Vehicle control device

Abstract

To provide a vehicle control device capable of preventing an increase in a braking distance even when a vehicle mounted with an ABS undergoes sudden braking in a situation where a contact load between a wheel and a road surface unexpectedly fluctuates.SOLUTION: A control device for a vehicle, mounted with a brake device and an anti-lock brake system controlling braking torque of the brake device so that a slip rate of a wheel with respect to a road surface becomes a predetermined reference target slip rate, comprises a controller controlling the brake device and the anti-lock brake system. When an earthquake determination section detects an occurrence of an earthquake (Yes in Step S2), the controller prevents activation of the anti-lock brake system (Step S3) or activates the anti-lock brake system with a target slip rate set to a corrected target slip rate which is larger than the reference target slip rate.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to a control device for a vehicle equipped with an antilock braking system (ABS).

Background Art

[0002] When a situation occurs during vehicle travel where the vehicle cannot travel safely due to an earthquake or the like, it is necessary to quickly stop the vehicle and allow the passengers to evacuate. For example, Patent Document 1 discloses a device configured to activate the brakes and release the vehicle door lock when the vertical acceleration of the vehicle is equal to or greater than a predetermined threshold value, enabling the passengers to evacuate quickly. Note that Patent Document 2 discloses a vehicle travel control device that can variably set overtaking travel control according to the situation so that safe overtaking travel can be performed even in an overtaking restricted environment. Patent Document 2 discloses that the overtaking restricted environment includes an emergency earthquake warning, and that the brake control device for braking the vehicle includes an ABS that controls the brake device to suppress or release wheel lock, among other things.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The braking force generated by the wheels varies depending on the ground contact load of the wheels on the road surface. Therefore, when the vehicle body moves up and down due to an earthquake or the like, the braking distance from when the brake is actuated until the vehicle stops may become longer. At that time, when the ABS that detects that the wheel has been locked and suppresses the wheel lock by adjusting the braking torque of the wheel is actuated, the braking distance of the vehicle may instead become longer. For example, when the ground contact load decreases due to the up and down movement of the vehicle, the wheel may be locked even if the braking torque is reduced by the ABS. In that case, the braking torque may be further reduced to release the lock. However, immediately after that, the ground contact load returns to its original value or increases, so the braking force of the wheel will be insufficient. When the ground contact load fluctuates unexpectedly in this way, the ABS cannot operate correctly, and there is a possibility that the braking force required to brake the vehicle will be insufficient. As a result, there was a risk that the braking distance of the vehicle would increase due to the actuation of the ABS. Such technical problems were not considered in Patent Document 1 and Patent Document 2, and there was room for improvement.

[0005] The present invention has been made by paying attention to the above technical problems, and an object thereof is to provide a vehicle control device capable of suppressing an increase in the braking distance even when a vehicle equipped with an ABS actuates an emergency brake when the ground contact load between the wheel and the road surface fluctuates unexpectedly.

Means for Solving the Problems

[0006] In order to achieve the above object, the present invention provides a control device for a vehicle, comprising a wheel, a brake device that applies a braking torque to the wheel, and an antilock brake system that controls the braking torque of the brake device so that the slip ratio of the wheel with respect to the road surface becomes a predetermined reference target slip ratio. The control device includes a controller that controls the brake device and the antilock brake system. The controller has an earthquake determination unit that detects the occurrence of an earthquake. When the earthquake determination unit detects the occurrence of an earthquake, the operation of the antilock brake system is prohibited, or a correction target slip ratio larger than the reference target slip ratio is set to operate the antilock brake system.

Advantages of the Invention

[0007] According to the control device for a vehicle of the present invention, when an unexpected change in the ground load between the road surface and the wheel occurs, it is possible to prevent or suppress the increase in the braking distance of the vehicle due to the operation of the ABS. Therefore, when an earthquake occurs, the vehicle can be quickly stopped, and the passengers can quickly move to evacuation actions.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0009] The vehicle in the embodiment of the present invention is a vehicle equipped with an anti-lock brake system (ABS) that controls to prevent or suppress the wheels from being locked by the brake device when an operation to suddenly brake the vehicle is performed by a driver's brake operation or the like during the running of the vehicle. FIG. 1 schematically shows the vehicle Ve configured as such. As shown in FIG. 1, the vehicle Ve includes a driving force source 1, a brake device 2, wheels 3, an ECU (electronic control unit) 4, a detection unit 5, and the like.

[0010] The driving force source 1 outputs torque for driving the wheels 3, that is, torque for generating the driving force of the vehicle Ve. As an example, it may have either a conventionally known engine (internal combustion engine) or a motor generator, or both.

[0011] The braking device 2 is a device that brakes the vehicle Ve by outputting a torque for braking the wheels 3. The braking device 2 is provided for each of the front and rear wheels 3 of the vehicle Ve. The braking device 2 is a device similar to the conventionally known braking device 2, and is, for example, a friction brake such as a disc brake, a drum brake, or a powder brake, and is configured to generate a braking force in a direction to stop the rotation of each wheel 3 by generating a frictional force by hydraulic pressure, electromagnetic force, or the like. For example, in the case of a drum brake, a piston attached to a wheel cylinder is actuated by the hydraulic pressure generated in a master cylinder, and a brake shoe with a friction material stretched by the piston is pressed against a brake drum that rotates together with the wheel 3, and is configured to transmit a braking torque to the wheel 3 by the frictional force generated. Further, a wheel speed sensor 5a for detecting the wheel speed, which is the respective rotational speed, is provided for each wheel 3. Note that the braking device 2 is configured such that the magnitude of the braking force output depends on the depression angle of a brake pedal operated by a driver.

[0012] This ECU 4 corresponds to the "controller" in the embodiment of the present invention, and is configured mainly with, for example, a microcomputer, performs calculations using data input from the detection unit 5, data stored in advance, and the like, and is configured to output a control command signal based on the calculation result. The input data is, for example, wheel speed, the rotational speed of the drive power source 1, the hydraulic pressure to the braking device 2, and the like. Further, the ECU 4 includes an ABS-ECU 4a and a seismic determination unit 4b.

[0013] The ABS-ECU 4a is an ECU 4 for operating the ABS. For example, when the braking torque of the braking device 2 suddenly increases and the wheel 3 locks, an electric signal is output to operate an ABS actuator (not shown) to control the hydraulic pressure of the wheel cylinder and adjust the braking force of the brake. The ABS actuator is an electromagnetic control valve that operates in response to the operation of the ABS. The ABS actuator is provided, for example, between the master cylinder and the wheel cylinder, and adjusts the hydraulic pressure from the master cylinder to the wheel cylinder to adjust the braking force generated on the wheel 3.

[0014] Note that the ABS is a conventionally known system, and is a system for preventing or suppressing the wheel 3 from locking and slipping when a large braking force is rapidly required due to a sudden braking operation by the driver or the like. As an example, in the ABS, the locking situation of the wheel 3 is detected by the wheel speed sensor 5a, and when it is detected that the wheel 3 is locked, the brake pressure for the locked wheel 3 is decreased to control so that the wheel 3 and the road surface grip. At that time, the vehicle body speed is obtained from the wheel speeds of the respective wheels 3, and the slip ratio of the wheel 3 is obtained based on the deviation between the vehicle body speed and the wheel speed. In the ABS, a target value of the slip ratio is set so that the wheel 3 is not locked or the lock of the wheel 3 is released, and the hydraulic pressure and the like for the braking device 2 are controlled based on the target slip ratio so that the wheel 3 reaches the target rotational speed.

[0015] The earthquake determination unit 4b determines the occurrence of an earthquake based on the data acquired by the detection unit 5, notifications from the outside, and the like. The determination of the occurrence of this earthquake may be executed by a conventionally known control. For example, when an emergency earthquake warning is acquired, or the control for determining the occurrence of an earthquake based on the change in the acceleration of the vehicle and the duration thereof disclosed in Japanese Patent Application Laid-Open No. 2014-153750, or the control for determining the occurrence of an earthquake based on the difference between the movement amount and attitude of the vehicle based on the captured image of the in-vehicle camera and the movement amount and attitude of the vehicle based on the vehicle sensor disclosed in Japanese Patent Application Laid-Open No. 2008-224353, and the like.

[0016] The detection unit 5 is a device or apparatus for acquiring various types of data and information necessary when controlling the vehicle Ve. In addition to the above-described wheel speed sensor 5a, the detection unit 5 includes a vehicle speed sensor 5b that detects the vehicle speed from the rotational speed of the wheels 3, an angular velocity sensor 5c that detects the angular velocity of the vehicle body, a brake sensor 5d that detects the operation amount (opening degree) of a brake pedal (not shown), an acceleration sensor 5e that detects the acceleration of the vehicle Ve, a master cylinder pressure sensor 5f that detects the hydraulic pressure acting on the master cylinder of the braking device 2, and the like. The detection unit 5, the ECU 4, and the ABS actuator configured as described above are electrically connected to each other by, for example, CAN (Controller Area Network), a wire harness, or the like, and output an electrical signal corresponding to the detected value or the calculated value to the ECU 4 as detection data.

[0017] FIG. 2 shows a flowchart that is an example of control executed by the ECU 4. First, in this flowchart, as shown in FIG. 2, it is determined whether an earthquake has occurred in step S1. The determination of the occurrence of an earthquake is made, for example, by receiving the above-described emergency earthquake warning with a receiver (not shown) or observing the initial microtremor.

[0018] In step S1, if it is determined that an earthquake has occurred, proceed to step S2. In step S2, based on step S1, it is determined whether an earthquake is actually occurring. Here, an earthquake actually occurring means, for example, that the seismic intensity or magnitude is greater than a predetermined value, or that a main motion is occurring. For example, as described above, it may be determined that the waveforms indicating changes in the acceleration in the front-rear direction, left-right direction, and up-down direction of the vehicle Ve are changes peculiar to an earthquake, or alternatively, based on the amount of movement and posture of the vehicle Ve based on image processing of an in-vehicle camera and the data detected by the detection unit 5, it may be determined that there are changes peculiar to an earthquake. For example, if any one of these three determinations, including the emergency earthquake warning, or two or more of the three determinations are satisfied, it may be determined that an earthquake is occurring. Note that it may also be determined that the vehicle body vibrates relatively greatly in the up-down direction due to an earthquake, or that the earthquake is of a scale such that it is necessary to stop the vehicle Ve.

[0019] In step S2, if it is affirmatively determined in step S2 that an earthquake is occurring, proceed to step S3. When proceeding to step S3, the operation of the ABS is prohibited. That is, if it is affirmatively determined in step S2, in order to prevent traffic accidents and evacuate passengers, if the driver or the like quickly operates the brake, the wheel 3 may be rapidly braked and locked. And in order to prevent the locking of the wheel 3, the ABS tries to operate. On the other hand, as described above, due to unexpected fluctuations in the ground contact load, the operation of the ABS may actually increase the braking distance of the vehicle Ve. To prevent or suppress this, in step S3, the operation of the ABS is prohibited.

[0020] On the contrary, if it is negatively determined in step S2, for example, that none of the three determinations hold, the process proceeds to step S4. That is, if it is determined in step S2 that an earthquake has not occurred, the process proceeds to step S4. When an earthquake has not occurred, unexpected fluctuations in the ground contact load are less likely to occur, so even if the ABS is activated, the braking distance of the vehicle Ve is unlikely to increase. Therefore, in such a case, the process proceeds to step S4, and this flowchart is terminated without prohibiting the activation of the ABS.

[0021] According to the control device for the vehicle Ve configured as described above, it is determined whether an earthquake has occurred based on an emergency earthquake warning, an in-vehicle sensor, or an in-vehicle camera. And when it is predicted that the ground contact load of the wheel 3 with respect to the road surface will fluctuate relatively greatly due to the detected scale and magnitude of the earthquake, etc., it is configured to prohibit the activation of the ABS. Therefore, it is possible to prevent or suppress a situation where the braking distance of the vehicle Ve increases due to the activation of the ABS caused by unexpected fluctuations in the ground contact load between the road surface and the wheel 3. Accordingly, when an earthquake occurs, the vehicle Ve can be quickly stopped, and the passengers can quickly move to evacuation actions.

[0022] Next, another example of the control executed by the ECU4 in the embodiment of the present invention will be described with reference to FIGS. 3 and 4. In the flowcharts in the other examples described below, steps similar to the steps already described are denoted by the same reference numerals, and the description thereof is omitted or simplified.

[0023] As shown in FIG. 3, in the flowchart in the other example, similar to the flowchart shown in FIG. 2, in step S1, it is determined whether an earthquake has occurred. If it is determined that an earthquake has occurred, the process proceeds to step S2, and it is determined whether an earthquake is currently occurring. If it is affirmatively determined in step S2 because an earthquake is currently occurring, the process proceeds to step S5.

[0024] In step S5, when the ABS is activated, the target slip ratio of the wheel 3 is increased. That is, it is set to a first target slip ratio B1 corresponding to the corrected target slip ratio in the embodiment of the present invention, which is a value larger than the reference target slip ratio B0 of the wheel 3 initially set when the ABS is activated. As shown in FIGS. 4(a) and 4(b), the braking force of the wheel 3 increases as the slip ratio increases up to a certain magnitude. On the other hand, the lateral force, which is the force in the direction perpendicular to the center plane of the wheel 3, decreases as the slip ratio of the wheel 3 increases. That is, substantially, the braking force and the lateral force of the wheel 3 are inversely proportional to each other with respect to the slip ratio of the wheel 3. Therefore, when the ABS is activated, the reference target slip ratio B0 of the wheel 3 is calculated within the range where the balance between the braking force and the lateral force is the best by experiments or the like, and the braking device 2 is controlled based on the reference target slip ratio B0. On the other hand, even if the thus-set ABS is activated, due to unpredictable external factors such as an earthquake as described above, the braking distance of the vehicle Ve may instead increase.

[0025] Therefore, in step S5, when an earthquake has occurred, the target slip ratio during ABS activation is increased. Specifically, as shown in FIG. 4(a), the setting range of the target slip ratio is changed from a preset setting range R1 to a range R2 set so that the braking force of the wheel 3 increases. As shown in FIG. 4(a), in the setting range R1 of the reference target slip ratio B0, when the ground load increases or there is no variation in the ground load, there is substantially no difference between the minimum braking force and the maximum braking force generated by the wheel 3 when the wheel 3 is locked and when the ABS is activated. On the other hand, when the ground load decreases and the ABS is activated, the minimum braking force generated by the wheel 3 is smaller compared to the case when the wheel 3 is locked.

[0026] On the other hand, in the setting range R2 of the first target slip ratio B1, as shown in Fig. 4(a), when the ground load decreases, the target slip ratio is set so that the minimum braking force of the wheel 3 generated during the operation of the ABS becomes approximately the same as the minimum braking force of the wheel 3 generated when the wheel 3 locks. Therefore, when the wheel 3 is locked, the average value of the braking force of the wheel 3 from the brake operation to the stop becomes a value close to the minimum braking force when the wheel 3 locks. In contrast, during the operation of the ABS, since it varies appropriately within the above-mentioned range, the average value from the brake operation to the stop becomes a larger value than when the wheel 3 is locked.

[0027] In addition, as shown in Fig. 4(b), by increasing the setting range of the target slip ratio of the wheel 3, the lateral force on the wheel 3 decreases. Therefore, when the ground load between the road surface and the wheel 3 fluctuates due to factors such as earthquakes that cannot be predicted in advance and the ABS is activated, which may cause the braking distance to extend instead, the above-mentioned control is executed. That is, it is an emergency measure and is executed only when it is determined that the braking force of the vehicle Ve should be prioritized. By setting the target slip ratio of the wheel 3 during the operation of the ABS to the first target slip ratio B1, this flowchart is terminated once.

[0028] In step S2, if it is negatively determined that an earthquake has not occurred, the process proceeds to step S6. In step S6, it is specified that the target slip ratio during the operation of the ABS is not changed from the setting range R1 of the reference target slip ratio B0. When the brake pedal is quickly depressed in a state where an earthquake has not occurred, the ABS with the reference target slip ratio B0 set is activated, maintaining the braking force of the wheel 3 at a high level while suppressing the decrease in the lateral force of the wheel 3. Therefore, it is possible to execute control that shortens the braking distance of the vehicle Ve while ensuring the stability of the vehicle Ve.

[0029] According to the control in another example configured as described above, when an earthquake occurs, the target slip ratio of wheel 3 during ABS operation is set to a first target slip ratio B1 whose setting range is larger than the range at the reference target slip ratio B0. In the setting range of the first target slip ratio B1, since the minimum braking force of wheel 3 is approximately the same as the minimum braking force when wheel 3 locks, the average value of the braking force generated from the brake operation until the vehicle stops is high. Therefore, when an earthquake occurs, it is possible to quickly stop the vehicle Ve while preventing wheel 3 from locking.

[0030] Next, another example of the control executed by the ECU 4 in the embodiment of the present invention will be described with reference to FIG. 5. In the flowchart of still another example described below, step members similar to those already described will be denoted by the same reference numerals and their description will be omitted or simplified.

[0031] In the flowchart shown in FIG. 4, if it is affirmatively determined in step S2 that an earthquake is currently occurring, the process proceeds to step S7. In step S7, it is determined whether the current speed of the vehicle Ve is greater than a predetermined first vehicle speed. This first vehicle speed is set to a relatively high vehicle speed and is mainly determined according to the lateral force of wheel 3 in the setting range R1 of the reference target slip ratio B0 during ABS operation. That is, as described above, as the slip ratio of wheel 3 increases, the lateral force of wheel 3 decreases, and accordingly, the stability of the vehicle Ve decreases. Since the decrease in the stability of the vehicle Ve has a greater impact on the vehicle Ve as the vehicle speed is higher, the first vehicle speed is determined taking this impact into account. If it is affirmatively determined in step S7 that the vehicle speed is greater than the first vehicle speed, the process proceeds to step S8 and the operation of the ABS is permitted.

[0032] In step S8, if the operation of the ABS is permitted, proceed to step S9. In step S9, the target slip ratio of the ABS is set from the reference target slip ratio B0 to the second target slip ratio B2. The setting range of this second target slip ratio B2 is a value larger than the setting range R1 of the reference target slip ratio B0 during the operation of the initially set ABS, and is determined based on the braking force and lateral force of the wheel 3 described above. When the vehicle speed is higher than the first vehicle speed, if the operation of the ABS is prohibited, the lateral force of the wheel 3 may excessively decrease, which may affect the stability of the vehicle Ve. To prevent such a situation, the second target slip ratio B2 is set to a slip ratio that can suppress the decrease in the stability of the vehicle body accompanying the decrease in the lateral force of the wheel 3 while ensuring the braking force of the wheel 3. Once the target slip ratio during the operation of the ABS is set to the second target slip ratio B2, this flowchart is terminated once.

[0033] Conversely, in step S7, when the vehicle speed is less than or equal to the first vehicle speed, proceed to step S10. In step S10, it is determined whether the vehicle speed is greater than the second vehicle speed. This second vehicle speed is set according to the lateral force of the wheel 3 in the same manner as the first vehicle speed. Specifically, the second vehicle speed is set to a vehicle speed at which it can be determined that although it is less than or equal to the first vehicle speed, the lateral force of the wheel 3 can be decreased and the brake device 2 can be controlled to emphasize the braking force. In other words, the second vehicle speed is set to a vehicle speed at which it is possible to determine whether the decrease in the lateral force of the wheel 3 due to the prohibition of the operation of the ABS can be tolerated. When it is affirmatively determined in step S10 because the vehicle speed is greater than the second vehicle speed, proceed to step S11 and permit the operation of the ABS.

[0034] In step S11, if the operation of the ABS is permitted, proceed to step S12. In step S12, set the target slip ratio of the ABS to the third target slip ratio B3. This third target slip ratio B3 is set to a value greater than the second target slip ratio B2. That is, although the vehicle speed is equal to or lower than the first vehicle speed but greater than the second vehicle speed, if the operation of the ABS is prohibited, the lateral force of wheel 3 may excessively decrease. The third target slip ratio B3 is set to a value that can increase the braking force of the vehicle Ve while preventing such a situation. Once the target slip ratio of wheel 3 during ABS operation is set to the third target slip ratio B3, this flowchart is terminated once.

[0035] In step S10, if the vehicle speed is equal to or lower than the second vehicle speed, proceed to step S13. When proceeding to step S13, prohibit the operation of the ABS. That is, it is determined that even if the operation of the ABS is immediately prohibited because the vehicle speed is equal to or lower than the second vehicle speed, the stability of the vehicle Ve will not excessively decrease due to the decrease in the lateral force of wheel 3. Therefore, prohibit the operation of the ABS and terminate this flowchart once.

[0036] Note that in step S2, if it is negatively determined that an earthquake has not occurred, proceed to step S14 and permit the operation of the ABS. Then, proceed to step S15 and terminate this flowchart once without changing the target slip ratio during ABS operation from the reference target slip ratio B0.

[0037] According to the control in still another example configured as described above, when an earthquake occurs, the target slip ratio of the ABS is changed according to the current vehicle speed. Specifically, when the vehicle speed is high, the increase width of the target slip ratio is reduced, and as the vehicle speed decreases, the increase width is increased. Then, when the vehicle speed becomes lower than the second vehicle speed, the operation of the ABS is prohibited. When the vehicle speed is high, the stability of the vehicle Ve decreases, so the target slip ratio is set so that the lateral force of the wheel 3 does not excessively decrease. When the vehicle speed becomes low, the target slip ratio is increased to increase the braking force. Therefore, at the time of an earthquake, the stability of the vehicle Ve can be ensured, the wheel 3 can be prevented from being locked, and the vehicle Ve can be quickly stopped.

Description of Signs

[0038] 2 Brake device 3 Wheel 4 ECU (Controller) 4b Earthquake determination unit

Claims

【Claim 1】 A wheel, a braking device that applies a braking torque to the wheel, an antilock braking system that controls the braking torque of the braking device so that the slip ratio of the wheel with respect to the road surface becomes a predetermined reference target slip ratio, and a control device for a vehicle comprising: a controller that controls the braking device and the antilock braking system, wherein the controller has an earthquake determination unit that detects the occurrence of an earthquake, and when the earthquake determination unit detects the occurrence of the earthquake, the operation of the antilock braking system is prohibited, or a correction target slip ratio larger than the reference target slip ratio is set to operate the antilock braking system. A control device for a vehicle, characterized by the above.

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