Vehicle control system

Abstract

The objective is to provide a vehicle control device that can sufficiently suppress engine over-revving. [Solution] A vehicle control device comprising: a prediction unit that predicts whether or not an engine will over-rotate based on a predicted rotational speed, which is a predicted value of the rotational speed of an engine mounted on a vehicle, and at least one of the rotational acceleration of the engine; and a control unit that, when over-rotation of the engine is predicted, performs a torque reduction process to reduce the torque of the engine compared to when over-rotation of the engine is not predicted.

Description

Technical Field

[0001] The present invention relates to a vehicle control device.

Background Art

[0002] There is a technique for suppressing over-rotation of an engine by stopping fuel supply when the engine speed reaches a predetermined upper limit speed (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] Even if fuel injection is stopped after the engine speed reaches the upper limit speed, the engine speed may not immediately decrease, and there is a risk that over-rotation of the engine cannot be sufficiently suppressed.

[0005] Therefore, an object of the present invention is to provide a vehicle control device capable of sufficiently suppressing over-rotation of an engine.

Means for Solving the Problems

[0006] The above object can be achieved by a vehicle control device including a prediction unit that predicts whether the engine will over-rotate based on at least one of a predicted engine speed, which is a predicted value of the engine speed of a vehicle-mounted engine, and the engine rotational acceleration, and a control unit that executes torque reduction processing for reducing the torque of the engine when over-rotation of the engine is predicted, more than when over-rotation of the engine is not predicted.

[0007] The prediction unit predicts that the engine will over-rotate if the predicted rotational speed is equal to or greater than a first determination value, if the rotational acceleration is equal to or greater than a second determination value, or if the predicted rotational speed is equal to or greater than the first determination value and the rotational acceleration is equal to or greater than the second determination value. The unit also includes a setting unit that sets the first and second determination values ​​to smaller values ​​the lower the gear position of the transmission provided on the power transmission path between the engine and the drive wheels of the vehicle, and sets the first and second determination values ​​to predetermined values ​​if the transmission is in neutral.

[0008] The setting unit may set the first and second determination values ​​to predetermined values ​​when the clutch provided on the power transmission path is in an open state.

[0009] The prediction unit may predict whether the engine will over-rev if at least one of the following conditions is met: the transmission is not performing gear shift control; the engine is not performing partial cylinder operation, in which combustion is suspended in some cylinders while combustion is performed in the remaining cylinders; and the rotational speed is not below a predetermined value.

[0010] The prediction unit calculates the predicted rotational speed based on the current engine speed and a value obtained by multiplying the current rotational acceleration by a predetermined time, and the predetermined time may be set to be longer than or equal to the delay time from when the torque reduction process is started until the engine speed starts to decrease. [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 over-speed suppression control. [Figure 4] Figure 4A is the map used to set the first judgment value A, and Figure 4B is the map used to set the second judgment value B. [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 prediction unit, control unit, and setting unit, which will be described in more detail later.

[0017] The ECU 20 is connected to a crank angle sensor 21 and a shift position sensor 22. 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 position, R range position, N range position, or D range position.

[0018] Based on the engine speed, intake air volume, and accelerator opening detected by the above sensors, the ECU 20 calculates the required torque and target speed for the engine 10. The ECU 20 controls the fuel injection volume, intake air volume, and ignition timing according to the required torque and target speed. For example, when the engine 10 is in the idle operation state, 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 supply torque. Further, the ECU 20 performs drive control of the clutch 13C and the automatic transmission 14 through the control of the hydraulic control mechanism.

[0019] As described below, when a predetermined condition is satisfied, the ECU 20 executes overspeed suppression control to suppress overspeed of the engine 10. Further, the ECU 20 calculates the rotational acceleration of the engine 10 based on the speed of the engine 10. The rotational acceleration of the engine 10 is used in the overspeed suppression control.

[0020] [Overspeed Suppression Control] FIG. 2 is a flowchart illustrating the overspeed suppression control. This control is continuously repeated while the ignition is on. The ECU 20 determines whether or not a prediction precondition for predicting whether or not the engine 10 will overspeed is satisfied (step S1). If the result in step S1 is No, this control ends. The prediction precondition will be described in detail later.

[0021] If the result in step S1 is Yes, the ECU 20 sets the first determination value A and the second determination value B (step S2). The first determination value A and the second determination value B will be described in detail later. Step S2 is an example of the process executed by the setting unit.

[0022] In step S3, the ECU 20 predicts whether or not the engine 10 will over-rev (step S3). Whether or not the engine 10 will over-rev is determined based on the predicted rotational speed, which is the predicted value of the engine 10's rotational speed, and the rotational acceleration of the engine 10. The predicted rotational speed of the engine 10 is the predicted value of the engine 10's rotational speed after a predetermined time has elapsed from the present (for example, several tens to several hundreds of msec). The predicted rotational speed is calculated, for example, as follows. Predicted rotational speed [rpm] = Detected current engine speed [rpm] + rotational acceleration of engine 10 [rpm / sec] × predetermined time [sec] × gain The predetermined time is set based on factors such as the delay time from when the instruction to execute the torque reduction process (described later) is issued until the torque of the engine 10 actually begins to decrease. Gain is a tuning element.

[0023] The rotational acceleration of the engine 10 can be calculated, for example, as follows, if the ECU 20 samples the values ​​detected by the crank angle sensor 21 every 0.002 seconds. Rotational acceleration [rpm / sec] = {rotational speed (n) - rotational speed (n-1)} / 0.002 The rotational speed (n) is the latest value of the engine 10's rotational speed acquired by the ECU 20, and the rotational speed (n-1) is the previous value of the engine 10's rotational speed acquired by the ECU 20. The rotational acceleration of the engine 10 may also be calculated, for example, as follows. Rotational acceleration [rpm / sec] = {rotational speed (n) - rotational speed (n-3)} / 0.006 The rotational speed (n-3) is the value of the engine 10's rotational speed obtained by the ECU20 three times prior.

[0024] If the predicted rotational speed is greater than or equal to the first determination value A and the rotational acceleration is greater than or equal to the second determination value B, the result in step S3 is determined to be Yes. If the predicted rotational speed is less than the first determination value A, or if the rotational acceleration is less than the second determination value B, the result in step S3 is determined to be No. If the result in step S3 is No, this control process ends. Step S3 is an example of the processing performed by the prediction unit.

[0025] If the answer in step S3 is Yes, the ECU 20 performs a torque reduction process (step S4) that reduces the torque of the engine 10 more than if the answer in step S3 is No. The torque reduction process is achieved, for example, by cutting fuel, retarding the ignition timing, or by cutting fuel in some cylinders of the engine 10 and retarding the ignition timing of the remaining cylinders. This suppresses over-revving of the engine 10. Step S4 is an example of a process performed by the control unit.

[0026] Figure 3 is a timing chart illustrating over-speed suppression control. Figure 3 shows the changes in the actual rotational speed, predicted rotational speed, rotational acceleration, and actual torque of the engine 10 when the accelerator opening is constant. In addition to the values ​​in this embodiment where over-speed of the engine 10 is predicted based on the predicted rotational speed and rotational acceleration, Figure 3 also shows the actual rotational speed and actual torque in a comparative example where over-speed is determined based only on the actual rotational speed.

[0027] First, let's explain the comparative example. When the actual rotational speed of engine 10 exceeds the first judgment value A (time t4), a torque reduction process is executed, and the actual torque of engine 10 decreases (time t5). However, there is a delay between the rotational speed exceeding the first judgment value A and the actual decrease in the actual torque of engine 10. As a result, after time t4, the rotational speed becomes significantly higher than the first judgment value A, causing over-rotation of engine 10. In particular, if the drive wheel 18 slips, the rotational speed may increase sharply, potentially causing such over-rotation.

[0028] In this embodiment, the rotational acceleration becomes greater than or equal to the second determination value B (time t1), and then the predicted rotational speed becomes greater than or equal to the first determination value A (time t2), and the torque reduction process is executed (time t3). As a result, the actual torque of the engine 10 decreases. In this way, the actual torque of the engine 10 is reduced before the actual rotational speed of the engine 10 becomes greater than or equal to the first determination value A, and over-rotation of the engine 10 is sufficiently suppressed.

[0029] Furthermore, as mentioned above, the predicted rotational speed is the predicted value of the engine 10's rotational speed after a predetermined time has elapsed from the present. Here, the predetermined time is preferably set to be at least the delay time from when the torque reduction process starts until the actual rotational speed of the engine 10 begins to decrease. This is because it is possible to reduce the actual rotational speed of the engine 10 before it reaches a rotational speed that indicates over-rotation after the torque reduction process starts.

[0030] [Setting the judgment value] Next, the setting of the first judgment value A and the second judgment value B in step S2 will be explained. Figure 4A is a map used to set the first judgment value A. The lower the gear position in the automatic transmission 14, the lower the value of the first judgment value A is set to. This is because a lower gear position results in a larger rotational acceleration of the drive wheels 18 for a given torque of the engine 10, making it easier for the engine 10 to over-rev. Also, when the automatic transmission 14 is in the N range and when the clutch 13C is disengaged, the first judgment value A is set to a smaller predetermined value than when the automatic transmission 14 is in the N range. Note that the first judgment value A may be a different value when the automatic transmission 14 is in the N range and when the clutch 13C is disengaged.

[0031] Figure 4B is a map used to set the second judgment value B. Similar to the first judgment value A, the lower the gear of the automatic transmission 14, the lower the value of the second judgment value B is set to. When the automatic transmission 14 is in the N range and when the clutch 13C is disengaged, the second judgment value B is set to a predetermined value that is smaller than when a gear is established in the automatic transmission 14. Note that the second judgment value B may be different when the automatic transmission 14 is in the N range and when the clutch 13C is disengaged.

[0032] Thus, the more likely the engine 10 is to over-rev depending on the state of the automatic transmission 14 and the clutch 13C, the lower the first judgment value A and the second judgment value B are set to. This sufficiently suppresses over-revving of the engine 10. The gear position of the automatic transmission 14 may be determined by the ECU 20 based on the gear position command value sent to the automatic transmission 14 by the ECU 20, or it may be detected by a sensor. Whether the automatic transmission 14 is in the N range may be detected by the shift position sensor 22. Whether the clutch 13C is in the disengaged state may be determined by the ECU 20 based on the command value sent to the clutch 13C by the ECU 20, or it may be detected by a sensor.

[0033] Next, the prediction preconditions in step S1 will be explained. In this embodiment, the prediction preconditions require that all of the following conditions be met: (1) the automatic transmission 14 is not performing gear shift control; (2) the engine 10 is not performing partial cylinder operation, in which combustion is suspended in some cylinders while combustion is performed in the remaining cylinders; and (3) the rotational speed of the engine 10 is not below a predetermined value.

[0034] Condition (1) is to avoid erroneous predictions under conditions where, for example, the rotational acceleration may be intentionally controlled to be high by blipping or downshifting during gear shifting by the automatic transmission 14. Condition (2) is because the torque of the engine 10 is low in partial cylinder operation, and there is little risk of over-revving. The predetermined value in condition (3) is set to a low rotational speed at which there is no risk of over-revving of the engine 10. Condition (3) is because there is little need to predict over-revving when there is no risk of over-revving.

[0035] However, the prediction assumptions are not limited to cases where all of the above conditions (1), (2), and (3) are met. For example, the prediction assumptions may be deemed to be true if at least one of conditions (1), (2), and (3) is met.

[0036] In step S3 shown in the flowchart of Figure 2, over-rotation of engine 10 is predicted when the predicted rotational speed is greater than or equal to the first determination value A and the rotational acceleration is greater than or equal to the second determination value B, but this is not limited to this. For example, over-rotation may be predicted when the predicted rotational speed is greater than or equal to the first determination value A or the rotational acceleration is greater than or equal to the second determination value B. In this case, if the predicted rotational speed is less than the first determination value A and the rotational acceleration is less than the second determination value B, over-rotation is not predicted. Alternatively, over-rotation may be predicted when the predicted rotational speed is greater than or equal to the first determination value A, without using rotational acceleration. In this case, over-rotation is not predicted when the predicted rotational speed is less than the first determination value A. Alternatively, over-rotation may be predicted when the rotational acceleration is greater than or equal to the second determination value B, without using the predicted rotational speed. In this case, over-rotation is not predicted when the rotational acceleration is less than the second determination value B. This is because by using at least one of the predicted rotational speed and rotational acceleration, it is possible to predict over-rotation of engine 10 before the actual rotational speed of engine 10 reaches a rotational speed that indicates over-rotation.

[0037] 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 an engine and a motor as driving power sources may also be used. In the case of a hybrid vehicle, torque reduction processing may be achieved, for example, by regenerating the motor so that the torque in the opposite direction to the engine's rotation direction increases.

[0038] In vehicles equipped with a manual transmission instead of an automatic transmission 14, the first judgment value A and the second judgment value B are set to predetermined values ​​when the manual transmission is in neutral or when the clutch pedal is operated and the clutch is disengaged.

[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 13C Clutch 14 Automatic transmission 20 ECU (Vehicle control unit, prediction unit, control unit, setting unit)

Claims

1. A prediction unit predicts whether or not the engine will over-rotate based on a predicted rotational speed, which is a predicted value of the rotational speed of the engine mounted on the vehicle, and at least one of the rotational acceleration of the engine. A control unit that, when over-rotation of the engine is predicted, performs a torque reduction process to reduce the torque of the engine compared to when over-rotation of the engine is not predicted, A vehicle control device equipped with the following features.

2. The prediction unit predicts that the engine will over-rotate if the predicted rotational speed is equal to or greater than a first determination value, if the rotational acceleration is equal to or greater than a second determination value, or if the predicted rotational speed is equal to or greater than the first determination value and the rotational acceleration is equal to or greater than the second determination value. The vehicle control device according to claim 1, further comprising a setting unit that sets the first and second determination values ​​to smaller values ​​as the gear position of the transmission provided on the power transmission path between the engine and the drive wheels of the vehicle decreases, and sets the first and second determination values ​​to predetermined values ​​when the transmission is in neutral range.

3. The vehicle control device according to claim 2, wherein the setting unit sets the first and second determination values ​​to predetermined values ​​when the clutch provided on the power transmission path is in an open state.

4. The vehicle control device according to claim 2 or 3, wherein the prediction unit predicts whether the engine will over-rev when at least one of the following conditions is met: the transmission is not performing gear shift control; the engine is not performing partial cylinder operation, in which combustion is suspended in some cylinders while combustion is performed in the remaining cylinders; and the rotational speed is not below a predetermined value.

5. The prediction unit calculates the predicted rotational speed based on the current engine speed and a value obtained by multiplying the current rotational acceleration by a predetermined time. The vehicle control device according to any one of claims 1 to 3, wherein the predetermined time is set to be longer than or equal to the delay time from when the torque reduction process is started until the engine speed starts to decrease.

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