DE3632384A1 - Electrical control device for pressure monitoring in brake systems for motor vehicles - Google Patents

Abstract

In order to monitor the operational readiness of a pressure medium pump (30) for supplying a motor vehicle hydraulic brake system, a piston arrangement (36, 37) is provided, one active surface of which can be acted upon by the pressure at the pump outlet (28) and the opposing active surface of which by the pressure in the brake lines (13, 14). If the pump pressure is too low, the piston arrangement (36, 37) is displaced by the pressure in the brake lines (13, 14) and a radially arranged tappet (45), which is fixed on a contact plate (47), is swivelled by means of an annular flange (43). In its rest position, the contact plate (47) is pressed by a compression spring (59) against two contact elements (54, 55), arranged at an interval from one another. Due to the swivelling of the tappet (45) the contact plate (47) moves into a tilted position, being raised by a contact element (55). The control device is characterised by an especially short contact travel. <IMAGE>

Description

The invention relates to an electrical switching device for Pressure monitoring in a hydraulic brake system for Motor vehicles with one of the pressure in a brake line acted upon piston assembly and one through the pistons arrangement movable switching element.

Electrical switching devices of the type specified can serve in brake systems where a pressure medium pump pe directly in without a pressure accumulator a brake line promotes the operational readiness of the Monitor the pressure medium pump in order to prevent the pump For example, switch off a brake slip control device can and thereby a collapse of the Bremsdruckge Avoid using controlled brake pressure.

In one in the older patent application P 36 01 914.3 be Brake system is written to monitor the pump pressure a differential pressure warning switch is provided that the output pressure of the pressure medium pump with the pressure in the two brakes circles the brake system compares and when exceeded operated a switch at a certain pressure difference. It it has now been found that the additional need for printing with tel volume from a differential pressure warning switch to Carrying out a switching operation is necessary after partly affects the volume balance of the brake system.

The invention is therefore based on the object of an electri cal switching device for monitoring a pressure in a to create hydraulic braking system, which is characterized by a low volume requirements.

This object is achieved in that a Movement of the piston assembly on one transverse to its longitudinal axis pivotally arranged plunger is transmitted to the a contact plate at its end facing away from the piston arrangement carries one spring against two spaced apart Arranged, fixed contact members can be pressed. A Such switching device has the advantage that one small pivoting movement of the plunger is enough to get one out Adequate distance between the contact plate and one Generate contact member. The necessary distances between the switch contacts can therefore be used with a small Achieve displacement of the piston assembly so that the Actu only a small volume of pressure medium is needed. The switching device according to the invention has further the advantage that the transmission of the switching movement from the piston arrangement to the tappet in structurally more favorable Way between the pressurized faces of the Kol benanordnung occurs and the plunger no pressurization subject to.

According to one embodiment of the present invention provided that the plunger into one between the end faces of an annular piston protruding with a Caster tank with the brake system's caster tank connected is.

According to a further proposal of the invention, the Kon clock plate made of an insulating material and its contact surface  is coated with conductive material. For this training the contact plate does not require additional insulation in the Switchgear housing. According to another configuration device of the invention can also the lower portion of the plunger made of insulating material to make an electrically conductive Avoid connection to the piston assembly. But it can the contact plate itself must also be conductive.

According to the invention, the contact members form conductive contacts the switching device, these as quiescent current contacts are trained. But it is also possible to have a contact link not directly as a switch contact, but as an actuator to use for another switch. In in this case the contact member is spring-loaded against the contact plate can be pressed on and transmits the switching movement the contact plate to a resilient contact of a switch.

In a further embodiment of the invention, the Ram in its longitudinal direction with a transverse to the longitudinal axis running oblong hole into which a fixed with a Switch housing connected pin protrudes. In one end position of the plunger in which the spring pressed the plate against the two Presses contact links, the pin is in the bottom Part of the elongated hole. If the ram is swiveled, it will guide an evasive movement in the direction of the piston arrangement, wherein the conductive connection between the contact plate and a contact member is retained while the contact plate is lifted from the other contact member.

According to another embodiment of the invention, the Contact plate with its edges through the inner wall of a Switch housing led. This leadership takes the place of  Storage of the plunger using a pen and stands out through a particularly simple structure.

Preferably, the contact plate is also inside Switch housing arranged from which through an elongated hole End of the plunger sealed against the inside and two in an insulating plate inserted pins protrude, each with connected a contact member and abge on the plunger facing side of the switch housing are arranged. The Switching elements are in this embodiment of the invention protected against external influences.

Particularly favorable switching conditions can be fiction according to achieve that the distance between the centers the contact members is greater than the distance between the the end of the plunger and the plane which can be applied to the piston arrangement, in which the ends of the contact members lie. This will a small swivel movement of the ram into a larger one Swiveling movement of the contact plate translates so that the path the piston arrangement for opening the switching device in particular can be small.

For sealing the switch housing against the piston order can according to the invention a penetrated by the plunger and tightly against the tappet membrane, preferably made of Rubber, be provided covering the inside of the switch housing separates from the annulus and its edge by an insert in the Switch housing is clamped.

The invention is described below with reference to exemplary embodiments len explained in more detail, which are shown in the drawing.  Show it:

Fig. 1 is a circuit diagram of a hydraulic dual-circuit braking system for a motor vehicle with a partial longitudinal section through a braking pressure generator,

Fig. 2 is a Schaltvorrrichtung according to the invention in longitudinal section with an electrical switch,

Fig. 3 shows another embodiment of a switch in longitudinal section;

Fig. 4 shows the switching elements of the switch shown in Fig. 3 with the contact elements open and

Fig. 5 switching elements of the switch of FIG. 3 with reference to the dimensions relevant to the pivoting movement of a plunger and a plate.

A brake pressure sensor consists of a tandem main brake cylinder 1 and a vacuum booster 2 , which can be actuated by a brake pedal 3 .

The tandem master cylinder 1 shown in section has two separate working chambers 4 , 5 , which can be reduced by an actuation stroke of the master cylinder pistons 6 , 7 . The working chambers 4 , 5 can be connected via central valves 8 , 9 , which are open in the basic position shown, to trailing spaces 10 , 11 , which are connected to a pressureless trailing container 12 .

Brake lines 13 , 14 of two brake circuits lead from the working chambers 4 , 5 of the tandem master brake cylinder to de-energized open solenoid valves 15 , 16 of a brake slip control device, not shown, which are arranged in a valve block 17 . To the solenoid valves 15 , 16 , two brakes 18 and 19 are connected, of which one of the wheel brakes 18 and 19 is assigned to a front wheel of a vehicle and the other of the wheel brakes 18 and 19 is assigned to a rear wheel of the vehicle lying diagonally to the front wheel. It is therefore a dual-circuit braking system with a diagonal circle division.

The wheel brakes 18 and 19 are still connected to two de-energized closed solenoid valves 21 , 22 of the valve block 17 , the input side of which is connected via a return line 23 to the secondary tank 12 .

A pressure line 24 , 25 branches off from each brake line 13 , 14 . Each pressure line 24 , 25 leads to a separate check valve 26 , 27 which is closed in the basic position and which is likewise accommodated in the valve block 17 . The check valves 26 , 27 are arranged so that they only open to the pressure lines 24 , 25 out. From the check valves 26 , 27 leads a pressure line 28 to a pump unit 29 , which consists of an electric motor-driven pump 30 and a pressure valve 31 and which is connected via a suction line 32 to the container 12 .

In order to monitor the pressure in the pressure line 28 of the pump unit 29 , an electrical switching device 33 is provided, which is also arranged in the valve block 17 and which is connected to the pressure line 28 , the brake lines 13 , 14 and the return line 23 .

The switching device 33 shown in FIG. 2 in detail in a housing 34 in a stepped bore 35 has a stepped piston 36 and a separating piston 37 , which is located in the portion of smaller cross section of the stepped bore 35 . The stepped bore 35 is divided into pressure chambers 38 , 39 , 40 by the stepped piston 36 and the separating piston 37 . The pressure chamber 38 is located in the larger cross section of the stepped bore 35 and is connected to the pressure line 28 . The pressure chamber 39 is connected to the brake line 13 and the pressure chamber 40 to the brake line 14 . The stepped piston 36 and the separating piston 37 are each sealed with two spaced-apart sealing rings from the wall of the stepped bore 35 . Between the sealing rings, the stepped piston 36 has an annular space 41 and the separating piston has an annular space 42 . Both annular spaces 41 , 42 are connected to the return line 23 . In the annular space 41 , the stepped piston 36 is provided with an annular collar 43 which can be placed against the stepped surface 44 formed by the stepped bore 35 . With its shoulder facing away from the step surface 44 , the collar 43 serves to actuate a tappet 45 which projects radially into the annular space 41 through a bore.

The plunger 45 has a thickened section 46 , the end facing away from the annular space 41 is connected to a contact plate 47 . The contact plate 47 is preferably designed as a flat circular disk, the plunger 45 hitting the center of the circular disk perpendicularly. In section 46 there is an elongated hole 48 which extends in the longitudinal direction of the plunger 45 . A pin 49 projects into the elongated hole 48 and is connected to a round insert 50, which is located in a cavity 51 in the housing 34 . The insert 50 has a central passage for the plunger 45 . In the bottom of the cavity 51 there is a sealing membrane 53 which surrounds the tappet 45 and is clamped between the insert 50 and the wall of the cavity 51 . On both sides of the center of the contact plate 47 , two contact members 54 , 55 are arranged at a distance from one another in a plane running in the direction of the longitudinal axis of the stepped bore 35 . The contact members 54 , 55 contain pins 56 , 57 which are passed through a round plate 58 which covers the cavity 51 . From the plate 58 , the pins 56 , 57 are festgehal th. A biased compression spring 59 is supported on the insert 50 and on the contact plate 47 . The plate 58 is held in the switch housing 34 by a ring 60 . Because the insert 50 , the plate 58 and the ring 60 are round, a simple countersink in the housing 34 is sufficient to accommodate the switching device therein. The ring 60 can be caulked in the housing 34 in a simple manner.

The operation of the switching device described is the following:

In the basic position, for example when the brake is released, all components of the switching device 33 are in the position shown in FIG. 2. The annular collar 43 lies against the step surface 44 and is additionally held in this position by a pressure spring which acts on the step piston 46 and is arranged in the pressure chamber 38 . If the brake pressure transmitter is actuated, a pressure is built up in the brake lines 13 , 14 with the aid of the vacuum booster 2 and the tandem master brake cylinder 1 , which pressure also propagates into the pressure chambers 39 , 40 . The pump unit 29 is initially not switched on, because blocking of a wheel brake 18 , 19 cannot yet be determined. Since no back pressure is thus built up in the pressure chamber 38 , the stepped piston 36 is shifted to the left into the pressure chamber 38 until it abuts the bottom of the pressure chamber 38 . The movement of the stepped piston 36 is transmitted from the collar 43 to the plunger 45 , whereby the plunger 45 is pivoted about the pin 49 and the contact plate 47 is tilted. The contact plate 47 is held by the compression spring 59 in contact with the contact member 54 , while it is lifted against the force of the compression spring 59 from the contact member 55 . The plunger 45 translates together with the contact plate 47 the small displacement of the collar 43 in a sufficiently large distance between the contact member 55 and the contact plate 47 so that the monitoring circuit connected to the pins 56 , 57 is reliably broken under.

If the brake slip control device registers a tendency of a vehicle wheel to lock during a braking operation, the pump unit 29 is switched on so that it provides sufficient pressure medium for brake slip control. Since the check valves 26 , 27 are initially kept closed by the pressure present in the brake lines 13 , 14 , a high pressure builds up very quickly in the pressure line 28 and the pressure chamber 38 connected thereto, which in connection with the larger end face of the stepped piston 36 overcomes the pressure in the pressure chamber 39 and presses the stepped piston 36 with its annular collar 43 against the stepped surface 44 . Here, the plunger 45 is released again, so that the compression spring 59 moves the contact plate 47 back to its starting position, in which it conductively connects the contact members 54 , 55 to one another and closes the monitoring circuit. It can be seen in this process that the small path of the stepped piston 36 leads to a rapid response of the switching device 33 , since only a correspondingly small amount of pressure medium is required by the pressure medium pump 30 to carry out the switching process. As soon as the monitoring circuit is closed, the brake slip control process can be initiated by actuating the solenoid valves 15 , 16 , 21 , 22 . Falls during the brake slip control of the pressure in the pressure chamber 38 so far that the force caused by the pressurization of the pressure chambers 39 , 40 prevails force, the stepped piston 36 is again moved to the left and the switching device 33 opens ge. The interruption of the monitoring circuit now indicates an insufficient supply of pressure medium by the pump unit 29 and causes the brake slip control process to be terminated for safety reasons.

In the embodiment of the switching device 33 shown in FIG. 3, the contact plate 47 is guided instead of the pin 49 on an inner wall 61 of an insert 62 , which also serves to clamp the membrane 53 on the bottom of a scarf housing. In this embodiment, too, the contact plate 47 is pressed by the compression spring 59 against the contact element 54 , 55 . By pivoting the plunger 33 , the contact plate 47 executes a tilting movement around the contact member 54 .

Fig. 4 shows the tappet 45, the contact plate 47 and the contact members 54, 55, wherein the contact plate is in a tilted position 47. In the rest position, the compression spring 59 presses the contact plate 47 firmly against the two contact members 54 , ie a normally closed contact is closed. By the pivoting of the plunger 45 and the tilting movement of the contact plate 47, the connection between the contact member 55 and the contact plate 47 is interrupted, and it is formed between the contact plate 47 and the contact member 55, a gap 64th

In Fig. 5, the contact members 54 , 55 , the contact plate 47 and the plunger 45 in relation to the distances l ₁ and l _{2 are} Darge. With l ₁ , the distance between the end of the plunger 45 and a plane in which the ends of the con tact members 54 , 55 are located. The location of the contact member 54 , about which the contact plate 47 is pivoted, is marked with 65 be. With l ₂ , the distance between the contact points len of the contact members 54 , 55 with the contact plate 47 is distinguished.

The deflection of the plunger 45 and the size of the gap 64 are proportional to the ratio of l ₂ / l ₁ . The length l ₂ is preferably greater than the length l ₁ before. With the switching device described, the gap 64 necessary for the opening position of the switch at a certain switching voltage can be achieved by a relatively small displacement of the plunger 45 and a correspondingly small stroke of the stepped piston 36 . It follows that the volume of pressure medium required for actuating the tappet 45 can be very small. The scarf ter works as a toggle switch, ie only when a certain force acts on the plunger 45 , the bias of the compression spring 59 is exceeded and the switch is opened. The connecting pins 56 , 57 can, if necessary, also be designed as plug contacts or as soldering lugs.

The switching device described can not only in Bremsan layers were used. All of them are mechanical  sliding parts possible their movement in a scarf actuation should be implemented, e.g. the position of the mechanical part to monitor. By translating the Movement of parts into a larger movement at the switch contact is an adaptation of the contact distance to that for the the required clearance and creepage distance simple way possible.  

• Reference symbol list: 1 tandem master cylinder
  2 vacuum boosters
  3 brake pedal
  4 working chamber
  5 working chamber
  6 master cylinder pistons
  7 master cylinder pistons
  8 central valve
  9 central valve
  10 trailing space
  11 trailing space
  12 trailing containers
  13 brake line
  14 brake line
  15 solenoid valve
  16 solenoid valve
  17 valve block
  18 wheel brakes
  19 wheel brakes
  21 solenoid valve
  22 solenoid valve
  23 return line
  24 pressure line
  25 pressure line
  26 check valve
  27 check valve
  28 pressure line
  29 pump set
  30 pump
  31 pressure relief valve
  32 line
  33 electrical switching device
  34 housing
  35 stepped bore
  36 step pistons
  37 separating pistons
  38 pressure chamber
  39 pressure chamber
  40 pressure chamber
  41 annulus
  42 annulus
  43 ring collar
  44 step surface
  45 pestles
  46 section
  47 contact plate
  48 slot
  49 pen
  50 stakes
  51 cavity
  53 sealing membrane
  54 contact link
  55 contact link
  56 connector pin
  57 connector pin
  58 plate
  59 compression spring
  60 ring
  61 inner wall
  62 use
  63 -
  64 gap
  65 pivot point

Claims (9)

1. Electrical switching device for pressure monitoring in a hydraulic brake system for motor vehicles with a pressurized by the pressure in a brake line piston assembly and a movable by the piston assembly switching element, characterized in that a movement of the piston assembly ( 36 , 37 ) on a transverse to its longitudinal axis is attached ordered plunger ( 45 ) is transmitted, which at its end facing the piston assembly ( 36 , 37 ) carries a contact plate ( 47 ), which is supported by a spring ( 59 ) against two, spaced from each other, fixed contact members ( 54 , 55 ) can be pressed. 2. Switching device according to claim 1, characterized in that the plunger ( 33 ) projects into an annular space ( 41 ) arranged between the end faces of a piston ( 36 ) and is connected to the trailing reservoir ( 12 ) of the brake system. 3. Switching device according to claim 1 or claim 2, characterized in that the contact plate ( 47 ) consists of an insulating material and its contact surface is coated with a conductive material. 4. Switching device according to claim 1 or 2, characterized in that the plunger ( 45 ) consists entirely or partially of insulating material. 5. Switching device according to a preceding claim, characterized in that the plunger ( 45 ) is provided in its longitudinal direction with a transverse to the longitudinal axis elongated hole ( 48 ) into which a fixed to a switch housing ( 50 ) pin ( 49 ) protrudes . 6. Switching device according to one of claims 1 to 4, characterized in that the contact plate ( 47 ) with its edges on the inner wall ( 61 ) of a switch housing ( 62 , 63 ) is guided. 7. Switching device according to one of the preceding claims, characterized in that the contact plate ( 47 ) in the interior of a switch housing ( 50 , 62 , 63 ) is arranged, from which through an elongated hole one end of the plunger ( 45 ) sealed against the interior and two in an insulating plate ( 58 ) inserted pins ( 56 , 57 ) protrude, each with a contact member ( 54 , 55 ) and on the plunger ( 45 ) facing away from the switch housing ( 50 , 62 , 63 ) are arranged. 8. Switching device according to one of the preceding claims, characterized in that the distance ( l ₂ ) between the centers of the contact members ( 54 , 55 ) is greater than the distance ( l ₁ ) between the end of the plunger ( 45 ) which can be placed on the piston arrangement ( 36 ) ) and the plane in which the ends of the contact members ( 54 , 55 ) lie. 9. Switching device according to one of the preceding claims, characterized in that one of the plunger ( 45 ) by penetrating and sealed against the plunger ( 45 ) sealed membrane ( 53 ), preferably made of rubber, is provided, which the interior of the switch housing ( 50 , 62 , 63 ) from the annular space ( 41 ) and the edge of which is clamped in the switch housing ( 63 ) by an insert ( 50 , 62 ).