Engine control device

Abstract

The present invention addresses the problem of suppressing emission deterioration in a range in which insufficient driving force of a vehicle does not occur. An electronic control unit, which is used in an engine mounted on a vehicle and provided with an exhaust purification catalyst in an exhaust passage, controls an engine output such that the engine output becomes equal to or less than an output limit value until warming of the exhaust purification catalyst is completed, and controls the engine output until warming of the exhaust purification catalyst is completed. When the output limit control is executed, an estimated vehicle speed, which is an estimated value of the vehicle speed when the traveling resistance is assumed to be a predetermined magnitude, is calculated on the basis of the engine output, and when the actual vehicle speed is lower than the estimated vehicle speed and the deviation between the actual vehicle speed and the estimated vehicle speed is large, the output limit value is set to a value larger than that not in this case.

Description

Technical Field

[0001] This invention relates to an engine control device. Background Technology

[0002] The engine control device described in Patent Document 1 is configured to suppress emissions deterioration by limiting engine output during the period until the exhaust purification catalyst installed in the exhaust passage has finished warming up.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2021-146789 Summary of the Invention

[0004] If the above output limit is applied to the engine installed in the vehicle, the vehicle's driving force may be insufficient under the output limit when the vehicle is heavily loaded or climbing a hill.

[0005] The engine control device for solving the above-mentioned problems is applicable to engines installed in vehicles and equipped with exhaust purification catalysts in the exhaust passage. The engine control device is configured to perform the following processing: based on the engine output, calculate an estimated vehicle speed assuming a predetermined driving resistance; if the actual vehicle speed is lower than the estimated vehicle speed and the deviation between the actual vehicle speed and the estimated vehicle speed is large, set an output limit value to a value larger than that in other cases; and control the engine output until the exhaust purification catalyst has warmed up completely, so that the engine output is below the output limit value.

[0006] Another engine control device for solving the above-mentioned problem is applicable to an engine installed in a vehicle and having an exhaust purification catalyst in the exhaust passage. The engine control device is configured to perform the following processing: based on the engine output, calculate an estimated value of the vehicle's acceleration, i.e., an estimated acceleration, assuming a predetermined driving resistance; if the actual acceleration of the vehicle is lower than the estimated acceleration and the deviation between the actual acceleration and the estimated acceleration is large, set an output limit value to a value larger than that in other cases; and control the engine output until the exhaust purification catalyst has warmed up completely, so that the engine output is below the output limit value.

[0007] Invention Effects

[0008] The aforementioned engine control device has the effect of suppressing emissions degradation within a range that does not cause insufficient driving force of the vehicle. Attached Figure Description

[0009] Figure 1 This is a diagram schematically showing the structure of the engine control device according to the first embodiment.

[0010] Figure 2 yes Figure 1 The flowchart shows the routine procedure for setting output limit values ​​performed by the engine control unit.

[0011] Figure 3 It is applicable Figure 1 The timing diagram of the engine cold start of the engine control unit, (a) represents the shift of cumulative air volume M, (b) represents the shift of engine output Pe, (c) represents the shift of actual vehicle speed Vt and estimated vehicle speed Ve, and (d) represents the shift of deviation rate.

[0012] Figure 4 This is a flowchart of the output limit value setting routine performed by the engine control device of the second embodiment. Detailed Implementation

[0013] (First Embodiment)

[0014] The first embodiment of the engine control device will now be described.

[0015] <Structure of Engine Control Unit>

[0016] First, refer to Figure 1 The structure of the engine control device of this embodiment will be described. The engine 10 to which the control device of this embodiment is applicable is mounted in vehicle 1.

[0017] The engine 10 includes a combustion chamber 11 for burning a mixture of air and gas, an intake passage 12 for introducing air into the combustion chamber 11, and an exhaust passage 13 for discharging exhaust gas from the combustion chamber 11. An air flow meter 14 for detecting the intake air volume Ga and a throttle valve 15 for adjusting the intake air volume Ga are installed in the intake passage 12. Furthermore, the engine 10 includes a fuel injector 16 for injecting fuel and an ignition device 17 for igniting the mixture in the combustion chamber 11 via spark discharge. Moreover, an exhaust purification catalyst 18 for purifying the exhaust gas generated by combustion in the combustion chamber 11 is installed in the exhaust passage 13 of the engine 10.

[0018] The vehicle 1 is equipped with an electronic control unit 20, which serves as an engine control device for controlling the engine 10. The electronic control unit 20 includes a processing circuit 21 that performs various processes for engine control and a storage device 22 that stores programs and data for engine control. The electronic control unit 20 receives input from various sensors installed in the vehicle 1, including the engine 10. In addition to the air intake Ga measured by the airflow meter 14, the sensor results input to the electronic control unit 20 include engine coolant temperature Thw, crankshaft angle θc, throttle opening Acc, and actual vehicle speed Vt. Engine coolant temperature Thw represents the temperature of the engine 10's coolant, and crankshaft angle θc represents the rotation angle of the crankshaft, which serves as the output shaft of the engine 10. Throttle opening Acc represents the amount of throttle pedal operation by the driver, and actual vehicle speed Vt represents the vehicle 1's speed. The electronic control unit 20 determines the operating amount of the engine 10 based on these results and controls the engine 10 by operating the actuators of the engine 10 according to the determined operating amount. Examples of the operating parameters of the engine 10 include the opening degree of the throttle valve 15, the fuel injection quantity of the injector 16, and the ignition timing of the air-fuel mixture based on the ignition device 17.

[0019] <Output Limitation Control During Cold Start>

[0020] During a cold start of the engine 10, the electronic control unit 20 performs output limiting control to keep the engine output Pe below the output limit value LM until the exhaust gas purification catalyst 18 has warmed up. In this embodiment, the electronic control unit 20 determines whether the start is a cold start or a warm start based on the engine coolant temperature Thw at the time of engine start. If it is determined to be a cold start, the electronic control unit 20 begins output limiting control. The electronic control unit 20 continues to output limiting control until the exhaust gas purification catalyst 18 has warmed up. In this embodiment, the electronic control unit 20 determines that the exhaust gas purification catalyst 18 has warmed up when the cumulative air volume M reaches or exceeds a preset warm-up determination value Mx. The cumulative air volume M represents the total amount of combustion air supplied to the combustion chamber 11 after the engine 10 starts. The electronic control unit 20 calculates the cumulative air volume M by accumulating the detected value of the intake air volume Ga based on the air flow meter 14.

[0021] Figure 2 The diagram shows a flowchart of the output limit setting routine executed by the electronic control unit 20, which sets the output limit value LM in output limit control. During output limit control, the electronic control unit 20 repeatedly executes this routine according to a predetermined control cycle.

[0022] If the electronic control unit 20 starts this routine procedure, it first acquires the cumulative air volume M, engine output Pe, and actual vehicle speed Vt in step S100. Additionally, the electronic control unit 20 calculates the engine speed Ne based on the detected crankshaft angle θc, and determines the engine output Pe based on the engine speed Ne and the intake air volume Ga.

[0023] Next, in step S120, the electronic control unit 20 sets the standard output limit value LM0 based on the cumulative air volume M. As the cumulative air volume M approaches the warm-up determination value Mx, the electronic control unit 20 sets the standard output limit value LM0 to increase its value.

[0024] In the subsequent step S130, the electronic control unit 20 calculates the estimated vehicle speed Ve based on the engine output Pe. The estimated vehicle speed Ve represents an estimate of the vehicle speed under the assumption of a fixed driving resistance, assuming the vehicle is traveling at the current engine output Pe. The storage device 22 of the electronic control unit 20 stores a mapping representing the relationship between the engine output Pe, obtained through experiments, etc., and the estimated vehicle speed Ve. The electronic control unit 20 refers to this mapping to calculate the estimated vehicle speed Ve.

[0025] The state where the driving resistance is a predetermined value here indicates that the load weight of vehicle 1 is a predetermined weight and vehicle 1 is driving stably on flat ground. In this embodiment, for example, a weight slightly heavier than the weight of the occupants of the maximum occupancy capacity of vehicle 1 is taken as the predetermined weight.

[0026] In the next step S140, the electronic control unit 20 divides the actual vehicle speed Vt by the estimated vehicle speed Ve, and calculates the value of this division as the deviation rate. Then, in the subsequent step S150, the electronic control unit 20 determines whether the deviation rate is below a threshold X. The threshold X is set with a positive value that is a certain degree less than 1.

[0027] Next, if the deviation rate is determined to exceed the threshold X (S150: NO), in step S160, the electronic control unit 20 directly calculates the value of the standard output limit value LM0 as the output limit value LM. Conversely, if the deviation rate is determined to be below the threshold X (S150: YES), in step S170, the electronic control unit 20 adds a predetermined additional amount U to the standard output limit value LM0 and calculates the value of this addition operation as the output limit value LM. Then, after calculating the output limit value LM in step S160 or step S170, the electronic control unit 20 ends the processing of this routine procedure in the current control cycle.

[0028] <Function of the first embodiment>

[0029] The exhaust purification catalyst 18 is in a state of decreased exhaust purification rate until the engine warm-up is complete. Therefore, after a cold start, during the period until the exhaust purification catalyst 18 has warmed up, if the engine 10 operates at high output and a large amount of exhaust flows into the exhaust purification catalyst 18, unpurified exhaust may be released into the atmosphere. The electronic control unit 20 performs output limiting control during this period. Then, in this output limiting control, the electronic control unit 20 suppresses the deterioration of emissions during cold starts by controlling the engine output Pe to a value below the output limit value LM.

[0030] Setting the output limit value LM Figure 2 In the processing, the electronic control unit 20 calculates the estimated vehicle speed Ve based on the engine output Pe. This estimated vehicle speed Ve is an estimate of the vehicle speed assuming a fixed driving resistance (S130). Furthermore, the electronic control unit 20 calculates the deviation rate as the ratio of the actual vehicle speed Vt to the estimated vehicle speed Ve (S140). Then, if the deviation rate exceeds a threshold X (S150: NO), the electronic control unit 20 sets the standard output limit value LM0 to the output limit value LM (S160). Conversely, if the deviation rate is below the threshold X (S150: YES), the electronic control unit 20 adds an additional amount U to the standard output limit value LM0 and sets it to the output limit value LM (S170). The threshold X contains a positive value slightly less than 1. Therefore, a deviation rate below the threshold X indicates that the actual vehicle speed Vt is lower than the estimated vehicle speed Ve, and the deviation between the actual vehicle speed Vt and the estimated vehicle speed Ve is large. Therefore, when the actual vehicle speed Vt is lower than the estimated vehicle speed Ve and the deviation between the actual vehicle speed Vt and the estimated vehicle speed Ve is large, the electronic control unit 20 sets the output limit value LM to a larger value than in other cases.

[0031] Figure 3 The diagram shows an example of the control method for cold start of engine 10. Figure 3 (a) represents the change in cumulative air volume M. Figure 3 (b) represents the change in engine output Pe. Figure 3 (c) represents the changes in actual vehicle speed Vt and estimated vehicle speed Ve. Figure 3 (d) indicates the shift in the deviation rate. In Figure 3 In this case, engine 10 starts at time t0. Electronic control unit 20 begins output limiting control of engine 10 from time t0. At a subsequent time t2, the accumulated air volume M reaches the warm-up determination value Mx. At time t2, electronic control unit 20 determines that the warm-up of exhaust purification catalyst 18 is complete and ends output limiting control.

[0032] When vehicle 1 is heavily loaded or climbing a hill, its speed is difficult to increase due to high driving resistance. The electronic control unit 20 calculates an estimated vehicle speed Ve based on the engine output Pe. This estimated speed Ve is a value estimated under the assumption of a fixed driving resistance. When vehicle 1 experiences driving resistance exceeding the fixed value, the actual vehicle speed Vt becomes lower than the estimated speed Ve. Therefore, when the actual vehicle speed Vt is lower than the estimated speed Ve and the deviation between the actual speed Vt and the estimated speed Ve is large, it is assumed that vehicle 1 is experiencing driving resistance exceeding the fixed value. In this case, the driving force required for vehicle 1 to move also increases.

[0033] exist Figure 3 In the case where, at time t1 during the output limiting process, the deviation rate falls below the threshold X. Up to time t1, the electronic control unit 20 sets the standard output limit value LM0 to the output limit value LM. Then, after time t1, the electronic control unit 20 adds an additional amount U to the standard output limit value LM0 and sets it to the output limit value LM.

[0034] exist Figure 3 In (b), the shift of engine output Pe is shown by dashed lines when the standard output limit value LM0 is continuously set to the output limit value LM after time t1. In this case, engine output Pe is controlled to be below the standard output limit value LM0. The standard output limit value LM0 is set to limit engine output Pe to suppress emissions degradation even if the exhaust purification catalyst 18 has not fully warmed up. Therefore, in this case, the driving force of the vehicle 10 generated by the engine 10 may be insufficient relative to the driving resistance experienced by the vehicle 1.

[0035] On the other hand, Figure 3 In (b), the shift of engine output Pe in this embodiment is shown by a thick solid line. In this embodiment, even during the execution of output limit control, engine output Pe exceeding the standard output limit value LM0 is allowed after time t1.

[0036] <Effects of the first implementation method>

[0037] The engine control device of this embodiment has the following effects.

[0038] The electronic control unit 20 performs output limiting control to keep the engine output Pe below the output limit value LM during the period until the exhaust purification catalyst 18 has warmed up. Furthermore, the electronic control unit 20 calculates an estimated vehicle speed Ve based on the engine output Pe, which is an estimate of the vehicle speed assuming a predetermined driving resistance. Then, if the actual vehicle speed Vt is lower than the estimated vehicle speed Ve and the deviation between the actual vehicle speed Vt and the estimated vehicle speed Ve is large, the electronic control unit 20 sets the output limit value LM to a larger value than in other cases. Therefore, when the vehicle 1 is traveling under high driving resistance, the upper limit of the engine output Pe that can be generated in the output limiting control is higher than usual. Thus, the engine control device of this embodiment has the effect of suppressing emission deterioration without causing insufficient driving force of the vehicle 1.

[0039] (Second Implementation)

[0040] Next, a second embodiment of the engine control device will be described. In this embodiment, structures identical to those in the above embodiment are labeled with the same symbols, and their detailed descriptions are omitted. The processing content of the output limit value setting routine of the engine control device in this embodiment differs from that in the first embodiment.

[0041] Figure 4 The diagram shows a flowchart of the output limit value setting routine executed by the electronic control unit 20 of this embodiment. During output limit control, the electronic control unit 20 repeatedly executes this routine according to a predetermined control cycle. The processing of steps S120, S150 to S170 in this routine is as follows... Figure 2 The situation is the same.

[0042] In this embodiment, if the electronic control unit 20 starts this routine procedure, in step S105, it acquires the cumulative air volume M, the engine output Pe, and the actual acceleration At of the vehicle 1. The actual acceleration At is obtained, for example, as a value obtained by differentiating the actual vehicle speed Vt over time. Then, the electronic control unit 20 and... Figure 2After performing the same processing step S120, the process proceeds to step S135. In step S135, the electronic control unit 20 calculates the estimated acceleration Ae based on the engine output Pe. The estimated acceleration Ae represents an estimate of the acceleration of vehicle 1 traveling at the current engine output Pe, assuming a fixed driving resistance. Then, in the next step S145, the electronic control unit 20 divides the actual acceleration At by the estimated acceleration Ae and calculates the value of this division operation as the deviation rate. Then, the electronic control unit 20 proceeds to step S150. The subsequent processing steps S150 to S170 are similar to... Figure 2 The situation is the same.

[0043] When traveling under significant resistance, vehicle 1's acceleration is unlikely to increase. Therefore, even if the actual acceleration At is lower than the estimated acceleration Ae calculated above, and the deviation between the actual acceleration At and the estimated acceleration Ae is large, vehicle 1 is considered to be traveling under resistance exceeding a predetermined magnitude. Therefore, in Figure 4 In step S145, even if the deviation rate is calculated as a ratio of the actual acceleration At relative to the estimated acceleration Ae, it is possible to... Figure 2 The same determination is performed in step S150 as in the case of the first embodiment. Therefore, the engine control device of this embodiment performs the same function as in the case of the first embodiment.

[0044] (Other implementation methods)

[0045] The above-described embodiments can be modified as follows. The embodiments of the present invention and the following...

[0046] For example, they can be combined and implemented within a technically compatible range.

[0047] In the above-described embodiment, by setting the standard output limit value LM0 to a value that increases as the cumulative air volume M approaches the warm-up determination value Mx, the limitation on engine output Pe in the output limit control is mitigated based on the warm-up process of the exhaust purification catalyst 18. This setting method for the standard output limit value LM0 can be appropriately modified. For example, the standard output limit value LM0 can be set to a fixed value.

[0048] • In the above-described embodiment, the completion of warm-up of the exhaust gas purification catalyst 18 is determined based on the cumulative air volume M, but this determination can also be made by other methods. For example, the completion of warm-up of the exhaust gas purification catalyst 18 can be determined based on the elapsed time after startup. Furthermore, the temperature of the exhaust gas purification catalyst 18 can be measured or estimated, and the determination can be made based on the measured value.

[0049] ·exist Figure 2 and Figure 4 In step S170, the output limit value LM is calculated by adding the additional amount U to the standard output limit value LM0. However, the calculation of the output limit value LM in step S170 can also be performed in other ways, provided that the output limit value LM is calculated to be greater than the standard output limit value LM0. For example, step S170 can be performed by multiplying the standard output limit value LM0 by a coefficient set to a value greater than "1" and setting the resulting value as the output limit value LM.

[0050] ·exist Figure 2 and Figure 4 If, in step S150, the deviation rate is determined to be below the threshold X, the output limit of engine 10 can also be lifted. The state of lifting the output limit can be regarded as the state of setting the maximum output of engine 10 to the value of the output limit value LM and performing output limit control.

[0051] In the above-described embodiment, the deviation rate, calculated as the ratio of the actual vehicle speed Vt relative to the estimated vehicle speed Ve or the ratio of the actual acceleration At relative to the estimated acceleration Ae, is used for... Figure 2 and Figure 4 The determination in step S150 can also be made using the difference between the actual vehicle speed Vt and the estimated vehicle speed Ve, or the difference between the actual acceleration At and the estimated acceleration Ae.

[0052] Symbol Explanation

[0053] 1-Vehicle, 10-Engine, 11-Combustion chamber, 12-Intake passage, 13-Exhaust passage, 14-Air flow meter, 15-Throttle valve, 16-Injector, 17-Ignition device, 18-Exhaust purification catalyst, 20-Electronic control unit, 21-Processing circuit, 22-Storage device.

Claims

1. An engine control device suitable for an engine mounted in a vehicle and having an exhaust purification catalyst disposed in the exhaust passage, the engine control device being characterized in that it performs the following processing: Based on engine output, the estimated vehicle speed is calculated under the assumption that the driving resistance is a given magnitude. If the actual vehicle speed is lower than the estimated vehicle speed and the deviation between the actual vehicle speed and the estimated vehicle speed is large, the output limit value will be set to a larger value than in other cases; and During the period until the exhaust purification catalyst has finished warming up, the engine output is controlled so that the engine output is below the output limit value.

2. An engine control device suitable for an engine mounted in a vehicle and having an exhaust purification catalyst disposed in the exhaust passage, the engine control device being characterized in that it performs the following processing: Based on engine output, the estimated acceleration of the vehicle is calculated under the assumption that the driving resistance is a given magnitude. If the actual acceleration of the vehicle is lower than the estimated acceleration and the deviation between the actual acceleration and the estimated acceleration is large, the output limit value will be set to a larger value than in other cases; and During the period until the exhaust purification catalyst has finished warming up, the engine output is controlled so that the engine output is below the output limit value.

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