Method for controlling a hydraulic unit and drive unit having a planetary transmission operated by the hydraulic unit

Abstract

The invention relates to a method for controlling a hydraulic unit (100) having a pump (101) operated by an electric motor (M) and an output cylinder (104) having a friction clutch which is loaded by a friction clutch which is hydraulically actuated against the action of a spring element (107), the electric motor being controlled by a control unit, and to a drive unit having at least one hydraulic unit (100). The invention proposes that the continuously adjusted contact point (TP) of the friction clutch is associated with a currently determined filling time of the output cylinder (104), and the currently determined filling time is determined in dependence on a change in a rotational characteristic value of a rotor of the electric motor (M) driving the pump (101).

Description

Technical Field

[0001] The present invention relates to a method for controlling a hydraulic unit and an apparatus having a drive unit having a planetary transmission operated by the hydraulic unit. Background Technology

[0002] A method for determining the rapid filling time of the output cylinder of a clutch for powertrain adaptation is known from publication DE 10 2009 055 065 A1. The clutch contact point is determined based on the pressure value.

[0003] Such a drive unit, for example, a drive unit having an electric motor that drives the drive wheels of a motor vehicle when a switchable transmission, such as a planetary transmission, is engaged in the middle, is known, for example, from publications DD 278 307 A and EP 2 597336 B1. For example, to switch planetary transmissions, components of the planetary transmission, such as the ring gear and / or planet carrier, are fixed to the housing by means of a brake band, allowing different gear ratios to be switched from different torque paths with and without rotating ring gears or planet carriers. The brake band can be operated in various ways by means of an electric actuator or a hydraulic actuator, for example, by means of a hydrostatically operated friction clutch. Control of such a planetary transmission is performed by means of a control unit that controls the corresponding actuator. Summary of the Invention

[0004] The object of this invention is an improvement to a method for controlling a hydraulic unit used to operate a friction clutch, and an improvement to a drive unit, particularly a wheel drive device for a motor vehicle. In particular, the object of this invention is to enable simple and adaptive control of the friction clutch without the need for additional sensor devices.

[0005] The proposed method is used to control a hydraulic unit for operating a friction clutch, such as a drive unit for a wheel drive system on two or all drive wheels of a motor vehicle. To this end, a central and / or multiple distributed control units are proposed, which control the drive unit and each of an output device, such as a transmission for the wheel drive system.

[0006] The drive unit is preferably driven by an electric motor. The electric motor can be configured as either a drive type or an energy recovery type. A planetary gearbox with at least two gears is connected downstream of the electric motor or its rotor. The planetary gearbox is configured at least as a single stage, preferably as a two-stage gearbox. As a component of the planetary gearbox, it includes at least one sun gear, a ring gear, and at least one planet carrier with rotatable planetary gears distributed circumferentially. The planetary gears mesh with the sun gear and their respective ring gears. Depending on the connection of the components, a component of the planetary gearbox, such as the sun gear of the first stage, serves as the drive unit and is fixedly connected to the rotor. For example, two planet carriers of different stages can be connected to the output device, such that, without reversing the rotational directions, not only the ring gear but also the planet carriers can preferably be connected to the housing in a crosswise and opposite manner to establish two different transmission ratios between the drive unit and the output device. Each pair of components can be fixedly connected to the housing of the planetary gearbox, i.e., in a manner fixed to the housing, for switching the planetary gearbox.

[0007] For this purpose, a hydrostatically operated friction clutch is employed, which is positioned between the housing and the corresponding component in a manner that allows for efficient switching. For example, the ring gear can be connected to the housing by means of a first friction clutch, and the planet carrier of a single-stage or multi-stage planetary transmission can be connected by means of a second friction clutch. The friction clutch is configured, for example, as a forced-closing friction clutch, i.e., the friction clutch closes under hydrostatic pressure, thereby connecting to the housing. In the unoperated state of the friction clutch, the ring gear or planet carrier is rotatably positioned relative to the housing. To achieve a large gear ratio, the friction clutches are alternately engaged and disengaged. When switching planetary transmissions, the friction clutches are operated in a cross-operation manner, i.e., one friction clutch is disengaged while the other is engaged.

[0008] The hydrostatic operation of the friction clutch is achieved by means of a hydraulic unit controlled by a control unit. The hydraulic unit includes a pressure supply device, such as an electrically operated pump. Both hydraulic units for the two friction clutches can be fed by a common pressure supply device. The hydraulic unit includes an output cylinder that operates the friction clutch, which is connected to the pressure supply device via a pressure line. Under pressure, the output cylinder piston moves axially against the action of a spring element, such as a return spring, thereby establishing a frictional engagement in the friction clutch with friction plates and mating friction plates arranged between the housing and the relevant components of the planetary gearbox. If pressure is released from the output cylinder, the output cylinder piston, preloaded by the spring element, moves to its rest position, and the frictional engagement of the friction clutch is released. To control the pressure in the output cylinder, a pressure relief valve, controlled by the control unit and for example electromagnetically operated, is connected in the pressure line between the pressure supply device and the output cylinder. In a first switching position, the pressure relief valve connects the output cylinder to the pressure supply device. In a second switching position, the output cylinder connects to the unpressurized oil pan. The pressure relief valve preferably actively switches from the second switching position to the first switching position against the return spring.

[0009] In order to assemble a planetary transmission using precisely coordinated friction clutches, it is necessary to accurately understand the contact points of the friction clutches. It is shown here that, due to system lag, the contact point where the friction clutch begins to transmit torque and the disengagement point where the friction clutch begins to cease transmitting torque are separated from each other, so that the disengagement point is determined and adjusted individually, for example, by means of an empirically determined gap, relative to the continuously adjusted contact point.

[0010] The contact points of the friction clutches in the drive unit, or the contact points of two friction clutches, are continuously adjusted by associating these contact points with the currently determined filling time of the output cylinder, such that the contact point of the corresponding friction clutch is identified according to its corresponding filling time. The filling time is here associated with a preset path of the output cylinder piston, thus geometrically relating it to the contact point. The corresponding conversion is stored in the control unit that controls the electric motor and can be determined empirically and, for example, stored as characteristic curves, tables, or formulas.

[0011] The filling timing of the contact point and the output cylinder associated with the contact point is determined here based on the change in the rotational characteristic value of the rotor of the pump driven by the electric motor. Here, the following effect is used: when torque is initially transmitted via the friction clutch, the friction clutch engages further by means of the further filled output cylinder, so that, in addition to the preload of the return spring, the displacement of the output cylinder piston preloads the friction clutch's friction plate assembly, thereby causing the rotational characteristic value to change, for example, decrease due to the varying load. In this way, additional sensor devices, such as pressure sensors with corresponding detection and evaluation software in the pressure lines, can be eliminated, making it possible to manufacture the hydraulic unit more cost-effectively.

[0012] It is advantageous here to evaluate the change in acceleration of the rotor of the electric motor used to drive the pump as a rotational characteristic value. Here, the rotor acceleration changes whenever the pump is subjected to an increased load at the contact point where the friction plates of the friction plate assembly and the mating friction plates are engaged.

[0013] Rotational characteristics of the rotor can be detected and processed without additional sensor devices for detecting rotational characteristics by means of: electronic commutation of the electric motor, and evaluation of the commutation speed information to determine the rotational characteristics to be continuously detected and evaluated for adjusting the contact points.

[0014] An electric motor can be speed-controlled during the operating time outside of a defined contact point, wherein the electric motor operates in a voltage-controlled manner, for example, in an open loop, at least during the defined contact point.

[0015] To determine the currently detected rotational characteristic value independently of interfering variables that do not change due to the contact point, compensation is made for environmental influences affecting the rotational characteristic value. For example, the rotational characteristic value is temperature compensated. This means, for example, that changes in viscosity, pipe cross-section, etc., due to temperature variations are compensated for. For this purpose, a temperature sensor can be installed either directly thermally connected to the pressure line or located away from the pressure line, for example, on the circuit board of the control unit, where the temperature of the hydraulic fluid is calculated using a temperature model.

[0016] For example, rotational characteristic values ​​used as acceleration variations can be evaluated based on the rotational speed of an electric motor in order to compensate for, for example, the inertia of rotors, pumps, etc.

[0017] For example, rotational characteristics can be evaluated based on the switching of at least one valve in the hydraulic unit, such as a pressure relief valve, to compensate for pressure drops at valves that are not fully open, for example.

[0018] For example, the currently determined rotational characteristic value is time-dependently associated with each interruption of the control unit during the contact point determination process in a FIFO data register with a defined amount of storage space. The rotational characteristic values ​​are serially read in and shifted forward one after another, with the sum of the rotational characteristic values ​​in the register determined in each time period. This sum is compared to a preset sum value for the contact point, and in the case of the preset sum value, the rotational characteristic value important to the contact point or the corresponding filling time or output cylinder piston position is determined.

[0019] The rotational characteristic values ​​located in the storage space can each be loaded with coefficients specifically preset for that storage space. For example, the rotational characteristic value located in the storage space centrally positioned in the register can be numerically applied with a minimum coefficient, such as zero, and the rotational characteristic values ​​of the storage spaces spaced apart from the storage space in two time directions can be applied with numerically increasing coefficients. By determining the sum value in sequence, the inflection point at the contact point of the rotational characteristic value can be determined, at which the compression of the friction plates of the friction clutch and the mating friction plates begins. It is thus concluded that at the contact point, after a gradual increase in the bridging of the output cylinder piston's idle stroke during the filling of the output cylinder, upon reaching the contact point at the inflection point, as torque begins to be transmitted to the friction clutch and, for example, by means of a corresponding switch, the relevant components of the planetary gearbox are fixed to their housing, the rotational characteristic value increases sharply.

[0020] The described processing of the detected rotational features is used to filter the rotational features using an FIR filter. Attached Figure Description

[0021] This invention is based on Figures 1 to 4 The embodiments shown are described in detail. The accompanying drawings illustrate: Figure 1 The diagram schematically illustrates a hydraulic unit for operating a friction clutch. Figure 2 Show Figure 1 A graph showing the pump pressure or electric motor acceleration over time. Figure 3 Shown in determining Figure 1 A diagram showing the rotational characteristic values ​​of the electric motor during the contact point of the friction clutch using an FIR filter. as well as Figure 4 Show Figure 1 Simulation of determining the contact point of a friction clutch. Detailed Implementation

[0022] Figure 1A hydraulic unit 100 is schematically shown for one of the two friction clutches in a drive unit having two friction clutches that switch the gear ratio of a planetary transmission during cross-operation. One hydraulic unit 100 is provided for each of the two friction clutches. The hydraulic unit 100 includes a pump 101 driven by the rotor of an electronically commutated electric motor M, which generates a pump pressure P. p .

[0023] The pressure relief valve 102 is installed in the pressure line 103 between the pump 101 and the output cylinder 104, and selectively switches between the pump 101 and the unpressurized oil pan 105 on the one hand, and on the other hand, the output cylinder 104 can utilize the orifice plate G. orif The pressure drops to the clutch pressure P. c Pump pressure P p Applying flow Q in Or depressurize.

[0024] Output cylinder piston 106 under clutch pressure P c The friction clutch, which is not shown in detail, is preloaded at the contact point TP after the filling time Δt required for filling the output cylinder 104 ends, and the friction plate assembly 108, which has greater rigidity than the spring element 107, is shifted by the action of the lower resistance spring element 107.

[0025] If the pressure relief valve 102, which is open here, closes, the output cylinder 104 is first filled during the filling time Δt, and the output cylinder piston 106 displaces against the action of the spring element 107 until the contact point TP, and the clutch pressure P in the pressure line 103... c The pressure increases slowly but continuously. If the output cylinder piston 106 or the component connected to the output cylinder piston reaches the friction plate assembly 108 at the contact point TP, the clutch pressure P in the pressure line 103 increases. c The friction clutch increases at a greater slope because the friction plate assembly 108 is additionally pre-tightened. The friction clutch begins to transmit torque at the contact point TP by means of the initial frictional contact between the friction plates of the friction plate assembly 108 and the mating friction plates, resulting in a clutch pressure P with a smaller slope. c With a clutch pressure P that has a larger slope c After the transition, the filling time of the output cylinder 104 is basically over, and signals, such as the flag for the contact point TP, can be stored in the software used to control the friction clutch.

[0026] To determine the clutch pressure P without an additional pressure sensor cThe response of the electric motor M driving pump 101 to the load is evaluated at the contact point TP, the transition between a smaller and a larger slope. For this purpose, during the operation of the friction clutch, at the fill time Δt, the change in rotational characteristics, such as the acceleration of the rotor of electric motor M, is evaluated using a sensor device for commutation of the electric motor, wherein electric motor M operates in open loop, for example, under a preset fixed voltage, at least during the fill time Δt. Due to the larger load on pump 101 after reaching the contact point TP, the clutch pressure P... c The transition between smaller and larger slopes can be identified based on the change in rotor acceleration over the filling time Δt and determined at the transition point. To smooth out noise, the rotational characteristic values ​​of the detected acceleration changes can be subjected to FIR filtering.

[0027] The friction clutch is preferably constructed according to the principle of forced closure (normally open). This means that the friction clutch is disengaged when there is no pressure in the pressure line 103, and disengaged when the applied clutch pressure P is applied. c The bottom is closed. This also means that the components of the planetary transmission associated with the friction clutch are connected to the housing under pressure.

[0028] Figure 2 refer to Figure 1 The hydraulic unit 100 schematically illustrates the clutch pressure P according to Figure 200. c The relationship between acceleration A and time t. As long as the pressure relief valve 102 is closed, the pump pressure P... p Guided into pressure line 103 and in orifice plate G orif The pressure drops to the clutch pressure P. c Here, the output cylinder 104 is filled with a pressure medium at time t, and the output cylinder piston 106 is displaced against the action of the spring element 107 during the filling time Δt, until the friction plates of the friction plate assembly 108 and the mating friction plates are within the detected time interval Δt. c Inner contact. Due to the pressure difference ΔP relative to the filling time Δt. f Utilizing pressure difference ΔP c The increased rigidity of the pre-tightened friction plate assembly 108 causes a change in the load on the pump 101, resulting in an acceleration change ΔA on the rotor of the electric motor M. The discrete filling moments of the contact points of the friction clutch are associated with this acceleration change ΔA, at which the friction clutch begins to transmit torque.

[0029] Figure 3 Reference Figure 1The hydraulic unit 100 is schematically shown, in which an FIR filter 300 is applied to the detected acceleration value of the rotor of the electric motor M to determine the contact point TP. The contact point TP is determined along the direction of the increased stroke of the output cylinder piston 106 with respect to the filling time Δt and the friction plate assembly. Figure 2 The time interval Δt c A portion of the preload is determined by register 301, which has these five storage spaces 302, 303, 304, 305, and 306, being filled according to the FIFO (first-in-first-out) principle with acceleration values ​​c4, c3, c2, c1, and c0 detected in successive interruptions, and evaluated according to the principle of an FIR (finite impulse response) filter 300. Here, if the value obtained by the FIR filter 300 corresponds to the calibrated magnitude, the contact point TP or the fill time value associated with said contact point is identified.

[0030] In principle, it is shown for, for example, determining Figure 2 The FIR filter 300 at contact point TP. Coefficients k4, k3, k2, k1, and k0, with values ​​of -6, -3, 0, 3, and 6, are associated with acceleration values ​​c4, c3, c2, c1, and c0 temporarily stored in storage spaces 302, 303, 304, 305, and 306 of FIFO register 301. In each interruption case, the acceleration values ​​c4, c3, c2, c1, and c0 in storage spaces 302, 303, 304, 305, and 306 are summed according to a given formula. If the sum corresponds to a calibration value, the fill time value belonging to acceleration value c2 is adopted as the contact point TP.

[0031] Figure 4 Referring to the preceding diagram, the determination of the contact point TP at fill time t (TP) is illustrated as a simulation 400 of the hydraulic unit 100 used to operate the friction clutch. Sub-chart I shows the acceleration value A(x) determined by the filter 300 at each interruption with respect to time t in curve 401. The acceleration value A(x) is detected at fill time Δt and time interval Δt. c The operation proceeds and is subsequently interrupted because, after reaching the maximum torque that can be transmitted via the friction clutch, the rotational speed n of pump 101 can be reduced or shut off under the corresponding preload of the friction plate assembly, and there is no reproducible acceleration value A(x).

[0032] If the acceleration value A(x) is lower than the threshold value, such as the acceleration value A(TP), or the acceleration change ΔA exceeds the preset threshold value, then the contact point TP is associated with the filling time t(TP).

[0033] Subgraph II shows curves 402, 403, 404, and 405 with respect to time t. Curve 402 shows the rotor speed n of the electric motor M with respect to time t, and curve 403 shows the pump pressure P of pump 101. p Curve 404 shows the clutch pressure P c Curve 405 shows the acceleration A of the rotor of the electric motor M. The value of curve 405 serves as the basis for filtering by means of FIR filter 300, as shown in curve 401. The remaining curves 402, 403, and 404 are shown for reference only and are not explicitly required for determining the contact point TP.

[0034] List of reference numerals 100 hydraulic units 101 Pump 102 Pressure relief valve 103 Pressure piping 104 Output Cylinder 105 Oil Pan 106 Output cylinder piston 107 Spring Components 108 friction pad assembly 200 charts 300 FIR filter Register 301 302 Storage Space 303 Storage Space 304 storage space 305 Storage Space 306 storage spaces 400 simulation 401 curve 402 curve 403 curve 404 curve 405 curve A acceleration A(x) acceleration value A(TP) acceleration value c0 acceleration value c1 acceleration value c2 acceleration value c3 acceleration value c4 acceleration value G orif Orifice plate k0 coefficient k1 coefficient k2 coefficient k3 coefficient k4 coefficient M electric motor n rotational speed P c Clutch pressure P p Pump pressure Q in flow TP contact points t time t(TP) fill time ΔA acceleration change ΔP c Pressure difference ΔP f Pressure difference Δt fill time Δt c Time interval.

Claims

1. Method for controlling a hydraulic unit (100) having a pump (101) operated by an electric motor (M) and an output cylinder (104) with a hydrostatically actuated friction clutch which loads a friction clutch against the action of a spring element (107), the electric motor being controlled by a control unit, characterized in that The continuously adjusted contact point (TP) of the friction clutch is associated with the currently determined filling time (t(TP)) of the output cylinder (104), and the currently determined filling time (t(TP)) is determined based on the change in the rotational characteristic value of the rotor of the pump (101) driven by the electric motor (M).

2. The method according to claim 1, characterized in that, The rotational characteristic value is the change in acceleration (ΔA).

3. The method according to claim 2, characterized in that, The electric motor (M) is electronically commutated, and sensor information on the commutation is evaluated to determine the rotational characteristic value.

4. The method according to claim 1, characterized in that, The electric motor (M) operates in a voltage-controlled manner at least during the determination of the contact point (TP).

5. The method according to claim 4, characterized in that, Compensation is provided for the environmental effects acting on the rotational characteristic value.

6. The method according to claim 5, characterized in that, Temperature compensation is applied to the rotational characteristic value.

7. The method according to claim 6, characterized in that, The rotational characteristic value used as the acceleration change (ΔA) is evaluated based on the rotational speed (n) of the electric motor.

8. The method according to claim 7, characterized in that, The rotational characteristic value is evaluated based on the switching of at least one valve of the hydraulic unit (100).

9. The method according to any one of claims 1 to 8, characterized in that, The rotational eigenvalues ​​are filtered using an FIR filter (300).

10. A drive unit comprising an electric motor, a planetary gearbox with at least two gears connected downstream of the electric motor, and at least one output device connected downstream of the planetary gearbox, wherein the gears of the planetary gearbox are switched by means of two friction clutches fixed in a manner fixed to a housing and hydrostatically operated, wherein the friction clutches are respectively operated by means of a hydraulic unit (100) controlled by a control unit, the hydraulic unit comprising a pump (101) driven by an electric motor (M), an output cylinder (104) loading the friction clutches against the action of a spring element (107), and a pressure relief valve (102) disposed in a pressure line (103) between the pump (101) and the output cylinder (104), characterized in that, The contact point (TP) of the friction clutch is continuously adjusted by means of the method according to any one of claims 1 to 9.

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