ENGINE CONTROL DEVICE

Abstract

The electronic control unit includes a calculation processing device and a storage device. The calculation processing device calculates an engine operation amount by using a transition time map in a transition period in which a difference between an outlet water temperature and a heater inlet water temperature is not less than a transition determination value after water flow into a first temperature raising water passage in which a heater core is provided or a second temperature raising water passage in which a water-to-water heat exchanger is provided is started by a switching valve, and by using a normal time map in a period other than the transition period. The normal time map and the transition time map are configured such that an outlet water temperature in a case where the same value is output is a lower temperature in the transition time map than in the normal time map.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2025-031986 filed on February 28, 2025. The disclosure of the above-identified application, including the specification, drawings, and claims, is incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to an engine control device.

2. Description of Related Art

As an engine mounted in a vehicle or the like, an engine is known that includes a circulation circuit of an engine coolant that is configured to cool, using a radiator, the engine coolant that has passed through an inside of the engine to recover heat, and to return the engine coolant back to the inside of the engine thereafter. A thermostat is provided in the circulation circuit of the engine coolant. The thermostat is configured to stop flow of the engine coolant through the radiator by closing a valve when the engine is cool and to start the flow of the engine coolant through the radiator by opening the valve when the engine is warm.

Further, an engine configured to use heat recovered by an engine coolant from an engine for heating a vehicle cabin or raising a temperature of a battery is also known, as seen in Japanese Unexamined Patent Application Publication No. 2024-113860 (JP 2024-113860 A). A cooling system of the engine is provided with a heater core, a water-to-water heat exchanger, and a switching valve. The heater core is a heat exchanger configured to exchange heat between air blown into the vehicle cabin and the engine coolant. The water-to-water heat exchanger is a heat exchanger configured to exchange heat between a battery coolant that is caused to circulate through an inside of the battery and the engine coolant. The switching valve is a valve that switches between a state in which flow of the engine coolant to the heater core and the water-to-water heat exchanger is not allowed and a state in which the flow of the engine coolant to the heater core and the water-to-water heat exchanger is allowed.

SUMMARY

In an engine mounted in a vehicle or the like, during a warm-up operation, an engine operation amount such as a fuel injection amount or an ignition timing is adjusted in accordance with a temperature of an engine coolant. When flow of the engine coolant to a heater core or a water-to-water heat exchanger is started during the warm-up operation, the engine coolant that is cold that has been retained in the heater core or the water-to-water heat exchanger until then flows into the engine. As a result, a so-called water temperature drop in which the temperature of the engine coolant temporarily drops may occur. In a case where the engine operation amount during the warm-up operation is adjusted in accordance with the temperature of the engine coolant, when the water temperature drop occurs, a value of the engine operation amount may change inappropriately. As a result, there is a concern that a combustion state of the engine will deteriorate.

An engine control device that solves the above-described problem is an engine control device that controls an engine in which, as flow paths for an engine coolant that returns from an outlet of a water jacket to an inlet of the water jacket, a radiator water passage provided through a radiator, a temperature raising water passage provided with a temperature raising heat exchanger for raising a temperature of another fluid with heat of the engine coolant, and a bypass water passage through which the engine coolant flows while the engine coolant bypasses the radiator and the temperature raising heat exchanger are provided in parallel, and a thermostat configured to open and close the radiator water passage and a switching valve configured to switch between a state in which flow of the engine coolant from the temperature raising water passage into the water jacket is not allowed and a state in which the flow of the engine coolant from the temperature raising water passage into the water jacket is allowed are provided in a cooling system. The engine control device includes a calculation processing device and a storage device. The storage device is configured to store a normal time map and a transition time map as maps that use, as input, an outlet water temperature that is a temperature of the engine coolant flowing out of the water jacket and output a value that is used for calculating an engine operation amount. The calculation processing device is configured to calculate, during a transition period that is a period until a difference between a temperature of the engine coolant flowing out of the temperature raising heat exchanger and the outlet water temperature decreases below a predetermined value after the switching valve switches from the state in which the flow of the engine coolant from the temperature raising water passage into the water jacket is not allowed to the state in which the flow of the engine coolant from the temperature raising water passage into the water jacket is allowed, the engine operation amount using the transition time map, and calculate, during a period other than the transition period, the engine operation amount using the normal time map. The normal time map and the transition time map are configured such that the outlet water temperature when the normal time map and the transition time map output the same value is lower on the transition time map than on the normal time map.

The engine control device has an effect of reducing deterioration of a combustion state due to a water temperature drop.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

FIG. 1 is a diagram schematically showing a configuration of an embodiment of an engine control device;

FIG. 2 is a flowchart of an engine operation amount calculation process executed in the engine control device of FIG. 1;

FIG. 3 is a graph showing a relationship between the outlet water temperature and the warm-up time incremental correction coefficient in each of the normal time map and the transition time map;

FIG. 4 is a graph showing a relationship between the outlet water temperature and the target EGR rate in each of the normal time map and the transition time map; and

FIG. 5 is a time chart in which (A) of FIG. 5 shows transitions of an opening and closing state of the temperature raising water passage, (B) of FIG. 5 shows transitions of an outlet water temperature and a heater inlet water temperature, (C) of FIG. 5 shows a transition of a warm-up time incremental correction coefficient, and (D) of FIG. 5 shows a transition of a target EGR rate, in the engine control device of FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the engine control device will be described in detail with reference to FIGS. 1 to 5.

Configuration of Engine 10 and Cooling System

First, a configuration of an engine 10 and a cooling system thereof to which the engine control device of the present embodiment is applied will be described with reference to FIG. 1. The engine 10 is mounted on a hybrid electric vehicle. In FIG. 1, an arrow indicates a flow direction of the engine coolant and the battery coolant in the cooling system of the engine 10.

Various actuators are provided in the engine 10. The driving state of the engine 10 is controlled through the operation of the actuators. Examples of the actuators include an injector 10A that injects fuel to be combusted in the engine 10, an ignition device 10B that ignites the fuel by spark discharge, and an exhaust gas recirculation valve 10C that adjusts the amount of exhaust gas recirculated from the exhaust system to the intake system of the engine 10.

The engine 10 includes a cooling system that cools the engine 10 by circulating engine coolant through a water jacket 11 provided therein. While the engine 10 is being operated, the engine coolant flows from the inlet 12 to the outlet 13 in the water jacket 11. The cooling system of the engine 10 includes an engine water pump 20 that pumps the engine coolant toward the inlet 12 of the water jacket 11. In the present embodiment, an electric pump is adopted as the engine water pump 20. In the cooling system of the engine 10, four water passages including a bypass water passage 14, a radiator water passage 15, a first temperature raising water passage 16, and a second temperature raising water passage 17 are provided in parallel as flow paths of the engine coolant that flows from the outlet 13 of the water jacket 11 to the inlet 12. The water passages (14 to 17) include a portion shared with each other.

The bypass water passage 14 is configured to pass through the thermostat 19 and the engine water pump 20 in this order from the outlet 13 of the water jacket 11 and to return to the inlet 12 of the water jacket 11. The radiator water passage 15 is configured to pass through the radiator 21, the reservoir tank 22, the thermostat 19, and the engine water pump 20 in this order from the outlet 13 of the water jacket 11 and to return to the inlet 12 of the water jacket 11. The radiator 21 is a heat exchanger for cooling the engine coolant by heat exchange with the outside air. The reservoir tank 22 is a storage container for the engine coolant. The thermostat 19 opens and closes the radiator water passage 15 according to the temperature of the engine coolant flowing in. Specifically, the thermostat 19 is configured to close the radiator water passage 15 when the temperature of the engine coolant is lower than the set temperature and to open the radiator water passage 15 when the temperature of the engine coolant is equal to or higher than the set temperature. The state in which the radiator water passage 15 is opened here indicates a state in which the engine coolant flows through the radiator water passage 15. In addition, the state in which the radiator water passage 15 is closed indicates a state in which the flow of the engine coolant through the radiator water passage 15 is stopped.

The first temperature raising water passage 16 is configured to pass through the switching valve 18, the heater core 23, the heater water pump 24, the electric heater 25, and the engine water pump 20 in this order from the outlet 13 of the water jacket 11 and to return to the inlet 12 of the water jacket 11. The switching valve 18 is a valve for changing a flow rate allocation of the engine coolant in each water passage, and details thereof will be described later. The heater core 23 is a heat exchanger that exchanges heat between the air blown into the vehicle cabin and the engine coolant, and is used to warm the air blown with the heat of the engine coolant when the vehicle cabin is heated. The heater water pump 24 is an electric pump. The electric heater 25 generates heat in response to power supply to heat the engine coolant.

The second temperature raising water passage 17 is configured to pass through the switching valve 18, the water-to-water heat exchanger 26, the heater water pump 24, the electric heater 25, and the engine water pump 20 in this order from the outlet 13 of the water jacket 11 and to return to the inlet 12 of the water jacket 11. The water-to-water heat exchanger 26 is a heat exchanger that exchanges heat between the battery coolant and the engine coolant. The battery coolant is a coolant that is circulated through the battery water passage 28 and is used for adjusting the temperature of the battery 27. The water-to-water heat exchanger 26 is used to warm the battery coolant with the heat of the engine coolant when the battery 27 is heated. In the present embodiment, each of the heater core 23 and the water-to-water heat exchanger 26 corresponds to a temperature raising heat exchanger for increasing the temperature of another fluid with the heat of the engine coolant. Further, in the present embodiment, the bypass water passage 14 is configured as a water passage through which the engine coolant flows by bypassing the radiator 21 and the temperature raising heat exchanger (the heater core 23 and the water-to-water heat exchanger 26).

The switching valve 18 allocates the flow rate of the engine coolant flowing from the outlet 13 of the water jacket 11 to the first temperature raising water passage 16 and the second temperature raising water passage 17. The switching valve 18 constitutes four states (A1) to (A4). The state (A1) is a state in which the flow of the engine coolant from the outlet 13 of the water jacket 11 to both the first temperature raising water passage 16 and the second temperature raising water passage 17 is stopped. The state (A2) is a state in which the engine coolant flows from the outlet 13 of the water jacket 11 to solely the first temperature raising water passage 16 among the first temperature raising water passage 16 and the second temperature raising water passage 17. The state (A3) is a state in which the engine coolant flows from the outlet 13 of the water jacket 11 to solely the second temperature raising water passage 17 among the first temperature raising water passage 16 and the second temperature raising water passage 17. The state (A4) is a state in which the engine coolant flows from the outlet 13 of the water jacket 11 to both the first temperature raising water passage 16 and the second temperature raising water passage 17.

In addition, the cooling system of the engine 10 is provided with an outlet water temperature sensor 30 and a heater inlet water temperature sensor 31. The outlet water temperature sensor 30 is a sensor that detects the outlet water temperature THW1 that is the temperature of the engine coolant flowing out of the outlet 13 of the water jacket 11. The heater inlet water temperature sensor 31 is a sensor that detects a heater inlet water temperature THW2 that is a temperature of the engine coolant flowing through a portion of the first temperature raising water passage 16 and the second temperature raising water passage 17 on a downstream side of the heater water pump 24 and an upstream side of the electric heater 25. The heater inlet water temperature THW2 when the engine coolant flows through the first temperature raising water passage 16 and the second temperature raising water passage 17 corresponds to the temperature of the engine coolant flowing out of the heater core 23 and the water-to-water heat exchanger 26.

Further, the cooling system of the engine 10 is provided with a return water passage 29 that is a water passage connecting a portion of the first temperature raising water passage 16 and the second temperature raising water passage 17 downstream of the electric heater 25 and the switching valve 18. Even in the state (A1), the switching valve 18 can connect the return water passage 29 to at least one of the first temperature raising water passage 16 and the second temperature raising water passage 17 to flow the engine coolant through the first temperature raising water passage 16 and the second temperature raising water passage 17. Then, even when the engine 10 is stopped, it is possible to perform heating of the vehicle cabin and heating of the battery 27 by operating the heater water pump 24 and the electric heater 25 in the state. The engine control device of the present embodiment is configured to circulate the engine coolant through the first temperature raising water passage 16 or the second temperature raising water passage 17 via the return water passage 29 when the heating of the vehicle cabin or the heating of the battery 27 is requested during the electric traveling of the hybrid electric vehicle.

Configuration of Engine Control Device

Next, a configuration of the engine control device according to the present embodiment will be described with reference to FIG. 1. The engine control device according to the present embodiment includes an electronic control unit 32. The electronic control unit 32 includes a calculation processing device 33 and a storage device 34. The storage device 34 stores in advance a program and data for engine control. The electronic control unit 32 is configured to execute various types of processes for controlling the engine by reading and executing the program from the storage device 34 by the calculation processing device 33. The detection signals X1, X2 of the outlet water temperature sensor 30 and the heater inlet water temperature sensor 31 are input to the electronic control unit 32. In addition, the electronic control unit 32 receives detection signals of sensors provided in each part of the hybrid electric vehicle. Examples of the detection signal include a detection signal X3 of an air flow meter 35, a detection signal X4 of an intake air temperature sensor 36, a detection signal X5 of a vehicle speed sensor 37, a detection signal X13 of an accelerator pedal sensor 38, and a detection signal X14 of a crank angle sensor 39. The air flow meter 35 is a sensor that detects an intake air amount GA of the engine 10. The intake air temperature sensor 36 is a sensor that detects an intake air temperature THA of the engine 10. The vehicle speed sensor 37 is a sensor that detects a vehicle speed SPD of the hybrid electric vehicle. The accelerator pedal sensor 38 is a sensor that detects an accelerator pedal depression amount ACC by a driver of the hybrid electric vehicle. The crank angle sensor 39 is a sensor that detects a crank angle that is a rotation angle of a crank shaft that is an output shaft of the engine 10. The calculation processing device 33 calculates an engine rotation speed NE that is a rotation speed of the crank shaft based on the detection signal X14 of the crank angle sensor 39. In addition, the calculation processing device 33 calculates an engine load rate KL based on the engine rotation speed NE, the detection signal X3 of the air flow meter 35, and the like. The engine load rate KL represents an intake filling rate of a combustion chamber of the engine 10.

Engine Operation Amount Calculation Process

The calculation processing device 33 calculates an operation amount of the engine 10 based on the detection result of each sensor. Examples of the operation amount of the engine 10 calculated by the calculation processing device 33 include a fuel injection amount of the injector 10A, an ignition timing of the fuel by the ignition device 10B, and an EGR opening degree that is an opening degree of the exhaust gas recirculation valve 10C. In addition, the calculation processing device 33 calculates an operation amount of the cooling system, such as the switching valve 18, the engine water pump 20, the heater water pump 24, and the electric heater 25. Then, the calculation processing device 33 outputs the command signals X6 to X12 corresponding to the operation amount to the injector 10A, the ignition device 10B, the exhaust gas recirculation valve 10C, the switching valve 18, the engine water pump 20, the heater water pump 24, and the electric heater 25. As a result, the electronic control unit 32 controls the engine 10 and the cooling system.

FIG. 2 shows a flowchart of a process executed by the calculation processing device 33 for calculating the engine operation amount. The calculation processing device 33 repeatedly executes the process of FIG. 2 for each predetermined control cycle during the operation of the engine 10. A reference numeral "S" before the reference numerals in the drawings indicates a step.

In a case in which the process of FIG. 2 is started, the calculation processing device 33 first acquires an engine rotation speed NE, an engine load rate KL, an accelerator pedal depression amount ACC, an outlet water temperature THW1, and a heater inlet water temperature THW2 in step 100. Subsequently, in step 102, the calculation processing device 33 subtracts the heater inlet water temperature THW2 from the outlet water temperature THW1 and calculates a value of the subtracted value as a water temperature difference ΔT.

Next, in step 104, the calculation processing device 33 determines whether the transition period is in progress. In a case in which the calculation processing device 33 determines that the transition period is in progress (YES), the process proceeds to step 106, and in a case in which the calculation processing device 33 determines that the transition period is not in progress (NO), the process proceeds to step 112. As will be described later, in the main process, the calculation processing device 33 determines the start and end of the transition period, and a period from a determination that the transition period is started to a determination that the transition period is ended is the transition period.

In a case in which the process proceeds to step 112, the calculation processing device 33 determines whether the water flow in the heater core 23 or the water-to-water heat exchanger 26 is started in step 112. Specifically, the calculation processing device 33 determines that the transition from a state (A1) to a state (A2) is the start of the water flow in the heater core 23 or the water-to-water heat exchanger 26. The state (A1) is a state in which the flow of the engine coolant from both the first temperature raising water passage 16 and the second temperature raising water passage 17 to the water jacket 11 is prohibited. The state (A2) is a state in which the flow of the engine coolant from at least one of the first temperature raising water passage 16 and the second temperature raising water passage 17 to the water jacket 11 is allowed. The switching from the state (A1) to the state (A2) is performed by the switching valve 18. In the present embodiment, the calculation processing device 33 performs the determination in step 112 based on the operation amount commanded to the switching valve 18.

In a case in which determination is made that the water flow in the heater core 23 or the water-to-water heat exchanger 26 is not started (NO), the calculation processing device 33 proceeds to step 110. In step 110, the calculation processing device 33 calculates the engine operation amount using the normal time map stored in the storage device 34 in advance, and then ends the process of FIG. 2 in the present control cycle.

On the other hand, in a case in which determination is made in step 112 that the water flow in the heater core 23 or the water-to-water heat exchanger 26 is started (YES), the calculation processing device 33 determines whether the water temperature difference ΔT is equal to or higher than the predetermined transition determination value in step 114. In a case in which determination is made that the water temperature difference ΔT is smaller than the transition determination value (NO), the calculation processing device 33 proceeds to step 110. On the other hand, in a case in which determination is made that the water temperature difference ΔT is equal to or higher than the transition determination value (YES), the calculation processing device 33 determines that the transition period has started in step 118. In step 120, the calculation processing device 33 calculates the engine operation amount using the transition time map stored in the storage device 34 in advance, and then ends the process of FIG. 2 in the present control cycle.

In addition, in a case in which determination is made in step 104 that the transition period is in progress and the process proceeds to step 106, the calculation processing device 33 determines in step 106 whether the water temperature difference ΔT is smaller than the transition determination value. In a case in which the calculation processing device 33 determines that the water temperature difference ΔT is smaller than the transition determination value (YES), the process proceeds to step 108, and in a case in which the calculation processing device 33 determines that the water temperature difference ΔT is equal to or higher than the transition determination value (NO), the process proceeds to step 120. In a case in which the process proceeds to step 108, the calculation processing device 33 determines in step 108 that the transition period is ended, and then proceeds to step 110.

In the determination value setting process, the calculation processing device 33 determines a period in which the water temperature difference ΔT, that is, the difference between the outlet water temperature THW1 and the heater inlet water temperature THW2 is equal to or higher than the transition determination value after the switching from the state (A1) to the state (A2) by the switching valve 18 as the transition period. The calculation processing device 33 calculates the engine operation amount using the transition time map during the transition period and using the normal time map during the period other than the transition period.

Specific Example of Engine Operation Amount Calculation

Next, a specific example of an aspect of the calculation of the engine operation amount in step 110 and step 120 of FIG. 2 will be described.

First, an aspect of the calculation of the fuel injection amount will be described. In a case of calculating the fuel injection amount, the calculation processing device 33 first calculates the basic injection amount based on the engine rotation speed NE, the engine load rate KL, and the like. Next, the calculation processing device 33 calculates various correction coefficients. The various correction coefficients include a warm-up time incremental correction coefficient calculated based on the outlet water temperature THW1. The calculation processing device 33 multiplies each of the calculated correction coefficients by the basic injection amount and calculates the multiplied value as the final fuel injection amount. The storage device 34 stores two maps of the normal time map and the transition time map as a map for calculating the warm-up time incremental correction coefficient. The calculation processing device 33 calculates the warm-up time incremental correction coefficient using the transition time map during the transition period and using the normal time map during the other period. The normal time map and the transition time map for calculating the warm-up time incremental correction coefficient are configured to output the warm-up time incremental correction coefficient in response to the input of the outlet water temperature THW1.

FIG. 3 shows a relationship between the outlet water temperature THW1 and the warm-up time incremental correction coefficient in each of the normal time map and the transition time map. In both the normal time map and the transition time map, "1" is set as the value of the warm-up time incremental correction coefficient in a range where the outlet water temperature THW1 is equal to or higher than a predetermined value. The value of the warm-up time incremental correction coefficient is set as a value that increases in response to the decrease in the outlet water temperature THW1 in a range where the outlet water temperature THW1 is lower than the predetermined value. However, in a range where the outlet water temperature THW1 is lower than the predetermined value, the value of the warm-up time incremental correction coefficient in the transition time map is set to a value smaller than the value of the warm-up time incremental correction coefficient in the normal time map at the same outlet water temperature THW1. That is, the normal time map and the transition time map for calculating the warm-up time incremental correction coefficient are configured such that the outlet water temperature THW1 when the same value is output is a lower temperature in the transition time map than in the normal time map.

Next, an aspect of calculating the EGR opening degree will be described. In calculating the EGR opening degree, the calculation processing device 33 first calculates a target EGR rate that is a control target value of the EGR rate, based on the engine rotation speed NE, the engine load rate KL, and the outlet water temperature THW1. The EGR rate represents a ratio of the recirculated exhaust gas to the intake air introduced into the combustion chamber of the engine 10. The calculation processing device 33 calculates the opening degree of the exhaust gas recirculation valve 10C required for the recirculation of the exhaust gas in an amount corresponding to the target EGR rate as the EGR opening degree. The storage device 34 stores two maps of the normal time map and the transition time map as the map for calculating the target EGR rate. The calculation processing device 33 calculates the target EGR rate using the transition time map in the transition period and using the normal time map in the other periods. The normal time map and the transition time map for calculating the target EGR rate are configured to output the target EGR rate in response to the input of the engine rotation speed NE, the engine load rate KL, and the outlet water temperature THW1.

FIG. 4 shows a relationship between the outlet water temperature THW1 and the target EGR rate in each of the normal time map and the transition time map under conditions in which the engine rotation speed NE and the engine load rate KL are constant. In both the normal time map and the transition time map, in a low water temperature region in which the outlet water temperature THW1 is lower than a certain value, "0" is set as the value of the target EGR rate. In addition, in a high water temperature region in which the outlet water temperature THW1 is higher than a certain value, a constant value is set as the value of the target EGR rate. In addition, in an intermediate water temperature region between the low water temperature region and the high water temperature region, the target EGR rate is set to be a value that increases from the value "0" of the low water temperature region to the value of the high water temperature region in response to an increase in the outlet water temperature THW1. However, in the transition time map in the intermediate water temperature region, a value larger than the value of the target EGR rate in the normal time map at the same outlet water temperature THW1 is set as the value of the target EGR rate. The normal time map and the transition time map used for calculating the target EGR rate are also configured such that the outlet water temperature THW1 at which the same value is output is lower in the transition time map than in the normal time map.

Subsequently, an aspect of calculating the ignition timing will be described. In a case of calculating the ignition timing, the calculation processing device 33 first calculates the basic ignition timing based on the engine rotation speed NE, the engine load rate KL, and the like. The calculation processing device 33 calculates various ignition timing correction amounts, and calculates a value obtained by correcting the basic ignition timing with the calculated correction amount as the value of the ignition timing. The ignition timing correction amount includes a warm-up advance angle correction amount calculated based on the outlet water temperature THW1. The warm-up advance angle correction amount is set as a value for correcting the ignition timing toward the advance angle side. The storage device 34 stores two maps, the normal time map and the transition time map, as a map for calculating the warm-up advance angle correction amount. In the transition period, the calculation processing device 33 calculates the warm-up advance angle correction amount using the transition time map, and in a period other than the transition period, the calculation processing device 33 calculates the warm-up advance angle correction amount using the normal time map. The normal time map and the transition time map for calculating the warm-up advance angle correction amount are configured to output the warm-up advance angle correction amount in response to the input of the outlet water temperature THW1. In both the normal time map and the transition time map, the value of the warm-up advance angle correction amount is set to "0" in a range in which the outlet water temperature THW1 is equal to or higher than a predetermined value. In a range in which the outlet water temperature THW1 is lower than the predetermined value, the value of the warm-up advance angle correction amount is set as a value that increases in response to a decrease in the outlet water temperature THW1. However, a value of the warm-up advance angle correction amount in the transition time map in a range in which the outlet water temperature THW1 is lower than the predetermined value is set to a value smaller than a value of the normal time map at the same outlet water temperature THW1. In the normal time map and the transition time map used for calculating the warm-up advance angle correction amount, the outlet water temperature THW1 in a case of outputting the same value is configured to be a lower temperature in the transition time map than in the normal time map.

Operation of Embodiment

During the warm-up operation of the engine 10, the wall surface temperature of the combustion chamber is low, and the combustion may be unstable due to deterioration in vaporization of the injected fuel or a decrease in the combustion speed. The calculation processing device 33 adjusts the engine operation amount, such as the fuel injection amount, the EGR opening degree, and the ignition timing, based on the outlet water temperature THW1, to suppress the deterioration of the combustion during the warm-up operation. Specifically, the calculation processing device 33 adjusts the fuel injection amount during the warm-up operation to be increased more than after the warm-up completion by the warm-up time incremental correction coefficient calculated based on the outlet water temperature THW1. In addition, the calculation processing device 33 adjusts the recirculated exhaust amount during the warm-up operation to be reduced more than after the warm-up completion by calculating the target EGR rate based on the outlet water temperature THW1. Furthermore, the calculation processing device 33 adjusts the ignition timing during the warm-up operation to be advanced more than after the warm-up completion by the warm-up advance angle correction amount calculated based on the outlet water temperature THW1.

During the warm-up operation of the engine 10, the engine coolant circulated through the water jacket 11 is heated by receiving heat from the engine 10. Therefore, during the warm-up operation, the wall surface temperature of the combustion chamber changes in correlation with the outlet water temperature THW1. Therefore, the calculation processing device 33 adjusts the engine operation amount to be an appropriate value corresponding to the wall surface temperature of the combustion chamber by using the outlet water temperature THW1.

Meanwhile, during the warm-up operation of the engine 10, water flow in the first temperature raising water passage 16 or the second temperature raising water passage 17 may be started in response to a request for heating the vehicle cabin or for elevating the temperature of the battery 27. In a case where the water flow is started, the cold engine coolant that has been stagnant in the first temperature raising water passage 16 and the second temperature raising water passage 17 until then flows into the water jacket 11. As a result, a water temperature drop in which the outlet water temperature THW1 temporarily decreases may occur. In a case where the water temperature drop occurs, the correspondence relationship between the outlet water temperature THW1 and the wall surface temperature of the combustion chamber temporarily breaks down. As a result, the engine operation amount adjusted based on the outlet water temperature THW1 may deviate from the appropriate value corresponding to the wall surface temperature of the combustion chamber, and the combustion state of the engine 10 may deteriorate. On the other hand, in the case of the engine control device according to the present embodiment, by switching the map used for the calculation of the engine operation amount between the occurrence of the water temperature drop and the normal time, the deterioration of the combustion state due to the water temperature drop is suppressed.

FIG. 5 shows an example of a control aspect of the engine control device according to the present embodiment. (A) in FIG. 5 shows a transition of the open or closed state of the temperature raising water passage, and (B) in FIG. 5 shows a transition of the outlet water temperature THW1 and the heater inlet water temperature THW2. In addition, (C) in FIG. 5 shows a transition of the warm-up time incremental correction coefficient for the fuel injection amount, and (D) in FIG. 5 shows a transition of the target EGR rate. The state in which the temperature raising water passage is opened here refers to a state in which the engine coolant flowing out of the water jacket 11 flows into at least one of the first temperature raising water passage 16 and the second temperature raising water passage 17 through the switching valve 18. In addition, the state in which the temperature raising water passage is closed here refers to a state in which the flow of the engine coolant that flows out of the water jacket 11 to both the first temperature raising water passage 16 and the second temperature raising water passage 17 is stopped by the switching valve 18.

In a case of FIG. 5, the temperature raising water passage is closed before time t1. The engine coolant that circulates through the water jacket 11 is also heated by receiving heat from the engine 10 in the period before time t1. Therefore, the outlet water temperature THW1 increases with the passage of time. On the other hand, in the period before time t1, since the engine coolant does not flow into the first temperature raising water passage 16 and the second temperature raising water passage 17, the heater inlet water temperature THW2 remains unchanged at a low temperature.

In a case where the temperature raising water passage is started to be supplied with water at time t1, the cold engine coolant that has been stagnant in the temperature raising water passage until then flows into the water jacket 11. Therefore, after the start of the water passage, a water temperature drop in which the outlet water temperature THW1 temporarily decreases occurs. Since the cold engine coolant remains in the temperature raising water passage immediately after the start of the water passage, the difference (water temperature difference ΔT) between the outlet water temperature THW1 and the heater inlet water temperature THW2 is large.

In (C) and (D) of FIG. 5, a transition of the warm-up time incremental correction coefficient and the target EGR rate in a case where the calculation using the normal time map is continued after time t1 is indicated by a broken line. The warm-up time incremental correction coefficient and the target EGR rate in this case change in accordance with the decrease in the outlet water temperature THW1 due to the water temperature drop. Therefore, the fuel injection amount and the recirculation amount of the exhaust gas may be inappropriate values that do not correspond to the wall surface temperature of the combustion chamber, and the combustion state may deteriorate.

On the other hand, in a case where the flow of the engine coolant through the temperature raising water passage is started by the switching valve 18 and the water temperature difference ΔT is equal to or higher than the transition determination value, the calculation processing device 33 switches the map used for the calculation of the engine operation amount from the normal time map to the transition time map. The normal time map and the transition time map are configured such that the outlet water temperature THW1 in a case of outputting the same value is a lower temperature in the transition time map than in the normal time map. Therefore, the change in the fuel injection amount and the recirculation amount of the exhaust gas due to the decrease in the outlet water temperature THW1 due to the water temperature drop is suppressed.

In a case where the temperature raising water passage is started to be supplied with water, the engine coolant that has been heated by passing through the water jacket 11 and receiving heat from the engine 10 flows into the temperature raising water passage, so that the heater inlet water temperature THW2 starts to rise. Then, after a certain period of time has elapsed from the start of the water supply, the engine coolant that flows from the temperature raising water passage into the water jacket 11 is replaced with the engine coolant heated by the engine 10, so that the outlet water temperature THW1 starts to rise again. Therefore, in a case where the water temperature drop ends, the difference (water temperature difference ΔT) between the outlet water temperature THW1 and the heater inlet water temperature THW2 is reduced. In a case where the water temperature difference ΔT is reduced to less than the transition determination value at time t2, the calculation processing device 33 determines that the water temperature drop has ended, and switches the map used for the calculation of the engine operation amount from the transition time map to the normal time map.

Effect of Embodiment

The engine control device of the present embodiment configured as described above has the following effects. (1) The calculation processing device 33 determines a period until the difference between the heater inlet water temperature THW2 and the outlet water temperature THW1 after the start of the water supply to the temperature raising water passage by the switching valve 18 is reduced to less than the predetermined value as the transition period in which the water temperature drop occurs. Therefore, the period in which the water temperature drop occurs can be accurately determined.

(2) The calculation processing device 33 calculates the engine operation amount by using the transition time map in the transition period and by using the normal time map in a period other than the transition period. The normal time map and the transition time map are maps that receive the outlet water temperature THW1 as an input and output values such as a warm-up time incremental correction coefficient, a target EGR rate, and a warm-up advance angle correction amount used for the calculation of the engine operation amount, and are stored in the storage device 34. The normal time map and the transition time map are configured such that the outlet water temperature THW1 in a case of outputting the same value is a lower temperature in the transition time map than in the normal time map. By switching such maps, the reflection of the decrease in the outlet water temperature THW1 due to the water temperature drop on the engine operation amount is relaxed. Therefore, the engine control device of the present embodiment has an effect of suppressing deterioration of the combustion state due to the water temperature drop.

Other Embodiments

The embodiment described above can be modified and carried out as follows. The embodiment described above and the following modifications can be carried out in combination within a technically consistent range.

In a case where the calculation is performed by using the value calculated by using the normal time map or the transition time map, the calculation aspect of the fuel injection amount, the EGR opening degree, and the ignition timing in the above-described embodiment may be appropriately changed.

In a case where the engine operation amount is calculated based on the outlet water temperature THW1, the same calculation aspect of the engine operation amount as that of the above-described embodiment may be applied to the engine operation amount other than the fuel injection amount, the EGR opening degree, and the ignition timing. The engine operation amount to which such a calculation aspect is applied is relaxed from an inappropriate change in the value due to the water temperature drop.

The cooling system of the engine 10 according to the above-described embodiment includes the first temperature raising water passage 16 provided with the heater core 23 and the second temperature raising water passage 17 provided with the water-to-water heat exchanger 26 as the temperature raising water passages provided with the temperature raising heat exchanger. The cooling system of the engine 10 may be configured to include only one of the first temperature raising water passage 16 or the second temperature raising water passage 17 as the temperature raising water passage. In addition, the engine cooling device may have a configuration in which a water passage in which a heat exchanger different from the heater core 23 and the water-to-water heat exchanger 26 is provided is used as a temperature raising water passage in a case where the temperature raising heat exchanger for increasing the temperature of another fluid with the heat of the engine coolant is used.

In the above-described embodiment, the temperature (heater inlet water temperature) of the engine coolant flowing out of the temperature raising heat exchanger is detected in a portion on a downstream side of the heater water pump 24 and on an upstream side of the electric heater 25 in the first temperature raising water passage 16 and the second temperature raising water passage 17. The detection position of the temperature may be appropriately changed. For example, the temperature of the engine coolant near the inlet 12 of the water jacket 11 may be detected as the temperature of the engine coolant flowing out from the temperature raising heat exchanger.

A mechanical pump that operates by receiving the power of the engine 10 may be adopted as the engine water pump 20.

The engine control device of the embodiment may be applied to a normal engine vehicle that is not the hybrid electric vehicle.

Supplementary Notes

Appendix 1

An engine control device that controls an engine provided with a cooling system in which a radiator water passage through a radiator, a temperature raising water passage in which a temperature raising heat exchanger for heating another fluid with heat of the engine coolant is provided, and a bypass water passage that allows the engine coolant to flow by bypassing the radiator and the temperature raising heat exchanger are provided in parallel as flow paths of the engine coolant that flows out from an outlet of a water jacket and returns to an inlet of the water jacket, the cooling system further provided with a thermostat that opens and closes the radiator water passage and a switching valve that switches between a state in which the engine coolant is allowed to flow from the temperature raising water passage to the water jacket and a state in which the flow of the engine coolant from the temperature raising water passage to the water jacket is prohibited, the engine control device including: a calculation processing device; and a storage device, in which the storage device stores a normal time map and a transition time map as a map that takes, as an input, an outlet water temperature that is a temperature of the engine coolant flowing out from the water jacket and outputs a value used for calculating an engine operation amount, and the calculation processing device is configured to calculate the engine operation amount using the transition time map during a transition period from a state in which the flow of the engine coolant from the temperature raising water passage to the water jacket is prohibited to a state in which the flow of the engine coolant from the temperature raising water passage to the water jacket is allowed by the switching valve, until a difference between the temperature of the engine coolant flowing out from the temperature raising heat exchanger and the outlet water temperature is reduced to less than a predetermined value, and to calculate the engine operation amount using the normal time map in a period other than the transition period, and the normal time map and the transition time map are configured such that, in a case where the same value is output, an outlet water temperature in the transition time map is lower than an outlet water temperature in the normal time map.

Appendix 2

The engine control device according to Appendix 1, in which the engine operation amount is any of a fuel injection amount, an ignition timing, or an opening degree of an exhaust gas recirculation valve.

Appendix 3

The engine control device according to Appendix 1 or 2, in which the temperature raising heat exchanger is a heater core that performs heat exchange between air blown into a vehicle cabin and the engine coolant.

Appendix 4

The engine control device according to Appendix 1 or 2, in which the temperature raising heat exchanger is a water-to-water heat exchanger that performs heat exchange between battery coolant used for adjusting a temperature of a battery and the engine coolant.

Claims

1. An engine control device that controls an engine in which, as flow paths for an engine coolant that returns from an outlet of a water jacket to an inlet of the water jacket, a radiator water passage provided through a radiator, a temperature raising water passage provided with a temperature raising heat exchanger for raising a temperature of another fluid with heat of the engine coolant, and a bypass water passage through which the engine coolant flows while the engine coolant bypasses the radiator and the temperature raising heat exchanger are provided in parallel, and a thermostat configured to open and close the radiator water passage and a switching valve configured to switch between a state in which flow of the engine coolant from the temperature raising water passage into the water jacket is not allowed and a state in which the flow of the engine coolant from the temperature raising water passage into the water jacket is allowed are provided in a cooling system, the engine control device comprising:

a calculation processing device; and

a storage device, wherein: the storage device is configured to store a normal time map and a transition time map as maps that use, as input, an outlet water temperature that is a temperature of the engine coolant flowing out of the water jacket and output a value that is used for calculating an engine operation amount; the calculation processing device is configured to calculate, during a transition period that is a period until a difference between a temperature of the engine coolant flowing out of the temperature raising heat exchanger and the outlet water temperature decreases below a predetermined value after the switching valve switches from the state in which the flow of the engine coolant from the temperature raising water passage into the water jacket is not allowed to the state in which the flow of the engine coolant from the temperature raising water passage into the water jacket is allowed, the engine operation amount using the transition time map, and calculate, during a period other than the transition period, the engine operation amount using the normal time map; and the normal time map and the transition time map are configured such that the outlet water temperature when the normal time map and the transition time map output the same value is lower on the transition time map than on the normal time map.

2. The engine control device according to claim 1, wherein the engine operation amount is any of a fuel injection amount, an ignition timing, and an opening degree of an exhaust gas recirculation valve.

3. The engine control device according to claim 1, wherein the temperature raising heat exchanger is a heater core configured to exchange heat between air blown into a vehicle cabin and the engine coolant.

4. The engine control device according to claim 1, wherein the temperature raising heat exchanger is a water-to-water heat exchanger configured to exchange heat between a battery coolant that is used for adjusting a temperature of a battery and the engine coolant.