Method for controlling the position of a moving element in a vehicle transmission device

Abstract

The present invention relates to a method for controlling the position of a moving element in a vehicle transmission device (1). The method comprises the following steps: (i) angularly moving a control plate (10), (ii) measuring the angular position of a torque output element of an actuator and comparing the measured value with a limiting threshold value (m), (iii) reducing the rotational speed of the actuator's electric motor, (iv) applying a limited current (Ilim) to the actuator's electric motor, (v) stopping the control of the electric motor when, cumulatively, the limited current value (Ilim) is substantially reached, the measured value of the angular position of the actuator's torque output element corresponds substantially to the desired position, and the angular speed of the torque output element is substantially zero. Figure for the abstract: Figure 8

Description

Title of the invention: Method for controlling the position of a moving element in a vehicle transmission device

[0001] The invention relates to a method for controlling the position of a moving element in a vehicle transmission device.

[0002] The method according to the invention is of particular interest in the field of parking locking devices for a vehicle transmission.

[0003] Conventionally, a parking lock device for a vehicle transmission comprises a parking gear that is mechanically linked in rotation to at least one wheel of the vehicle. A rotation-locking finger for the parking gear is movably mounted between a first position, called "non-park," in which the finger is disengaged from the parking gear, and a second position, called "park," in which the finger is engaged between two teeth of the parking gear, thus blocking the rotation of the parking gear and consequently the vehicle.

[0004] An electromechanical actuator allows the position of the locking finger to be changed according to an instruction issued by a controller. This actuator generally comprises an electric motor, a torque output element linked directly or indirectly to the locking finger, and an angular position sensor for the torque output element that reflects the engaged or disengaged position of the locking finger.

[0005] To obtain a mechanically stable position of the locking device in an engaged or disengaged position, it is known to interpose a control plate between the torque output element of the actuator and the locking finger. This control plate generally comprises a cam profile with at least two concave portions and at least one convex portion disposed between the two concave portions. A rolling element, fixed relative to the transmission, is adapted to be constrained to the bottom of one of the concave portions in a static position, ensuring a mechanically balanced position. The two concave portions are respectively associated with the first and second positions of the locking finger.

[0006] It is important to ensure successful engagement of the locking finger between the teeth of the parking wheel in order to immobilize the vehicle. It is also important to transmit this engagement or disengagement information to a control unit.

[0007] By using only the angular position sensor of the finger-linked torque output element, it is difficult to achieve the accuracy required to guarantee the successful engagement, in particular due to the mounting tolerances of the actuator on the transmission.

[0008] By also using the measurement of the electric motor current, it is possible to obtain an indicator of the torque applied by the actuator to the control plate. Based on this torque and knowledge of the shape of the control plate, it is possible to determine whether the desired position of the control plate has been reached.

[0009] US patent 2005 / 043878 A1 proposes a method for determining the exact position of the control plate, thus reflecting the position of a moving element of the transmission. The proposed method uses an angular position sensor attached to the control plate and a torque sensor applied by the electric motor to rotate the control plate. The values ​​associated with these two sensors are combined in a control unit, thereby determining the exact position of the moving element of the transmission.

[0010] The method described in the aforementioned document has the drawback of not taking into account the inertia of the rolling element as it travels along the cam track of the control plate, particularly during the downward phases. Thus, the rolling element may extend beyond the bottom of the concave portion, generating an unacceptable margin of error which, in the worst-case scenario, can lead to incorrect information regarding the exact position of the moving element.

[0011] It is therefore necessary to optimize this margin of error so that it is as low as possible and without additional cost, i.e. without adding sensors or additional components.

[0012] Thus, the invention proposes a method for controlling the position of a moving element in a vehicle transmission device, the device comprising a moving element between a first position and a second position, an actuator for driving the moving element between the first and second positions comprising an electric motor, a torque output element, a current consumption sensor for the electric motor, an angular position sensor for the torque output element, a control plate disposed between the torque output element of the actuator and the moving element, said plate comprising a cam profile with at least two concave portions, at least one convex portion disposed between the two concave portions and a rolling element capable of being constrained to the bottom of one of the concave portions in a static position, the bottom of the two concave portions being respectively associated with the first and second positions of the moving element,The process is characterized in that it comprises the following steps: i. to angularly move the control plate (10) by driving the electric motor of the actuator, thus allowing the rolling element (16) to move out of the first concave portion (11) towards the second concave portion (13), ii. Measure the angular position of the actuator's torque output element and compare the measured value with a limiting threshold value (m), and in the case where the measured value is greater than the limiting threshold value (m), iii. reduce the rotational speed of the actuator's electric motor, iv. apply a limited current (Ilim) to the actuator's electric motor, v. stop the control of the electric motor when cumulatively the value of the limited current (Ilim) is substantially reached, the measured value of the angular position of the actuator's torque output element corresponds substantially to the second position and the angular speed of the torque output element is substantially zero.

[0013] One of the advantages of the invention is that instead of relying solely on the measured angle of the torque output element of the actuator to determine whether the final position is actually reached, the current consumed and the speed of the electric motor of the actuator intervene to ensure that the mechanism will stop in the correct position, i.e. a mechanically balanced position.

[0014] This method makes it possible to achieve a precision target of plus or minus 1.5° without increasing the manufacturing cost of the device.

[0015] Another advantage of the present invention is that it is not necessary to perform position learning of the control plate on the vehicle assembly lines. Position control is performed in real time to automatically stop the control plate by limiting the inertia and available torque around the desired position.

[0016] The method according to the invention also has the advantage of adapting to a displacement of the angular position sensor of the torque output element of the actuator due to temperature or dismantling or even replacement of the actuator, for example.

[0017] The rolling element in the sense of the invention means that it is capable of moving or sliding along the cam surface, regardless of its structure, the rolling element can also be an elastic blade with a bead acting as a rolling element.

[0018] According to the invention, the device also includes a parking gear which is mechanically linked in rotation to at least one wheel of the vehicle.

[0019] According to the invention, the moving element is a rotation-locking finger for the parking gear that is movably mounted between a first position called "non-park" in which the finger is disengaged from the parking gear and a second position called "park" in which the finger is engaged between two teeth of the parking gear. In other words, these two positions correspond to the locking and unlocking positions of the parking gear. The two concave portions of the control plate are respectively associated with the first and second positions of the locking finger.

[0020] According to the invention, when the rolling element moves from the first position to the second position, the control plate moves through an angular range a. This range is, for example, between 28.5° and 31.5°, and preferably 30°. For example, 0° corresponds to the first position and 30° corresponds to the second position.

[0021] According to an additional feature of the invention, the limiting threshold value m is a value within the angular range a and is reached from 80% of the angular displacement of the control plate. In other words, the limitation applies in the last 20% of the angular displacement of the control plate 10.

[0022] According to another feature of the invention, the rolling element reaches the second position with a deviation e relative to the bottom of the concave surface. This deviation e corresponds to the torque generated by the actuator's electric motor with the limited current. For example, the deviation e is between 0.3° and 0.5°. Thus, the rolling element exerts force on the upward slope of the second concave portion but is prevented from going further due to the limited current.

[0023] In other words, thanks to the invention, it is ensured that the rolling element cannot go much further than the bottom of the concave portion in which it is required to move. This point is detected using threshold values ​​of the current consumed by the electric motor, the angular velocity, and the angular position of the torque output element of the actuator.

[0024] According to the invention, the rotational speed of the actuator's electric motor is reduced in steps. More precisely, the rotational speed of the actuator's electric motor is reduced twice. For example, the rotational speed of the electric motor is reduced firstly to a range between 80% and 90% of the angular displacement of the control plate. The rotational speed of the electric motor is then reduced a second time, more significantly, for example, to a range between 90% and 100% of the angular displacement of the control plate.

[0025] This stepped limitation makes it possible to limit inertia and prevent overshooting of desired positions. The reduced speed as the second position is approached allows for closer approximations of static conditions, meaning that the current then depends primarily on the reaction of the shape of the concave portion.

[0026] According to the invention, the rotational speed of the electric motor is reduced by a factor of between 2 and 2.5.

[0027] According to the invention, the limited current is less than the current required for the rolling element to exit one of the concave portions. This has the effect of preventing the rolling element from going beyond the desired position.

[0028] The present invention is described in connection with a parking lock device for a vehicle transmission but is in no way limited to it. For example, the invention can also be applied to a device comprising a gear-shifting system based on the angular position of the torque output element of the actuator. In this case, each gear is associated with the bottom of a concave portion of the cam profile of the control plate.

[0029] Other features and advantages of the invention will become apparent from the following detailed embodiment, with reference to the attached figures:

[0030] [Fig.1] represents a parking locking device for a vehicle transmission according to the invention;

[0031] [Fig.2] illustrates the operation of the rolling element mechanism at the level of the control plate;

[0032] from [Fig.3] to [Fig.7] the different stages of the rolling element along the cam path of the control plate are schematically represented;

[0033] [Fig.8] represents a graph of the evolution of the rolling element along the cam path of the control plate between its two positions as a function of the current consumed by the electric motor of the actuator.

[0034] It should be noted that the figures disclose the invention in sufficient detail for its implementation, and that the figures help to further define the invention if necessary. However, the invention should not be limited to the embodiment disclosed in the description.

[0035] The parking locking device 1 of [Fig. 1] is located partly inside the transmission. It comprises a parking gear 2 which is mechanically linked in rotation to at least one wheel of the vehicle.

[0036] A parking ratchet is pivotally mounted around a shaft 8. The parking ratchet has, at one of its ends, a locking finger 4 designed to engage in a recess between two teeth of the parking gear 2.

[0037] The parking gear locking finger 4 is movably mounted between a first position, referred to as "non-park," in which the finger is disengaged from the parking gear 2, and a second position, referred to as "park," as shown in [Fig. 1], in which the finger is engaged between two teeth of the parking gear. Thus, the rotation of the parking gear is blocked and the vehicle is immobilized.

[0038] The locking finger 4 is held in, and returned to an unlocking position by means of an elastic return member 7, for example in the form of a torsion spring, arranged around the shaft 8 of the parking pawl.

[0039] A fork head 6 mounted to slide to alternately adopt a locking position in which the fork head 6 pushes the locking finger 4 into an engaged position, i.e. into the recess of the parking gear 2, in order to block the transmission output, and thus park the vehicle.

[0040] The fork head 6 is able to adopt another position, known as the unlocking position, in which it does not interfere with the locking finger 4, allowing said parking pawl to be returned by the elastic return member 7 to its unlocking position of the locking finger 4.

[0041] The fork head 6 is mounted at the end of a guide rod 9. A compression spring 14 is mounted around the rod 9 in order to push said fork head 6 into the locking position.

[0042] The fork head 6 includes a first roller and a second roller 5, each mounted to rotate freely around an axis, the first roller being positioned to roll against the parking ratchet when the fork head 6 moves to the locking position.

[0043] An electromechanical actuator (not visible) allows the position of the locking finger 4 to be changed according to an instruction issued by a controller. This actuator comprises an electric motor, a torque output element linked directly or indirectly to the locking finger, and an angular position sensor for the torque output element that reflects the engaged or disengaged position of the locking finger.

[0044] In order to obtain a mechanically stable position of the locking device in an engaged or disengaged position, a control plate 10 is interposed between the torque output element of the actuator and the locking finger 4. The torque output element of the actuator engages in an interface 15 of the control plate 10, for example by means of a male / female coupling.

[0045] This control plate 10 comprises a cam profile with at least two concave portions 11, 13 and at least one convex portion 12 disposed between the two concave portions 11, 13. A rolling element 16, also referred to as a ball bearing system in this case, is adapted to be constrained to the bottom of one of the concave portions 11, 13 in a static position, ensuring a mechanically balanced position. The two concave portions 11, 13 are respectively associated with the first and second positions of the locking finger.

[0046] The control plate 10 is capable of being pivoted under the effect of the torque supplied by the actuator. When the rolling element 16 moves from the first position to the second position the control plate 10 moves according to an angular range a, for example of 30°.

[0047] The ball bearing system which is fixedly mounted on the transmission includes an elastic element 17 in the form of a spring at the end of which is a ball 18. This ball 18 is in contact with the cam profile of the control plate 10.

[0048] The interaction between the rolling element 16 and the control plate 10 is illustrated in [Fig.2],

[0049] The mechanical means for retaining the control plate 10 in its functional positions “park” and “non-park” is represented schematically only with the ball 18. The functional area of ​​the control plate 10 is defined by the cam track which includes the two concave portions 11, 13 and the convex portion 12.

[0050] Under the effect of a torque supplied by the actuator, the control plate pivots in front of the ball 18, which moves in a substantially radial direction relative to the control plate 10. As the control plate rotates, its functional area moves. The ball 18 advances into the concave portions 11, 13 of the control plate 10 as it passes over it.

[0051] The ball appears three times, respectively in positions A, B, C, in the two concave portions and on the convex portion. For example, A is considered to be the first position, called "non-park", C is considered to be the second position, called "park", and B an intermediate position of the ball on the convex portion of the cam track.

[0052] The ball 18 can move from the first concave portion 11 to the second concave portion 13 and vice versa depending on the direction of rotation of the actuator's electric motor. The invention applies to both directions of rotation.

[0053] The first concave portion 11 comprises two slopes 111 and 112, the second concave portion 13 comprises two slopes 131 and 132. The convex portion is defined in part by the slopes 112 and 131.

[0054] When the ball 18 moves from the first concave portion 11 to the second concave portion 13, the slopes 111 and 131 are said to be downward and the slopes 112 and 132 are said to be upward. Conversely, when the ball 18 moves from the second concave portion 13 to the first concave portion 11, the slopes 111 and 131 are said to be upward and the slopes 112 and 132 are said to be downward. When the ball 18 travels along an upward slope, the actuator's electric motor generates a positive torque, and when the ball 18 travels along a downward slope, the actuator's electric motor generates a negative torque.

[0055] By knowing the geometry of the cam path of the control plate 10, it is thus possible to know the torque curve applied by the electric motor of the actuator as a function of the angular position of the control plate 10.

[0056] The advantage of this control plate 10 is that if the torque of the electric motor of the actuator disappears, the control plate 10 is thus mechanically held in the “park” or “non-park” position.

[0057] The different stages of the process according to the invention will now be described.

[0058] Figure 3 shows the control plate 10 in its initial, so-called "non-park" position, i.e., the actuator's electric motor is not powered. The actuator's torque output element coupled to the control plate 10 is also in its "non-park" position. The angular sensor of the actuator's torque output element thus measures the "non-park" position with two margins of error: one related to the assembly tolerances of the actuator on the transmission, and the other related to the sensor itself.

[0059] Fig. 4 represents the control plate 10 when it begins to move, i.e. the ball 18 passes from the first concave portion 11 to the second concave portion 13. In this Fig. 4 the ball is on the upward slope 112 of the first concave portion 11 towards the crest of the convex portion 12. In this position and as seen previously, the torque generated by the electric motor is positive and the current consumed by the electric motor is also positive.

[0060] Fig. 5 represents the control plate 10 in a position where the ball 18 has passed the crest of the convex portion 12 and is on the downward slope 131 of the second concave portion 13. In this position, the ball 18 is "swallowed", that is to say the torque generated by the electric motor becomes negative and the current consumed by the electric motor is also negative.

[0061] In order that the device is not driven by the downward slope 131, the angular position of the torque output element of the actuator is measured and this measurement is compared with a limiting threshold value m.

[0062] In the case where the measured value of the angular position is greater than the limiting threshold value m, the rotation speed of the electric motor of the actuator is reduced when the ball 18 approaches the bottom of the second concave portion 13 and a limited current IUm is applied to the electric motor of the actuator.

[0063] It is necessary to slow the descent of the ball 18 because the current consumed by the electric motor does not correspond to the position of the ball 18 on the cam track of the control plate 10 due to dynamic effects. In other words, it is necessary to reduce the rotational speed of the electric motor so that the dynamic effects are negligible and the current consumed corresponds to the path of the ball 18 on the cam track of the control plate 10.

[0064] The limiting threshold value m is an angular calibration value that is stored in the actuator controller. The limiting threshold value m is reached when the last 20% of the angular displacement of the control plate 10 is reached.

[0065] For example, when the ball 18 moves from the first position to the second position, the control plate 10 moves through an angular range a of 30°. In other words, the rotational speed of the electric motor is reduced and the current limited IUm over approximately the last 20% of the angular displacement of the control plate 10, i.e., between 24° and 30°, or in other words, over 6°.

[0066] The rotational speed of the electric motor is reduced by a factor of between 2 and 2.5. For example, the rotational speed of the electric motor decreases from 12,800 rpm to 5,600 rpm. The rotational speed of the actuator's electric motor is reduced in steps, for example, twice. In this case, the rotational speed of the actuator's electric motor is reduced firstly within a range of between 80% and 90% of the angular displacement of the control plate 10, i.e., between 24° and 27°, or 3°. The rotational speed of the actuator's electric motor is reduced a second time, more significantly, within a range of between 90% and 100% of the angular displacement of the control plate 10, i.e., between 27° and 30°, or 3°.

[0067] The limited current value Iiim is a calibration value that is stored in the actuator controller. For example, the limited current value is 1.3A.

[0068] Figure 6 shows the control plate 10 in a position where the ball 18 reaches the bottom of the second concave portion 13. The torque generated and the current consumed by the electric motor reverse and become substantially close to zero. The torque output element of the actuator coupled to the control plate 10 is in its so-called "park" position. The angular sensor of the actuator's torque output element thus measures the "park" position with two margins of error: one related to the assembly tolerances of the actuator on the transmission, and the other related to the sensor itself.

[0069] Fig. 7 represents the control plate 10 in a position where it is desired to stop, i.e. in a position where the ball 18 slightly exceeds the bottom of the second concave portion 13, which represents a zone of deviation e with respect to the position of the bottom of the second concave portion 13.

[0070] The fact that a limited current is applied to the electric motor of the actuator prevents the ball 18 from going back up the slope 132 and makes it possible to ensure that it has crossed the bottom of the second concave portion 13 and is in the deviation zone e.

[0071] The electric motor control is stopped when cumulatively the limited current value IUm is substantially reached, the measured value of the angular position of the torque output element of the actuator corresponds substantially to the second "park" position of the ball 18 and the angular velocity of the torque output element The actuator's tolerance is essentially zero. "Similarly" means that there is a tolerance threshold for each of these criteria. These tolerance thresholds are calibration values ​​that are stored in the actuator controller.

[0072] In the present case, the limited current IUm is considered to be reached when it is between 1.2A and 1.4A, which means that the rolling element 16 or the ball 18 is "forcing" itself on the upward slope of the second concave portion and that we are in the acceptable deviation zone.

[0073] In the present case, the second position of the rolling element 16 is considered to be reached when the angular position sensor of the torque output element output of the actuator is + / - 2.5° relative to the position recorded in the controller.

[0074] The zero angular velocity of the actuator's torque output element is considered to be achieved with a tolerance threshold of + / - 0.5 rad / s, thus allowing for low inertia. The angular velocity of the actuator's output element is derived from its angular position.

[0075] The control plate 10 is thus stopped when the ball 18 slightly exceeds the bottom of the second concave portion 13, which represents a deviation e relative to the bottom of the second concave portion 13. This deviation e represents the final angular position of the control plate 10, which corresponds to the torque generated by the actuator with the limited current Iiim. For example, this deviation e is between 0.3° and 0.5°.

[0076] The angular sensor of the actuator's torque output element thus measures the "park" position with two margins of error: the first related to the assembly tolerances of the actuator on the transmission, and the second related to the sensor itself. The desired deviation e compensates for these two margins of error to ensure correct positioning of the rolling element in the desired position.

[0077] Fig. 8 represents on the same graph the curve 100 of the current consumption of the electric motor of the actuator according to the advancement of the ball 18 on the cam path of the control plate 10 and the curve 200 shows the position of the control plate between its “park” and “non-park” positions.

[0078] The graph is divided into four phases which correspond to the different visible stages from [Fig.4] to [Fig.7].

[0079] Curve 100 shows that at the beginning of the movement of the control plate 10 there is a positive peak in current consumption corresponding to the effort required for the ball 18 to overcome the upward slope 112 of the first concave portion 11. Then the current consumption decreases until it becomes negative, meaning that the ball is on the downward slope 131 of the second concave portion 13. Then the current consumption becomes positive again, which means that the ball 18 has crossed the bottom of The second concave portion 13 begins to travel up the ascending slope 132. Due to the limited current IUm applied to the electric motor, the ball 18 can no longer rise and stops at the desired position with the deflection e, thus guaranteeing the desired position.

[0080] Although the invention has been described in connection with a particular embodiment, it is clear that it is by no means limited to it and that it includes all technical equivalents of the means described.

[0081] In the claims, the reference symbols in parentheses should not be interpreted as a limitation of the claim.

Claims

1. Demands Method for controlling the position of a moving element in a device of a vehicle transmission (1), the device comprising: - a movable element (5) between a first position and a second position, - a drive actuator for the moving element (5) between the first and second positions comprising an electric motor, a torque output element, a current consumption sensor for the electric motor, and an angular position sensor for the torque output element, - a control plate (10) disposed between the torque output element of the actuator and the moving element (5), said plate (10) comprising a cam profile with at least two concave portions (11, 13), at least one convex portion (12) disposed between the two concave portions (11, 13) and a rolling element (16) capable of being constrained to the bottom of one of the concave portions (11, 13) in static position, the bottoms of the two concave portions (11, 13) being respectively associated with the first and second position of the moving element, The process is characterized in that it comprises the following steps: i. to angularly move the control plate (10) by driving the electric motor of the actuator, thus allowing the rolling element (16) to exit the first concave portion (11) towards the second concave portion (13), ii. Measure the angular position of the actuator's torque output element and compare the measured value with a limiting threshold value (m), and in the case where the measured value is greater than the limiting threshold value (m), iii. reduce the rotational speed of the actuator's electric motor, iv. apply a limited current (IUm) to the actuator's electric motor, v. stop the control of the electric motor when cumulatively the limited current value (IUm) is substantially reached, the measured value of the angular position of the torque output element of the actuator corresponds substantially to the second position and the angular velocity of the torque output element is substantially zero.

2. The method according to claim 1, characterized in that when the rolling element (16) moves from the first position to the second position the control plate (10) moves along an angular range a, for example between 28.5 and 31.5°, and preferably 30°.

3. Method according to claim 2, characterized in that the limiting threshold value (m) is a value within the angular range a and reached from 80% of the angular displacement of the control plate (10).

4. A method according to any one of the preceding claims, characterized in that the rolling element (16) reaches the second position with a deviation (e) from the bottom of the concave surface, this deviation (e) corresponds to the torque generated by the electric motor of the actuator with the limited current (Iiim).

5. Method according to claim 4, characterized in that the deviation (e) is between 0.3° and 0.5°.

6. A method according to any one of the preceding claims, characterized in that the rotational speed of the electric motor of the actuator is reduced in steps.

7. Method according to claim 6, characterized in that the rotational speed of the electric motor of the actuator is reduced a first time in a range between 80% and 90% of the angular displacement of the control plate (10) and a second time, more strongly, in a range between 90% and 100% of the angular displacement of the control plate (10).

8. A method according to any one of the preceding claims, characterized in that the rotational speed of the electric motor is reduced on the basis of a factor between 2 and 2.

5.

9. A method according to any one of the preceding claims, characterized in that the limited current (Iiim) is less than the current required to the rolling element (16) to exit one of the concave portions (11, 13).

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