Multi-condition hydraulic braking system for vehicles

Abstract

This invention provides a multi-condition hydraulic braking system for vehicles, including a controller, a hydraulic subsystem, an oil control subsystem, and a braking subsystem. The hydraulic subsystem includes a motor, a reservoir, a hydraulic pump, an overflow valve, a check valve, an accumulator, a first pressure sensor, a first isolation valve, and a second isolation valve. The second isolation valve is configured to be normally open. When the braking subsystem is not braking, oil leaking from the outlet of the first isolation valve flows back to the reservoir through the second isolation valve, thereby preventing oil leaking from the outlet of the first isolation valve from flowing into the braking subsystem. This avoids the brake calipers continuously acting on the brake disc in the braking subsystem, preventing drag torque and reducing wear on the brake cylinder. This results in lower vehicle driving resistance, reduced fuel consumption, improved power performance, and improved response accuracy of the braking subsystem, thus enhancing vehicle driving safety.

Description

Technical Field

[0001] This invention relates to the field of vehicle braking technology, and in particular to a multi-condition hydraulic braking system for vehicles. Background Technology

[0002] As a core component ensuring driving safety, the reliability and stability of the vehicle hydraulic braking system are of paramount importance. In the traditional multi-condition hydraulic braking system design, the accumulator, as a pressure energy storage element, is filled with fluid by a hydraulic pump and requires check valves and isolation valves to seal the pressurized oil in order to provide stable hydraulic power to the wheel cylinders under different braking conditions.

[0003] However, research has found that isolation valves are often not completely sealed, and after prolonged operation, pressurized oil may leak through the isolation valve into the brake cylinder. This leakage can cause abnormal pressure build-up in the brake cylinder, which in turn pushes the brake caliper to continuously act on the brake disc, generating unnecessary drag torque. This results in greater wear on the brake cylinder, higher vehicle fuel consumption, and reduced safety. Summary of the Invention

[0004] This invention provides a multi-condition hydraulic braking system for vehicles, which solves the defects of the prior art, such as large wear of the brake cylinder, high vehicle fuel consumption, and poor safety due to leakage of the isolation valve.

[0005] On the one hand, the present invention provides a multi-condition hydraulic braking system for vehicles, which includes a controller, a hydraulic subsystem, an oil control subsystem, and a braking subsystem;

[0006] The hydraulic subsystem includes a motor, a reservoir, a hydraulic pump, a relief valve, a check valve, an accumulator, a first pressure sensor, a first isolation valve, and a second isolation valve.

[0007] The motor is electrically connected to the hydraulic pump and the controller;

[0008] The inlet of the hydraulic pump and the outlet of the relief valve are connected to the reservoir, and the outlet of the hydraulic pump is connected to the inlet of the check valve and the inlet of the relief valve.

[0009] The outlet of the one-way valve and the inlet of the first isolation valve are connected to the accumulator; the first pressure sensor is used to detect the pressure of the accumulator.

[0010] The outlet of the first isolation valve is connected to the oil control subsystem and the inlet of the second isolation valve;

[0011] The oil control subsystem is connected to the braking subsystem;

[0012] The outlet of the second isolation valve is connected to the reservoir; wherein the second isolation valve is configured to be normally open, so that when the braking subsystem is not braking, the oil leaking from the outlet of the first isolation valve flows back to the reservoir through the second isolation valve.

[0013] According to the present invention, a multi-condition hydraulic braking system for vehicles is provided, wherein the oil control subsystem includes a first proportional valve, a second proportional valve, a first pressure relief valve, a second pressure relief valve, and a balance valve; and the braking subsystem includes a first service brake cylinder and a second service brake cylinder.

[0014] The outlet of the first proportional valve is connected to the inlet of the first pressure relief valve, the first opening of the balance valve, and the first service brake cylinder.

[0015] The outlet of the second proportional valve is connected to the inlet of the second pressure relief valve, the second opening of the balance valve, and the second service brake cylinder;

[0016] The outlets of the first pressure relief valve and the second pressure relief valve are connected to the liquid storage tank;

[0017] The controller is configured to control the braking subsystem by controlling the operating states of the target valve and the motor according to different operating conditions, thereby controlling the braking or non-braking operation of the braking subsystem; wherein the target valve includes at least one of the first isolation valve, the second isolation valve, the first proportional valve, the second proportional valve, the first pressure relief valve, the second pressure relief valve, and the balance valve.

[0018] According to the present invention, a multi-condition hydraulic braking system for vehicles includes an accumulator replenishment condition.

[0019] When the pressure value detected by the first pressure sensor is less than the first preset pressure value, the motor starts, causing the motor to drive the hydraulic pump to replenish the accumulator until the pressure value detected by the first pressure sensor is greater than the second preset pressure value, at which point the motor stops running.

[0020] Among them, the first isolation valve, the second isolation valve, the first proportional valve, the second proportional valve, the first pressure relief valve, the second pressure relief valve, and the balance valve are all de-energized.

[0021] According to the present invention, a multi-condition hydraulic braking system for vehicles includes a non-braking driving condition.

[0022] When there is no driving brake percentage command, the first isolation valve, the second isolation valve, the first proportional valve, the second proportional valve, the first pressure relief valve, the second pressure relief valve, and the balance valve are all de-energized. The motor determines whether to work based on the pressure of the accumulator. The first proportional valve and the second proportional valve both output a first adjustment ratio signal that is less than a preset ratio, so that the pressure of the first driving brake cylinder and the pressure of the second driving brake cylinder are both less than or equal to a third preset pressure.

[0023] According to the present invention, a multi-condition hydraulic braking system for vehicles includes a pressure-boosting braking condition on a straight road and a pressure-reducing braking condition on a straight road.

[0024] Under the flat road condition boost braking condition, the first isolation valve is energized and turned on, the second isolation valve is energized and turned off, the first proportional valve and the second proportional valve output a second adjustment ratio signal, and the balance valve is not energized and remains turned on, so that the pressure of the first service brake cylinder and the pressure of the second service brake cylinder both meet the pressure corresponding to the second adjustment ratio signal.

[0025] Under the pressure relief braking condition on a straight road, the first isolation valve is de-energized and closed, the second isolation valve is energized and closed, the first proportional valve and the second proportional valve output a third adjustment proportional signal, the balance valve is de-energized and remains conductive, and the first pressure relief valve and the second pressure relief valve are intermittently energized and conductive, so that the pressure of the first service brake cylinder and the pressure of the second service brake cylinder both meet the pressure corresponding to the third adjustment proportional signal; wherein, the pressure corresponding to the third adjustment proportional signal is less than the pressure corresponding to the second adjustment proportional signal.

[0026] According to the present invention, a multi-condition hydraulic braking system for vehicles includes a long downhill braking condition.

[0027] When it is detected that the duration of the vehicle's boost braking is greater than the first preset duration, and the change in the pedal position is less than the preset change value, the first proportional valve and the second proportional valve are adjusted to the set control current, the first isolation valve is de-energized and closed, the second isolation valve is energized and closed, and the first pressure relief valve and the second pressure relief valve are de-energized and remain closed.

[0028] When the detected change in the pedal position exceeds the preset change value, the long downhill braking condition is released, and the operating condition is switched according to the change in the pedal position.

[0029] According to the present invention, a multi-condition hydraulic braking system for vehicles is provided, wherein the conditions include a turning braking condition, and the turning braking condition includes a turning boost braking condition and a turning depressurization braking condition;

[0030] Under the aforementioned turning braking condition, the pressure of the inner service brake cylinder and the pressure of the outer service brake cylinder are distributed according to the turning direction, such that the pressure of the outer service brake cylinder is greater than that of the inner service brake cylinder; wherein, when the turning direction is left turn, the first service brake cylinder is the inner service brake cylinder and the second service brake cylinder is the outer service brake cylinder; when the turning direction is right turn, the first service brake cylinder is the outer service brake cylinder and the second service brake cylinder is the inner service brake cylinder;

[0031] In the case of turning and boosting braking, the first isolation valve is energized and open, the second isolation valve is energized and closed, the first pressure relief valve and the second pressure relief valve are not energized and remain closed, the balance valve is energized and closed, the first proportional valve outputs a fourth proportional adjustment signal, and the second proportional valve and the first proportional valve output a fifth proportional adjustment signal, so that the pressure of the first service brake cylinder is different from the pressure of the second service brake cylinder.

[0032] During cornering and decompression braking, the first isolation valve is de-energized and closed, the second isolation valve is energized and closed, the balance valve is energized and closed, the first proportional valve outputs a sixth proportional adjustment signal, and the second proportional valve outputs a seventh proportional adjustment signal, causing the pressure of the first service brake cylinder to be different from the pressure of the second service brake cylinder. The first pressure relief valve and the second pressure relief valve are intermittently energized and connected, so that the pressure of the first service brake cylinder meets the pressure corresponding to the sixth proportional adjustment signal, and the pressure of the second service brake cylinder meets the pressure corresponding to the seventh proportional adjustment signal.

[0033] According to the present invention, a multi-condition hydraulic braking system for a vehicle further includes a second pressure sensor and a third pressure sensor.

[0034] The second pressure sensor is used to detect the pressure of the first service brake cylinder, and the third pressure sensor is used to detect the pressure of the second service brake cylinder;

[0035] The operating conditions include continuous braking automatic pressure reduction operating conditions;

[0036] If the pressure of the first service brake cylinder is greater than the required pressure of the first service brake cylinder, and / or the pressure of the second service brake cylinder is greater than the required pressure of the second service brake cylinder, automatic pressure reduction shall be performed;

[0037] Specifically, the first isolation valve is de-energized and closed, the second isolation valve is energized and closed, the first pressure relief valve and the second pressure relief valve are intermittently energized and connected, and the balance valve maintains the state before automatic pressure reduction.

[0038] According to the present invention, a multi-condition hydraulic braking system for vehicles includes a pressure-holding condition.

[0039] Under the pressure-holding condition, if the pressure of the first service brake cylinder is greater than the fourth preset pressure but less than the required pressure of the first service brake cylinder, the first isolation valve is energized and opened, the second isolation valve is energized and closed, the balance valve is energized and closed, the first proportional valve is energized and closed, and the second proportional valve remains in its original state to maintain the pressure of the first service brake cylinder; if the pressure of the second service brake cylinder is greater than the fourth preset pressure but less than the required pressure of the second service brake cylinder, the first isolation valve is energized and opened, the second isolation valve is energized and closed, the balance valve is energized and closed, the second proportional valve remains in its original state to maintain the pressure of the second service brake cylinder.

[0040] According to the present invention, a multi-condition hydraulic braking system for vehicles includes a pressure holding and then pressure depressurization condition.

[0041] Under the pressure-holding and pressure-reducing condition, if after the first service brake cylinder has entered the pressure-holding condition for a second preset time, the pressure of the first service brake cylinder is greater than the fifth preset pressure and less than the fourth preset pressure, the first isolation valve is energized and opened, the second isolation valve is energized and closed, the balance valve is energized and closed, the first proportional valve is energized and closed, the second proportional valve remains in its original state, and the first pressure relief valve is intermittently energized and opened to relieve pressure on the first service brake cylinder; if after the first service brake cylinder has entered the pressure-holding condition for a second preset time, the pressure of the second service brake cylinder is greater than the fifth preset pressure and less than the fourth preset pressure, the first isolation valve is energized and opened, the second isolation valve is energized and closed, the balance valve is energized and closed, the second proportional valve is energized and closed, the first proportional valve remains in its original state, and the second pressure relief valve is intermittently energized and opened to relieve pressure on the second service brake cylinder.

[0042] The multi-condition hydraulic braking system for vehicles provided by this invention includes a normally open second isolation valve ZLV2 located between the outlet side of the first isolation valve ZLV1 and the reservoir C. When the braking subsystem is not in use, oil leaking from the outlet of the first isolation valve ZLV1 flows back to the reservoir C through the second isolation valve ZLV2, preventing leaked oil from the first isolation valve ZLV1 from flowing into the braking subsystem. This avoids the brake calipers continuously acting on the brake disc, preventing drag torque and reducing wear on the brake cylinders. This results in lower vehicle drag, reduced fuel consumption, improved power performance, and enhanced response accuracy of the braking subsystem, thus improving vehicle safety. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the structure of the vehicle multi-condition hydraulic braking system provided in an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the vehicle operating under no-braking conditions;

[0046] Figure 3 This is a schematic diagram of the boost braking operation on a straight road.

[0047] Figure 4 This is a schematic diagram of the decompression braking operation on a straight road.

[0048] Figure 5 This is a schematic diagram of the braking principle for long downhill slopes;

[0049] Figure 6 This is a schematic diagram of the braking principle during cornering with boost pressure.

[0050] Figure 7 This is a schematic diagram of the braking principle during cornering with pressure relief.

[0051] Figure 8 This is a schematic diagram of the braking operation when the accumulator pressure is insufficient.

[0052] Figure 9 This is the schematic diagram of the pressure holding condition corresponding to the first service brake cylinder L;

[0053] Figure 10 This is the schematic diagram of the pressure holding condition corresponding to the second service brake cylinder R;

[0054] Figure 11 This is the schematic diagram of the decompression working condition corresponding to the first service brake cylinder L;

[0055] Figure 12 This is the schematic diagram of the decompression condition corresponding to the second service brake cylinder R. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0057] Figure 1 This is a structural schematic diagram of the multi-condition hydraulic braking system for vehicles provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the vehicle multi-condition hydraulic braking system of this embodiment may include a controller (not shown in the figure), a hydraulic subsystem, an oil control subsystem, and a braking subsystem. The hydraulic subsystem includes a motor M, a reservoir C, a hydraulic pump PUMP, an overflow valve RV, a check valve CV, an accumulator ACC, a first pressure sensor PU1, a first isolation valve ZLV1, and a second isolation valve ZLV2.

[0058] In one specific implementation, the motor M is electrically connected to the hydraulic pump PUMP and the controller; the inlet of the hydraulic pump PUMP and the outlet of the relief valve RV are connected to the reservoir C; the outlet of the hydraulic pump PUMP is connected to the inlet of the check valve CV and the inlet of the relief valve RV; the outlet of the check valve CV and the inlet of the first isolation valve ZLV1 are connected to the accumulator ACC; the first pressure sensor PU1 is used to detect the pressure of the accumulator ACC; the outlet of the first isolation valve ZLV1 is connected to the oil control subsystem and the inlet of the second isolation valve ZLV2; the oil control subsystem is connected to the braking subsystem; and the outlet of the second isolation valve ZLV2 is connected to the reservoir C.

[0059] In one specific implementation, the second isolation valve ZLV2 is configured to be normally open. When the braking subsystem is not braking, the oil leaking from the outlet of the first isolation valve ZLV1 flows back to the reservoir C through the second isolation valve ZLV2. This prevents the leaking oil from the outlet of the first isolation valve ZLV1 from flowing into the braking subsystem, avoiding continuous action of the brake calipers on the brake disc, thus preventing drag torque, reducing wear on the brake cylinders, decreasing vehicle rolling resistance, reducing fuel consumption, improving power performance, and enhancing the response accuracy of the braking subsystem, thereby improving vehicle safety.

[0060] See also Figure 1 The oil control subsystem includes a first proportional valve EV1, a second proportional valve EV2, a first pressure relief valve AV1, a second pressure relief valve AV2, and a balance valve BV; the braking subsystem includes a first service brake cylinder L and a second service brake cylinder R.

[0061] The outlet of the first proportional valve EV1 is connected to the inlet of the first pressure relief valve AV1, the first opening of the balance valve BV, and the first service brake cylinder L.

[0062] The outlet of the second proportional valve EV2 is connected to the inlet of the second pressure relief valve AV2, the second opening of the balance valve BV, and the second service brake cylinder R;

[0063] The outlet of the first pressure relief valve AV1 and the outlet of the second pressure relief valve AV2 are connected to the liquid storage tank C;

[0064] In one specific implementation, the controller is configured to control the braking subsystem by controlling the operating states of the target valve and the motor M according to different operating conditions; wherein, the target valve includes at least one of the first isolation valve ZLV1, the second isolation valve ZLV2, the first proportional valve EV1, the second proportional valve EV2, the first pressure relief valve AV1, the second pressure relief valve AV2, and the balance valve BV.

[0065] Specifically, the operating condition includes the accumulator ACC replenishment condition. See also... Figure 1 Under this operating condition, when the pressure value detected by the first pressure sensor PU1 is less than the first preset pressure value (which can be 12 MPa), the motor M starts, causing the motor M to drive the hydraulic pump PUMP to replenish the accumulator ACC with fluid, until the pressure value detected by the first pressure sensor PU1 is greater than the second preset pressure value (which can be 14 MPa), at which point the motor M stops running; wherein, the first isolation valve ZLV1, the second isolation valve ZLV2, the first proportional valve EV1, the second proportional valve EV2, the first pressure relief valve AV1, the second pressure relief valve AV2, and the balance valve BV are all de-energized. See the corresponding oil circuit flow path for details. Figure 1 The red part in the middle.

[0066] In other words, under this operating condition, after the vehicle starts, the system confirms the status of the accumulator ACC and obtains the pressure value detected by the first pressure sensor PU1 (i.e., the pressure value of the accumulator ACC). At the same time, when the pressure value of the accumulator ACC is detected to be less than 12MPa during normal vehicle operation, the accumulator ACC fluid replenishment mode is activated. At this time, the first isolation valve ZLV1, the second isolation valve ZLV2, the first pressure relief valve AV1, the second pressure relief valve AV2, the first proportional valve EV1, the second proportional valve EV2, and the balance valve BV are all de-energized and remain in normal condition. The motor M is energized and rotates to drive the gear pump to replenish the accumulator ACC fluid until the pressure is greater than 14MPa and then stops.

[0067] It should be noted that the accumulator ACC replenishment operation is described separately here. In actual applications, the accumulator ACC replenishment operation can also be carried out simultaneously in other operating conditions, which will not be described in detail here.

[0068] In a specific implementation, the operating conditions include a non-braking driving condition. In this condition, when there is no driving brake percentage command, the first isolation valve ZLV1, the second isolation valve ZLV2, the first proportional valve EV1, the second proportional valve EV2, the first pressure relief valve AV1, the second pressure relief valve AV2, and the balance valve BV are all de-energized. The motor M determines whether to operate based on the accumulator pressure. The first proportional valve EV1 and the second proportional valve EV2 both output a first adjustment ratio signal (the value corresponding to the first adjustment ratio is less than a preset ratio, which can be 0), so that the pressure of the first driving brake cylinder L and the pressure of the second driving brake cylinder R are both less than or equal to a third preset pressure (the third preset pressure can be 0). For details, please refer to... Figure 2 , Figure 2 This is a schematic diagram of the vehicle operating under unbraked conditions. Figure 2 The medium-pressure oil is blocked by the check valve CV and the first isolation valve ZLV1.

[0069] In other words, the controller does not output the "driving brake percentage command" (driving brake percentage = 0). At this time, the motor M, the first isolation valve ZLV1, the second isolation valve ZLV2, the first pressure relief valve AV1, the second pressure relief valve AV2, the balance valve BV, and the motor M are all de-energized. The output signal ratio of the first proportional valve EV1 and the second proportional valve EV2 is 0. The driving brake cylinder is unloaded, and the pressure inside the driving brake cylinder is close to 0. 12MPa≤pressure of the first parking brake cylinder / pressure of the second parking brake cylinder≤14MPa, and the parking brake cylinder oil circuit maintains pressure.

[0070] In a specific implementation, the operating conditions include boost braking on straight roads and depressurization braking on straight roads. Here, "straight roads" refers to road conditions under normal circumstances, excluding road conditions such as long downhill slopes and curves.

[0071] Figure 3 This is a schematic diagram of the boost braking operation on a straight road, such as... Figure 3 As shown, under the pressure-boosting braking condition on a straight road, the first isolation valve ZLV1 is energized and open, the second isolation valve ZLV2 is energized and closed, the first proportional valve EV1 and the second proportional valve EV2 output a second adjustment ratio signal, and the balance valve BV remains closed, ensuring that the pressure of the first service brake cylinder L and the pressure of the second service brake cylinder R both meet the pressure corresponding to the second adjustment ratio signal. The pressure of the first service brake cylinder L and the pressure of the second service brake cylinder R can both be expressed as: 10 MPa × brake signal percentage % ± 0.5 MPa. Wherein, the brake signal percentage % is the value corresponding to the second adjustment ratio signal. Under this condition, the oil circuit flow is as follows... Figure 3 As shown by the red line in the middle.

[0072] In other words, under this operating condition, the second isolation valve ZLV2 is energized and closed, while the first isolation valve ZLV1 is energized and opened, supplying hydraulic fluid to the first proportional valve EV1 and the second proportional valve EV2. The first and second proportional valves EV1 and EV2 output a pressure percentage based on the adjustment ratio signal given by the controller. At this time, the balance valve is normally open, ensuring that the pressure in both left and right wheel brake cylinders equals 10MPa * brake signal percentage % ± 0.5MPa. When the required pressure is reached, the first isolation valve ZLV1 disconnects and remains open. During the brake holding process, due to hydraulic valve leakage, the brake pressure may decrease. When the brake pressure falls below the required pressure, the first isolation valve ZLV1 is energized and opens to replenish the brake cylinders. The first and second pressure relief valves AV1 and AV2 are both de-energized and remain closed.

[0073] Figure 4 This is a schematic diagram of the decompression and braking operation on a straight road. (For example...) Figure 4 As shown, under the pressure-reducing braking condition on a straight road, the first isolation valve ZLV1 is de-energized and closed, the second isolation valve ZLV2 is energized and closed, the first proportional valve EV1 and the second proportional valve EV2 output a third adjustment proportional signal, the balance valve BV is de-energized and remains conductive, and the first pressure relief valve AV1 and the second pressure relief valve AV2 are intermittently energized and conductive, so that the pressure of the first service brake cylinder L and the pressure of the second service brake cylinder R both meet the pressure corresponding to the third adjustment proportional signal; wherein, the pressure corresponding to the third adjustment proportional signal is less than the pressure corresponding to the second adjustment proportional signal. Under this condition, the flow status of the oil circuit is as follows: Figure 4 As shown by the red line in the middle.

[0074] In other words, when the controller sends a pressure reduction braking program and the "service braking percentage command" begins to decrease, the first isolation valve ZLV1 is de-energized and closed, and the second isolation valve ZLV2 is energized and closed to ensure that the pressure in the brake cylinder does not increase. The first proportional valve EV1 and the second proportional valve EV2 output a certain percentage of pressure according to the adjustment ratio signal given by the controller. At this time, the balance normal is open. The first pressure relief valve AV1 and the second pressure relief valve AV2 adjust the opening time through pulse width modulation (PWM) technology to slowly reduce the pressure in the brake cylinder until the pressure specified by the "service braking percentage command" is met. At this time, the pressure of both left and right wheel brake cylinders is 10MPa * brake signal percentage % ± 0.5MPa.

[0075] In one specific implementation, the operating conditions include long downhill braking conditions. Figure 5This is a schematic diagram of the braking principle for a long downhill slope. When the duration of the vehicle's boost braking is detected to be greater than a first preset duration, and the change in the pedal depressor position is less than a preset change value, the first proportional valve EV1 and the second proportional valve EV2 are adjusted to the set control current. The first isolation valve ZLV1 is de-energized and closed, the second isolation valve ZLV2 is energized and closed, and the first pressure relief valve AV1 and the second pressure relief valve AV2 remain closed. When the change in the pedal depressor position is detected to be greater than the preset change value, the long downhill braking condition is released, and the braking condition is switched according to the change in the pedal depressor position. Figure 5 The red line in the middle shows the oil circuit diagram under this operating condition.

[0076] In other words, when it is detected that the vehicle is under pressure braking for a long time and the pedal position remains basically unchanged, in order to avoid the EV valve being energized for a long time and improve the system reliability, the long downhill braking condition will be activated. At this time, after the first proportional valve EV1 and the second proportional valve EV2 are adjusted to the intended control current, the first isolation valve ZLV1 is de-energized and closed, the second isolation valve ZLV2 is energized and closed, and the first pressure relief valve AV1 and the second pressure relief valve AV2 remain closed to maintain the pressure at the brake caliper and achieve long-distance downhill braking.

[0077] In a specific implementation process, when a significant change in the position of the foot pedal is detected, it indicates that the operating condition is different from the actual braking requirements of the vehicle. At this time, the long slope braking condition can be deactivated, and the operating condition can be switched according to the change in the foot pedal. The specific operating condition to switch to can be selected according to the actual situation. For example, it can be switched to the flat road pressure boosting braking condition, the flat road pressure decompression braking condition, etc., which will not be listed here.

[0078] In a specific implementation process, the operating conditions include a turning braking condition, which includes a turning boost braking condition and a turning depressurization braking condition.

[0079] Under the aforementioned turning braking condition, the pressure of the inner service brake cylinder and the pressure of the outer service brake cylinder are distributed according to the turning direction, such that the pressure of the outer service brake cylinder is greater than that of the inner service brake cylinder; wherein, when the turning direction is left turn, the first service brake cylinder L is the inner service brake cylinder and the second service brake cylinder R is the outer service brake cylinder; when the turning direction is right turn, the first service brake cylinder L is the outer service brake cylinder and the second service brake cylinder R is the inner service brake cylinder.

[0080] Specifically, the pressure of the inner service brake cylinder and the pressure of the outer service brake cylinder can be distributed in the following manner:

[0081] (1) Obtain the steering angle of the steering wheel, vehicle speed, road surface adhesion coefficient, vehicle center of gravity height, track width and wheelbase;

[0082] The steering angle can be obtained through a steering wheel angle sensor, and the vehicle speed can be obtained by combining it with a vehicle speed sensor. The road surface adhesion coefficient can be estimated based on the vehicle speed. The track width and wheelbase can be obtained through the vehicle's structure.

[0083] (2) Based on the preset formula for calculating the outer pressure distribution coefficient, the outer pressure distribution coefficient is calculated using the steering angle, vehicle speed, road surface adhesion coefficient, vehicle center of gravity height, wheel track and wheelbase.

[0084] The formula for calculating the outer pressure distribution coefficient is as follows:

[0085]

[0086] in, Indicates the outer pressure distribution coefficient. Indicates the steering angle. Indicates vehicle speed. Indicates the road surface adhesion coefficient. Indicates the reference road surface adhesion coefficient. This indicates the height of the vehicle's center of gravity (the higher the center of gravity, the greater the risk of rollover and the greater the need for lateral pressure compensation). It indicates the wheel track (the distance between the center of the left and right wheels; the wider the wheel track, the weaker the load transfer and the better the stability). This indicates the wheelbase (the distance between the center of the front and rear axles, which affects the turning radius and lateral acceleration). Represents gravitational acceleration. The nonlinear correction index can range from 0.8 to 1.2. On wet, slippery surfaces, the effect of μ on pressure distribution is nonlinear, necessitating mitigation of the risk of over-distribution. Indicates the dynamic correction factor. It indicates the steering angular velocity (reflecting how quickly you turn the steering wheel; when making a sharp turn, you need to quickly increase the pressure on the outside of the steering wheel). This indicates longitudinal deceleration (during emergency braking, the external pressure needs to be increased to balance the inertial force).

[0087] It should be noted that constraints can be applied using the following calculation formula:

[0088]

[0089] In other words, This causes the pressure in the outer service brake cylinder to be greater than the pressure in the inner service brake cylinder.

[0090] (3) Based on the outer pressure distribution coefficient, determine the pressure of the inner service brake cylinder and the pressure of the outer service brake cylinder.

[0091] In a specific implementation process, the pressure of the inner service brake cylinder and the pressure of the outer service brake cylinder can be obtained according to the following pressure distribution calculation formula:

[0092]

[0093] in, This indicates the pressure of the outer service brake cylinder. This indicates the pressure of the inner service brake cylinder. Indicates the maximum pressure that can be provided. Indicates the percentage of braking signal.

[0094] Figure 6 This is a schematic diagram of the braking principle during cornering with boost pressure, such as... Figure 6 As shown, under the turning and boosting braking condition, the first isolation valve ZLV1 is energized and open, the second isolation valve ZLV2 is energized and closed, the first pressure relief valve AV1 and the second pressure relief valve AV2 are not energized and remain closed, the balance valve BV is energized and closed, the first proportional valve EV1 outputs a fourth proportional adjustment signal, the second proportional valve EV2 and the first proportional valve EV1 output a fifth proportional adjustment signal, so that the pressure of the first service brake cylinder L is different from the pressure of the second service brake cylinder R. Under this condition, the oil circuit flow path can be seen in [reference needed]. Figure 6 The red line in the middle.

[0095] In other words, when the vehicle is under cornering and pressurized braking, the controller can distribute the braking pressure of the left and right wheels according to the cornering direction, so that the braking pressure of the outer wheel is greater than that of the inner wheel, thereby making full use of the wheel's adhesion. At this time, the first isolation valve ZLV1 is energized and opened, the second isolation valve ZLV2 is energized and closed, the first pressure relief valve AV1 and the second pressure relief valve AV2 are de-energized and remain closed, and the balance valve BV is energized and closed to ensure that the left and right wheels can achieve different braking pressures. The first proportional valve EV1 and the second proportional valve EV2 output a certain percentage of pressure according to the adjustment ratio signal given by the controller.

[0096] Figure 7 This is a schematic diagram of the braking principle during cornering, such as... Figure 7As shown, under the turning decompression braking condition, the first isolation valve ZLV1 is de-energized and closed, the second isolation valve ZLV2 is energized and closed, the balance valve BV is energized and closed, the first proportional valve EV1 outputs a sixth proportional adjustment signal, and the second proportional valve EV2 outputs a seventh proportional adjustment signal. This causes the pressure of the first service brake cylinder L to differ from the pressure of the second service brake cylinder R. The first pressure relief valve AV1 and the second pressure relief valve AV2 are intermittently energized and conducting, ensuring that the pressure of the first service brake cylinder L meets the pressure corresponding to the sixth proportional adjustment signal, and that the pressure of the second service brake cylinder R meets the pressure corresponding to the seventh proportional adjustment signal. Under this condition, the oil circuit flow path can be seen in [reference needed]. Figure 7 The red line in the middle.

[0097] In other words, when the vehicle is in a turning decompression braking state, upon receiving the decompression braking program from the controller, when the "service brake percentage command" begins to decrease (at this time, the service pressure signals of the two wheels are different), the first isolation valve ZLV1 is de-energized and closed, and the second isolation valve ZLV2 is energized and closed to ensure that the pressure in the brake cylinder does not increase. The balance valve BV is energized and closed. The first pressure relief valve AV1 and the second pressure relief valve AV2 adjust their opening time through PWM to slowly reduce the pressure in the brake cylinder until the pressure specified by the "service brake percentage command" is met. At this time, the pressure of the left and right wheel brake cylinders is different. Specifically, the brake pressure = 10MPa * brake signal percentage% ± 0.5MPa.

[0098] like Figures 1 to 7 As shown, the vehicle's multi-condition hydraulic braking system may further include a second pressure sensor PU2 and a third pressure sensor PU3. The second pressure sensor PU2 is used to detect the pressure of the first service brake cylinder L, and the third pressure sensor PU3 is used to detect the pressure of the second service brake cylinder R.

[0099] In one specific implementation, the operating conditions include a continuous braking automatic pressure reduction condition; under this condition, if the pressure of the first service brake cylinder L is greater than the required pressure of the first service brake cylinder L, and / or the pressure of the second service brake cylinder R is greater than the required pressure of the second service brake cylinder R, automatic pressure reduction is performed; wherein, the first isolation valve ZLV1 is de-energized and closed, the second isolation valve ZLV2 is energized and closed, the first pressure relief valve AV1 and the second pressure relief valve AV2 are intermittently energized and connected, and the balance valve BV maintains the state before automatic pressure reduction.

[0100] In other words, when the vehicle performs continuous braking, the oil temperature in the first service brake cylinder L and / or the second service brake cylinder R will rise, resulting in an increase in system pressure. When the pressure of the first service brake cylinder L is detected to be higher than the required value range given to the first proportional valve EV1 by the controller, and / or the pressure of the second service brake cylinder R is higher than the required value range given to the second proportional valve EV2 by the controller, the automatic pressure reduction mode is activated. The first pressure relief valve AV1 and the second pressure relief valve AV2 are controlled by PWM wave to reduce the system pressure to the required pressure. At this time, the first proportional valve EV1 and the second proportional valve EV2 are in the stopped pressurization state, the first isolation valve ZLV1 is de-energized and closed, the second isolation valve ZLV2 is energized and closed, and the state of the balance valve BV remains the same as before the pressure reduction.

[0101] In a specific implementation, the braking process may also include a braking condition due to insufficient accumulator pressure. In this condition, when the vehicle is braking and the accumulator pressure drops below 12 MPa due to braking, this condition is initiated. At this time, the motor is energized, the ZLV1 valve is energized and opened, and the ZLV2 valve is energized and closed. Simultaneously with braking, the motor is activated to replenish fluid to the accumulator, ensuring the highest possible braking pressure for subsequent braking. See also... Figure 8 , Figure 8 This is a schematic diagram of the braking principle under insufficient accumulator pressure. The oil flow path under this condition can be found in [reference needed]. Figure 8 The red line in the middle.

[0102] In a specific implementation process, the operating conditions include pressure holding conditions. Figure 9 This is the schematic diagram of the pressure holding condition corresponding to the first service brake cylinder L, i.e., the pressure holding condition of the left wheel. Figure 9 As shown, under the left wheel pressure-holding condition, if the pressure of the first service brake cylinder L is greater than the fourth preset pressure but less than the required pressure of the first service brake cylinder L, the first isolation valve ZLV1 is energized and opened, the second isolation valve ZLV2 is energized and closed, the balance valve BV is energized and closed, the first proportional valve EV1 is energized and closed, and the second proportional valve EV2 remains in its original state to maintain the pressure of the first service brake cylinder L. Under this condition, the oil circuit flow path can be found in [reference needed]. Figure 9 The red line in the diagram indicates the oil flow path during the depressurization of the second service brake cylinder R. (See [link to relevant documentation]). Figure 9 The blue line in the middle.

[0103] In other words, when the pressure value of the left wheel of the vehicle is detected to be too high, which may cause the wheel to lock up, the left wheel pressure holding mode is activated. At this time, the second isolation valve ZLV2 is energized and closed, the first isolation valve ZLV1 is energized and opened, the balance is energized and closed to make the pressure of the left and right wheels different, the first proportional valve EV1 stops increasing the pressure to the left wheel, and the second proportional valve EV2 outputs a certain percentage of pressure according to the adjustment ratio signal given by the controller to maintain the pressure and braking status of the left and right wheels respectively. All other valves remain in normal state.

[0104] Figure 10 This is the schematic diagram of the pressure holding condition corresponding to the second service brake cylinder R, i.e., the right wheel pressure holding condition. Figure 10 As shown, if the pressure of the second service brake cylinder R is greater than the fourth preset pressure but less than the required pressure of the second service brake cylinder R, the first isolation valve ZLV1 is energized and opened, the second isolation valve ZLV2 is energized and closed, the balance valve BV is energized and closed, the second proportional valve EV2 is energized and closed, and the first proportional valve EV1 remains in its original state to maintain the pressure of the second service brake cylinder R. Under this operating condition, the oil circuit flow path can be found in [reference needed]. Figure 10 The red line in the diagram indicates the oil flow path during the depressurization of the second service brake cylinder R. (See [link to relevant documentation]). Figure 10 The blue line in the middle.

[0105] In other words, when the right wheel pressure value of the vehicle is detected to be too high, which may cause wheel lock-up, the right wheel pressure holding mode is activated. At this time, the second isolation valve ZLV2 is energized and closed, the first isolation valve ZLV1 is energized and opened, the balance is energized and closed to make the left and right wheel pressures different, the second proportional valve EV2 stops increasing pressure to the right wheel, and the first proportional valve EV1 outputs a certain percentage of pressure according to the adjustment ratio signal given by the controller to maintain the pressure and braking status of the left and right wheels respectively. All other valves remain in normal state.

[0106] In a specific implementation process, the operating conditions include pressure holding followed by pressure reduction. Figure 11 This is the schematic diagram of the decompression condition corresponding to the first service brake cylinder L, that is, the decompression condition after the left wheel has maintained pressure, as shown below. Figure 11 As shown, under the pressure-holding and pressure-reducing condition of the left wheel, if the pressure of the first service brake cylinder L is greater than the fifth preset pressure and less than the fourth preset pressure after the first service brake cylinder L has entered the pressure-holding condition for a second preset time, the first isolation valve ZLV1 is energized and opened, the second isolation valve ZLV2 is energized and closed, the balance valve BV is energized and closed, the first proportional valve EV1 is energized and closed, the second proportional valve EV2 remains in its original state, and the first pressure relief valve AV1 is intermittently energized and opened to relieve pressure on the first service brake cylinder L. Under this condition, the oil circuit flow path can be found in [reference needed]. Figure 11 The red line in the diagram indicates the oil flow path during the depressurization of the second service brake cylinder R. (See [link to relevant documentation]). Figure 11 The green line in the middle.

[0107] In other words, if the brake pressure is still too high after the left wheel of the vehicle enters the pressure holding state, it will enter the left wheel decompression state. At this time, the balance is turned off, the first proportional valve EV1 stops increasing the pressure to the left wheel, and the first pressure relief valve AV1 opens intermittently to reduce the brake pressure to meet the requirements.

[0108] Figure 12 This is the schematic diagram of the decompression condition corresponding to the second service brake cylinder R, that is, the decompression condition after the right wheel pressure is maintained, as shown below. Figure 12 As shown, if after the first service brake cylinder L enters the pressure-holding state for a second preset time, the pressure of the second service brake cylinder R is greater than the fifth preset pressure but less than the fourth preset pressure, the first isolation valve ZLV1 is energized and opened, the second isolation valve ZLV2 is energized and closed, the balance valve BV is energized and closed, the second proportional valve EV2 is energized and closed, the first proportional valve EV1 remains in its original state, and the second pressure relief valve AV2 is intermittently energized and opened to relieve pressure on the second service brake cylinder R. Under this condition, the oil circuit flow path can be found in [reference needed]. Figure 12 The red line in the diagram indicates the oil flow path during the depressurization of the second service brake cylinder R. (See [link to relevant documentation]). Figure 12 The green line in the middle.

[0109] In other words, if the braking pressure is still too high after the right wheel of the vehicle enters the ABS pressure holding state, it will enter the right wheel decompression state. At this time, the balance power is turned off, the second proportional valve EV2 stops increasing pressure to the right wheel, and the first pressure relief valve AV1 opens intermittently to reduce the braking pressure to meet the requirements.

[0110] In a specific implementation process, the energization status of each valve corresponding to each of the above operating conditions can be found in Table 1:

[0111] Table 1 shows the energization status of each valve under various operating conditions.

[0112]

[0113] In this embodiment of the vehicle multi-condition hydraulic braking system, a normally open second isolation valve ZLV2 is installed between the outlet side of the first isolation valve ZLV1 and the reservoir C. This allows oil leaking from the outlet of the first isolation valve ZLV1 to flow back to the reservoir C through the second isolation valve ZLV2 when the braking subsystem is not in use. This prevents leaked oil from the first isolation valve ZLV1 from flowing into the braking subsystem, avoiding continuous action of the brake calipers on the brake disc, preventing drag torque, reducing wear on the brake cylinders, decreasing vehicle driving resistance, reducing fuel consumption, improving power performance, and enhancing the response accuracy of the braking subsystem, thus improving vehicle driving safety.

[0114] In a specific implementation process, the vehicle's multi-condition hydraulic braking system can also perform vehicle start-up checks and vehicle checks while driving.

[0115] Specifically, vehicle start-up checks include the following aspects:

[0116] 1) Confirm the status of accumulator ACC: Check the pressure value of accumulator ACC. If the pressure value of accumulator ACC is lower than 12MPa, start the motor M of the hydraulic subsystem to drive the hydraulic pump PUMP to fill accumulator ACC with liquid to a pressure of 14MPa and then stop.

[0117] 2) Under normal circumstances, the filling time of the hydraulic pump PUMP for the accumulator ACC will not exceed 15 seconds. If the continuous filling time of the motor M pump group exceeds 30 seconds after starting, and the pressure detection value of the accumulator ACC is still ≤14MPa, the braking system will alarm, indicating that "the hydraulic system or brake oil circuit is abnormal" and the vehicle needs to be stopped for inspection.

[0118] 3) Check whether the working status of the first pressure sensor PU1 to the third pressure sensor PU3 is normal. A normal pressure signal is a switch quantity "1", and an abnormal pressure signal is a switch quantity "0". If the accumulator ACC pressure signal output is abnormal, the controller outputs a switch quantity "0". If any of the pressure sensors corresponding to the service brake cylinder is abnormal, the controller outputs a switch quantity "0".

[0119] Vehicle inspections while driving may include the following aspects:

[0120] 1) When there is a "service brake percentage command", the detection value of the service brake pressure sensor (second pressure sensor PU2 and / or third pressure sensor PU3) should be within the range of "10MPa × service brake percentage %" ± 1MPa. If the detection value of the service brake pressure sensor is outside the range of "10MPa × service brake percentage %" ± 1MPa, the vehicle's multi-condition hydraulic braking system will alarm, indicating "abnormal pressure increase in the service brake cylinder".

[0121] 2) If there is no “service brake percentage command or service percentage is 0”, the service brake pressure sensor value should be ≤0.1MPa. If the service brake pressure sensor value is >0.1MPa, the vehicle multi-condition hydraulic braking system will alarm, indicating “abnormal decompression of service brake cylinder”.

[0122] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-condition hydraulic braking system for vehicles, characterized in that, This includes the controller, hydraulic subsystem, oil control subsystem, and braking subsystem; The hydraulic subsystem includes a motor, a reservoir, a hydraulic pump, a relief valve, a check valve, an accumulator, a first pressure sensor, a first isolation valve, and a second isolation valve. The motor is electrically connected to the hydraulic pump and the controller; The inlet of the hydraulic pump and the outlet of the relief valve are connected to the reservoir, and the outlet of the hydraulic pump is connected to the inlet of the check valve and the inlet of the relief valve. The outlet of the one-way valve and the inlet of the first isolation valve are connected to the accumulator; the first pressure sensor is used to detect the pressure of the accumulator. The outlet of the first isolation valve is connected to the oil control subsystem and the inlet of the second isolation valve; The oil control subsystem is connected to the braking subsystem; The outlet of the second isolation valve is connected to the reservoir; wherein the second isolation valve is configured to be normally open, so that when the braking subsystem is not braking, the oil leaking from the outlet of the first isolation valve flows back to the reservoir through the second isolation valve; The oil control subsystem includes a first proportional valve, a second proportional valve, a first pressure relief valve, a second pressure relief valve, and a balance valve; the braking subsystem includes a first service brake cylinder and a second service brake cylinder. The outlet of the first proportional valve is connected to the inlet of the first pressure relief valve, the first opening of the balance valve, and the first service brake cylinder. The outlet of the second proportional valve is connected to the inlet of the second pressure relief valve, the second opening of the balance valve, and the second service brake cylinder; The outlets of the first pressure relief valve and the second pressure relief valve are connected to the liquid storage tank; The controller is configured to control the braking subsystem by controlling the operating states of the target valve and the motor according to different operating conditions; wherein the target valve includes at least one of the first isolation valve, the second isolation valve, the first proportional valve, the second proportional valve, the first pressure relief valve, the second pressure relief valve, and the balance valve; The operating conditions include accumulator replenishment, non-braking driving, straight road pressure boosting braking, straight road pressure decompression braking, long downhill braking, turning braking, continuous braking automatic decompression, pressure holding, and pressure holding followed by decompression; the turning braking condition includes turning pressure boosting braking and turning decompression braking.

2. The vehicle multi-condition hydraulic braking system according to claim 1, characterized in that, The operating condition described is the accumulator replenishment operating condition; When the pressure value detected by the first pressure sensor is less than the first preset pressure value, the motor starts, causing the motor to drive the hydraulic pump to replenish the accumulator until the pressure value detected by the first pressure sensor is greater than the second preset pressure value, at which point the motor stops running. Among them, the first isolation valve, the second isolation valve, the first proportional valve, the second proportional valve, the first pressure relief valve, the second pressure relief valve, and the balance valve are all de-energized.

3. The vehicle multi-condition hydraulic braking system according to claim 1, characterized in that, The operating condition described is the non-braking driving condition; When there is no driving brake percentage command, the first isolation valve, the second isolation valve, the first proportional valve, the second proportional valve, the first pressure relief valve, the second pressure relief valve, and the balance valve are all de-energized. The motor determines whether to work based on the pressure of the accumulator. The first proportional valve and the second proportional valve both output a first adjustment ratio signal that is less than a preset ratio, so that the pressure of the first driving brake cylinder and the pressure of the second driving brake cylinder are both less than or equal to a third preset pressure.

4. The vehicle multi-condition hydraulic braking system according to claim 1, characterized in that, The operating conditions described are boost braking on straight roads and depressurization braking on straight roads; Under the flat road condition boost braking condition, the first isolation valve is energized and turned on, the second isolation valve is energized and turned off, the first proportional valve and the second proportional valve output a second adjustment ratio signal, and the balance valve is not energized and remains turned on, so that the pressure of the first service brake cylinder and the pressure of the second service brake cylinder both meet the pressure corresponding to the second adjustment ratio signal. Under the pressure relief braking condition on a straight road, the first isolation valve is de-energized and closed, the second isolation valve is energized and closed, the first proportional valve and the second proportional valve output a third adjustment proportional signal, the balance valve is de-energized and remains conductive, and the first pressure relief valve and the second pressure relief valve are intermittently energized and conductive, so that the pressure of the first service brake cylinder and the pressure of the second service brake cylinder both meet the pressure corresponding to the third adjustment proportional signal; wherein, the pressure corresponding to the third adjustment proportional signal is less than the pressure corresponding to the second adjustment proportional signal.

5. The vehicle multi-condition hydraulic braking system according to claim 1, characterized in that, The operating condition described is a long downhill braking condition; When it is detected that the duration of the vehicle's boost braking is greater than the first preset duration, and the change in the pedal position is less than the preset change value, the first proportional valve and the second proportional valve are adjusted to the set control current, the first isolation valve is de-energized and closed, the second isolation valve is energized and closed, and the first pressure relief valve and the second pressure relief valve are de-energized and remain closed. When the detected change in the pedal position exceeds the preset change value, the long downhill braking condition is released, and the operating condition is switched according to the change in the pedal position.

6. The vehicle multi-condition hydraulic braking system according to claim 1, characterized in that, The operating condition is a turning braking condition, which includes a turning boost braking condition and a turning depressurization braking condition. Under the aforementioned turning braking condition, the pressure of the inner service brake cylinder and the pressure of the outer service brake cylinder are distributed according to the turning direction, such that the pressure of the outer service brake cylinder is greater than that of the inner service brake cylinder; wherein, when the turning direction is left turn, the first service brake cylinder is the inner service brake cylinder and the second service brake cylinder is the outer service brake cylinder; when the turning direction is right turn, the first service brake cylinder is the outer service brake cylinder and the second service brake cylinder is the inner service brake cylinder; In the case of turning and boosting braking, the first isolation valve is energized and open, the second isolation valve is energized and closed, the first pressure relief valve and the second pressure relief valve are not energized and remain closed, the balance valve is energized and closed, the first proportional valve outputs a fourth proportional adjustment signal, and the second proportional valve and the first proportional valve output a fifth proportional adjustment signal, so that the pressure of the first service brake cylinder is different from the pressure of the second service brake cylinder. During cornering and decompression braking, the first isolation valve is de-energized and closed, the second isolation valve is energized and closed, the balance valve is energized and closed, the first proportional valve outputs a sixth proportional adjustment signal, and the second proportional valve outputs a seventh proportional adjustment signal, causing the pressure of the first service brake cylinder to be different from the pressure of the second service brake cylinder. The first pressure relief valve and the second pressure relief valve are intermittently energized and connected, so that the pressure of the first service brake cylinder meets the pressure corresponding to the sixth proportional adjustment signal, and the pressure of the second service brake cylinder meets the pressure corresponding to the seventh proportional adjustment signal.

7. The vehicle multi-condition hydraulic braking system according to claim 1, characterized in that, It also includes a second pressure sensor and a third pressure sensor; The second pressure sensor is used to detect the pressure of the first service brake cylinder, and the third pressure sensor is used to detect the pressure of the second service brake cylinder; The operating condition described is the continuous braking automatic pressure reduction operating condition; If the pressure of the first service brake cylinder is greater than the required pressure of the first service brake cylinder, and / or the pressure of the second service brake cylinder is greater than the required pressure of the second service brake cylinder, automatic pressure reduction shall be performed; Specifically, the first isolation valve is de-energized and closed, the second isolation valve is energized and closed, the first pressure relief valve and the second pressure relief valve are intermittently energized and connected, and the balance valve maintains the state before automatic pressure reduction.

8. The vehicle multi-condition hydraulic braking system according to claim 7, characterized in that, The operating condition described is a pressure-holding condition; Under the pressure-holding condition, if the pressure of the first service brake cylinder is greater than the fourth preset pressure but less than the required pressure of the first service brake cylinder, the first isolation valve is energized and opened, the second isolation valve is energized and closed, the balance valve is energized and closed, the first proportional valve is energized and closed, and the second proportional valve remains in its original state to maintain the pressure of the first service brake cylinder; if the pressure of the second service brake cylinder is greater than the fourth preset pressure but less than the required pressure of the second service brake cylinder, the first isolation valve is energized and opened, the second isolation valve is energized and closed, the balance valve is energized and closed, the second proportional valve remains in its original state to maintain the pressure of the second service brake cylinder.

9. The vehicle multi-condition hydraulic braking system according to claim 8, characterized in that, The operating condition described is the pressure reduction condition after pressure holding; Under the pressure-holding and pressure-reducing condition, if after the first service brake cylinder has entered the pressure-holding condition for a second preset time, the pressure of the first service brake cylinder is greater than the fifth preset pressure and less than the fourth preset pressure, the first isolation valve is energized and opened, the second isolation valve is energized and closed, the balance valve is energized and closed, the first proportional valve is energized and closed, the second proportional valve remains in its original state, and the first pressure relief valve is intermittently energized and opened to relieve pressure on the first service brake cylinder; if after the first service brake cylinder has entered the pressure-holding condition for a second preset time, the pressure of the second service brake cylinder is greater than the fifth preset pressure and less than the fourth preset pressure, the first isolation valve is energized and opened, the second isolation valve is energized and closed, the balance valve is energized and closed, the second proportional valve is energized and closed, the first proportional valve remains in its original state, and the second pressure relief valve is intermittently energized and opened to relieve pressure on the second service brake cylinder.

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