DE102007034113B4 - Method for calibrating a hydraulic pump - Google Patents

Abstract

A method for determining the speed of an electric motor, which is part of a motor pump unit (10) in a pressure control device, wherein the speed of the motor and thus the capacity of the pump with the electrical drive power of the motor is related and the speed of the pump by means of a control Changing the drive power is set, wherein furthermore the motor comprises no means for determining the rotational speed comprises a determination of the rotational speed by hand pressure pulsations of the conveying fluid and the pressure pulsations are measured in particular on a pressure sensor (16) of the pressure control unit, characterized in that the generator voltage of Pump motor is measured and this is used together with the speed determined by the pressure pulsations for determining one or more calibration values, wherein the calibration or the (s) a functional or tabular relationship between "generator voltage ng "and" pump speed "produce, where as a calibration value, the numerical ratio between generator voltage and speed is formed.

Description

The invention relates to a method for calibrating a hydraulic pump according to the preamble of claim 1 and an electronic motor vehicle brake control system according to claim 9, in which this method is used.

Today usual electronically controlled motor vehicle brake systems for driving dynamics or anti-lock regulations, such as in the DE 10 2005 041 556 A1 (P 11192) described, usually include at least one hydraulic pump for the return delivery of brake fluid in a brake fluid reservoir, which can also be used for the purpose of active pressure build-up. An active pressure build-up is necessary in the event of independent braking intervention, for example within the control functions "Vehicle dynamics control" (ESP) or "automatic distance control" (ACC) as well as "traction control" (TCS). For driving the pump, a DC electric motor with a commutator is usually used, which is clocked, for example driven by a pulse width modulated current control. The basic structure of a corresponding brake system is shown in the block diagram in FIG 1 seen.

From the EP 0 662 051 B1 (P 7386) a corresponding brake system is known in which a method is used in which the delivery rate of the hydraulic pump is electronically controlled. The pump is controlled by a PWM controller. To estimate the delivery rate, the generator voltage of the motor (motor emf) is measured during the pulse pause times. To meter the Sollradbremsdruck sufficiently accurate during an active pressure build-up, among other things, the most accurate possible adjustment of the pump delivery rate is necessary. Unfortunately, not every pump motor is exactly the same as the other, so that the control with the aid of motor EMF does not yet achieve the required accuracy. To solve this problem, it would be possible in principle to carry out an individual engine calibration for each brake control unit produced, in order to set its speed with the required accuracy over the setpoint value of the engine control via the electrical power control of the motor in conjunction with the measured motor EMF. However, such a factory calibration would be very expensive.

In the older German patent application DE 10 2006 040 127 A1 (P 11502) describes a procedure for calibrating the relationship between pump power setting and speed by means of the motor emf. The motor is also controlled by the motor controller with a pulse width modulated signal with a fixed period. This allows the signal to be divided into two phases: in the time t _AN , a voltage is applied to the terminals of the motor; In the time t _OFF , no voltage is applied to the motor and it rotates due to the moment of inertia of its rotating components. In time t _OFF the engine EMF is measured by means of brake system electronics. The signal motor EMF forms the actual size of the motor control circuit and is regulated by the controller during the brake control operation, as is known, in accordance with the predetermined setpoint voltage. In this way, the motor can be operated at a constant speed because it is linearly related to the generated voltage. To eliminate the design-related deviations of the ratio of speed to motor EMF, proposes the DE 10 2006 040 127 A1 before, after the installation of the brake control unit, ie "in the field", to have this perform an automatic, software-controlled test cycle. In this test cycle, the pump motor is operated in a closed loop for a certain time. In contrast to the control in normal operation, a constant voltage is preset as the set value for the regulator and the duty cycle of the regulation, ie the ratio of pulse duration to the period of the PWM signal, is monitored and, together with empirical results from previously performed suitable ones Laboratory series investigations determined a relationship between speed and motor emf. The advantage of this method is that not every single unit of a series has to be measured. The properties of the pump motor can be independently and automatically determined by the electronic control of the unit in a ready-to-use brake system.

The WO 00/59 762 A1 describes a method for monitoring a pump of a brake system, wherein the pressure pulsations occurring during operation of the pump are determined by means of a pressure sensor. These are evaluated together with temperature signals so that it can be determined whether the pump power has the desired efficiency. Table values are used for this.

DE 102 44 203 A1 shows a method for detecting the rotational speed of a pump, wherein a pressure signal is used to detect the mining activity.

From the WO 97/23 373 A1 is a method for controlling a pump, wherein a noise reduction is effected. The WO 00/02 753 A2 also shows a method for improving brake pressure adjustment and opening an intake valve.

The object of the present invention is now to provide an alternative method for adjusting or determining the pump speed - in particular for determining one or more calibration values - which has a higher accuracy and can likewise be carried out without the use of additional speed sensor technology.

This object is achieved by the method according to claim 1.

According to the method of the invention, a determination is made of the rotational speed of the electric motor used to drive the pump. The motor is preferably a DC electric motor with a commutator whose speed depends on the electrical drive power of the motor. The motor does not include any means for direct measurement of the speed, so for example, no speed sensor. According to the invention, the determination of the rotational speed is carried out on the basis of pressure pulsations of the delivery fluid, in particular in the region of the pump output side hydraulic system. These pressure pulsations are preferably measured at a pressure sensor of the pressure control unit. The method offers besides an increase in accuracy, among other things, the advantage that an additional laboratory series investigation, as in the DE 10 2006 040 127 described, now can be omitted.

Conveniently, the pump motor is integrated in a control loop, which regulates the flow rate or the speed of the pump.

Preferably, the generator voltage of the pump motor is measured and used together with the determined via the pressure pulsations speed for determining one or more calibration values. Here, the or the calibration values are used to establish a functional or tabular relationship between "generator voltage" and "pump speed". This relationship is, in particular, that the numerical ratio between the generator voltage and the speed is formed as the calibration value.

The pump motor is preferably controlled by an electronic control, which in particular generates a pulse width modulated signal (PWM), which determines the speed of the motor. A PWM signal is a periodic square wave signal with a constant period within which the duration of a square pulse is varied. The ratio of pulse to pause is called a duty-cycle. The speed is usually determined by setting the duty cycle, which can take values between zero and one. In the pulse pauses, a measurement of the generator voltage of the motor (motor EMF) is preferably made, which is used as the actual size of the control.

The pressure pulsations determined at the pressure sensor or the pressure actually measured there are preferably measured repeatedly by the electronic control of the pressure control device automatically over a predetermined period of time to determine a pressure curve in a temporal sequence. After that, in particular, an analysis of the pressure curve by the brake control unit takes place, in which case the number of engine revolutions is determined from the identifiable periods or an integral multiple thereof.

The pressure regulating unit preferably comprises a pre-pressure circuit and a plurality of wheel pressure circuits, wherein the pre-pressure circuit can be separated from the wheel pressure circuits by means of at least one separating valve. The pressure sensor for measuring the pressure pulsations is expediently arranged in the region of the pre-pressure circuit. The or the separating valve (s) is / are preferably at least partially opened during the pressure measurement. The method for calibration can thus be carried out particularly advantageously without additional pressure sensors, because it is possible to evaluate the pressure sensor signal of a pressure sensor which is already present in a predominant proportion of ABS control units.

It has been found that the pressure curve has a clearer signal when, as is preferred, the intake valve (s) associated with the wheel pressure circuits, particularly the circuit equipped with a pressure sensor, is / are closed during the acquisition of pressure measurement points. Most preferably, it is provided that only one inlet valve per brake circuit is closed in order to maintain a braking function, albeit limited, during the measurement.

According to a further preferred embodiment of the invention, the above-described pump test carried out for calibration is repeated once or several times after a suitably selected predetermined time or running time of the vehicle in order to take account of inlet or wear effects of the motor pump unit.

The invention further relates to an electronic motor vehicle brake control system having at least one regulated pump for an active brake pressure buildup according to claim 9.

Further preferred embodiments will become apparent from the subclaims and the following description of an embodiment with reference to the figures.

• 1 ein Blockschaltbild eines elektronisch geregelten Bremssystems, in dem das beispielgemäße Verfahren ausgeführt wird und
• 2 einen Messschrieb, welcher das am eingebauten Drucksensor gemessene Signal im zeitlichen Verlauf darstellt.

Show it

• 1 a block diagram of an electronically controlled braking system, in which the exemplary method is carried out and
• 2 a measurement record, which represents the signal measured on the built-in pressure sensor over time.

This in 1 illustrated brake system 1 consists of a hydraulic valve block 2 (HCU) and a firmly connected electronic controller housing 3 (ECU). The brake system comprises two brake circuits I. and II. In the following, only circuit I will be explained in more detail. With tandem master cylinder 4 can brake fluid via hydraulic line in accordance with the brake pedal operation 5 in block 2 be initiated. Via inlet valve 6 and exhaust valve 7 can the pressure in the wheel brake cylinders 8th be set. A measurement of the pre-pressure entered by the driver is by means of an input pressure sensor 16 possible. The brake system shown is otherwise equipped with no other pressure sensors. hydraulic pump 10 is output side with inlet valve 6 and isolation valve 14 connected. pump 10 is operated by a DC electric motor, which is electrically connected to the control unit 3. pressure line 5 leads via a hydraulic line to the upstream side of electrical switching valve 11 and isolation valve 14 , The second output of diverter valve 11 is with the inlet of pump 10 and exhaust valve 7 connected. The second side of isolation valve 14 is with the pump outlet and inlet valve 6 connected.

In the "active pressure build-up" mode, the hydraulic motor is switched on by switching on the electric motor 10 operated, creating hydraulic fluid before inlet valve 6 is encouraged. switching valve 11 is opened in this mode, allowing brake fluid from storage tank 12 to the suction side 13 the pump 10 can flow. isolation valve 14 is essentially closed, but can also be opened slightly for further dosing of the brake pressure. The electric motor of the pump is controlled by the control unit 3 electrically driven with a rectangular voltage signal with variable pulse width (PWM signal).

Inside electronic control unit 3 There is a microprocessor system μP, in which a variety of control and test programs are executed. control unit 3 In addition to internal printing requirements, it can also print requests from external control devices, such as an automatic distance controller 15 (ACC). According to the existing pressure requirement valves are 6 . 7 . 14 and pump 10 so controlled that the requested pressure in the wheel brake cylinders 18 set as accurately as possible.

To do so during a corresponding, not through master cylinder 4 initiated, pressure request to meter the Sollradbremsdruck sufficiently accurate, among other things, an accurate adjustment of the pump delivery is necessary. Unfortunately, due to the manufacturing process, not every pump motor is exactly the same as the other, so that at least one individual engine calibration is required in order to set its speed with the required accuracy over the setpoint value of the engine control via the electrical control of the engine.

Curve 9 in the measurement log in 2 represents the time course of the pre-pressure sensor 16 measured pressure with the pump switched on 10 during the pump calibration test cycle. isolation valve 14 is open. The intake valves to the wheel brake cylinders are closed. As a result, the elastic volume of the wheel brake cylinder from the hydraulic train in which the pressure measurement takes place, decoupled. For comparison, below is curve 9 another pressure curve 17 shown, which indicates the actual pressure curve at the output of the pump. As 2 shows, the pressure measuring points recorded at the admission pressure sensor are sufficient to carry out a determination of the pumping period A. From the pump period results in the number of pump strokes per time. The speed of the pump can be determined in this way in a particularly simple manner with the existing sensors.

Claims (9)

A method for determining the speed of an electric motor, which is part of a motor pump unit (10) in a pressure control device, wherein the speed of the motor and thus the capacity of the pump with the electrical drive power of the motor is related and the speed of the pump by means of a control Changing the drive power is set, wherein further the motor comprises no means for determining the speed includes a determination of the rotational speed by hand pressure pulsations of the conveying fluid and the pressure pulsations are measured in particular on a pressure sensor (16) of the pressure control unit, characterized in that the generator voltage of Pump motor is measured and this is used together with the determined via the pressure pulsations speed for determining one or more calibration values, wherein the calibration or the (e) a functional or tabular relationship between "Generator Span "and" pump speed ", where as a calibration value, the numerical ratio between generator voltage and speed is formed. Method according to Claim 1 , characterized in that the pump motor is driven by an electronic control. Method according to Claim 2 , characterized in that the electronic control for controlling the pump motor generates a pulse width modulated signal. Method according to Claim 3 , characterized in that the generator voltage is used in the pauses between pulses as actual size of the control. Method according to at least one of the preceding claims, characterized in that the pressure measured at the pressure sensor by the electronic control of the pressure control device is automatically measured repeatedly over a predetermined period of time to determine a pressure curve in a time sequence. Method according to Claim 5 , characterized in that the number of engine revolutions is determined from the number of evaluated from the pressure curve periods or an integer multiple thereof. Method according to at least one of the preceding claims, characterized in that the pressure control unit comprises a pre-pressure circuit (5) and a plurality of wheel pressure circuits, that the pre-pressure circuit by means of at least one separating valve (14) is separable from the Radruckkreisen that the pressure sensor is arranged in the region of the pre-pressure circuit and the separating valve (s) is / are at least partially opened during the pressure measurement. Method according to at least one of the preceding claims, characterized in that at least one or all of the wheel pressure circuits associated s / n inlet valve / e (6) is closed / are. Electronic motor vehicle brake control system with at least one regulated pump (10) for an active brake pressure build-up, characterized in that the pump control with the method according to at least one of Claims 1 to 8th is calibrated.

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