DE2411701A1 - DEVICE FOR THE POWER SUPPORT OF ACTUATING BODIES IN MOTOR VEHICLES, IN PARTICULAR A HYDRAULIC BRAKE SYSTEM - Google Patents

Description

Daimler-Benz Aktiengesellschaft Daim 9886/4

Stuttgart March 8th

Device for the power assistance of actuators in motor vehicles, in particular a hydraulic brake system

The invention relates to a device for power assistance of actuators in motor vehicles, in particular a hydraulic brake system, wherein an operating member, for. B. the brake pedal, via a reinforcement member on an actuator, ζ. Β. a master cylinder of a dual-circuit braking system, acts.

Servo-amplified brakes are known per se in motor vehicles. Usually the negative pressure of the motor is used as a reinforcing force for this. These arrangements have the Disadvantage that they require a lot of space. In addition, they are not to be used if the motor vehicle with a central hydraulic system is equipped, which is more and more sought in recent times.

The invention is based on the object of avoiding the disadvantages outlined. So it becomes a servo gain sought, which has a significantly smaller footprint than the currently used facilities, and which particularly suitable for use with a central hydraulic supply. There should also be a force reaction to the respective control element and proportionally for increased actuation force and functional reliability can also be achieved in the event of a power failure. And finally there is a mechanical separation between the energy supply system, d. H. i.e. between the central hydraulic supply and the power transmission medium, z. B. the brake fluid aimed.

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In the above-mentioned arrangements, this object is achieved according to the invention in that a hydraulic between the operating member and the actuator acted upon servo unit is arranged, the first part of which is supported on the operating member and the second Part is connected to the actuator and that the actuation of this servo unit in the manner of a sequential control by means of a connected to the operating member Control member is controllable from a hydraulic Druckraittelquelle.

The device according to the invention has the advantage of requiring considerably less space than the previous vacuum-operated servo reinforcements. She is special for one central hydraulic supply applicable. With the proposed device, it is also possible to achieve a proportional force reaction on the operating member as well as functional reliability in the event of failure of the central hydraulic supply. And finally there is also the mechanical separation between the energy supply and the power transmission of Advantage.

Recently, systems for automatic vehicle guidance are under development or testing. For this, the The invention provides a further development in such a way that the actuation of the servo unit can be controlled by a second control element, which is connected to the hydraulic pressure medium source in parallel with the first control member connected to the operating member and which is connected by means of an electrohydraulic one Servo valve can be controlled by the control pulses of the automatic vehicle guidance.

With the invention it is further proposed that the pressure medium is guided to the servo unit via a locking element, which is held in its release position depending on the pressure in the hydraulic pressure medium source and at Pressure drop or drop in pressure can be moved into its locking position by spring force, in which it is the two sides of the

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Servo unit connects to each other. That way will a security against pressure failure is achieved, in which case a purely mechanical actuation from the operating member can be done.

In addition, in the case of the embodiment according to the invention intended for a central hydraulic supply, it is expedient to when the pressure medium is passed to the servo unit via a switching valve which is electromagnetically in one of the Inflow held by the second control member releasing position and in the event of power failure by spring force in one of the Inflow from the first control member releasing position is movable. This also provides security against power failure. Furthermore, an arbitrary one at any time Intervention in such an automatic vehicle guidance can take place, it is proposed that in the circuit of the magnet an opening when the operating member is attacked Switch is arranged. In this way, the driver has it in hand, at all times in the automatic vehicle guidance to intervene if the situation so requires.

In one embodiment according to the invention, the servo unit is displaceably guided on a pedal bracket, in on known way designed as a hydraulic cylinder-piston unit and its housing rigid with the piston in one Master cylinder connected, while their actuating piston is supported with a relatively short lever arm on the pedal. These It is expedient to use a ball head for support. The master cylinder can be in a well known manner, e.g. B. as a known two-circuit master cylinder.

Another feature of the invention can be seen in the fact that the control element and at the same time in the housing of the servo unit the locking member is arranged and both are designed in the manner of hydraulic piston valves known per se, and that the piston slide of the control member engages via a control linkage on the pedal with a relatively large lever arm. It is also proposed that for the piston valve of the control

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organs is provided axially only a small path in the housing and after overcoming this path of the piston in the housing strikes for the purpose of mechanical power transmission.

The invention is primarily intended for use in the braking system of a motor vehicle. Of course it can be applied in a very similar way to the clutch actuation and in principle of course also to other actuations of a motor vehicle.

The exemplary embodiments show details of the invention the drawing namely shows

Fig. 1 shows the structure of a brake actuation with self-reinforcement,

2 shows the structural diagram of a brake actuation for a vehicle with automatic vehicle guidance and

3 shows an embodiment according to FIG. 1 in section (partially).

According to Figure 1 is between the brake pedal 10 and the master cylinder 11 a hydraulic servo unit 12 is arranged. The pedal suspension as well as pedal training and also the The master cylinder 11 can be designed in a known manner. They do not belong to this one Invention. The diagram shows the master brake cylinder of a dual-circuit brake system.

The hydraulic servo unit 12 is designed as a cylinder-piston unit known per se. It is with the inlet line 13 to a pressure medium source not shown, for. B. a pump or a memory is connected, while the line 14 forms the return to the container, also not shown in detail. The housing 15 of the servo unit is rigidly connected to the piston of the master brake cylinder 11 by the rod 16. The piston 17 of the servo unit 12 is supported via a piston rod l8 on the pedal 10, to be precise

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with a relatively short lever arm to the pivot point 19. The housing 15 of the servo unit 12 also has a locking slide 20 and a control element 21 arranged, both of which are designed in a manner known per se as a piston slide. The control piston 21 is connected via a piston rod 22 and an anateuer linkage 23 to the pedal 10 with a relatively large lever arm to the pivot point 19. The locking slide 20 is held in the position shown via a line 2k from the inflow 13 , in which he releases the connection from the control element 21 to the servo unit 12. When the pressure is no longer applied, however, it is moved by a spring 25 into its other end division, in which it blocks the connection to the control element 21 and, on the other hand, connects the two sides of the piston 17 to one another via the recess 26.

When the brake element 10 is not actuated, all organs are in the position shown. If the brake pedal is now depressed to a greater or lesser extent, the piston slide 21 of the control device is thus activated via the anateuergeatänge 23 moved to the left in its position indicated by a. This connects the line 27 to the inlet and the line connected to the return, ao that aich can build up pressure on the left side of the actuating piston 17. This pressure now initially moves the entire housing 15 and thus over The piston length 16 also moves the piston in the main brake cylinder to the left, ao that the brake is actuated. In the existing area ratio, the actuating force is proportional to that on the left-hand side of the actuating piston 17 Incidentally, the pressure acts back on the piston 17 as a reaction force and via the rod 18 as well on the brake pedal 10. Since the latter is held in its position, the housing 15 moves relatively to the control piston 21 until the center position shown is reached again and equilibrium thus prevails. Is this braking enough, i. H. alao the brake pressure reached, not yet enough, the pedal 10 is simply continued through

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presses and the pressure increases accordingly.

If the pedal 10 is released more or less, then The piston slide 21 is pulled to the right into its position b via the control linkage 23. In this the Line connection reversed, d. that is, the line 28 is with the inlet and the line 27 is connected to the return 15. This gives the actuating piston 17 on its right side Pressure, whereby the housing 15 is shifted to the right and thus the brake master cylinder 11 is more or less relieved will. This process also continues until the state of equilibrium is restored as shown in the drawing is reached.

According to Pigur 2, the structure of the mechanical actuation, ie in principle of parts 10 to 28, is exactly the same as in the device according to Pigur 1, although the housing 15 a takes a different shape because it - as will be described later - still has to include further parts. The housing 15a is now assigned an electrohydraulic servo valve 29, the structure of which is known in principle and which has the purpose of converting the electrical control pulses of the automatic vehicle guidance supplied through the lines 30 into pressure pulses so that they can then be used for pressure control of the device according to the invention . The pressure medium feed of the electrohydraulic servo valve 29 takes place from the line 2k through the line part 31 * with a filter 32 and corresponding throttles 33 being provided to limit the quantity. The function of such a valve is known in principle, so that it does not need to be described in more detail here. It is assumed that the pulses for actuating the brake are entered via the electrical line 30 a and the pulses for releasing the brake via the line 30 b. Correspondingly, the corresponding pressure pulses are now available at the output lines Jk a and 3'ib.

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In the housing 15 a, a second control element 35 is provided in an operational manner parallel to the control element 21, and the cup is connected to the line 36 to the inlet 13 and to the line 37 to the return line. This second control element 35 is basically designed as a piston valve like the control element 21. Ee is not actuated via a control linkage 23 from the brake pedal 10; rather, it is held in its central position by springs and is operated by the lines Jk a and Jk b applied on both front sides. The function can already be seen clearly from this. If, in the event of a braking pulse, pressure builds up through the line Jk a, the piston slide 35 is displaced to the left and pressure is built up on the left side of the actuating piston 17 via the line 38 in the manner already described. The line 39 is then used to connect the right side of the piston 17 to the return. If the control pulse is reversed, the process is also reversed. The metering of the brake and the restoration of the equilibrium when the intended braking effect is achieved is carried out in this case by the electrical pulse control and the pressure difference directly associated therewith at the control element 35.

The lines 38, 39 are routed via a switchover slide kO , which is acted upon electromagnetically via the connections kl and is held in the position shown. In this position, the control element 21 - which is actuated by the pedal 10 - is switched off and the control element 35 accordingly takes over the control. If for any reason the voltage drops at the terminals kl , the spring k2 pushes the switchover slide kO into its other position, ie the control element 35 controlled by the electrical impulses is now switched off and the control element 21 controlled by the pedal 10 is switched on. I. E. in other words, there is a switchover from automatic vehicle guidance to arbitrary pedal actuation.

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So that the driver depending on the location or as desired in the automatic vehicle guidance can intervene is the Brake pedal 10 is assigned a switch 43, which is normally is closed and is only opened when the brake pedal 10 is attacked. The connections 4l are on this switch connected, so that when you tap the brake pedal, the Umachaltschieber 42 switches to its other position and now the control of the brake from the pedal 10 is taken over.

Figure 3 shows a section (partially) through an arrangement according to Figure 1. More detailed descriptions of this are in Basically not necessary. It should only be mentioned that the pedal 10 is articulated at 19 on a pedal bracket 44, which also the master cylinder 11 receives or forms. A return spring 45 constantly pulls the pedal 10 against a stop 46. The piston rod 18 is supported on the pedal via a ball head 47. From this figure, however, it can still be seen - which is quite important for the function - that the piston slide 21 in the housing 15 on both sides only one whole can travel a limited, relatively short distance. If this short path is used up, the piston slide 21 pushes open Stops 4f and 49 in the housing 15 · If the pressure medium fails, the pedal 10 can therefore use the control linkage 23 brought the piston slide 21 to the stop on the housing 15 and as a result, the brake master cylinder can be actuated purely mechanically via the piston rod 16.

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Claims (8)

Daimler-Benz Aktiengesellschaft Daim 9886/4 Stuttgart Expectations device for the power assistance of actuators for motor vehicles, in particular a hydraulic brake system, wherein an operating member, e.g. B. the brake pedal, via a reinforcing member on an actuator, z. B. a master cylinder of a two-circuit brake system, acts, characterized in that between the operating member and Actuator a hydraulically actuated servo unit is arranged, the first part of which is supported on the operating member and the second part with the actuator is connected, and that the application of this Servo unit in the manner of a sequence control by means of a with the operating member connected control mechanism from a hydraulic pressure medium source can be controlled. 2. Device according to claim 1 and with a system for automatic Vehicle guidance, characterized in that the actuation of the servo unit by a second Control organ-is controllable, which is parallel to the with the first control member connected to the operating member is connected to the hydraulic pressure medium source, and which by means of an electro-hydraulic servo valve can be controlled by the control pulses of the automatic vehicle guidance. 3. Device according to claim 1 or 2, characterized in that that the pressure medium is guided to the servo unit (12) via a blocking element (20) which, depending on the pressure in the hydraulic pressure medium source in its release - 10 - 509838/0466 - 10 - Palm 9886/4 ■ division held and in the event of a pressure drop or loss of pressure can be moved by spring force into a blocking position in which it connects the two sides of the piston (17) of the servo unit (12) with one another. 4. Device according to claim 2 or 3, characterized in that the pressure medium to the servo unit (12) via a Switching valve (40) is performed, which electromagnetically in one of the inflow from the second control member (35) release, the position is held and can be moved by spring force into a position releasing the inflow from the first control element (21) when the power is cut off. 5. Device according to claim 4, characterized in that a switch (43) which opens when the operating element (pedal 10) is engaged is arranged in the circuit of the magnet. 6. Device according to one or more of claims 1 to 5 »characterized in that on a pedal bracket (44) the Servo unit (12) slidably guided, this in itself As is known, it is designed as a hydraulic cylinder-piston unit and its housing (15 »15a) is rigid with the piston is connected in a master brake cylinder (ll), while its actuating piston (l7) with a relatively short lever arm supported on the pedal (10). 7. Device according to claim 6, characterized in that in the housing (15 »15a) of the servo unit (12) at the same time Control member (21) or (21 and 35) and the locking member (20 or 20 and 40) arranged and both naeh type per se known hydraulic piston valve are formed, and that the piston valve of the control member (21) via a Control linkage (22, 23) on the pedal (10) with a relatively large Lever arm attacks. 509838/0466 Palm 9886/4 Λ / 1. 8. Device according to claim 7 »characterized in that that axially only a small path is provided for the piston slide (21) dea control member in the housing (15) and after overcoming this path, the piston (21) in the housing (stops 48, 49) strikes for the purpose of mechanical power transmission. 509838/0466 Blank page