Vehicle control device

Abstract

To provide a control device of a vehicle which can restrain vibration.SOLUTION: A control device of a vehicle, in which output torque of a drive power source is transmitted to driving wheels via a non-stage transmission and a drive shaft, comprises: a detection part which detects switching from on-accelerator to off-accelerator; a prediction part which, upon the detection part detecting the switching from the on-accelerator to the off-accelerator, predicts a transmission gear ratio of the non-stage transmission as of when the output torque functions, as a requested torque corresponded to the off-accelerator; a calculation part which calculates an inverse number of a resonant frequency generated at the transmission gear ratio predicted by the prediction part, of a drive system which contains from the drive power source to the drive shaft; and a control part which controls the drive power source so that a torque falling time period becomes the inverse number of the resonant frequency, the torque falling time period ranging from when the switching from the on-accelerator to the off-accelerator is detected by the detection part until when the output torque becomes the requested torque.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] There is a technique for suppressing vibrations of a vehicle by setting the inverse of the resonance frequency of a drive system including a drive power source and a transmission as the torque fall time of the drive power source (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-099059 A Summary of the Invention [Problem to be solved by the invention]

[0004] If the transmission is a continuously variable transmission, the gear ratio changes continuously even during torque ramp-down. If the inverse of the resonance frequency is used as the torque ramp-down time without taking such gear ratio into consideration, there is a risk that vibrations cannot be sufficiently suppressed.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a vehicle control device capable of suppressing vibrations. [Means for solving the problem]

[0006] The above object can be achieved by a vehicle control device in which the output torque of a driving force source is transmitted to drive wheels via a continuously variable transmission and a drive shaft, the vehicle control device including: a detection unit that detects switching from accelerator on to accelerator off; a prediction unit that predicts a gear ratio of the continuously variable transmission when the detection unit detects switching from accelerator on to accelerator off and the output torque becomes a required torque corresponding to accelerator off; a calculation unit that calculates the reciprocal of a resonance frequency of the drive system including the driving force source to the drive shaft generated at the gear ratio predicted by the prediction unit; and a control unit that controls the driving force source so that the torque fall time from when the detection unit detects switching from accelerator on to accelerator off until the output torque becomes the required torque is the reciprocal of the resonance frequency. Effect of the Invention

[0007] According to the present invention, a vehicle control device capable of suppressing vibrations can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a vehicle according to this embodiment. [Diagram 2] FIG. 2 is a graph showing the relationship between vibration strength and frequency. [Diagram 3] FIG. 3 is a graph showing the relationship between the drive shaft torque and the torque fall time. [Figure 4] FIG. 4 is an example of a timing chart showing changes in the accelerator opening, the gear ratio, and the engine torque. [Diagram 5] FIG. 5 is a flowchart showing an example of vibration suppression control executed by the ECU. [Figure 6] FIG. 6A is an example of a map that defines the relationship between the gear ratio and the resonance frequency, and FIG. 6B is a map that defines the relationship between the resonance frequency and the torque fall time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Vehicle outline] Fig. 1 is a block diagram showing a schematic configuration of a vehicle 1 according to this embodiment. As shown in Fig. 1, the vehicle 1 includes an engine (ENG) 10, a torque converter (T / C) 20, a continuously variable transmission (CVT) 30, a hydraulic control circuit 35, a differential gear 41, a drive shaft 43, driving wheels 45, and an ECU (Electronic Control Unit) 50.

[0010] 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 thereto and may be a diesel engine. Torque of the engine 10 is transmitted to drive wheels 45 through a torque converter 20 and a continuously variable transmission 30.

[0011] The torque converter 20 is a fluid power transmission device, and 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.

[0012] 1, the continuously variable transmission 30 is disposed on the same axis as the engine 10, and transmits torque between the engine 10 and drive wheels 45. The continuously variable transmission 30 can continuously change the gear ratio, which is the ratio of the input rotation speed to the output rotation speed. Specifically, the hydraulic control circuit 35 controlled by the ECU 50 changes the groove width of the input side pulley and the output side pulley, thereby changing the wrapping diameter of the transmission belt, thereby changing the gear ratio.

[0013] A differential gear 41, which is a final reduction gear, is connected to the output shaft 31 of the continuously variable 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 continuously variable 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.

[0014] 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 supply source, and supplies hydraulic pressure to the torque converter 20 and the continuously variable transmission 30 to control the operations of these. In addition, a hydraulic pressure command value output from the ECU 50 is input to the hydraulic control circuit 35, and the hydraulic pressures supplied to the torque converter 20 and the continuously variable transmission 30 are controlled based on the hydraulic pressure command value.

[0015] 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 the various control programs are executed. The CPU performs calculation processing based on the various control programs and maps stored in the ROM. The RAM is a memory that 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 to be saved when the ignition is turned off. The CPU, ROM, RAM, and backup RAM functionally realize a detection unit, a prediction unit, a calculation unit, and a control unit, which will be described in detail later.

[0016] Various sensors and switches, such as an ignition switch 60, a crank angle sensor 61, an accelerator opening 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 continuously variable transmission 30 based on the detection results of the various sensors.

[0017] [Relationship between resonance frequency and torque fall time] In the vehicle 1 configured as described above, the drive system from the engine 10 to the drive shaft 43 may resonate due to torque fluctuations of the engine 10. FIG. 2 is a graph showing the relationship between vibration intensity [dB] and frequency [Hz]. The vertical axis shows vibration intensity, and the horizontal axis shows frequency. In FIG. 2, the case of a gear ratio γ0 of the continuously variable transmission 30 is shown by a dotted line, and the case of a gear ratio γ1 smaller than the gear ratio γ0 is shown by a solid line. The frequency at the peak value of the vibration intensity is the resonance frequency. As shown in FIG. 2, the resonance frequency f0 at the gear ratio γ0 is lower than the resonance frequency f1 at the gear ratio γ1. That is, the smaller the gear ratio, the higher the resonance frequency tends to be. This is because the smaller the gear ratio, the smaller the difference in the rotation speed of the drive shaft 43 relative to the engine rotation speed, which is equivalent to a high rigidity of the drive system from the crankshaft of the engine 10 to the drive shaft 43. Incidentally, in the case of the continuously variable transmission 30, the gear ratio is controlled to be small at low vehicle speeds, and the gear ratio is controlled to be large at high vehicle speeds.

[0018] The torque of the engine 10 falls when the accelerator is switched from on to off, and vibrations due to resonance as described above may occur. The torque of the drive shaft 43 when the torque falls (hereinafter referred to as drive shaft torque) varies depending on the torque fall time. If the variation in the drive shaft torque is large, the vehicle 1 vibrates. The torque fall time is the time from when the ECU 50 detects that the accelerator has been switched from on to off until the torque of the engine 10 becomes the required torque corresponding to the accelerator being off.

[0019] Figure 3 is a graph showing the relationship between drive shaft torque [N·m] and torque fall time [s]. The vertical axis shows drive shaft torque, and the horizontal axis shows torque fall time. As shown in Figure 3, the drive shaft torque has a waveform that takes the absolute value of a sine wave, and it is known that the drive shaft torque becomes zero when the torque fall time is an integer multiple of the reciprocal of the resonance frequency. Specifically, when the gear ratio is γ0, the drive shaft torque becomes zero when the torque fall time is (1 / f0), (2 / f0), (3 / f0)…. Similarly, when the gear ratio is γ1, the drive shaft torque becomes zero when the torque fall time is (1 / f1), (2 / f1), (3 / f1)…. The shortest torque fall time at which the drive shaft torque becomes zero at the gear ratios γ0 and γ1 is (1 / f0) and (1 / f1), respectively, and (1 / f1)<(1 / f0) is established. It should be noted that the peak value of the drive shaft torque adjacent to the speed ratios γ0 and γ1 is smaller for the speed ratio γ1 than for the speed ratio γ0.

[0020] 3 shows torque D0 when the torque fall time is (1 / f0) for a gear ratio of γ0, and torque D1 when the torque fall time is (1 / f0) for a gear ratio of γ1. Torque D0 is zero, and torque D1 is a value greater than torque D0. Details will be described later.

[0021] [Setting torque fall time taking into account gear ratio transitions] FIG. 4 is an example of a timing chart showing the transition of the accelerator opening [deg], the gear ratio [-], and the engine torque [N·m]. The engine torque is an example of the output torque of the driving force source. For ease of understanding, FIG. 4 illustrates an example in which the torque is reduced from the above-mentioned gear ratio γ0 to the gear ratio γ1 due to a torque drop. At time t0, the vehicle is traveling at a specified accelerator opening with the gear ratio being γ0. When the accelerator is released at time t1, the gear ratio gradually decreases together with the engine torque. Eventually, the engine torque decreases to a specified deceleration torque corresponding to the accelerator being released, and the gear ratio decreases to the gear ratio γ1.

[0022] Here, a comparative example shown in Fig. 4 will be described. In the comparative example, the torque fall time is set to (1 / f0) based on the gear ratio γ0 at time t1 when the accelerator is released. Therefore, at time t3, which is (1 / f0) after time t1, the engine torque becomes the backlash elimination start torque, and the gear ratio drops from the gear ratio γ0 to the gear ratio γ1. In other words, the gear ratio when the engine torque becomes the backlash elimination start torque is not the gear ratio γ0 but the gear ratio γ1. Therefore, in the comparative example, when the engine torque becomes the backlash elimination start torque, the torque D1 shown in Fig. 3 is generated in the drive shaft 43, and the vibration of the vehicle 1 increases.

[0023] In this embodiment, the gear ratio when the engine torque becomes the backlash elimination start torque at time t1 is predicted to be γ1, and the torque fall time is set to (1 / f1) based on the gear ratio γ1. Therefore, in this embodiment, the engine torque becomes the backlash elimination start torque at time t2, which is (1 / f1) after time t1. The drive shaft torque at this time is zero, as shown in FIG. 3. In this manner, vibration is suppressed.

[0024] [Vibration suppression control] 5 is a flowchart showing an example of vibration suppression control executed by the ECU 50. This control is repeatedly executed with the ignition on. The ECU 50 determines whether or not it has detected a change from accelerator on to accelerator off (step S1). If the answer is No in step S1, this control ends. Step S1 is an example of a process executed by the detection unit.

[0025] If the answer is Yes in step S1, the ECU 50 predicts the gear ratio when the engine torque becomes the required torque corresponding to the accelerator being released (step S2). Specifically, the ECU 50 predicts the above-mentioned gear ratio as the target gear ratio set based on the detection of the accelerator being released. The target gear ratio is set based on the current output shaft rotation speed and the target engine rotation speed. Note that the method of predicting the gear ratio is not limited to this. For example, the gear ratio may be predicted by referring to a map of suitable values ​​experimentally calculated based on the current output shaft rotation speed and the target engine rotation speed. Step S2 is an example of a process executed by the prediction unit.

[0026] Next, the ECU 50 calculates the resonance frequency based on the predicted gear ratio (step S3). Fig. 6A is an example of a map that specifies the relationship between the gear ratio and the resonance frequency. As described above, this map specifies that the smaller the gear ratio is, the higher the resonance frequency is. This map is calculated in advance by experiments and is stored in the memory of the ECU 50. The ECU 50 calculates the resonance frequency by referring to this map.

[0027] Next, the ECU 50 calculates the torque fall time based on the calculated resonance frequency (step S4). FIG. 6B is a map that specifies the resonance frequency and the torque fall time. As described above, this map specifies that the torque fall time is shorter as the resonance frequency is higher. This map is stored in advance in the memory of the ECU 50. The ECU 50 calculates the torque fall time by referring to this map. Steps S3 and S4 are an example of a process executed by the calculation unit. As described above, the torque fall time is the reciprocal of the resonance frequency, and therefore it may be calculated by calculation without referring to the map.

[0028] Next, the ECU 50 reduces the engine torque so that the engine torque becomes the required torque corresponding to the accelerator release when the torque fall time has elapsed since the accelerator release is detected (step S5). For example, the ECU 50 adjusts the reduction amount of the intake air amount of the engine 10 and the retard amount of the ignition timing to reduce the engine torque so that the engine torque becomes the required torque after the torque fall time has elapsed since the accelerator release. Step S5 is an example of a process executed by the control unit.

[0029] In the above embodiment, the ECU 50 is a control device for the 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 be applied to a control device for an electric vehicle having a motor as a driving force source, or a control device for a hybrid vehicle having an engine and a motor as driving force sources.

[0030] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0031] 10 Engine 50 ECU (control device, detection unit, prediction unit, calculation unit, control unit)

Claims

[Claim 1] A control device for a vehicle in which output torque of a driving force source is transmitted to driving wheels via a continuously variable transmission and a drive shaft, A detection unit that detects a change from an accelerator on to an accelerator off; a prediction unit that predicts a gear ratio of the continuously variable transmission when the output torque becomes a required torque corresponding to the accelerator being off, when the detection unit detects a switch from an accelerator being on to an accelerator being off; a calculation unit that calculates an inverse of a resonance frequency of a drive system including the drive force source and the drive shaft, the resonance frequency being generated at the gear ratio predicted by the prediction unit; a control unit that controls the driving force source so that a torque fall time from when the detection unit detects a switch from accelerator on to accelerator off until the output torque becomes the required torque is the reciprocal of the resonance frequency.

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