Hydraulic brake control method

Abstract

To provide a hydraulic brake control method capable of more effectively damping vibrations.SOLUTION: A hydraulic brake system 10 includes a hydraulic pump 48 that supplies brake fluid to a brake shoe 22, and one or more switching valves 36, 38 that switch the connection state between the hydraulic pump 48 and a master brake cylinder 16. A control method for the hydraulic brake system repeats a communication step of opening and closing the one or more switching valves 36, 38 so as to allow the hydraulic pump 48 to communicate with the master cylinder 16 during a non-braking period, a pump drive step of temporarily driving the hydraulic pump 48 after the communication step, and a recovery step of returning the switching valves 36, 38 to the original state by opening and closing the switching valves after the pump drive step twice or more.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This specification discloses a method for controlling a hydraulic brake that exerts a braking force by hydraulically actuating a brake shoe. [Background technology]

[0002] Hydraulic brakes are widely known and are installed in vehicles, etc. Hydraulic brakes operate a hydraulic pump provided in a hydraulic circuit to transmit hydraulic pressure to brake shoes. The brake shoes are then actuated by the hydraulic pressure to generate a braking force.

[0003] However, hydraulic brakes generate vibrations and noise due to the pulsation of the brake fluid, which can cause discomfort to the driver and other passengers.

[0004] Patent Document 1 discloses a technology for performing gas-liquid separation control to separate the brake fluid into gas and liquid when a certain condition is satisfied in order to suppress vibration and noise of the hydraulic brake. In the gas-liquid separation control, the hydraulic pump is operated while a valve located upstream of the hydraulic pump is kept in a closed state. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-157966 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, a sufficient vibration damping effect could not be obtained with the technology of Patent Document 1. Furthermore, in the case of the technology of Patent Document 1, if the amount of air separated from the gas and liquid is large, there is a risk of another problem occurring in that the braking effect is reduced.

[0007] Therefore, this specification discloses a method for controlling a hydraulic brake that can more effectively suppress vibration. [Means for solving the problem]

[0008] The hydraulic brake control method disclosed in this specification is a control method for a hydraulic brake device having a hydraulic pump that supplies brake fluid to brake shoes and one or more switching valves that switch the connection state between the hydraulic pump and a master cylinder, and is characterized in that during a non-braking period, the method repeats two or more times the following steps: a connection step of opening and closing the one or more switching valves so that the hydraulic pump is connected to the master cylinder, a pump driving step of temporarily driving the hydraulic pump after the connection step, and a recovery step of opening and closing the switching valve to return to the original state after the pump driving step. Effect of the Invention

[0009] By repeatedly opening and closing the switching valve and temporarily driving the hydraulic pump, air bubbles are generated in the brake fluid. These air bubbles suppress the pulsation of the brake fluid, and thus effectively suppress the vibration of the vehicle. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram showing a configuration of a hydraulic brake system. [Diagram 2] 13 is a flowchart showing a flow of a vibration damping process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The configuration of a hydraulic brake system 10 will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of the hydraulic brake system 10. This hydraulic brake system 10 is mounted on a four-wheeled vehicle. The hydraulic brake system 10 includes a brake pedal 18, hydraulic circuits 12f, 12r, and a brake shoe 22. When a user wishes to apply the brakes, the user depresses the brake pedal 18. The depressing force of the brake pedal 18 is amplified by an amplifier 20. The amplifier 20 includes a master brake cylinder 16 and a brake fluid container 14.

[0012] The brake shoes 22 are provided corresponding to each of the four wheels 100. When subjected to hydraulic pressure, the brake shoes 22 come into close contact with a part of the wheel 100. This restricts the rotation of the wheel 100, generating a braking force.

[0013] The hydraulic circuits 12f, 12r are circuits disposed between the master brake cylinder 16 and the brake shoes 22. In this example, the hydraulic circuit 12f is for the front wheels, and the hydraulic circuit 12r is for the rear wheels. Since the two hydraulic circuits 12f, 12r have almost the same configuration, in the following description, they will be referred to as the "hydraulic circuit 12" with the suffixes f and r removed.

[0014] The hydraulic circuit 12 includes a foot brake hydraulic system that transmits hydraulic pressure to the brake shoes 22 in conjunction with the operation of the brake pedal 18, and a non-foot brake hydraulic system that transmits hydraulic pressure to the brake shoes 22 regardless of the operation of the brake pedal 18. The foot brake hydraulic system is composed of an upstream first flow path 24 connected to the master brake cylinder 16, and a downstream first flow path 28 and a downstream second flow path 30 branched from the upstream first flow path 24. The downstream first flow path 28 is connected to the brake shoe 22 of the right wheel 100R, and the downstream second flow path 30 is connected to the brake shoe 22 of the left wheel 100L. A first switching valve 36 is disposed in the upstream first flow path 24. When braking is performed in conjunction with the operation of the brake pedal 18, the first switching valve 36 is opened and a second switching valve 38, which will be described later, is closed. This allows a braking force corresponding to the operation of the brake pedal 18 to be applied to the wheels 100.

[0015] The non-foot brake hydraulic system is composed of the upstream second flow path 26 connected in parallel to the upstream first flow path 24, the downstream first flow path 28 and the downstream second flow path 30, and a hydraulic pump 48. The downstream end of the upstream second flow path 26 is connected to the suction port of the hydraulic pump 48. In addition, the discharge port of the hydraulic pump 48 merges with the upstream first flow path 24 via a relay flow path 56. This merge point is downstream of the first changeover valve 36. By driving the hydraulic pump 48 with the first changeover valve 36 closed and the second changeover valve 38 open, hydraulic pressure is transmitted to the brake shoes 22 regardless of the operation of the brake pedal 18.

[0016] The first downstream flow passage 28 and the second downstream flow passage 30 are provided with a first inlet valve 40 and a second inlet valve 42 capable of switching the wheels 100 to which hydraulic pressure is transmitted. A reservoir 46 is connected to the upstream second flow passage 26 via a check valve 44. The reservoir 46 is further connected to the first downstream flow passage 28 and the second downstream flow passage 30 via a branch flow passage 34. A first outlet valve 52 and a second outlet valve 54 are connected to the branch flow passage 34, which switch the communication between the reservoir 46 and the first downstream flow passage 28 and the second downstream flow passage 30. The hydraulic pressure (brake pressure) acting on the brake shoe 22 is adjusted to an appropriate pressure by the interaction between the pressure retention function of the first inlet valve 40 and the second inlet valve 42 and the pressure reduction function of the first outlet valve 52 and the second outlet valve 54.

[0017] The controller 60 controls the operation of the above-mentioned hydraulic pump 48 and the various valves 36, 38, 40, 42, 52, and 54. The controller 60 is physically a computer having a processor and a memory.

[0018] However, in such a hydraulic brake system 10, vibrations and noises may occur due to hydraulic pulsation and the like. Such vibrations and noises cause discomfort to the driver and other passengers. Therefore, in this example, a vibration suppression process is executed to suppress the pulsation during a non-braking period when the brakes are not applied. This vibration suppression process will be described in detail below.

[0019] 2 is a flowchart showing the flow of the vibration suppression process. In the vibration suppression process, the switching valves 36, 38 are opened and closed and the hydraulic pump 48 is temporarily driven multiple times, thereby increasing the amount of air bubbles in the brake fluid flowing through the hydraulic circuit 12. As the amount of air bubbles increases, the air bubbles act as a kind of damper, suppressing the vibration of the piping that constitutes the hydraulic circuit 12. As the vibration of the piping is suppressed, the vibration and sound transmitted to the vehicle body are also reduced.

[0020] More specifically, when performing the vibration suppression process, the controller 60 first resets a counter (not shown) and then determines whether or not the brakes are currently being applied, i.e., whether or not braking is in progress (S12). If braking is in progress, the vibration suppression process is not executed. On the other hand, if braking is not in progress, the controller 60 closes the first changeover valve 36 and opens the second changeover valve 38 (S14). That is, the controller 60 communicates the hydraulic pump 48 with the master brake cylinder 16 and selects the non-foot brake hydraulic system.

[0021] Then, in this state, the controller 60 temporarily drives the hydraulic pump 48 (S18, 20). The amount of drive of the hydraulic pump 48 at this time is switched depending on the traveling state of the vehicle. Specifically, when the vehicle is traveling (Yes in S16), the controller 60 stops the operation of the hydraulic pump 48 to the extent that the brake shoes 22 do not operate (S18). On the other hand, when the vehicle is stopped (No in S16), the controller 60 drives the hydraulic pump 48 until the brake shoes 22 operate, and then stops the hydraulic pump 48 (S20).

[0022] When the driving of the hydraulic pump 48 stops, the controller 60 closes the second switching valve 38 and opens the first switching valve 36 (S22). That is, the switching valves 36, 38 are returned to their original states. As a result, the hydraulic pressure to the brake shoes 22 is released.

[0023] Thereafter, the controller 60 increments the counter and checks whether or not the count value has reached a predetermined reference number (S24, S26). If the reference number has not been reached, the process returns to step S14, and the opening and closing of the switching valves 36, 38 and the temporary driving of the hydraulic pump 48 are repeated again. The reference number is not particularly limited, but can be selected, for example, between 5 and 500. The reference number is not limited to a fixed value, and may be a variable value that changes according to various conditions. For example, the reference number may change according to the outside air temperature, the driving conditions, etc.

[0024] In any case, air bubbles are effectively generated in the brake fluid by repeatedly opening and closing the switching valves 36, 38 and temporarily driving the hydraulic pump 48. The generation of air bubbles effectively suppresses vibrations in the piping, and ultimately vibrations and noise in the vehicle body.

[0025] When the process of steps S12 to S24 has been repeated a reference number of times (Yes in S26), the controller 60 resets a timer (not shown) (S28) and starts measuring the elapsed time. If the measurement shows that the specified waiting time has elapsed, the process returns to step S10 and the same process is repeated again.

[0026] The reason why the same process is executed after the waiting time has elapsed is to maintain a certain amount of air bubbles. That is, even if a sufficient amount of air bubbles are generated in the brake fluid by the process of steps S10 to S26, the air bubbles will disappear over time. If many of the air bubbles disappear, the vibration damping effect described above will decrease. Therefore, in this example, after a sufficient amount of air bubbles have been generated, the air bubble generation process, i.e., the process of steps S10 to S26, is executed again when a predetermined waiting time has elapsed. This makes it possible to always effectively prevent vibration caused by braking.

[0027] The standby time is not particularly limited, but may be selected within a range of, for example, 3 to 30 minutes. The standby time may be a fixed value or a variable value that changes depending on conditions. For example, the standby time may be changed depending on the outside temperature, the driving conditions, etc.

[0028] In any case, according to the hydraulic brake system 10 disclosed in this specification, air bubbles are generated in the brake fluid, so that vibrations and noise can be effectively suppressed. The above-mentioned configuration is an example, and may be appropriately changed as long as the configuration described in claim 1 is included. For example, the number of times that the switching valves 36 and 38 are opened and closed may be appropriately changed as long as it is two or more times. Also, while the vehicle is traveling, the hydraulic pump 48 may not be driven, and only the switching valves 36 and 38 may be opened and closed. That is, in FIG. 2, if the answer is No in step S16, the process may proceed to step S22 without executing step S18. Even in this case, air bubbles are generated when the switching valves 36 and 38 are opened and closed. [Explanation of symbols]

[0029] 10 hydraulic brake system, 12 hydraulic circuit, 14 brake fluid container, 16 master brake cylinder, 18 brake pedal, 20 amplifier, 22 brake shoe, 24 upstream first flow path, 26 upstream second flow path, 28 downstream first flow path, 30 downstream second flow path, 34 branch flow path, 36 first switching valve, 38 second switching valve, 40 first inlet valve, 42 second inlet valve, 44 check valve, 46 reservoir, 48 hydraulic pump, 52 first outlet valve, 54 second outlet valve, 56 relay flow path, 60 controller, 100 wheel.

Claims

[Claim 1] A method for controlling a hydraulic brake system having a hydraulic pump that supplies brake fluid to a brake shoe and one or more switching valves that switch a connection state between the hydraulic pump and a master cylinder, comprising: During the non-braking period, a communication step of opening and closing the one or more switching valves so that the hydraulic pump is in communication with the master cylinder; a pump driving step of temporarily driving the hydraulic pump after the communicating step; a recovery step of opening and closing the switching valve to return it to its original state after the pump drive step; The above-mentioned control method for hydraulic brakes is characterized in that the above-mentioned is repeated two or more times.

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