JPS6240213B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tandem master cylinder device that is integrally equipped with a hydraulic pressure control valve for preventing rear wheels from locking during braking of a vehicle.

[Prior Art] As is well known, when a vehicle brakes, a load is transferred to the front, and when the frictional engagement force of the rear wheels with the road surface becomes extremely small, the rear wheels lock, losing lateral stability, and causing the rear of the vehicle to shift. There is a problem that the machine swings sideways and causes a turn. In order to prevent such wheel locking, it is necessary to appropriately distribute the braking force between the front wheels and the rear wheels. Ideally, as the braking force increases, the front wheel brakes will be more effective than the rear wheel brakes. Figure 1 shows a curve 70 in which the relationship between the front wheel brake fluid pressure P _F and the rear wheel brake fluid pressure P _R takes the load as a parameter. , 71 is desirable.

Conventionally, as a tandem master cylinder device that satisfies such requirements, there is one disclosed in, for example, Japanese Unexamined Patent Publication No. 130975/1983. In this prior art, a floating piston slides inside a stepped cylinder of a cylinder housing in order to reduce the hydraulic pressure of the rear wheel brake. Therefore, it is no longer possible to use common parts of the conventional master cylinder device, and accurate concentricity is required for machining the stepped cylinder with respect to the cylinder body, resulting in increased costs.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, an object of the present invention is to provide a system in which a hydraulic control valve can be integrated into a cylinder body having a single inner diameter, which is advantageous in cost reduction due to common parts. An object of the present invention is to provide a tandem master cylinder device.

[Means for Solving the Problems] In order to achieve the above object, the structure of the present invention is such that a floating piston is fitted into a cylinder body and partitions first and second liquid chambers, and inside the floating piston, both ends have a small diameter. a stepped cylindrical portion that communicates with the first and second fluid chambers, has a large diameter in the center, and has a cylindrical portion on the first fluid chamber side that communicates with the rear wheel brake; A stepped piston having a small diameter at both ends and a large diameter at the center and biased toward the first liquid chamber by a spring is fitted into the second liquid chamber, and the second stepped piston is provided inside the stepped piston.
A control valve supported by a floating piston is protruded into a passage communicating the liquid chamber with the cylindrical portion, and the passage is narrowed by movement of the stepped piston against the spring.

[Function] The stepped piston 12 has a different area that receives the hydraulic pressure of the second liquid chamber 57 and an area that receives the hydraulic pressure of the rear wheel brake. A passage 60 communicating with the wheel brake is provided,
When the liquid pressure in the second liquid chamber 57 exceeds a predetermined value, the stepped piston 12 resists the force of the spring 10 against the control valve 15 supported by the floating piston 43 and protruding into the passage 60. A relative movement occurs, constricting the passage 60 and reducing hydraulic pressure to the rear brakes.

[Embodiments of the Invention] As shown in FIG. 2, the tandem master cylinder device according to the present invention includes a liquid tank 55, a cylinder body 32, and a driving piston 50 actuated by pedal force.
, a floating piston 43, and a control valve 15 configured inside the floating piston 43. The liquid tank 55 is provided with pipes 22 and 26 that protrude from the bottom and supply working liquid to a pair of liquid chambers in the cylinder body 32.

One end of the cylinder body 32 is closed by an end wall 42, and the open end is fixed to the vehicle body by inserting bolts into a plurality of holes 34 provided in a flange 35.
A floating piston 43 and a driving piston 50 are fitted into a cylinder with a single inner diameter formed inside the cylinder body 32, and a return spring 41 is inserted between the end wall 42 and the floating piston 43, and the floating piston 43 and the driving piston 50 A return spring 38 is interposed between them, and the drive piston 50 is stopped by a retaining ring 36 that is engaged with the open end of the cylinder body 32. The spring seat 47 is made of a conical cylindrical body, and its closed end is slidably fitted over the rod 48 so as not to come off, and its open end is used to return the radially outwardly extending flange to the floating piston 43 by the spring 38. It abuts against the right end surface.

A liquid chamber C is formed on the upper peripheral wall of the main body 32, and is partitioned into a liquid chamber 57 and a liquid chamber 58 by the floating piston 43, and normally communicates with the liquid chamber 57 via the passage 23.
The pipe 22 of the liquid tank 55 described above is firmly connected to this liquid chamber C via an elastic seal ring 24. Similarly, the liquid chamber D that normally communicates with the liquid chamber 58 is connected to the cylinder body 3.
2, and a pipe 26 of a liquid tank is connected to this liquid chamber D via an elastic seal ring 29.

Inside the cylindrical liquid chamber D, two parts having different inner diameters are formed, and a sleeve 28 having a passage 30 and connecting a valve seat 31 made of an elastic material to the lower end is fitted. It is held by a retaining ring 27. A valve body 52 that is brought into contact with the valve seat 31 by the force of a spring 53 is housed inside the liquid chamber D. The leg 52a of the valve body 52 projects into the interior of the cylinder body 32 and is normally tilted by the spring seat 47 to open the passage 30. An air vent plug 21 is provided at the closed end of the cylinder body 32 to expel internal air.

The drive piston 50 is provided with a recess 49 at this end for engaging a rod that receives depression force from a brake pedal (not shown), and a return spring 38.
It is equipped with a rod 48 for regulating the Seal rings 33 and 37 are fitted around the outer periphery of the drive piston 50 to ensure fluid tightness of the sliding portion with the cylinder body 32.

The floating piston 43 has a seal ring 6 in the center part.
3, a pair of seal rings 18 and 19 are fitted to the right end, and a cup-shaped seal ring 67 is fitted to the left end, which is smaller than the inner diameter of the liquid chamber 57, along with a weak leaf spring 56 that abuts against the back surface of the cup-shaped seal ring 67. mated,
It is held by a spring seat 39 so that it does not come off. A pair of wide annular grooves 6 on the outer periphery of the floating piston 43
1 and 65 are provided, and the annular groove 61 constantly communicates with the liquid chamber C via the passage 25 and communicates with the gap existing on the back surface of the seal ring 67 via the passage 68.

According to the present invention, a stepped cylindrical portion is formed inside the floating piston 43, with a large diameter at the center and small diameters at both ends. That is, the small diameter cylindrical portion 51 on the left side of the large diameter cylindrical portion 59 is communicated with the liquid chamber 57 via the passage 40 . Further, a stopper 44 equipped with a seal ring is fitted to the right side of the large-diameter cylindrical portion 59 and fixed by a retaining ring 46 . This stopper 44 has a small diameter cylindrical portion 5.
4 is formed and communicates with the liquid chamber 58 via a passage 45. The inner diameters of the small-diameter cylindrical parts 51 and 54 are the same, or preferably, the small-diameter cylindrical part 51 has a slightly larger diameter than the small-diameter cylindrical part 54.

Small diameter portion 12 that fits into small diameter cylindrical portions 51 and 54
The stepped piston 12 has a large diameter portion that fits into the large diameter cylindrical portion 59 and partitions the large diameter cylindrical portion 59 into a liquid chamber A and a liquid chamber B. The small diameter portion 12a of the stepped piston 12 is urged into engagement with the end wall of the small diameter cylindrical portion 54 by the spring 10 housed in the liquid chamber A at atmospheric pressure. The liquid chamber A communicates with the annular groove 61 through a passage 69, and the liquid chamber B communicates with the annular groove 65 through a passage 64. Seal rings are attached to the large diameter portion and small diameter portions 12b, 12a of the stepped piston 12, respectively.

The stepped piston 12 includes a passage 60 extending in the axial direction from the left end, and the right end forms a valve hole and communicates with a radial guide groove 66.
The control valve 15 having a projecting piece inserted into the guide groove 66 is moved by the force of the spring 62 housed in the passage 60 to the right end wall of the large diameter cylindrical portion 59, that is, the stopper 44.
The floating piston 43 does not move relative to the floating piston 43.

The cylinder body 32 is provided with an outlet passage 20 that communicates the liquid chamber 58 with the front brake, and an outlet passage 14 that communicates the liquid chamber B of the floating piston 43 or the liquid chamber formed by the annular groove 65 with the rear brake.

Next, the operation of the device of the present invention will be explained. When the drive piston 50 is pushed to the left in FIG. 2 during braking, the floating piston 43 also moves to the left while its position is regulated by the return springs 41 and 38. When the spring seat 47 separates from the leg 52a of the valve body 52, the valve body 52 is brought into an upright position by the force of the coil spring 53, and the passage 30 is closed. Therefore, the liquid chamber 58 is cut off from the liquid tank 55, and as the drive piston 50 moves leftward, the liquid in the liquid chamber 58 is forced to be sent from the passage 20 to the front wheel brake.

At the same time, as the floating piston 43 moves leftward, the seal ring 67 passes through the passage 23 while being spread outward in a radially outward manner.
The liquid enters the small diameter cylindrical portion 51 through the passage 40.
Further, it enters the liquid chamber B from the guide groove 66 via the passage 60, and further passes through the passage 64, the annular groove 65, and the outlet passage 14.
It is then sent under pressure to the rear brakes.

To simplify the explanation, the small diameter portions 12a and 12b
The cross-sectional areas of are assumed to be equal. floating piston 43
The control valve 15 integrated with the stepped piston 12 normally opens the passage 60, but as the liquid pressure in the liquid chamber 57 gradually increases, When the hydraulic pressure acting on the area (area obtained by subtracting the cross-sectional area of ) becomes larger than the load of the spring 10 (hydraulic pressure Pc in FIG. 4), the stepped piston 12 moves toward the second liquid chamber 57, and the control valve passage 60 by 15
is throttled and the fluid pressure to the rear brakes is reduced.

When the brake action is released, the force of the return spring 41 returns the floating piston 43 to the right, and the force of the return spring 38 returns the drive piston 50 to the position shown in FIG. Therefore, the hydraulic pressure of the rear wheel brake is transferred from the outlet passage 14 to the annular groove 65 to the passage 6.
4. The liquid is released through the liquid chamber B, the guide groove 66, the passage 60, the small diameter cylindrical portion 51, and the passage 40 to the liquid chamber 57 whose volume is increasing due to the rightward movement of the floating piston 43. Then, the stepped piston 12 is pushed to the right by the force of the spring 10, and the small diameter portion 12a is pushed into the small diameter cylindrical portion 5.
4, and the opening degree of the passage 60 is maximized. Further, the hydraulic pressure of the front wheel brake is released from the outlet passage 20 to the liquid chamber 58 whose volume is increasing. When the spring seat 47 returns to the state shown in FIG. 2, it hits the leg 52a of the valve body 52, tilts the valve body 52 against the force of the spring 53, and opens the passage 30.

[Effects of the Invention] As described above, the present invention has a floating piston that is fitted into the cylinder body and partitions the first and second liquid chambers, the first and second liquid chambers each having a small diameter at both ends. A stepped cylindrical part is provided that communicates with the fluid chamber and has a large diameter in the center and a cylindrical part on the first fluid chamber side that communicates with the rear wheel brake, while the stepped cylindrical part has small diameters on both ends and a large diameter in the center. a stepped piston having a diameter and biased by a spring toward a first liquid chamber side, and connecting the second liquid chamber provided inside the stepped piston to a passage communicating with the cylindrical portion; Since the control valve supported by the floating piston is protruded and the passage is narrowed by the movement of the stepped piston against the spring, when the operating force applied to the drive piston during brake application exceeds a certain value, the stepped piston is closed. The attached piston moves relative to the control valve, and the passage is narrowed by the control valve.
The hydraulic pressure applied from the second liquid chamber to the rear wheel brake is lower than the hydraulic pressure applied from the first liquid chamber to the front wheel brake, and locking of the rear wheel is suppressed.

In addition, by communicating the small diameter cylindrical portion adjacent to the first liquid chamber side of the stepped cylindrical portion with the first liquid chamber,
When a pressure loss occurs in the front brake system, the stepped piston is pressed toward the first fluid chamber, and the pressure fluid in the second fluid chamber is sent to the rear brake without being depressurized. Delivers maximum braking power.

Since the present invention incorporates a control valve inside the floating piston, it can be applied to a general master cylinder device without changing the dimensions, and the control valve directly controls the hydraulic pressure in the first and second liquid chambers. It is designed so that it can be operated reliably. Further, since the cylinder body 32 has a single inner diameter, the inner diameter of the cylinder body can be easily machined compared to the conventional example having a stepped cylinder, which is advantageous for cost reduction.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the ideal distribution of braking force applied to the front wheels and rear wheels, FIG. 2 is a longitudinal sectional view of the tandem master cylinder device according to the present invention, and FIG.
The figure is a sectional view of a main part of the device, and FIG. 4 is a diagram illustrating the operation of the device. 10: Spring, 12: Stepped piston, 12a, 1
2b: Small diameter part, 14, 20: Outlet passage, 15: Control valve, 32: Cylinder body, 43: Floating piston, 50: Drive piston, 51, 54: Small diameter cylindrical part, 55: Liquid tank, 57: Second Liquid chamber, 58: 1st
liquid chamber, 59: large diameter cylindrical part;

Claims (1)

[Claims] 1 Inside the floating piston that is fitted into the cylinder body and partitions the first and second liquid chambers, there is a piston that has a small diameter at both ends, communicates with the first and second liquid chambers, and has a large diameter at the center. The cylindrical portion on the first fluid chamber side is provided with a stepped cylindrical portion that communicates with the rear wheel brake, and the stepped cylindrical portion has a small diameter at both ends and a large diameter at the center, and has a spring connected to the first fluid chamber side. into a passageway into which a stepped piston is fitted, which is biased by the stepped piston, and communicates the second liquid chamber provided inside the stepped piston with the cylindrical portion;
A tandem master cylinder device characterized in that a control valve supported by a floating piston is protruded, and the passage is narrowed by movement of the stepped piston against the spring.