DE3736059A1 - HYDRAULIC AMPLIFIER FOR A MOTOR VEHICLE BRAKE SYSTEM AND AN ANTI-BLOCKED HYDRAULIC BRAKE SYSTEM WITH SUCH AN AMPLIFIER - Google Patents

Abstract

A hydraulic booster with a reduced response force is demonstrated. This is achieved in that the pressure medium is fed by way of the tappet (4), which is led through a wall (5) forming a seal. The diameter of the tappet (4) may be designed very small, so that the pressure acting on the ring seals (15, 15') can be kept significantly lower than is possible in the prior art. <IMAGE>

Description

The invention relates to a hydraulic Amplifier for a motor vehicle brake system with a Booster piston that delimits a booster chamber, a brake pressure control valve, the control part of an actuating force and relative to Booster piston is movable, depending on the position control unit / booster piston the connection the amplifier room either to a storage container or is manufactured to a pressure medium source, and an annular space on the outer edge of the booster piston in the Connection of pressure medium source / brake pressure control valve, the is sealed by means of sealing rings.

Such amplifiers have already been described in large numbers been. At this point, only that DE-OS 24 61 295 called. The booster piston points an annulus on its outer edge, which with the Pressure source is directly connected. This Annulus is over a radial bore with one central bore in the booster piston connected. In the A spool is guided in the central bore. The Control spool also has holes, so are arranged that with a relative movement Control spool / booster piston connecting the Amplifier room, which, seen in the direction of actuation,  is arranged in front of the booster piston with which Storage container interrupted and the connection to Annulus is made. To operate the The amplifier is the control spool in the above Senses actuated so that pressure medium from the Pressure medium source can flow into the amplifier room. This creates a pressure on the Booster piston works and this in the sense of a Actuation of a brake master cylinder moves. The Control spool also has a pressurized Surface on so that one counteracts the braking force Force is generated.

Such constructions have a decisive one Disadvantage on. The sealing rings that make up the annulus seal, are from the pressure of the pressure medium source acted upon. You will be against the walls of the Amplifier housing pressed and generate in this way a high frictional force caused by the pressure in the amplifier room must be compensated. This does particularly disadvantageous at the start of braking noticeable: The brake pressure control valve turns on Pressure built up in the amplifier room, which at the same time creates a retroactive force on the push rod. The pressure is not enough, the frictional forces to overcome that of the pressurized Run out of sealing rings. There is therefore no Actuation of the master brake cylinder, although for the The driver feels a back force on the pedal. This means that there is no clear connection between the Brake pressure and the retroactive force on the pedal.

The invention is therefore based on the object Construct an amplifier where the frictional forces, that attack the booster piston are minimized.

The problem is solved in that the Booster piston has an area whose Cross section is smaller than the cross section of the End face of the booster piston to the booster chamber, that this area seals through the longitudinal bore of a Wall is guided.

This solution still has pressurization Seals are provided, and will continue to be Frictional forces occur, but these are clear reduced because the sealing rings due to this measure be significantly reduced. The size of the Frictional force depends linearly on the scope of the pressure-loaded sealing rings, so that a clear Minimization of the frictional forces can be achieved. The Pressurizing surface of the booster piston can become arbitrarily large or optimal to the Boundary conditions caused by the dimensioning of the Pressure medium source and the forces to be applied is determined to be adjusted.

The area of smaller diameter can in principle can be chosen arbitrarily small. There may be Strength criteria to be considered.

A particularly cheap and compact embodiment is obtained if the area has a smaller cross section than Tappet is formed on the from the amplifier room  opposite side of the booster piston is formed and which can be applied to the organ to be operated.

The pressure medium is supplied in a known manner an annulus in the wall that the pestle penetrates, is formed. The wall can be used as Insert piece are formed, in which the Amplifier housing can be used.

This type of pressure medium supply can also realize a simple brake pressure control valve. It consists of a sleeve that is operated with the foot power Push rod communicates and seals over one Extension is guided on the booster piston. The process has ring channels that with the reservoir and the pressure source.

The amplifier can be advantageously in one Use brake system with brake slip control, one Pedal reset during brake slip control makes necessary. This happens in a surprising way simple way that the amplifier room to the Space between the wall and the booster piston in the case of a Slip control is connected. These rooms are supposed to have essentially the same cross section. Now there is a connection between these two Broach, so is the booster piston, based on the Forces acting on its end faces pressure balanced. It now acts as a driving force Pressure in the master cylinder, which on the push rod piston acts.  

Since there is no force on the master brake cylinder from the amplifier is transferred, the pistons of the Master brake cylinders in their basic positions deferred. The booster piston and that Brake pedal reset. At the same time Pressure medium from the booster room to the reset room promoted. But it is only one Exchange of pressure medium, since, as I said, the aforementioned Rooms have essentially the same cross-sections. This means that no additional pressure medium for Resetting the amplifier is necessary. The The pressure medium source can therefore possibly be low Funding services or lower storage capacities be equipped so that a Reduction is achieved.

It is also advantageous if in the connection mentioned between the reset room and the amplifier room Throttle is switched on. That way achieved that the pressure medium supply to the recovery room damped and the pedal is slow is deferred.

A too violent reset of the pedal could Driver get confused and cause him to brake to solve.

An exemplary embodiment is described below with reference to the figure . The idea of the invention is thus intended to be described again without any restriction to this exemplary embodiment being provided.

The figure shows the amplifier 1 according to the invention within a brake system with brake slip control. The amplifier can also be used in other areas. The use within a brake slip control system, as will be described below, has certain advantages.

The hydraulic booster 1 consists of a housing 2 in which an booster piston is inserted in a bore. The end faces of the booster piston 3 each delimit a room, namely the booster room 27 and the reset room 11 . At the end face, facing the return chamber 11, a plunger is integrally formed, which projects through a wall 5, and for example, can be applied to the push rod piston 32 of a master cylinder 30th An extension 6 is provided on the other end face of the booster piston 3 , which projects into the booster chamber 27 .

This extension is encompassed by a sleeve 7 which is fastened to the push rod 8 by means of a snap ring 9 . The push rod 8 can be pushed into the amplifier by means of a pedal, not shown. Furthermore, a stop 10 is provided which defines the basic position of the booster piston 3 .

Between the wall 5 and the booster piston 3 , a recovery space 11 is formed, which is connected to the reservoir 12 .

As part of a brake slip control, another can  Circuit provided on the below is received.

The pressure medium is supplied from the pressure medium source 23 via the wall 5 . For this purpose, the wall has an annular space 14 which is adjacent to the plunger 4 and is sealed with the aid of two seals 15 , 15 'on the one hand against the recovery space 11 and on the other hand against an intermediate space 16 . A radial bore 13 leads from the annular space 14 to an external connection to which the pressure medium source is coupled.

The tappet 4 has a first channel 18 and a second channel 20 , the first channel leading from the annular space 14 to a first annular groove 19 on the outer edge of the extension 6 . The second pressure medium channel 20 leads from the recovery space 11 to a second ring channel 21 , which is also formed on the outer edge of the extension 6 . The extension 6 forms, together with the sleeve 7 surrounding it, the pressure control valve.

In the illustrated release position, the annular groove 21 is connected to the booster chamber 27 , while the first annular groove 19 is covered by the sleeve, so that the connection between the pressure medium source 23 and the booster chamber 27 is interrupted.

There is a distance x between the extension 6 and the push rod 8 , the space formed there being in constant communication with the amplifier space 27 .

Furthermore, the sleeve has a radial bore 22 which can be brought into overlap with the first annular groove 19 , so that a connection between the pressure medium source 23 and the booster chamber 27 can be established.

The pressure medium source 23 itself consists of a pump 24 which conveys into a memory 25 via a check valve 26 . This in turn is connected to the annular space 14 via a pressure line 48 .

Before going into the brake system further, First, the mode of operation of the amplifier to be discribed.

In the release position, all parts are in the position shown in the figure . The storage pressure is in the annular space 14 and loads the sealing rings 15 , 15 '. Storage pressure also prevails in the pressure medium channel 18 and in the annular groove 19 . However, the pressure medium cannot flow into the booster chamber 27 since the sleeve 7 surrounds the extension 6 in a sealing manner.

Low leakage currents cannot be avoided, but can be disregarded when considering the system in principle. The annular groove 21 is not yet covered by the sleeve, so that a pressure medium path by means of the channel 20 from the booster chamber 27 to the reset chamber 11 exists, which is connected to the reservoir 12 via a permanent pressure medium line 44 .

To actuate the amplifier, the push rod 8 is pushed to the left in the illustration according to the FIG . The sleeve slides over the annular groove 21 , whereby the pressure medium connection from the booster chamber 27 to the reservoir 12 is interrupted. Upon further actuation of the bore 22 engages the annular groove 19 for covering, by which pressure medium from the pressure medium source 23 via the line 48 the radial bore 13, the annular space 14, the channel can enter the booster chamber 27 eighteenth A pressure builds up there, which acts on the one hand on the booster piston 3 and on the push rod 8 . The pressure in the booster chamber 27 acts on the booster piston, whereby it is pushed to the left and, for example, a brake master cylinder 30 is acted upon by force. The retroactive force on the push rod 8 is determined by the actuating force: This means that the pressure in the booster chamber is essentially proportional to the foot force.

Since the booster piston moves to the left as a result of the pressurization, the annular groove 19 no longer remains in register with the bore 22 , so that the pressure build-up is interrupted. A further pressure build-up can only take place if the push rod is pushed further into the booster chamber by the actuating force and follows the movement of the booster piston 3 .

In principle, the effect mentioned in the introduction to the description will also occur with this amplifier. The seals 15 , 15 'are constantly under pressure and are pressed against the tappet 4 . The pressure force on the booster piston must therefore overcome the frictional forces before the booster piston 3 can be set in motion. A minimum pressure must therefore be introduced into the booster chamber 27 before a force can be applied to the organ to be actuated. These frictional forces can, however, be kept very small due to the construction, since the plunger 4 can have an almost arbitrarily small diameter, which is only determined by the size of the forces to be transmitted. Since the plunger is mounted at two points apart, namely through the seals 15 , 15 ', high stability results. The smaller the diameter of the tappet, the smaller the circumference of the sealing rings. The circumference of the seals directly determines the friction force, since the pressure surfaces are linearly determined by the circumference. It is readily apparent that at the same pressures on the sealing rings 15 , 15 ', a smaller frictional force occurs with a smaller contact surface. In addition, the booster piston 3 can now have a relatively large diameter, so that the pressure level of the pressure medium source can be kept small and a sufficient boosting force can nevertheless be generated. This is not possible with the amplifier according to the prior art. The pressure on the seals would be reduced, but at the same time the circumference and thus the area under pressure would become larger, so that the frictional forces remained constant in principle.

This amplifier has yet another advantage, which becomes apparent when you see its use in a brake system with slip control. The brake system consists of a master brake cylinder 30 and the hydraulic booster 1 already described. The master brake cylinder 30 consists of a housing 31 which is flanged to the booster housing 3 . In the housing there is a floating piston 33 and a push rod piston 32 , which are held by return springs 34 , 34 'in their release position. Furthermore, in the pistons 32 , 33 central valves 35 , 35 'are arranged, which are open in the brake release position, so that a pressure medium connection between the respective working space and an annular space 36 , 36 ' or prechamber is made. This annular space 36 , 36 'is connected via a line 43 to a main valve 41 , which in its position I connects the line 43 to the reservoir 12 and in its position II to the amplifier chamber 27 .

When the pistons are moved from their brake release position, the central valves 35 , 35 'close, so that a braking pressure can be built up in the working spaces in front of the pistons 32 , 33 . This pressure is passed via brake lines 47 , 47 'to the wheel brakes, a valve block 40 being switched on in these brake lines, in which the valves are controlled by a brake slip control device, not shown. The brake slip control does not need to be explained further, it should only be pointed out that a connection to the work spaces is established to build up pressure and a connection to the relief line 46 , which is connected to the reservoir 12 , to reduce the pressure. This makes it necessary to adjust the pressure medium in the event of a slip control.

Furthermore, the already mentioned main valve 41 is provided, which has two switching positions I and II. In switch position I, the already mentioned annular spaces 36 , 36 'are connected to the reservoir 12 , and the recovery space 11 of the hydraulic amplifier 1 is connected to the reservoir. For brake slip control, the main valve 11 is switched to its switching position II. Then there is a pressure medium connection between the booster chamber 27 and the annular spaces 36 , 36 '.

The reset space 11 is also decoupled from the reservoir 12 and is now connected to the booster space 27 via a throttle 42 .

Two cases can now be distinguished. This is on the one hand the conventional and on the other hand the slip-controlled braking.

Conventional braking works as follows. To actuate the brake, the pedal (not shown) is depressed and the amplifier 1 is activated. In the manner already described, the booster piston 1 moves to the left and takes the push rod piston 32 with it. The central valve 35 closes and a pressure builds up in the space in front of the push rod piston 32 , which acts on the floating piston. This piston also shifts in the actuation direction, as a result of which the central valve 35 closes and a pressure is also built up in the space in front of the floating piston 33 . The pressures in the master brake cylinders are transmitted to the connected wheel brakes via the brake lines 47 , 47 '.

In a conventional braking, the main valve 41 is in the switching position I, whereby the annular spaces 36 , 36 'and the reset space 11 are connected to the reservoir 12 . The pressure medium from the reserve room is conveyed into the reservoir without additional effort. The following conditions must be met for brake slip control. First, it must be ensured that the pressure medium discharged from the wheel brakes can be refilled from the pressure medium source 23 . On the other hand, the pistons of the master brake cylinder have to be reset so far that a reserve volume is formed in the work area which is sufficient to be able to initiate sufficient emergency braking in the event of a failure of the brake slip control.

This is achieved in that the main valve from the Switch position I switches to switch position II.

As a result, the annular spaces 36 , 36 'are first separated from the reservoir 12 and connected to the amplifier space 27 . This means that pressure medium flows from the pressure medium source 23 via the brake pressure control valve into the booster chamber 27 and from there to the annular spaces 36 , 36 '. There it flows through the sleeves on the working piston into the working areas in front of the piston and thus to the wheel brakes. In the switching position 2 of the main valve 41 , however, the reset space 11 is also separated from the reservoir 12 and connected to the booster space 27 via a throttle 42 . Pressure medium thus flows not only to the wheel brakes, but also into the reset space 11 , as a result of which there is an excess of forces due to the pressure in the master cylinder in the direction of the brake release position. The booster piston and the pistons 32 , 33 no longer loaded move into their release position. The throttle 42 has the effect that the supply of pressure medium is throttled into the return space 11 , so that the return movement is slow and not jerky. The main valve 41 can be of simple design, in particular in that the throttle is connected between the lines 44 and 43 .

Since the volume of the resetting space 11 and the booster space 27 is changed to approximately the same extent, no additional pressure medium is required for the resetting.

In principle, the effective diameter of the reset space 11 can be chosen larger than the effective diameter of the amplifier space 27 . The result of this is that additional forces are available for resetting the pedal; on the other hand, when the pedal is reset, the booster is compressed. Advantages and disadvantages of dimensioning the amplifier room and the reset room must be weighed by the designer.

Reference symbol list:

1 hydraulic booster
2 housings
3 booster pistons
4 pestles
5 wall
6 extension
7 sleeve
8 push rod
9 snap ring
10 stop
11 storage room
12 storage containers
13 radial bore
14 annulus
15, 15 'seals
16 space
17 longitudinal bore
18 first channel
19 first ring groove
20 second channel
21 second ring groove
22 radial bore
23 pressure medium source
24 pump
25 memory
26 check valve
27 amplifier room
30 master brake cylinders
31 housing
32 push rod pistons
33 floating pistons
34, 34 'return springs
35, 35 ′ central valves
36, 36 ′ annular spaces / antechambers
40 valve block
41 main valve
42 throttle
43 pressure medium line
44 pressure medium line
45 cross line
46 Discharge line
47, 47 ′ brake line
48 pressure line
x distance
I, II switching positions of the main valve 41

Claims (16)

1. Hydraulic booster ( 1 ) for a motor vehicle brake system with an booster piston ( 3 ) which delimits an booster chamber ( 27 ), a brake pressure control valve, the control part ( 7 ) of which can be acted upon by an actuating force and can be moved relative to the booster piston ( 3 ), depending on from the position of the control part ( 7 ) / booster piston ( 3 ) the connection of the booster chamber ( 27 ) to either a reservoir ( 12 ) or to a pressure medium source ( 23 ) is established, and an annular space ( 14 ) on the outer edge of the booster piston ( 3 ) in the connection of pressure medium source ( 23 ) / brake pressure control valve, which is sealed by means of sealing rings ( 15 , 15 ′), characterized in that the booster piston ( 3 ) has a region (plunger 4 ) whose cross section is smaller than the cross section of the end face of the booster piston ( 3 ) to the amplifier room ( 27 ) and that this area ( 4 ) sealingly through the longitudinal bore ( 17 ) of a wall ( 5 ) is. 2. Amplifier according to claim 1, characterized in that the region of smaller cross-section ( 4 ) on the amplifier chamber ( 27 ) facing away from the amplifier piston ( 3 ) is formed. 3. Amplifier according to claim 2, characterized in that the area of smaller cross-section ( 4 ) can be applied to the organ ( 30 ) to be actuated. 4. Amplifier according to claim 1, characterized in that an annular space ( 14 ) is formed on the longitudinal bore ( 17 ) of the wall ( 5 ), which is sealed by means of two ring seals ( 15 , 15 ') and on the booster piston ( 3 , 4th ) adjoins. 5. Amplifier according to claim 4, characterized in that the annular space ( 14 ) by means of a radial bore ( 13 ) with the pressure medium source ( 23 ) is in communication. 6. Amplifier according to claim 1, characterized in that the wall ( 5 ) in the amplifier housing ( 2 ) can be used. 7. Amplifier according to claim 1, characterized in that the space ( 11 ) between the wall ( 5 ) and the booster piston ( 3 ) is in communication with the reservoir ( 12 ). 8. Amplifier according to one of the preceding claims, characterized in that a push rod acted upon by the actuating force projects into the booster chamber and is formed in the booster chamber ( 27 ) as a sleeve ( 7 ) which sealingly engages around an extension ( 6 ) of the booster piston ( 3 ) . 9. Amplifier according to claim 8, characterized in that the push rod ( 8 ) and the extension ( 6 ) maintain a distance ( x ) in the brake release position. 10. Amplifier according to claim 8, characterized in that the extension ( 6 ) has two outer annular grooves ( 19 , 21 ), the first annular groove ( 19 ) being connected to a first channel ( 18 ) which is in the annular space ( 14 ) opens, and the second annular groove ( 21 ) is connected to a channel ( 20 ) which opens into the reset space ( 11 ). 11. Amplifier according to claim 10, characterized in that the second annular groove ( 21 ) by means of the sleeve ( 7 ) can be hidden and the first annular groove ( 19 ) by means of a bore ( 22 ) in the sleeve ( 7 ) with the amplifier space ( 27 ) in Connection can be made. 12. Amplifier according to one of the preceding claims, characterized in that the sleeve ( 7 ) is fastened to the push rod ( 8 ) by means of a snap ring ( 9 ). 13. An anti-lock hydraulic brake system with a master cylinder, an amplifier upstream of the master cylinder, with pressure modulation valves that are connected to the brake lines between the master cylinder and the wheel brake cylinders, with a master valve that can be used to establish a connection between the booster chamber and the working spaces of the master brake cylinder, characterized in that the hydraulic amplifier is designed according to one of claims 1 to 12, and in that the resetting space ( 11 ) can be separated from the reservoir ( 12 ) by means of a valve ( 41 ) and can be connected to the amplifier space via a throttle ( 42 ). 14. Brake system according to claim 13, characterized in that the throttle between the reset space ( 11 ) and antechambers ( 36 , 36 ') is connected to the master brake cylinder. 15. Braking system according to claim 14, characterized in that by means of a 4/2-way valve either the connection of the antechambers ( 36 , 36 ') and the reset chamber ( 11 ) to the reservoir ( 12 ) or the connection of the amplifier chamber ( 27 ) the antechambers ( 36 , 36 ') can be produced. 16. Brake system according to claim 14, characterized  characterized that the throttle is adjustable.