Vehicle control device

Abstract

To provide a vehicle control device that suppresses vibrations and shocks caused by switching from accelerator ON to accelerator OFF.SOLUTION: A vehicle control device acquires command torque when accelerator is switched from ON to OFF, executes a vibration suppression process to reduce the command torque so that time from the switching from accelerator ON to accelerator OFF until the command torque decreases to initial torque at which a shock suppression process is started corresponds to an inverse of a resonant frequency of a drive system including a drive source to a drive shaft, executes a shock suppression process to reduce the command torque with a reduced descending slope relative to the vibration suppression process, from when the command torque reaches the initial torque until the same reaches ending torque smaller in value than the initial torque, and sets the initial torque and the ending torque to lower values and sets the descending slope of the command torque in the shock suppression process to be reduced as the acquired command torque becomes smaller.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] There is a technology that suppresses vehicle vibrations by setting the time during which the output torque of the driving force source decreases when the accelerator is switched from on to off to the inverse of the resonance frequency of the drive system, including the driving force source and the drive shaft (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-076929 Summary of the Invention [Problem to be solved by the invention]

[0004] When the output torque of the driving force source decreases, the torque applied to the driving force source in the reverse direction from an external source becomes greater than the output torque in the forward direction, causing the gears in the drive train to switch from a driving state to a driven state. At this time, gear backlash may cause a shock to the vehicle. Furthermore, if the response to the decrease in output torque when switching from accelerator on to accelerator off is poor, drivability may be reduced.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a vehicle control device that ensures drivability while suppressing the occurrence of vibrations and shocks caused by switching from accelerator on to accelerator off. [Means for solving the problem]

[0006] The above object can be achieved by a vehicle control device that is applied to a vehicle in which the output torque of a driving force source corresponding to a command torque to the driving force source is transmitted to a drive wheel via a drive shaft, and that reduces the command torque when the accelerator is switched from on to off, the vehicle control device comprising: an acquisition unit that acquires the command torque when the accelerator is switched from on to off; a vibration suppression control unit that executes a vibration suppression process that reduces the command torque so that the time it takes for the command torque to decrease from when the accelerator is switched from on to off to a start torque at which shock suppression processing begins is the reciprocal of the resonance frequency of the drive system including the driving force source to the drive shaft; a shock suppression control unit that executes the shock suppression process that reduces the command torque at a decrease gradient that is gentler than the decrease gradient of the command torque in the vibration suppression process from when the command torque becomes the start torque until it becomes an end torque that is lower than the start torque; and a setting unit that sets the start torque and end torque to lower values ​​as the command torque acquired by the acquisition unit is smaller, and sets the decrease gradient of the command torque in the shock suppression processing to be gentler.

[0007] The setting unit may set the start torque and the end torque so that a difference between the start torque and the end torque is a constant value, regardless of the magnitude of the command torque acquired by the acquisition unit.

[0008] The setting unit may variably set the starting torque from a positive value to a negative value. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a vehicle control device that ensures drivability while suppressing the occurrence of vibrations and shocks caused by switching from accelerator on to accelerator off. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a vehicle. [Figure 2]FIG. 2 is a flowchart illustrating the deceleration control executed by the ECU. [Figure 3] FIG. 3 is a timing chart illustrating the deceleration control. [Figure 4] FIG. 4A is an example of a map that defines the relationship between the initial value of the command torque and the start torque and end torque, and FIG. 4B is an example of a map that defines the relationship between the initial value of the command torque and the decrease gradient in the shock suppression process. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Vehicle outline] 1 is a schematic configuration diagram of a vehicle 1. The vehicle 1 includes an engine (ENG) 10, a torque converter (T / C) 20, an automatic transmission (A / T) 30, a hydraulic control circuit 35, a differential gear 41, a drive shaft 43, drive wheels 45, and an ECU (Electronic Control Unit) 50.

[0012] The engine 10 is a driving force source for the vehicle 1. The engine 10 is a gasoline engine, which is an example of an internal combustion engine, but is not limited to this and may be a diesel engine. The output torque of the engine 10 is transmitted to drive wheels 45 via a torque converter 20 and an automatic transmission 30.

[0013] The torque converter 20 is a fluid power transmission device that includes a pump impeller directly or indirectly connected to the crankshaft of the engine 10 described above, and a turbine runner connected to the input shaft of the torque converter 20. The torque converter 20 transmits torque, which is power, from the pump impeller side to the turbine runner side via oil while increasing the torque.

[0014] As shown in FIG. 1, the automatic transmission 30 is disposed on the same axis as the engine 10 and transmits torque between the engine 10 and drive wheels 45. The automatic transmission 30 is a stepped transmission that can change the gear ratio, which is the ratio of input rotation speed to output rotation speed. Specifically, a hydraulic control circuit 35 controlled by the ECU 50 engages or disengages multiple friction engagement elements. Note that a stepped manual transmission or a continuously variable transmission that continuously changes the gear ratio may be employed instead of the automatic transmission 30.

[0015] A differential gear 41, which is a final reduction gear, is connected to the output shaft 31 of the automatic transmission 30, and torque is transmitted to drive wheels 45 via a drive shaft 43 connected to the differential gear 41. The drive wheels 45 generate driving force on the road surface using the power of the engine 10 transmitted from the torque converter 20 and the automatic transmission 30, causing the vehicle 1 to travel. The drive wheels 45 may be the left and right front wheels, the left and right rear wheels, or both.

[0016] The hydraulic control circuit 35 is a known hydraulic control circuit that uses a mechanical oil pump driven by the engine 10 as a hydraulic pressure supply source, and supplies hydraulic pressure to the torque converter 20 and the automatic transmission 30 to control their respective operations. In addition, hydraulic pressure command values ​​output from the ECU 50 are input to the hydraulic control circuit 35, and the hydraulic pressures supplied to the torque converter 20 and the automatic transmission 30 are controlled based on the hydraulic pressure command values.

[0017] The ECU 50 is an electronic control unit that performs control processing for the vehicle 1. The ECU 50 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a backup RAM. The ROM stores various control programs and maps that are referenced when executing the various control programs. The CPU performs calculations based on the various control programs and maps stored in the ROM. The RAM temporarily stores the results of calculations performed by the CPU and data input from each sensor, and the backup RAM is a non-volatile memory that stores data that should be saved when the ignition is turned off, for example. The CPU, ROM, RAM, and backup RAM functionally implement an acquisition unit, a vibration suppression control unit, a shock suppression control unit, and a setting unit, which will be described in detail later.

[0018] Various sensors and switches, such as an ignition switch 60, a crank angle sensor 61, an accelerator pedal position sensor 62, and an output shaft rotation speed sensor 63, are connected to the ECU 50, and signals from these sensors and switches are input to the ECU 50. The ECU 50 controls the operating state of the engine 10 and the gear ratio of the automatic transmission 30 based on the detection results of the various sensors. The ECU 50 calculates a command torque that the engine 10 should output in accordance with the operating state of the engine 10 and the accelerator pedal position, and controls the engine 10 so that the output torque of the engine 10 becomes the command torque. Specifically, the ECU 50 controls the output torque of the engine 10 to become the command torque by adjusting the amount of reduction in the intake air amount of the engine 10, the amount of retardation of the ignition timing, the amount of reduction in the fuel injection amount, etc.

[0019] [Vibration suppression processing] The ECU 50 executes deceleration control to decelerate the vehicle 1 by switching from accelerator on to accelerator off. Specifically, the ECU 50 reduces the output torque of the engine 10. This reduction in the output torque of the engine 10 may cause the torque of the drive shaft 43 to fluctuate, causing the drive system from the engine 10 to the drive shaft 43 to resonate. For this reason, the ECU 50 reduces the command torque of the engine 10 so that the reduction time of the command torque becomes the reciprocal (1 / f) of the resonance frequency f of the drive system. This suppresses the fluctuation in the torque of the drive shaft 43 and suppresses vibration of the vehicle 1. The ECU 50 executes this vibration suppression process.

[0020] [Shock suppression processing] When the output torque of the engine 10 is reduced by the deceleration control, the torque in the reverse rotation direction applied to the engine 10 from the drive wheels 45 via the drive shaft 43, etc., becomes greater than the output torque of the engine 10 in the forward rotation direction. This can cause teeth to strike due to backlash in the drive system including the engine 10 to the drive shaft 43, for example, the differential gear 41, and can cause a shock to the vehicle 1. For this reason, when the command torque to the engine 10 decreases to near zero, the ECU 50 reduces the command torque at a gradient that is gentler than the gradient at which the command torque is reduced in the vibration suppression process. This suppresses the occurrence of a shock due to gear backlash. The ECU 50 executes this shock suppression process.

[0021] [Deceleration control] FIG. 2 is a flowchart illustrating deceleration control executed by the ECU 50. This control is repeatedly executed with the ignition on. The ECU 50 determines whether the accelerator has been switched from on to off (step S1). For example, the ECU 50 determines that the accelerator has been switched from on to off when the difference between the required driving torque to the engine 10, which decreases in response to the accelerator being off, and the command torque to the engine 10 is equal to or greater than a predetermined value for a predetermined time or longer. If the result in step S1 is No, this control ends. Step S1 is an example of processing executed by the determination unit.

[0022] If the result of step S1 is Yes, the ECU 50 acquires the command torque (step S2). Hereinafter, the command torque acquired in step S2 will be referred to as the command torque initial value. Step S2 is an example of a process executed by the acquisition unit.

[0023] Next, the ECU 50 sets a start torque, an end torque, and a decrease gradient according to the command torque initial value (step S3). The start torque, the end torque, and the decrease gradient are torque values ​​used to execute the shock suppression process. Details will be described later. Step S3 is an example of a process executed by the setting unit.

[0024] Next, the ECU 50 executes vibration suppression processing (step S4). In the vibration suppression processing, the command torque is reduced so that the time it takes for the command torque to decrease from the command torque initial value to the shock suppression processing start torque is the reciprocal of the resonance frequency f (1 / f). The ECU 50 calculates the reciprocal of the resonance frequency f (1 / f) by referring to a map that defines, for example, that the smaller the gear ratio of the automatic transmission 30, the higher the resonance frequency f. Step S4 is an example of processing executed by the vibration suppression control unit.

[0025] Next, the ECU 50 determines whether the command torque has decreased to the start torque (step S5). If the answer is No in step S5, step S4 continues. If the answer is Yes in step S5, the ECU 50 executes shock suppression processing (step S6). In the shock suppression processing, the command torque is decreased at the decreasing gradient set in step S3. Step S6 is an example of processing executed by the shock suppression control unit.

[0026] Next, the ECU 50 determines whether the command torque has decreased to the end torque (step S7). If the answer is No in step S7, step S6 continues. If the answer is Yes in step S7, the ECU 50 ends the shock suppression processing (step S8). After the shock suppression processing ends, the ECU 50 reduces the command torque to a predetermined minimum value at a decreasing gradient greater than the decreasing gradient in the shock suppression processing.

[0027] Figure 3 is a timing chart illustrating deceleration control. In Figure 3, the solid line indicates the transition of the commanded torque when the initial value of the commanded torque is a relatively large value Q1. The dotted line indicates the transition of the commanded torque when the initial value of the commanded torque is a relatively small value Q2 (<Q1). When the accelerator is switched from on to off, the vibration suppression process is executed (time t1). When the time of the reciprocal of the resonance frequency f (1 / f) has elapsed from time t1, the shock suppression process is started (time t2).

[0028] Here, when the initial value of the commanded torque is the value Q1, the starting torque is set to the value D1, the ending torque is set to the value E1, and the decreasing gradient is set to R1. When the initial value of the commanded torque is the value Q2, the starting torque is set to the value D2, the ending torque is set to the value E2, and the decreasing gradient is set to R2. The value E1 is smaller than the value D1. The value E2 is smaller than the value D2. The value D2 is smaller than the value D1. The value E2 is smaller than the value E1. R2 is gentler than R1. The values D1 and E1 are positive values. The values D2 and E2 are negative values.

[0029] Figure 4A is an exemplary diagram of a map defining the relationship between the initial value of the commanded torque and the starting torque and the ending torque. Figure 4B is an exemplary diagram of a map defining the relationship between the initial value of the commanded torque and the decreasing gradient in the shock suppression process. The ECU 50 refers to these maps to set the starting torque, the ending torque, and the decreasing gradient. Thus, the smaller the initial value of the commanded torque, the smaller the values to which the starting torque, the ending torque, and the decreasing gradient are set.

[0030] Therefore, if the initial command torque value is Q1, the shock suppression process ends when the command torque reaches E1 as shown in FIG. 3 (time t3). If the initial command torque value is Q2, the shock suppression process ends when the command torque reaches E2 (time t4). The start torque, end torque, and decrease gradient may be calculated using an arithmetic expression that uses the initial command torque value as an argument. If the command torque is a negative value, this means that braking torque is being requested of the engine 10. The engine 10 can generate braking torque by, for example, cutting fuel.

[0031] As shown in Figures 3 and 4A, the smaller the initial command torque value, the smaller the starting torque is set to. For example, if the starting torque is set to a value D2 regardless of the initial command torque value, the command torque at time t2 will be D2 if the initial command torque value is Q1. This may result in large torque fluctuations in the drive shaft 43, which may cause gear tooth strike to be insufficiently suppressed, resulting in shock. Furthermore, for example, if the starting torque is set to a value D1 regardless of the initial command torque value, the command torque at time t2 will be D1 if the initial command torque value is Q2. This may result in an insufficient decrease in command torque, which may reduce deceleration responsiveness and degrade drivability.

[0032] In this embodiment, the smaller the initial command torque value, the smaller the start torque is set to. For example, when the initial command torque value is Q1, the start torque is set to a positive value D1. This limits the decrease in command torque when the command torque is relatively high, thereby suppressing the occurrence of shock. When the initial command torque value is Q2, the start torque is set to a negative value D2. This allows the command torque to be sufficiently decreased while the vibration suppression process is being executed, ensuring drivability.

[0033] Furthermore, for example, if the start torque is set to a smaller value as the initial command torque value becomes smaller, and the end torque is set to a constant value regardless of the initial command torque value, the following problems may occur. When the initial command torque value is Q1, the execution period of the shock suppression process may become long, which may result in a decrease in drivability. Also, when the initial command torque value is Q2, the execution period of the shock suppression process may become short, which may result in an insufficient suppression of shock. In this embodiment, like the start torque, the end torque is set to a smaller value as the initial command torque value becomes smaller. This ensures drivability while suppressing the occurrence of shock.

[0034] Furthermore, even if the decrease gradient is a constant value regardless of the initial command torque value, as in the case described above, there is a risk that the execution period of the shock reduction process will be long when the initial command torque value is Q1, and that the execution period of the shock reduction process will be short when the initial command torque value is Q2. In this embodiment, the decrease gradient in the shock reduction process is set to a smaller value as the initial command torque value becomes smaller. As a result, when the initial command torque value is Q1, the decrease in drivability can be suppressed, and when the initial command torque value is Q2, the occurrence of shock can be sufficiently suppressed.

[0035] In this embodiment, as shown in FIG. 4A, the range from value D1 to value E1 is the same as the range from value D2 to value E2. That is, the torque section in which the shock suppression process is executed is constant regardless of the initial command torque value. Therefore, by setting the decrease gradient to a smaller value as the initial command torque value becomes smaller, the optimal execution period of the shock suppression process according to the initial command torque value is ensured. This ensures drivability while suppressing the occurrence of shock.

[0036] In this embodiment, the value D1 is a positive value and the value D2 is a negative value. That is, as shown in FIG. 4A, the starting torque is variably set within a range from a positive value to a negative value. As a result, when the initial command torque value is a relatively large value Q1, the shock suppression process is started early, thereby suppressing the occurrence of shock. When the initial command torque value is a relatively small value Q2, the initial command torque value itself is small, so that the occurrence of shock can be sufficiently suppressed even if the shock suppression process is started with a small command torque value, and drivability is also ensured by reducing the command torque early.

[0037] As described above, the vibration suppression process and the shock suppression process are executed when the accelerator is switched from on to off, thereby ensuring drivability while suppressing the occurrence of vibrations and shocks.

[0038] In the above embodiment, the ECU 50 is a vehicle control device for a vehicle 1 whose driving force source is the engine 10, but the present invention is not limited to this. For example, the contents of the above embodiment can also be applied to a vehicle control device for an electric vehicle equipped with a motor as a driving force source, or a vehicle control device for a hybrid vehicle equipped with an engine and a motor as driving force sources. In the case of a hybrid vehicle, the engine and the motor may be controlled so that the sum of the engine output torque and the motor output torque becomes the command torque.

[0039] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0040] 10 Engine 43 Drive shaft 50 ECU (controller, acquisition unit, vibration suppression control unit, shock suppression control unit, setting unit)

Claims

1. A vehicle control device is applied to a vehicle in which an output torque of a driving force source corresponding to a command torque to the driving force source is transmitted to driving wheels via a drive shaft, and the vehicle control device reduces the command torque when an accelerator pedal is switched from ON to OFF, an acquisition unit that acquires the command torque when the accelerator is switched from ON to OFF; a vibration suppression control unit that executes vibration suppression processing to reduce the command torque so that the time it takes for the command torque to decrease from an accelerator-on state to a start torque that starts shock suppression processing after the accelerator is switched from on to off is the reciprocal of a resonance frequency of a drivetrain that includes the drive power source and the drive shaft; a shock suppression control unit that executes the shock suppression process to reduce the command torque at a gentler decrease gradient than the decrease gradient of the command torque in the vibration suppression process from when the command torque becomes the start torque until the command torque becomes an end torque that is lower than the start torque; A vehicle control device comprising: a setting unit that sets the start torque and end torque to lower values ​​as the command torque acquired by the acquisition unit becomes smaller, and that sets a gentler gradient of decrease in the command torque during the shock suppression processing.

2. The vehicle control device according to claim 1 , wherein the setting unit sets the start torque and the end torque so that a difference between the start torque and the end torque is a constant value, regardless of the magnitude of the command torque acquired by the acquisition unit.

3. The vehicle control device according to claim 2 , wherein the setting unit variably sets the starting torque from a positive value to a negative value.

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