Engine control device

Abstract

To provide an engine control device that protects an engine by preventing overspeed and improves drivability by reducing deceleration shock.SOLUTION: An engine control device includes: an accelerator sensor that detects input of an accelerator; a rotation sensor that detects speed of an engine; and a control section that executes limitation cylinder control for continuing combustion of some cylinders out of a plurality of cylinders constituting the engine over a preset duration on the basis of the speed detected by the rotation sensor when the accelerator sensor detects release of input.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] When a driver of an engine vehicle suddenly releases the accelerator pedal (accelerator off), dashpod control is known to gradually reduce the amount of air intake into the engine while maintaining the combustion state for a certain period of time in order to mitigate the deceleration shock caused by a sudden decrease in engine speed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-36948 Summary of the Invention [Problem to be solved by the invention]

[0004] When the engine speed when the accelerator is released is close to the upper limit of the allowable speed, even if dashpod control is performed, the engine speed may temporarily exceed the upper limit (engine overspeed) due to the sudden release of twist in the drive shaft, causing an overload on the engine.

[0005] The present invention has been made to solve such problems, and provides an engine control device and the like that prevents over-revving to protect the engine, and also reduces deceleration shock to improve drivability. [Means for solving the problem]

[0006] An engine control device in one aspect of the present invention includes an accelerator sensor that detects accelerator input, a rotation sensor that detects engine speed, and a control unit that executes limited cylinder control to continue combustion in some of the multiple cylinders that make up the engine for a predetermined duration based on the rotation speed detected by the rotation sensor at the time the accelerator sensor detects the release of the input. [Effects of the Invention]

[0007] The present invention can provide an engine control device that protects the engine by preventing over-revving, and also reduces deceleration shock to improve drivability. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of an engine control device according to an embodiment of the present invention; [Figure 2] FIG. 10 is a diagram illustrating an example of the relationship between elapsed time and accelerator opening degree. [Figure 3] FIG. 4 is a diagram illustrating an example of the relationship between elapsed time and engine rotation speed. [Figure 4] FIG. 10 is a diagram illustrating an example of the relationship between elapsed time and an execution flag. [Figure 5] FIG. 10 is a diagram illustrating an example of the relationship between elapsed time and the number of combustion cylinders. [Figure 6] FIG. 4 is a diagram illustrating an example of a relationship between elapsed time and an ignition retard amount. [Figure 7] FIG. 10 is a diagram showing an example of the relationship between elapsed time and a throttle opening degree. [Figure 8] FIG. 4 is a diagram illustrating an example of the relationship between the number of stopped cylinders and engine torque. [Figure 9] FIG. 2 is a control flow diagram of an engine control process executed by an ECU. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the invention according to the claims is not limited to the following embodiments. Furthermore, not all of the configurations described in the embodiments are necessarily essential as means for solving the problems.

[0010] 1 is a schematic diagram of an engine control device 100 according to this embodiment. The engine control device 100 is mounted on a vehicle (not shown). The engine control device 100 is mainly composed of an ECU (Electronic Control Unit) 110, an engine 120, a memory unit 130, an accelerator 140, and associated circuits, sensors, and actuators.

[0011] The ECU 110 is a computer unit including a processor (CPU: Central Processing Unit) and a volatile memory. The ECU 110 reads an engine control program stored in the storage unit 130 and executes various processes related to engine control. In other words, the ECU 110 functions as a control unit that comprehensively controls the engine control device 100.

[0012] The engine 120 is, for example, a gasoline engine, and in this embodiment, it will be described as a four-cylinder gasoline engine having four cylinders (C1, C2, C3, C4). Each cylinder has an ignition plug 121 and a throttle 123, and the combustion cycle is controlled by synchronizing the ignition of the spark plug 121 by a plug control circuit 122 with the opening and closing of the throttle 123 by a throttle actuator 124. Note that timing commands to the plug control circuit 122 and drive commands to the throttle actuator 124 are part of the control commands generated by the ECU 110.

[0013] Drive shaft 125 is an output shaft of engine 120. Rotation sensor 126 is a sensor that detects the rotation speed of drive shaft 125, and a magnetic sensor is used, for example. A detection signal from rotation sensor 126 is transmitted to ECU 110. ECU 110 can steadily grasp the rotation speed of engine 120 by successively receiving the detection signal from rotation sensor 126.

[0014] The storage unit 130 is a non-volatile storage medium and is configured, for example, by an SSD (Solid State Drive). In addition to storing the engine control program, the storage unit 170 also stores constants, variables, setting values, and the like required for the operation of the engine control device 100. In particular, in this embodiment, the storage unit 170 stores a control table 131 and a detection history 132. As will be described in detail later, the control table 131 includes a table showing the relationship between the number of stopped cylinders and engine torque, and a table showing the relationship between the accelerator input amount immediately before the accelerator is released and the required torque, and the detection history 132 includes a history of the accelerator input amount over a certain period of time.

[0015] Accelerator 140 is an input device that is operated by the driver or driven by an automatic driving device. During normal driving, the combustion cycle of engine 120 is controlled so that the vehicle accelerates or decelerates according to the input amount of accelerator 140. Accelerator sensor 141 is a sensor that detects the input amount of accelerator 140, and a potentiometer is used, for example. A detection signal from accelerator sensor 141 is transmitted to ECU 110. ECU 110 can steadily grasp the input amount of accelerator 140 by sequentially receiving the detection signals from accelerator sensor 141.

[0016] Dashpod control is known, which adjusts the throttle opening to gradually reduce the amount of air intake into the engine while maintaining combustion in all cylinders for a certain period of time when the driver of an engine vehicle suddenly releases the accelerator pedal (accelerator off). Dashpod control can mitigate deceleration shock experienced by the driver and other passengers. However, even when dashpod control is executed, if the engine speed at the time of accelerator release is close to the upper limit of the allowable speed, the engine speed may temporarily exceed the upper limit as the torsion of the drive shaft caused by the rotational drive up to that point is suddenly released, causing an overload on the engine. Therefore, in this embodiment, if the rotation speed detected by the rotation sensor 126 exceeds a threshold value when the accelerator sensor 141 detects the release of the accelerator 140 input, the ECU 110 executes cylinder limiting control, which continues combustion in some of the four cylinders (C1, C2, C3, and C4) that make up the engine 120 and stops combustion in the other cylinders for a predetermined duration. When the rotation speed is equal to or less than the threshold value, the ECU 110 executes dashpod control, which will be described in detail below using an example.

[0017] FIG. 2 is a diagram showing an example of the relationship between elapsed time (horizontal axis) and accelerator opening (vertical axis). The accelerator opening is a value corresponding to the accelerator input amount detected by the accelerator sensor 141, and is 0 when the accelerator is released and 1 when the accelerator is fully depressed. In the example described below, the elapsed time t s The case where the driver releases the accelerator at time t a The accelerator opening at time t is F, and this information is stored in the detection history 132. Here, Δt is a very short time, and the elapsed time t a is the elapsed time t s It can be said that it is essentially just before the

[0018] Figure 3 is a diagram showing an example of the relationship between elapsed time (horizontal axis) and engine speed (vertical axis), where the elapsed time corresponds to the elapsed time in Figure 2. The solid line shows the change in engine speed over time when cylinder limit control is executed, and the dotted line shows the change in engine speed over time when dashpod control is executed. The dash-dotted line shows, as a reference example, the change in engine speed over time when neither cylinder limit control nor dashpod control is executed when cylinder limit control should be executed.

[0019] The ECU 110 detects the elapsed time t s When the ECU 110 detects the release of the accelerator pedal, it immediately receives a detection signal from the rotation sensor 126 and acquires the engine rotation speed R. The ECU 110 then checks whether the detected engine rotation speed R is greater than or equal to a preset threshold value R th If the threshold value R th Dash pod control will be initiated in the following cases:

[0020] The confirmed engine speed R is equal to the preset threshold R th If the limit cylinder control is not performed even though the engine speed exceeds the upper limit R, the engine speed will remain at the upper limit R for a short period of time, as shown by the dashed line. max Even when dashpod control is performed, the upper limit of RPM R max However, if the cylinder limit control is executed, the ECU 110 can prevent the upper limit rotation speed R from exceeding the upper limit rotation speed R as shown by the solid line. max The engine speed R can be converged over time without exceeding the value.

[0021] In addition, the threshold R th is determined in advance according to the characteristics of the engine 120. Specifically, it is determined by trial and error or based on the results of simulations, taking into consideration the engine speed that increases when the torsion of the drive shaft 125 is eliminated.

[0022] Elapsed time t s The engine speed R at the threshold R thIn the following cases, when dashpod control is started, the ECU 110 still sets the upper limit rotation speed R max In this case, it is possible to reduce the deceleration shock caused by a sudden decrease in the engine speed.

[0023] Specific processing of the cylinder limit control and dashpod control will be explained along the time course. FIG. 4 is a diagram showing an example of the relationship between elapsed time (horizontal axis) and execution flag (vertical axis). The execution flag specifies the period for executing the control, and the execution flag of the cylinder limit control is set as the elapsed time t s From t e The dash pod control execution flag is set to "1" until the elapsed time t s From t d It is "1" until the elapsed time t s The cylinder limiting control started at elapsed time t e and the elapsed time t s The dashpod control started at elapsed time t d and ends.

[0024] 5 is a diagram showing an example of the relationship between elapsed time (horizontal axis) and the number of combustion cylinders (vertical axis). As described above, engine 120 in this embodiment has four cylinders, so the vertical axis is a discrete value of "0," "1," "2," "3," and "4."

[0025] As described above, cylinder limiting control is a control that continues combustion in some of the four cylinders and stops combustion in the other cylinders. In the example shown in the figure, as indicated by the solid lines, combustion continues in three cylinders and combustion in one cylinder is stopped. In this way, cylinder limiting control continues combustion in some cylinders even when the accelerator is released, thereby applying a constant rotational torque to the drive shaft 125 during the control period. The specific number of cylinders that are allowed to continue combustion will be described later.

[0026] On the other hand, in dashpod control, as shown by the dotted line, combustion continues in all cylinders during the control period even when the accelerator is released, but the rotational torque applied to the drive shaft 125 is gradually reduced as described below.

[0027] FIG. 6 is a diagram showing an example of the relationship between elapsed time (horizontal axis) and ignition retard amount (vertical axis). Ignition retard is a control for retarding the ignition timing of the spark plug 121, and the ignition retard amount corresponds to a delay time relative to the reference ignition timing. In the example shown in the figure, an ignition retard amount m is set when cylinder limit control is executed. The ignition timing of the spark plug 121 is adjusted by the plug control circuit 122 in accordance with a timing command received from the ECU 110. By retarding the ignition timing of the spark plug 121, the ECU 110 can adjust the torque output by that cylinder within a certain range. The specific method for setting the ignition retard amount will be described later. Note that the ignition timing of the spark plug 121 is not retarded in dashpod control.

[0028] 7 is a diagram showing an example of the relationship between elapsed time (horizontal axis) and throttle opening degree (vertical axis) during intake. In the dashpod control, the elapsed time t s The throttle opening gradually decreases from the time t d This adjustment of the throttle opening is applied to all four cylinders that continue to receive fuel. The throttle opening during intake is adjusted by the throttle actuator 124 in response to a drive command received from the ECU 110.

[0029] In the limited cylinder control, for the cylinders where combustion continues (three in the example of Figure 5), the elapsed time t e The throttle opening V before the accelerator is released is maintained until the elapsed time t s On the other hand, for the cylinder where combustion is stopped (one in the example of Fig. 5), the elapsed time t sIn this case, the throttle opening is set to 0. In this case, as in the case of dashpod control, the throttle opening during intake is adjusted by the throttle actuator 124 in response to a drive command received from the ECU 110.

[0030] 8 is a diagram showing an example of the relationship between the number of stopped cylinders (horizontal axis) and engine torque (vertical axis). In this embodiment, cylinder limit control prevents a sudden release of twist in drive shaft 125 by leaving torque for a certain period even when the driver releases accelerator 140, and prevents the engine speed from exceeding the allowable upper limit. At this time, the torque left in drive shaft 125, i.e., the required torque TQ required to output from engine 120, is r is calculated by the ECU 110 as the elapsed time t a The accelerator input amount with respect to the elapsed time is stored in the storage unit 130 as the detection history 132 as described above.

[0031] Required torque TQ r is set to increase as the amount of accelerator input increases, because the amount of twist in drive shaft 125 at the time of release increases as the amount of accelerator input immediately before increases. Specifically, calculation formulas and correspondence tables are prepared in advance by trial and error or based on simulation results, taking into account the material and diameter of drive shaft 125.

[0032] In this way, the required torque is TQ r Once calculated, the ECU 110 determines the required torque TQ r The ECU 110 calculates the number of cylinders in which combustion will continue (in other words, the number of cylinders to be stopped) and the ignition retard amount m according to the above. As shown in FIG. 8, the engine torque decreases in stages as the number of stopped cylinders increases. Therefore, the ECU 110 first calculates the required torque TQ r The minimum number of cylinders that can be burned (3 cylinders in the example shown) is determined for the engine torque that exceeds the required torque TQ. rThe ECU 110 calculates the difference Δtq between the torque values ​​and the ignition retard amount m to reduce the torque by the calculated Δtq. The relationship between the number of cylinders in which combustion continues, the torque reduction amount, and the ignition retard amount is prepared in advance, for example, as a look-up table, and the ECU 110 can determine the ignition retard amount m by referring to such a look-up table. If the ECU 110 determines that the number of cylinders in which combustion continues is three, for example, the ECU 110 randomly selects three of the four cylinders. By selecting them randomly, it is possible to maintain a uniform usage history among the four cylinders.

[0033] Next, a description will be given of the procedure of the engine control process executed by the ECU 110. Fig. 9 is a control flow diagram of the engine control process executed by the ECU 110. The flow starts from a traveling state in which the driver depresses the accelerator 140 and the vehicle is traveling.

[0034] In step S101, the ECU 110 receives a detection signal from the accelerator sensor 141 and acquires the accelerator opening degree F. In the following step S102, the ECU 110 checks the acquired opening degree F and determines whether the accelerator 140 has been released. If it is determined that the accelerator 140 has not been released, the process returns to step S101 and the vehicle continues traveling. Note that steps S101 and S102 are repeated at regular intervals while the vehicle is traveling.

[0035] If it is determined in step S102 that the accelerator 140 has been released, the process proceeds to step S103, where the ECU 110 receives a detection signal from the rotation sensor 126 and acquires the engine rotation speed R. In the following step S104, the ECU 110 checks whether the acquired engine rotation speed R is greater than or equal to a preset threshold value R. th If it is determined that it has exceeded the limit, the process proceeds to step S105, and if it is determined that it has not exceeded the limit, the process proceeds to step S110.

[0036] When the process proceeds from step S104 to step S105, the ECU 110 switches the execution flag of the limited cylinder control to ON (corresponding to "1" in FIG. 4) and starts the timer. Then, in step S106, the required torque TQ r is calculated, and the number of cylinders in which combustion is to continue and the amount of ignition retard are determined in step S107.

[0037] Next, the process proceeds to step S108, where the ECU 110 continues combustion in some cylinders and stops combustion in the remaining cylinders according to the determined number of cylinders, and controls the ignition retard amount for the cylinders in which combustion is to continue by sending a timing command to the plug control circuit 122. The ECU 110 proceeds to step S109, where it checks whether the timer has reached a preset end time for the restricted cylinder control, i.e., whether the execution flag for the restricted cylinder control has switched from ON to OFF (corresponding to "0" in FIG. 4). If the flag has not switched, the process returns to step S108, where the restricted cylinder control continues. If the flag has switched, the restricted cylinder control ends and the process transitions to normal driving control.

[0038] When the process proceeds from step S104 to step S110, the ECU 110 switches the dash pod control execution flag to ON (corresponding to "1" in FIG. 4) and starts a timer. Next, the process proceeds to step S111, where the ECU 110 sends a drive command to the throttle actuator 124 to gradually reduce the opening of the throttle 123. The ECU 110 proceeds to step S112, where it checks whether the timer has reached the preset end time for dash pod control, i.e., whether the dash pod control execution flag has switched from ON to OFF (corresponding to "0" in FIG. 4). If the flag has not switched, the process returns to step S111, where dash pod control continues. If the flag has switched, dash pod control ends and the process transitions to normal driving control.

[0039] In the present embodiment described above, the engine 120 is described as having four cylinders, but the number of cylinders does not have to be "4". rIn the above embodiment, Δtq is calculated for Δtq and the ignition retard amount is controlled accordingly, but from the viewpoint of simplifying the control, the control of the ignition retard amount may be omitted. Also, in the above embodiment, an example is described in which dashpod control is performed when cylinder limit control is not performed, but from the viewpoint of simplifying the control, a transition to normal driving control may be performed without performing dashpod control. [Explanation of symbols]

[0040] 100... engine control device, 110... ECU, 120... engine, 121... spark plug, 122... plug control circuit, 123... throttle, 124... throttle actuator, 125... drive shaft, 126... rotation sensor, 130... memory unit, 131... control table, 132... detection history, 140... accelerator, 141... accelerator sensor

Claims

1. an accelerator sensor that detects accelerator input; a rotation sensor that detects the engine rotation speed; a control unit that executes cylinder restriction control to continue combustion in some of the cylinders among the plurality of cylinders that constitute the engine for a predetermined duration based on the rotation speed detected by the rotation sensor at the time when the accelerator sensor detects the release of the input; An engine control device comprising:

2. 2. The engine control device according to claim 1, wherein the control unit calculates a required torque to be required of the engine over the duration based on a detection history of the accelerator sensor, and determines the number of cylinders in which combustion is to continue based on the required torque.

3. The engine control device according to claim 2, wherein the control unit controls an ignition retard amount for a cylinder in which combustion is to continue based on the required torque.

4. 3. The engine control device according to claim 2, wherein the control unit determines the required torque based on the amount of accelerator input detected by the accelerator sensor at a time point a predetermined time before it is detected that the accelerator input has been released.

5. 2. The engine control device according to claim 1, wherein the control unit executes the cylinder restriction control if the rotation speed detected by the rotation sensor exceeds a predetermined threshold value at the time when the accelerator sensor detects that the accelerator input has been released, and executes dashpot control that gradually closes the opening of the throttle valve while continuing combustion in all of the plurality of cylinders if the rotation speed is equal to or less than the threshold value.

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