Pumps – Condition responsive control of pump drive motor – In response to pump speed
Patent
1995-08-21
1998-01-06
Thorpe, Timothy
Pumps
Condition responsive control of pump drive motor
In response to pump speed
417 53, 303 10, 3031164, F04B 4900
Patent
active
057047669
DESCRIPTION:
BRIEF SUMMARY
This application is the U.S. national-phase application of PCT International Application No. PCT/EP93/02226.
BACKGROUND OF THE INVENTION
The present invention relates to a method of adjusting the flow rate of an electromotively driven hydraulic pump of a brake system including anti-lock control (ABS) and traction slip control by brake management (BASR) to the instantaneous requirements, wherein the hydraulic pump is activated by a pulse train having variable pulse times and/or times of pulse break. A circuit configuration for implementing the method is also included in the present invention.
Adjusting the flow rate of pumps of this type to the requirements involves difficulties if the parameters, which determine the flow rate, vary within wide limits and the value, required in the respective situation, is to be adjusted as precisely as possible. For example, it is a problem with hydraulic brake systems including anti-lock control and traction slip control by brake management to decrease to the greatest extent possible the rotational speed of the pump with a view to minimizing noises. An extremely large number of interferences affect the rotational speed of the pump in brake systems for automotive vehicles: (a) there is a wide range of temperatures, (b) the supply voltage (i.e. battery voltage) depends on the charging condition and the age of the battery, and (c) the counterpressure, in opposition to which the pump delivers fluid, depends on the prevailing situation. Further, for safety reasons, a minimum value safeguarding the function of the brake system must fall short of whatever situation occurs.
Attempts have been made to reduce the flow rate of pumps used on brake systems by activating a series resistance in the case of traction slip control by brake management because, principally, less energy is required for a traction slip control operation by brake management than for an anti-lock control operation. Activation of the pump pulsed in response to the requirements with a view to reducing the rotational speed and, thus, noises during a traction slip control operation by brake management, has also been taken into consideration (e.g. DE 41 10 494 A1). However, due to the above-mentioned variable parameters and for safety reasons, a large "reserve volume" must be taken into account in any case, with the result that the pump, generally, must be adjusted to a higher flow rate than the flow rate actually required.
DE-A-3 241 039 discloses a brake force control unit for an automotive vehicle which has an anti-lock system (ABS) and a brake power booster (BKV). The two systems (ABS and BKV) have a common hydraulic unit with an electrically driven hydraulic pump. Because the pressure fluid requirements during anti-lock operation are increased greatly compared to partial braking operations, the drive motor of the hydraulic pump is activated by means of a series resistance in the absence of the ABS mode, when exclusively the brake power booster is used. This takes into account that the power requirement of the brake power booster is, e.g., 1 watt, while the power requirement of the ABS is, e.g., 60 watt. In the ABS mode, principally, the pump performs at its maximum output.
A circuit arrangement to control the rotational speed of a small-size d.c. motor is disclosed in EP-A-0 296 444. In this publication, the electromotive force of the generator is measured after deactivation of the motor current, and the measured value is delivered to a comparator circuit and compared with a nominal value which corresponds to the desired rotational speed. Small-size motors of this type are required for driving dental tools such as dental drills, grinders, etc.
Finally, a control circuit for a heat pump is disclosed in EP-A-0 270 474. The nominal speed value, responsive to the ambient temperature, is compared with the actual speed, and a difference signal is obtained and evaluated to adjust the speed of the motor of a compressor. There is no suggestion or hint in this publication on how to control the hydraulic pump of a brake
REFERENCES:
patent: 4399200 (1983-08-01), Galloway
patent: 4975852 (1990-12-01), Fennel et al.
patent: 5131730 (1992-07-01), Kollers et al.
patent: 5188440 (1993-02-01), Muller et al.
patent: 5222787 (1993-06-01), Eddy et al.
Brochure: Motor Control Seminar 1986, SGS Halbleiter Bauelemente GmbH, Postfach 1180, 8018 Grafing b. Munchen.
English translation (labelled PCT 7168) of the PCT International Application which was filed based on German reference DE 4 110 494.
Fennel Helmut
Honus Klaus
Kolbe Alexander
ITT Automotive Europe GmbH
Korytnyk Peter G.
Lewis J. Gordon
Thorpe Timothy
Twomey Thomas N.
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