DE4317790A1 - Circuit for controlling an electrically operated hydraulic pump - Google Patents

Abstract

A circuit for controlling an electrically operated hydraulic pump which is part of a brake system with ABS and TCS comprises an engine relay (16) which activates a switching contact (18) which is located in the actuation line (21) of the pump motor (7), and a safety relay (17) with a switching contact (19) which lies in series with the contact (18) of the engine relay (16). By means of the engine relay, the pump is actuated in the ABS mode by means of continuous signals and in TCS mode it is actuated in a clocked fashion. The switching contact (19) of the safety relay (17) remains closed in TCS mode for the duration of the control; in ABS mode the engine relay (16) and the safety relay (17) are actuated simultaneously. <IMAGE>

Description

The invention relates to a circuit arrangement for Control of an electrically driven hydraulic pump, the for supplying auxiliary pressure or pressure medium to a brake system with anti-lock protection (ABS) and traction control (ASR) serves, with the help of a motor relay, one in the control path the switching contact of the pump is actuated, whereby in vorege ned phases of the control the speed and delivery rate of the Hydraulic pump through clocked activation of the motor relay and thus the hydraulic pump is limited.

One is already published in DE 41 10 494 A1 Brake system with anti-lock and traction control known to be a hydraulic pump for auxiliary pressure supply sits, whose drive motor in ASR mode via a series resistor was driven. This way the performance Recording and thus the speed of the hydraulic pump on one Sufficient value limited in ASR mode. With the rev reduction is a reduction in noise forth. Instead of a series resistor, an electronic cal relay are used, the power consumption the motor of the hydraulic pump by controlling the relay is adapted to the respective need with a pulse train.  

It has also been suggested that the pump be in ASR mode controlled by a mechanical relay (Pa tent registration P 42 29 691.9). Such mechanical relays are inexpensive compared to electronic relays, but be there may be special measures to be taken with the mechanical relay a sufficient life for the present application to ensure long-term expectation. As is well known, tend the contacts of mechanical relays when high currents are too stale are for welding or gluing the contact elements te; this would have been an ongoing one in the present application Switching on the hydraulic pump, premature wear and tear Discharge of the vehicle battery.

The invention is based on the object, the aforementioned to overcome ten disadvantages and a circuit arrangement of to develop continued operation the controlled brake system in the event of a defective motor relay or permissible closed motor relay contact.

It has been found that this task through the enclosed claim 1 further development of one of the like circuit arrangement can be solved.

The additional effort required is limited to installation an additional relay. Because the contact of this relay only is actuated at the beginning and at the end of the regulation, but not when clocking the control signal, the confidence reliability of this relay and its life expectancy equally very high.

The invention proves to be of particular advantage in the case of Verwen  mechanical relay, but is also used of electronic relays the operational safety of the brake location significantly increased.

Some advantageous embodiments of the invention are described in the attached subclaims.

Other features, advantages and possible uses of the Invention go further from the following description of De tails from the attached pictures.

It shows

Fig. 1 in a simplified, schematic representation of the most important components of a controlled braking system with a circuit arrangement according to the inven tion and

Fig. 2 in the diagram of the course of the relay control signals, the voltage across the contacts and the pump motor current in different situations.

1 is in the embodiment according to FIG. A dual-circuit brake system with anti-lock control and traction slip control by brake intervention. Darge is a tandem master cylinder 1 with an upstream vacuum booster 2 , a valve block 3 , a pressure equalization and reservoir 4 and an auxiliary pressure supply system 5 , which according to the schematic representation of the actual hydraulic pump 6 and an electric drive motor 7 . Only one hydraulic pump circuit is shown; in fact, two hydraulically separated pumps with a common drive motor are often used.

The system of FIG. 1 is one of the "open" systems in which the pressure medium discharged from the wheel brakes in the pressure reduction phase flows via a return line 8 into the container 4 , to which the suction sides of the hydraulic pump 6 is also connected, flows back. In a "closed" system, to which the invention applies equally, the pressure medium derived from the wheel brakes is returned directly into the brake circuit and into the master cylinder of the brake system with the hydraulic pump. Brake systems with open and closed hydraulic systems are known in a wide variety of training, which is why there is no need to go into further details here.

In the valve block 3 electrically controllable Hydraulikven tile are housed, with which the brake pressure during an anti-lock or traction slip regulation can be adjusted to the value calculated in electronic circuits in a known manner. From this valve block 3 brake lines lead to the symbolically represented wheel brakes 9 to 12 of the individual vehicle wheels. In addition, the Rückflußlei device 8 and the pressure side of the auxiliary pressure supply system 5 and the hydraulic pump 6 are connected to the valve block 3 .

The individual vehicle wheels are equipped with wheel sensors S₁ to S₄, with which the rotational behavior of the individual wheels is measured and corresponding signals are fed to a controller 13 for processing and evaluation. Via an electrical multiple line 14 , which is connected to an output A _{n of} the controller 13 , the electrical control commands or control signals are fed to the individual (not shown) electrically controllable hydraulic valves in the valve block 3 .

In the controller 13 , the electronic circuits, including one or more microcomputers, monitoring circuits, etc. are summarized. A dashed symbolically divided area 15 of the controller 13 contains or symbolizes the circuits or program structures required to control the pump motor 7 .

Essential to the invention is the design, arrangement and control of the two relays 16 , 17 with the associated switching contacts 18 , 19 arranged one behind the other in the control path of the pump motor 7 . In the illustrated embodiment of the invention, there are two mechanical relays 16 , 17 . The relay 16 is the actual motor relay, while the second relay 17 is used here as a safety relay.

The two relays 16 , 17 are controlled via outputs A1, A2 of the controller 13 . In the illustrated embodiment of the invention, the pump motor 7 , when the switch contacts 18 , 19 are closed, and the relays 16 , 17 , when a connection to ground is established via the controller 13 , are supplied with current from the vehicle battery U _B. By a circuit block 20 is indicated in Fig. 1 that between the battery U _B and the leading to the pump motor 7 or to the relays 16 , 17 leads 21 , 22 further relays (the so-called. "Main relay"), steering lock contacts, fuses etc. are usually inserted.

To control the relays 16 , 17 13 connections are made from the outputs A1, A2 to ground in the controller. The re relays 16 , 17 , which are designed here as mechanical relays, are each assigned a normally open contact 18 , 19 . These Ar beitskontakte 18 , 19 are connected in series in the connecting line 21 or in the control path of the pump motor 7th

V _CC denotes the connection of the electronics of the controller 13 to the power supply. The ground connection of the entire circuit is also shown symbolically.

With the aid of the pump control relays, here the relays 16 , 17 , the hydraulic pump for the auxiliary pressure supply or for pressure medium return is switched on "as required" in a controlled brake system of the present type. It is known that during an anti-lock control, at least in the worst case, a significantly higher pressure is required than in the case of traction control. For this reason, in the brake system described here, the pump motor is fundamentally operated at full power during ABS control or is operated with continuous signals, that is to say signals which are constantly present during the pump's on times, while the pump is actuated “clocked” in ASR mode. Through this clocked control with pulse sequences, the power consumption and thus the speed is limited in ASR mode to a value that is significantly lower compared to control with the continuous signals, which among other things results in a reduction in pump and valve noise. Fig. 2 illustrates the control of relays 16 , 17 in ABS and ASR mode, with the motor relay intact and defective.

The relay 16 controlled via the output A1 is the actual motor relay in the present case, while the relay 17 controlled via the output A2 serves as a safety relay. With the signal A1 and the relay 16 , as the upper curve in FIG. 2 shows, the relay 16 is controlled with permanent signals in the ABS mode, with pulses or clocked in the ASR mode. The output signal A2, which leads to the safety relay 17 , is controlled in the ABS mode at the same time as the motor relay 16 , while in the ASR mode the safety relay 17 remains closed during the clocking; in the off operation example according to FIG. 2, the safety relay 17 is closed at the beginning of the traction control, reopened at the end of the scheme.

If a relay error now occurs, which leads to a faulty sticking or welding of the contact elements of the switching contact 18 - see third line in FIG. 2 - this has because of the series-connected switching contact 19 of the safety relay 17 and activation of this relay by the output signal A2 in ABS mode has no effect on the control. The warning lamp WL is only lit up via the controller 13 . In contrast, in ASR mode the clocked pump control signal is replaced by a continuous signal. The traction control continues. The control of the pump motor 7 with the continuous signal has only Lich an increase in noise. The pump ( 6 + 7 ) is switched off again after the end of the regulation of the regulation so that no overloading of the motor by a permanent operation or premature discharge of the vehicle battery can occur. Of course, this fault is signaled with the help of the warning lamp WL. The last line in FIG. 2 shows the course of the pump current I _M.

From the waveform of FIG. 2 it can also be seen that the switching contact 19 of the safety relay 17 is subject to a considerably lower load because the contact 19, in contrast to the contact 18 of the motor relay 16 , remains closed during the clocked actuation of the pump motor 7 . With the same design of the two relays 16 and 17 , a significantly longer service life of the relay 17 can therefore be expected, so that it can actually function as a safety relay.

Claims (8)

1. Circuit arrangement for controlling an electrically driven hydraulic pump, which is used to supply auxiliary pressure or pressure medium to a brake system with anti-lock protection (ABS) and traction control system (ASR), with the aid of a motor relay that actuates a switch contact located in the control path of the pump, whereby In predetermined phases of the control, the speed and delivery capacity of the hydraulic pump is limited by clocked actuation of the motor relay and thus the hydraulic pump, characterized in that a further relay serving as a safety relay ( 17 ) is provided, which has a switch contact ( 18 ) of the motor relay ( 16 ) lying in series Schaltkon clock ( 19 ) and is controlled such that the switch contact ( 19 ) of the safety relay ( 17 ) remains closed for the duration of the clocked activation of the motor relay ( 16 ) and outside of this time period with the switch contact ( 18 ) of the motor relay ( 16 ) closed u nd is opened. 2. Circuit arrangement according to claim 1, characterized in that the safety relay ( 17 ) is controlled in ABS mode at the same time as the motor relay ( 16 ), in ASR mode for the duration of the control. 3. Circuit arrangement according to claim 1 or 2, characterized in that the motor relay ( 16 ) and / or the safety relay ( 17 ) are designed as mechanical relays. 4. Circuit arrangement according to claim 1 or 2, characterized in that the motor relay ( 16 ) and / or the safety relay ( 17 ) are designed as a semiconductor relay. 5. Circuit arrangement according to one or more of claims 1 to 4, characterized in that the hydraulic pump ( 6 + 7 ) is controlled in ABS mode with continuous signals, in ASR mode with pulsed or clocked signals. 6. Circuit arrangement according to claim 5, characterized ge indicates that the clocked signal is off a pulse train with a constant or variable pulse There is a permanent / pulse pause ratio. 7. Circuit arrangement according to claim 6, characterized in that mechanical relays are provided as motor relays ( 16 ) and as safety relays ( 17 ) and that with clocked actuation the duration of the individual pulses to a value between 20 and 60 ms and the pulse pauses a value between 80 and 150 ms are specified. 8. Circuit arrangement according to one of claims 1 to 7, characterized in that the hydraulic likpump ( 6 + 7 ) is controlled in the ASR mode only during the brake pressure build-up phases.