GB1589154A

GB1589154A - Pressure ratio valve for motor vehicles

Info

Publication number: GB1589154A
Application number: GB2147078A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1978-02-01
Filing date: 1978-05-23
Publication date: 1981-05-07
Also published as: FR2416144B1; FR2416144A1; DE2804217A1

Description

(54) A PRESSURE RATIO VALVE FOR MOTOR VEHICLES (71) We, ROBERT BOSCH GmbH, a German company of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a pressure ratio valve which is usable in a hydraulic two-circuit brake system and has connections for a pressure supply side, a pressure output side and a control line. The connections are connected to a valve member in which a nonreturn valve is integrated in such a manner that it is fixed in an operable state without any additional means.The pressure which is set up on the pressure output side is dependent upon both the pressure on the pressure supply side and the pressure in the control line, the latter pressure being influenced again by a load-dependent braking force regulator in the brake circuit.

It is here pointed out that by a pressure ratio valve is meant a valve which determines the ratio of the braking pressures developed in the two circuits and the braking system.

In the pressure ratio valve known from German Offenlegungsschrifi 25 50 674, the non-return valve comprises an O-ring which rests in a groove from which several radial channels lead into an inner blind bore.

A non-return valve of this construction, although very simple, is very susceptible to breakdown, is almost impossible to adjust and does not guarantee any functional continuity.

The aim of the present invention is to provide a pressure ratio valve which, particularly because of the design and disposal of the non-return valve, is not only easy to manufacture but also operates over a long time reliably and is adaptable to different circumstances.

There is provided by the present invention a pressure ratio valve for motor vehicles having a stepped valve member which is movably journalled in a valve housing and is provided with a larger surface acting in a closing direction and with two smaller surfaces acting in an opening direction, the larger surface being acted upon by the pressure on a pressure output side, one smaller surface being acted upon by the pressure on a pressure supply side and the other smaller surface being acted upon by the pressure of a control line receiving a load-dependent regulated brake pressure, and having a non-return valve in the valve member between the pressure supply side and the pressure output side, wherein the valve member comprises two parts and the non-return valve is inserted between the two parts and has a sealing part which is biassed by a spring towards a valve seat and by the pressure on the pressure output side away from said valve seat.

The pressure ratio valve according to the present invention compared to prior art, has the advantage that the risk of the non-return valve's failing is very much reduced, and because of the spring construction and dimensioning good adaptation is possible. It is also possible to achieve a compact, spacesaving construction of few components which is easy to manufacture.

An embodiment of the invention is illustrated in the accompanying drawings in which: Fig. 1 is a diagrammatic reproduction of a hydraulic two-circuit brake system having a pressure ratio valve according to the invention, and Fig. 2 is a longitudinal section through the pressure ratio valve.

A hydraulic main brake cylinder I, preferably in the form of a tandem cylinder, serves as a pressure supply for the supply of two brake lines 2, 3 (brake circuits I and II). One brake line 2 is connected by a load-dependent braking force regulator 4 to brake cylinders 5, 6 of a rear axle 7 of a motor vehicle (not shown). The other brake line 3 leads by way of a pressure ratio valve 8 to brake cylinders 9, 10 of a front axle 11. To control the load dependence, the braking force regulator 4 is connected by a linkage 12 to the rear axle 7; it being understood that the brake cylinders 5, 6, 9, 10 are pressure receivers.

The construction of the pressure ratio valve 8 may be seen in Fig. 2 which reproduces the pressure ratio valve in detail on an enlarged scale. In a cast iron valve housing 13 there is a stepped bore 14 into which a valve member 15 is inserted. The valve member 15 comprises two piston-like parts 16, 17 which are journalled axially in one another and in the stepped bore 14 displaceably relative to one another, and between which a non-return valve 18 is accommodated. The part 16 of the valve member 15 forms a stepped piston having a larger surface 19 and a smaller surface 20. It has a central through-bore 21 having a shoulder 22 which forms a valve seat 23 for a sealing part 24 of the non-return valve 18.

The part 17 comprises a ram element 25, which is accommodated in the through-bore 21, a surrounding collar 26 and a piston part 27. The collar 26, the piston part 27, a cylinder part 28 of the part 16 and ribs 29 are guided in the stepped bore 14 which also comprises a stop 30 for a front face 31 of the piston part 27 and a conical valve seat 32 for the valve member 15. The piston part 27 of the part 17 and the cylinder part 28 of the part 16 are sealed off from the valve housing 13 by sealing washers 33, 34. A relieving connection 35 prevents possible leakages from influencing operation. While the piston part 27 projects from one side 36 of the collar 26, the other side 37 comes to rest against the front face 38 of the part 16. The through bore 21 is tightly closed on one side by the ram element 25 and a sealing washer 39 located on said element.

The sealing part 24 of the non-return valve 18 is in the form of a cup 40 which is axially displaceably journalled in the through-bore 21 of the part 16, the front part of the ram element 25 being accommodated in the cup 40 and the front face 41 forming an abutment for one end of a spring 42 whose other end is supported on the cup base 43. This spring 42 urges an outer cone 44 of the cup base 43 towards the valve seat 23. In an opening direction, the movement of the sealing part 24 is limited by a stop 45 on the ram element 25.

The valve member 15 constitutes a unit to which belong the parts 16, 17, the non-return valve 18 and the sealing washers 33, 34. This unit is inserted from one side into the stepped bore 14 of the valve housing 13 and this bore is then closed tightly by a closure member 46.

Further fixing means are not required. The chamber 47 between the greater surface 19 of the part 16 and the closure member 46 is connected to the pressure output side 48. The line to the brake cylinders 9, 10 of the front axle 11 is connected to a connection 49. The pressure supply side 50 acts upon the smaller surface 20 of the part 16, a connection 51 being connected to the main brake cylinder I. Finally, the pressure of a control line 53 which is influenced by the load-dependent braking force regulator 4 acts upon the front face 31 of the piston part 27 as a further smaller surface 52 of the valve member 15.

The control line 53 is connected by a connection 54 to the pressure ratio valve. A relief valve 56 permitting venting of the entire system is placed in a transverse channel 55 connected to the connection 54.

If a pressure exists on the pressure supply side 50, the part 16 of the valve member 15 is withdrawn from the valve seat 32 until a pressure is formed in the chamber 47 which, in conjunction with the larger surface 19, conveys the valve member 15 back onto the seat 32. This means that the pressure originating from the main brake cylinder 1 only comes into effect in a correspondingly reduced manner at the brake cylinders 9, 10 of the front axle 11 in the brake circuit II. This reduced effective output pressure may be increased by the pressure prevailing in the control line 53 and acting upon the smaller surface 52 so that the part 17 acts by way of the side 37 of the collar 26 upon the part 16 in the sense of assisting the withdrawal from the valve seat 32.With increasing brake pressure in the brake cylinders 5, 6 of the rear axle 7 controlled by the brake force regulator 4, the brake pressure in the brake cylinders 9, 10 of the front axle 11 is therefore also correspondingly increased. If the pressure on the pressure output side decreases for any reason, for example, because of leakage losses or enlargement of the medium-filled chambers, the valve member 15 opens and allows the leakage quantity to flow back. If the pressure on the pressure supply side 50 is decreased (e.g. end of braking process), the non-return valve 18 opens and allows fluid to flow from the pressure output side (48) to the pressure supply side (50) until, below a threshold pressure, the valve member 15 opens again. The relief connection 35 between the sealing washers 33, 34 prevents pressure from passing over from one brake circuit to the other.

WHAT WE CLAIM IS: 1. A pressure ratio valve for motor vehicles having a stepped valve member which is movably journalled in a valve housing and is provided with a larger surface acting in a closing direction and with two smaller surfaces acting in an opening direction, the larger surface being acted upon by the pressure on a pressure output side, one smaller surface being acted upon by the pressure on a pressure supply side and the other smaller surface being acted upon by the pressure of a control line receiving a load-dependent regulated brake pressure, and having a non-return valve in the valve member between the pressure supply side

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The construction of the pressure ratio valve 8 may be seen in Fig. 2 which reproduces the pressure ratio valve in detail on an enlarged scale. In a cast iron valve housing 13 there is a stepped bore 14 into which a valve member 15 is inserted. The valve member 15 comprises two piston-like parts 16, 17 which are journalled axially in one another and in the stepped bore 14 displaceably relative to one another, and between which a non-return valve 18 is accommodated. The part 16 of the valve member 15 forms a stepped piston having a larger surface 19 and a smaller surface 20. It has a central through-bore 21 having a shoulder 22 which forms a valve seat 23 for a sealing part 24 of the non-return valve 18. The part 17 comprises a ram element 25, which is accommodated in the through-bore 21, a surrounding collar 26 and a piston part 27. The collar 26, the piston part 27, a cylinder part 28 of the part 16 and ribs 29 are guided in the stepped bore 14 which also comprises a stop 30 for a front face 31 of the piston part 27 and a conical valve seat 32 for the valve member 15. The piston part 27 of the part 17 and the cylinder part 28 of the part 16 are sealed off from the valve housing 13 by sealing washers 33, 34. A relieving connection 35 prevents possible leakages from influencing operation. While the piston part 27 projects from one side 36 of the collar 26, the other side 37 comes to rest against the front face 38 of the part 16. The through bore 21 is tightly closed on one side by the ram element 25 and a sealing washer 39 located on said element. The sealing part 24 of the non-return valve 18 is in the form of a cup 40 which is axially displaceably journalled in the through-bore 21 of the part 16, the front part of the ram element 25 being accommodated in the cup 40 and the front face 41 forming an abutment for one end of a spring 42 whose other end is supported on the cup base 43. This spring 42 urges an outer cone 44 of the cup base 43 towards the valve seat 23. In an opening direction, the movement of the sealing part 24 is limited by a stop 45 on the ram element 25. The valve member 15 constitutes a unit to which belong the parts 16, 17, the non-return valve 18 and the sealing washers 33, 34. This unit is inserted from one side into the stepped bore 14 of the valve housing 13 and this bore is then closed tightly by a closure member 46. Further fixing means are not required. The chamber 47 between the greater surface 19 of the part 16 and the closure member 46 is connected to the pressure output side 48. The line to the brake cylinders 9, 10 of the front axle 11 is connected to a connection 49. The pressure supply side 50 acts upon the smaller surface 20 of the part 16, a connection 51 being connected to the main brake cylinder I. Finally, the pressure of a control line 53 which is influenced by the load-dependent braking force regulator 4 acts upon the front face 31 of the piston part 27 as a further smaller surface 52 of the valve member 15. The control line 53 is connected by a connection 54 to the pressure ratio valve. A relief valve 56 permitting venting of the entire system is placed in a transverse channel 55 connected to the connection 54. If a pressure exists on the pressure supply side 50, the part 16 of the valve member 15 is withdrawn from the valve seat 32 until a pressure is formed in the chamber 47 which, in conjunction with the larger surface 19, conveys the valve member 15 back onto the seat 32. This means that the pressure originating from the main brake cylinder 1 only comes into effect in a correspondingly reduced manner at the brake cylinders 9, 10 of the front axle 11 in the brake circuit II. This reduced effective output pressure may be increased by the pressure prevailing in the control line 53 and acting upon the smaller surface 52 so that the part 17 acts by way of the side 37 of the collar 26 upon the part 16 in the sense of assisting the withdrawal from the valve seat 32.With increasing brake pressure in the brake cylinders 5, 6 of the rear axle 7 controlled by the brake force regulator 4, the brake pressure in the brake cylinders 9, 10 of the front axle 11 is therefore also correspondingly increased. If the pressure on the pressure output side decreases for any reason, for example, because of leakage losses or enlargement of the medium-filled chambers, the valve member 15 opens and allows the leakage quantity to flow back. If the pressure on the pressure supply side 50 is decreased (e.g. end of braking process), the non-return valve 18 opens and allows fluid to flow from the pressure output side (48) to the pressure supply side (50) until, below a threshold pressure, the valve member 15 opens again. The relief connection 35 between the sealing washers 33, 34 prevents pressure from passing over from one brake circuit to the other. WHAT WE CLAIM IS:

1. A pressure ratio valve for motor vehicles having a stepped valve member which is movably journalled in a valve housing and is provided with a larger surface acting in a closing direction and with two smaller surfaces acting in an opening direction, the larger surface being acted upon by the pressure on a pressure output side, one smaller surface being acted upon by the pressure on a pressure supply side and the other smaller surface being acted upon by the pressure of a control line receiving a load-dependent regulated brake pressure, and having a non-return valve in the valve member between the pressure supply side

and the pressure output side, wherein the valve member comprises two parts and the non-return valve is inserted between the two parts and has a sealing part which is biassed by a spring towards a valve seat and by the pressure on the pressure output side away from said valve seat.

2. A valve as claimed in claim 1, in which one part of the valve member has a throughbore having a shoulder, the shoulder forms the valve seat and the sealing part is displaceable guided axially in the through-bore.

3. A valve as claimed in claim 2, in which the sealing part is cup-shaped and the cup base on the one hand has an outer cone with which it rests against the valve seat and on the other hand serves as an abutment for the spring housing inside the cup.

4. A valve as claimed in claim 2 or 3, in which projecting into the through-bore of one part of the valve member is a ram element of the other part and the ram element tightly closes the through-bore on the side remote from the non-return valve.

5. A valve as claimed in claim 4, in which a sealing washer is provided for a tight closure between the ram element and the through-bore.

6. A valve as claimed in claim 4 or 5, in which the ram element forms a stop for the sealing part of the non-return valve.

7. A valve as claimed in claim 3 and any of claims 4 to 6 as dependent on claim 3, in which the spring of the non-return valve is clamped between the cup base and the front face of the ram element.

8. A valve as claimed in claim 3 and any of claims 4 to 7 as dependent on claim 3, in which the ram element projects into the cup.

9. A valve as claimed in claim 4 and any of claims 5 to 8 as dependent on claim 4, in which a collar surrounds the ram element, one side of said collar being appliable to the front face of one part of the valve member, and there being a piston part originating from the other side of said collar, the front face of said piston part forming the one smaller surface which is acted upon by the pressure of the control line.

10. A valve as claimed in claim 9, in which the piston part of one part and a cylinder part of the other part are sealed off from the valve housing by sealing washers and a relief connection is provided between the two sealing washers.

I I. A valve as claimed in any of the preceding claims. in which the two parts may be inserted from one side into a stepped bore in the valve housing.

12. A valve as claimed in claim I I, in which the stepped bore forms a stop for one front face of the piston part of one part and forms the valve seat for the valve member and is closed on the insert side by a sealed closure member, the pressure output side being connected to the chamber between the larger surface of the valve member and the closure member.

13. A pressure ratio valve substantially as hereinbefore described with reference to the drawings.

14. A braking system incorporating a valve according to any of the preceding claims.