JPS6366701B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-medium actuated multi-system brake for motor vehicles, of the type equipped with an anti-lock device for maintaining the brake pressure within wheel lock limits.

A brake of this type is known from DE 27 02 819 A1.

In the above-mentioned type of brake system, problems to be solved include boosting the brake force using a brake force booster, adjusting the brake force using a pressure reducing device or pressure limiting device or brake force adjustment mechanism, and controlling the brake force using an anti-lock device. is left behind. A large number of different types of brake force boosters are already known.

Regarding the problem of braking force adjustment, gradually
Brake systems having a brake pressure limiting device that limits the distribution of brake pressure to the rear brake cylinders relative to the front brake cylinders have come into use, and such brake pressure limiting devices have a negative effect on vehicle deceleration. It is something that works by doing so. Brake systems with such pressure limiting devices have, on the one hand, become almost indispensable in vehicles with large fluctuations in the rear axle load, for example front-drive motor vehicles and lorries. Generally, when braking, the vehicle enters a so-called nose-down state, and the load on the rear axle rapidly decreases, causing the rear axle to lose grip on the road surface and become more likely to lock up.
A locked rear axle creates a much more dangerous driving situation than a locked front axle. This is because if the front wheels are locked, the vehicle will still skid in a straight line, but if the rear wheels are locked and the road blip is lost, the vehicle will rotate around the yaw axis, causing a skid. It is from.

On the other hand, however, there is a need to increase the braking force to reduce wear on the brake linings, in other words, to reduce the frequency of brake lining replacement. For this reason, the rear wheels are braked more strongly, especially in normal so-called partial braking in which the wheel lock limit is not exceeded.

However, if the brake system is configured so that the rear wheels are strongly braked, especially during partial braking without exceeding the wheel lock limit,
When the deceleration of the vehicle is relatively high, i.e. when the load on the rear axle is suddenly and significantly reduced, there is a risk that the rear wheels will lock in front of the front wheels, which can be dangerous as described above. A running condition occurs.

Basically, when adjusting the brake circuit, efforts are made to ensure that the front wheels are locked before the rear wheels. However, the functionality of the pressure reducers or pressure limiters used in some cases today has serious deficiencies in the event of a failure of the front wheel brake circuit. In other words, in this case, only the rear brake circuit is working, but if a pressure reducing device or pressure limiting device is used in this circuit, significantly higher brake pressure (large pedal force) may be required to compensate for the reduced pressure. ) must be used for braking.
However, it is often difficult for the driver to apply such brake pressure.

Some automobiles with anti-lock systems do not have such pressure reducing or limiting devices. However, even in this case, there are still problems in the following two points.

1. If the brake force adjustment mechanism is designed to apply a desired relatively strong braking force to the rear wheels, such a configuration is extremely problematic in the event of a failure of the antilock device;
In this case, the result is that the rear axle is braked too strongly.

2. If the rear wheels are braked relatively strongly, driving stability will be impaired, which means that if the deceleration is relatively high, the front wheels will be braked even though the rear wheels are already within the range that should be antilock controlled. yields a result that is not yet within this range. This means that the rear wheels experience higher braking slip than the front wheels. Driving stability is at risk in these ranges, especially when braking from relatively high-speed driving situations.

In the pressure medium actuated multi-system brake of the present invention having the features set forth in claim 1,
Within the lock limits, where the anti-lock device is not activated, the pressure limiting device is switched into the activated or deactivated position in relation to the deceleration of the vehicle in question, so that when the pressure limiting device is activated, the brake pressure on the rear wheels is reduced. When the pressure limiting device is not activated, that is, during normal partial braking without exceeding the locking limit, strong braking of the rear wheels is possible. Additionally, during antilock activation, the pressure limiting device is switched completely to the inactive position.

This provides the following advantages:

That is, by increasing the braking force of the rear wheels in the normal partial braking range, wear on the brake pads is reduced. Also, in the event of a failure of the antilock device, at the lock limit, the risk of rear wheel locking is reduced by activation of the pressure limiting device. Furthermore, when mechanical-hydraulic braking means are employed, the braking function is ensured without the action of a brake force booster, ie, independently of the supply of electric power.

According to yet another configuration of the present invention, the configuration of the hydraulic brake force booster allows the transmission ratio of brake pressure to the rear wheels to be changed. That is, it is possible to generate a higher brake pressure in the rear wheel brake circuit than in the front wheel brake circuit. Pressure transmission at this transmission ratio will not work if the servo pressure supply system of the hydraulic brake force booster malfunctions.
You can prevent it from happening.

Particularly low manufacturing costs can be achieved by integrating the above-mentioned pressure limiting device in a hydraulic brake force booster or in a pressure control valve of an antilock device or by manufacturing it in one piece.

The invention will now be explained with reference to the illustrated embodiment.

A hydraulic brake force booster 1 is arranged between a brake pedal 2 and a pair of front brake cylinders 3, 3' and a separate rear brake cylinder 4, 4'. A pair of front brake cylinders 3,
3' belongs to the brake circuit, and the other two rear brake cylinders 4, 4' each separately belong to a part of the brake circuit.

For boosting the brake force, a pressure source consisting of a pump 6 and a pressure accumulator 7 is used, which is connected to the housing 8 of the brake force booster 1 . In the casing 8 there are three main parallel holes 9,1
0, 11 are provided, of which two holes 9, 10 serve as two master cylinders 90, 100. Between the two master cylinders 90, 100 there is a bore 11 which receives a control valve 110 made as a slide valve.

The slide 12 of the control valve 110 projects from the casing 8 at one end, and in this projection a stroke spring 15 and a guide tube 17 made as a tube body are connected.
It is coupled to the brake pedal 2 via. The guide tube 17 has two arms 19, 20,
Two protruding rods 21 and 22 face each other at these ends, and these protruding rods are connected to the master cylinder 9.
0,100 and support one master cylinder piston 23, 24, respectively.

There is one pressure chamber 25, 26 on the opposite side of each piston 23, 24 from the protruding rods 21, 22 side (left side in the drawing), one of which 26 is connected to the brake circuit via a passage 27. One 25 is passage 28
Connected to the brake circuit via. The brake circuit is a front wheel brake circuit, and the brake circuit is a rear wheel brake circuit. control slide 1
2 (to the left in the figure) is a locking piston 29 which limits the travel of the travel spring 15 when supplying pressure medium.

On the outer wall of the guide tube 17, which is located at the center between the axes of both master cylinders 90 and 100, there is a swing fulcrum 30 of a lever 31 that can swing like a seesaw. Arms 32, 33
(lengths L ₁ , L ₂ ). Arms 32, 33
are in contact with the free side ends of the protruding rods 21 and 22 having the flanges 34 and 35, and each of the flanges 34 and 3
5 and the housing 8 are arranged return springs 36, 37, which surround the rods 21, 22, for the master cylinder pistons 23, 24 which are connected to the rods 21,22.

In this embodiment, the pressure limiting device 49 is the control valve 11
0 and the servo pressure chamber 42 on the right side of the figure of the master cylinder piston 24, which is loaded with servo pressure, into a conduit 50 leading to the rear brake cylinders 4, 4', However, it is also possible to connect the master cylinder pistons 23, 24 in a conduit between the brake pressure chambers 25, 26 on the side opposite to the servo pressure chambers 41, 42 and the rear brake cylinders 4, 4'. (Second
figure).

The general working style of brake force boosters is described in the Federal Republic of Germany Patent Application Publication No.
It is described in the specification of No. 2702819. Lever 31
serves only as an emergency braking mechanism in case of failure of the servo pressure supply system by the hydraulic brake force booster. In this case, the guide tube 17 is pushed to the left side in the drawing by the force of pressing the pedal 2, and as a result, the arms 32 and 33 of the lever 31 are
1, 22, master cylinder piston 23,
24 to the left in the drawing to create brake pressure in the wheel brake cylinders 3, 3'; 4, 4'.
The lever 33 operates as a beam that swings like a seesaw body, and transfers the pedal depression force to the two protruding rods 21 and 22.
The pressure is distributed so that approximately equal pressure is generated in both brake circuits. Arm 1 of guide tube 17
9 and 20 support the levers 32 and 33 when the guide tube 17 is pushed to the left in the drawing as described above and the levers 32 and 33 push the protruding rods 21 and 22. The connection passage 40 from the control valve 110 to the servo pressure chambers 41, 42 of the master cylinder pistons 23, 24 has three
There is a port 2-position directional control valve 43, which is controlled via a 3-port 2-position directional control solenoid valve 44. The brake pressure chambers 25 and 26 of the master cylinder pistons 23 and 24 on the opposite side from the servo pressure chambers 41 and 42 include a 2-port 2-position directional control valve 45,
46 and 47 are arranged, and these have a pressure holding function. Valves 43, 44, 45, 46 and 4
7 is a component of an antilock device 48, which is assigned to a wheel speed sensor (not shown) and an electronic control circuit (also not shown). In a simple form, a pressure limiting device 49 having a ball 49' as an inertial mass is connected in a conduit 50 coming from the servo pressure chamber 42 and leading to the rear brake cylinders 4, 4'. ing. Instead of this simple pressure limiting device 49, it is also possible to use a switching valve which closes at a certain predetermined pressure. It is also possible to use a so-called pressure reducing device which operates at a set switching pressure, although this involves an increase in manufacturing costs.

In the illustrated embodiment, when a predetermined inertial force acts on the ball 49' in connection with the deceleration of the vehicle, the ball 49'
contacts the seat 51 and closes the passage. As a result, the supply of servo pressure medium from the servo pressure chamber 42 into the brake cylinders 4, 4' is cut off, and the pressure no longer increases. However, this pressure limiting device 49 is activated only if the antilock device is not activated.

A pressure limiting device 49 operating in conjunction with the deceleration is combined with a regulator 52 operated by pressure medium, which regulator 52 has a rod 53, which extends in the area of the ball 49'. You can reach inside. When the anti-lock device is activated, the anti-lock signal activates the 3-port 2-position directional control solenoid valve 4.
4 is switched and the protrusion 53 moves upwards in conjunction with the pressure, lifting the ball 49' from its seat 51. This opens the passage again, so that the pressure in the rear brake cylinders 4, 4' is reduced to the antilock device 4.
8.

Pressure limiting device 49 is shown enlarged in FIG. As can be seen from this figure, a locking piston 54 is also associated with the rod 53, which receives the pressure of the servo pressure chamber 42 supplied to the connection 56 against the force of a spring 55. The seat 51 forms the beginning of the brake conduit leading to the rear brake cylinders 4, 4'. The protruding rod 53 is operated by a switching piston 58, which has three ports 2 which are switched by an anti-lock signal.
It receives pressure supplied via a position and direction control solenoid valve 44. Furthermore, the rod 53 has a radial projection 57, on which a locking piston 54 normally rests.

When a certain brake pressure is built up in the rear brake circuit, the locking piston 54 moves upwards against the force of the spring 55 even after a slight pressure increase. This releases the protruding rod 53, but it does not operate. As a result, braking takes place without the action of the pressure limiting device 49. Furthermore, when the pressure limiting device 49 is activated in connection with vehicle deceleration, the braking pressure is thereby limited. When the anti-lock device is activated, the anti-lock signal switches the 3-port 2-position directional control solenoid valve 44, and a control pressure PST is applied to the lower side of the switching piston 58, thereby causing the switching piston 58 to reach the set reference pressure P _RZ. As a result, the protruding rod 53 is pushed up against the
When the ball 49' is placed on the seat 51,
Release the ball 49' from the seat 51. This deactivates the pressure limiting device 49 and releases its pressure limiting function.

It is also possible to configure the above-mentioned operating mechanism to be bistable, that is, so that the first control holds the protruding rod 53 in its switching position. In this case, the bar is returned to its starting position only when the pressure in the conduit 50 has reached zero, ie when the braking process has ended. Instead of the locking piston 54, it is also possible to use the pressure difference that occurs during activation of the antilock device between the control valve pressure and the regulated wheel brake cylinder pressure. This measure is particularly advantageous in the case of antilock devices for pneumatic brake systems.

In the illustrated embodiment, the system is hydraulically boosted with an area ratio F
:FO and F:FO are designed so that more pressure is transmitted to the brake circuit than to the brake circuit. Pressure transmission at this transmission ratio does not occur when servo pressure supply is not performed due to a failure of the hydraulic booster system. In this case, the pedal force is mechanically transmitted to both master brake cylinder pistons 23, 24 via the arms 32, 33 of the lever 31, as described above. In this case, due to the lever 33 swinging like a seesaw around the swing fulcrum 31 and its corresponding lever ratio L1:L2, approximately equal brake pressures are generated in both brake circuits.

It is also possible to integrate the pressure limiting device directly into the brake booster or anti-lock device 48 in order to save space and eliminate trouble-prone conduits and seals.

The embodiment shown in Fig. 2 relates to a diagonal type two-system brake in which the brake circuit is divided diagonally, and parts corresponding to those of the embodiment shown in Fig. 1 are given the same reference numerals. There is. In such a brake circuit, the rear wheel brake circuit is adjusted using the so-called "select low method".
Prinzip) via a common regulator 25. The solenoid valve 60 has a pilot control function and controls the corresponding brake circuit and the internal two-port two-position directional control valves 61,62. In this system configuration, there are two different brake circuits for the rear wheels, so each brake circuit,
In each case, a separate pressure limiting device 63, 64 is required in the branch line which branches off from the respective rear brake cylinders 4, 4'. The working style is the same as that of the embodiment shown in FIG.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 shows a conventional type of pressure medium operated multi-system brake, FIG. 2 shows a similar type of pressure medium operated multi-system brake, FIG. 3 is a diagram showing a switching device of a pressure limiting device of a pressure medium operated brake system. 1... Brake force booster, 2... Brake pedal, 3, 3'... Front wheel brake cylinder, 4,
4'...Rear brake cylinder, 6...Pump,
7... Pressure accumulator, 8... Casing, 9, 10, 1
1... Hole, 12... Slide, 15... Stroke spring, 17... Guide tube, 19, 20... Arm, 2
1, 22... Protrusion rod, 23, 24... Master cylinder piston, 25, 26... Brake pressure chamber, 2
7, 28... Passage, 29... Lock piston, 3
0... Swinging fulcrum, 31... Lever, 32, 33...
...Arm, 41, 42...Servo pressure chamber, 43...
...3 port 2 position directional control valve, 44...3 port 2 position directional control solenoid valve, 45, 46, 47...2
Port 2 position solenoid valve, 48... Anti-lock device, 49... Pressure limiting device, 49'... Ball, 50
... Conduit, 51 ... Seat, 52 ... Regulator, 53 ...
... protrusion rod, 54 ... lock piston, 55 ... spring, 56 ... connection section, 58 ... switching piston, 6
1,62...2 port 2 position directional control valve, 63,
64...Pressure limiting device, 90...Master cylinder, 100...Master cylinder, 110...Control valve.

Claims (1)

[Scope of Claims] 1. In a pressure medium-operated multi-system brake for an automobile, which is equipped with an anti-lock device that maintains the brake pressure within the wheel lock limit, pressure limiting devices 49, 63, 64 that limit the distribution of brake pressure to the rear brake cylinders 4, 4';
, means 44 for detecting the operation of the anti-lock device 48, and switching means 52 for switching the pressure limiting devices 49, 63, 64 to non-operating positions when the anti-lock device 48 is activated via the anti-lock device operation detecting means 44. , 53. 2 has a hydraulic brake booster 1, and the pressure limiting devices 49, 63, 64 are connected to the control valve 110 of the brake force booster 1 and the master cylinder piston 2.
In the conduit 50 leading to the rear brake cylinders 4, 4', connected between the servo pressure chamber 42 of 4,
The brake according to claim 1, which is connected. 3 It has a hydraulic brake force booster, and the pressure limiting devices 49, 63, 64 are connected to the pressure chambers 25, 26 of the master cylinder pistons 23, 24 on the opposite side of the servo pressure chambers 41, 42 and the rear wheel. 2. The brake according to claim 1, wherein the brake is connected in a conduit connected between the brake cylinders 4, 4'. 4 Pressure limiting devices 49, 63, 64 are connected to valve seat 51
and a ball 49', and an anti-lock device 4
8, switching means 52, 53 for switching the pressure limiting devices 49, 63, 64 to the non-operating position when activated are connected to the switching piston 5 for separating the ball 49' from the valve seat 51.
8. The brake according to claim 1, having a diameter of 8. 5. A switching piston 58 is associated with a locking piston 54, by means of which the switching piston 58 is actuated in conjunction with the supply of servo pressure medium by the hydraulic brake force booster 1. Brake described in item 4. 6 The switching piston 58 is connected to the anti-lock device 48.
It is combined with a switching element 44 which is switched by an anti-lock signal when the switch is activated.
4, the switching piston 58 is connected to the anti-lock device 4.
8. The brake according to claim 4, which is operated in conjunction with the operation of item 8. 7 The brake force booster 1 is provided with a mechanism F:FO, F:FO that transmits different pressures to the front wheel brake circuit and the rear wheel brake circuit, and the rear wheel brake circuit has a higher brake pressure than the front wheel brake circuit. 3. A brake according to claim 2, wherein pressure is transmitted. 8. A device 31 is provided which generates approximately equal brake pressure in both brake circuits by the brake pedal depression force when the servo pressure medium supply system of the hydraulic brake force booster 1 does not work. 8. A brake according to claim 7, wherein the brake is formed by a lever or a piston surface. 9. The brake according to claim 2, wherein the pressure limiting devices 49, 63, 64 are manufactured integrally within the hydraulic brake force booster 1. 10. The brake of claim 1, wherein the pressure limiting devices 49, 63, 64 are integrally manufactured within the anti-lock device.