WO2020049144A1

WO2020049144A1 - Method for monitoring the function, in particular for monitoring the tightness, of a braking apparatus, and a braking apparatus and a vehicle

Info

Publication number: WO2020049144A1
Application number: PCT/EP2019/073806
Authority: WO
Inventors: Alexander Fuchs
Original assignee: Knorr-Bremse Systeme für Nutzfahrzeuge GmbH
Priority date: 2018-09-07
Filing date: 2019-09-06
Publication date: 2020-03-12
Also published as: DE102018121859A1

Abstract

A method (1) for monitoring the function, in particular for monitoring the tightness, of a braking apparatus (201), having the following steps: a) evaluating (step 101) a sensor signal (6) for capturing an internal pressure in a pressure chamber, in particular a caliper interior (206) or a plunger chamber (209), of the braking apparatus (201) during a period, wherein a plurality of data points (300, 400) of the internal pressure are captured during the period at staggered times, and wherein the period comprises at least one braking operation with at least one applied operating state and one released operating state; b) determining a first comparison value (step 103) from two data points, wherein a first data point is selected in a period of the sensor signal in which the braking apparatus is in the applied operating state, and wherein a second data point is selected in a period of the sensor signal in which the braking apparatus is in the released operating state; c) comparing the first comparison value (step 104) with a first limit value while determining a leakage, and d) outputting (5) a warning signal or a change in a count value if the comparison value reaches, exceeds or undershoots the limit value; and a braking apparatus (201) and a vehicle.

Description

DESCRIPTION

Function monitoring method, in particular for

Leakage monitoring, a braking device and a braking device, and a vehicle

The invention relates to a method for function monitoring, in particular for tightness monitoring, a braking device and a braking device, and a vehicle comprising several of these braking devices.

Field failures due to corroded mechanical parts of a braking device nowadays occur when the sealing effect of a braking device fails. The failure of the sealing effect can be caused by mechanical or thermal damage to the seals. If this dysfunctional seal is not recognized at an early stage, moisture can penetrate into the brake and lead to subsequent errors that impair the function of the brake or can result in a complete replacement of the application unit.

For example, progressive corrosion of the mechanical parts of the adjusting unit can lead to failure of the latter. In the most serious case, this would have the consequence, if the error was not discovered beforehand, that the brake adjustment function was interrupted and the clearance between the pads and the disk increased over the nominally specified, permissible range. An increased clearance can lead to reduced braking performance and, for example, to skewing.

Monitoring the seals is therefore an important condition monitor. Damaged or defective seals result in moisture entering the interior of the brakes and possibly in the failure of electronic parts or in the corrosion of internal mechanical parts.

Based on the above considerations, the object of the present invention is therefore a method for function monitoring, in particular with regard to the tightness or functionality of the seals used within the braking device, to provide a braking device.

The present invention achieves this object by providing a method with the features of claim 1 and by providing one

Braking device with the features of claim 10.

A method for function monitoring, in particular for tightness monitoring, of a braking device of a vehicle is preferably used for monitoring a pneumatic disc brake of a wheel of a vehicle, for example a truck. Due to the construction, such braking devices have a pneumatic and / or hydraulic pressure chamber.

Further structural details of a variant of a pneumatic

Brake device in the form of a pneumatic disc brake can be found in DE 10 2016 1 17 593 A1, to which the present invention relates.

The aforementioned method has at least the following steps:

In a first step a) there is an evaluation of a sensor signal for detecting an internal pressure of a pressure chamber of the braking device during a period of time, with a plurality of data points of the internal jerk being recorded at different times during the period and the period of time comprising at least one braking with at least one applied and one released Operating status includes.

This internal pressure prevails in the aforementioned pressure chamber of the braking device, also called the pressure modulator, and can be several millibars, for example 5-50 millibars. The pressure room can e.g. act a caliper interior or tappet space within the braking device.

The braking device according to the invention can be a disc brake or a drum brake, although a disc brake is preferred. A caliper brake in particular is a preferred embodiment. The disc brake can have a brake caliper and can, but need not, have a brake carrier. A pneumatically or possibly also electromotively actuated brake cylinder can be connected to the brake caliper and a caliper interior delimited by the caliper, which can be flanged to the caliper. The interior of the saddle can be designed as the aforementioned pressure space. Optionally, a plunger space, which is arranged adjacent to the caliper interior and in which a brake plunger is guided, can be designed as a pressure space.

Optionally, however, the brake cylinder, e.g. in the

Design of a pneumatic, electric motor or hydraulic

Brake device are monitored, which is known to be acted upon by compressed air.

The volume of said pressure space changes preferably in proportion to a stroke movement of a brake tappet of the brake device.

The sensor signal comprises a chronological sequence of a plurality of data points. It can be a recording of a sensor signal over a certain period of time or a continuous sensor signal that is only recorded and possibly evaluated by a measuring and / or evaluation unit in a specific period or time window. There are several in time

successive data points, in particular data points equivalent to pressure, which were recorded within a time window or time interval. During this time window, at least one braking operation is carried out with the braking device, so that the braking device on the one hand in the released operating state and on the other hand in the locked operating state during the determination of the

Sensor signal is present.

In a step b), a first comparison value is determined from at least two data points of the sensor signal. The first of the at least two data points is determined, in particular selected, in such a way that it is located in a time segment of the Time window of the sensor signal is in which the braking device is in the applied operating state.

This first data point corresponds to an internal pressure in the locked operating state of the braking device and the second data point corresponds to an internal pressure in the released operating state of the braking device.

The comparison value itself can, for example, be the difference between the two

Data points are determined. However, there are also other variants, e.g.

Quotient formation of both data points or the like, possible.

The determined first comparison value is compared in a step c) with a first limit value. Depending on the selection of the comparison value and the limit value, if the limit value is reached, exceeded or undershot, the leakage is determined, preferably a leak in the pressure chamber, e.g. if the internal pressure is too low, especially in the closed operating mode.

If a leak is determined, a warning signal is issued or a count is changed.

This count can also be compared to a limit. If the count exceeds the limit, e.g. if a leak is detected three times in succession, a warning can be issued.

The method is preferably used to monitor the tightness of a pneumatic disc brake with a pneumatic brake cylinder, but it can

Function monitoring also other function variables, e.g. the temperature of the braking device, in particular the so-called saddle temperature, based on the

Monitor the determination of the pressure signal without the additional use of a temperature sensor.

The above-mentioned method can primarily be used to specifically check the

Functionality eg a caliper seal of a brake caliper of a disc brake as well as from various other interfaces. The method can be used to detect a dysfunctional seal or, optionally, a gradual degradation of the sealing effect and prevent consequential damage such as corrosion caused by moisture.

As a result of the method, complex and expensive repair measures such as e.g. the replacement of a complete application unit of a braking device can be avoided and replaced by an intervention with significantly less maintenance effort, for example a single replacement of one or more seals of the braking device, which significantly reduces the service costs.

The safety of the disc brake is also increased even further, as an impending failure of mechanical parts due to direct corrosion

Sensation is prevented.

Advantages also result from the targeted control of maintenance or

Workshop visits (predictive maintenance) as well as increasing the safety of the brake device by monitoring the sealing effect of the brake caliper and

Brake cylinder seals.

Further advantageous embodiments of the invention are the subject of

Subclaims.

To detect a gradual leak, the method can have a further step e), a second comparison value being determined from a chronological sequence of data points in the closed operating mode and being compared with a second limit value.

By supplementing the method with step e), a possible complete saddle leak and / or dysfunctionality of the seals can be prevented, since this is recognized during the gradual progress of a leak. This results in advantages for the maintenance control, since degrading Seals are recognized in good time and moisture ingress is prevented.

When determining this second comparison value, only data points are used which were recorded within a time period in which the braking device is in a locked operating mode. It is considered whether a decrease in the values of the data points within the

Application time, in particular a drop in the internal pressure during application. This drop can be used as the second comparison value, e.g. as a gradient.

With each braking operation of the braking device, the determination of the data points, that is to say both the point in time for recording the sensor signal and the length of the sensor signal, can be identical to a previous braking operation or a previous braking operation in which the method according to the invention can always be newly initiated. his. The same also applies advantageously to the determination of the two data points to determine the first comparison value and to the sequence of data points to determine the second comparison value.

It is also advantageous if a warning signal is output if the count value has reached a certain value in step d). This means that a measurement does not automatically lead to a warning message, but may be followed by a subsequent one

Measurement during renewed braking verified and, if necessary, the count can be reset to zero.

The first and / or the second data point can be an average of a plurality of chronologically successive data points, in each case in an operating state, that is to say released or locked.

The second comparison value can be formed by forming a moving average value from the chronological sequence of data points in the clamped operating state. The second comparison value can alternatively or additionally be carried out by a recursive

Procedure from a chronological sequence of data points in the clamped

Operating mode can be determined.

The method for function monitoring, in particular for tightness monitoring, can advantageously be combined with further method features and / or supplemented by further monitored functions. In an optional step f), by comparing the first and / or the second determined comparison values of several braking devices of a vehicle, the stronger temperature development of one of the braking devices, in particular the saddle temperature of this braking device, can be determined and output as a warning signal.

Additionally or alternatively, the first and / or second can be carried out in a step g)

Comparative value of a first braking device of a vehicle can be used as part of a plausibility test for leak testing with other braking devices of the vehicle. The comparison values of the braking devices are compared with one another. In the event of increased deviations from the comparison values, there is no plausibility.

A braking device, in particular one, is also according to the invention

Disc brake which has a measuring and / or evaluation unit which is equipped to carry out the aforementioned method according to the invention.

In addition, a vehicle is also according to the invention, which has several, but at least two, of the aforementioned braking devices according to the invention and with which steps f) and g) can also be carried out.

Further advantages, features and details of the invention result from the following description, in which an embodiment of the invention is explained in more detail with reference to the drawing. The person skilled in the art will see the in the drawing

Description and the features disclosed in combination

expediently also consider individually and combine them into meaningful further combinations. Show it:

Fig. 1 flow chart for the sequence of the method

2 first diagram of a temporally progressive density function;

3 shows a second diagram of a temporally progressive density function;

4 first diagram of a dysfunctional sealing function; and

Fig. 5 shows a schematic representation of an embodiment of a

braking device according to the invention.

Fig. 1 shows a flow chart for explaining an inventive

Embodiment of a method.

The method is used to monitor the tightness of a braking device,

especially a disc brake.

Field 100 is the representation of a brake actuation of the brake device. By actuating the brake 100, the measuring and / or evaluation unit can be used

Brake device, the inventive method can be activated, wherein the measuring and / or evaluation unit can have a data memory on which a computer program product for executing the present method can be stored.

Alternative options for executing the method are of course also possible. The method is activated by the brake actuation and a sensor signal of a pressure sensor is first determined in a step 101 and read in by the measuring and / or evaluation unit 2. A suitable braking device with a pressure sensor is disclosed, for example, in patent application DE 10 2017 128 595 A1 and DE 10 2016 1 17 593 A1. For the construction of a braking device according to the invention and the arrangement of a pressure sensor within this braking device, express reference is made to this

Registrations referenced. These braking devices shown in the aforementioned patent applications are only examples of a braking device according to the invention.

In a purely supplementary manner, the structure of the braking device is briefly described below based on a disc brake known from DE 10 2016 117 593 A1:

5, reference number 201 overall designates an embodiment variant of a pneumatic braking device according to the invention. The

Braking device 201, here in the form of a disk brake, has a brake disk 202 which is spanned by a brake caliper 203. By doing

Brake caliper 203 a brake lever 207 mounted in a brake caliper interior 206, which is operatively connected to a bridge 212 and at one

Braking process presses the bridge 212 via one or more pressure pieces against a brake lining 205 on the application side.

The movement of the brake lever 207 is effected by a plunger 208 of an air-tight pneumatic brake cylinder 204 connected to the brake caliper 203. The plunger 208 is moved from a non-braking position shown in FIG. 5 into a braking position by pressurizing the brake cylinder 204. The movement of the plunger 208 takes place as a linear movement. The plunger 208 is separated from a cylinder interior 21 1 in a known construction by an airtight separating device 210 designed here as a bellows.

The reference symbols 216 and 217 have been used to represent some interfaces to be monitored, possibly with seals, such as the separating device 210, which can be checked for their tightness.

As in FIG. 5, the state of the brake device 201 is also monitored a pressure sensor 214 is arranged in an airtight pressure chamber of the disc brake, the volume of which changes in proportion to a stroke movement of the tappet 208.

This pressure sensor 214 is, as shown schematically in FIG. 5, connected to a first interface of an evaluation unit 215, in which the stroke of the tappet 208 of the brake cylinder 204 is determined from the detected pressure change.

While the pressure sensor 214 is arranged on the tappet 208 in the embodiment variant shown in FIG. 5, it is also conceivable to arrange the pressure sensor 214 at a different location within the tappet space 209 or also in the

Caliper interior 206 of the brake caliper 203.

The pressure space in which the pressure sensor 214 is arranged is in one

Embodiment variant of the disc brake formed by the tappet space 209 and by the caliper interior 206 of the brake caliper 203, the tappet space 209 being separated from a cylinder interior 21 1 by an airtight separating device 210.

The separating device 210 is preferably designed as a bellows, in particular as a bellows, as already described above with reference to that in FIG. 5

Design variant was described. It is also conceivable to design the separating device 210 as a piston.

It is also conceivable that the pressure chamber is formed exclusively by the plunger chamber 209. The plunger chamber 209 is separated from the cylinder interior 21 1 and the by an appropriately designed airtight separating device 210

Caliper interior 206 of the brake caliper 203 is formed separately. In this case, the tappet 208 is received in a receiving opening connecting the tappet space 209 to the saddle interior 206, the tappet 208 sealing the tappet space 209 from the saddle interior 206 in an airtight manner both in the braking position and in the non-braking position. Such a pressure sensor 214 can be attached to an easily accessible location of the braking device 201, in particular anywhere in the caliper interior 206 or tappet space 209, since the pressure in the airtight pressure space under consideration changes in the same way. If you choose a location away from the brake disc and the brake pads, this enables the use of a comparatively inexpensive sensor, since the pressure sensor is not exposed to excessively high ambient temperatures due to the distance from the brake disc and the brake pads.

The pressure sensor 214 can e.g. on existing circuit boards of sensors, such as a wear potentiometer.

As can be seen in FIG. 1, the method 1 according to the invention can be triggered with the following method steps after the brake actuation 100 of the braking device. After calling function 2, e.g. by initiating the program, a pressure sensor signal is recorded. In this first step 101

Pressure sensor signal recorded over a predetermined time interval t. The

The program step can be defined as “reception of the sensor signal p in a specified

Time window t "can be defined.

In a subsequent step 102, the sensor signal pjn 1 comprising a plurality of data points, which has a predefined data length, is stored in the aforementioned data memory. If a signal pJnO is already present in the data memory, this signal is transmitted with the chronological sequence of the data points of the

recorded sensor signal pjn 1 overwritten.

This is easy to calculate from a computational point of view since both signals have the same data length. In this way, no additional storage space has to be provided within the measuring and / or evaluation unit.

In a subsequent step 103, the available sensor signal of the course of the internal pressure can be checked for an existing leak in the system. For this, two characteristic data points of the signal are used and the difference is formed.

Dr_ίh1 = f (p_in [t1], pjn [t2])

The characteristic data points are selected such that a data point lies before the mechanical application of the brake device and a data point after the application, that is to say in the actuated system state of the brake device.

However, optionally more than two characteristic points can also be used to detect a difference in the signal curve. Thus, to increase the robustness, several data points can be used to form two characteristic data points, for example one or more preceding and following data points (multi-sampling), the

Data points are either before or after tightening. From the

Data points can then be averaged and used as a characteristic data point.

The difference between the two (or more) characteristic data points can then be compared in one step 104 with one limit value or with several limit values, with several characteristic data points.

Is the difference or the differences below or above the defined

Limit values (depending on how they are defined) trigger a warning that the evaluated signal of the specific braking device indicates a leak in this braking device.

Alternatively or additionally, an internal counter can also be incremented and only after a defined counter value has been exceeded, that is to say with several

successive evaluations of the internal pressure with negative

Comparative results on the specific braking devices, for example with counter value = 3, a warning or a warning with higher urgency information can be issued. A typical program command could therefore be:

If Dr_ίh1 <= limit value, output 4 as warning and / or counter +1

In a further step 105, a gradual leak can now be determined by determining a second comparison value.

For this purpose, several data points, preferably in chronological succession, can be used, which were determined in the locked operating state. These are required to determine a second comparison value Dr_ίh2.

Dr_ίh2 = f (p_in [t1], pjn [t1 + x], ... p_in [tn]), where t1 -tn = closed operating condition and

x = period between two data points

In a step 106, the second comparison value is also compared with a further limit value

If Dr_ίh2 <= limit value, output 5 as warning and / or counter +1

A stop 3 of method 1 can then take place until a new brake actuation 100.

2 shows a pressure signal 6 of a pressure sensor, that is to say a pressure sensor signal, of a fault-free braking device which varies between approximately 2 and a maximum of 25 mbar. In addition, a "brake pressure signal" 7 is shown, which is also referred to as a signal from the service brake system. 2 is to be used to explain the third and fourth method steps 103 and 104 in more detail. The data points for step 103 before the brake is applied are in the range 0-3 mbar. In the diagrams, the signals share the ordinate axis. For the brake pressure signal 7 the unit is bar, for the internal pressure 6 the unit is mbar. Here a data point can be selected as the first characteristic data point. The data points after tightening are more than 20 mbar. Here can one

Data point should be chosen as the second characteristic data point. The difference between the first and the second data point should ideally be more than 17 mbar. If the value of the difference between the data points falls below 17 mbar, a warning signal can be issued.

The method can also have the further steps 105 and 106.

In these process steps, the pressure sensor signal can be adjusted to a possible one

gradual leakage in the brake device can be checked. A

there is a gradual leak if there is a gradual degradation of the sealing effect and this is not sensed by step 103.

In order to detect this creeping leak, successive

Data points are used and evaluated in the applied operating state of the braking device, that is to say when the brake is actuated.

The information can be extracted from the data points in different ways.

In a variant, a moving average can be formed and this can be compared with the starting value of the data points examined.

The amount of moving averages can be calculated iteratively over a time interval of the determined sensor signal. The time interval can be shifted overlapping, ie the first data point is repeatedly deleted from the time interval under consideration, the first data point is added after the time interval and a new mean value is calculated. For the calculation of the mean, the data points occurring in the aforementioned time interval can be weighted as desired. The sensor signal can be smoothed by forming a moving average can be reached so that outliers are not significant for the data points.

If the difference between the moving average and the starting value exceeds a certain limit, a warning can be given to a gradual one

Leak will be issued.

Another possibility is to determine the gradient of the chronological sequence from data points, for example using the recursive least squares method (RLS algorithm) or using another regression method. The gradient of the chronological sequence of the data points can then be compared with a defined limit value. If the determined gradient is above or below the specified limit value, a gradual leak is recognized and a corresponding warning is issued.

Alternatively or additionally, an internal counter can be incrementally increased if the limit value is exceeded or undershot and a warning is only issued after a defined counter value has been exceeded (in the case of successive evaluations of the internal pressure on the specific brake), for example when the counter value = 3.

The addressed data points are preferably recorded at each identical braking time at each braking in order to make the method as robust and comparable as possible. Here, for example, the i-th data point can be selected as the first data point after the start of the method. The variable i stands for a freely selectable integer, with the condition that the i-th data point is in the system state "closed".

This value can be set empirically, for example in a time range after the brake is applied and with a safety margin at the time the brake is released. The time at which the brake is released depends on the type of braking. With an empirically determined minimum duration, a time interval can be limited in which the brake is applied to all types of

Braking (braking to a standstill, slight adjustment braking, etc.) in System state "closed" is located. The data points addressed are therefore within the minimum time interval described.

In FIGS. 3 and 4, method steps 105 and 106 are again based on a

Internal pressure signal 6 and a "brake pressure signal" 7 practically explained. In Fig. 3 you can see from the waveform that instead of a plateau

Brake device in the applied state has a progressive reduction in the amount of the signal in the area 200 shown. This shows one

progressive leakage.

3 would obviously not lead to the output of a warning signal in step 103. For this reason, a separate evaluation of the gradient in the clamped state, for example in the area 200 shown, must take place.

Fig. 4 shows a brake system with a dysfunctional sealing effect. It can be seen that when the brake is applied, the internal pressure signal overshoots (approx. At 2 on the abscissa) and immediately afterwards a decrease to the level before application. At approx. 8 on the abscissa, the brake is released again and the volume is increased by retracting the ram. There is an overshoot into the negative, but due to the dysfunctional sealing effect, it immediately returns to the initial level.

The method shown in FIG. 1 can be supplemented by additional method steps. The difference values determined in steps 103 and 104 can also be used

Differences of pressure signals from other braking devices (101) of wheels of a vehicle are compared.

If the differential values of one / more braking devices (101) are significantly higher or lower than the pressure values of the other wheel brakes, an unusual temperature development on the wheel brakes, for example the saddle temperature, are concluded with significantly higher pressure values and a corresponding warning is issued.

In addition to the function monitoring described above, in particular with regard to tightness monitoring, the use of the pressure sensor in the

Braking device, such as shown in Fig. 5, ensure the monitoring of the stroke movement of the plunger during the braking process due to the changing pressure, and the stroke movement of the plunger can be determined from this pressure change, since the pressure change is proportional to the linear movement of the plunger.

REFERENCES

method

2 Call the function

3 stop

4th edition

5th edition

6 pressure sensor signal

7 Brake pressure signal

201 disc brake

202 brake disc

203 caliper

204 brake cylinder

205 brake pad

206 saddle interior

207 brake lever

208 pestles

209 pestle chamber

210 separator

21 1 cylinder interior

212 bridge

213 adjuster

214 pressure sensor

215 evaluation unit

21 6 interface (seal)

217 interface

100 brake application

101 -106 method step 200 area

300 data point

400 data point

Claims

PATENT CLAIMS

1. Method (1) for function monitoring, in particular for

Leakage monitoring, a braking device (201) characterized by the following steps:

a) evaluating (step 101) a sensor signal (6) for detecting an internal pressure of a pressure space, in particular a saddle interior (206) or one

Ram chamber (209) of the braking device (201) during a period of time, a plurality of data points (300,

400) of the internal jerk is detected and the period of time comprises at least one braking with at least one closed and one released operating state; b) Determination of a first comparison value (step 103) from two data points, a first data point being selected in a period of the sensor signal in which the braking device is in the applied operating state and a second data point in a period of the

Sensor signal is selected in which the braking device is in the released operating state;

c) comparing the first comparison value (step 104) with a first limit value while determining a leak, and

d) output (5) of a warning signal or change of a count value, if the

Comparative value reaches, exceeds or falls below the limit.

2. The method according to claim 1,

characterized in that

the method has one or more further steps e) (step 105, step 106), a second comparison value being determined from a chronological sequence (200) of data points in the clamped operating mode (step 105) and with a second one

Limit value is compared (step 106).

3. The method according to claim 1,

characterized in that with each brake actuation (100), the data points in step b) and / or the sequence of data points in step e) are evaluated at an identical point in time after a brake actuation and over an identically long period.

4. The method according to any one of the preceding claims,

characterized in that

a warning signal is issued if the count value has reached a certain value in step d).

5. The method according to any one of the preceding claims,

characterized in that

the first and / or the second data point is an average of several in time

successive data points are each in an operating state.

6. The method according to any one of the preceding claims,

characterized in that

the second comparison value as a moving average of several temporal ones

successive data points are each formed in an operating state.

7. The method according to any one of the preceding claims,

characterized in that

the comparison value is determined by a recursive method from a chronological sequence of data points in the closed operating mode.

8. The method according to any one of the preceding claims,

characterized in that

determined in a step f) by comparing the first and / or the second

Comparison values of several braking devices of a vehicle which show a stronger temperature development of one of the braking devices, in particular the

Saddle temperature of the brake device, determined and output as a warning signal.

9. The method according to any one of the preceding claims,

characterized in that in a step g) a plausibility test for leak testing is carried out with other braking devices of a vehicle.

10. Braking device (201), in particular pneumatic disc brake, with a measuring and / or evaluation unit (215) which is equipped to carry out a method (1) according to one of the preceding claims.

11. Vehicle comprising a plurality of braking devices (201) according to claim 10.