Engine control unit

Abstract

To improve the accuracy in estimating a catalyst temperature at the time of starting an engine.SOLUTION: A CPU 17 of an engine control device 16 performs the following determination processing and estimation processing at the time of starting the engine 13. The determination processing is the processing for determining whether an engine hood 12 is opened or closed while the engine 13 is stopped, on the basis of an intake air temperature and a soak time at the time of starting the engine 13. The estimation processing is the processing for estimating a catalyst temperature at the time of starting the engine 13, on the basis of a catalyst temperature and a soak time when the engine 13 is stopped. In the estimation processing, when the CPU 17 determines in the determination processing that the engine hood 12 is opened, it estimates, as the catalyst temperature at the time of starting the engine 13, a lower temperature than that when it determines that the engine hood is closed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an engine control device. [Background technology]

[0002] Some vehicle engine control devices estimate the temperature of a catalytic converter installed in the exhaust passage based on the engine's operating state. Temperature estimation based on the operating state is not possible while the engine is stopped. However, the temperature of the catalytic converter gradually decreases over time while the engine is stopped. Therefore, the temperature of the catalytic converter at engine start can be estimated as a function of the estimated temperature of the catalytic converter when the engine is stopped and the time the engine is stopped. In the following explanation, the temperature of the catalytic converter will be referred to as the catalyst temperature, and the time the engine is stopped will be referred to as the engine soak time. The catalyst temperature when the engine is stopped will be referred to as the stop catalyst temperature, and the catalyst temperature when the engine is started will be referred to as the start catalyst temperature.

[0003] Patent Document 1 describes a technique for estimating the engine soak time based on the motor temperature and the transmission oil temperature. Some engine control devices also have a built-in timer that measures the soak time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-044432 Summary of the Invention [Problem to be solved by the invention]

[0005] Vehicles are sometimes parked with the engine hood open for inspection, maintenance, etc. When the engine hood is open, the amount of heat dissipated from the engine compartment to the outside air is greater, so the catalyst temperature drops more quickly while the engine is stopped than when the engine hood is closed. Therefore, if the engine is stopped with the engine hood open, the catalyst temperature at startup cannot be accurately estimated from the soak time and catalyst temperature at shutdown. [Means for solving the problem]

[0006] An engine control device that solves the above problem is a device that controls an engine installed in an engine compartment of a vehicle. A temperature sensor is installed in the engine compartment of the vehicle, and a catalyst is installed in the exhaust passage of the engine. The engine control device also includes a soak timer that measures a soak time, which is the time from when the engine is stopped to when the engine is started. The engine control device performs the following determination process and estimation process when the engine is started. The determination process determines whether the engine hood was open or closed while the engine was stopped based on the soak time and a detection value of the temperature sensor at the time of engine start. The estimation process estimates the catalyst temperature at the time of engine start based on the soak time and the catalyst temperature at the time of engine stop. If the determination process determines that the engine hood was open, the estimation process estimates a lower temperature as the catalyst temperature at the time of engine start than if the engine hood was closed.

[0007] If the engine hood is open, the temperature in the engine compartment drops more quickly after the engine is stopped than if it is closed. Therefore, based on the temperature detected by a temperature sensor installed in the engine compartment at engine start and the soak time, it is possible to determine whether the engine hood was open or closed while the engine was stopped. Furthermore, if the engine hood is open, the catalyst temperature also drops more quickly after the engine is stopped than if it is closed. In contrast, if the engine control device determines that the engine hood is open, it estimates a lower temperature as the catalyst temperature at engine start than if it determines that the engine hood is closed. Therefore, the engine control device can accurately estimate the catalyst temperature at engine start regardless of whether the engine hood is open or closed. Therefore, the engine control device has the effect of improving the accuracy of estimating the catalyst temperature at engine start. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of an embodiment of an engine control device; [Figure 2] 2 is a flowchart of a catalyst temperature increase control routine executed by the engine control device of FIG. [Figure 3] 2 is a flowchart of a routine for estimating a catalyst temperature at startup executed by the engine control device of FIG. 1. [Figure 4] 10 is a graph showing the relationship between soak time and an open / close determination value. [Figure 5] 10 is a graph showing the relationship between the soak time and the convergence rate in the first map and the second map. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of an engine control device will be described in detail below with reference to FIGS. <Configuration of engine control unit> First, the configuration of the engine control device of this embodiment will be described with reference to Figure 1. A vehicle 10 shown in Figure 1 has an engine compartment 11, which is a space for accommodating an engine 13. The engine compartment 11 is covered from above by an engine hood 12, which is a hinged cover. An intake air temperature sensor 14 is installed in an intake passage 13A of the engine 13, and detects an intake air temperature THA, which is the temperature of the intake air flowing therethrough. An electrically heated catalyst 15 is also installed in an exhaust passage 13B of the engine 13. The electrically heated catalyst 15 is an exhaust purification device equipped with a heater that generates heat in response to the passage of electricity.

[0010] The engine control device 16 of this embodiment is mounted on such a vehicle 10. The engine control device 16 is an electronic control unit for engine control. The engine control device 16 is activated in response to an ignition switch being turned on by the driver of the vehicle 10. The engine control device 16 also stops activation in response to an ignition switch being turned off.

[0011] The engine control device 16 includes a CPU 17 and a memory 18. The CPU 17 is a processing device that executes various processes for engine control. The memory 18 is a storage device that stores programs and data for engine control. Detection signals from various sensors provided in the engine 13 are input to the engine control device 16. The detection signals input to the engine control device 16 include a detection signal from the intake air temperature sensor 14. The engine control device 16 controls the intake air amount, fuel injection amount, ignition timing, etc. of the engine 13 based on the detection signals from these sensors. The engine control device 16 also controls the power supply to the heater of the electrically heated catalyst 15. The engine 13 is controlled by the CPU 17 reading and executing programs from the memory 18.

[0012] Furthermore, the engine control device 16 is provided with a soak timer 19. The soak timer 19 continues to operate even while the engine control device 16 is being started or stopped. The soak timer 19 measures a soak time ST, which is a time during which the engine 13 is stopped.

[0013] <Catalyst temperature rise control> As part of engine control, the engine control device 16 performs catalyst temperature rise control to promote warm-up of the electrically heated catalyst 15. Figure 2 shows a flowchart of a catalyst temperature rise control routine executed by the CPU 17 for the catalyst temperature rise control. The CPU 17 repeatedly executes this routine at predetermined control intervals while the engine 13 is running. In the following description, the temperature of the electrically heated catalyst 15 will be referred to as the catalyst temperature.

[0014] When this routine starts, the CPU 17 first calculates the temperature rise ΔT in step S100. The temperature rise ΔT represents the amount of change in catalyst temperature from the previous control cycle to the current control cycle. The CPU 17 calculates the temperature rise ΔT by estimation based on the operating state of the engine 13. Specifically, the CPU 17 calculates the temperature rise ΔT based on a model of the heat balance between the electrically heated catalyst 15 and the exhaust gas and the outside air. The operating state of the engine 13 used to calculate the temperature rise ΔT includes, for example, the engine speed, engine load factor, and engine water temperature.

[0015] Next, in step S110, the CPU 17 updates the value of the estimated catalyst temperature THC, which is an estimate of the catalyst temperature, in accordance with the temperature rise ΔT calculated in step S100. Specifically, the CPU 17 updates the value of the estimated catalyst temperature THC so that the updated value is the value obtained by adding the temperature rise ΔT to the value before the update.

[0016] Next, in step S120, the CPU 17 determines whether the estimated catalyst temperature THC is less than a determination value X1. The determination value X1 is set to the catalyst temperature when the warm-up of the electrically heated catalyst 15 is complete. If the estimated catalyst temperature THC is less than the determination value X1 (YES), the CPU 17 energizes the heater of the electrically heated catalyst 15 in step S130. On the other hand, if the estimated catalyst temperature THC is equal to or greater than the determination value X1 (NO), the CPU 17 stops energizing the heater of the electrically heated catalyst 15 in step S140. After processing step S130 or step S140, the CPU 17 ends the processing of this routine for the current control cycle.

[0017] <Estimation of catalyst temperature THC0 at start-up> Meanwhile, the CPU 17 estimates a start-up catalyst temperature THC0, which is an estimated catalyst temperature THC at engine start-up, when the engine control device 16 is started up. Next, the estimation of the start-up catalyst temperature THC0 will be described in detail.

[0018] 3 shows a flowchart of a routine for estimating the catalyst temperature THC0 at startup. The CPU 17 executes this routine when the engine control device 16 is started up. When this routine starts, the CPU 17 first acquires the stop catalyst temperature THCS in step S200. The stop catalyst temperature THCS is the value of the estimated catalyst temperature THC when the engine 13 was last stopped. When the engine 13 was stopped, the CPU 17 recorded the value of the estimated catalyst temperature THC at that time in the memory 18 as the value of the stop catalyst temperature THCS. Then, in the next step S210, the CPU 17 acquires the soak time ST measured by the soak timer 19. Then, in the following step S220, the CPU 17 acquires the current intake air temperature THA.

[0019] Next, in step S230, the CPU 17 calculates an opening / closing determination value X2 based on the soak time ST. Then, in the next step S240, the CPU 17 determines whether the intake air temperature THA is equal to or lower than the opening / closing determination value X2.

[0020] FIG. 4 shows the relationship between the open / close determination value X2 and the soak time ST. FIG. 4 also shows the relationship between the intake air temperature THA and the soak time ST when the engine hood 12 is closed and when it is open. When the engine 13 is running, intake air flows through the intake passage 13A, so the intake air temperature THA is close to the outside air temperature. When the engine 13 is stopped, the intake air stagnates in the intake passage 13A, and residual heat from the engine 13 is transferred to the intake air. Therefore, the intake air temperature THA rises immediately after the engine 13 is stopped. Thereafter, the intake air temperature THA decreases as the engine 13 cools, eventually converging to a temperature equal to the outside air temperature. When the engine hood 12 is open, the engine compartment 11 is exposed to the outside, so the intake air temperature THA decreases more quickly after the engine is stopped than when the engine hood 12 is closed. The open / close determination value X2 for each soak time ST is set to be higher than the intake air temperature THA when the engine hood 12 is open and lower than the intake air temperature THA when the engine hood 12 is closed. Therefore, if the intake air temperature THA at the time of engine start is equal to or lower than the open / close determination value X2, it can be determined that the engine 13 was stopped with the engine hood 12 open.

[0021] 3, if the CPU 17 determines that the intake air temperature THA is equal to or lower than the opening / closing determination value X2 (YES), the process proceeds to step S250. If the CPU 17 determines that the intake air temperature THA is not higher than the opening / closing determination value X2 (NO), the process proceeds to step S260. In step S250, the CPU 17 calculates a convergence rate K using a first map MAP1 pre-stored in the memory 18. In addition, in step S260, the CPU 17 calculates the convergence rate K using a second map MAP2 similarly pre-stored in the memory 18. In both steps S250 and S260, the CPU 17 calculates a value greater than 0 and equal to or lower than 1 as the value of the convergence rate K.

[0022] After calculating the convergence rate K in step S250 or step S260, the CPU 17 proceeds to step S270. In step S270, the CPU 17 calculates a value that satisfies the relationship of equation (1) as the value of the start-time catalyst temperature THC0. That is, when the value of the convergence rate K is "0," the CPU 17 calculates a value equal to the stop-time catalyst temperature THCS as the value of the start-time catalyst temperature THC0. When the value of the convergence rate K is "1," the CPU 17 calculates a value equal to the intake air temperature THA as the value of the start-time catalyst temperature THC0. The CPU 17 calculates the value of the start-time catalyst temperature THC0 so that the value changes from the value equal to the stop-time catalyst temperature THCS to the value equal to the intake air temperature THA as the value of the convergence rate K changes from "0" to "1." Note that the CPU 17 ends the processing of this routine after calculating the start-time catalyst temperature THC0.

[0023]

number

[0024] FIG. 5 shows the relationship between the soak time ST and the convergence rate K for each of the first map MAP1 and the second map MAP2. In both the first map MAP1 and the second map MAP2, when the soak time ST is "0," the value of the convergence rate K is "0." In both the first map MAP1 and the second map MAP2, the value of the convergence rate K eventually converges to "1" as the soak time ST increases. However, in the case of the first map MAP1, the value of the convergence rate K converges to "1" more quickly than in the case of the second map MAP2. In the relationship of equation (1), the closer the convergence rate K is to "1," the closer the startup catalyst temperature THC0 is to the intake air temperature THA, i.e., the lower the temperature becomes. Therefore, when the convergence rate K is calculated using the first map MAP1, the value of the startup catalyst temperature THC0 calculated in step S270 will be lower than when the convergence rate K is calculated using the second map MAP2.

[0025] <Effects of the embodiment> When the engine 13 is started, the CPU 17 performs a determination process to determine whether the engine hood 12 was open or closed while the engine 13 was stopped, based on the intake air temperature THA and the soak time ST at the time of engine start (FIG. 3: S230, S240). If the engine hood 12 is open, the intake air temperature THA decreases faster while the engine 13 is stopped than if the engine hood 12 is closed. Therefore, based on the intake air temperature THA at the time of engine start and the soak time ST, it is possible to determine whether the engine hood 12 was open or closed while the engine 13 was stopped.

[0026] Furthermore, when the engine 13 is started, the CPU 17 performs an estimation process to estimate the start-up catalyst temperature THC0 based on the stop-up catalyst temperature THCS and the soak time ST. When the engine 13 is stopped, the catalyst temperature gradually decreases over time from the temperature at the time of stop and eventually converges to a temperature close to the outside air temperature. However, if the engine hood 12 is open while the engine 13 is stopped, the catalyst temperature decreases more quickly than if the engine hood 12 is closed. In response to this, the CPU 17 reflects the results of the determination process in estimating the start-up catalyst temperature THC0 in the estimation process. Specifically, during the estimation process, if the CPU 17 determines that the engine hood 12 is open, the CPU 17 estimates a lower temperature as the start-up catalyst temperature THC0 than if it determines that the engine hood 12 is closed. Therefore, the start-up catalyst temperature THC0 can be accurately estimated regardless of whether the engine hood 12 is open or closed.

[0027] Furthermore, while the engine 13 is operating, the CPU 17 estimates the catalyst temperature by repeatedly calculating the temperature rise ΔT based on the operating state of the engine 13 and updating the estimated catalyst temperature THC in accordance with the temperature rise ΔT. The temperature rise ΔT represents the amount of change in the catalyst temperature. The CPU 17 uses the start-up catalyst temperature THC0 estimated in the estimation process as the value of the estimated catalyst temperature THC at the start of the engine 13. This allows for accurate estimation of the catalyst temperature while the engine 13 is operating.

[0028] The CPU 17 then performs catalyst temperature increase control based on the estimated catalyst temperature THC. Specifically, the CPU 17 energizes the heater based on the estimated catalyst temperature THC until warm-up of the electrically heated catalyst 15 is complete. As described above, the CPU 17 accurately estimates the start-up catalyst temperature THC0 through estimation processing. The CPU 17 then reflects the start-up catalyst temperature THC0 in estimating the catalyst temperature while the engine 13 is running. This allows the catalyst temperature increase control to be performed in an appropriate manner that corresponds to the actual progress of warm-up of the electrically heated catalyst 15.

[0029] According to the engine control device 16 of the present embodiment described above, the following effects can be achieved. (1) The CPU 17 of the engine control device 16 performs the following determination process and estimation process when the engine 13 is started. The determination process is a process for determining whether the engine hood 12 was open or closed while the engine 13 was stopped, based on the intake air temperature THA and the soak time ST when the engine 13 was started. The estimation process is a process for estimating the start-up catalyst temperature THC0 based on the stop-up catalyst temperature THCS and the soak time ST. Therefore, the catalyst temperature at the start of the engine 13 can be accurately estimated regardless of whether the engine hood 12 was open or closed while the engine 13 was stopped.

[0030] (2) The CPU 17 of the engine control device 16 estimates the catalyst temperature by repeatedly calculating the amount of change in the catalyst temperature based on the operating state of the engine 13 and updating the estimated value of the catalyst temperature according to the amount of change while the engine 13 is operating. When estimating the catalyst temperature, the CPU 17 uses the start-up catalyst temperature THC0 estimated in the estimation process as the estimated value of the catalyst temperature at the start of the engine 13. This allows the catalyst temperature while the engine 13 is operating to be estimated with high accuracy.

[0031] (3) Based on the above-described catalyst temperature estimation results, the CPU 17 of the engine control device 16 performs catalyst temperature rise control to promote the temperature rise of the electrically heated catalyst 15. Therefore, catalyst temperature rise control can be performed in an appropriate manner corresponding to the progress of the actual warm-up of the electrically heated catalyst 15.

[0032] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0033] When the difference between the catalyst temperature after warm-up and the outside air temperature is sufficiently larger than the amount of change in the outside air temperature in the environment in which the vehicle 10 is used, the catalyst temperature at startup THC0 can be estimated with high accuracy even if the outside air temperature is considered to be a constant temperature. Therefore, the catalyst temperature at startup THC0 may be calculated in step S270 of FIG. 3 without using the detected value of the intake air temperature THA.

[0034] The determination in step S240 of FIG. 3 may be performed using the detected value of another temperature sensor installed in the engine compartment 11 instead of the intake air temperature THA. Examples of other temperature sensors installed in the engine compartment 11 include a water temperature sensor that detects the temperature of the coolant for the engine 13 and other on-board equipment, and an oil temperature sensor that detects the temperature of oil used to lubricate the engine 13 and operate the transmission. Furthermore, if the vehicle 10 is a hybrid vehicle, a sensor that detects the temperature of an inverter or a sensor that detects the temperature of a motor may be installed. In such a hybrid vehicle, these sensors may be used instead of the intake air temperature sensor 14.

[0035] Instead of the electrically heated catalyst 15, a catalyst without a heater may be used. The catalyst temperature increase control may be performed by a method other than energizing the heater. For example, the catalyst temperature increase control may be performed by increasing the amount of fuel injected into the engine 13, retarding the ignition timing, making the air-fuel ratio leaner, etc. [Explanation of symbols]

[0036] 10...vehicle, 11...engine compartment, 12...engine hood, 13...engine, 13A...intake passage, 13B...exhaust passage, 14...intake air temperature sensor, 15...electrically heated catalyst, 16...engine control device, 17...CPU, 18...memory, 19...soak timer

Claims

1. An engine control device that controls an engine installed in an engine room of a vehicle, A temperature sensor is installed in the engine compartment, A catalyst is installed in the exhaust passage of the engine, the engine control device is provided with a soak timer that measures a soak time, which is a time from when the engine is stopped to when the engine is started, The engine control device performs a determination process and an estimation process when the engine is started, the determination process is a process of determining whether an engine hood was open or closed while the engine was stopped based on the soak time and a detection value of the temperature sensor at the time of starting the engine, The estimation process is a process for estimating the catalyst temperature at the time of starting the engine based on the soak time and the catalyst temperature at the time of stopping the engine, and when it is determined in the determination process that the engine hood is open, a temperature lower than that when it is determined that the engine hood is closed is estimated as the catalyst temperature at the time of starting the engine. Engine control device.

2. 2. The engine control device according to claim 1, wherein the temperature sensor is an intake air temperature sensor that detects an intake air temperature of the engine.

3. 2. The engine control device according to claim 1, wherein the catalyst temperature is estimated by repeatedly calculating the amount of change in the catalyst temperature based on the operating state of the engine while the engine is running and updating the estimated value of the catalyst temperature in accordance with the amount of change.

4. 2. The engine control device according to claim 1, wherein catalyst temperature increase control is performed to promote a temperature increase of the catalyst based on the result of the catalyst temperature estimation.

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