WO2012104168A1

WO2012104168A1 - Method and assembly for controlling a vacuum pump

Info

Publication number: WO2012104168A1
Application number: PCT/EP2012/051010
Authority: WO
Inventors: Alexander Kalbeck
Original assignee: Continental Automotive Gmbh
Priority date: 2011-01-31
Filing date: 2012-01-24
Publication date: 2012-08-09
Also published as: DE102011088975A1

Abstract

The invention relates to a method and an assembly for controlling an electric vacuum pump for a vehicle. According to said method: a saturation point is identified and when the vacuum pump is active a saturation pressure range (SD) of a predefinable width can be defined; the actual prevailing negative pressure produced by the vacuum pump is continuously determined; a saturation point is identified when the prevailing negative pressure lies in the saturation pressure range (SD) and does not move outside said range over a predeterminable period of time (tx) and when a saturation point is identified, the vacuum pump is deactivated.

Description

Method and arrangement for controlling a vacuum pump

The invention relates to a method and a

Arrangement for controlling a vacuum electric pump for a vehicle, wherein a saturation detection takes place.

From the prior art electric vacuum pump are known in vehicles (cars), the conventional methods (vacuum by engine intake in gasoline

Motors or mechanical vacuum pumps for diesel engines). This vacuum, or more precisely this vacuum, is used in vehicles, among others. to

Brake force support or reinforcement needed.

For energy saving reasons as well as for the sake of

Lifespan, the electric vacuum pumps over the actual existing negative pressure in

Controlled vacuum pressure vessel. If the negative pressure (negative relative to ambient pressure) above a certain upper threshold becomes the pump

activated. When falling below a vacuum threshold, ie a sufficiently large vacuum for the

Brake force support, the pump is then deactivated. Such switch-on thresholds are generally in a range of about -600 hPa, switch-off thresholds in a range of about -700 hPa. Such an arrangement is for example from WO

2008/003547 AI known, in which the thresholds are selected speed-dependent.

However, if you m m heights, where there is a lower ambient pressure, so the pump reaches only a lower maximum negative pressure relative to the ambient pressure. This can cause the lower turn-off threshold not

is reached and therefore the pump runs permanently. However, this comes at the expense of energy consumption and lifetime.

There are known solutions that have a saturation detection. In this case, the reaching of a saturation of the negative pressure is detected. This indicates that the pump has delivered its maximum vacuum performance. If the saturation is detected, this leads to a deactivation of the pump.

Will then again a negative pressure, the by one

configurable value is higher than that

Detected cut-off value, detected, the pump is reactivated and the saturation detection restarts. To detect the saturation, one considers the gradient of the negative pressure. Remains within a configurable time under one

configurable threshold, this is considered to be saturation detection.

It is an object of the invention, a control including saturation detection of the type mentioned

to improve so that even under changing ambient pressures a more reliable

Saturation detection takes place.

This object is achieved for a method or an arrangement by the features of the independent claims.

It is a saturation range with selectable mean and selectable width predetermined. As soon as the

For example, in a vacuum vessel prevailing, generated by the vacuum pump vacuum is within this pressure range, it is subsequently determined during a predetermined period of time, whether the actual negative pressure within the

Saturation range remains. If this is the case, a saturation is detected and the vacuum pump

switched off, because a stay in the

Saturation range indicates that the vacuum pump is no longer able to increase the negative pressure and exceed the upper threshold of the saturation range.

According to embodiments of the invention, a

improved adaptation to changing external

Pressure conditions take place in that the mean pressure value of the saturation pressure range is variably predetermined, and thereby

- Based on a predefinable initial pressure value of the mean pressure value of the saturation pressure range with running vacuum pump within a predetermined period t is continuously determined whether the

actually prevailing negative pressure the saturation pressure range to a higher or lower

Negative pressure goes out,

- When leaving the saturation pressure range to a higher negative pressure value, the mean pressure value of the saturation pressure range increased by a predetermined negative pressure value and on leaving the

Saturation pressure range to a lower

Low pressure value the mean pressure value of the

Saturation pressure range to a predetermined

Low pressure value is lowered and that

- After each change in the mean pressure value of the saturation pressure range, the time t new

is started.

Thus, the value range of the saturation pressure range becomes indirectly to the prevailing outer Adjusted pressure conditions, using as a criterion

is used, whether with the pump running

actually prevailing negative pressure leaves the pressure range up or down. The values of the saturation pressure range are re-selected depending on the direction of this exit.

According to an advantageous further embodiment of the invention, this can be done in such a way that the average pressure value of the saturation pressure range after leaving the same by half the value of

Difference of the highest and the lowest pressure value of the saturation pressure range is changed. According to an advantageous further embodiment of the

This can be done in such a way that the average pressure value of the saturation pressure range is changed up or down after leaving the same by the minimum measurable pressure change value if the pressure value lies above or below the saturation range in the current measurement.

Thus, starting from an initial value from which the saturation detection is to be started (for example, - 400 hPa), the threshold is set symmetrically to the starting value (for example, + -25 hPa). Exceeds or falls below the

actual negative pressure value now within the configured time (eg 3s) these thresholds, then the mean value for the saturation detection

corresponding to the initial value by +25 (at

Exceeded) or -25 (when falling below). There, the same thresholds are revalued accordingly.

Will this process successively at each over or

If this is undershot, a sliding threshold band for saturation detection, which approaches the final saturation value, is obtained at low computation and memory outlay. If the actual negative pressure value remains within the band for the defined time, the saturation is recognized.

Advantageously, this is also one for electronic microcontroller systems

optimized method typically used to control such systems.

According to a further embodiment of the invention, the configurable time for saturation detection, in which the actual negative pressure within the

Threshold band must be variably changed with the current average. This is to happen in the way that, the farther the mean p_mean_sat of

"normal" shutdown p_vac_off_th is removed, the necessary time for the saturation detection is increased. If the saturation threshold band were in the range of, for example, -650 hPa, then a detection time of, for example, 3 s would be selected (very close to a "normal switch-off point of -700 hPa).

If the threshold band were in the range of -500hPa, e.g. a time of 4.5s is needed, with a threshold band in the range of -400hPa then a value of e.g. 6s.

The time dependency can be stored via a function (for example linear dependency, quadratic, exponential etc.) or also via a characteristic map.

This mechanism improves the safety of

Saturation detection insofar as that at a

Saturation detection in areas close to

"normal" shut-off point, a certain error is allowed because the brake force gain is only minimally affected by the deviation. For a saturation detection in areas where one

However, a more pronounced prolonged test takes place in order to compensate for any influences from the environment (for example brake pedal depressed, voltage fluctuations, etc.).

According to a further embodiment of the invention can also be the size of the saturation band depending on the expected saturation value similar to the threshold time. Preferably, such that at lower negative pressure, a larger threshold is allowed for systems where the pumping a larger change in the vacuum signal at larger

Causes air mass movement. Possibly. can also respect safer detection of saturation, a larger band is allowed at greater negative pressure.

According to a further embodiment of the invention, the threshold algorithm as described above

additionally combined with a gradient comparison (similar to those known from the prior art). That If a gradient of the negative pressure signal that is above a definable threshold (possibly also dependent on the current mean negative pressure value p_mean_sat) is detected, although the actual value lies within the selected band, the saturation detection time counter is reset and the condition must be after the detected Gradients are again constant for the swelling time. The should make it possible, without further vehicle information events in the

Braking system (eg depressed brake pedal) too

identify and saturation detection

to make more reliable.

In contrast to the prior art will be here

but not a filtered, longer-term one

Signal waveform detected, but a short event. According to a further embodiment of the invention, the modified by the saturation detection

Switch-on point p_vac_on_th, after a saturation has already been detected and then the pump was deactivated, be reset to the initial value as soon as the detected negative pressure falls below a threshold p_sat_deactivate_th as follows: p_sat_deactivate_th = p_vac_on_th - p_vac_on_addon - 2 * saturation threshold

This should take into account that at a detected saturation at a higher altitude, where a relative

"high" new turn-on point has been selected (e.g., - 450hPa), which will be reset accordingly as soon as a downhill in which the relative pressure increases in magnitude takes place (e.g., back to -600hPa).

As a rule, the pump would be automatically reactivated and thus the thresholds

updated.

Overall, the following advantages result from the

Invention:

a) Threshold use is more stable against short-term changes in the noise of the sensors, but more sensitive and more accurate in the individual measurements of the negative pressure value. b) The algorithm allows an adaptation of the

Detection behavior as a function of the distance of the current negative pressure value of the "normal" shutdown and thus increasing the security of the algorithm. c) The algorithm allows in combination with the

Gradient checking as well as the detection of fast external events such as Press the brake pedal. d) An adaptation of the threshold values can be carried out even after detection of the saturation, in order thus to recognize new environmental situations.

An embodiment of the invention will be explained in more detail with reference to the drawing. Show it:

FIG. 1 is a graph illustrating the actual negative vacuum produced by a vacuum pump over time, with a pressure trace having a saturation pressure region down, i.e., a pressure gradient. to higher oppressions, leaves and

2 shows a representation according to Figure 1 with a different pressure curve and detection of saturation.

FIG. 1 shows a negative pressure curve D over time t. It is a negative pressure D, the one not indicated vacuum pump

For example, in a pressure vessel relative to

Ambient pressure generated. The actually producible negative pressure D depends on various boundary conditions, in particular of

Ambient pressure. The lower it is (for example, at high altitudes, the lower is the maximum vacuum that can be generated by the vacuum pump.) Then there is a so-called saturation, in which the pump runs, but can not build up any further increased negative pressure Situation is to be avoided especially for reasons of energy saving.

The invention therefore aims at the most flexible detection of such saturation.

On the one hand, a saturation pressure range SD is preset with an upper limit SDo and a lower limit SDu. In the example according to FIG. 1, this saturation pressure range SD is between 525 and 575 hPa.

Saturation is detected when the actual vacuum curve D does not leave the saturation pressure range SD during a time period tx whose length can be predetermined and / or varied.

In the illustration of Figure 1 leaves the

Subpressure D is the saturation pressure range SD for

Zeitpumkt tl. During the time tx, the pressure D remains outside the saturation pressure range SD, so that no saturation is detected during this period. In order to achieve a more flexible adaptation to the ambient pressure, the pressure range may preferably

be displaceable. Starting from a predefinable initial pressure value of the mean pressure value of the saturation pressure range, which in the example in accordance with FIG. 1 is 550 hPa, it is continuously determined within a predefinable time interval tx when the vacuum pump is running whether the actually prevailing negative pressure satisfies the saturation pressure. Pressure range leaves up or down. In the example according to FIG. 1, this is the case at the time t 1.

Then, when leaving the saturation pressure range upward, the average pressure value of the

Saturation pressure range to a predetermined

Pressure value increased and when leaving the

Saturation pressure range down the middle

Pressure value of the saturation pressure range lowered by a predetermined pressure value and then the

Time interval tx restarted.

In the example according to FIG. 1, therefore, the saturation pressure region is lowered at the point in time t 1 in a manner not shown in the figure. H. to higher

Suppress down.

In this case, preferably, the mean pressure value of the saturation ^¬ pressure range for a leave the same can be changed by half the value of the difference of the uppermost and the lowest pressure value of the saturation pressure range. In the example according to FIG. 1, a shift of the mean pressure value of the saturation pressure range from 550 hPa to 575 hPa would therefore take place.

Preferably, the saturation pressure range between a minimum (in the example of Figure 1 400 hPa) and a maximum (in the example of Figure 1 700 hPa) is displaceable.

In the now shifted pressure range, it is again determined whether the negative pressure D leaves the pressure range SD during the time interval tx. If this is the case, the print area is again shifted.

However, if the actual negative pressure value remains within the time tx during the time period

Saturation pressure range, so a saturation is detected.

This is indicated by way of example in FIG. According to this example, the value of the actual negative pressure during the period tx remains within the saturation pressure range SD. This indicates that the vacuum pump is unable to produce an even higher vacuum and saturation detected and shut off the pump to save the pump and save energy.

The duration of the time period tx can advantageously be chosen to be variable and to be greater, the larger the

Pressure difference between the mean pressure value of the saturation pressure range and a predetermined standard Abschaltdruckwert is.

Claims

Patent claims

A method of controlling an electric vacuum pump for a vehicle, wherein a saturation detection is performed and wherein when the vacuum pump is activated

a saturation pressure range (SD) of predeterminable width can be predetermined,

- the actual prevailing negative pressure generated by the vacuum pump is continuously detected,

- A saturation detection then takes place when the prevailing negative pressure during a predetermined

Time duration (tx) in the saturation pressure range (SD) and does not leave this, and at a

Saturation detection the vacuum pump is turned off.

2. The method according to claim 1, characterized in that the mean pressure value of the saturation pressure range (SD) is variably predetermined.

3. The method according to claim 2, characterized in that

- Starting from a predetermined initial pressure value of the mean pressure value of the saturation pressure range

(SD) with running vacuum pump within a

predetermined period (tx) is continuously determined whether the actual prevailing negative pressure the Saturation pressure range to a higher or higher

leaves lower negative pressure,

- When leaving the saturation pressure range to a higher negative pressure value toward the mean pressure value of the saturation pressure range (SD) increased by a predetermined negative pressure value and when leaving the saturation pressure range to a lower

Low pressure value the mean pressure value of the

Saturation pressure range (SD) is lowered by a predetermined negative pressure value and that

- after each change in the mean pressure value of the saturation pressure range, the time interval (tx) is restarted.

4. The method according to claim 3, characterized in that the mean pressure value of the saturation pressure range (SD) after leaving the same by half the value of the difference of the uppermost (SDo) and the lowest negative pressure value (SDu) of the saturation pressure range is changed.

5. The method according to claim 3, characterized in that the mean pressure value of the saturation pressure range (SD) after leaving the same successively by a minimum detectable

Pressure change value is changed until the determined pressure value is again within the saturation pressure range.

6. The method according to any one of claims 1 to 5, characterized in that the predeterminable period of time (tx) is variable and the greater is selected, the greater the pressure difference between the mean pressure value of the saturation pressure range and a predefinable

Default cutoff pressure value is.

7. The method according to any one of claims 1 to 6, characterized in that the width of the saturation pressure range (SD) is variable and the greater is selected, the greater the pressure difference between the mean pressure value of the saturation pressure range and a predetermined standard Abschaltdruckwert is.

8. The method according to any one of claims 1 to 6, characterized in that the width of the saturation pressure range (SD) is variable and the smaller is selected, the greater the pressure difference between the mean pressure value of the saturation pressure range and a predetermined standard Abschaltdruckwert is.

9. The method according to any one of claims 1 to 8, characterized in that the gradient of the change of the actual pressure prevailing is determined and that, if the gradient is above a predetermined

Threshold is, the predetermined period of time is restarted.

10. The method according to claim 4, characterized in that the modified mean pressure value of

Saturation pressure range, after a saturation has already been detected and then the pump has been deactivated, is reset to the initial mean pressure value as soon as the detected negative pressure falls below a threshold p_sat_deactivate_th as follows: p_sat_deactivate_th = p_vac_on_th - p_vac_on_addon - 2 * saturation threshold.

11. Arrangement for controlling a vacuum pump for a vehicle with saturation detection with a

Control electronics and at least one in a vacuum pressure vessel or in a vacuum circuit

provided pressure sensor, wherein the

Control electronics with activated vacuum pump

activates a saturation pressure range (SD) of predeterminable width,

- the actual prevailing, generated by the vacuum pump vacuum continuously determined by means of the pressure sensor,

- performs a saturation detection when the prevailing negative pressure during a predetermined

Time duration (tx) is in the pressure range and does not leave this, and the vacuum pump switches off.

12. Arrangement according to claim 11, characterized in that the control electronics

variably selects the mean pressure value of the saturation pressure range (SD),

- Starting from a predefinable initial pressure value of the mean pressure value of the saturation pressure range (SD) with running vacuum pump within a

predeterminable time interval (tx) by means of the pressure sensor continuously determines whether the actual prevailing vacuum leaves the saturation pressure range (SD) to a higher or lower negative pressure,

- When leaving the saturation pressure range (SD) to a higher negative pressure value towards the mean pressure value of the saturation pressure range increased by a predetermined negative pressure value and at a

Leaving the saturation pressure range to a lower negative pressure value lowers the mean pressure value of the saturation pressure range by a predeterminable negative pressure value and

- after each change in the mean pressure value of the saturation pressure range (SD) restarts the time period (tx).