Vehicle control system
The vehicle control device addresses engine overrotation by implementing gradual torque reduction and recovery processes, ensuring stable engine operation.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2024-11-29
- Publication Date
- 2026-06-10
AI Technical Summary
Existing engine overrotation suppression methods risk engine rotational speed rebound due to rapid torque reduction, failing to sufficiently suppress overrotation.
A vehicle control device with a determination unit that gradually or stepwise reduces engine torque and enables controlled torque recovery, disabling shift control during torque processes to prevent overrotation.
Effectively suppresses engine overrotation by preventing rotational speed spikes through gradual torque adjustments and controlled recovery processes.
Smart Images
Figure 2026094923000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a vehicle control device.
Background Art
[0002] There is a technique for suppressing vibration of a vehicle by controlling the torque of an engine (see, for example, Patent Document 1).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] When the engine overrotates, by reducing the torque of the engine, the rotational speed of the engine can be reduced to suppress the overrotation of the engine. However, if the torque of the engine is rapidly reduced, there is a possibility that the rotational speed of the engine will rise again due to the recoil, and the overrotation of the engine cannot be sufficiently suppressed.
[0005] Therefore, an object of the present invention is to provide a vehicle control device that can sufficiently suppress the overrotation of an engine.
Means for Solving the Problems
[0006] The above object can be achieved by a vehicle control device including a determination unit that determines whether or not an engine mounted on a vehicle has overrotated, and a control unit that, when the determination unit makes an affirmative determination, executes a torque reduction process for reducing the torque of the engine more than when the determination unit makes a negative determination, and the control unit executes the torque reduction process by gradually or stepwise reducing the torque of the engine.
[0007] The control unit may perform a torque recovery process to gradually or stepwise increase the torque of the engine after the torque reduction process has been executed.
[0008] The control unit may cancel the torque recovery process if the vehicle is started while the torque recovery process is being executed.
[0009] The control unit may, while the torque reduction process is being executed, disable the shift control of the automatic transmission provided on the power transmission path between the engine and the drive wheels.
[0010] The control unit may, while the torque recovery process is being executed, disable the shift control of the automatic transmission provided on the power transmission path between the engine and the drive wheels. [Effects of the Invention]
[0011] According to the present invention, a vehicle control device can be provided that can sufficiently suppress engine over-revolution. [Brief explanation of the drawing]
[0012] [Figure 1] Figure 1 is a schematic diagram of the vehicle's configuration. [Figure 2] Figure 2 is a flowchart illustrating over-speed suppression control. [Figure 3] Figure 3 is a timing chart illustrating the torque reduction process. [Figure 4] Figure 4 is a timing chart illustrating the torque recovery process. [Modes for carrying out the invention]
[0013] [Vehicle Outline] Figure 1 is a schematic diagram showing the general configuration of vehicle 1. Vehicle 1 is equipped with a torque converter (T / C) 12, a clutch 13C, and an automatic transmission (A / T) 14 in the power transmission path between the engine (ENG) 10 and the drive wheels 18. The engine 10 is a gasoline engine with multiple cylinders, but it may also be a diesel engine or a hydrogen engine. The torque converter 12 is connected to the crankshaft 11 of the engine 10. The turbine shaft 13 of the torque converter 12 is connected to the input side of the automatic transmission 14 via the clutch 13C, and the driving force of the engine 10 is transmitted to the automatic transmission 14. The clutch 13C engages when hydraulic pressure is supplied, connecting the power transmission between the turbine shaft 13 and the input shaft of the automatic transmission 14. The clutch 13C disengages when the hydraulic pressure supply is stopped, interrupting the power transmission between the turbine shaft 13 and the input shaft of the automatic transmission 14. Note that the torque converter 12 is not required. Furthermore, the automatic transmission 14 may also be a dog transmission.
[0014] The output shaft 15 of the automatic transmission 14 is connected to the differential gear 16, which is the final reduction gear. The left and right axles 17 are connected to the differential gear 16. The driving force transmitted to the output shaft 15 is transmitted to the drive wheels 18 via the axles 17.
[0015] The automatic transmission 14 is a stepped transmission and includes multiple hydraulic friction engagement elements and a planetary gear system. In the automatic transmission 14, the multiple friction engagement elements are selectively engaged to switch between P (parking), R (reverse), N (neutral), and D (drive) ranges. The automatic transmission 14 has an AT clutch 14C. The AT clutch 14C engages when hydraulic pressure is supplied, connecting the power transmission between the input shaft and output shaft of the automatic transmission 14. The AT clutch 14C disengages when the hydraulic pressure supply is stopped, interrupting the power transmission between the input shaft and output shaft of the automatic transmission 14. When the AT clutch 14C is disengaged, the automatic transmission 14 is switched to the N range.
[0016] The ECU (Electronic Control Unit) 20 is an electronic control unit that performs control processing related to the vehicle 1. The ECU 20 is a computer that includes a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory). The ECU 20 is an example of a vehicle control device and functionally implements the determination unit and control unit, which will be described in more detail later.
[0017] The ECU 20 is connected to a crank angle sensor 21, a shift position sensor 22, and a vehicle speed sensor 23. The crank angle sensor 21 detects the rotational speed of the engine 10. The shift position sensor 22 detects whether the shift lever is in the P range, R range, N range, or D range. The vehicle speed sensor 23 detects the speed of the vehicle 1.
[0018] The ECU 20 calculates the required torque and target rotational speed for the engine 10 based on the engine speed, intake air volume, and accelerator opening detected by the above-mentioned sensors. The ECU 20 controls the fuel injection volume, intake air volume, and ignition timing according to the required torque and target rotational speed. For example, when the engine 10 is idling, the ECU 20 controls the fuel injection volume, intake air volume, and ignition timing so that the engine speed becomes the target idle speed and the engine torque becomes the supplied torque. The ECU 20 also controls the drive of the clutch 13C and the automatic transmission 14 through the control of the hydraulic control mechanism. The ECU 20 performs over-speed suppression control to suppress over-speed of the engine 10 when predetermined conditions are met, as described below.
[0019] [Over-speed suppression control] Figure 2 is a flowchart illustrating over-rotation suppression control. This control is continuously repeated while the ignition is on. The ECU 20 determines whether the engine 10 has over-rotated (step S1). For example, when the rotational speed of the engine 10 becomes equal to or higher than the upper limit rotational speed, it is determined that the engine 10 has over-rotated. Note that the determination of over-rotation is not limited to the above method. For example, over-rotation may be determined based on the rotational acceleration of the engine 10. If the result in step S1 is No, this control ends. Step S1 is an example of the process executed by the determination unit.
[0020] If the result in step S1 is Yes, the ECU 20 prohibits the shift control of the automatic transmission 14 (step S2). The reason for prohibiting the shift control will be described later. Step S2 is an example of the process executed by the control unit.
[0021] Next, the ECU 20 executes torque reduction processing to reduce the torque of the engine 10 more than when the result in step S1 is No (step S3). Specifically, the torque reduction processing is executed by gradually or stepwise reducing the torque of the engine 10. The torque reduction processing is realized, for example, by retarding the ignition timing or by executing fuel cut in some cylinders of the engine 10 and retarding the ignition timing of the remaining cylinders. For example, by gradually or stepwise retarding the ignition timing or by gradually increasing the number of cylinders in which fuel cut is executed, the torque of the engine 10 is gradually or stepwise reduced. As a result, as will be described in detail later, over-rotation of the engine 10 can be sufficiently suppressed. Step S3 is an example of the process executed by the control unit.
[0022] Next, the ECU 20 determines whether the torque return condition is satisfied (step S4). The torque return condition is a condition for executing torque return processing, which will be described later. The torque return condition is determined to be satisfied, for example, when the rotational speed of the engine 10 becomes lower than the return rotational speed. The return rotational speed is lower than the above-described upper limit rotational speed.
[0023] Furthermore, the torque recovery condition is not limited to the conditions relating to the rotational speed of the engine 10. For example, the torque recovery condition may be determined to be met when a predetermined time has elapsed since the start of the torque reduction process. Alternatively, for example, the torque recovery condition may be determined to be met when the rotational speed of the engine 10 is less than or equal to the recovery rotational speed AND a predetermined time has elapsed since the start of the torque reduction process. If the answer in step S4 is No, the execution of step S3 continues.
[0024] If the answer in step S4 is Yes, the ECU 20 performs torque recovery processing (step S5). Torque recovery processing is a process that gradually or stepwise increases the torque of the engine 10. Specifically, torque recovery processing is a process that releases the torque limitation imposed by the torque reduction processing and returns the torque of the engine 10 to the original accelerator-requested torque. As will be explained in more detail later, by gradually or stepwise increasing the torque of the engine 10 in the torque recovery processing, it is suppressed that the engine 10 will over-rev again. Step S5 is an example of processing performed by the control unit.
[0025] Next, the ECU 20 determines whether or not the vehicle 1 has been started while the torque recovery process is being executed (step S6). For example, this occurs when the vehicle speed is below a predetermined speed at which it can be considered to be stationary, the engine speed of the 10 is below a predetermined speed, and the position of the shift lever has been switched from the N range position to the D range position or the R range position. In vehicles equipped with a manual transmission instead of an automatic transmission 14, this occurs when the vehicle speed is below a predetermined speed at which it can be considered to be stationary, the engine speed of the 10 is below a predetermined speed, and the clutch pedal has been operated to set a gear position of the manual transmission to a predetermined gear position or lower, for example, 1st gear. If the answer in step S6 is No, this control process ends.
[0026] If the answer in step S6 is Yes, the ECU 20 cancels the torque recovery process (step S7). This enables torque control of the engine 10 that is suitable for starting the vehicle 1, and ensures drivability. Step S7 is an example of a process performed by the control unit.
[0027] The disallowance of the gear shift control of the automatic transmission 14 described above continues until the torque reduction process is initiated and the torque recovery process is completed or released. This is because gear shift control can sometimes lead to situations where over-revving is easily induced due to blipping. Similarly, if the automatic transmission 14 is a dog-type transmission, gear shift control can also lead to situations where over-revving is easily induced due to dog-disengagement control.
[0028] Figure 3 is a timing chart illustrating a torque reduction process. Figure 3 shows the changes in engine speed and torque of engine 10 when the accelerator opening is constant. Figure 3 shows a case where the torque of engine 10 is gradually reduced by the torque reduction process as the first embodiment, and a case where the torque of engine 10 is gradually reduced by the torque reduction process as the second embodiment. Figure 3 also shows a case where the torque of engine 10 is rapidly reduced as a comparative example of torque reduction process.
[0029] First, let's explain the torque reduction process in the comparative example. When the torque of engine 10 is maintained at the accelerator-required torque corresponding to the accelerator opening, the rotational speed of engine 10 exceeds the upper limit rotational speed, and the torque of engine 10 is rapidly reduced to the reduction-required torque due to the torque reduction process (time t1). As a result, the rotational speed of engine 10 decreases. However, when the torque of engine 10 decreases rapidly in this way, the direction of power transmission switches from from engine 10 to drive wheels 18 to from drive wheels 18 to engine 10. As a result, torque in the opposite direction to the rotational direction is applied to the shafts, gears, etc. between engine 10 and drive wheels 18, causing twisting. Due to the reaction of this twisting, the rotational speed of engine 10 increases again and exceeds the upper limit rotational speed (time t4). When the torque of engine 10 is rapidly reduced in this way, there is a risk that over-rotation of engine 10 cannot be sufficiently suppressed.
[0030] In the torque reduction process of the first embodiment, the torque of the engine 10 is first reduced by a first reduction amount ΔTa (time t1). Subsequently, the torque of the engine 10 is reduced by a second reduction amount ΔTb, and the torque of the engine 10 is maintained at the torque reduction target (time t2). By reducing the torque in this stepwise manner, the reaction described above is suppressed, and it is prevented that the rotational speed of the engine 10 exceeds the upper limit rotational speed again (time t4). In this way, over-rotation of the engine 10 is sufficiently suppressed in the first embodiment.
[0031] The magnitude of the first reduction amount ΔTa is greater than the magnitude of the next second reduction amount ΔTb. This suppresses further increases in the rotational speed of the engine 10 when the rotational speed of the engine 10 exceeds the upper limit rotational speed. In the first embodiment, the torque of the engine 10 was reduced in two stages, but it may be reduced in three or more stages. Even when the torque is reduced in three or more stages, from the viewpoint of suppressing over-rotation of the engine 10, it is preferable that the magnitude of the reduction amount in the first stage is greater than the magnitude of the reduction amounts in each subsequent stage.
[0032] In the torque reduction process of the second embodiment, the torque of the engine 10 gradually decreases (time t1), and eventually decreases to the torque to be reduced (time t3). By gradually reducing the torque in this way, the reaction described above is suppressed, and it is prevented that the rotational speed of the engine 10 exceeds the upper limit rotational speed again (time t4). In this way, over-rotation of the engine 10 is sufficiently suppressed in the second embodiment as well.
[0033] In the torque reduction process of the second embodiment, the amount of torque reduction per unit time is controlled to decrease gradually. That is, as shown in Figure 3, the torque of the engine 10 decreases in a downward convex shape. This suppresses further increases in the rotational speed of the engine 10 when the rotational speed of the engine 10 exceeds the upper limit rotational speed. In the second embodiment, the torque of the engine 10 decreases gradually in a curve, but the torque of the engine 10 may also be gradually reduced by multiple straight lines.
[0034] Next, the torque recovery process will be explained. Figure 4 is a timing chart illustrating the torque recovery process. Figure 4 shows the changes in engine speed and torque of engine 10 when the accelerator opening is constant. Figure 4 shows the case where the system switches from the torque reduction process of the first embodiment to the torque recovery process, which gradually increases the torque. Figure 4 also shows a case where the torque of engine 10 increases rapidly as a comparative example.
[0035] First, let's explain the torque recovery process in the comparative example. If the rotational speed of engine 10 drops below the recovery rotational speed during the execution of the torque reduction process (time t5), the torque of engine 10 rapidly increases to the accelerator-required torque (time t6). As a result, the rotational speed of engine 10 also rapidly increases to above the upper limit rotational speed (time t7). This may cause the torque reduction process to be executed again, potentially leading to repeated execution of the torque reduction process.
[0036] In the torque recovery process of the first embodiment, the torque of the engine 10 gradually increases at a constant rate (time t6). This suppresses a sudden increase in the rotational speed of the engine 10 and avoids the repeated execution of the torque reduction process.
[0037] In the torque recovery process of the first embodiment, the case in which the torque of the engine 10 increases linearly was described as an example, but it is not limited to this. For example, the torque recovery process may increase the torque of the engine 10 in steps or in a curved manner.
[0038] In the above embodiment, an ECU 20 mounted on a vehicle equipped with an engine 10 as a driving power source was described as an example of a vehicle control device. However, a vehicle control device mounted on a hybrid vehicle equipped with both an engine and a motor as driving power sources may also be used. In the case of a hybrid vehicle, the torque reduction process may be achieved, for example, by regenerating the motor so that the torque in the opposite direction to the engine's rotation direction increases. Furthermore, the torque recovery process may be achieved by gradually reducing the regenerative torque of the motor.
[0039] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]
[0040] 1 vehicle 10 Engines 14 Automatic transmission 20 ECU (Vehicle control unit, determination unit, and control unit)
Claims
1. A determination unit that determines whether or not the engine mounted on the vehicle has become over-revved, The system includes a control unit that, if the determination unit determines that the result is positive, performs a torque reduction process that reduces the engine torque compared to the case where the determination unit determines that the result is negative, The control unit is a vehicle control device that performs the torque reduction process by gradually or stepwise reducing the torque of the engine.
2. The vehicle control device according to claim 1, wherein the control unit performs a torque recovery process that increases the torque of the engine in stages or gradually after the execution of the torque reduction process.
3. The vehicle control device according to claim 2, wherein the control unit cancels the torque recovery process if the vehicle is started while the torque recovery process is being executed.
4. The vehicle control device according to any one of claims 1 to 3, wherein the control unit disallows shift control of an automatic transmission provided on the power transmission path between the engine and the drive wheels while the torque reduction process is being executed.
5. The vehicle control device according to claim 2 or 3, wherein the control unit prohibits the shift control of the automatic transmission provided on the power transmission path between the engine and the drive wheels while the torque recovery process is being executed.