Method for optimizing the pressure setting accuracy

Abstract

In a method for optimizing the pressure setting accuracy, a hydraulic pressure is built up according to a pressure requirement of a hydraulic pump, and overflow control is performed using an analog-controlling hydraulic valve and a known control characteristic curve of the analog-controlling hydraulic valve, which overflow control counteracts a pressure build-up produced by the hydraulic pump that exceeds the pressure requirement. In addition to the known control characteristic curve of the analog-controlling hydraulic valve, at least one additional valve characteristic is taken into account for the overflow control.

Claims

1. A method for optimizing a pressure setting accuracy, wherein a hydraulic pressure is built up by a hydraulic pump in accordance with a pressure demand and wherein, using an analog-regulation hydraulic valve and a known actuation characteristic curve of the analog-regulation hydraulic valve, overflow regulation is performed which counteracts a pressure build-up, generated by the hydraulic pump, which goes beyond the pressure demand wherein in addition to the known actuation characteristic curve of the analog-regulation hydraulic valve, at least an overflow characteristic map is taken into consideration for the overflow regulation.

2. The method as claimed in claim 1, wherein the overflow characteristic map represents an overflow behavior of a hydraulic valve of averaged characteristics.

3. The method as claimed in claim 1, wherein the overflow characteristic map is modified on a valve-specific basis by the known actuation characteristic curve.

4. A method for optimizing a pressure setting accuracy, wherein a hydraulic pressure is built up by a hydraulic pump in accordance with a pressure demand and wherein, using an analog-regulation hydraulic valve and a known actuation characteristic curve of the analog-regulation hydraulic valve, overflow regulation is performed which counteracts a pressure build-up, generated by the hydraulic pump, which goes beyond the pressure demand wherein in addition to the known actuation characteristic curve of the analog-regulation hydraulic valve, at least one further valve characteristic is taken into consideration for the overflow regulation, wherein the known actuation characteristic curve is a valve-specific actuation characteristic curve.

5. The method as claimed in claim 1, wherein the known actuation characteristic curve is determined after the connection of the hydraulic valve into a hydraulic or electrohydraulic vehicle brake system.

6. The method as claimed in claim 1, wherein the analog-regulation hydraulic valve which is used to perform the overflow regulation is a cut-off valve of a hydraulic or electrohydraulic brake system.

7. A method for optimizing a pressure setting accuracy, wherein a hydraulic pressure is built up by a hydraulic pump in accordance with a pressure demand and wherein, using an analog-regulation hydraulic valve and a known actuation characteristic curve of the analog-regulation hydraulic valve, overflow regulation is performed which counteracts a pressure build-up, generated by the hydraulic pump, which goes beyond the pressure demand wherein in addition to the known actuation characteristic curve of the analog-regulation hydraulic valve, at least one further valve characteristic is taken into consideration for the overflow regulation, wherein an overflow characteristic map represents a regulation current versus a hydraulic fluid volume flow rate as a function of a pressure difference prevailing across the hydraulic valve.

8. The method as claimed in claim 7, wherein a quantitative modification of the overflow characteristic map increases with the value of the deviation of an opening current determined on a valve-specific basis in the case of a pressure difference of substantially 0 bar from the opening current of a hydraulic valve of averaged characteristics, or increases with the value of the deviation of the closing current determined on a valve-specific basis in the case of a pressure difference of substantially 0 bar from the closing current of a hydraulic valve of averaged characteristics.

9. The method as claimed in claim 8, wherein, if a closing current determined on a valve-specific basis in the case of a pressure difference of substantially 0 bar prevailing across the hydraulic valve is less than a closing current determined in the case of a pressure difference of substantially 0 bar prevailing across a hydraulic valve of averaged characteristics, a modification is performed for a reduction of the regulating current versus the hydraulic fluid volume flow rate in the overflow characteristic map.

10. The method as claimed in claim 8, wherein, if a closing current determined on a valve-specific basis in the case of a pressure difference of substantially 0 bar prevailing across the hydraulic valve is greater than a closing current determined in the case of a pressure difference of substantially 0 bar prevailing across a hydraulic valve of averaged characteristics, a modification is performed for an increase of the regulation current versus the hydraulic fluid volume flow rate in the overflow characteristic map.

11. A method for optimizing a pressure setting accuracy, wherein a hydraulic pressure is built up by a hydraulic pump in accordance with a pressure demand and wherein, using an analog-regulation hydraulic valve and a known actuation characteristic curve of the analog-regulation hydraulic valve, overflow regulation is performed which counteracts a pressure build-up, generated by the hydraulic pump, which goes beyond the pressure demand wherein in addition to the known actuation characteristic curve of the analog-regulation hydraulic valve, at least one further valve characteristic is taken into consideration for the overflow regulation, wherein the known actuation characteristic curve is determined by a valve plunger position detection method.

12. A hydraulic or electrohydraulic vehicle brake system comprising: at least one master cylinder for the supply of hydraulic fluid, at least one inlet valve for the admission of a pressure into at least one wheel brake cylinder assigned to a vehicle brake and at least one outlet valve for the release of the pressure from the at least one wheel brake cylinder assigned to a vehicle brake, at least one hydraulic pump, at least one electronic control and regulation unit and at least one analog-regulation cut-off valve, wherein the hydraulic pump builds up a hydraulic pressure in accordance with a pressure demand from the electronic control and regulation unit, and the electronic control and regulation unit, using the cut-off valve and a stored actuation characteristic curve of the cut-off valve, performs overflow regulation which counteracts a pressure build-up, generated by the hydraulic pump, which goes beyond the pressure demand, wherein, for the overflow regulation, the electronic control and regulation unit takes into consideration not only the stored actuation characteristic curve of the cut-off valve but also an overflow characteristic map of the cut-off valve.

13. The vehicle brake system as claimed in claim 12, wherein, for the overflow regulation, the electronic control and regulation unit takes into consideration a stored overflow characteristic map as a further valve characteristic of the cut-off valve.

14. The vehicle brake system as claimed in claim 12, wherein the electronic control and regulation unit modifies the stored overflow characteristic map on a valve-specific basis as a function of the stored actuation characteristic curve.

15. The vehicle brake system as claimed in claim 12, wherein the electronic control and regulation unit determines and/or corrects the stored actuation characteristic curve of the cut-off valve repeatedly during operation.

16. Use of the method as claimed in claim 1 for pressure regulation in a system for inter-vehicle distance regulation and speed regulation of a motor vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further preferred embodiments will emerge from the subclaims and from the following description of an exemplary embodiment on the basis of figures, in which:

(2) FIG. 1 shows actuation characteristic curves of three hydraulic valves with different behavior,

(3) FIG. 2 shows an overflow characteristic map of a hydraulic valve of average characteristics, with a valve-specific modification at low pressures, and

(4) FIG. 3 shows a relationship between the valve-specific modification of an overflow characteristic map of a hydraulic valve of averaged characteristics and the valve-specific actuation characteristic curve of a hydraulic valve.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 illustrates, by way of example, the closing current I.sub.0 versus a pressure difference p prevailing across a hydraulic valve for three different individual hydraulic valves (not illustrated). Characteristic curves 11, 12 and 13 are the valve-specific actuation characteristic curves of the three hydraulic valves and have been determined by means of a valve plunger position detection method directly after the connection of the hydraulic valves into a hydraulic or electrohydraulic vehicle brake system. Characteristic curve 11 has the lowest closing current I.sub.0,1 at a prevailing pressure difference p=0, characteristic curve 12 has an average closing current I.sub.0,2>I.sub.0,1 at p=0, and characteristic curve 13 has a higher-than-average closing current I.sub.0,3>I.sub.0,2 at p=0. With increasing pressure difference p between valve inlet and valve outlet, the behaviors of the three hydraulic valves converge on one another to an increasing extent. From valve-specific actuation characteristic curves 11, 12 and 13, the pressure-dependent opening and closing points of the three hydraulic valves are known. Valve-specific actuation characteristic curves 11, 12 and 13 also allow statements to be made regarding the valve-specific overflow behavior of the associated hydraulic valves.

(6) FIG. 2 shows, by way of example, an overflow characteristic map of a hydraulic valve of averaged characteristics (not illustrated), the overflow characteristic map being composed of graphs 21, 22, 23 and 24. The figure shows the pressure-dependent hydraulic fluid volume flow rate Q as a function of an offset current I.sub.off which is selected in a pressure-dependent manner and which has the regulation current I.sub.R added thereto in directional fashion in the case of different pressure differences p.sub.1<p.sub.2<p.sub.3<p.sub.4. It can be seen from the overflow characteristic map that a higher offset current I.sub.off is required to achieve a certain hydraulic fluid volume flow rate Q in the case of large pressure differences than in the case of low pressures. Since graphs 21, 22, 23 and 24 illustrate the overflow behavior of a hydraulic valve of averaged characteristics, that is to say an average hydraulic valve, said graphs correspond to the behavior of the hydraulic valve characterized by actuation characteristic curve 12 in FIG. 1. In order to prevent an excessively high or excessively low hydraulic fluid volume flow rate Q from passing through the hydraulic valve in the case of deviating valve characteristics, the overflow characteristic map is modified in valve-specific fashion as a function of the actuation characteristic curves shown by way of example in FIG. 1. Graphs 25 and 26, illustrated by dashed lines, show an individual modification of said type for a hydraulic valve with relatively low closing current I.sub.0, as illustrated for example by actuation characteristic curve 11 in FIG. 1. Since a hydraulic valve would, with an actuation characteristic curve 11 (FIG. 1) and a closing current I.sub.0,1 (FIG. 1), allow too little hydraulic fluid to flow out during the course of unmodified overflow regulation, the overflow characteristic map is consequently modified for a hydraulic valve of said type such that graphs 21 and 22 are shifted toward lower offset currents I. This modification leads, according to the example, to overflow regulation of the hydraulic valve as per the graphs 25 and 26, illustrated by dashed lines, at pressures p.sub.1 and p.sub.2. Owing to the fact that even different hydraulic valves exhibit increasingly similar behavior at high pressures, a modification is not necessary at high pressures (p.sub.3, p.sub.4) in this exemplary embodiment. Graphs 23 and 24 thus do not need to be modified for precise regulation.

(7) FIG. 3 shows, by way of example, the relationship between the modification of the overflow characteristic map and the determined opening current I.sub.0 of a hydraulic valve in the case of a pressure difference p=0 in the form of a linear relationship 31. I.sub.off indicates the quantitative modification of the offset current I.sub.off as a function of the closing current Io in the case of a pressure difference p=0. In this exemplary embodiment, the closing current I.sub.0,2 corresponds to an average hydraulic valve, of averaged characteristics. The closing current I.sub.0,3 corresponds to the closing current of a hydraulic valve whose closing current I.sub.0 is higher than average. The higher the closing current I.sub.0 of a hydraulic valve is, the greater is the extent to which the overflow characteristic map by which the hydraulic valve is regulated is modified toward higher offset currents I. By contrast, the closing current I.sub.0,1 represents a below-average closing current I.sub.0, which leads to a reduction of the corresponding pressure-dependent offset current I.sub.off of the hydraulic valve in the overflow characteristic map that is used. Thus, in this exemplary embodiment, use is made of a linear relationship between the valve-specific quantitative modification of the overflow characteristic map and the valve-specific closing current I.sub.0 in the case of a pressure difference of p=0.