Electrically controlled brake installation for vehicles.

Electric brake system

p0001The invention relates to an electric brake system according to the preamble of claim 1.

p0002In an electric brake system, in particular for commercial vehicles, the brake cylinders are actuated by a pressure fluid, mostly compressed air. The control of the brake pressure here but not by means of a tread plates brake valve control pressure graded. Instead, the brake pedal is provided with an electrical setpoint device, for example a potentiometer. The output of the encoder is supplied to an electronics. Here the signal is modified by additional facilities, for example, depending on the load (ALB, automatic load-dependent brake), radschlupfabhängig (ABS, Anti-lock braking system) and / or in coordination with additional brake (retarder) can work.

p0003The resulting brake signal is passed to solenoid valves (modulators), which control the supply of the pressure medium to the brake cylinders. Such a solenoid valve may be constructed (digital or analog) according to different principles. Instead of a mere control of the braking pressure can be adjusted also to a desired value. In this case, the actual pressure is generally monitored by a pressure sensor and fed back.

p0004Electrical braking systems have the advantage of allowing a particularly precise dosage and rapid braking. Next can be also previously known hysteresis of the tread plates brake valve and other control valves (ALB others) eliminate.

p0005At braking systems are inherently more demanding high security to. Thus, for example, mutatis mutandis, laid down in international regulations, that even with a failure in the electrical, electronics or a modulator of an electronically controlled brake system operating a road vehicle still a restricted, so-called auxiliary or residual braking effect can be achieved. This requires a minimum two-section structure of the service brake system.

p0006As an alternative to a dual-circuit electronics and electrical power supply es.zB is analogous to the hydraulic booster brake systems as used in USA or also in DE-OS 20 65 815 and DE-PS 20 62 533 are described - obvious a pneumatic redundancy to a single circuit provide electronics and power supply. It must be pressed to the brake pedal in addition to the electric setpoint adjuster also a common pressure-gradation valve. With the stepped pressure the brake cylinder directly via valves (DE-OS 32 30 970) or indirectly via suitable modulators (DE-OS 32 30 971) are driven in total failure of the electronics or electrics. Thereby, the wheel brakes can be actuated pneumatically in the event of an error. The disadvantage of these solutions is that the normally inactive pneumatic circuit must be Uber guard by at least one additional pressure sensor (DE-OS 33 37 800).

p0007The invention is based on the object to provide an electric brake control of the aforementioned type, which is additionally provided with an advantageous and cost-effective redundant pneumatic control.

p0008This object is achieved by the contained in claim 1. invention. The sub-claims contain expedient developments of the invention.

p0009In the electric brake system according to the invention of redundant pressure of the tread plates valve acts directly on the exhaust ports of the pilot and / or main valves of the pressure modulators. This can be vented this over the to a certain relative or absolute pressure difference AP (eg 1 bar) lower redundant pressure. By this measure, a ver improved control quality and a fine stage partial braking is achieved due to the slow bleed in spite of large nominal width of the modulator-venting valve.

p0010The invention is explained below with reference to a drawing. The drawing shows a schematic representation of the essential parts of the brake system according to the invention. In<ul><li>Fig. 1 is the basic scheme, and in</li><li>FIG. 2 an embodiment with an antilock braking system. The</li><li>Fig. 3 to 6 show specific embodiments of the measures provided for in the brake pressure modulator.</li></ul>

p0011In Fig. 1, 1 a compressed-air reservoir of a commercial vehicle designated. The reservoir is connected via a line 2 to a tread plate valve 5 and to a solenoid valve (modulator) 10th The tread plate valve 5 is part of a braking value generator 3. The latter is equipped in addition with an electrical desired-value transmitter 4 which is connected via a line 8 to an electronic 6th One or more output lines 9 of the electronic unit 6 is / are connected to one or more actuating coil of the solenoid valve 10th

p0012The output terminal of the step plate valve 5 is connected via a line 7 to the vent port 11 of the solenoid valve 10th The output of the solenoid valve 10 (the front axle VA here) and connected to a pressure sensor 22 via a line 21 to the brake cylinders 12,13 one brake circuit. The latter is connected via a line 23 with the electronics. 6 It can be integrated in the solenoid valve 10 (modulator).

p0013The installation described functions as follows.

p0014In braking operation of the electric setpoint generator 4 a signal to the electronics 6 from. This signal is processed in electronics. Signals may be charged here other, not shown means, such as ALB, ABS added dder retarder and logically. With the resulting output signal of the solenoid valve 10 is driven according to the braking operation. With the thus set initial pressure on the line 21, the brake cylinders 12,13 are actuated.

p0015The pressure sensor 22 reports back the brake pressure of the electronics 6 and thus closes the electro-pneumatic control loop.

p0016If the solenoid valve 10, for example, a proportional valve, the pressure sensor 22 may not be necessary for representation of the basic control loop. It may then serve up to monitor or improve the control quality.

p0017In braking power transmitter 3 a usual graduated brake pressure is simultaneously generated by a treadle valve. 5 This opens the vent 11 of the solenoid valve 10th And in enhancing the holding constant of the brake pressure thereby then vent closed-magnetic valve 10 is not affected. However, reduced by the driver of the nominal braking value, then vented, the solenoid valve 10 via the line 7 and the vent port of valve Trittplatten- fifth

p0018The pressure conditions are adjusted so that the output pressure of the valve 5 on the line 7, for example, about 1 bar lower than the output pressure of the solenoid valve 10 on the line 21. By so throttled venting of the solenoid valve 10 is a softer brake release effected.

p0019In FIG. 2, a braking device is shown, which additionally contains an anti-lock brake system (ABS). To this end, the electronic unit 6 are supplied to 16.17 signals via the wheel speeds in the known manner via wheel sensors. To the two wheels of a brake circuit to brake controlled individually (the front axle VA here), here two solenoid valves 10,14 are provided, the pressure inputs are connected via the line 2 to the compressed air reservoir. 1 The solenoid valves 10,14 are actuated via lines 9 by the electronics. 6 The controlled brake pressure is measured by pressure sensors 22,24 and communicated to the electronics via lines 23,25.

p0020In contrast to the system of FIG. 1 is in the two solenoid valves 10,14 common vent line 7 is inserted a check valve 19 which is actuated by the electronic unit 6 via a line 20. The check valve 19 is formed as a solenoid valve and normally switched to passage. Only in special cases, such as an ABS regulated braking, the stop valve 19 is controlled by applying a signal of the electronic 6th This then the vent solenoid valves 10,14 is not made through the treadle valve 5, but directly into the open. Thus the necessary in the controlled braking fast venting operations are guaranteed to below the predetermined by the driver pressure setpoint.

p0021The check valve 19 may also be reversed when the service braking performance to be retained because of superimposed Retarderbremswirkung or when the driver wants to release the brake particularly quickly.

p0022This is then detected by the electronic unit 6 and the shutoff valve 19 via the line 20 optionally connected to venting.

p0023Similarly, the check valve 19 may then be reversed when the brake pressure in non- or partially loaded vehicle is to be reduced in accordance with a supplied by a sensor 26 axle load value against the braking setpoint determined by the driver.

p0024Especially for ALB arrangements with bend characteristic, it may be advantageous to replace the 3/2-way shut-off valve 19 in a conventional manner by a 2/2-way holding valve and a 2/2-way vent valve (not shown). Then only the hold valve needs to be activated, once the controlled by the treadle valve 5 redundant pressure would reach and exceed the ALB-regulated pressure. This is the case only at a relatively small number of brake actuations. Such Anordnug reduces air consumption and the magnetic actuation of the shutoff valve 19th

p0025If the electrical power supply, electrics, electronics 6 or the solenoid valves should 10,14 fail due to an error, so that the latter can no longer be controlled electrically, is the arrangement of the invention can still braking by the generated by the treadle valve 5 redundant pneumatic allows printing. This goes beyond the line 7 and the vents of the solenoid valves 11,15 10,14 directly on the brake cylinder 12.13.

p0026According to the invention the air guiding of the redundant pressure by the solenoid valves 10,14 to the braking distance of cylinders 12,13 and to the pressure sensors 22,24 so made is formed such that the pressure sensors, both to the actual electro-pneumatic brake pressure control as well as for monitoring the redundant pneumatic circuit ( line 7) may be used. The latter is done by means of suitable test routines by the electronics. 6

p0027Figs. 3 and 4 as sections of Fig. 1,2 show two exemplary embodiments of the solenoid valve 10 with directly controlled 2/2-or. 3/2-way solenoid valves 10a, 10b.

p0028According to FIG. 3 which consists in Figs. 1,2 shown as a single unit solenoid valve 10 (modulator) comprises two 2/2-way solenoid valves 10a, 10b. The valves 10a, 10b are driven by the electronic unit 6 via lines 9,9a, 9b. The valve 10a blocks not driven from the supply pressure in line. 2 The valve 10b vented not actuated brake cylinder 12 in the conduit 7. A brake pressure increase is effected by permanent reversal of the exhaust valve 10b in the closed position and - depending on the design of the valve 10a - through continuously or clocked driving of the intake valve 10a in the open position. The reversing only the exhaust valve lOb leads to maintain pressure. Logically, there is a pressure reduction through Nichtansteuern both valves. As described above, the pressure reduction is carried out also in permanently open exhaust valve 10b with a low gradient, provided that abuts a counter-pressure at the connection 11 via the valve 5 and the tread plate line 7th

p0029Corresponds to the back pressure to the atmospheric pressure, occurs a steeper Entlüftungsgradient. This is the case if the check valve 19 shown in Figure 2 is switched by the electronics 6 or the redundant pneumatic circuit by mistake -. Has failed - for example, in the treadle valve 5, the line 7 or the shutoff valve 19.

p0030According to this situation is to monitor the redundant pneumatic circuit as follows exploited. As known from anti-lock braking systems, leading the electronics 6 upon boarding and during driving test routines for testing the electro-pneumatic brake system. These are extended to monitoring the redundant circuit. When initiated by the driver by actuating the brake signal transmitter brake tests upon boarding and partial braking, the solenoid valves 10 a, are momentarily not driven in targeted test routines despite setpoint. This places the known one of the electronic differential pressure, for example 1 bar; lower redundant pressure of the treadle valve 5 in the brake cylinders 12,13 and the pressure sensor 22. Reports of the pressure sensor 22 of the electronic unit 6 a corresponding to the target value "right" redundant pressure is detected, the test result as properly. Otherwise, a retest and / or error indication.

p0031In addition, can be briefly operated within the test routine and the shutoff valve 19th Properly then the electronics 6 must recognize a corresponding further pressure reduction and subsequent increase in pressure of redundant pressure.

p0032Furthermore, a check is made at brake release operations in that by a further test routine, the check valve is triggered 19 briefly switched or longer lasting, and thereby resulting modified (increased) Entlüftungsgradient will detected by the electronics. 6

p0033According to FIG. 4, the solenoid valve 10 (modulator) 10b of a 3/2-way change-over valve 10 a and a subsequent holding valve. An increase of the braking pressure is carried out by reversing the valve 10a. A reduction takes place in the position shown. A pressure maintenance is performed by reversing the holding valve 10b. To limit the pressure gradient at the fuel control 27 may be provided a choke.

p0034The test routines described above for the arrangement of FIG. 3 are then applied accordingly. This also applies when, for example, the valve 10a of Fig. 4 is formed as a proportional valve, as well as not shown other modulator arrays.

p0035FIGS. 5 and 6 show as sections of Figs. 1, 2 show two exemplary embodiments of the solenoid valve 10 (modulator) with pilot valves.

p0036According to the FIG. 5 control the solenoid valves 10a, 10b according to FIG. 3 in a conventional manner a relay valve 10c before. The pressure sensor 22 detects this pilot pressure and leads its signal to the electronics 6. According to the invention 1 to 3, the redundant pressure via the line 7 to the pilot valve 10b and above the pressure sensor 22 and the relay control chamber of the relay valve 10c is in contrast to the Fig. Fed. Not only the above-described testing capabilities applied mutatis mutandis, but also the beneficial effect relays for the redundant circuit are exploitable. In addition, the redundant circuit (line 7) can also be connected to the main vent 11 of the relay valve 10c.

p0037According to FIG. 6 detects, in contrast to Figure 5, the pressure sensor 22 does not push the pilot, but the outsorted from the relay valve 1Oc brake pressure. Here is sufficient in itself a connection of the redundant cancer to the main vent 11 of the relay valve 10c to ensure the redundant braking effect and the monitoring by the pressure sensor 22nd The additional connection of the pilot valve 10b to the conduit 7 allows exploiting the relay effect of the redundant circuit and improves the control convenience with partial braking.

p0038The arrangements according to FIG. 5.6 shall apply mutatis mutandis in modulators, where instead of a relay valve 10c diaphragm valves or other pilot operated valves are used.