DE102007034113A1 - 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, further wherein the motor comprises no means for determining the rotational speed and wherein a determination of the rotational speed on the basis of pressure pulsations of the conveying fluid takes place and the pressure pulsations are measured in particular at a pressure sensor (16) of the pressure control unit. Described is also an electronic vehicle brake control system with at least one regulated pump (10) for an active brake pressure build-up, which uses the above method.

Description

The 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 10, 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 (P 11192), at least comprise a hydraulic pump for the return 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 is usually used with a commutator, which clocked, z. B. is controlled 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 target value of the engine control via the electrical power control of the motor in conjunction with the measured engine EMF. However, such a factory calibration would be very expensive.

In the older German patent application DE 10 2006 040 127 (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 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 The object of the present invention is to provide an alternative Specify a method for adjusting or determining the pump speed, which has a higher accuracy and also without the use of additional speed sensors performed can be.

These The object is achieved by the method according to claim 1 solved.

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 into a control loop, which the Flow rate or the speed of the pump regulates.

Prefers the generator voltage of the pump motor is measured and these together with the determined via the pressure pulsations speed for Determining one or more calibration values used. there If the or the calibration values are used, a functional or tabular relationship between "generator voltage" and "pump speed". This connection is in particular that as a calibration value, the numerical ratio between generator voltage and speed is formed.

Of the Pump motor is preferably of an electronic control controlled, which in particular a pulse width modulated signal (PWM) generated, which determines the speed of the motor. A PWM signal is a periodic square wave signal with constant period inside of which the duration of a rectangular pulse is varied. The relationship from pulse to pause is called a duty-cycle. The speed determination is usually done by setting the duty-cycle, which can take values between zero and one. In the pulse breaks it is preferable to measure the generator voltage of the motor (motor emf) made, which as the actual size of the scheme is used.

The at the pressure sensor determined pressure pulsations or the current there Measured pressure is preferred by the electronic controller the pressure control device automatically over a predetermined Period for determining a pressure curve in a chronological order measured several times. Thereafter, in particular, an analysis of the Pressure curve through the brake control unit, in which the identifiable periods or an integer multiple of them Number of engine revolutions is determined.

Prefers the pressure control unit comprises a pre-pressure circuit and several wheel pressure circuits, wherein the pre-pressure circuit by means of at least one separating valve from the Radruckkreisen is separable. The pressure sensor for measuring the pressure pulsations is expediently in the region of the admission pressure circuit arranged. The separating valve (s) is / are preferably during the pressure measurement at least partially open. The procedure for calibration is thus particularly advantageous without additional pressure sensors executable, because it can be the pressure sensor signal of a pressure sensor be evaluated, which in a predominant proportion ABS control units already exists.

It it has been shown that the pressure curve has a clearer signal, if, as it is preferred, the wheel pressure circuits, in particular the equipped with a pressure sensor circuit, associated inlet valve (s) is closed during the recording of pressure measuring points. All It is particularly preferred that only one inlet valve is provided in each case closed per brake circuit to a braking function, albeit restricted, to maintain during the measurement.

According to one Another preferred embodiment of the invention the pump test described above for calibration after a suitably chosen predetermined time or duration the vehicle repeated once or several times to enema or wear effects of the engine pump unit.

The The invention further relates to an electronic vehicle brake control system with at least one regulated pump for one active Brake pressure assembly according to claim 10.

Further preferred embodiments will be apparent from the dependent claims and the following description of an embodiment Hand of the figures.

It demonstrate

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 in time Velauf.

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 illustrated brake system 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 powered by a DC electric motor, which is electrically connected to the control unit 3 connected is. 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, whereby hydrau likflüssigkeit 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 substantially closed, but can also be opened slightly for further dosage 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, you can also print requests from external control devices, such as: B. 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 when switched pump 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.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102005041556 [0002]
• EP 0662051 B1 [0003]
• - DE 102006040127 [0004, 0004, 0007]

Claims (10)

Method for determining the rotational speed of an electric motor which is part of a motor pump unit ( 10 ) is in a pressure control device, wherein the rotational speed of the motor and thus the capacity of the pump with the electrical drive power of the motor is related and the rotational speed of the pump is adjusted by means of a control by changing the drive power, wherein further the motor is no means for determining the Speed comprises, characterized in that a determination of the rotational speed takes place on the basis of pressure pulsations of the conveying fluid and the pressure pulsations in particular at a pressure sensor ( 16 ) of the pressure control unit are measured. Method according to claim 1, characterized in that that the generator voltage of the pump motor is measured and this together with the pressure pulsations determined Speed used to determine one or more calibration values is the one or more calibration value (s) a functional or tabular relationship between "generator voltage" and "pump speed" manufacture, in particular as the calibration value, the numerical ratio is formed between generator voltage and speed. Method according to claim 1 or 2, characterized that the pump motor is controlled by an electronic control becomes. Method according to claim 3, characterized that the electronic control for controlling the pump motor generates a pulse width modulated signal. Method according to claim 4, characterized in that that the generator voltage in the pauses between pulses as actual size the scheme is used. Method according to at least one of the preceding Claims, characterized in that the pressure sensor measured pressure from the electronic control of the pressure regulator automatically via a predetermined period of time to determine a pressure curve in a time sequence is measured several times. Method according to Claim 6, characterized that the number of engine revolutions from the number of out of the Pressure curve evaluated periods or an integer multiple it is determined. Method according to at least one of the preceding claims, characterized in that the pressure control unit a pre-pressure circuit ( 5 ) and a plurality of wheel pressure circuits, that the admission pressure circuit by means of at least one isolation valve ( 14 ) is separable from the Radruckkreisen that the pressure sensor is arranged in the region of the pre-pressure circuit and that the or the separating valve (s) during the pressure measurement is at least partially open / are. 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 vehicle brake control system with at least one regulated pump ( 10 ) for an active brake pressure build-up, characterized in that the pump control is calibrated with the method according to at least one of claims 1 to 9.