WO2019101312A1

WO2019101312A1 - Method for detecting a kiss-point in a clutch system

Info

Publication number: WO2019101312A1
Application number: PCT/EP2017/080185
Authority: WO
Inventors: Mihai Dan NICOLAESCU
Original assignee: Volvo Construction Equipment Ab
Priority date: 2017-11-23
Filing date: 2017-11-23
Publication date: 2019-05-31

Abstract

A method for detecting a kiss-point in a clutch system comprising the steps of determining (S1) a first value based on the integral of the ingoing rotational speed (ωin) of the clutch over a predetermined time duration (T1), determining (S2) a second value based on the integral of the outgoing rotational speed (ωout) of the dog clutch over said predetermined time duration, calculating (S3) the difference (A) between the first value and the second value, calculating (S4) the derivative (ΔA) of said calculated difference (A) with respect to time (t) for said time duration (T1), and concluding (S5) that the kiss-point (KP) is detected when the derivative (ΔA) is below a threshold value (V).

Description

METHOD FOR DETECTING A KISS-POINT IN A CLUTCH SYSTEM

TECHNICAL FIELD

The invention relates to a method to detect the kiss-point of a clutch assembly during engagement.

The invention can be applied in any clutch system in a vehicle and is especially relevant for heavy-duty vehicles, such as articulated haulers, trucks, buses and construction equipment.

BACKGROUND

In clutch systems it is an advantage to know the kiss-point, i.e. the initial point when the clutch is in an engaged position for transferring torque from the driving axle to the driven axle. Knowing the timing of the kiss-point may be used to e.g. evaluate the performance of the gear shifting.

Most clutch system merely comprise a digital position sensor that only indicate when engaged position is completed. Hereby, the input is only given when the clutch is already in an engaged position, which is after the kiss-point. For example, US8042420 detects the engagement state of a clutch by use of the rotational speed difference between an inner main shaft and an outer main shaft and a signal outputted from a gear position sensor. However, a disadvantage of measuring mismatch speed is that the speed sensors used to calculate the mismatch speed are affected by measurement noise, which will cause false kiss-point detection in the clutch system.

In state of the art systems, the kiss-point may be determined by using an analogue position sensor. However, a disadvantage of using an analogue position sensor is that the sensor itself is costly, but also the implementation of the sensor is complex. An analogue sensor must have access to measure the fork or clutch component during the transition to engage position.

Thus, there is a need for a method to determine the kiss-point with high accuracy but with an improved cost level. SUMMARY

An object of the invention is to provide a method for detecting the kiss-point in a clutch assembly, having improved accuracy and cost level compared to known solutions.

The inventive concept is based on the inventor’s realization that the problem with indicating the kiss-point of the clutch by using only a digital position sensor may solved by calculating, not only the speed of the driving and driven axle, but also the difference in the integral of the rotational speeds and thereafter calculating the time derivate of said difference. When said derivate value falls below a threshold value, the kiss-point can be concluded.

According to a first aspect of the invention, the object is achieved by a method according to claim 1 , namely a method for detecting a kiss-point in a clutch system, wherein the method comprises the steps of: determining a first value based on the integral of the ingoing rotational speed of the clutch over a predetermined time duration, determining a second value based on the integral of the outgoing rotational speed of the clutch over said predetermined time duration, calculating the difference between the first value and the second value, calculating the derivative of said calculated difference with respect to time for said time duration, concluding that the kiss-point is detected when the derivative is below a threshold value. Hereby, a method for detecting the kiss-point in a clutch assembly is provided that provides an improved accuracy and cost level compared to known solutions. By first integrating the ingoing rotational speed and then deducting the value from integrating the outgoing rotational speed and finally calculating a derivate of the difference in respect of time, any potential noise from sensing the rotational speed may be filtered, and a more true and good approximation of the clutch kiss-point may be achieved. Thus, this method provides a good approximation of the clutch kiss-point without requiring advance position sensors.

In the context of this application the ingoing speed is meant as the rotational speed of the driving axle (i.e. the axle being adapted to be mechanically coupled to the engine), and the outgoing speed is the rotational speed of the driven axle (which is adapted to be coupled to the propulsion means, such as the wheels). According to one embodiment the method comprises a step of measuring the ingoing rotational speed (coin) by means of a first sensor on a driving axle. Hereby, the ingoing rotational speed may be obtained by means of measuring on the driving axle.

According to one embodiment the method comprises a step of measuring the outgoing rotational speed by means of a second sensor on a driven axle. Hereby, the outgoing rotational speed may be obtained by means of measuring on the driven axle.

According to one embodiment the first and second sensor are speed sensors. In one embodiment, the sensors are digital hall effect sensors.

According to one embodiment the steps of determining of the first and second values, calculating the difference between the first and second values and calculating the derivate are repeated for further time durations, if the derivative is above said threshold value. Hereby, the method may be repeated until the kiss-point is detected. Thereby, it may be continuously repeated throughout relevant operations.

According to one embodiment the method is performed on a dog-clutch system. Hereby, the method is applied to a clutch system which could reduce the wear and tear if the kiss- point would be determined with increased accuracy. In the context of this application a dog clutch is meant to be a clutch that couples two rotating shafts or other rotating components not by friction but by interference. The two parts of the clutch are designed such that one will push the other, causing both to rotate at the same speed and will never slip.

According to one embodiment the method comprises a step of measuring the engagement time from a clutch engage actuation until the detected kiss-point. Hereby, the system may track the duration of the actuation until the kiss-point is detected, which can be used for e.g. controlling the timing of the clutch engage actuation command.

According to one embodiment the method comprises a step of storing the measured the engagement time. Hereby, the data may be stored and compared over the life time of the clutch system, so as to be used for e.g. service intervals and/or to change components in the clutch system. According to one embodiment the threshold value corresponds to a value when the second derivate of the difference between the first value and the second value with respect to time turns positive Hereby, the method determines when the difference in rotational speeds have passed each other, but filtered by the two integrated values and the derivate of the difference, as described above.

According to one aspect, the method according to any of the embodiments above is used in a vehicle for logging clutch data including the engagement time. Hereby, the data may be logged and compared over the life time of the clutch system, so as to be used for e.g. service intervals and/or to change components in the clutch system.

According to one embodiment the method according to any of the embodiments above is used in a heavy vehicle. Hereby, the method may be use on a vehicle with components that involve heavy loads and thereby high potential wear and tear if the kiss-point is not accurately determined.

According to one embodiment the method according to any of the embodiments above is used for adjusting control of clutch actuators dependent on the time elapsed between a clutch engage actuation and a concluded kiss-point. Hereby, the actuation may be controlled in order to time the kiss-point in a desired way.

According to one aspect, a computer program is provided which comprise program code means for performing the steps of any of the above mentioned embodiments. The program may be executed on a computer. Hereby, the method may be used to simulate and based on simulation construct and configure vehicle clutch systems so that they have a correct kiss-point.

According to one embodiment the computer program comprising program code means for performing the steps of any of the above mentioned embodiments and the program is executed in an embedded system in a vehicle.

According to one aspect, a vehicle logging unit for logging vehicle date, is provided which logging unit comprise program code means for performing the steps of the method according to any of the above mentioned embodiments. Hereby, the method may be used to monitor the clutch function in a vehicle, and the outcome may be e.g. logged and compared over the life time of the clutch system, so as to be used for e.g. service intervals and/or to change components in the clutch system or for warning the driver/fleet owner etc. if needed.

Further advantages and advantageous features of the invention are disclosed in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

In the drawings:

Fig. 1 is a flowchart of the steps that may be carried out in the method,

Fig. 2a is a graph denoting the rotational speed of the ingoing and outgoing rotational speeds in a clutch system,

Fig. 2b is a graph denoting the area between ingoing and outgoing rotational speeds, and Fig. 2c is a graph denoting derivate of the area A.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled addressee. Like reference characters refer to like elements throughout.

The present disclosure contemplates a method and program products on any machine- readable media for accomplishing various operations. The embodiments of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine- readable media can be any available media that can be accessed by a general purpose or special purpose computer or another machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium, specifically including a non-transitory computer-readable storage medium, which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine- executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

Turning to the figures, the method will be described in relation to the steps as illustrated in fig 1. However, since figures 2a, 2b and 2c also relate to the actual calculations carried out in the different steps, these figures will partly be referred to in parallel.

As mentioned, Fig. 1 is a flowchart diagram illustrating the method steps that may be carried out in the claimed method. The first step S1 a is and optional step (illustrated by the dashed lines) of measuring S1 a the ingoing rotational speed w,_h by means of a first sensor on a driving axle. This way, it will be rather easy to perform the step of determining S1 a first value based on the integral of the ingoing rotational speed w,_h Alternatively, the ingoing rotational speed oo_in may be calculated from another input along the driveline. Moving on, the third step is similarly an optional step of measuring S2a the outgoing rotational speed w_0ίL by means of a first sensor on a driven axle. The advantages are analogous with the first optional step, and so are the alternatives to this step.

Further, the next illustrated step is determining S2 the second value based on the integral of the outgoing rotational speed w_0ίL of the clutch over said predetermined time duration. This would represent the white area under the oo_0urline in fig 2a. After this step, the third step is carried out, namely calculating S3 the difference A between the first determined value and the second determined value. The area A is illustrated as the striped area A in fig. 2a and as a graph in fig 2b. Further, the forth step in fig. 1 is calculating S4 the derivative DA of said calculated difference A with respect to time t for said time duration T 1. The derivate DA is illustrated as a graph in fig 2c.

The next step of the method is to conclude S5 that the kiss-point KP is detected when the derivative DA is below a threshold value V. This is also illustrated in fig 2c, as when the line DA falls below the dashed line V.

Further, there are two more optional steps. One step of measuring S6 the engagement time from a clutch engage actuation 1 1 until the detected kiss-point KP. And a last step of storing S7 the measured the engagement time. As has been described above, the steps of measuring S6 and storing S7 the data may be used for e.g. evaluation and maintenance of the clutch system.

Now turning specifically to the graphs in figures 2a-2c. Fig. 2a is a graph, showing time in milliseconds (MS) vs revolutions per minute (RPM), denoting the rotational speed of the ingoing w,_h and outgoing w_ouC rotational speeds in a clutch system. All three figures 2a-2c comprise three vertical dashed lines. The first line (from the left) represents when the actuation 1 1 of the clutch is initiated, and is thus denoted with reference 1 1. Further, the second dashed line (middle) represents where the area calculation is reaching the convergence point 12, and is thus where the estimated dog-clutch kiss-point is determined, and is thus denoted 12. Finally, the third dashed line (the right one) is a point where a dog clutch position sensor would indicate engaged position 13, if present in the system.

The ingoing speed is the speed of the driving axle (i.e. from the power source such as the engine), and the outgoing speed is the speed of the driven axle (couple to the propulsion means, such as the wheels). The area A in fig 2a represents the difference between the integral of the ingoing speed and the outgoing speed. As the kiss-point approach this area is decreased, as the speeds converge. The kiss-point KP is where the two lines of the ingoing oo_in and outgoing w_0ίL rotational speeds cross. After the kiss-point KP the rotational speeds substantially merges into the same rotational speed for both the ingoing w,_h and outgoing w_ouC rotational speed. Moving on to fig. 2b, it shows a graph denoting the area A between ingoing w,_h and outgoing oo_out rotational speed. In the beginning, close to the time where actuation 1 1 of the clutch is initiated, the increase of the area is quick, and as difference of the rotational speeds is rather large in the beginning. However, as the time moves on and the kiss-point 5 approaches, the increase in area is deaccelerating, thus the DA is decreased, as illustrated in fig. 2c. The vertical span denoted between the two horizontal lines in Fig. 2b represents the area convergence limit CL. That is, in this area the between ingoing w,_h and outgoing oo_out rotational speed are substantially synchronized. o Fig. 2c is a graph denoting derivate of the area A, that is DA. As is shown in the graph, the derivate DA decreases as the kiss-point KP approach. At one point, the derivate DA falls below the predetermined threshold value V, which is denoted with the dashed horizontal line marked V. The point where the derivate DA falls below the value V is close to the Kiss- point KP.

5

Thus, the above mentioned method provides a way to identify the clutch kiss-point KP by analyzing the area A between the ingoing w,_h and outgoing oo₀ut clutch element rotational speeds. As the two speeds are becoming synchronized the area will converge to a value that will present only small variations over time. The advantage of using the integral part is0 the robustness against the measurement error and therefore smaller error in identifying the kiss-point KP.

If the method is described from a mathematical point of view the kiss-pint is concluded by calculate S3 the area A between the ingoing w,_h and outgoing w_oui clutch rotational speeds:

Thereafter the derivative of the area is calculated S4 with respect to time:

0 Finally, the kiss-point KP is concluded S5 when the derivative value falls below a selected threshold value.

It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

Claims

1. A method for detecting a kiss-point in a clutch system, characterized in that the method comprises the steps of:

- determining (S1 ) a first value based on the integral of the ingoing rotational speed (u)_in) of the clutch over a predetermined time duration (T1 ),

- determining (S2) a second value based on the integral of the outgoing

rotational speed (w_oiL) of the clutch over said predetermined time duration,

- calculating (S3) the difference (A) between the first value and the second

value,

- calculating (S4) the derivative (DA) of said calculated difference (A) with

respect to time (t) for said time duration (T 1 ), and

- concluding (S5) that the kiss-point (KP) is detected when the derivative (DA) is below a threshold value (V).

2. A method according to claim 1 , further comprising a step of

- measuring (S1 a) the ingoing rotational speed (u)_in) by means of a first sensor on a driving axle.

3. A method according to any one of claim 1 or 2, further comprising a step of

- Measuring (S2a) the outgoing rotational speed (w_oiL) by means of a second sensor on a driven axle.

4. A method according to any one of claims 2 or 3, wherein said first and second sensor are speed sensors.

5. A method according to any one of claims 1 -4, wherein said steps of determining of the first and second values, calculating the difference between the first and second values and calculating the derivate are repeated for further time durations, if the derivative (DA) is above said threshold value (V).

6. A method according to any one of claims 1 -5, wherein said method is performed on a dog-clutch system.

7. A method according to any one of claims 1 -4, wherein said method further comprises a step (S6) of measuring the engagement time from a clutch engage actuation (1 1 ) until the detected kiss-point (KP).

8. A method according to claims 7, wherein said method further comprises the step of storing (S7) the measured the engagement time.

9. A method according to any one of claims 1 -8, wherein said threshold value (V) corresponds to a value when the second derivate of the difference (A) between the first value and the second value with respect to time (t) turns positive.

10. Use of the method according to any of claims 1 -8, in a vehicle for logging clutch data including the engagement time.

1 1 . Use of the method according to any of claims 1 -8, in a heavy vehicle.

12. Use of the method according to any of claims 1 -8 for adjusting control of clutch actuators dependent on the time elapsed between a clutch engage actuation (1 1 ) and a concluded kiss-point.

13. A computer program comprising program code means for performing the steps of any of claims 1 -9, when said program is run on a computer.

14. A computer program comprising program code means for performing the steps of any of claims 1 -9, when said program is run in an embedded system in a vehicle.

15. A vehicle logging unit, for logging vehicle date, comprising program code means for performing the steps of the method as described in any of claims 1 -9.