GB2059528A

GB2059528A - Modulating Valves for Anti-skid Systems

Info

Publication number: GB2059528A
Application number: GB8030129A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1979-09-21
Filing date: 1980-09-18
Publication date: 1981-04-23
Also published as: DE2938180A1; JPS5653946A; GB2059528B; JPS6313858B2

Abstract

A pressure-control brake valve unit for a vehicle brake anti-skid system has a plurality of main valves (14) which are respectively pilot- controlled by solenoid valves (11, 12, 13), the pilot valves and the main valves being disposed in a common housing (17) at the bottom of which is provided a common exhaust port (45) for the valves (11, 12, 13, 14). In the valve housing, the piston rod (74) of an actuating piston (75) of a main valve (14) is provided with guide ribs (76) located in a region of the valve (housing recess 46) which does not become soiled and which does not freeze up. The brake valve unit is an improvement on that described in British Patent application No. 17668/78 (Serial No. 1579301). <IMAGE>

Description

SPECIFICATION Anti-skid System The invention reiates to a vehicle brake antiskid system and more particularly to a pressurecontrol valve unit for an anti-skid system.

A known pressure-control valve unit has at least two main valves of which one is a three-port two-position valve, and respective solenoid pilot valves for actuating the main valves. In this known valve unit it is possible that the 3,2 main valve might not close in a reliable manner owing to the fact that its closure member is not guided with sufficient accuracy. Thus, leaks can occur which would impair the operation of the anti-skid system.

The invention consists in a pressure-control valve unit for an anti-skid brake system of a motor vehicle, comprising a common housing at least two pressure-controlled main valves and a respective solenoid pilot valve for each main valve, all the valves being disposed in the common housing which, in use of the valve unit, is so oriented that the solenoid pilot valves are disposed below the main valves and a common atmospheric air port provided for the valves is in the underside of the housing, an actuating piston of one main valve being provided with a piston rod which has guides for guidance in the housing and whose free end carries a deflectable valve closure member of that main valve.

This has the advantage that the satisfactory guidance of the closure member of the main valve ensures satisfactory operation of the anti-skid system. It is thereby ensured that the guide cannot be soiled and cannot freeze up. In accordance with preferred features of the invention, the valve closure member actuated by the piston rod can compensate for offset between the plane of the valve seat and the guide.

The invention is further described by way of example, with reference to the drawing which is a flow diagram of an anti-skid system, the anti-skid valve being shown in section.

An anti-skid system is incorporated in a brake system having a brake line 1, 1', 1" between a brake valve 2 and two wheel cylinders 3 and 4.

The anti-skid system comprises two sensors 5 and 6 on the wheels 7 and 8 of vehicle axle 9, and an electronic control device 10 to which the sensors 5 and 6 and three solenoid valves 11, 12 and 13 are connected, only two of which solenoid valves are visible in Figure 1, since the third valve is located behind the first valve.

The three solenoid valves 11, 12 and 13 are pilot valves and, together with three main valves 14, are combined in a common housing 17 to form a so-called pressure-control valve unit by which the brake line 1 is connected to the branch lines 1', 1". The pressure-control valve unit is an improvement on that described in published German Patent specification (Offenlegungschrift) No. 27 39 513. The housing 17 is essentially of two-part construction and has an upper portion 1 8 and a lower portion 1 9 which are clamped together by a bolted connection comprising bolts 20.

The three pilot valves 11, 12, 13 have solenoid housings 21,22 and 23 each having a mounting surface by means of which the housings abut against an underface 24 of the upper portion 18 where they are secured by the said bolted connection of the housing portions 18 and 19. A respective stem 25,26 or 27 of the respective solenoid pilot valve 11, 12 or 13 passes through each mounting surface, and the top end of each stem is provided with a respective closure member 28, 29 or 30 for a respective valve seat 31,32 or 33.

Each closure member controls communication between a branch passage 34, 35 or 36 to the respective valve seat 31, 32 or 33 and a passage 40 leading to a working chamber 37 of the respective main valve 14 and between the respective passage 40 and a respective further valve seat which leads via the respective solenoid housing 25, 26 or 27 to an atmospheric air port 45.

The upper portion of the housing has a brake valve port 43 for the brake line portion 1, the port 43 having a bore extension 44 which is intersected by the branch passage 34, 35 or 36 which commence at this location. Thus, in the non-energised stat of each pilot valve 11, 12 or 13, an atmospheric air connection leads downwardly from an actuating chamber 37 of the respective main valve 14 by way of the respective passage 40 and through the housing 21,22 or 23 of the respective solenoid valve 11, 12 or 1 3 and then via the port 45 to the atmosphere. The atmospheric air port 45 is common to all valves and is provided on the underside of the housing 1 7. This atmospheric air port 45 is provided with an outwardly opening non-return valve.

Only one valve 14 of the main valves is shown.

The axes of the main valves lie horizontally and are disposed at an angle to one another such that two main valves are located opposite to one another on a common axis, and the axis of the third main valve is at right angles thereto. This renders it possible to provide the valve unit with a very compact type of construction. Moreover, in order to enable water to drain off downwardly, the axis of one of the main valves is disposed at a higher level than the axes of the other main valves.

Each main valve 14 is let into a housing recess 46 which is sealed externally by a cover 49.

The visible main valve 14 is a three-port, twoposition valve (3, 2 valve) and has a closure disc 72 which cooperates with two valve seats 57 and 58. The valve disc 72 is applied to the valve seat 58 by the action of a spring 59. The closure disc 72 is carried by the spherical end 73 of a piston rod 74, the piston rod 74 being connected to an actuating piston 75 which abuts against a diaphragm 56 bounding the actuating chamber 37. The piston rod 74 has a guide in the form of four guide ribs 76 which are received in a housing recess 77 which guides and centres them.

The seat 57 of the visible main valves 14 is connected to the bore extension 44 of the inlet port 43 and the seat 58 is connected to the interior of the housing portion 19 and thereby to the atmospheric port 45. The two non-visible main valves are two-port, two-position valves of which the valve seats (corresponding to the seat 57) are both connected to the valve chamber 1 4a of the visible valve 14. The valve chambers of the other two main valves are connected respectively to the brake branch lines 1', 1".

During normal braking, a free brake line passage exists between the brake valve 2 and the brake cylinders 3 and 4 by way of the brake line 1, 1' and 1", wherein the compressed air flows to the brake cylinders 3 and 4 by way of the visible three-port, two-position main valve 14 and the other two main valves.

The anti-skid system responds when a wheel, such as wheel 7 having the brake cylinder 3, is over-braked, and the pilot valves 11 and 12 change over. The visible main valve 14 is thereby changed over and allows air to flow to the atmosphere from the brake cylinder 3. One of the other (2, 2) main valves at the same time switches to its closed position, so that the pressure is held in the brake cylinder 4 which is not tending to lock the wheel. All the pilot control valves 11,12 and 13 change over at the end of the pressure-drop phase of brake cylinder 3. Thus, the (3, 3) main valve 14 and the one other (2, 2) main valve change back to flow-through, the pressure in the brake cylinder 4 continues to rise, and the third (2, 2) main valve switches to its closed position, so that the reduced brake pressure in the brake cylinder 3 is held.The pilot valve 13 for the last-mentioned main valve is switched off again after a predetermined period of time at the end of the holding phase, so that the last-mentioned main valve again assumes its position for a pressure rise. The reduced brake pressure in the brake cylinder 3 is increased again by switching on and switching off the pilot control valve 13.

The guide ribs 76 ensure satisfactory guidance of the closure member 72 during the switching back and forth of the main valve 14. The guide between the guide ribs 76 and the housing recess 77 is located in a housing portion into which it is difficult for dirt or water to enter. The guide is not located in the region of the passage for compressed air.

Thus, the guide is protected from caking, i.e.

from being soiled or freezing up. Despite the arcuate guidance, it is possible for the valve disc 72 to execute slight tilting movements about the spherical end 73 if the planes of the valve seats do not lie exactly at right angles to the guide.

The illustrated valve unit is for two separate brakes and thus has three main valves. In the case of there being only one brake, one of the (not visible) main valves and the respective solenoid pilot valve would be omitted.

Claims

1. A pressure-control valve unit for an anti-skid brake system of a motor vehicle, comprising a common housing, at least two pressurecontrolled main valves and a respective solenoid pilot valve for each main valve, all the valves being disposed in the common housing which, in use of the valve unit, is so oriented that the solenoid pilot valves are disposed below the main valves and a common atmospheric air port provided for the valves is on the underside of the housing, an actuating piston of one main valve being provided with a piston rod which has guides for guidance in the housing and whose free end carries a deflectable valve closure member of that main valve.

2. A valve unit as claimed in claim 1, in which said valve closure member is in the form of a disc and is tiltably mounted on the free end of the piston rod.

3. A valve unit as claimed in claim 1 or 2, in which the guides are constituted by guide ribs which are formed on the piston rod and which are centered in a housing recess which is contiguous with a valve seat of that main valve.

4. A valve unit as claimed in claim 3, in which the said valve seat communicates with said atmospheric air port and said valve closure member also cooperates with an opposed valve seat with which a brake valve seat communicates.

5. A pressure-control valve unit for an anti-skid brake system, constructed and adapted to operate substantially as herein described with reference to and as illustrated in the drawing.