GB1580222A

GB1580222A - Pressure control valve for an anti-skid braking system for compressed-air-operated brakes of a motor vehicle

Info

Publication number: GB1580222A
Application number: GB2976477A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1976-07-17
Filing date: 1977-07-15
Publication date: 1980-11-26
Also published as: FR2358300A1; SE7708199L; FR2358300B1; DE2632305A1

Description

(54) PRESSURE CONTROL VALVE FOR AN ANTI-SKID BRAKING SYSTEM FOR COMPRESSED-AIR-OPERATED BRAKES OF A MOTOR VEHICLE (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 pressurecontrol valve of an anti-skid braking system for compressed-air-operated brakes of a motor vehicle, comprising at least one main valve and at least one pilot control solenoid valve.

An anti-skid braking system of this type is known (German Offenlegungsschrift 2 219 212). In an anti-skid braking system of this type, the individual members of the system may be adjusted in their operating behaviour, although their operating reliability following adjustment is not fully satisfactory at least under extreme operating conditions.

Thus, satisfactory function of the valves is not always ensured in the case of a wet road or at low temperature in winter. A considerable amount of expenditure is normally involved in the drainage of the brake pressure control valves in conventional compressed air brake systems. However, the formation of water of condensation is greatly increased in anti-skid systems, this being promoted by the rapid pressure change. In addition to promoting corrosion, this effect also leads to the risk of ice formation in winter and thus possibly to the complete failure of the system to function.

In contrast to this, the anti-skid braking system using the valve in accordance with the invention has the advantage that water produced in the pressure control valve is reliably drained off to the outside, so that the valve unit cannot fail as a result of corrosion and/or the formation of ice. The control chambers of the or each main valve and the or each pilot control solenoid valve are arranged on the pressure-control valve such that water of condensation which is produced is conveyed to the atmosphere solely by gravity by way of a direct connection in the solenoid valve.

Furthermore, the control chambers in the pressure-control valve may be of a construction which effectively prevents the freezing of the actuating members but which nevertheless ensure the full operating surface of the actuating members remains effective, and that the heat of the electromagnet employed in the solenoid of the or each solenoid valve may be used to de-ice the valve unit.

Embodiments of the invention are illustrated by way of example, in the accompanying drawings in which: Fig. 1 shows a section through a pressurecontrol valve unit; Fig. 2 shows a detail of a different pressure-control valve unit; Fig. 3 shows the special construction of a control chamber wall, Fig. 4 shows a modification of the construction shown in Fig. 3, and Fig. 5 shows a different construction of a control chamber wall.

Referring now to the drawings, a compressed air brake system has a compressor 1, a pressure reservoir 2, a brake valve 3, and a wheel brake cylinder 4. The pressure-control valve unit 7 of the embodiment is incorporated in a brake line 5, 6 leading from the brake valve 3 to the wheel brake cylinder 4, the passage through the brake line being interrupted by the pressure-control valve unit 7 when locking of the wheels is to be prevented.

Two main valves 8 and 9 and two pilot control valves 10 and 11 are provided in the pressure-control valve unit 7. The pair od valves comprising the pilot control 10 and the main valve 8, and the pair of valves comprising the pilot control valve 11 and the main valve 9, co-operate with one another. Thus, the pair of valves 8 and 10 control an inlet seat 12, and the pair of valves 9 and 11 control an outlet seat 13, the inlet seat and the outlet seat being provided in the housing of the pressure-control valve unit 7.

The actuating member of the main valve 8 is a double diaphragm element 16 comprising two diaphragms 14 and 15 with a thrust member 17 arranged between the diaphragms; the space above the actuating member (as seen in Figure 1) being the valve actuating chamber of the main valve.

A control chamber 18 is located below the diaphragm 15 and communicates with the atmospheric air by way of the pilot control solenoid valve 10 when the latter is unenergised, communication with the atmospheric air being effected through an outlet opening 19 in the solenoid valve 10. The outlet opening 19 is located immediately below an outlet valve seat which, when the magnet is energised, is closed by a closure body 22 of the valve arranged on an armature 21. When the solenoid valve 10 is in its illustrated, unenergised, starting position, the mouth of a pressure passage 23 is closed by a closure body 24 of the armature 21, the pressure passage 23 communicating permanently with the opening in the inlet seat 12.

The other main valve 9 has a diaphragm 25 which defines a control chamber 26. The working region of the diaphragm is connected by way of a thrust member 27 to a spring-loaded closure body 28 which normally closes the outlet seat 13. The outlet seat 13 may communicate with the atmospheric air by way of a passage 29 and a non-return valve 30.

The control chamber 26 communicates with the atmospheric air by way of the pilot con trol solenoid valve 11, when the valve is unenergised, communication with the atmos pheric air being effected through an outlet opening 31 in the solenoid valve. The outlet opening 31 is located immediately below an outlet valve seat 32 which, when the magnet is energised, is closed by means of a closure body 34 of the valve secured to the armature 33. When the solenoid valve 11 is in its illu strated, unenergised, starting position, the mourh of a pressure passage 35 is closed by a closure body 36 of the armature 33, the pressure passage 35 communicating perma nently with the opening in the inlet seat 12.

An advantage od the illustrated embodiment is that the two pilot control solenoid valves 10 and 11 are identical.

During a normal braking operation, the two control chambers 18 and 26 communicate with the atmospheric air. Thus, no water collects. Water produced during an anti-skid regulation braking operation is immediately conveyed to the atmosphere.

It will be seen that the control chambers 18 and 26 in the pressure-control valve unit 7, and the pilot control solenoid valves 10 and 11, are arranged such that water of con densation produced from the compressed air is discharged solely by gravity into the atmosphere through the outlet passages 19 and 31 in the solenoid valves 10 and 11.

This also applies to an embodiment of a pressure-control valve unit 40 of the type illustrated in Fig. 2. The detail shown in Fig. 2 shows that a main valve 41, having its axis horizontal, is controlled by means of a perpendicularly arranged pilot control valve 42. A control chamber 43 of the main valve 41 which is of wedge-shaped configuration in the cross section illustrated, and which is defined by a diaphragm 46 acting as an actuating member, is connected to the solenoid valve 42 such that the water of condensation flows out of the chamber 43 and can then flow out of the solenoid valve 42 to a bottom outlet opening 45 by way of an outlet air passage having a drainage surface and by way of an outlet valve seat 44. The control chamber 43 is arranged above the outlet valve seat 44 of the solenoid valve 42.

Figs. 3 and 4 show, in the form of a plan view and an end view, the construction of a wall 47, 48 or 49, located opposite the diaphragm 15, 25 or 46 respectively, of the control chamber 18, 26 or 43. The wall 47, 48 or 49 is provided with recesses 50 which may be arranged symmetrically as shown in Fig. 3 and, as is shown in Fig. 4, may be arranged so as to be larger towards one edge of the wall than they are elsewhere. Projections are left between the recesses 50. The construction shown in Fig. 3 has a central outlet 54. The construction shown in Fig. 4 is intended for the control chamber 43 (Fig.

2). It has a lateral outlet 55 which, when in the fitted state, is located at the bottom-most point d the control chamber 43.

Annular recesses 51 are used in the embodiment shown in Fig. 5 and may also be provided in the wall 47, 48 or 49 of the control chamber 18, 26 or 43.

In the manner shown in Figs. 3 to 5, the support surface for the diaphragms 15, 25 or 46 is interrupted by rectangular or annular depressions. Thus, the diaphragm is prevented from freezing to the wall of the control chamber, and the pressure-control valve unit is prevented from failing.

Windings 52 and 53 of the solenoid of the pilot control valves 10 and 11 are illustrated in Fig. 1. Advantageously, the heating effect of these windings 52 and 53 is used to prevent the freezing of the pressurecontrol valve unit 7.

For this purpose, an electrical circuit has to be provided which applies voltage to the two windings 52 and 53 for a short, limited period of time when the vehicle is stationary, such that, enhanced by the relatively high current density of the solenoids provided, the windings 53 and 52 are heated rapidly when current is flowing.

The following circuit features are provided in order to exclude negative effects such as undesirable releasing of the brakes or the absence of a build-up of pressure during the heating phase; 1. The heating current is permitted to flow only when the vehicle is stationary, for example, during the test programme.

2. The solenoid valves are energised successively in accordance with the requirements of the anti-skid electronics, so that at least one circuit always maintains the vehicle ready for braking action (important in the case of a sloping roadway).

3. As soon as the vehicle wheels start to rotate, measurable by way of the sensor signals, for example, when the driver puts the vehicle into motion or, alternatively, is unintentionally put into motion as a result of a reduction in the action of the parking brake when a test programme is being carried out on a sloping roadway, the control of the supply to the magnet coils for the purpose of heating is immediately interrupted.

In addition to a complete operational test by means of a test programme, these measures also ensure optimum operating reliability of the brakes in normal use of the vehicle.

WHAT WE CLAIM IS:- 1. A pressure control valve for an antiskid braking system for compressed-airoperated brakes of a motor vehicle, which braking system comprises a brake valve and brake cylinder which are interconnected by way of a brake line, the pressure-control valve comprising at least one pilot control solenoid valve comprising at least one pilot control solenoid valve and at least one main valve formed with a control chamber and an actuating chamber, a communicating passage connecting a bottom portion of the control chamber with a housing for the solenoid valve and the solenoid valve housing having a bottom outlet opening incorporating an outlet valve seat, the control chamber of the main valve being arranged above the outlet valve seat of the solenoid valve, and the bottom of the control chamber, the communication passage and the solenoid housing being such as to provide a gravitational flow path to enable water formed in the control chamber to pass to the bottom outlet opening without lodgement.

2. A valve as claimed in claim 1, wherein the or each solenoid valve comprises an armature having a valve closure member to be moved between an upper inlet valve seat and the bottom outlet valve seat, the solenoid valve being arranged so that normally the valve closure member leaves the bottom outlet valve seat free to permit water produced in the control chamber of the main valve to be discharged to the exterior of the valve.

3. A valve as claimed in claim 1 or 2, wherein the main valve is arranged to lie in use with its axis horizontal, and the lower region of the control chamber slopes towards the outlet valve seat.

4. A valve as claimed in any of the claims 1 to 3, wherein recesses are provided in the pressure-conrol valve unit in the wall located opposite to the actuating member of the main valve, the recesses are provided in the control pressure chamber, and the recesses slope towards the outlet valve seat of the solenoid valve.

5. A valve as claimed in any of the claims 1 to 4, wherein the thermal energy from the heating-up of the winding of the or each pilot control solenoid valves is used for de-icing in the pressure-control valve unit.

6. A pressure-control valve for an antiskid braking system for the compressed-airoperated brakes of a motor vehicle, substantially as hereinbefore described with reference to Figure 1 or to Figure 2 of the accompanying drawings.

7. A pressure-control valve for an anti-skid braking system for the compressed-airoperated brakes of a motor vehicle, substantially as hereinbefore described with reference to Figure 1 and Figure 3 or 5 of the accompanying drawings.

8. A pressure-control valve for an anti-skid braking system for the compressed-airoperated brakes of a motor vehicle, substantially as hereinbefore described with refer ence to Figures 2 and 4 of the accompanying drawings.

9. An anti-skid compressed air-operated braking system for a motor vehicle, whenever comprising a pressurecontrol valve according to any of the preceding claims.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. undesirable releasing of the brakes or the absence of a build-up of pressure during the heating phase; 1. The heating current is permitted to flow only when the vehicle is stationary, for example, during the test programme. 2. The solenoid valves are energised successively in accordance with the requirements of the anti-skid electronics, so that at least one circuit always maintains the vehicle ready for braking action (important in the case of a sloping roadway). 3. As soon as the vehicle wheels start to rotate, measurable by way of the sensor signals, for example, when the driver puts the vehicle into motion or, alternatively, is unintentionally put into motion as a result of a reduction in the action of the parking brake when a test programme is being carried out on a sloping roadway, the control of the supply to the magnet coils for the purpose of heating is immediately interrupted. In addition to a complete operational test by means of a test programme, these measures also ensure optimum operating reliability of the brakes in normal use of the vehicle. WHAT WE CLAIM IS:-

1. A pressure control valve for an antiskid braking system for compressed-airoperated brakes of a motor vehicle, which braking system comprises a brake valve and brake cylinder which are interconnected by way of a brake line, the pressure-control valve comprising at least one pilot control solenoid valve comprising at least one pilot control solenoid valve and at least one main valve formed with a control chamber and an actuating chamber, a communicating passage connecting a bottom portion of the control chamber with a housing for the solenoid valve and the solenoid valve housing having a bottom outlet opening incorporating an outlet valve seat, the control chamber of the main valve being arranged above the outlet valve seat of the solenoid valve, and the bottom of the control chamber, the communication passage and the solenoid housing being such as to provide a gravitational flow path to enable water formed in the control chamber to pass to the bottom outlet opening without lodgement.