Method For Protecting An Engine During A Parked Regeneration Of A Particulate Filter

Abstract

An automatic shutdown system is provided in which a work vehicle is shutdown upon an occurrence of a critical fault; i.e., an occurrence of a condition which could diminish the life or cause a complete failure of at least a portion of the work vehicle.

Description

FIELD OF THE INVENTION

This invention relates to emission control systems in motor vehicles powered by internal combustion engines and, more particularly, vehicles powered by diesel engines with exhaust gas treatment devices requiring regeneration.

BACKGROUND OF THE INVENTION

Diesel particulate filters (DPFs) form a known part of certain diesel engine exhaust gas systems trapping significant amounts of pollutants such as hydrocarbons, carbon monoxide and ash (soot) as the exhaust gas travels through them, i.e., the DPFs. The functional efficiency of a DPF tends to decrease as the amount of pollutants it has entrapped increases. It is, therefore, incumbent on the operator/owner of the vehicle to at least periodically clean or regenerate the DPF.

DPFs may be regenerated by raising their internal temperatures to temperature values suitable for flashing and flushing the pollutants, i.e., cleaning the DPFs. Such a rise in temperature may be accomplished by increasing the temperature of the exhaust gases passing through the DPFs. In cold conditions, a rise in exhaust gas temperatures may be accomplished by an increased load on the engine. Increasing the volume of exhaust gas throughput may enhance the flushing of such pollutants. Increasing the volume of exhaust gas throughput may enhance the flushing of such pollutants. There are a variety of methods used to increase the temperature of gases flowing through the DPFs.

Regardless of the method chosen to increase the temperature of the exhaust gas to a threshold level, the regeneration process will, at times, be prolonged. Thus, a need or desire may arise to regenerate a DPF while the operator is away from the machine.

SUMMARY OF THE INVENTION

With a desire for DPF regeneration while the operator is absent from the machine (“unmanned regeneration”), the inventors have recognized a need for the machine to act somewhat as if the operator is present to, among other things, avoid possible damage to the machine should unfavorable operational conditions develop during regeneration. Thus the machine will complete DPF regeneration and follow normal automatic shutdown procedures under normal operating conditions while the machine is parked and will follow immediate shutdown procedures if/when a critical fault occurs during regeneration, critical fault being defined as a condition that could cause damage or undue wear to the machine. A critical fault is, among other things, an occurrence of a detected value that is unfavorable, i.e., that falls outside of an acceptable predetermined range of values, for engine oil pressure, engine coolant temperature or engine coolant level. Such occurrences may lead to a lower life or a complete failure of the engine. Various critical faults are described and illustrated in the specification which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a vehicle which may make use of the invention;

FIG. 2 is schematic of the engine and control system;

FIG. 3 is an alternative view of the engine and control system with controller 100; and

FIG. 4 is a flowchart illustrating the workings of an embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a side view of a work vehicle, i.e., a loader 10 having an operator cab 20; wheels 30 for powered movement along the ground; an engine 40. Such a work vehicle, as well as others, may be suitable for use of the invention.

FIG. 2 is a schematic of parts of the vehicle involved in an exemplary embodiment of the invention. Illustrated is a vehicle controller unit (“VCU”) 15 which controls various functions of the vehicle 10; an engine 40; an engine speed sensor 40a; an exhaust 40b providing a route for engine exhaust gases; a throttle 41 capable of being engaged and not engaged; a throttle position sensor 41a capable of detecting whether the throttle 41 is engaged or not engaged; an engine oil pressure sensor 42a; an engine coolant temperature sensor 43; an engine coolant level sensor 44; an engine controller unit (“ECU”) 45 capable of controlling the functions of the engine 40; a transmission 50 capable of being in a forward, a reverse, or a neutral gear; a transmission gear sensor 50a; a park brake 55 capable of being engaged and disengaged; a park brake sensor 55a capable of detecting if the park brake 55 is engaged or disengaged; an ignition 60 having an on position and an off position through which the vehicle may be powered by an electrical power source 70 which may be a battery, an alternator or some other device when the ignition is in a first position and the vehicle 10 is shutdown when the ignition 60 is in a second position; a diesel particulate filter (“DPF”) 80; an exhaust gas temperature sensor 81; a fuel dosing injector 82; a diesel oxidation chamber (“DOC”) 83; and a timer 90 by which the ECU 45 and the VCU 15 measure time passed.

The vehicle 10 is considered to be in a parked regeneration state, i.e., a state suitable for parked regeneration, when the following conditions exist: (1) the ignition is on; (2) the transmission 50 is in a neutral gear; (3) the park brake 55 is engaged; (4) the engine speed is at standby idle, i.e., the throttle 42 is not engaged; and (5) the DPF soot level is high. The ECU 45 may determine soot level by monitoring exhaust gas temperatures over time and using a lookup table to calculate the difference between soot accumulated over time and soot burned or oxidized over time. Alternatively, the ECU 45 may determine soot level as a mere function of total amount of time the engine has been running since the soot level was determined to be zero (“0”). Regardless of the method, the ECU determines filter soot level. The VCU 15 may allow the vehicle 10 to begin parked regeneration of the DPF 80 when the vehicle 10 is in the parked regeneration state. Parked regeneration may continue as long as the vehicle 10 is in the parked regeneration state. When the state of the vehicle 10 changes, i.e., when one of conditions (1) through (5) (above) do not exist, the VCU 15 may discontinue any ongoing parked regeneration process. An exemplary parked regeneration process will now be described below.

The exemplary parked regeneration process begins when the vehicle is in a parked regeneration state and the VCU 15 receives a mechanical or electrical signal from the operator of the vehicle 10, via a switch, to actively clean or regenerate the DPF 80, i.e., to begin the parked regeneration. The VCU 15 then signals the ECU 45 to begin engine speed management (“ESM”), i.e., to use values transmitted by the exhaust temperature sensor 81 to determine a required engine speed for bringing the exhaust gas temperature to at least a predetermined regeneration temperature which, in this exemplary embodiment, may be at least 275° C. This may allow the DOC 83 to bring exhaust gas temperatures to at least 575° C. prior to the exhaust gas entering the DPF 80. The fuel dosing injector 82 will inject fuel into the exhaust gas as necessary to bring the additional temperature rise when the exhaust gas enters the DOC 83 for additional burning or oxidation. The ECU 45 then determines the required engine speed via the use of a lookup table cross referencing required engine speeds and exhaust gas temperatures. The ECU 45 then adjusts engine speed to the required engine speed and continues monitoring the exhaust gas temperatures and making adjustments in engine speed using required engine speeds until parked regeneration is complete or canceled. The parked regeneration of the DPF 80 may be normally complete when the ECU 45 determines that the DPF 80 is regenerated and cancels the regeneration signal to the VCU 15. This determination may be made via the passage of a first predetermined length of time for parked regeneration as measured by the timer 90. When parked regeneration is complete, the ECU 45 discontinues ESM allowing the engine 40 to return to standby idle speed, i.e., an unthrottled idle speed. Engine coolant may then be allowed to cool down to a first predetermined coolant temperature as detected by the engine coolant temperature sensor 43. Once the engine coolant has cooled to the first predetermined coolant temperature, the VCU 15 initializes the timer 90 and continues to allow the engine to idle for a second predetermined length of time as measured by the timer 90. When the timer 90 indicates that the predetermined length of time has passed, the VCU 15 turns the ignition 60 off, shutting down the vehicle 10. If the vehicle 10 is taken out of the parked regeneration state by the operator via, for example, placing the transmission 50 in a non-neutral gear or making some other demand on the vehicle 10, i.e., the operator begins to engage the vehicle for locomotion or work operations, the VCU 15 signals the ECU 45 to end ESM, immediately canceling the parked regeneration, and returning the vehicle 10 to normal operation.

The parked regeneration of the DPF 80 may also be affected by the occurrence of one or more critical faults, i.e., conditions under which the vehicle may be damaged. In this exemplary embodiment, the following may be considered to be critical faults: (a) engine oil pressure falls below a predetermined operational level; (b) engine coolant rises above a second predetermined coolant temperature; and (c) engine coolant level falls below a predetermined coolant level. If a critical fault occurs during a parked regeneration, the VCU 15 signals the ECU 45 to cancel the parked regeneration and turns the ignition off, immediately shutting the vehicle 10 down.

FIG. 3 illustrates how the sensors, the timer 95 and a warning device 96 may communicate with the controller unit combination 100. In this exemplary embodiment the warning device 96 may be a monitor, audible sound generator or some other device including a switch and may, among other things, indicate: the vehicle 10 is ready for parked regeneration of the DPF 80; the vehicle 10 will/has shut down due to a critical fault; or parked regeneration of the DPF 80 has been canceled due to the vehicle being taken out of the parked regeneration state.

FIG. 4 illustrates a flowchart that may represent the manner in which this exemplary embodiment works. As illustrated in FIG. 4, the entire process begins at step 100 with the ignition 11 and the engine 40 on. If the soot level in the DPF 80 is calculated to be within a predefined range, the warning device 96 may signal the operator that a filter regeneration would be appropriate, at which point the operator manipulates a switch which, in this case is located on the warning device 96, requesting a parked regeneration. the VCU 15 then signals the ECU 45 to start parked regeneration at step 110. If the park brake 55 is engaged, a neutral gear is selected, and the throttle is not engaged in steps 120, 130 and 140, the VCU 15 may move to step 160 if engine oil pressure is not less than a predetermined pressure, engine coolant temperature is not greater than a first predetermined temperature, and the coolant level is not less than a predetermined level in steps 150a, 150b and 150c. At step 160, the VCU 15 signals the ECU 45 to begin ESM. At step 170, the the ECU 45 proceeds to ESM at step 170 and maintains ESM until the time elapsed is greater than or equal to a first predetermined time. Once the time elapsed is greater than or equal to the first predetermined time, ESM is canceled allowing the engine to return to standby idle at step 181. The timer is restarted at step 182, to begin a cool down period at step 183 which lasts until the time elapsed is greater than or equal to a second predetermined time at which time the vehicle 10 is shut down. As illustrated, if, at any time, the vehicle 10 moves out of the regeneration state at steps 120, 130 and 140, the VCU 15 signals the ECU 45 to cancel regeneration of the DPF 80 at step 141 and to allow the engine 40 to return to standby idle. Also, if at any time, the oil pressure is less than the predetermined oil pressure, the coolant temperature is greater than the predetermined coolant temperature, or the coolant level is less than the predetermined coolant level at steps 150a, 150b, or 150c, the vehicle 10 is shut down at step 190.

Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.

Claims

1. A method of cleaning a filter for engine exhaust gas, comprising:

a. Step 1—automatically monitoring engine oil pressure, engine coolant temperature and engine coolant level for the occurrence of a critical fault which includes a detected value outside a predetermined range for at least one of the engine oil pressure, the engine coolant temperature, and the engine coolant level;

b. Step 2—automatically monitoring a state of a park brake to determine if the park brake is in a first state or a second state, a throttle capable of being engaged and disengaged to determine if the throttle is engaged, a transmission gear to determine if the transmission is in a neutral gear, and a filter soot level;

c. Step 3—automatically beginning engine speed management to increase a temperature of exhaust gas when: the park brake is in the first state, the throttle is disengaged, the transmission is in a neutral gear, a filter soot level is within a predetermined range of values, and the critical fault has not occurred;

d. Step 4—maintaining engine speed management until one of a predetermined amount of time has elapsed, the bark brake is in the second state, the throttle is engaged or the transmission is not in the neutral gear;

e. Step 5—automatically executing an engine shutdown procedure after Step 4 is complete or upon the occurrence of the critical fault.

2. The method of claim 1, wherein the engine shutdown procedure includes immediate engine shutdown upon the occurrence of the critical fault.

3. The method of claim 1, wherein the engine shutdown procedure includes an engine cool down prior to the engine shutdown.

4. A method of regenerating filter for exhaust gas a work vehicle, comprising the following steps:

a. Step 1—monitoring at least one of an oil pressure level, an engine coolant temperature, and an engine coolant level;

b. Step 2—monitoring a state of a park brake to determine if the park brake is in a first state or a second state;

c. Step 3—monitoring an engine speed;

d. Step 4—monitoring a state of a throttle having a first state and a second state.

e. Step 5—initiating engine speed management to increase the temperature of the exhaust gas to at least a predetermined temperature required for filter regeneration only if: (1) the at least one of an oil pressure level, an engine coolant temperature, and an engine coolant level is within a predetermined range, (2) the park brake is in a first state, and (3) the throttle is not engaged;

f. Step 6—maintaining the engine speed management until one of a predetermined amount of time has elapsed or the at least one of an oil pressure level, an engine coolant temperature, and an engine coolant level is not within the predetermined range; and

g. Step 7—automatically executing an engine shutdown procedure when Step 6 is complete.

5. The method of claim 4, wherein the engine shutdown procedure includes:

abandoning the engine speed management and allowing it to return to standby idle speed until the engine coolant temperature falls below a predetermined threshold and, subsequently shutting down the engine.

6. The method of claim 4, wherein the engine shutdown procedure includes immediately shutting down the engine when the at least one of an oil pressure level, an engine coolant temperature, and an engine coolant level is not within a predetermined range.

7. A method of filter cleaning, comprising the following steps:

a. Step 1—monitoring at least one of an oil pressure level, an engine coolant temperature, and an engine coolant level;

b. Step 2—monitoring a state of a park brake to determine if the park brake is in a first state or a second state;

c. Step 3—monitoring an engine speed;

d. Step 4—automatically managing the engine speed to raise and keep exhaust gas temperatures to a predetermined range for regeneration of the filter if: (1) the at least one of an oil pressure level, an engine coolant temperature, and an engine coolant level is within a predetermined range and (2) the parked brake is in a first state;

e. Step 5—continuing to manage the engine speed until one of a predetermined amount of time has elapsed or the at least one of an oil pressure level, an engine coolant temperature, and an engine coolant level is not within the predetermined range; and

f. Step 6—automatically executing an engine shutdown procedure when Step 5 is complete.

8. The method of claim 7, wherein automatically managing the engine speed is discontinued when the park brake is adjusted to the second state.

9. The method of claim 7, wherein the engine shutdown procedure comprises an immediate shutdown of the engine when the at least one of an oil pressure level, an engine coolant temperature, and an engine coolant level is not within the predetermined range.