JP7439484B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

When applying friction braking force to the wheels of a vehicle, a friction material is pressed against a rotating body that rotates integrally with the wheels. In this way, when the friction material is pressed against the rotating body, abnormal noise may be generated.

In the control device disclosed in Patent Document 1, control is performed to adjust the braking force for each wheel so that the force with which the friction material is pressed against the rotating body does not fall into a region where abnormal noise may occur. Specifically, while maintaining the total value of the front wheel braking force, which is the frictional braking force applied to the front wheels, and the rear wheel braking force, which is the frictional braking force applied to the rear wheels, the front wheel braking force and the rear wheel braking force are reduced. One of them is decreased while the other is increased.

Japanese Patent Application Publication No. 2014-69602

In the control device disclosed in Patent Document 1, when control is performed to suppress the generation of abnormal noise due to vehicle braking by adjusting front wheel braking force and rear wheel braking force, friction control is performed before the intervention of the control. When the power is small, a negative value may be set as the target value of the frictional braking force for a wheel among the front wheels and rear wheels whose frictional braking force needs to be reduced. In this case, the total value of the actually applied front wheel braking force and rear wheel braking force cannot be maintained only by adjusting the frictional braking force for each wheel. Patent Document 1 suggests increasing the driving force input to the wheels when the target value of the braking force for the wheels is negative. However, when the output of the power source is increased during braking of the vehicle, the energy efficiency of the entire vehicle becomes inefficient.

A vehicle control device to solve the above problem is a braking device that can individually change the front wheel braking force, which is a frictional braking force applied to the front wheels of the vehicle, and the rear wheel braking force, which is a frictional braking force applied to the rear wheels of the vehicle. The target value of the total braking force and the ratio of the front wheel braking force to the front wheel braking force and the rear wheel braking force are applied to a vehicle having a frictional braking force applied to the vehicle. a brake control unit that controls the braking device based on a front-rear distribution ratio; a drive control unit that controls a power source of the vehicle; a vehicle speed derivation unit that derives a vehicle body speed of the vehicle as a vehicle speed; When the vehicle speed is less than or equal to a prescribed determination speed, the front-rear distribution ratio is changed to be different from that when the vehicle speed is higher than the determination speed, and The gist thereof is to include a low speed instruction section that performs low speed processing that requests the drive control section to reduce the driving force output by the power source.

One of the causes of the phenomenon in which abnormal noise is generated when applying frictional braking force to a wheel is that the frictional braking force applied to the wheel is balanced with the driving force transmitted to the wheel.
In the above configuration, when the vehicle speed becomes equal to or less than the determination speed when the vehicle is braked and it is determined that the vehicle is traveling at a low speed, the low speed process is executed. In low-speed processing, the drive control unit is required to not only change the front-rear distribution ratio but also reduce the driving force. When the driving force is reduced in accordance with such a request, it becomes difficult to balance the frictional braking force and the driving force even if the fluctuation range of the braking force accompanying the change in the front-rear distribution ratio is small. In other words, when it is difficult to reduce the amount of frictional braking force applied to the wheels because the frictional braking force is small, the generation of abnormal noise caused by applying frictional braking force to the wheels can be suppressed without increasing the driving force. can do.

FIG. 1 is a schematic diagram showing an embodiment of a vehicle control device and a vehicle that is a control target of the control device. 5 is a flowchart showing the flow of processing executed by the control device. 5 is a timing chart showing braking force and driving force of a vehicle controlled by the control device.

An embodiment of a vehicle control device will be described below with reference to FIGS. 1 to 3.
FIG. 1 shows a vehicle 90 and a control device 10 for the vehicle 90.
Vehicle 90 is equipped with four wheels. The vehicle 90 includes a right front wheel FR and a left front wheel FL as front wheels. The vehicle 90 includes a right rear wheel RR and a left rear wheel RL as rear wheels. Vehicle 90 includes a power source 71 that outputs driving force. The power source 71 is, for example, an internal combustion engine. The driving force output from the power source 71 is transmitted to each front wheel FL, FR via a differential gear 72. That is, vehicle 90 is a front wheel drive vehicle.

Vehicle 90 includes a braking device 80. The brake device 80 includes a hydraulic pressure generator 81, a brake actuator 83, and a brake mechanism 84. The braking mechanism 84 is provided at each wheel FL, FR, RL, and RR of the vehicle 90. A brake operating member 61 such as a brake pedal is connected to the hydraulic pressure generating device 81 . When the brake operation member 61 is operated, MC pressure, which is the hydraulic pressure in the master cylinder 82 included in the hydraulic pressure generating device 81, is generated. The MC pressure increases depending on the operating force of the brake operating member 61, as the operating force increases.

The hydraulic pressure generator 81 supplies brake fluid to the brake actuator 83. Brake actuator 83 is connected to wheel cylinder 85 of each brake mechanism 84 . Brake fluid is supplied to the wheel cylinder 85 from the hydraulic pressure generator 81 via the brake actuator 83 . When brake fluid is supplied to the wheel cylinder 85, the WC pressure, which is the fluid pressure within the wheel cylinder 85, increases. Each braking mechanism 84 is configured such that the higher the WC pressure, the greater the force with which the friction material 86 is pressed against the rotating body 87 that rotates integrally with the wheel. In the braking device 80, the WC pressure is individually adjusted by operating the brake actuator 83 so that the WC pressure of the braking mechanism 84 corresponding to the front wheels FL, FR is different from the WC pressure of the braking mechanism 84 corresponding to the rear wheels RL, RR. can be adjusted to Each braking mechanism 84 can apply a larger frictional braking force to the wheels FL, FR, RL, and RR as the WC pressure increases. That is, the greater the operating force of the brake operating member 61 and the higher the MC pressure, the greater the frictional braking force can be applied to the wheels FL, FR, RL, and RR.

Hereinafter, the application of friction braking force to the wheels FL, FR, RL, and RR based on the operation of the brake operation member 61 will be referred to as braking of the vehicle 90. Further, the frictional braking force applied to the front wheels FL, FR by the braking mechanism 84 provided corresponding to the front wheels FL, FR is referred to as front wheel braking force BPF. The frictional braking force applied to the rear wheels RL and RR by the braking mechanism 84 provided corresponding to the rear wheels RL and RR is referred to as rear wheel braking force BPR. Since the braking device 80 can individually adjust the WC pressure as described above, the front wheel braking force BPF and the rear wheel braking force BPR can be adjusted individually.

Vehicle 90 is equipped with various sensors. A wheel speed sensor 91 and a brake stroke sensor 92 are shown as examples of various sensors. Wheel speed sensors 91 are provided at each wheel FL, FR, RL, and RR.

Detection signals from various sensors such as a wheel speed sensor 91 and a brake stroke sensor 92 are input to the control device 10 .
The control device 10 includes a brake control section 11, a low speed instruction section 12, a derivation section 13, and a drive control section 14 as functional sections. Note that the control device 10 may have any of the following configurations (a) to (c).

(a) It includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memories such as RAM and ROM. The memory stores program codes or instructions configured to cause the CPU to perform processes. Memory or computer-readable media includes any available media that can be accessed by a general purpose or special purpose computer. (b) It includes one or more dedicated hardware circuits that perform various processes. The dedicated hardware circuit is, for example, an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). (c) It includes a processor that executes a part of various processes according to a computer program, and a dedicated hardware circuit that executes the remaining processes among the various processes.

The derivation unit 13 derives the wheel speed of each wheel based on the detection signal from each wheel speed sensor 91. Then, the control device 10 derives the vehicle body speed of the vehicle 90 as the vehicle speed VS based on each wheel speed. That is, the deriving section 13 is a vehicle speed deriving section. Further, the derivation unit 13 derives a brake operation amount as the operation amount of the brake operation member 61 based on the detection signal from the brake stroke sensor 92 .

The drive control section 14 has a function of controlling the power source 71.
The brake control unit 11 has a function of controlling the brake device 80. If the ratio of allocating the total braking force BPA, which is the frictional braking force applied to the vehicle 90, to the front wheel braking force BPF and the rear wheel braking force BPR is the front-rear distribution ratio, the brake control unit 11 sets the target value of the total braking force BPA. The braking device 80 is controlled based on a certain target braking force BPT and a front-rear distribution ratio. That is, the front wheel braking force BPF and the rear wheel braking force BPR are applied based on the target braking force BPT and the front-rear distribution ratio. Note that the target braking force BPT is derived based on the amount of braking operation. Further, the front/rear distribution ratio is set to a prescribed ratio as an initial value, and the ratio can be changed by low speed processing performed by the low speed instruction section 12 as described later.

The low-speed indicator 12 detects a situation in which abnormal noise is likely to occur when the vehicle 90 is running at a low speed and the friction material 86 is pressed against the rotating body 87 due to the braking of the vehicle 90. When this is the case, it is assumed that the execution condition is satisfied and the low-speed processing is executed. The low speed instruction unit 12 determines that the vehicle 90 is traveling at a low speed when the vehicle speed VS is less than or equal to a vehicle speed determination value VSth, which is a prescribed determination speed. The vehicle speed determination value VSth is a value set in advance as a threshold value for determining whether or not the vehicle speed VS is low. The low speed instruction unit 12 determines that the situation is such that abnormal noise is likely to occur when the target braking force BPT is within a prescribed determination range. The prescribed determination range is a range derived in advance through experiments or the like as a range of the target braking force BPT in which abnormal noise is likely to occur when the friction material 86 is pressed against the rotating body 87 due to braking of the vehicle 90.

In the low-speed processing, the low-speed instruction unit 12 changes the front-rear distribution ratio in a manner different from that in the case where the vehicle speed VS is higher than the vehicle speed determination value VSth. The low-speed instruction unit 12 sets a front-rear distribution ratio so as to suppress abnormal noise caused by application of frictional braking force, based on the relationship between the magnitude of the frictional braking force and the situation in which abnormal noise occurs based on, for example, the results of experiments and the like. . Note that in this embodiment, the low-speed instruction unit 12 increases the ratio of rear wheel braking force BPR in the front-rear distribution ratio. For example, if the ratio of rear wheel braking force BPR is increased by changing the front-rear distribution ratio while total braking force BPA is increasing, the front wheel braking force BPF will increase while the amount of increase in total braking force BPA is maintained. The amount of increase is reduced and the amount of increase of rear wheel braking force BPR is increased.

Further, in the low speed processing, the low speed instruction section 12 requests the drive control section 14 to reduce the driving force DP transmitted from the power source 71 to the front wheels FL and FR. For example, the low speed instruction unit 12 requests that the driving force DP be reduced to the minimum driving force DPmin. The minimum driving force DPmin is the minimum value of the driving force DP that allows the internal combustion engine that is the power source 71 to continue operating.

A processing routine executed by the control device 10 when braking of the vehicle 90 is requested will be described with reference to FIG. 2. This processing routine is repeatedly executed from when the operation of the brake operation member 61 is started until the amount of brake operation starts to decrease.

When this processing routine is executed, first in step S101, the control device 10 causes the brake control unit 11 to acquire the target braking force BPT. After that, the control device 10 moves the process to step S102.

In step S102, the control device 10 causes the low speed instruction unit 12 to determine whether the vehicle speed VS is less than or equal to the vehicle speed determination value VSth. If the vehicle speed VS is greater than the vehicle speed determination value VSth (S102: NO), the control device 10 temporarily ends this processing routine. On the other hand, if the vehicle speed VS is less than or equal to the vehicle speed determination value VSth (S102: YES), the control device 10 moves the process to step S103.

In step S103, the control device 10 causes the low speed instruction unit 12 to determine whether the target braking force BPT is within the determination range. If the target braking force BPT is not included in the determination range (S103: NO), the control device 10 temporarily ends this processing routine. On the other hand, if the target braking force BPT is within the determination range (S103: YES), the control device 10 moves the process to step S104.

In step S104, the control device 10 causes the low speed instruction unit 12 to perform low speed processing. The low-speed instruction unit 12 performs low-speed processing to change the front-rear distribution ratio and change the braking force distribution applied to the wheels. As a result, the front-rear distribution ratio becomes a ratio different from that before the vehicle speed VS becomes equal to or less than the vehicle speed determination value VSth. Then, the brake control unit 11 controls the brake device 80 based on the changed front-rear distribution ratio, thereby changing the distribution between the front wheel braking force BPF and the rear wheel braking force BPR. Further, the low speed instruction section 12 requests the drive control section 14 to reduce the driving force DP in the low speed processing. As a result, the drive control unit 14 controls the power source 71, so that the driving force DP decreases compared to before the vehicle speed VS becomes equal to or less than the vehicle speed determination value VSth. After executing the low-speed processing, the control device 10 ends this processing routine.

Note that the front-to-rear distribution ratio changed in the process of step S104 is initialized, for example, when the amount of operation of the brake operation member 61 starts to decrease. The WC pressure is gradually returned to the magnitude according to the initial value of the front-rear distribution ratio by the braking control unit 11, and the distribution of front wheel braking force BPF and rear wheel braking force BPR is the distribution when low speed processing is not performed. will be returned to. Further, for example, the front-rear distribution ratio may be initialized when the vehicle speed VS becomes larger than the vehicle speed determination value VSth or when the target braking force BPT falls outside the determination range.

The operation and effects of this embodiment will be explained.
With reference to FIG. 3, the state of vehicle 90 when processing by control device 10 is executed will be described.

In the example of FIG. 3, braking of the vehicle 90 is started at timing t1, and the vehicle speed VS begins to decrease as shown in FIG. 3(e). Vehicle speed VS decreases to vehicle speed determination value VSth at timing t2, and becomes "0" at subsequent timing t3. Thereafter, the vehicle speed VS starts increasing from timing t4 onwards. From timing t5, the accelerator pedal is started to be depressed, and the amount of increase in the vehicle speed VS is increasing. In the example shown in FIG. 3, the target braking force BPT is included in the determination range at timing t2 (S103: YES).

Until timing t2, the vehicle speed VS is larger than the vehicle speed determination value VSth (S102: NO), so the low speed process is not performed. After timing t2, since the vehicle speed VS is less than or equal to the vehicle speed determination value VSth (S102: YES), the low speed process is started (S104).

As shown in FIG. 3(a), the driving force DP starts decreasing from timing t1 when braking is started. In (a) of FIG. 3, as a comparative example, an example in which the low-speed processing is not performed is indicated by a two-dot chain line. In the example shown by the two-dot chain line, the driving force DP becomes the minimum driving force DPmin at timing t3 when the vehicle speed VS becomes "0", and starts increasing from timing t5.

On the other hand, in the example of the present embodiment shown by the solid line in FIG. The driving force DP is decreased at a larger decreasing gradient after timing t2 so as to reach the minimum driving force DPmin.

As shown in FIG. 3(b), the total braking force BPA starts increasing from timing t1 when braking is started. As the amount of braking operation is gradually increased, the total braking force BPA increases during the period from timing t1 to timing t3. During the period from timing t3 to timing t4, the total braking force BPA is held constant as the amount of braking operation is held constant. Thereafter, after timing t4 when the amount of braking operation is decreased, the total braking force BPA starts decreasing and reaches "0" at timing t5. Note that the change in the total braking force BPA is the same in the case of the comparative example and the case of the present embodiment. That is, even if the low speed processing is performed, the total braking force BPA is maintained.

(c) of FIG. 3 shows the transition of the front wheel braking force BPF, and (d) of FIG. 3 shows the transition of the rear wheel braking force BPR. In FIGS. 3(c) and 3(d), a comparative example in which the low-speed processing is not performed is indicated by a two-dot chain line. In the comparative example shown by two-dot chain lines in FIGS. 3(c) and 3(d), the total braking force BPA increases until timing t3 and starts decreasing from timing t4, similar to the total braking force BPA shown in FIG. 3(b). There is.

On the other hand, in the example of this embodiment shown by solid lines in FIGS. 3(c) and 3(d), the front-rear distribution ratio is changed by the low-speed processing after timing t2. Specifically, since the braking control unit 11 does not adjust the WC pressure from when braking is started at timing t1 until timing t2 when the vehicle speed VS reaches the vehicle speed determination value VSth, the front wheel braking force BPF and the rear The wheel braking force BPR increases similarly to the comparative example shown by the two-dot chain line. When the front-rear distribution ratio is changed by the low-speed processing after timing t2, the ratio of the rear wheel braking force BPR is increased, so the brake control unit 11 changes the WC pressure of the braking mechanism 84 corresponding to the front wheels FL and FR. , and the WC pressure of the braking mechanism 84 corresponding to the rear wheels RL and RR are individually adjusted.

As a result, as shown by the solid line in FIG. 3(c), the increasing slope of the front wheel braking force BPF during the period from timing t2 to timing t3 is smaller than that of the comparative example shown by the two-dot chain line. Therefore, after timing t2, the front wheel braking force BPF is smaller than in the comparative example. Furthermore, as shown by the solid line in FIG. 3(d), the rising slope of the rear wheel braking force BPR during the period from timing t2 to timing t3 is larger than that of the comparative example shown by the two-dot chain line. Therefore, after timing t2, the rear wheel braking force BPR is larger than that in the comparative example. That is, after timing t2, the braking force distribution is changed.

Here, in a front-wheel drive vehicle such as the vehicle 90, abnormal noise is likely to occur at the front wheels FL and FR when the vehicle 90 is braked. According to the control device 10, as shown in FIGS. 3(b) to 3(d), when the low speed process is performed, the total braking force BPA is maintained at the same level as when the low speed process is not performed. In this state, the magnitude of the front wheel braking force BPF is different from that in the case where the low-speed processing is not performed. As a result, although a braking force that decelerates the vehicle 90 is applied to the vehicle 90, the front wheel braking force BPF becomes difficult to balance with the driving force DP. Thereby, it is possible to suppress the generation of abnormal noise due to the application of the front wheel braking force BPF.

Furthermore, in the low-speed processing in the control device 10, not only the front-rear distribution ratio is changed but also the driving force DP is reduced. This makes it difficult for the frictional braking force and the driving force to be balanced even if the fluctuation range of the frictional braking force due to a change in the front-rear distribution ratio is small. In other words, if it is difficult to ensure a reduction in the front wheel braking force BPF because the front wheel braking force BPF is small at the time when low speed processing is started, the front wheel braking force BPF can be applied without increasing the driving force DP. It is possible to suppress the occurrence of abnormal noise caused by.

Note that the vehicle deceleration may vary as the driving force DP decreases. However, in this embodiment, since the low-speed processing is performed only when the vehicle 90 is traveling at low speed, a decrease in the driving force DP has little effect on vehicle deceleration.

This embodiment can be modified and implemented as follows. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
- In the low speed processing in the above embodiment, the low speed instruction section 12 requests the drive control section 14 to reduce the driving force DP to the minimum driving force DPmin. In the low speed processing, the driving force DP does not necessarily have to be reduced to the minimum driving force DPmin. Further, as an example, it is also possible to reduce the driving force DP to "0".

- In the low-speed processing in the above embodiment, the ratio of rear wheel braking force BPR in the front-rear distribution ratio is increased by decreasing the upward slope of front wheel braking force BPF and increasing the upward slope of rear wheel braking force BPR. Ta. Alternatively, the ratio of rear wheel braking force BPR in the front-rear distribution ratio can be increased by maintaining the front wheel braking force BPF at the time when low-speed processing is started and continuing to increase the rear wheel braking force BPR. can.

- In the low-speed processing in the above embodiment, the ratio of rear wheel braking force BPR in the front-rear distribution ratio is increased. If the frictional braking force and the driving force DP can avoid imbalance, the occurrence of abnormal noise can be suppressed, so changing the front-rear distribution ratio is not limited to increasing the ratio of the rear wheel braking force BPR in the front-rear distribution ratio. That is, in the low-speed processing, the ratio of the front wheel braking force BPF in the front-rear distribution ratio can also be increased. When the ratio of front wheel braking force BPF in the front-rear distribution ratio is increased, for example, while the total braking force BPA is maintained, the amount of increase in front wheel braking force BPF is increased and the amount of increase in rear wheel braking force BPR is decreased. Ru.

- In the above embodiment, if the vehicle speed VS is larger than the vehicle speed judgment value VSth, or if the target braking force BPT is not included in the judgment range, the low speed processing is not performed and the front/rear distribution ratio is not changed. Not done. In addition to these conditions, the low speed instruction unit 12 can also be configured not to perform the low speed process when the operation speed of the brake operation member 61 is faster than a prescribed determination operation speed. The operation speed of the brake operation member 61 can be derived by differentiating the amount of brake operation with respect to time. That is, if the driver of the vehicle requests sudden braking of the vehicle 90, the low speed process may not be performed and the braking force distribution may not be changed.

- In the embodiment described above, the low speed process is performed when the vehicle speed VS is less than or equal to the vehicle speed determination value VSth and the target braking force BPT is within the determination range. Regardless of whether or not the target braking force BPT is within the determination range, the low-speed processing may be performed when the vehicle speed VS is less than or equal to the vehicle speed determination value VSth.

- In the above embodiment, the generation of abnormal noise is suppressed by making it difficult to balance the frictional braking force and the driving force DP. The abnormal noise that may be generated due to the contact between the rotating body 87 and the friction material 86 in the braking mechanism 84 is caused not only by the balance between the frictional braking force and the driving force DP but also by other factors. According to the control device 10 that varies the front wheel braking force BPF and the rear wheel braking force BPR while maintaining the total braking force BPA by changing the front and rear distribution ratio, the front wheel braking is more effective than when low speed processing is not performed during braking. Since the magnitudes of the power BPF and the rear wheel braking force BPR can be changed, it is possible to make it difficult for the other factors mentioned above to lead to a situation where abnormal noise is likely to occur.

- The control device 10 can also be applied to a braking device that can individually change the frictional braking force applied to each wheel of the vehicle. In this case, the ratio of the total braking force to the frictional braking force applied to the left wheel and the frictional braking force applied to the right wheel is the left-right distribution ratio, and in addition to the front-rear distribution ratio, the left-right distribution ratio is It can also be changed.

- The braking device to which the control device 10 is applied may be one that can individually change the frictional braking force applied to the front wheels and the frictional braking force applied to the rear wheels. For example, a drum brake that can apply braking force by pressing a brake shoe, which is a friction material, against a drum, which is a rotating body, may be used. Furthermore, it is also possible to employ an electric braking device that can apply frictional braking force to the wheels by driving an electric motor.

- In the above embodiment, a front-wheel drive vehicle is illustrated, but the vehicle to which the control device 10 is applied may be a rear-wheel drive vehicle or a four-wheel drive vehicle. For example, in the case of a rear-wheel drive vehicle, it is preferable to increase the ratio of front wheel braking force in the front-rear distribution ratio during low-speed processing.

DESCRIPTION OF SYMBOLS 10... Control device 11... Brake control part 12... Low speed instruction part 13... Derivation part 14... Drive control part 61... Brake operation member 71... Power source 80... Brake device 84... Brake mechanism 85... Wheel cylinder 86... Friction material 87 ...Rotating body 90...Vehicle

Claims (2)

Applicable to vehicles that have a braking device that can individually change the front wheel braking force, which is a frictional braking force applied to the front wheels of the vehicle, and the rear wheel braking force, which is a frictional braking force applied to the rear wheels of the vehicle,
Based on the target value of the total braking force and the front-rear distribution ratio, the ratio of allocating the total braking force, which is the frictional braking force applied to the vehicle, to the front wheel braking force and the rear wheel braking force is defined as a front-rear distribution ratio. a brake control unit that controls the brake device;
a drive control unit that controls a power source of the vehicle;
a vehicle speed derivation unit that derives the vehicle body speed of the vehicle as a vehicle speed;
When the vehicle speed is equal to or lower than a predetermined determination speed when braking the vehicle, the vehicle speed is set to the The front and rear distribution ratio is changed to be different from that when the vehicle speed is higher than the determination speed, and the driving force output from the power source is reduced at a slope greater than before the vehicle speed becomes equal to or less than the determination speed. A control device for a vehicle, comprising: a low speed instruction section that performs low speed processing requested of a drive control section. The vehicle is a front wheel drive vehicle in which driving force from the power source is transmitted to the front wheels,
The vehicle control device according to claim 1, wherein the low speed instruction unit increases the ratio of the rear wheel braking force in the front-rear distribution ratio in the low speed processing.