GB2115894A - Hydraulic brake control apparatus - Google Patents

Abstract

The hydraulic control apparatus has a flow regulating valve (16) and a braking device (51, 52, 71, 89). During a braking operation, the pressure medium delivered by the pump is conveyed by the flow regulating valve and a non- return valve (38) to the brake cylinder (89). In that way, pressure is exerted on the piston (52) together with the slide (51) whereupon the latter is so adjusted that a neutral circulation flow from the pump to the reservoir is produced and pressure medium can flow to the braking device. In order to prevent a fixed throttling or seizing of the slide (51) the pressure medium included in an annular space (90) arranged between it and a sealing sleeve (54) must be able to flow away through a throttle disc(91). By using the throttle disc, the pressure difference at the slide (51) is increased whereupon a seizing of the latter is prevented. <IMAGE>

Description

SPECIFICATION Hydraulic control apparatus The invention originates from an hydraulic control apparatus according to the preamble to the main claim. With one such known apparatus, energy is only required forthe initiation ofthe braking operation and forthe correction of the braking pressure. When the pressure difference ofthe braking pressure during its correction or during readjustment is not great enough, a slide in the braking device is inclined towards fixed throttling, that is to say the slide is no longer moved as it should be which leads to failures in the control apparatus.

As opposed to this, the control apparatus in accordance with the invention comprising the characterising features ofthe main claim has the advantage thatthe pressure difference of the braking pressure during the correction or during readjustment thereof is increased. In that way, thefixed throttling ofthe slide is also prevented.

Advantageous further developments and improvements of the features set forth in the main claim are made possible by the measures set forth in the sub claims.

An embodiment of the invention is illustrated in the drawing and is explained in detail in the following description. The drawing shows, in partial section, a diagrammatic representation of a longitudinal sec tionthrough an hydraulic control apparatus.

The control apparatus has a valve housing 10 comprising a longitudinal bore 11 passing th rough it to which is connected a delivery line 12 into which a pump 13 delivers pressure medium from a reservoir 14. Acontrol slide 15 of a flow regulating valve 16 is slidingly guided in the longitudinal bore 11 and acts on a control spring 17 againstthe inflowing pressure medium. The rear portion of the bore 18 in which the control spring is arranged is sealed by a closure screw 19. Three triangular notches 21 are formed at the end ofthe control slide 1 Sfacing the inlet 20to the longitudinal bore 11.

A diaphram 24 is arranged inside the control slide 15 and a throttle 25 of a substantially smaller diameterthan that of the diaphram 24 is arranged down-stream thereof. Three annular grooves 26,27, 28 are formed in the longitudinal bore 11. A bore 29 leads from the annular groove 26to the exterior of the valve housing; a return line 30 which leads to the reservoir 14 is connected at that location. Athrottle disc 32 through which the control spring 17 acts on the control slide 15 is arranged in the rear portion of the control slide 15. The throttle disc32 simply provides damping of the movement of the control slide 1 Abduct 35 into which enters a housing bore 36 in which a valve insert37 provided with a conical non-return valve 38 is inserted, issues into the annular groove 27.A duct 39 proceeds from the housing bore 36 and issues into a longitudinal bore 40 running parallel to the longitudinal bore 11.

A duct 43 which issues into an annular groove47 at a widened portion 40' of the longitudinal bore 40, proceeds from the annular grove 28. A plurality of radial bores 44 which are atthe Ievelofthe annular groove 27 issue into the space 45 in the control slide located between the diaphragm 24 and the throttle bore 25. A plurality of radial bores46whichareatthe level of the annular groove 28 issue into the hollow control slide downstream of the throttle bore 25.

A cup-like housing insert 49 in the housing bore 50 of which a slide 51 is slidingly mounted, is arranged in the wideopen portion 40' of the longitudinal bore 40.

A piston 52 is fixed to the slide and its left-hand portion 52' slides in a bore portion 53 extending coaxiallywith respecttothehousing bore50whilst its right-hand portion 52" is guided outwardly bya sealing sleeve 54. The sealing sleeve is supported by a disc 55 against which a spring 56 wound around the right-hand portion 52" of the piston also engages and the other end of which engages a spring abutment 58.

The latter is arranged in a piston 59 which is slidingly mounted in a bore 60 which extends coaxially with respectto the housing bore 40. Springs 61,62 act on the spring abutment. The bore 60 is ciosed by a housing 64in which isformed a longitudinal bore 65 which extends coaxiallywith respect to the housing bore 40. A piston 66 is sealingly slidingly mounted in the longitudinal bore 65. It has atappet67which engages a closure screw 68 closing the longitudinal bore 65. Atransverse bore 69to which a line 70 is attached extends in the housing 64 and issues into the longitudinal bore 65. The line proceeds from a pressure sensor 71 which is actuable by a brake pedal 72.An air bleeding device 73 is also connected to the longitudinal bore 65.

The annularwall 51' ofthe slide 51 is interrupted by a transverse bore 76, the end wall is interrupted by a bore 75; the former issues into an annular groove 77 which co-operates with an annular groove 78 in the housing insert49. However,thetwoannulargrooves 77,78 are in communication with one another and thus with the duct 43 through a transverse bore 79 passingthroughthe housing insert 49. An inclined bore 81 extends from the space 80 within the housing insert 49 into an annular groove 82 in the bore portion 40' of the housing bore 40. A bore 83 extends from the annulargroove 82 to the outside ofthe housing.A longitudinal bore85 from which a transverse bore 86 extends outwardly and in a particular position of the slide 51 is in communication with the space 80, is located in the left-hand portion 52' of the piston 52. A line 88 leads from the longitudinal bore 40 to a brake cylinder89. Athrottle disc 91 the inner diameter91' of which forms a throttle gap 92 with the outer diameter ofthe piston 52, is arranged in the slide 51. The throttle disc 91 is maintained in position by a corrugated washer 94 supported against a securing ring 93. A line 96 leads from the bore 83 to the reservoir 14.

The control apparatus operates as follows: The pump 13 delivers pressure medium through an inlet 20 into the lonitudinal bore 11 whereby it also arrives in the interior ofthe control slide. A portion of this pressure medium flows through the diaphragm 24, the throttle bore 25 and the throttle disc 32 into the space 18 A control oil stream flows through the throttle bore 25 to the transverse bore 46, from there into the annular groove 28 and the duct 43, from there throughthe annulargroove47intothetransverse bore 79 ofthe housing insert 49 and then into the annular grooves 78,77 and the transverse bore 76 into the space 80. From there, the pressure medium flows through the inclined bore 81 and the line 96 to the reservoir 14.As a result of the flow resistance at the diaphragm 25 and the thus generated pressure difference, the control slide 15 is moved towards the right against the force of the control spring 17 and produces communication to the annular groove 26 and to the line 30 andthusto the reservoir through the triangularnotches21.

When the brake pedal 72 is actuated, pressure builds up in the line 70 and in the bores 69 and 65 and the piston 66 is moved towards the left againstthe piston 59. The spring abutment 58 pushes against the piston 52 whereupon the latter is pushed towards the lefttogetherwith the slide 51. In that way, the communication from the duct 43 to the space 80 is interrupted so that control oil can no longer flow awaytothe reservoir 14. Thus, the pressure difference atthe diaphragm 25 is reduced and the spring 17 moves the control slide 15 towards the left whereupon the transverse bores 44 come into communication with the annular groove 27.Then, due to the pressure drop at, the diaphragm 24, a portion ofthe pressure medium delivered by the pump 13 is conveyed into the duct 35 and through the open non-return valve 38 into the duct 39 and from there into the longitudinal bore 40 as well as into the line 88 and to the brake cylinder 89. During a re-setting, that isto say an increase in the brake pressure, the piston 52 is displacedtowa rds the right whereby it entrains the slide 51. The annular groove 77 again produces communication to the reservoir 14through the line 96 whereupon the pressure in the duct 43 drops.Thus, the control slide 15 oftheflow regulating valve is displaced towards the right against the force ofthe control spring 17 whereupon the pressure medium delivered bythe pump 13flowsawaytothe reservoir through the triangular notches 21, the annular groove 26 connected thereto and the line 30.

During the movement ofthe piston 52 together with the slide 51 due to the re-setting ofthe brake pressure referred to above, the pressure medium enclosed in the annular space 90 must be displaced through the throttle gap 92 atthethrottle disc91. As a result ofthe throttling effect, the pressure difference atthe slide 51 is increased and with it the force for adjusting the piston 52 so thatthe danger of fixed throttling ofthe slide 51 is reduced. lithe throttle disc were not provided, only a very small or even no pressure difference would exist at that location and the slide 51 could remain suspended whereupon the operation of the control apparatus would be impaired.

Claims (5)

1. Hydraulic control apparatus which supplies pressure medium delivered from a pressure medium source through aflow regulating valve 15to a load or to a reservoir and supplies a brake cylinder (89) through an hydraulically controllable braking device during its activation whereby a control oil flow branchedfromtheflow regulating valve is inter- rupted and a brake pressure is generated in the braking device, which has a piston 52 connected to the slide (51), which passesthrough a seal (54) and engages a spring abutment (58) wherein between the seal and the slide a pressure medium filled annular space (90) is provided which is displaced to the return on movement ofthe slide, characterised in that, a throttle means (91) is arranged inthe connection from the annular space (90) to the return (81,96).

2. Apparatus according to claim 1, characterised in that, the throttle means is a disc (9f iarranged in the annular space (90), the bore (91') of which forms à throttle gap (92) with the outer diameterofthe piston (51).

3. Apparatus according to claim 1 and/or2, characterised in that, the throttle means is held fast by a corrugated washer (94) supported buy a securing ring (93).

4. Apparatus according to one of claims 1 to 3, characterised in that, a damping throttle (32) is arranged in the rear portion ofthe control slide (15) of the flow regulating valve.

5. Hydraulic control apparatus substantially as herein described with reference to the accompanying drawing.