KR810000831B1 - Improvements in master cylinders for vehicle braking systems - Google Patents

Abstract

The tandem master brake cylinder has the primary and secondary pistons(1,2) of different diameters, with the primary piston larger in cross sectional area. The two pistons are held apart by a spring(12) which ensures that in the released position sufficient fluid is provided between the pistons to overcome any brake play. The larger dia. of the pirmary piston ensures that not only its circuit is provided with higher pressures but that in the event of primary circuit failure the amount of travel required before reaching the secondary piston is minimal.

Description

Tandem master cylinder

1 is a side view of a master cylinder according to the invention with the top in cross section and with the main and sub pistons in their retracted positions.

2 is an enlarged cross-sectional view of the rear end of the cage assembly of FIG.

FIG. 3 is a view similar to FIG. 2 with a valve head located rearward to the rear spring retainer of the cage assembly and showing the state of the spring wash fully inflated.

4 is an enlarged partial cross-sectional view of the front assembly of the cage assembly modified to attach the screw groove to the fine plug.

5 is a partial cross-sectional view of the front assembly of the cage assembly modified to attach to one piston.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem master cylinder for use in a hydraulic brake device of a vehicle, and more particularly to a tandem master cylinder having a cylinder housing having a hole in which the front end is closed. The movement is formed between the pistons in the main pressurizing zone and the additional pressure zone is formed between the sub piston and the closed end of the hole, and the sub piston is a port exposed to the sub pressurizing zone and It has a recuperation path that provides a permanent connection between the tank and the storage tank connection in the housing, which is connected to the oil storage tank. The recovery valve member controls the flow of fluid through the pot, The pot is sealed as it moves forward from the retracted position.

Two separate seals forming an annular chamber connected to the storage tank connection are provided to the volume stone in the master cylinder and it is necessary to provide a recovery passage within the volume stone. Conventionally, the main pressurizing zone and the additional pressurizing zone of the master cylinder have been used separately from each other by one annular seal operated by a volume stone. Such a device has a defect in which the defect of the seal cannot be easily found. If the seal fails, then one of the oil cycles will fail, so that the fluid flows through the broken seal on the bulk stone, causing the other oil cycle. Recently, many countries have forbidden the use of the single seals mentioned above for the above reasons. If two isolated seals are used on the bulk stone, a defect occurring in one of the two seals will not allow fluid to flow between the two pressurized zones, but only directly flow between one of the pressurized zones and the oil storage tank.

One of the conventional master cylinders of the above kind is that the recovery valve member is positioned by a caged spring relative to the closed end of the cylinder bore and the revolving position of the volume stone is a stopper and piston for the main piston. Is determined by the operation of the caged spring in between.

A serious drawback of the conventional apparatus described above is that the spacing between the recovery valve member and the pot is difficult when the tolerances in the size of the piston and the length of the cage assembly between the pistons are taken into account. If the gap between the recovery valve member and the pot is too large, the piston needs to move forward before the valve closes and the pressurization of the pressure zone begins. Thus, various tolerances will cause pistons in some mass-produced master cylinders to perform excessive stroke before pressurization begins.

According to the present invention, the valve adjusting assembly coupled with the valve member is located in the additional pressure region, and the valve control assembly includes a joining member engaged with the surface protruding to the front of the volume stone and is axially in the hole with respect to the valve member. The stopper is connected to the joining member, and the elastic device holds the valve member in front of the joining member against the stopper at the backward position of the volume stone, thereby positioning the valve member with respect to the joining member and thereby Determine the space between the pot and the valve member, and as the volume stone moves forward from the retracted position to the front, the force generated by the elastic device on the valve member is overcome so that the valve member moves backward with respect to the joining member. The device is arranged to close the haute. Thus, the space between the recovery valve member and the pot is substantially determined by the tolerance of the valve adjustment assembly and not by the sum of the other tolerances.

The reverse position of the volume stone in the hole is preferably determined by engagement with the joining member.

The secondary piston can be easily held forward to engage the joining member by a second elastic device in the form of a compression spring acting between the pistons.

Preferably, the second elastic device is operated backward with respect to the joining member, and with respect to the other members directly and indirectly engaged with the housing, and with the front member so that the valve member is attached to the other member to suppress the backward movement. do.

The first elastic device preferably includes a caged spring assembly comprising a caged spring between the two spring retainers and a rear spring retainer forming a joining member and a front spring retainer and spring forming another member. It is composed of a valve member carried by a head of the rear of the extending member extending in the axial direction with two heads to suppress the separation of the retainer.

The front part of the cage assembly, the front part of the cage, is fixed to the housing, or it is affected by the hydraulic pressure in the non-joined area and is fixed to the pressure reaction member having an effective area equal to or greater than the area of the valve member. It can prevent you from moving backward in the hole. In some cases, residual pressure may remain in the additional pressure zone when the volume stone approaches its normal reverse position. And if the cage assembly is not maintained in any way, the valve member can be permanently moved by pulling the cage backwards without being separated from the piston.

The invention will be explained in detail by the following figures and examples.

In the master cylinder of FIG. 1, the main piston 1 and the volume stone 2 can slide in the hole 3 in the cylinder housing 4, respectively. The main pressurizing zone and the additional pressurizing zone 5 and 6 are each connected to the angular oil circulation circuit passing through a port (not shown) in the wall of the housing.

The main pressurizing zone is an oil storage tank 8 separable by the tipping valve assembly 9, the annular chamber 10 and the radial port 11 in the main piston when the main piston is in the reverse position as shown. Is arranged to be connected to one thread (7). It is determined by engagement of the main piston with the lower end of the retracting tapping valve assembly.

The volume stone is isolated from the main piston by a compression spring 12 (second elastic device) and the spring 12 acts as a return spring with respect to the main piston, and at its rear end a cylindrical projection 13 is provided (12) is positioned so that it is accommodated in the hole (14) in the front part of the main piston (1). Thus, the stroke of the main piston is partly densely adjusted by the hole 14 and the device necessary for positioning the spring 12 is provided by the projection 13.

The protrusion 13 acts as a plunger that serves to vent airflow that is blocked inside the hole 14 or around the spring 12.

The bulky stone is provided with two axially isolated seals 15 and 16, between which an annular recess outside the bulky stone is connected to the storage tank 8 by means of a tubular connection member 19. ) And annular chamber 17 which can communicate freely. The connecting member 19 acts as a safety stop for the volume stone when excessive pressure is applied to the additional pressure chamber 6 at the time of brake rupture.

The recovery path of the volume stone is provided by axial and radial drilling 20 and 21 in the volume stone, which are located between the port 22 and the annular chamber 17 exposed to the pressure zone. Communicate.

The port 22 is a recovery valve member in the form of an annular seal 23 held in an annular groove 23 ′ in one head 29 of the rod 24 with two heads of the cage assembly 25. Controlled by a configured control valve assembly 36. The cage assembly 25 determines the cage length of the compression spring 26 (first elastic device) and consists of a rod 24 and two cup-shaped spring retainers 27 and 28, the retainer being a rod 24. It is capable of sliding from above and its maximum separation is determined by coupling with heads 29 and 30, respectively, on the opposite end of the rod.

The weak spring washer 31 (third elastic device) is sandwiched between the head 29 and the base 32 of the spring retainer 27 as shown in FIG. 3 and has a rod 30 and a seal ( 23) is pushed back against the spring retainer 27.

The spring retainer 28 is secured in the hole by a projection 28 'which is formed by a cylindrical nail 3 which engages with an outer annular groove in the boss 33. It is pressed against the inside of the outer recess of the tubular boss 33 attached in the closed end.

The compression spring 26 of the cage assembly 25 is stronger than the compression spring 25 acting between the pistons so that the cage assembly 25 constitutes the connecting member when the pedal force is removed by acting on the main piston. At the rear end of the hole 34 extending rearward in the piston 13 by the engagement of a spring retainer 27 having a surface 37 on the piston 13 to determine the backward position of the volume stone 13. To expand.

The axial position of the seal 23 relative to the spring retainer 27 is determined by the joining of the head 29 with the stop surface 38 over the spring retainer 27 as in FIG. 2. The axial thickness of the annular seal 23 is a surface that allows fluid to communicate between the radial seal surface of the seal 23 and the second chamber 6 and the port 22 with the cage assembly 25 fully inflated. It is chosen so that there can be a desired gap between (37). This clearance is determined only by the size of the spring retainer 27, the head 29, and the seal 23.

The bulky stone moves forward from the backward position in response to the forward movement of the main piston, and the rear spring retainer 27 also moves forward as the force in the spring 26 is overcome in the hole. The head 29 is no longer supported forward against the retainer 27 by the spring 26 and when the surface 37 is joined to seal the pot 22 of the bulky stone by the seal 23. Until under the control of the force of the spring 31 in the hole. As the volume stone continues to move forward, both the head 29 and the retainer 27 move forward together with the piston 2 in the bore.

Providing holes 34 in the volume stone allows a substantial portion of the length of the cage assembly 25 to be received within the length of the volume stone, thereby reducing the total length of the master cylinder. This length is further reduced by placing the spring 12 in the hole 14.

If an abnormality occurs in the seal 16 of the bulky stone, communication is established between the annular recess 17 connected to the storage compartment 18 and the main pressurization zone 5 and the addition of the main pressurization zone 5. Since there is no direct connection between the pressure zones 6, the oil circulation connected to the additional pressure zone will continue to operate.

Similarly, if an error occurs in the seal 15, only the communication between the additional pressure zone 6 and the annular chamber 17 prevents the main pressure zone 5 and the circulation connected to it.

If either seal 15 or 16 fails, it will be detected by a pressure change warning actuator connected between the two flow paths. In a normal cylinder equipped with a single seal on the volume stone to isolate the main and additional pressure zones, the seal failure will not be detected by the warning actuator.

The advantage of having a recuperation port for the additional pressure region located in the volume stone with the cage assembly 25 held at the closed end of the cylinder bore 3 recovers within the closed end of the cylinder bore. Compared with conventional arrangements equipped to attach to the bulk stone with the pot, the former requires the bulk stone to be machined with only plain holes, while the latter accommodates the fixed retainer of the valve member. And machining with cylindrical slots to hold.

In an embodiment the relative stroke of the piston can be adjusted simply by changing the length of the cage assembly 25. Jupitons are shown to be acted upon by scaffolding, but it will be appreciated that the master cylinder may be operated at fluid pressure.

In the variant structure of FIG. 4, the spring retainer 28 is secured to the sleeve 39 like a fine plug 33 'by a tag 28' (not shown). The sleeve 39 forms a conveying member of the spring retainer. The plug 33 'seals a hole 40 in the end wall of the cylinder housing which is large enough to allow the sleeve 39 and the cage assembly to which it is attached to form the housing from that end. . The plug 33 ′ is sealed to the housing by an annular seal 41.

In another variant of FIG. 5, the additional pressure acting on the piston 42 to which the spring retainer 28 is attached by a tag (not shown) is not mechanically attached in the cylinder housing. It is effectively held by the hydraulic pressure of the region 6. The piston 42 is sealed in the deformed distal end 43 of the cylinder bore 3 by an annular seal 44 which is cup-shaped and located in an annular groove formed in the outer surface of the piston. The vent 45 in the end wall of the cylinder housing communicates the airflow so that when the second pressurized zone 6 is pressurized, the pressure passing through the piston is different and the fluid leaks due to the abnormality of the seal 44. To show.

The cross-sectional area of the piston 42 is made larger than the cross-sectional area of the recovery seal (not shown) carried by the rear end of the rod 24. Thus, when retracting, when the volume stone approaches its normal retracted position, if the residual pressure remains in the additional pressure region, the force generated by the hydraulic pressure on the piston 42 is caught by the valve member from the position on the volume stone by the rod 24. It is sufficient to overcome the force generated by the hydraulic pressure on the recovery valve member so that it can be pulled.

Claims (1)

It consists of a cylinder housing in which the front end is sealed and the main piston and the volume stone operate, the main pressure zone defined between these pistons, and the additional pressure zone defined between the volume stone and the sealed end of the hole. There is a recovery passage for continuous communication between the pot and the storage tank connection path in the housing connected to the oil storage tank and the port exposed to the pressure zone, and the volume stone is advanced as it moves forward from the backward position. A master cylinder having a recovery valve member arranged to seal an haute and controlling fluid flow through the port; A valve steering assembly 36 cooperating with the valve member 23 is disposed in the additional pressure region 6, which is coupled by a forward facing surface 37 on the volume stone 2 to provide a hole ( 3) a joining member 27 capable of axially moving relative to the valve member, a stopper 38 associated with the joining member, and a valve against the stopper when the volume stone is in the reversed position. It has an elastic device 26 which holds the member forward relative to the joining member to position the valve member relative to the joining member and accordingly spaces the valve member from the pot 22. The force generated by this resilient device on the valve member is overcome as it moves forward to its backward position to cause the valve member to move backwards with respect to the joining member to seal the pot. A tandem master cylinder.

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