DE2046802A1 - Hydraulic braking system with anti-lock regulator - Google Patents

Description

Hydraulic Brake System with Anti-Lock Control The invention relates to a hydraulic brake system with anti-lock regulator, in which in the lines, which connect the pressure source with the wheel brake cylinders, from the anti-lock regulator controlled shut-off valves are switched on.

It deals in general with the problem of operational safety to increase hydraulic braking systems by taking precautions which prevent the failure of the entire system if a brake line breaks or, for example, leaks due to slurry or corrosion.

This goal is also achieved with the well-known and widespread dual-circuit brakes pursued, but it must be noted that if the front Braking supply circuit only approx. 30, the braking effect remains. According to experience namely brings the brake of a front wheel of a vir-wheeled vehicle 35% and the brake of a ginter wheel 15% of the braking effect.

Another disadvantage of the known dual-circuit brake is that that if a brake circuit fails, its entire master cylinder volume is lost goes and thus a relatively large pedal movement occurs, which is also known as "Brake pedal falling. This phenomenon has been shown to be extreme adverse psychological effects on the driver who is surprised by it and frightened.

There is a higher residual braking effect if a brake circuit fails with the so-called dual-circuit brakes, which are also known. Underneath will understood a brake system in a four-wheel vehicle, whose front brakes Je have two separately fed brake cylinders.

One brake cylinder each on the front wheels and the brake cylinder on one Rear wheels are jointly connected to a brake circuit. In this case it remains in the event of a brake circuit failure on each front wheel, half the braking effect, what with the braking effect of the remaining rear wheel together a residual braking effect of 50% results.

It is also known from German Offenlegungsschrift 1 530 914 that that in the pulp line system one or more cylindrical spacers with im Inner movable pistons are arranged, the pistons in the event of a loss of brake fluid interrupt the connection from the main brake link to the defective line. By the piston stroke covered thereby becomes a warning display by means of a contact device triggered. A disadvantage of this device, however, is that the brakes not, as is usual in workshops, vented by pumps on the master brake cylinder can be, because namely the piston the resulting high liquid throughput impede.

The invention is based on the object of providing a braking system if one of the brake lines leaks Highest possible residual braking effect retains. This braking system should take into account the anti-lock braking control required effort to be as simple as possible and bleeding the brakes allow by pumping on the main brake cylinder.

The solution to this problem results from what is characterized in claim 1 Features, it being assumed that volume monitors are known per se. However, according to the invention, your electrical signal is not used as a warning, but rather effective used to lock the line.

When assessing this solution, the fact must be taken into account that approx. 80% of all brake failures are due to leaks in the area of the brake hose and the brake itself. If so, like this with the invention is provided, the shut-off valves are arranged centrally, so can with these valves the most endangered part of the hydraulic pipe system is effectively protected will. In the worst case, the system according to the invention can be caused by a leak a front wheel brake fails in the brake line leading to a front wheel, However, the residual braking effect is still 65%.

The proposed approach is particularly well suited for vehicles, their front wheels according to the construction described in German patent 1,077,538 are hung. Then the swivel axis of the front wheels intersects the road outside the standing area, which has the consequence that even when pulling unevenly Braking and in extreme cases with only one braked front wheel the vehicle without any Angular deviation from the previous direction runs straight ahead and also not a disturbing one Moment back to the steering wheel.

It is a further advantage of the invention that in one Line defect the loss of volume is very limited and thus also the noticeable pedal movement is low.

A cylinder is provided as a volume monitor in the sense of the invention, which by a movable piston in two.

Chambers is divided. One of these chambers is with the shut-off valve and the other connected to the line leading to preferably a wheel brake cylinder continues. The piston makes the displacements of the brake fluid column when Brakes with and actuates an electrical contact when it reaches a certain switch position achieved, which - however, can only occur in the event of a leak.

Other developments of the invention result from the following Points of view. At the beginning of braking, the piston must always be in the same starting position take in. The chambers on both of its sides are therefore through one in the longitudinal direction running channel connected to each other, which contains a fine nozzle. The piston is held in the initial position by a return spring. But not with that through these measures the necessary, rapid pressure reduction when relieving the brake is hindered in the event of a longer braking, there is another channel with a non-return valve provided, which opens from the wheel brake cylinder to the shut-off valve.

It is well known that the brakes are vented in the workshops by that by pumping on the brake pedal a relatively large amount of liquid through quickly the pipe system is pressed. This process is allowed by the invention Leak sensor are not obstructed. It is therefore further proposed that the piston can move beyond the switch position into an end position in which he by means of a longitudinal channel with a sufficiently large cross-section on the inner wall of the cylinder is bypassed.

With regard to the design of the switching device to be actuated by the piston a high level of operational safety must be ensured. In this regard, it is proposed that that the piston contains or magnetizes a permanent magnet and a magnetic field sensitive ßehutzgeekontakt is arranged on the cylinder in such a way is that it is actuated in the switching position of the piston by its magnetic field. The protective gas contacts mentioned are already widely used today under the name "Reed contacts" * In addition to the extremely small dimensions, they have the advantage of that they cannot oxidize even over long periods of time. It is also advisable to the electrical signal generated by the volume monitor to an electrical memory to forward, which any warning device even after termination of the signal keeps in operation, at least until the power supply is switched off by switching off the ignition.

It is particularly intended to testify with the invention in driving To use dual-circuit braking system and individual wheel control. However, you could too to be used on vehicles with a single-circuit braking system, provided the wheels or at least the front wheels are only individually regulated.

An embodiment of the invention is described below with reference to the Description of the drawing: Fig. 1 shows a simplified hydraulic-electrical circuit diagram a braking system according to the invention and Fig. 2 shows a longitudinal section through the volume monitor.

In Figure 1, a tandem master cylinder 1 is shown, the piston is operated by a brake pedal 2. The main pressure line 3 of a brake circuit branches off and leads to two inlet valves 4 and 5. These are via two leak sensors 6 and 7 connected to the wheel brake cylinders 8 and 9 of the front wheels. On the connecting lines branches are provided between the inlet valves and the leak sensors through Exhaust valves 10 and 11 are normally closed. That with the pressure reduction here Depending on the embodiment selected, the pressure medium flowing out becomes a collecting vessel or fed back into the corresponding main brake line by means of a pump. the Main brake line 12 of the second brake circuit leads accordingly to two inlet valves 13 and 14 and via leak sensors 15 and 16 to the wheel brake cylinders 17 and 18 of the Rear wheels. The. Exhaust valves are designated here with 19 and 20. The valves are controlled by an electronic anti-lock regulator 21. The signals flow to the Inlet valve 14 via a line 22 and the outlet valve 20 via a line 23 to. On the other hand, the controller receives signals about the rotational behavior of the braked Wheel from a sensor 24 on the left rear wheel via a line 25. Correspondingly the wheel sensors 26 to 28 are connected to the controller at 29, while controller outputs 30 and 31 lead to the remaining exhaust and intake valves. The inventive The connection of the leak sensors is again only shown using the example of the leak sensor 16. Its output signal flows to one input of a memory 32. A brief one Signal sets the memory so that a signal appears at its output, which The inlet valve 14 closes via an OR gate 33. At the same time is about a another OR gate 33a actuates a warning device 33b. When turning off the Ignition switch 35 arrives at the second input via an inverter 34 of the memory, so that it tilts back into its idle state. On the other leak sensors 6, 7 and 15 are connected to corresponding memories, the outputs of which are their respective Control inlet valves and are connected to OR gate 33a at 33c.

It is thought that the bin and exhaust valves as well as the leak sensors combined into a structural unit or at least spatially close to one another in the engine compartment are housed. The lines from the leak sensors to the wheel brake cylinders are therefore relatively long, which is in the Drawing by a dashed interruption is indicated. These parts of the line become through her associated inlet valve shut off when they themselves ode the wheel brake cylinder a Have a leak.

Figure 2 now shows the design of the leak sensors in detail. A Cylinder 36 has two connections on the end faces, one of which 37 with one the inlet valve and the other 38 is connected to a wheel brake cylinder.

A piston 39 can be located in the cylinder between the stops 40 and 41 move. A spring 42 normally holds the piston in the position shown.

So that the piston moves in the event of permanent volume shifts, e.g. after brake bleeding, can move back to the starting position, he is penetrated by a longitudinal channel 43 into which a screw 44 with a fine nozzle 45 is screwed in. A second longitudinal channel 46 contains a check valve, consisting from a ball 48 which is pressed onto its seat by a spring 47. The feather is supported against a cannulated screw 49.

The check valve opens the passage for the pressure medium when Release the brake.

The piston also contains a rod-shaped permanent magnet 50, the contact 51 cooperates with a magnetic field-sensitive protective gas. Of the Inert gas contact is inserted into the cylinder wall 36 or at least in the Arranged near the wall.

In the pressure build-up phase, the brake fluid is supplied by the master pressure cylinder 1 moved to the wheel brake cylinder. According to the volume moved, it also moves the piston 39. The volume is given and limited by the maximum operating pressure the brake and the resulting elastic deformation of components. At normal With a vented brake, this volume is known to vary slightly.

The piston moves according to these conditions Consequently during normal operation of the brake in the area of the stroke 55.

If the braking lasts longer, the piston is due to its spring and moved back again as a result of the nozzle 45, possibly up to its starting position. If the pressure in the main brake line drops after braking has ended, it is relaxed the pressure in the wheel brake cylinder via the non-return valve, whereby the ball 48 lifts from its seat.

If a leak now occurs in the line connected at 38, it is moved the piston 39 moves beyond the aforementioned maximum stroke 53 into the position 54. This is the switch position in which the magnetic field of the magnet 50 makes the protective gas contacts brings into contact with each other. This immediately becomes the corresponding inlet valve closed and the warning device activated.

When the brake is vented, the piston 39 moves into its end position 55, in which the pressure medium through the channel 52 a free connection bypassing of the piston finds. This allows large volumes to pass through the line unhindered be pumped.

- patent claims -

Claims (7)

Claims 1. Hydraulic brake system with anti-lock regulator, in the lines that connect the pressure source to the wheel brake cylinders Shut-off valves controlled by the anti-lock regulator are switched on, characterized in that that each shut-off valve (14) is assigned a volume monitor (16) to which the volume of the pressure medium flowing from the valve in question to the wheel brake cylinders (18) detected and if a certain volume is exceeded, an electrical one A signal is given which keeps the shut-off valve closed with priority and a warning signal (33b) triggers. 2. Hydraulic brake system according to claim 1, characterized in that that the volume monitor consists of a cylinder (36), which by a movable Piston (39) is divided into two chambers with the shut-off valve and the wheel brake cylinders are connected, and that the piston in a certain switching position (54) a electrical contact (51) actuated. 3. Hydraulic brake system according to claim 2, characterized in that that the chambers on both sides of the piston (39) through two channels (43, 46) with one another are connected, one of which is an open from the wheel brake cylinder to the shut-off valve Check valve (48) and the other a fine nozzle (45) and that the piston normally by spring force (42) in an initial position adjacent to the shut-off valve is held. 4. Hydraulic brake system according to claim 3, characterized in that that the piston contains a permanent magnet (50) or is magnetized and on Cylinder one magnetic field sensitive protective gas contact (51) like this is arranged that it is in the switching position (54) of the piston of its magnetic field is operated. 5. Hydraulic brake system according to claim 3, characterized in that that the cylinder has a longitudinal channel arranged and dimensioned in this way on its inner wall (52) has that a connection bypassing the piston is created between the chambers, if this is in an end position following the switching position (55) is located. 6. Hydraulic brake system according to claim 1, characterized in that that the volume monitor is connected to an electrical storage device (32), which maintains the warning signal until the power supply is switched off. 7. Hydraulic brake system according to claim 1, characterized by the application of the invention in vehicles with a two-circuit brake system and individual wheel control.