JPH0215421B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brake hydraulic pressure control device for a vehicle, and more particularly to a brake hydraulic pressure control device that supplies a hydraulic pressure lower than that of the front wheels as the brake hydraulic pressure of the rear wheels. It is.

Conventionally, in automobile braking systems, during braking, the increase in rear wheel brake hydraulic pressure is suppressed in response to a decrease in the rear wheel load due to forward movement of the vehicle load.
In order to prevent the rear wheels from locking up and obtain efficient braking, the oil path connecting the master cylinder and the rear wheel brakes detects the braking effect of the vehicle that exceeds a predetermined value, that is, the deceleration that exceeds a predetermined value. When this happens, a brake hydraulic pressure control device is known that reduces the output hydraulic pressure of the master cylinder and transmits the reduced pressure to the rear wheel brakes. This control device has a differential piston that receives hydraulic pressure on the master cylinder side and rear wheel brake side from both sides, and a weight valve body that communicates or cuts off the master cylinder side and the rear wheel brake side. When the deceleration of the vehicle reaches a predetermined value or more, the weight valve body cuts off between the master cylinder and the hydraulically operated part of the rear wheel brake, and the differential piston is moved by the hydraulic pressure from the master cylinder. Braking hydraulic pressure is applied to the rear wheel brake at a fixed ratio. In this way, the ratio of the braking force between the front wheels and the rear wheels changes in a straight line that bends at the time of activation of the weight valve body, and the ratio is approximated to the ideal braking force curve that represents the ideal change in the ratio. characteristics can be obtained.

By the way, depending on the type of vehicle, or in other words, depending on the load distribution between the front and rear wheels of the vehicle, this ideal braking force curve may vary depending on the type of vehicle, in other words, depending on the load distribution between the front and rear wheels of the vehicle, when the driver is the only person on board, and when the vehicle is loaded with a specified number of people or cargo. It changes depending on the constant volume. That is, since the rear wheels are more likely to lock up when there is only one person than when there is a constant load, the ratio of braking pressure between the front and rear wheels must be increased. Therefore, in such vehicle types, it is desirable that the characteristics of the brake hydraulic control device be changed between when one person is operating and when the vehicle is carrying a constant load.

The present invention has been made in view of the above-mentioned points, and its object is to provide a brake hydraulic control system for a vehicle whose characteristics automatically change between when one person is in the vehicle and when the load is constant.

Another object of the present invention is to create a pressure constant section in which the movement of the differential piston is stopped and the braking oil pressure of the rear wheels is kept constant when the output oil pressure of the master cylinder at constant volume reaches a predetermined value. An object of the present invention is to provide a braking hydraulic control device for a vehicle which further prevents the locking phenomenon of the rear wheels.

Still another object of the present invention is to provide a brake hydraulic control system for a vehicle that is capable of reliably braking the rear wheels even if the weight valve body malfunctions.

In order to achieve the above object, the present invention provides a housing that is installed in an oil passage that supplies the output hydraulic pressure of a master cylinder to a hydraulic actuating part of a rear wheel brake; They are fitted to define an input hydraulic chamber that communicates with the master cylinder and an output hydraulic chamber that communicates with the hydraulic actuation section of the rear wheel brake, and the pressure receiving area of the output hydraulic chamber side is equal to that of the input hydraulic chamber side. a differential piston set to be larger than the pressure regulating spring; a pressure regulating spring that urges the differential piston toward the output hydraulic chamber; and a pressure regulating spring that opens at the end face of the differential piston on the output hydraulic chamber side, and a pressure regulating spring that urges the differential piston toward the output hydraulic chamber; a valve body housed in a communication passage formed in the differential piston so as to communicate with the differential piston, and normally biased by a spring so as to abut against the inner end wall of the cylinder hole on the output hydraulic chamber side; a valve chamber that is provided and connected to a valve hole that bypasses the communication passage and communicates between the input and output hydraulic chambers; is accommodated in the valve chamber and moves by its inertia when the deceleration of the vehicle exceeds a predetermined value; and a weighted valve body that closes the valve hole when the differential piston moves by a predetermined amount or more toward the input hydraulic pressure chamber as the output hydraulic pressure increases. A valve seat is provided that contacts the body and closes the communication passage, and the pressure regulating spring maintains the output oil pressure at a predetermined value when the valve hole is closed and the valve body is in contact with the inner end wall. The output hydraulic pressure is proportionally reduced by cooperation with the differential piston and the valve body when the hydraulic pressure exceeds the hydraulic pressure of the rear wheel brake, and the output hydraulic pressure is transmitted to the hydraulic operating section of the rear wheel brake.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In FIG. 1, output ports P ₁ and P ₂ of a tandem type master cylinder 2 operated by a brake pedal 1 have oil passages L ₁ and L ₂ , respectively. is connected, and the output hydraulic pressure of the master cylinder 2 is supplied to each hydraulic operating part of the front wheel brake Bf and the rear wheel brake Br. A housing 3 of a brake hydraulic control device C is interposed in the oil passage _L2 . The housing 3 is fixed to the vehicle body at a predetermined angle of inclination θ upward and forward with respect to the direction of travel of the vehicle.

A cylinder hole 6 having a small diameter hole 4 and a large diameter hole 5 is formed in the housing 3, and the rear end (the right end in the figure) of the cylinder hole 6 is closed by an end plug 7. This end plug 7
A small diameter cylinder hole 8 smaller in diameter than the small diameter hole 4 of the cylinder hole 6 is formed in the small diameter cylinder hole 8 and the small diameter hole 4 of the cylinder hole 6.
Small diameter part 10 and large diameter part 1 of stepped differential piston 9
1 are sliding against each other. Thus, the large diameter portion 5 of the cylinder hole 6 and the small diameter portion 1 of the differential piston 9
0, an input hydraulic chamber 12 is defined, and an output hydraulic chamber 13 is defined between the small diameter hole 4 of the cylinder hole 6 and the front end surface (left end surface in the figure) of the differential piston 9. will be accomplished. These input hydraulic chamber 12 and output hydraulic chamber 13 are connected to the master cylinder 2 through an input port 14 connected to the upstream side of the oil path L ₂ and an output port 15 connected to the downstream side of the oil path L ₂ , respectively.
and is constantly connected to the hydraulic operating part of the rear wheel brake Br. Further, an atmospheric chamber 1 is provided in the small diameter cylinder hole 8 of the end plug 7 by the rear end surface of the differential piston 9.
6 is defined. This atmospheric chamber 16 communicates with the atmosphere through a ventilation hole 17 formed in the end wall of the end plug 7 and a dust seal 19 attached to the back surface of the end plug 7 by a retaining ring 18.

A cylindrical cavity 20 is formed inside the large diameter portion 11 of the differential piston 9, and a valve head 22 of a valve body 21 is accommodated within this cavity 20. The front end surface of the space 20 is closed off by an end piston 23 fixed to the front end of the differential piston 9 and a valve body 21 passing through the end piston 23. This void 20 is formed by a through hole 24 provided in the differential piston 9 and a through hole 2 provided in the end piston 23.
5 communicates with the input hydraulic chamber 12 and the output hydraulic chamber 13, respectively, and the input hydraulic chamber 12 and the output hydraulic chamber 13 communicate with each other through the space 20 and through holes 24 and 25. communication path p that can
is formed. A valve seat 26 is formed at the rear end of the end piston 23, and a valve body 2 is mounted on this valve seat 26.
When the valve head 22 of No. 1 comes into contact, the input hydraulic pressure chamber 12
The flow of hydraulic oil between the output hydraulic chamber 13 and the output hydraulic chamber 13 is cut off.

A valve spring 27 is provided in the space 20 to constantly bias the valve body 21 in a direction to bring it into contact with the end wall W of the cylinder hole 6.
has been reduced. Further, a spring 28 serving as a pressure regulating spring that presses the differential piston 9 forward, that is, in the direction of the output hydraulic chamber 13 with a constant spring force, is housed in the input hydraulic chamber 12 . Therefore,
Usually, the end piston 2 at the front end of the differential piston 9
3 and the front end surfaces of the valve body 21 are both in the illustrated position in contact with the end wall W of the cylinder hole 6, and the valve head 2
2 is away from the valve seat 26.

The housing 3 is also formed with a cylindrical valve chamber 29 having an axis extending in the longitudinal direction of the vehicle. The rear end (right end in the figure) of this valve chamber 29 is closed by a lid 30. A throttle hole 31 parallel to the axis of the valve chamber 29 is formed in the upper part of the lid body 30, and the throttle hole 31 and the housing 3
The valve chamber 29 communicates with the input hydraulic pressure chamber 12 through an inflow passage 32 provided in the valve chamber 29 . The housing 3 further includes a valve hole 33 that opens at the front surface of the valve chamber 29;
An outflow passage 34 communicating this valve hole 33 with the output hydraulic pressure chamber 13 is formed. An elastic valve seat 35 is provided around the valve hole 33 that opens into the valve chamber 29, and a spherical weighted valve body 3 accommodated in the valve chamber 29.
6 is seated on or removed from the valve seat 34, thereby controlling the opening and closing of the valve hole 33. Since the housing 3 is mounted facing forward and upward with respect to the traveling direction of the vehicle, the bottom surface of the valve chamber 29 is inclined, so that the weight valve body 36 is normally located at a lower position supported by the lid body 30. The valve hole 33 is open.

Next, the operation of the brake hydraulic pressure control system will be explained. When the vehicle is normally running, the differential piston 9 and the weight valve body 36 are in the position shown in FIG. 1. Therefore, when the master cylinder 2 is actuated by the brake pedal 1, one of the output ports P ₁
The pressure oil sent out from the front wheel brake Bf is supplied to the hydraulic operating section of the front wheel brake Bf through the oil path _L1 to operate it. At the same time, the other output port of master cylinder 2
Pressure oil sent out from P ₂ is introduced into the input port 14 of the brake hydraulic control device C via the oil path L ₂ , and flows from the input hydraulic chamber 12 to the through hole 24 , the cavity 20 , and the through hole 2 .
5 to the output hydraulic chamber 13 through the communication path p consisting of
Further, from the inflow passage 32, the throttle hole 31, and the valve chamber 29 to the output hydraulic chamber 13 via the valve hole 33 and the outflow passage 34,
It flows in from both, passes through the output port 15 and the downstream of the oil path _L2 , and is supplied to the hydraulic operating section of the rear wheel brake Br to operate it. Therefore, during this period, when the output oil pressure of the master cylinder 2, that is, the oil pressure in the input oil pressure chamber 12 of the braking oil pressure control device C increases, the braking oil pressure of the rear wheel brake Br, that is, the oil pressure in the output oil pressure chamber 13 also increases. will rise proportionately. During this time, the relationship between the input oil pressure of the control device C, that is, the oil pressure in the input oil pressure chamber 12, and the output oil pressure, that is, the oil pressure in the output oil pressure chamber 13, is as shown by the solid line _a1 in the characteristic diagram of FIG.

When the input oil pressure and the output oil pressure rise in the same manner as described above, due to the difference between the pressure receiving area on the input oil pressure chamber 12 side and the pressure receiving area on the output oil pressure chamber 13 side of the differential piston 9, the rearward pressure acting on the entire differential piston 9, That is, the pressing force toward the input hydraulic pressure chamber 12 becomes larger than the set load of the spring 28, causing the differential piston 9 to slide toward the input hydraulic chamber 12. And front and rear brakes
The vehicle decelerates due to the operation of Bf and Br, but when the driver is the only person on board, a large deceleration can be obtained while the braking oil pressure is relatively low, so the differential piston 9 moves back and the valve head Before the valve seat 26 is seated on the valve seat 22, the deceleration of the vehicle reaches a predetermined value.

In this way, when a predetermined deceleration occurs in the vehicle,
The weighted valve element 36 senses this and climbs up the slope of the bottom of the valve chamber 29 by its own inertia, seats on the valve seat 35, and closes the valve hole 33. However, the output hydraulic chamber 13 has a through hole 2 from the input hydraulic chamber 12.
4. Since pressure oil is supplied through the cavity 20 and the through hole 25, the hydraulic pressure in the output hydraulic chamber 13 is equal to that in the input hydraulic chamber 12 until the valve head 22 of the valve body 21 and the valve seat 26 come into contact. It still rises as the oil pressure increases.

The differential piston 9 retreats and the valve head 22 of the valve body 21
When it comes into contact with the valve seat 26, the flow of pressure oil from the input hydraulic chamber 12 to the output hydraulic chamber 13 is completely blocked. Therefore, an increase in the braking oil pressure of the rear wheel brake Br is suppressed. Thereafter, when the depression force on the brake pedal 1 is further increased to increase the output oil pressure of the master cylinder 2 and therefore the oil pressure in the input oil pressure chamber 12, the forward pressing force applied to the differential piston 9 increases. The differential piston 9 slides forward, and this sliding causes the hydraulic pressure in the output hydraulic chamber 13 to rise. At the same time, the gap between the valve head 22 and the valve seat 26 opens due to the sliding movement, and pressure oil flows from the input hydraulic chamber 12 into the output hydraulic chamber 13.
The oil pressure inside increases further. When this oil pressure reaches a value close to the oil pressure in the input oil pressure chamber 12, the differential piston 9 retreats again, and the communication path p between the input oil pressure chamber 12 and the output oil pressure chamber 13 is closed by the valve body 21.
An increase in the oil pressure within the output oil pressure chamber 13 is suppressed. By repeating such actions, the output oil pressure of the brake oil pressure control device C is maintained lower than the input oil pressure. The pressure reduction ratio at this time is the ratio of the effective areas obtained by subtracting the effective cross-sectional area of the valve body 21 from the respective pressure receiving areas of the input hydraulic chamber 12 side and the output hydraulic chamber 13 side of the differential piston 9. Therefore, the relationship with the input oil pressure at this time is as shown by the solid line _b1 on the characteristic curve in FIG.

In other words, the characteristic of this braking hydraulic control device C when one person is operating is a straight line that bends at a pressure point q ₁ that is slightly higher than the pressure at the activation point P ₁ of the weight valve body 36.
It is represented by a ₁ and b ₁ , and the ideal braking force curve in this case
The characteristics are similar to m ₁ .

When the vehicle is loaded with a predetermined number of people or cargo, the braking oil pressure becomes considerably high until the deceleration of the vehicle reaches a predetermined value. Therefore, in this case, when the master cylinder 2 is actuated by the brake pedal 1 and its output oil pressure is increased, the oil pressure in the input oil pressure chamber 12 and the oil pressure in the output oil pressure chamber 13 of the brake oil pressure control device C are The differential piston 9 is slid rearward, that is, toward the input hydraulic chamber 12, and the input hydraulic chamber 1 is opened by the valve body 21.
2 and the output hydraulic chamber 13 is closed. However, since pressure oil is supplied to the output hydraulic chamber 13 from the input hydraulic chamber 12 through the valve chamber 29, the hydraulic pressure in the output hydraulic chamber 13 continues to rise. Then, the differential piston 9 moves further rearward to separate the valve body 21 from the end wall W of the cylinder hole 6. At this time,
The valve body 21 is pressed by the valve spring 27 and input oil pressure, and is held in a state in which the valve head 22 is seated on the valve seat 26. During this period, the relationship between the input oil pressure and the output oil pressure of the brake oil pressure control device C is as shown by the solid line _a2 on the characteristic diagram in FIG.

When the braking oil pressure increases and a predetermined deceleration occurs in the vehicle, the weight valve body 36 moves due to inertia and closes the valve hole 33. In this way, the input hydraulic chamber 1
The flow of pressure oil from the output hydraulic pressure chamber 13 to the output hydraulic pressure chamber 13 is completely blocked, and an increase in the braking hydraulic pressure of the rear wheel brake Br is suppressed. When the hydraulic pressure in the input hydraulic pressure chamber 12 is further increased, the forward pressing force applied to the differential piston 9 increases, and the differential piston 9 moves forward. Due to this movement, the hydraulic pressure in the output hydraulic chamber 13 increases, but the pressure is reduced at a rate equal to the ratio of the pressure receiving area of the differential piston 9 on the input hydraulic chamber 12 side and the pressure receiving area on the output hydraulic chamber 13 side. Ru. Therefore, the decompression ratio in this case is closer to 1 than in the case of 1 person, and its characteristic diagram is larger than the solid line b ₁ in the case of 1 person, as shown by the solid line b ₂ in Figure 2. It becomes a straight line with a slope.

When the differential piston 9 slides forward as the oil pressure in the input hydraulic chamber 12 increases and the front end surface of the valve body 21 comes into contact with the end wall W of the cylinder hole 6, the pressure receiving area changes. , the backward force applied to the differential piston 9 by the hydraulic pressure in the output hydraulic chamber 13 becomes greater than the forward force applied by the hydraulic pressure in the input hydraulic chamber 12, and the forward movement of the differential piston 9 stops. be done. In this state, the pressure within the input hydraulic chamber 12 further increases, causing the differential piston 9 to move forward.
This continues until the valve seat 26 is separated from the valve head 22 of the valve body 21. That is, during this period, the output hydraulic pressure chamber 1
3, and therefore the braking oil pressure of the rear wheels, is held constant. This period is the pressure constant area indicated by the solid line z in FIG.

As described above, the characteristics of the braking hydraulic control device C in the case of constant volume are that the weight valve body 36 is bent at the actuation point _p2 , and the valve body 21 further advances so that its front end surface is in the cylinder hole 6. It is represented by straight lines a ₂ , b ₂ , and z that are bent at the point r ₂ that abuts the end wall W, and has a characteristic that approximates the ideal braking force curve m ₂ in this case.

If the weight valve body 36 malfunctions for some reason, for example, if the valve hole 33 is closed before the vehicle reaches a predetermined deceleration, the valve body 21 will close between the input hydraulic chamber 12 and the output hydraulic chamber 13. If it is before the communication passage p is closed, the rear wheel brake Br will be operated by the pressure oil flowing through it, and if it is after the valve body 21 has closed the communication passage p, the solid line b ₁ in the characteristic diagram for one person. It operates as follows to activate the rear wheel brake Br. Therefore, in either case, the rear wheel brake Br operates reliably.

In addition, in the above embodiment, the input hydraulic chamber 12
is formed between the large diameter hole 5 of the cylinder hole 6 and the differential piston 9, and a chamber 16 defined by the rear end surface of the differential piston 9 in the small diameter cylinder hole 8 of the end plug 7 is an atmospheric chamber. However, the position of this atmospheric chamber 16 is used as an input hydraulic chamber to guide the output hydraulic pressure from the master cylinder 2, and a through hole communicating from this input hydraulic chamber to the empty space 20 is provided to construct a braking hydraulic pressure control device similar to that described above. can also be configured.

As described above, according to the present invention, there is provided a housing interposed in the oil passage that supplies the output hydraulic pressure of the master cylinder to the hydraulic operating part of the rear wheel brake; and a housing that is slidably fitted into the cylinder hole in the housing; An input hydraulic chamber communicating with the master cylinder and an output hydraulic chamber communicating with the hydraulic operating section of the rear wheel brake are defined, and the pressure receiving area of the output hydraulic chamber side is set larger than that of the input hydraulic chamber side. a pressure regulating spring that urges the differential piston toward the output hydraulic chamber; and a pressure regulating spring that opens at the end face of the differential piston on the output hydraulic chamber side and communicates between the input and output hydraulic chambers. a valve body housed in a communication passage formed in the error moving piston and normally biased by a spring so as to abut against an inner end wall of the cylinder hole on the output hydraulic chamber side; A valve chamber connected to a valve hole that bypasses the passage and communicates between the input and output hydraulic chambers; is accommodated in this valve chamber, and moves by its inertia when the deceleration of the vehicle exceeds a predetermined value, and connects the valve hole to the valve hole. and a weighted valve body for closing the differential piston; the differential piston is configured to abut against the valve body when the differential piston moves toward the input hydraulic pressure chamber by a predetermined amount or more as the output oil pressure increases. A valve seat for closing the communication passage is provided, and the pressure regulating spring is activated when the output oil pressure exceeds a predetermined value with the valve hole closed and the valve body in contact with the inner end wall. It is constructed so that the output hydraulic pressure can be proportionally reduced by cooperation with the differential piston and the valve body and transmitted to the hydraulic operating section of the rear wheel brake.
When riding, the valve body is kept in contact with the inner end wall even when the valve hole is closed by the weight valve body, and when the volume is fixed, the valve body is moved to follow the differential piston from before the same time. It can be spaced apart from the inner end wall, and as a result, the ratio of the pressure receiving areas on the input hydraulic chamber side and the output hydraulic chamber side of the differential piston can be made different between when one person is on board and when the load is constant. Moreover, when one person is on board, the output hydraulic pressure of the master cylinder can be proportionally reduced and transmitted to the rear brake side by the cooperation of the pressure regulating spring, the differential piston, and the valve body in contact with the inner end wall. On the other hand, at the time of constant displacement, the output hydraulic pressure of the master cylinder is also proportionally reduced based on the ratio of the pressure receiving area, which is changed by substantially integrating the valve body into the differential piston. The information can be transmitted to the rear wheel brake side, and as a result, the pressure reduction ratio of the output hydraulic pressure of the master cylinder can be changed between when one person is riding and when the load is constant, and the braking force ideal curve in each state can be changed. Approximate ideal decompression characteristics can be provided. Moreover, only one differential piston is required to obtain these two types of pressure reduction characteristics, and the structure does not become particularly complicated, which contributes to cost reduction and improved assembly efficiency.

Also, when the output oil pressure of the master cylinder is increased during constant volume, when the differential piston moves forward and the valve body contacts the end wall of the cylinder hole, the rear wheel braking oil pressure remains constant for a certain period of time. This makes it possible to further prevent the rear wheels from locking up.

Furthermore, even if the weight valve body does not operate properly, the braking action of the rear wheels can be ensured by the operation of the differential piston and the valve body. It is possible to obtain a braking hydraulic control device for a vehicle that operates reliably.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the device of the present invention, and FIG. 2 is a graph showing the characteristics of the device. 2...Master cylinder, 3...Housing, 6
... Cylinder hole, 9 ... Differential piston, 12 ...
Input hydraulic chamber, 13... Output hydraulic chamber, 20... Blank space, 21... Valve body, 29... Valve chamber, 33... Valve hole, 36... Weight valve body, Br... Rear wheel brake,
C...Brake hydraulic control device, _L2 ...Oil passage.

Claims (1)

[Claims] 1 The output hydraulic pressure of master cylinder 2 is applied to the rear wheel brake.
A housing 3 is interposed in an oil passage L ₂ that supplies oil to a hydraulically operated part of the Br; and a housing 3 is slidably fitted into a cylinder hole 6 in this housing 3 and is connected to the master cylinder 2.
an input hydraulic chamber 12 communicating with the rear wheel brake;
The differential piston 9 defines an output hydraulic chamber 13 that communicates with the hydraulic operating section of the Br, and the pressure receiving area on the output hydraulic chamber 13 side is set larger than that on the input hydraulic chamber 12 side; a pressure regulating spring 28 that urges the dynamic piston 9 toward the output hydraulic chamber 13 side; and a pressure regulating spring 28 that opens at the end surface of the differential piston 9 on the output hydraulic chamber 13 side and connects the input and output hydraulic chambers 12 and 13 to communicate with each other. Communication path p formed in differential piston 9
A spring 27 is housed in the cylinder hole 6 and normally comes into contact with the inner end wall W of the cylinder hole 6 on the output hydraulic chamber 13 side.
an energized valve body 21; a valve chamber 29 provided in the housing 3 and connected to a valve hole 33 that bypasses the communication path p and communicates between the input and output hydraulic chambers 12 and 13; The differential piston 9 includes at least a weight valve body 36 which is housed in the chamber 29 and moves by its inertia force to close the valve hole 33 when the deceleration of the vehicle exceeds a predetermined value. When the differential piston 9 moves toward the input hydraulic pressure chamber 12 by a predetermined amount or more as the output oil pressure increases, the valve body 2
A valve seat 26 is provided which contacts the valve hole 33 and closes the communication path p, and the pressure regulating spring 28 is arranged such that the valve hole 33 is closed and the valve body 21 is in contact with the inner end wall W. When the output oil pressure exceeds a predetermined value, the output oil pressure is proportionally reduced by cooperation with the differential piston 9 and the valve body 21, and is transmitted to the hydraulic pressure operating part side of the rear wheel brake Br. A brake hydraulic control device for a vehicle, characterized by: