DE102009053693B4 - Method for determining a point of application of a clutch as well as clutch and assistance system - Google Patents

Abstract

Method for determining a point of application of a coupling, in particular for use in a motor vehicle, comprising the steps: - providing a coupling (2) with - a drive-side, first coupling element (4), - a driven-side, second coupling element (5), - a clutch actuator (6) for applying the first clutch element (4) to the second clutch element (5), - a spring element (14) for generating a pretensioning force (F) acting on the clutch actuator (6) and - a control unit ( 3) to determine a point of application of the clutch (2), - actuation of the clutch actuator (6) by specifying a target pressure (ps) for a fluid located in a pressure chamber (11) of the clutch actuator (6), the target pressure (ps) being derived a changing setpoint pressure basic signal (pG) and a periodic setpoint pressure pull signal (pP) superimposed thereon, - setting an actual pressure (pI) in the pressure chamber (11) corresponding to the setpoint pressure (ps) in the middle As a controllable pressure valve (12), - measuring an actual pressure (pI) in the pressure chamber (11) by means of a pressure sensor (13), and - determining the contact point of the coupling elements (4, 5) by evaluating the target pressure (ps) and the associated pressure Actual pressure (pI) by means of the control unit (3), the application point of the coupling elements (4, 5) being determined in such a way that an amplitude ratio (VA) of an amplitude (As) of the setpoint pressure (ps) and an amplitude (AI) of the actual pressure (pI) is calculated as a function of the nominal pressure basic signal (pG), - the amplitude ratio (VA) is compared with a threshold value (S), and - the pressure value (pA) of the nominal pressure basic signal (pG) corresponds to the application point at which the amplitude ratio (VA) is equal to the threshold value (S).

Description

The invention relates to a method for determining a point of application of a clutch, in particular for use in a motor vehicle. The invention also relates to a clutch, in particular for a motor vehicle, and an assistance system.

To optimize shifting comfort in motor vehicles, it is necessary to determine the point where the clutch is applied. The application point characterizes the point in the torque transmission behavior of a clutch at which all clutch elements or clutch disks are in contact with one another and enable torque transmission of the clutch.

From the DE 10 2007 031 383 A1 a method for determining the touch point of an automatically actuated clutch is known.

In the DE 10 2008 009 094 A1 a control method for a vehicle clutch is disclosed.

The invention is based on the object of creating a method for determining a point of application of a coupling which is simple and accurate.

This object is achieved by a method with the features of claim 1. According to the invention, it was recognized that a clutch has a plurality of pressure ranges, each of which has a different dynamic transmission behavior for the setpoint pressure. The point of application of the coupling elements can be determined by comparing the setpoint pressure with the associated actual pressure. For this purpose, the clutch actuator is actuated by specifying a defined setpoint pressure. The setpoint pressure for the fluid actuating the clutch actuator is composed of a changing setpoint pressure basic signal and a periodic setpoint pressure pulse signal superimposed on this. Essentially the entire pressure range of the clutch is passed through with the nominal pressure basic signal, the dynamic transmission behavior in the respective pressure range or actuation state being determined with the superimposed nominal pressure pulse signal.

The method according to the invention enables the application point to be determined precisely. By comparing the amplitude ratio with the threshold value, the point is determined from which there is no longer any change in volume in the pressure chamber due to an increase in the actual pressure. This point corresponds to the point of application.

A method according to claim 2 ensures a reliable determination of the application point. In the first pressure range, the actual pressure is too low to overcome the pretensioning force of the spring element. The clutch actuator remains unactuated or unmoved and the volume in the pressure chamber of the clutch actuator remains constant. Due to the constant volume in the pressure chamber, there is no fluid flow in the pressure chamber or the supply lines. Accordingly, the pressure drop from the pressure valve to the pressure sensor is low and the measured actual pressure follows the setpoint pressure very quickly.

In the second pressure range, the actual pressure is greater than the pretensioning force of the spring element. The clutch actuator actuates the first clutch element against the biasing force of the spring element and moves it in the direction of the second clutch element. According to Hooke's law, the greater the actual pressure, the greater the volume in the pressure chamber. Due to the increase in the volume in the pressure chamber, a fluid flow occurs in this or in the supply lines. The flow resistance leads to a pressure loss between the pressure valve and the pressure sensor, which is reduced again. The measured actual pressure follows the target pressure with a delay.

In the third pressure range, the clutch actuator reaches the first clutch element and pushes it in the direction of the second clutch element. At the point of application of the coupling, the coupling elements are completely in contact with one another. This prevents further movement of the clutch actuator and the volume of the pressure chamber remains constant with a further increase in the actual pressure. Because the change in the volume of the pressure space decreases or stagnates, the actual pressure follows the setpoint pressure again very quickly, as is the case in the first pressure range. The application point can be found easily and reliably by evaluating the third pressure area, which can be distinguished from the other pressure areas.

A method according to claim 3 ensures that the entire pressure range of the clutch is traversed. The accuracy of the determination of the contact point can be adjusted by means of the step height.

A method according to claim 4 ensures that the dynamic transmission behavior is examined for a sufficiently long period of time in the entire pressure range of the clutch.

A method according to claim 5 enables the application point to be determined quickly and easily.

A target pressure pulse signal according to claim 6 is easy to implement.

A method according to claim 7 ensures a reliable determination of the application point.

A method according to claim 8 simplifies the determination of the application point. A band-pass filter is used to filter out a narrow frequency band around the frequency of the target pressure pulse signal from the target pressure and the measured actual pressure, which contains the relevant information for the transmission behavior to be determined.

A method according to claim 9 is robust and reliable. The low-pass filter suppresses high-frequency interference signals.

The invention is also based on the object of creating a coupling, the point of application of which can be determined simply and precisely.

This object is achieved by a coupling with the features of claim 10. With regard to the advantages of the coupling according to the invention, reference is made to the advantages of the method according to the invention already described.

An assistance system according to claim 11 enables the shifting comfort of the clutch to be optimized for the torque to be transmitted in each case. If the application point of the clutch is known, the filling of the pressure chamber with the fluid, that is to say the actual pressure in the pressure chamber, can be adapted to the torque to be transmitted.

• 1 eine schematische Darstellung eines Assistenzsystems zur Optimierung des Schaltverhaltens einer Kupplung,
• 2 einen zeitlichen Verlauf eines Solldruckes zur Betätigung der Kupplung in 1,
• 3 eine schematische Darstellung zur Bildung eines Amplitudenverhältnisses aus einer Amplitude des Solldrucks und einer Amplitude eines zugehörigen, gemessenen Istdrucks, und
• 4 ein Diagramm des Amplitudenverhältnisses in Abhängigkeit eines Solldruck-Grundsignals des Solldrucks in 2.

Further features, details and advantages of the invention emerge from the following description of an exemplary embodiment. Show it:

• 1 a schematic representation of an assistance system for optimizing the shifting behavior of a clutch,
• 2 a time profile of a setpoint pressure for actuating the clutch in 1 ,
• 3 a schematic representation of the formation of an amplitude ratio from an amplitude of the setpoint pressure and an amplitude of an associated, measured actual pressure, and
• 4th a diagram of the amplitude ratio as a function of a target pressure base signal of the target pressure in 2 .

An assistance system 1 to optimize the shifting behavior of a motor vehicle comprises a clutch 2 with an associated control unit 3 . The coupling 2 has several first coupling elements on the drive side 4th and a plurality of second coupling elements on the output side 5 in the form of clutch plates or plate packs. The coupling elements 4th and 5 are displaceable relative to each other, so that they are in an open state of the clutch 2 do not rest against each other and in a closed state of the clutch 2 abut against each other, whereby by means of the coupling 2 a torque can be transmitted.

To make contact with the first coupling elements 4th to the second coupling elements 5 is a clutch actuator 6th provided, which is designed hydraulically and can be actuated by means of a fluid in the form of oil. The clutch actuator 6th comprises a piston-cylinder unit 7th with a cylinder 8th and a piston guided in it 9 . The piston 9 is with a pressure plate 10 connected to the first coupling elements 4th works. The cylinder 8th forms a pressure space 11 from the one on one side of the axially displaceable piston 9 is limited.

By means of a controllable pressure valve 12th is an actual pressure p _I in the pressure room 11 adjustable, which corresponds to a corresponding setpoint pressure ps. The setpoint pressure ps is from the control unit 3 specifiable. In the pressure room 11 is a pressure sensor 13th arranged to measure the actual pressure p _I serves. The pressure sensor 13th is for the transmission of the actual pressure p _I to the control unit 3 connected to this.

On one of the pistons 9 remote side of the pressure plate 10 is a spring element 14th arranged, the one on the pressure plate 10 acting preload force F is generated.

To determine a point of application of the coupling 2 is by means of the control unit 3 a setpoint pressure ps is specified, which results from a changing setpoint pressure basic signal p _G and a periodic setpoint pressure pulse signal superimposed on this p _P composed. The nominal pressure basic signal p _G is changed in such a way that essentially the entire pressure range of the clutch 2 with the associated actual pressure p _I is driven through. In particular, the nominal pressure basic signal p _G changed in such a way that in a first pressure range Δp ₁ by means of the associated actual pressure p _I the pretensioning force F is not overcome in a second pressure range Δp ₂ by means of the associated actual pressure p _I the preload force F is overcome, but the coupling elements 4th and 5 are not yet in contact with one another and in a third pressure range Δp ₃ by means of the associated actual pressure p _I the preload force F is overcome and the coupling elements 4th and 5 rest against each other.

How out 2 can be seen, the nominal pressure basic signal p _G preferably changed in steps, with an amplitude change ΔA _{G of} the nominal pressure basic signal p _G is constant between two levels. The change in amplitude ΔA _G thus results in different offsets for the setpoint pressure pulse signal p _P realized. The nominal pressure basic signal p _G is in 2 shown in dashed lines.

The periodic target pressure pulse signal p _P is for example a square wave signal. The change in amplitude ΔA _{P of} the target pressure pulse signal p _P is smaller than the change in amplitude ΔA _{G of} the nominal pressure basic signal p _G . Furthermore, the period T _{P of} the setpoint pressure pulse signal p _P less than a time cycle T _{G of} the nominal pressure basic signal p _G . The target pressure pulse signal p _P over time t is in 2 illustrated.

The frequency of the set pressure pulse signal p _P , which results as the reciprocal of the period T _P , is greater than the limit frequency of the hydraulic transmission behavior of the clutch 2 .

3 shows the in the control unit 3 implemented signal processing of the target pressure ps and the actual pressure p _I , where in 3 the transmission behavior of the clutch 2 is characterized by a double-frame rectangle. The setpoint pressure ps and the measured actual pressure p _I are initially using a bandpass filter 15th filtered, so that a narrow frequency band around the basic frequency of the target pressure pulse signal p _P is filtered out. The time course of the setpoint pressure ps and the associated actual pressure p _I are in digital form in a buffer memory 16 saved. The setpoint pressure ps and the associated actual pressure are then used from the stored time profiles p _I in an amplitude unit 17th the amplitude As of the setpoint pressure ps and the amplitude A _I of the actual pressure p _I at a certain value of the nominal pressure base signal p _G determined. From the amplitudes As and A _I is made by an inverse calculator 18th and a multiplier 19th an amplitude ratio V _A ' educated. The amplitude ratio V _A ' describes the ratio of the amplitude As to the amplitude A _I depending on the setpoint pressure basic signal p _G . The amplitude ratio V _A ' is then using a low-pass filter 20th filtered, with the filtered amplitude ratio V _A results. The filtered amplitude ratio V _A depending on the setpoint pressure basic signal p _G is in 4th shown.

wobei

min (VA)

das Minimum des Amplitudenverhältnisses V_A ,

max (VA)

das Maximum des Amplitudenverhältnisses V_A und

f

einen Schwellwertfaktor bezeichnet.

The point of application of the coupling elements 4th and 5 is made by comparing the filtered amplitude ratio V _A determined with a threshold value S. The threshold value S is determined empirically in preliminary tests. The threshold value S is for example $$\text{S.}\mathrm{=}\text{min}\left({\text{V}}_{\text{A.}}\right)+\text{f}\cdot \left[\text{Max}\left({\text{V}}_{\text{A.}}\right)-\text{min}\left({\text{V}}_{\text{A.}}\right)\right],$$

whereby

min (VA)

the minimum of the amplitude ratio V _A ,

max (VA)

the maximum of the amplitude ratio V _A and

f

denotes a threshold factor.

The threshold value factor f is, for example, 0.3.

The pressure value p _A of the nominal pressure basic signal p _G , at which the amplitude ratio V _A is equal to the threshold value S, corresponds to the point of application of the coupling elements 4th and 5 . This pressure value p _A characterizes the transition from the second pressure range Δp ₂ to the third pressure range Δp ₃ The amplitude ratio V _A increases sharply at the beginning of the second pressure range Δp ₂ , since the actual pressure p _I the target pressure ps only follows with a delay. The amplitude ratio increases accordingly V _A at the end of the second pressure range Δp ₂ or at the beginning of the third pressure range Δp ₃ , since the actual pressure p _I again follows the setpoint pressure ps essentially without delay. How out 4th can be seen has the amplitude ratio V _A two points of intersection with the threshold value S, the higher of the two pressure values of the nominal pressure basic signal p _G characterizes the point of application.

The method according to the invention thus becomes the point of application of the coupling elements 4th and 5 determined by the response of the measured actual pressure p _I on the clutch actuator 6th is examined for a periodic setpoint pressure signal with different offsets. The printing room 11 is via the current-controlled pressure valve 12th or pressure control valve is acted upon by a specific setpoint pressure ps, the actual pressure being set p _I some distance from the pressure valve 12th by means of the pressure sensor 13th is measured. The dynamic transfer behavior of p _I / p _S is in the entire pressure range of the clutch 2 evaluated. The point of application of the coupling elements 4th and 5 can be derived from the ratio of the amplitudes As and A _I by comparison with a threshold value S. The application point corresponds to the pressure value p _A of the nominal pressure basic signal p _G on which no change in volume of the pressure chamber due to an increase in pressure 11 more takes place. Is the attachment point of the coupling 2 known, the filling of the pressure chamber 11 optimize with the fluid to the desired torque to be transmitted, whereby the shift comfort can be improved.

Claims (10)

Method for determining a point of application of a coupling, in particular for use in a motor vehicle, comprising the steps: - providing a coupling (2) with - a drive-side, first coupling element (4), - a driven-side, second coupling element (5), - a clutch actuator (6) for applying the first clutch element (4) to the second clutch element (5), a spring element (14) for generating a pretensioning force (F) acting on the clutch actuator (6) and - a control unit (3) for determining a point of application of the clutch (2), - actuation of the clutch actuator (6) by specifying a setpoint pressure (ps ) for a fluid located in a pressure chamber (11) of the clutch actuator (6), the setpoint pressure (ps) being composed of a changing setpoint pressure basic signal (p _G ) and a periodic setpoint pressure pull signal (p _P ) superimposed thereon, - Setting an actual pressure (p _I ) corresponding to the set pressure (ps) in the pressure chamber (11) by means of a controllable pressure valve (12), - measuring an actual pressure (p _I ) in the pressure chamber (11) by means of a pressure sensor (13), and - Determination of the point of application of the coupling elements (4, 5) by evaluating the setpoint pressure (ps) and the associated actual pressure (p _I ) by means of the control unit (3), the point of application of the coupling elements (4, 5) being determined such that - a amplitude n ratio (V _A ) of an amplitude (As) of the target pressure (ps) and an amplitude (A _I ) of the actual pressure (p _I ) is calculated as a function of the target pressure base signal (p _G ), - the amplitude ratio (V _A ) with a The threshold value (S) is compared, and the pressure value (p _A ) of the nominal pressure basic signal (p _G ) corresponds to the application point at which the amplitude ratio (V _A ) is equal to the threshold value (S). Procedure according to Claim 1 , characterized in that the nominal pressure basic signal (p _G ) is changed in such a way that - in a first pressure range (Δp ₁ ) the preload force (F) is not overcome by means of the associated actual pressure (p _{I), - in a second pressure range (} Δp ₂ ) the preload force (F) is overcome by means of the associated actual pressure (p _I ) and the coupling elements (4, 5) are not in contact with one another, and - in a third pressure range (Δp ₃ ) the preload force is achieved by means of the associated actual pressure (p _I) (F) is overcome and the coupling elements (4, 5) rest against one another. Procedure according to Claim 1 or 2 , characterized in that the nominal pressure basic signal (p _G ) is changed in steps. Method according to one of the Claims 1 until 3 , characterized in that the period (T _P ) of the target pressure pulse signal (p _P ) is less than a time cycle (T _G ) of the target pressure basic signal (p _G ). Method according to one of the Claims 1 until 4th , characterized in that a change in amplitude (ΔA _P ) of the target pressure pull signal (p _P ) is smaller than a change in amplitude (ΔA _G ) of the target pressure base signal (p _G ). Method according to one of the Claims 1 until 5 , characterized in that the target pressure pulse signal (p _P ) is a Reckeck signal. Method according to one of the Claims 1 until 6th , characterized in that the frequency of the set pressure pulse signal (p _P ) is greater than the limit frequency of the transmission behavior of the clutch (2). Procedure according to Claim 7 , characterized in that the setpoint pressure (ps) and the actual pressure (p _I ) are bandpass filtered before the calculation of the amplitude ratio (V _A). Method according to one of the preceding claims, characterized in that the amplitude ratio (V _A ) is low-pass filtered before the comparison with the threshold value (S). Coupling, in particular for a motor vehicle, with - a drive-side, first coupling element (4), - a driven-side, second coupling element (5), - a coupling actuator (6) for applying the first coupling element (4) to the second coupling element (5), which - can be actuated by means of a fluid located in a pressure chamber (11), - has a controllable pressure valve (12) for specifying a target pressure (ps) and - a pressure sensor (13) for measuring an actual pressure (p _I ) in the Pressure chamber (11), - a spring element (14) for generating a pretensioning force (F) acting on the clutch actuator (6), and - a control unit (3) for determining a point of application of the clutch (2), the control unit (3) is set up to - specify a changing setpoint pressure basic signal (p _G ), - to transmit a periodic setpoint pressure pull signal (p _P ) to the setpoint pressure basic signal (p _G ), and to - by evaluating the setpoint pressure (ps ) and the associated meas enen actual pressure (p _I ) to determine the point of application of the coupling elements (4, 5), the point of application of the coupling elements (4, 5) being determined in such a way that - an amplitude ratio (V _A ) of an amplitude (As) of the setpoint pressure (ps) and an amplitude (A _I ) of the actual pressure (p _I ) is calculated as a function of the nominal pressure basic signal (p _G ), - the amplitude ratio (V _A ) is compared with a threshold value (S), and - the pressure value (p _A ) of the nominal pressure basic signal (p _G ) corresponds to the application point at which the amplitude ratio (V _A ) is equal to the threshold value (S). 11. Assistance system with a clutch (2) after Claim 10 to optimize the switching behavior of a motor vehicle.

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