Control device for vehicle

Abstract

To provide a control device for a vehicle, allowing a front wheel side motor and a rear wheel side motor to switch a torque direction at the same timing.SOLUTION: When vehicle total torque, as combined torque of front wheel driving torque and rear wheel driving torque, is in a low torque region lower than a prescribed threshold T (th), a control section sets a front-rear torque distribution rate to a basic distribution rate in which the front wheel driving torque and the rear wheel driving torque are equal, and sets each of a torque change rate of the front wheel driving torque and a torque change rate of the rear wheel driving torque to almost the same value. When the vehicle total torque is in a high torque region equal to or higher than the prescribed threshold T (th), the control section sets the front-rear torque distribution rate to a distribution rate different from the basic distribution rate, and sets each of the torque change rate of the front wheel driving torque and the torque change rate of the rear wheel driving torque to a different value. As the vehicle total torque comes closer to a border with the low torque region in the high torque region, the control section sets the front-rear torque distribution rate closer to the basic distribution rate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 describes torque distribution control for an electric four-wheel drive vehicle that runs by applying motor torque to some or all of the four wheels. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2023 / 148860 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology described in Patent Document 1 has a problem in that when the magnitude of the front wheel drive torque differs from the magnitude of the rear wheel drive torque, the timing of the zero torque crossing, where the torque direction switches, differs between the front wheel motor and the rear wheel motor. For example, when the front wheel motor and the rear wheel motor have different maximum motor torques or maximum outputs, the timing of the zero torque crossing will differ between the front wheel motor and the rear wheel motor when tipping out from the high torque range corresponding to a high accelerator opening (switching from power running to regeneration).

[0005] If the timing of the zero torque crossing is different, the front wheel drive torque and rear wheel drive torque will be divided into power running and regeneration, resulting in unstable driving.On the other hand, if the timing of the zero torque crossing is adjusted so that one of the front wheel motor or rear wheel motor reaches near 0 Nm first and then the other motor reaches approximately 0 Nm, the jerk, which is the rate of change in torque acceleration, will change unintentionally, resulting in a deterioration in drivability.

[0006] The present invention has been made in light of the above-mentioned circumstances, and aims to provide a vehicle control device that can switch the torque direction of the front wheel motor and the rear wheel motor at the same time. [Means for solving the problem]

[0007] The present invention provides a vehicle control device mounted on a vehicle including a front-wheel motor that outputs front-wheel drive torque to front wheels and a rear-wheel motor that outputs rear-wheel drive torque to rear wheels, the vehicle control device including a control unit that sets a front-rear torque distribution ratio, which is a distribution ratio between the front-wheel drive torque and the rear-wheel drive torque, and controls the front-wheel motor and the rear-wheel motor based on the front-rear torque distribution ratio, and when an overall vehicle torque, which is a sum of the front-wheel drive torque and the rear-wheel drive torque, is in a low torque region less than a predetermined threshold, the control unit sets the front-rear torque distribution ratio to the front-wheel drive torque and the rear-wheel drive torque. the torque change rate of the front wheel drive torque and the torque change rate of the rear wheel drive torque are set to approximately the same value, and when the entire vehicle torque is in a high torque region equal to or greater than a predetermined threshold, the front / rear torque distribution ratio is set to a distribution ratio different from the basic distribution ratio, and the torque change rate of the front wheel drive torque and the torque change rate of the rear wheel drive torque are set to different values, and the closer the entire vehicle torque approaches the boundary with the low torque region in the high torque region, the closer the front / rear torque distribution ratio is to the basic distribution ratio. [Effects of the Invention]

[0008] As described above, according to the present invention, it is possible to provide a vehicle control device that can switch the torque direction of the front wheel motor and the rear wheel motor at the same timing. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing the configuration of a vehicle equipped with a vehicle control device according to an embodiment of the present invention. [Figure 2]FIG. 2 is a setting map of the front and rear torque distribution ratio that is referred to by the vehicle control device according to one embodiment of the present invention. [Figure 3] FIG. 3 is a timing chart showing the time transition of the degree of front wheel drive torque and rear wheel drive torque during operation of the vehicle control device according to one embodiment of the present invention. [Figure 4] FIG. 4 is a timing chart showing the time transition of the degree of front wheel drive torque and rear wheel drive torque in the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] A vehicle control device according to one embodiment of the present invention is mounted on a vehicle including a front-wheel motor that outputs front-wheel drive torque to the front wheels and a rear-wheel motor that outputs rear-wheel drive torque to the rear wheels, and includes a control unit that sets a front-rear torque distribution ratio, which is the distribution ratio between the front-wheel drive torque and the rear-wheel drive torque, and controls the front-wheel motor and the rear-wheel motor based on the front-rear torque distribution ratio, and the control unit sets the front-rear torque distribution ratio to the front-wheel drive torque when the total vehicle torque, which is the sum of the front-wheel drive torque and the rear-wheel drive torque, is in a low torque region less than a predetermined threshold. a basic distribution rate at which front wheel drive torque and rear wheel drive torque are equal, a rate of change of front wheel drive torque and a rate of change of rear wheel drive torque are set to substantially the same value, and when the total vehicle torque is in a high torque range equal to or greater than a predetermined threshold, the front / rear torque distribution rate is set to a distribution rate different from the basic distribution rate, and the rate of change of front wheel drive torque and the rate of change of rear wheel drive torque are set to different values, and the front / rear torque distribution rate is set to approach the basic distribution rate as the total vehicle torque in the high torque range approaches the boundary with the low torque range. This allows the front wheel motor and the rear wheel motor to switch the torque direction at the same time. [Example]

[0011] Hereinafter, a vehicle equipped with a vehicle control device according to an embodiment of the present invention will be described with reference to the drawings.

[0012] As shown in FIG. 1, the vehicle 1 is configured as an electric four-wheel drive vehicle having front wheels 3 and rear wheels 4 as drive wheels, a front-wheel motor 28 that outputs front-wheel drive torque to the front wheels 3, and a rear-wheel motor 26 that outputs rear-wheel drive torque to the rear wheels 4.

[0013] The vehicle 1 is equipped with an inverter 25 that converts DC power supplied from a battery (not shown) into AC power and supplies it to the front wheel motor 28, and an inverter 24 that converts DC power supplied from the battery into AC power and supplies it to the rear wheel motor 26.

[0014] The vehicle 1 is provided with a reducer 29 between the front-wheel motor 28 and the front wheels 3. The reducer 29 reduces the rotation output from the front-wheel motor 28 and transmits it to the front wheels 3. The vehicle 1 is provided with a reducer 27 between the rear-wheel motor 26 and the rear wheels 4. The reducer 27 reduces the rotation output from the rear-wheel motor 26 and transmits it to the rear wheels 4.

[0015] The vehicle 1 is equipped with a control device 10 that controls the entire vehicle. The control device 10 is configured by a computer unit that includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory, input ports, and output ports.

[0016] The ROM of the computer unit stores various constants, various maps, and the like, as well as a program for causing the computer unit to function as the control device 10. That is, in the computer unit, the CPU executes the program stored in the ROM, causing the computer unit to function as the control device 10 in this embodiment.

[0017] The control device 10 is equipped with a control unit 11, which sets a front-to-rear torque distribution ratio, which is the distribution ratio between the front wheel drive torque and the rear wheel drive torque, and controls the front wheel motor 28 and the rear wheel motor 26 based on the front-to-rear torque distribution ratio.

[0018] When the total vehicle torque, which is the sum of the front wheel drive torque and the rear wheel drive torque, is in a low torque region less than a predetermined threshold T(th), the control unit 11 sets the front / rear torque distribution ratio to a basic distribution ratio in which the front wheel drive torque and the rear wheel drive torque are equal, and sets the torque change rate of the front wheel drive torque and the torque change rate of the rear wheel drive torque to approximately the same value. For example, when the total vehicle torque is in the low torque region, the control unit 11 sets the front / rear torque distribution ratio to the basic distribution ratio of 50:50. Note that approximately the same values for the torque change rates are not limited to strictly the same values, but also include values that can be considered to be substantially the same.

[0019] When the total vehicle torque is in a high torque region equal to or greater than a predetermined threshold value T(th), the control unit 11 sets the front / rear torque distribution ratio to a distribution ratio different from the basic distribution ratio, and also sets the torque change rate of the front wheel drive torque and the torque change rate of the rear wheel drive torque to different values. For example, when the total vehicle torque is in the high torque region, the control unit 11 sets the front / rear torque distribution ratio to a value different from the basic distribution ratio, such as 70:30. In the high torque region, the front / rear torque distribution ratio is not constant but changes depending on the total vehicle torque.

[0020] The control unit 11 sets the front-rear torque distribution ratio so that it approaches the basic distribution ratio as the total vehicle torque approaches the boundary with the low torque region in the high torque region. For example, when the total vehicle torque is farther from the boundary with the low torque region and is in the high torque region, the control unit 11 sets the front-rear torque distribution ratio to 70:30, which is different from the basic distribution ratio, but as the total vehicle torque approaches the boundary with the low torque region, the control unit 11 gradually changes the front-rear torque distribution ratio to 60:40 and 55:45, and sets the front-rear torque distribution ratio to 50:50 at the boundary with the low torque region. Note that the boundary between the high torque region and the low torque region is the position where the total vehicle torque becomes a predetermined threshold value T(th).

[0021] In the high torque region, the control unit 11 keeps constant the sum of the torque change rate of the front wheel motor 28 and the torque change rate of the rear wheel motor 26. This keeps the torque change rate of the vehicle constant even if the front / rear torque distribution ratio changes.

[0022] The high torque region is a region where the absolute value of both positive and negative torque values is equal to or greater than a predetermined threshold value T(th), and the low torque region is a region where the absolute value of both positive and negative torque values is less than the predetermined threshold value T(th).

[0023] The front / rear torque distribution ratio setting map will be described with reference to Fig. 2. The control unit 11 sets the front / rear torque distribution ratio based on the front / rear torque distribution ratio setting map. In Fig. 2, the vertical axis represents the torque of each motor, and the horizontal axis represents the overall vehicle torque.

[0024] 2, in the setting map for the front / rear torque distribution ratio, in the low torque region where the total vehicle torque, which is the sum of the front wheel drive torque and the rear wheel drive torque, is less than a predetermined threshold value T(th), the front / rear torque distribution ratio is set to a basic distribution ratio in which the front wheel drive torque and the rear wheel drive torque are equal. Also, the torque change rate of the front wheel drive torque and the torque change rate of the rear wheel drive torque are set to approximately the same value.

[0025] In the high torque region where the overall vehicle torque is equal to or greater than a predetermined threshold T(th), the front / rear torque distribution ratio is set to a distribution ratio different from the basic distribution ratio, and the torque change rate of the front wheel drive torque and the torque change rate of the rear wheel drive torque are set to different values.

[0026] In the high torque region, the front / rear torque distribution rate is set to approach the basic distribution rate as the overall vehicle torque approaches the boundary with the low torque region.

[0027] Referring to Figure 3, we will explain the transition of the jerk (jerk) of the front wheel motor 28, the rear wheel motor 26, and the entire vehicle when moving from the high torque region through the low torque region to the 0 Nm line. Jerk is the rate of change of acceleration per unit time, also known as jerk. In Figure 3, the vertical axis represents jerk, and the horizontal axis represents time.

[0028] As shown in FIG. 3, at time t1, the overall vehicle effort decreases toward 0 Nm. The efforts of the front-wheel motor 28 and the rear-wheel motor 26 also decrease toward 0 Nm. At time t2, the overall vehicle effort reaches 0 Nm. At this time t2, the front-wheel motor 28 and the rear-wheel motor 26 simultaneously reach 0 Nm. Therefore, the front-wheel motor 28 and the rear-wheel motor 26 can switch torque directions (cross over zero torque) at the same timing at time t2.

[0029] On the other hand, in the comparative example shown in Fig. 4, the efficiency of the entire vehicle is reduced at time t11, and the efficiency of the front wheel motor and the rear wheel motor is also reduced.

[0030] After that, at time t12, the effort of the front wheel motor reaches 0 Nm. Also, the effort of the entire vehicle and the effort of the rear wheel motor become the same value.

[0031] After that, at time t13, the effort of the rear wheel motor reaches 0 Nm, and the effort of the entire vehicle also reaches 0 Nm. In this way, in the comparative example, after the front wheel motor switches torque direction (crosses zero torque) at time t12, the rear wheel motor also switches torque direction (crosses zero torque) at time t13.

[0032] As described above, in this embodiment, when the total vehicle torque, which is the sum of the front wheel drive torque and the rear wheel drive torque, is in a low torque region below the predetermined threshold T(th), the control unit 11 sets the front / rear torque distribution ratio to a basic distribution ratio in which the front wheel drive torque and the rear wheel drive torque are equal, and sets the torque change rate of the front wheel drive torque and the torque change rate of the rear wheel drive torque to approximately the same value. Furthermore, when the total vehicle torque is in a high torque region above the predetermined threshold T(th), the control unit 11 sets the front / rear torque distribution ratio to a distribution ratio different from the basic distribution ratio, and sets the torque change rate of the front wheel drive torque and the torque change rate of the rear wheel drive torque to different values. Furthermore, the control unit 11 sets the front / rear torque distribution ratio to approach the basic distribution ratio as the total vehicle torque approaches the boundary with the low torque region in the high torque region.

[0033] As a result, the front-wheel motor 28 and the rear-wheel motor 26 can switch torque directions (cross over to zero torque) at the same time as the overall vehicle torque approaches the boundary between the high-torque region and the low-torque region, thereby enabling the front-wheel motor 28 and the rear-wheel motor 26 to switch torque directions (cross over to zero torque). In addition, the front-wheel motor 28 and the rear-wheel motor 26 can be set to different maximum motor torque and maximum output specifications, ensuring the drive torque required for vehicle travel even in two-wheel drive mode, in which either the front wheels 3 or the rear wheels 4 are driven. This point will be explained in more detail. Consider a case in which the front-wheel motor 28 and the rear-wheel motor 26 use motors with the same maximum motor torque and maximum output. In this case, even in the high-torque region, the front-wheel motor 28 and the rear-wheel motor 26 can set their front-wheel torque and rear-wheel drive torque to the basic distribution ratio, which makes the front-wheel drive torque and the rear-wheel drive torque equal, and the torque change rate of the front-wheel drive torque and the torque change rate of the rear-wheel drive torque can be set to approximately the same value. In four-wheel drive, two motors simultaneously generate driving force, so the maximum motor torque and maximum output of each motor can be relatively small. However, in two-wheel drive, a single motor generates the driving force required to drive the vehicle, so a motor with a low maximum motor torque and maximum output would result in insufficient driving force. If both the front-wheel motor 28 and the rear-wheel motor 26 have high maximum motor torque and maximum output to avoid insufficient driving force in two-wheel drive, the motors will be driven with excess power remaining in four-wheel drive. In other words, if both the front-wheel motor 28 and the rear-wheel motor 26 have the same maximum motor torque and maximum output, the motors will be over-specified. For these reasons, it is desirable to use a motor with a higher maximum motor torque and maximum output for generating driving force in two-wheel drive than a motor that generates driving force only in four-wheel drive. Furthermore, the torque change rate for the front wheels 3 and the torque change rate for the rear wheels 4 can be set using a single map.

[0034] In this embodiment, the control unit 11 keeps the sum of the torque change rate of the front wheel motor 28 and the torque change rate of the rear wheel motor 26 constant in the high torque region.

[0035] As a result, the sum of the torque change rate of the front wheel motor 28 and the torque change rate of the rear wheel motor 26 is kept constant, so that the jerk can be kept constant.

[0036] In addition, in this embodiment, the high torque region is a region where the absolute value of the torque value is greater than or equal to a predetermined threshold value T(th) in both positive and negative directions, and the low torque region is a region where the absolute value of the torque value is less than the predetermined threshold value T(th) in both positive and negative directions.

[0037] This allows the front wheel motor 28 and the rear wheel motor 26 to switch torque direction (crossing zero torque) at the same time in both cases where the torque value transitions from positive powering to negative regenerative torque, and where the torque value transitions from negative regenerative torque to positive powering.

[0038] While an embodiment of the present invention has been disclosed, it will be apparent to one skilled in the art that modifications may be made thereto without departing from the scope of the present invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0039] 1 vehicle 3 Front wheels 4 rear wheels 11 Control section 26 Rear wheel motor 28 Front wheel motor

Claims

1. a front-wheel motor that outputs front-wheel drive torque to the front wheels; a rear-wheel motor that outputs rear-wheel drive torque to the rear wheels, a control unit that sets a front-to-rear torque distribution ratio, which is a distribution ratio between the front wheel drive torque and the rear wheel drive torque, and controls the front wheel side motor and the rear wheel side motor based on the front-to-rear torque distribution ratio; The control unit when an overall vehicle torque, which is a combined torque of the front wheel drive torque and the rear wheel drive torque, is in a low torque region less than a predetermined threshold, the front / rear torque distribution ratio is set to a basic distribution ratio in which the front wheel drive torque and the rear wheel drive torque are equal, and the torque change rate of the front wheel drive torque and the torque change rate of the rear wheel drive torque are set to approximately the same value; When the entire vehicle torque is in a high torque region equal to or greater than a predetermined threshold, the front / rear torque distribution ratio is set to a distribution ratio different from the basic distribution ratio, and the torque change rate of the front wheel drive torque and the torque change rate of the rear wheel drive torque are set to different values; 10. A vehicle control device, comprising: a control unit for controlling a front-rear torque distribution ratio such that the front-rear torque distribution ratio approaches the basic distribution ratio as the overall vehicle torque approaches the boundary with the low torque region in the high torque region.

2. 2. The vehicle control device according to claim 1, wherein the control unit maintains a constant sum of the torque change rate of the front wheel motor and the torque change rate of the rear wheel motor in the high torque region.

3. The high torque region is a region in which the absolute values of both positive and negative torque values are equal to or greater than the predetermined threshold value, 3. The vehicle control device according to claim 1, wherein the low torque region is a region in which absolute values of both positive and negative torque values are less than the predetermined threshold value.

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