EXHAUST GAS CLEANING SYSTEM FOR ENGINEERING VEHICLE

Abstract

An exhaust gas cleaning system is provided in an engineering vehicle such as a hydraulic excavator. During automatic regeneration, when a gate lock lever 5 is in a locked state and work is not performed, the exhaust gas temperature detected by the exhaust temperature detecting device 37 may be lower than the threshold value, so temperature-rising assistance is started as follows. The minimum engine output PS1 (pump discharge pressure P1 and pump discharge amount Q1) is brought to engine output PS2 (pump discharge pressure P2 and pump discharge amount Q2). In this way, a hydraulic load is applied to an engine to thereby increase exhaust gas temperature. When the work is resumed during the regeneration, an operator pulls down the gate lock lever to the first position A, and the engine output is returned to PS1. Thus, the temperature-rising assistance is stopped, however the automatic regeneration is continued.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to exhaust gas cleaning systems for engineering vehicles. In particular, the invention relates to an exhaust gas cleaning system for an engineering vehicle, which allows a filter to capture particulate matter contained in exhaust gas to clean the exhaust gas and that burns and removes the particulate matter captured by the filter for cleaning the filter.

2. Description of the Related Art

An engineering vehicle such as hydraulic excavator or the like has a diesel engine as its drive source mounted thereon. Regulations on the discharge amount of particulate matter (hereinafter, called PM) discharged from the diesel engine have yearly been tightened along with that of NOx, CO, HC, etc. To keep up with such regulations, an exhaust gas cleaning system has been known that allows a filter called a diesel particulate filter (DPF) to capture PM to reduce the amount of the PM to be discharged to the outside. As the amount of PM captured by the filter progressively increases during the use of such a discharge gas cleaning system, the filter will be increasingly clogged. This increases the exhaust pressure of the engine to induce degradation in fuel consumption. The PM captured by the filter is appropriately burned to remove the clogging of the filter, thereby regenerating the filter.

The filter is normally regenerated by use of an oxidation catalyst. The oxidation catalyst is disposed on the upstream side of the filter or directly carried on the filter. Alternatively, the oxidation catalyst is disposed on the upstream side of the filter and is directly carried on the filter. In any of such cases, to activate the oxidation catalyst, the temperature of the exhaust gas has to be higher than the activating temperature of the oxidation catalyst. For this reason, there is a technology called forced regeneration in which the exhaust gas temperature is increased to a set temperature (a threshold value) that is higher than the activating temperature of the oxidation catalyst and is suitable for regeneration. The forced regeneration includes a technique for increasing the temperature of exhaust gas by performing sub-injection (after-injection) in which fuel is injected in an expansion stroke after direct main injection into an engine, and a technique for increasing the temperature of exhaust gas by allowing a regeneration fuel injector installed in an exhaust pipe to inject fuel into the exhaust gas flowing in the exhaust pipe.

The forced regeneration of the filter includes manual regeneration in which the regeneration is started by the operator's input and automatic regeneration in which the regeneration is automatically started. The manual regeneration is performed as below. An amount of PM deposited on a filter (a deposition amount) is first estimated. When the PM deposition amount reaches a PM deposition limit amount, a warning is given to an operator to perform the manual regeneration. Then, the operator operates a manual regeneration switch, and the regeneration is started. WO 2009/60719 discloses a technology relating to manual regeneration. On the other hand, when the PM deposition amount reaches an accumulation limit value or when a predetermined time elapses, the automatic regeneration is performed. JP-2009-79500-A discloses a technology relating to automatic regeneration. The manual regeneration and automatic regeneration are such that the PM deposition amount is generally obtained by detecting an anteroposterior differential pressure on a filter and carrying out an operation based on the detected value of such differential pressure.

Incidentally, there is a close relationship between engine output and exhaust gas temperature. For example, if the engine output lowers, the exhaust gas temperature lowers. When the exhaust gas temperature per se is low, even if forced regeneration is performed, satisfactory regeneration is not likely to be performed because of insufficiently increased temperature. To address such a problem, JP-7-166840-A proposes an exhaust gas cleaning system attached with temperature-rising assistance means.

This exhaust gas cleaning system includes a device for detecting the neutral position of a control lever. When such a neutral detecting device detects the neutral position, the exhaust gas cleaning system starts temperature-rising assistance. When the neutral detecting device detects an operation position switched from the neutral position, the exhaust gas cleaning system stops the temperature-rising assistance position. The temperature-rising assistance means adjusts the discharge pressure and discharge amount of a hydraulic pump to increase pump output and increases engine output, thereby increasing exhaust gas temperature.

SUMMARY OF THE INVENTION

As described above, the exhaust gas cleaning system in the related art starts the temperature-rising assistance on the basis of the neutral position of the control lever. Therefore, there is a problem (first) as below.

For example, when a hydraulic excavator allows a front work device to work via a control lever, its engine output is increased and also exhaust gas temperature is increased accordingly. On the other hand, when the control lever is made neutral, the engine output immediately lowers while the exhaust gas temperature does not lower immediately. The exhaust gas temperature gradually lowers. When the control lever is operated again to resume the work, the engine output is increased and also the exhaust gas temperature is again increased. In other words, whenever the control lever is temporarily made neutral during the work, the temperature-rising assistance is not necessarily always performed.

If the temperature-rising assistance is done unnecessarily, it is likely to cause melting of the filter due to the abnormal increase in the exhaust gas temperature. Further, the unnecessary temperature-rising assistance is not preferable in view of energy saving.

The exhaust gas cleaning system in the related art stops the temperature-rising assistance on the basis of the operating position of the control lever. Therefore, there is a problem (second) as below.

When the control lever is made neutral during the normal time, the engine becomes idle. Therefore, the engine output is brought to engine output PSmin (pump discharge pressure P1 and pump discharge amount Q1). When the control lever is made neutral during regeneration, to perform the temperature-rising assistance the engine output is brought to engine output PSmax (pump discharge pressure P2 (>P1) and pump discharge amount Q2 (>Q1)). Then, when the control lever is switched from the neutral position to the operating position, the engine output is regulated to the pump discharge pressure P1 and the pump discharge amount Q1, i.e., to the engine output PSmin. In this way, the temperature-rising assistance is stopped.

In this case, the discharge pressure of the pump is regulated by the switching control of a pressure control valve. In addition, the discharge amount of the pump is regulated by the tilting control of a regulator. A response time until the pressure control valve and the regulator are operated after a control command was received occurs. Specifically, the control command may be issued so that the pump discharge pressure P2 becomes the pump discharge pressure P1 and the pump discharge amount Q2 becomes the pump discharge amount Q1. In such a case, they do not become P1 and Q1 immediately but the discharge pressure higher than P1 and the discharge amount greater than Q1 are kept for a given length of time.

In the state where the temperature-rising assistance is not completely stopped, if slight operation work is intended to be done via a control lever, a front work device is likely to be more driven than operator's intention. Thus, operability is impaired. Further, if the work is done by the front work device, an excessive load is suddenly applied to the engine to cause abrupt lowering in the rotation number of the engine (lag-down), which significantly impairs operability.

As described above, the exhaust gas cleaning system in the related art has the problem (1) relating to the unnecessary temperature-rising assistance and the problem (2) relating to the deterioration in operability in resuming work.

It is an object of the present invention to provide an exhaust gas cleaning system that can avoid unnecessary temperature-rising assistance and can prevent deterioration in operability in resuming work.

(1) According to the present invention, there is provided an exhaust gas cleaning system for an engineering vehicle including a diesel engine, a driven body driven by power of the engine, operating means for commanding the driven body to operate, and operation stopping means for stopping the operation of the driven body. The system includes: a filter device disposed in an exhaust system of the engine and including a filter for capturing particulate matter contained in exhaust gas; a regeneration device adapted to increase temperature of the exhaust gas to burn and remove particulate matter deposited on the filter; a regeneration control device adapted to control the start and stop of operation of the regeneration device; and temperature-rising assistance means for assisting temperature-rising of the regeneration device. The regeneration control device starts the operation of the temperature-rising assistance means when the operation stopping means is operated to stop the operation of the driven body during the operation of the generation device.

When the operation stopping means is operated so as to stop the operation of the driven body, a period of time during which engine output lowers is long. If the engine output lowers so that also the exhaust gas temperature gradually lowers, there is a high possibility that the exhaust gas becomes lower than a threshold value (a set temperature suitable for regeneration). In other words, unnecessary temperature-rising assistance can be avoided by starting the temperature-rising assistance only as necessary.

(2) Preferably, the exhaust gas cleaning system further includes an exhaust temperature detecting device adapted to detect temperature of the exhaust gas. The regeneration control device starts the operation of the temperature-rising assistance means when the operation stopping means is operated to stop the operation of the driven body and the exhaust temperature detecting device detects temperature lower than a threshold value during the operation of the regeneration device.

In this way, the temperature-rising assistance is started only when the exhaust gas temperature is lower than the threshold value. Therefore, the unnecessary temperature-rising assistance can further be avoided.

(3) Preferably, the regeneration control device stops the operation of the temperature-rising assistance means when the operation stopping means is operated to release the stop of the operation of the driven body.

A certain amount of time occurs until the operating means is operated to drive the driven body to resume the work after the operation stopping means was operated to release the stop of the operation of the driven body to enable the operation thereof. Such an amount of time is longer than a response time until the operation of the assistance means is stopped after the command of stopping the temperature-rising assistance was issued. At the time of resuming the work, the operation of the assistance means is surely stopped. In this way, deterioration in operability in resuming the work can be prevented.

(4) Preferably, the engineering vehicle includes a hydraulic pump driven by the engine, and the temperature-rising means regulates at least one of the discharge pressure and discharge amount of the hydraulic pump and applies a hydraulic load to the engine.

(5) Preferably, the engineering vehicle includes an engine control device adapted to control the engine, and the temperature-rising assistance means commands the engine control device to bring the rotation number of the engine to a predetermined rotation number higher than an idle rotation number.

With the constitution just above, the engine output increases and the temperature-rising assistance means can assist the temperature-rising of exhaust gas during the regeneration.

(6) Preferably, the operation stopping means is a gate lock lever selectively operated between a first position where the operation of the driven body is enabled and a second position where the operation of the driven body is disabled.

(7) Preferably, the operation stopping means is a parking brake operated to brake travel motion during parking of the engineering vehicle.

(8) Preferably, the operation stopping means is a shift lever switched among a forward movement position, a neutral position and a rearward movement position.

The operation of the driven body (e.g. a front work device or a traveling system) can be stopped by operating the operation stopping means such as the gate lock lever, the parking lever, the shift lever, etc.

The present invention can avoid the unnecessary temperature-rising assistance and prevent the degradation in operability in resuming the work.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the entire constitution of an exhaust gas cleaning system (a first embodiment).

FIG. 2 illustrates a hydraulic drive system mounted on a hydraulic excavator.

FIG. 3 illustrates external appearance of the hydraulic excavator.

FIG. 4 illustrates a functional block diagram of a controller.

FIG. 5 is a flowchart illustrating processing contents of temperature-rising assistance control.

FIG. 6 illustrates the relationship between the discharge pressure and discharge amount of a hydraulic pump and the output power of an engine.

FIG. 7 illustrates exhaust gas temperature with time by way of example.

FIG. 8 illustrates the entire constitution of the exhaust gas cleaning system (a modified example).

FIG. 9 illustrates external appearance of a wheel loader (third example).

FIG. 10 illustrates a functional block diagram of a controller.

FIG. 11 is a flowchart illustrating processing contents of temperature-rising assistance control.

FIG. 12 is a flowchart illustrating processing contents of temperature-rising assistance control.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Constitution

A first embodiment of the present invention will hereinafter be described with reference to the drawings.

FIG. 1 illustrates the entire constitution of an exhaust gas cleaning system for an engineering vehicle according to the first embodiment of the invention. Referring to FIG. 1, a diesel engine 1 is mounted on the engineering vehicle (e.g. a hydraulic excavator). The engine 1 is provided with an electronic governor 1a which is an electronic fuel injection control unit. The target rotation number of the engine 1 is commanded with an engine control dial 2 and the actual rotation number of the engine 1 is detected by a rotation number detecting device 3. The instruction signal of the engine control dial 2 and the detected signal of the rotation number detecting device 3 are received by a controller 4. The controller 4 controls the electronic governor 1a on the basis of the command signal (the target rotation number) and the detected signal (the actual rotation number), thereby controlling the rotation number and torque of the engine 1.

The hydraulic excavator is provided with a gate lock lever 5 on the left front side of a cab seat 108. The gate lock lever 5 can be selectively operated between a first position A which is a lowered position to limit an entrance to the cab seat 108 and a second position B which is a raised position to open the entrance to the cab seat 108.

The exhaust gas cleaning system is disposed on an exhaust pipe 31 constituting part of an exhaust system of the engine 1. The exhaust gas cleaning system includes: a DPF device 34 including a filter 32 collecting particulate matter contained in exhaust gas and oxidation catalyst 33 disposed on the upstream side of the filter 32; a position detecting device 35 detecting the operating position of the gate lock lever 5; and a differential pressure detecting device 36 detecting anteroposterior differential pressure (a pressure loss of the filter 32) between the upstream side and downstream side of the filter 32. The cleaning system further includes an exhaust temperature detecting device 37 installed on the upstream side of the filter to detect the temperature of exhaust gas; a regeneration switch 38 instructing manual regeneration; and a regeneration fuel injection device 39 installed on the exhaust pipe 31 between the engine 1 and the DPF device 34. The oxidation catalyst 33 and the regeneration fuel injection device 39 constitute a regeneration unit which burns and removes the PM (particulate matter) deposited on the filter 32 for regenerating the filter 32.

FIG. 2 illustrates the hydraulic drive system mounted on the engineering vehicle (e.g. a hydraulic excavator). The hydraulic drive system includes: a variable displacement main hydraulic pump 11 and a fixed displacement pilot pump 12 which are driven by the engine 1; a plurality of actuators including a hydraulic motor 13 and hydraulic cylinders 14 and 15, the motor 13 and the cylinders 14 and 15 being driven by the hydraulic fluid discharged from the hydraulic pump 11; and a plurality of flow control valves including pilot-operated flow control valves 17 to 19 which control the flow (a flow rate and a direction) of the hydraulic fluid supplied from the hydraulic pump 11 to the hydraulic motor 13 and hydraulic cylinders 14 and 15. The hydraulic drive system further includes a pilot relief valve 21 which regulates the pressure of the hydraulic fluid discharged from the pilot pump 12 and forms a pilot hydraulic source 20; a main relief valve 22 which sets the upper limit of the discharge pressure of the main hydraulic pump 11; a control valve 30 installed on the downstream side of a center bypass line connecting the flow control valves 17 to 19 in series. The hydraulic drive system further includes a solenoid selector valve 23 connected to the downstream side of the pilot hydraulic source 20 and on/off controlled depending on the opening/closing state of the gate lock lever 5 installed at the cab seat entrance of the hydraulic excavator; and remote control valves 25, 26 and 27. The remote control valves are connected to a pilot fluid passage 24 on the downstream side of the solenoid selector valve 23 and produces control pilot pressures a, b; c, d; e and f, respectively, adapted to operate the flow control valves 17 to 19 using the hydraulic pressure of the pilot hydraulic source 20 as original pressure.

The remote control valves 25, 26 and 27 are operated by the corresponding left and right control levers 28 and 29 installed on the left and right of the cab seat 108. The control levers 28 and 29 can each be operated in a cross shape direction. When the control lever 28 is operated in a one direction of the cross shape, the remote valve 25 is operated. When the control lever 28 is operated in the other direction of the cross shape, the remote control valve 27 is operated. When the control lever 29 is operated in a one direction of the cross shape, the remote control valve 26 is operated. When the control lever 29 is operated in the other direction of the cross shape, a remote control valve not illustrated is operated. In the case where the control lever 28 is operated in the one direction of the cross shape, when it is operated from the neutral direction in the one direction, the remote control valve produces control pilot pressure “a” and when the control lever 28 is operated from a neutral position in the opposite direction, the remote control valve 25 produces control pilot pressure “b”. The control pilot pressures “a” and “b” are led via pilot lines 25a and 25b to the corresponding pressure-receiving portions of the flow control valve 17, whereby the flow control valve 17 is switched from the neutral position.

Similarly, in the case where the control lever 28 is operated in the other direction of the cross shape, when it is operated in the one direction from the neutral position, the remote control valve 27 produces control pilot pressure “e”, and when the control lever 28 is operated in the opposite direction from the neutral direction, the remote control valve 27 produces control pilot pressure “f”. The control pilot pressures “e” and “f” are led via pilot lines 27a and 27b to the corresponding pressure-receiving portions of the flow control valve 19, whereby the flow control valve 19 is switched from the neutral position. In the case where the control lever 29 is operated in the one direction of the cross shape, when it is operated from the neutral position in the one direction, control pilot pressure “c” is produced, and when the flow control lever is operated from the neutral direction in the opposite direction, control pilot pressure “d” is produced. The control pilot pressures “c” and “d” are led via pilot control lines 26a and 26b, respectively, to the respective pressure-receiving portions of the flow control valve 18, whereby the flow control valve 18 is switched from the neutral position.

The control pilot pressures a to f are subjected to communication or shutoff depending on the position of the gate lock lever 5.

When the gate lock lever 5 is at the first position A, the solenoid of the solenoid selector valve 23 is energized to switch the solenoid control valve 23 from the position illustrated in the figure. In this way, the pressure of the pilot hydraulic source 20 is led to the remote control valves 25, 26 and 27, which makes it possible to allow the remote control valves 25, 26 and 27 to operate the corresponding flow control valves 17, 18 and 19. When the gate lock lever 5 is operatively raised to the second position B, the solenoid of the solenoid selector valve 23 is de-energized to switch the position illustrated in the figure, thereby blocking the communication between the pilot hydraulic source 20 and the remote control valves 25, 26 and 27. This makes it impossible for the remote control valves 25, 26 and 27 to operate the corresponding flow control valves 17, 18 and 19. In short, when the gate lock lever 5 is operatively raised to the second position B, the remote control valves 25, 26 and 27 (control lever units) are brought into a locked state. When the gate lock lever 5 is operatively lowered to the first position A again, the remote control levers 25, 26 and 27 are brought into an unlocked state. The switching of the position of the solenoid valve 23 by the gate lock lever 5 is done as below. For example, a switch not illustrated in the figure is installed between the solenoid of the solenoid selector valve 23 and the power supply. When the gate lock lever 5 is at the first position A, such a switch is turned on (closed) to energize the solenoid. When the gate lock lever 5 is operated to be at the second position B, the switch is turned off (opened) to de-energize the solenoid.

The control valve 30 is a two-position selector valve having an open position and a close position. When the solenoid is not energized, the control valve 30 is at the open position. When the solenoid is energized, the control vale 30 is switched from the open position illustrated from the close position.

FIG. 3 illustrates external appearance of the hydraulic excavator. The hydraulic excavator includes a lower travel structure 100, an upper turning body 101, and a front work device 102. The lower travel structure 100 has left and right crawler type travelling devices 103a and 103b which are driven by left and right travelling devices 104a and 104b, respectively. The upper turning body 101 is mounted on the lower travel structure 100 so as to be turnable by a turning motor 105. The front work device 102 is mounted onto the front portion of the upper turning body 101 so as to be able to be laid and raised. The upper turning body 101 is provided with an engine room 106 and a cabin 107. An engine 1 is disposed in the engine room 106. The gate lock lever 5 (FIG. 1) is installed at the entrance to the cab seat 108 in the cabin 107. The control lever units (not illustrated) incorporating the corresponding remote control levers 25, 26 and 27 are disposed on the left and right of the cab seat 108.

The front work device 102 is of an articulated structure having a boom 111, an arm 112 and a bucket 113. The boom 111 is turned vertically by the extension and contraction of a boom cylinder 114. The arm 112 is turned upward and downward, and forward and rearward by the extension and contraction of an arm cylinder 115. The bucket 113 is turned upward and downward, and forward and rearward by the extension and contraction of a bucket cylinder 116.

In FIG. 2, the hydraulic motor 13 corresponds to e.g. the turning motor 105. The hydraulic cylinder 14 corresponds to e.g. the arm cylinder 115. The hydraulic cylinder 15 corresponds to e.g. the boom cylinder 114. The hydraulic drive device illustrated in FIG. 2 is provided with other hydraulic actuators and control valves corresponding to the traveling motors 104a, 104b and the bucket cylinder 116, etc. However, their illustrations are omitted.

Control

FIG. 4 illustrates a functional block of the controller 4. The controller 4 includes a main controller 41 and an engine controller 43, which are connected with each other via a communication line 44 to form a vehicle-body network. The main controller 41 is adapted to receive the command signal of the engine control dial 2, the detection signals of a position detecting device 35, of a differential pressure detecting device 36 and of an exhaust temperature detecting device 37. The engine controller 43 is adapted to receive the detection signal of a rotation number detecting device 3.

The engine controller 43 receives the command signal of the engine control dial 2 via the communication line 44 and controls the rotation number and torque of the engine 1 on the basis of the command signal and the detected signal of the rotation number detecting device 3.

The main controller 41 controls the vehicle body in general such as the hydraulic drive device, etc. For example, the main controller 41 controls the discharge pressure and discharge amount of the hydraulic pump 11 by controlling the control valve 30 and the regulator of the hydraulic pump 11. Regeneration control and temperature-rising assistance control are each one function of the main controller 41.

The main controller 41 receives the detected signal of the differential pressure detecting device 36, estimates a PM deposition amount, and executes arithmetic processing on regeneration control on the basis of the estimated PM deposition amount. The main controller 41 then sends a control signal corresponding to the calculation result to the engine controller 43 via the communication line 44. In response to the control signal, the engine controller 43 controls the electronic governor 1a and the regeneration fuel injection device 39 (automatic regeneration control). The main controller 41 receives an instruction signal of the regeneration switch 38 and executes the arithmetic processing on the regeneration control (manual regeneration control).

A description is given of the temperature-rising assistance control by the main controller 41. The main controller 41 receives the detected signals of the position detecting device 35 and of the exhaust temperature detecting device 37 and executes arithmetic processing on the temperature-rising assistance control on the basis of the detected signals. The main controller 41 sends the control signals corresponding to the calculation results to the control valve 30 and the regulator of the hydraulic pump 11 to control the discharge pressure and discharge amount of the hydraulic pump 11. In this way, the load on the engine 1 driving the hydraulic pump 11 is increased to increase the exhaust gas temperature of the engine 1.

FIG. 5 is a flowchart illustrating the processing contents of the temperature-rising assistance control by the main controller 41.

The main controller 41 first determines whether or not the main controller 41 per se is executing the regeneration control (step S10). When determining that the regeneration control is being done, the main controller 41 determines whether or not the gate lock lever 5 is operatively raised to the second position B on the basis of the detected signal of the position detecting device 35. In other words, the main controller 41 determines whether or not the gate lock lever 5 is in the locked state where the control pilot pressure is blocked (step S20). When determining that the gate lock lever 5 is in the locked state, the main controller 41 determines whether or not the exhaust gas temperature is lower than a threshold value (a set value suitable for regeneration) on the basis of the detected signal of the exhaust temperature detecting device 37 (step S30). When determining that the exhaust gas temperature is lower than the threshold value, the main controller 41 controls the discharge pressure and discharge amount of the hydraulic pump 11 and applies a hydraulic load to the engine 1, thus starting the temperature-rising assistance (step S40).

In step S10, the main controller 41 may determine that it does not exercise the regeneration control. In step S20, the gate lock lever 5 may not be in the locked state (is at the first position A). In step S30, the exhaust gas temperature may not be lower than the threshold value (the temperature suitable for the regeneration). In any of such cases, the processing is returned to the procedure immediately after the start and the procedures of steps S10, S20 and S30 are repeated.

The start of temperature-rising assistance in step S40 is performed as below for example. FIG. 6 illustrates the relationship between the discharge pressure and discharge amount of the hydraulic pump 11 and the output power of the engine 1. When, during normal times, the gate lock lever 5 is in the locked state and work is not done, the discharge pressure and discharge amount of the hydraulic pump 11 are controlled to pump discharge pressure P1 and pump discharge amount Q1, respectively, in view of energy saving to provide minimum engine output PS1. When the temperature-rising assistance command is issued, the discharge pressure and discharge amount of the hydraulic pump 11 are controlled to pump discharge pressure P2 (>P1) and pump discharge amount Q2 (>Q1), respectively. The engine 1 is allowed to have engine output PS2 for driving the hydraulic pump 11, that is, the load on the engine 1 is increased, thereby increasing the exhaust gas temperature of the engine 1.

After the start of temperature-rising assistance, determination is made as to whether or not at least one of the determination in step 10 (condition 1), the determination in step 20 (condition 2) and the determination in step 30 is negative (at least one of the conditions 1 to 3 is not satisfied) (step 50). When it is determined that any one is negative, the temperature-rising assistance is stopped (step S60).

The stop of the temperature-rising assistance in step S60 is carried out by controlling the pump discharge pressure and pump flow rate to the pump discharge pressure P1 and pump discharge amount Q1, respectively, to provide the minimum engine output PS1. The load on the engine 1 is reduced to lower the exhaust gas temperature of the engine 1.

When it is determined that all of conditions 1 to 3 is affirmative (all of the conditions 1 to 3 is satisfied. In other word, none of the conditions 1 to 3 is negative.) in step S50, the procedure of step 50 is repeated to continue the temperature-rising assistance.

Operation

A description is given of the operation of the exhaust gas cleaning system according to the first embodiment. FIG. 7 illustrates an example in exhaust gas temperature with time for assisting understanding.

When the engineering vehicle (the hydraulic excavator) finishes work, an operator operatively raises the gate lock lever 5 from the first position A to the second position B to bring it into the locked state. In this case, when the PM deposition amount reaches an accumulation limit value, automatic regeneration is started. There is also a case where, since the automatic regeneration is started during work, an operator interrupts the work and brings the gate lock lever 5 into the locked state.

In general, exhaust gas temperature immediately after work or during work is higher than the activating temperature of the oxidation catalyst 33. When the regeneration fuel injection device 39 is controlled to inject fuel into the exhaust pipe 31, unburned fuel is supplied to and oxidized by the oxidation catalyst 33 to provide reaction heat. Such reaction heat further increases the exhaust gas temperature to burn and remove the PM deposited on the filter 32.

In this case, the exhaust gas temperature detected by the exhaust temperature detecting device 37 is equal to or higher than a threshold value. Therefore, the temperature-rising assistance is not performed (step S10→S20→S30→S10) (the state 1 in FIG. 7).

The gate lock lever 5 is usually in the locked state. When work is not performed, the discharge pressure and discharge amount of the hydraulic pump are controlled to the pump discharge pressure P1 and the pump discharge amount Q1, respectively, in view of energy saving to provide the minimum engine output PS1. If the engine output is lowered, also the exhaust gas temperature lowers gradually and becomes lower than the threshold value. In this case, even if the forced regeneration is performed, there is a possibility that the exhaust gas temperature may not sufficiently be increased (state 2 in FIG. 7).

Therefore, when the exhaust gas temperature detected by the exhaust gas temperature device 37 is lower than the threshold value, the temperature-rising assistance is started (step S10→S20→S30→S40). The discharge pressure and discharge amount of the hydraulic pump are controlled to the pump discharge pressure P2 and the pump discharge amount Q2, respectively, to provide engine output PS2, which increases exhaust gas temperature (state 3 in FIG. 7).

After the start of the temperature-rinsing assistance, when the exhaust gas temperature is equal to or higher than the threshold value by the temperature-rising assistance or when the automatic regeneration is finished by burning and removing the PM, the temperature-rising assistance is stopped (Step S40→S50→S60).

On the other hand, in a case where work is resumed during the regeneration, when the operator operatively pulls down the gate lock lover 5 to the first position A, the temperature-rising assistance is stopped (Step S40→S50→S60) (state 4 in FIG. 7).

Incidentally, even if the temperature-rising assistance is stopped by operatively pulling down the gate lock lever 5, automatic regeneration is continued. If the operator operatively pulls down the gate lock lever 5 to the first position A and resumes the work, the engine output is increased so that the exhaust gas temperature is equal to or higher than the threshold value. Thus, satisfactory regeneration is performed (state 5 in FIG. 7).

Advantages

A description is given of the effects of the exhaust gas cleaning system according to the first embodiment.

(a) The exhaust gas cleaning system in the related art starts the temperature-rising assistance on the basis of the neutral position of each of the control levers 28 and 29. When the control levers 28 and 29 are made neutral, the engine output is lowered. However, if the control levers 28 and 29 are operated again to resume the work, the engine work is increased again so that it is not likely that the exhaust gas temperature becomes lower than the threshold value. In other words, if the period of time during which the engine output is lowered is short, it is not necessary to perform the temperature-rising assistance. On the other hand, if the temperature-rising assistance is performed needlessly, there is a possibility that the filter is damaged by melting due to abnormally increased temperature. In addition, such needless temperature-rising assistance is not preferable also in view of energy saving.

The exhaust gas cleaning system according to the present embodiment starts the temperature-rising assistance on the basis of the operating position (the second position B) of the gate lock lever 5. When operatively raising the gate lock lever 5 to the second position B, the operator often gets away from the hydraulic excavator for a rest. Therefore, the period of time during which the engine output is lowered is long. If the engine output is lowered, also the exhaust gas temperature gradually lowers and is more likely to become lower than the threshold value. In short, the exhaust gas cleaning system according to the present embodiment starts the temperature-rising assistance only when required. Thus, the unnecessary temperature-rising assistance can be avoided.

(b) If the engine output is lowered, the exhaust gas temperature gradually lowers; however, it will not lower immediately. If the exhaust gas temperature is equal to or higher than the threshold value, the temperature-rising assistance is not necessary. The exhaust gas cleaning system according to the present embodiment is provided with the exhaust temperature detecting device 37. When the exhaust gas temperature detected by the exhaust temperature detecting device 37 is equal to or higher than the threshold value, the temperature-rising assistance is not performed. Thus, the unnecessary temperature-rising assistance can further be avoided.

(c) The exhaust gas cleaning system in the related art has the following same operation with the exhaust gas cleaning system according to the present embodiment. Both the systems control the discharge pressure and discharge amount of the hydraulic pump 11 and increase the engine output PS1 (the pump discharge pressure P1 and the pump discharge amount Q1) to the engine output PS2 (the pump discharge pressure P2 and the pump discharge amount Q2). In this way, the systems start the temperature-rising assistance and return the engine output PS2 to the engine output PS1 (the pump discharge pressure P1 and the pump discharge amount Q1) and stop the temperature-rising assistance.

In this case, the discharge pressure of the pump 11 is regulated by the switching control of the control valve 30. In addition, the discharge amount of the pump 11 is regulated by the tilting control of the regulator. Response time occurs until the control valve 30 and the regulator of the pump 11 are operated after a control command was inputted. In other words, even if the control order is issued so that P2 and Q2 become P1 and Q1, respectively, P2 and Q2 do not immediately become P1 and Q1, respectively. Therefore, discharge pressure higher than P1 and a discharge amount greater than Q1 are kept for a given length of time.

The exhaust gas cleaning system in the related art commands the stop of the temperature-rising assistance on the basis of the operating positions of the control levers 28 and 29. There is no time until the work is resumed by the control levers 28 and 29 after the temperature-rising assistance was stopped by the control levers 28 and 29. Therefore, if the work is resumed in this state, operability is likely to deteriorate.

The exhaust gas cleaning system in the present embodiment commands the stop of the temperature-rising assistance on the basis of the operating position (the first position A) of the gate lock lever 5. An interval of time from the command of stopping the temperature-rising assistance to the resuming of the work by the operative levers 28 and 29, i.e., an interval of time until the operator operates the control levers 28 and 29 after the operator operatively pulls down the gate lock lever 5 to enable the operation of the hydraulic excavator, is longer than the response time of the control valve 30 and of the regulator of the pump 11. Therefore, the engine output is returned to the engine output PS1 (the pump discharge pressure P1, pump discharge amount Q1) at the time of resuming the work. Thus, it is possible to prevent operability from deteriorating at the time of resuming the work.

Modified Example

The embodiment of the present invention has been described thus far. However, the present invention is not limited to this. The invention can be modified in various ways within the scope of the spirit thereof. The following recites such modified examples.

1. In the operation of the present embodiment, the description is given on the premise of the automatic regeneration control. However, the temperature-rising assistance may be done during manual regeneration control. The manual regeneration control is started based on the command of a regeneration switch 38.

2. In the operation of the present embodiment, the automatic regeneration is stated when the PM deposition amount estimated by the differential pressure detecting device 36 reaches the accumulation limit value and is ended when the PM is burned and removed so that the estimated PM deposition amount becomes equal to or less than the accumulation permissible value. However, the automatic regeneration may be started after a predetermined time elapses and may be ended after a predetermined time elapses.

3. In the operation of the present embodiment, the PM deposition amount is obtained by detecting the anteroposterior differential pressure on the filter by the differential pressure detecting device 36 and by performing a calculation based on the detected value of the differential pressure. However, the PM deposition amount may be obtained as below. The engine 1 is provided with an air-quantity detecting device 51 which detects a quantity of air flowing into the engine and with a boost pressure detecting device 52 which detects the pressure of air flowing into the engine. The quantity and pressure of the air flowing into the engine are detected by such devices and a calculation is performed based on the detected values. FIG. 8 illustrates the entire constitution of the exhaust gas cleaning system for an engineering vehicle according to this modified example.

4. In the operation of the present embodiment, as illustrated in the functional block diagram (FIG. 4) of the controller 4, the control valve 30 and the regulator of the hydraulic pump 11 directly receive the command signals outputted from the controller 4 and are controlled based on the command signals. However, another constitution as below may be possible. Solenoid valves are installed. The controller 4 sends command signals to these solenoid valves. The solenoid valves are each switched based on the command signals and produce control pilot pressure taking the hydraulic pressure of the pilot hydraulic source 20 as source pressure. The control valve 30 and the regulator of the hydraulic pump 11 are each controlled based this control pilot pressure.

Second Embodiment

In the first embodiment, the control valve 30, the regulator of the pump 11 and one function of the main controller 41 controlling these constitute the temperature-rising assistance means as below. The discharge pressure and discharge amount of the hydraulic pump 11 are adjusted and the hydraulic load is applied to the engine 1 to assist temperature-rising during regeneration. However, the temperature-rising assistance means is not limited to this.

The constitution of a second embodiment is the same as that of the first embodiment; therefore, its illustration is omitted. The second embodiment is different from the first embodiment in the details of the start (S40) and stop (S60) of the temperature-rising assistance in the temperature-rising assistance control (see FIG. 5) of the main controller 41.

The start of the temperature-rising assistance in step S40 is done as below for example.

During the normal time, the gate lock lever 5 is in the locked state. When work is not done, the engine controller 43 controls the rotation number of the engine 1 to the idle rotation number N0 (low rotation number) in view of energy saving (automatic idle control). During regeneration, when exhaust gas temperature is insufficient, temperature-rising assistance is performed.

The main controller 41 switches the target rotation number of the engine 1 from the target rotation number (the idle rotation number N0) directed by the engine control dial 2 to a predetermined rotation number N1. In addition, the main controller 41 sends the target rotation number (the rotation number N1) to the engine controller 43 via the communication line 44. The engine controller 43 exercises feedback control on a fuel injection amount of the electronic governor 1a on the basis of the target rotation number (the rotation number N1) and the actual rotation number of the engine 1 detected by the rotation number detecting device 3 so that the rotation number of the engine 1 may become the first rotation number N1. The rotation number N1 is one suitable for the regeneration control that can raise the temperature of the exhaust gas at that time to temperature higher than the activating temperature of the oxidation catalyst 33. For example, the rotation number N1 is a middle-speed rotation number, e.g., approximately 1800 rpm.

The stop of the temperature-rising assistance in step S60 is done by controlling the rotation number of the engine 1 to the idle rotation number N0 (the low-speed rotation number). The load on the engine 1 is reduced to lower the exhaust gas temperature of the engine 1.

Also the present embodiment configured as described above can produce the effects (a), (b) and (c) of the first embodiment.

Third Embodiment

In the first embodiment, the engineering vehicle is the hydraulic excavator. The gate lock lever 5 constitutes operation stopping means for disabling the operation of the front work device 102 of the hydraulic excavator to stop the operation. However, the operation stopping means for the engineering vehicle is not limited to this.

A third embodiment is described with reference to FIGS. 9 to 12. The present embodiment is such that the present invention is applied to a wheel loader.

FIG. 9 illustrates the external appearance of the wheel loader which is an engineering vehicle according to the present embodiment. In FIG. 9, the wheel loader 200 includes a vehicle-body front portion 201 and a vehicle-body rear portion 202 which are turnably pin-joined to each other and which constitute a vehicle body. A front work device 204 is installed on the vehicle-body front portion 201. A cab seat 206 is installed on the vehicle-body rear portion 202. The cab seat 206 is provided with operation means such as a control lever device 207, a steering wheel 208 and the like. The vehicle-body front portion 201 and the vehicle-body rear portion 202 are provided with front wheels 235 and rear wheels 236, respectively. In addition, an engine 1, a hydraulic pump 11, a controller 4 and other devices are mounted on the vehicle-body rear portion 202. The front wheels 235 and the rear wheels 236 are connected to an output shaft of the engine 1 via a torque converter and a transmission not illustrated to constitute a traveling system (not illustrated). When the operator depresses an accelerator pedal 61 (described later), the rotation number and torque of the engine 1 are increased. Such power is transmitted to the front wheels 235 and rear wheels 236 via the torque converter and the transmission to provide travel motion. A steering cylinder 203 is installed between the vehicle-body front portion 201 and the vehicle-body rear portion 202. The steering wheel 208 is operated to actuate the steering cylinder 203 to change the direction of the vehicle-body front portion 201 (the traveling direction of the vehicle body) with respect to the vehicle-body rear portion 202.

The wheel loader further includes operating means such as an accelerator pedal 61 which outputs command signals for controlling the rotation number and torque of the engine 1 and traveling speed; parking braking means such as a parking brake 62; and a shift lever 63 selectively switched among a forward movement position F, a neutral position N and a rearward movement position R.

FIG. 10 illustrates a functional block of a controller 4.

A command signal of the accelerator pedal 61 is received by a main controller 41 of the controller 4. The main controller 41 calculates the target rotation number of the engine 1 on the basis of the command signal. The main controller 41 sends a control signal corresponding to the calculation result to an engine controller 43 via a communication line 44. The engine controller 43 controls an electronic governor 1a on the basis of the target rotation number and the detected signal (the actual rotation number) of the rotation number detecting device 3 to control the rotation number and torque of the engine 1. The output shaft of the engine 1 is connected to a traveling system. The engine controller 43 controls the rotation number and torque of the engine 1 to control traveling speed.

In the present embodiment, for example, if temperature-rising assistance is started based on a non-operation state of the accelerator pedal 61, a problem associated with unnecessary temperature-rising assistance occurs. If the temperature-rising assistance is stopped based on the operation state of the accelerator pedal 61, a problem associated with deterioration in the operability in resuming traveling occurs.

The parking brake 62 is provided with a parking brake operating position detecting device 66 which detects the operating position thereof. A main controller 41 receives a detected signal of the parking brake operating position detection device 66. The main controller 41 exercises braking control on the wheel loader on the basis of its command signal. When being operated to be at the braking position, the parking brake 62 disables the traveling of the wheel loader to stop its operation.

The shift lever 63 is provided with a shift lever operating position detecting device 67 which detects the operating position thereof. Also the detected signal of the shift lever operating position detecting device 67 is received by the main controller 41. The main controller 41 exercises switching control on switching among forward movement, neutral and rearward movement on the basis of its command signal. When being operated to be at a neutral position N, the shift lever 63 disables the traveling of the wheel loader to stop its operation.

The parking brake 62 and the shift lever 63 each constitute operation stopping means.

FIG. 11 and FIG. 12 are flowchart illustrating processing contents of temperature-rising assistance control by the main controller 41 in the present embodiment. The flowchart of FIG. 11 is different from that of FIG. 5 in that a determination relating to the operating position of the parking brake 62 is made in the processing of step S20 and of step S50. The flowchart of FIG. 12 is different from that of FIG. 5 in that a determination relating to the operating position of the shift lever 63 is made in the processing of step S20 and of step S50.

Specifically, in FIG. 11, after it was determined to be under regeneration control in step S10, a determination is made as to whether or not the parking brake 62 is operated to be at the braking position on the basis of the detected signal of the parking brake operating position detecting means 66 (S20). When it is determined that the parking brake 62 is operated to be at the braking position and it is determined that the exhaust gas temperature is lower than a threshold value in step S30, the temperature-rising assistance is started in step S40.

After the temperature-rising assistance has been started, when at least one of condition 1, condition 2 (the parking bake 62 being at the braking position) and condition 3 is determined as negative, the temperature-rising assistance is stopped in step S60.

In FIG. 12, after it was determined to be under regeneration control in step S10, a determination is made as to whether or not the shift lever 63 is operated to be at the neutral position N on the basis of the detected signal of the shift lever operating position detecting device 67 (step S20). When it is determined that the shift lever 63 is operated to be at the neutral position N and that the exhaust gas temperature is lower than a threshold value in step S30, the temperature-rising assistance is started in step S40.

After the temperature-rising assistance has been started, when at least one of condition 1, condition 2 (the shift lever 63 being at the neutral position) and condition 3 is determined as negative, the temperature-rising assistance is stopped in step S60.

Also the embodiment configured as described above can produce the same effects as the effects (a), (b) and (c) of the first embodiment.

(a) The exhaust gas cleaning system according to the present embodiment starts the temperature-rising assistance on the basis of the braking position of the parking brake 62 or the neutral position N of the shift lever 63. When operating the parking brake 62 to be at the braking position or the shift lever 63 to be at the neutral position N, the operator intends to allow the wheel loader not to travel. In this case, the period of time during which the engine output lowers becomes long. When the engine output lowers, exhaust gas temperature gradually lowers and is likely to become lower the threshold value. That is to say, the exhaust gas cleaning system according to the present embodiment starts the temperature-rising assistance only when necessary. Thus, unnecessary temperature-rising assistance can be avoided.

(b) When engine output lowers, it is gradually that the exhaust gas temperature lowers; however, it is not immediately that the exhaust gas temperature lowers. When the exhaust gas temperature is equal to or higher than a threshold value, the temperature-rising assistance is not necessary. The exhaust gas cleaning system according to the embodiment is provided with the exhaust gas temperature detecting device 37. When the exhaust gas temperature detected by the exhaust temperature detecting device 37 is equal to or higher than the threshold value, the temperature-rising assistance is not done. This can further avoid unnecessary temperature-rising assistance.

(c) The exhaust gas purifying system according to the present embodiment commands the stop of the temperature-rising assistance on the basis of the braking-releasing position of the parking brake 62 or the forward movement position F or rearward movement position R of the shift lever 63. An interval of time until the resuming of the travel by the accelerator pedal 61 after the command of stopping the temperature-rising assistance by the parking brake 62 or by the shift lever 63, that is to say, an interval of time until the accelerator 61 is operated after the operator operates the parking brake 62 or the shift lever 63 to enable the wheel loader to be traveled, is longer than the response time of the control valve 30 or of the regulator of the pump 11. At the time of resuming the travel, the engine output is returned to the engine output PS1 (the pump discharge pressure P1 and the pump discharge amount Q1). Thus, the degradation in operability in resuming the traveling can be prevented.

Claims

1. An exhaust gas cleaning system for an engineering vehicle including a diesel engine, a driven body driven by power of the engine, operating means for commanding the driven body to operate, and operation stopping means for stopping the operation of the driven body, the system comprising:

a filter device disposed in an exhaust system of the engine and including a filter for capturing particulate matter contained in exhaust gas;

a regeneration device adapted to increase temperature of the exhaust gas to burn and remove particulate matter deposited on the filter;

a regeneration control device adapted to control the start and stop of operation of the regeneration device; and

temperature-rising assistance means for assisting temperature-rising of the regeneration device;

wherein the regeneration control device starts the operation of the temperature-rising assistance means when the operation stopping means is operated to stop the operation of the driven body during the operation of the regeneration device.

2. The exhaust gas cleaning system for an engineering vehicle according to claim 1, further comprising:

an exhaust temperature detecting device adapted to detect temperature of the exhaust gas;

wherein the regeneration control device starts the operation of the temperature-rising assistance means when the operation stopping means is operated to stop the operation of the driven body and the exhaust temperature detecting device detects temperature lower than a threshold value during the operation of the regeneration device.

3. The exhaust gas cleaning system for an engineering vehicle according to claim 1,

wherein the regeneration control device stops the operation of the temperature-rising assistance means when the operation stopping means is operated to release the stop of the operation of the driven body.

4. The exhaust gas cleaning system for an engineering vehicle according to claim 1,

wherein the engineering vehicle includes a hydraulic pump driven by the engine, and

the temperature-rising means regulates at least one of the discharge pressure and discharge amount of the hydraulic pump and applies a hydraulic load to the engine.

5. The exhaust gas cleaning system for an engineering vehicle according to claim 1,

wherein the engineering vehicle includes an engine control device adapted to control the engine, and

the temperature-rising assistance means commands the engine control device to bring the rotation number of the engine to a predetermined rotation number higher than an idle rotation number during the operation of the regeneration device.

6. The exhaust gas cleaning system for an engineering vehicle according to claim 1,

wherein the operation stopping means is a gate lock lever selectively operated between the first position where the operation of the driven body is enabled and the second position where the operation of the driven body is disabled.

7. The exhaust gas cleaning system for an engineering vehicle according to claim 1,

wherein the operation stopping means is a parking brake operated to brake travel motion during parking of the engineering vehicle.

8. The exhaust gas cleaning system for an engineering vehicle according to claim 1,

wherein the operation stopping means is a shift lever selectively switched among a forward movement position, a neutral position and a rearward movement position.