A Shift Actuator Assembly for a Vehicle Transmission

Abstract

The present invention is directed to a shift actuator assembly for a vehicle transmission including a shift actuator (2) moveable between a number of predetermined shift positions, a sensor (24) for sensing the shift actuator position, a mechanical detent mechanism (30, 32, 34) such that at the predetermined shift positions a detent engagement feeling is generated, an adaptive braking mechanism (10, 12) acting on the actuator (2) to selectively increase the resistance against shift actuator movements, and a controller (20) receiving the input from the position sensor (24), wherein the controller (20) is arranged to control the adaptive brake mechanism (10, 12), characterized in that the controller is arranged to control the adaptive brake mechanism so that, if the shift actuator (2) reaches any of the predetermined shift positions, the braking force of the adaptive braking mechanism is increased such that the actuator movement is completely stopped for a predetermined period of time, whereafter the adaptive braking mechanism is released.

Claims

1. A shift actuator assembly for a vehicle transmission including: a shift actuator (2) moveable between a number of predetermined shift positions, a sensor (24) for sensing the shift actuator position, a mechanical detent mechanism (30, 32, 34) such that at the predetermined shift positions a detent engagement feeling is generated, an adaptive braking mechanism (10, 12) acting on the actuator (2) to selectively increase the resistance against shift actuator movements, and a controller (20) receiving the input from the position sensor (24), wherein the controller (20) is arranged to control the adaptive brake mechanism (10, 12), and wherein the controller is arranged to control the adaptive brake mechanism so that, if the shift actuator (2) reaches any of the predetermined shift positions, the braking force of the adaptive braking mechanism is increased such that the actuator movement is completely stopped for a predetermined period of time, whereafter the adaptive braking mechanism is released.

2. A shift actuator assembly for a vehicle transmission including: a shift actuator (2) moveable between a number of predetermined shift positions, a sensor (24) for sensing the shift actuator position, a mechanical detent mechanism (30, 32, 34) such that at the predetermined shift positions a detent engagement feeling is generated, an adaptive braking mechanism (10, 12) acting on the shift actuator to selectively increase the resistance against shift actuator movements, and a controller (20) receiving the input from the position sensor (24), wherein the controller (20) is arranged to control the adaptive brake mechanism (10, 12), and wherein in that the controller (20) is arranged to receive a velocity signal representative for the velocity of the shift actuator movement, to control the adaptive brake mechanism (10, 12) so that, if the actuator (2) reaches any of the predetermined shift positions and the velocity of the shift actuator is below a threshold velocity, the braking force of the adaptive braking mechanism (10, 12) is increased such that the actuator movement is completely stopped for a predetermined period of time, whereafter the adaptive braking mechanism is released, whereas the controller (20) is arranged to omit activation of the adaptive braking mechanism and arrestment of movement of the shift actuator upon passing one of the predetermined shift positions when the velocity determined is above the threshold velocity.

3. The shift actuator assembly according to claim 1, wherein the adaptive brake mechanism (10, 12) utilizes a magneto-rheological fluid acting between a component (6) moving with the shift actuator (2) and a stationary component (8), and wherein the controller (20) is arranged to control a magnetic field generator (12) to generate a magnetic field in the area of the magneto-rheological fluid upon activation.

4. The shift actuator assembly according to claim 1, wherein the controller (20) is arranged to control the adaptive brake mechanism such that the predetermined period of time of arrestment of movement of the actuator is within the range 0.05 to 0.9 seconds.

5. The shift actuator assembly according to claim 1, wherein the shift actuator is a shift lever.

6. The shift actuator assembly according to claim 1, wherein the shift actuator (2) is a rotary knob.

7. The shift actuator assembly according to claim 2, wherein the adaptive brake mechanism (10, 12) utilizes a magneto-rheological fluid acting between a component (6) moving with the shift actuator (2) and a stationary component (8), and wherein the controller (20) is arranged to control a magnetic field generator (12) to generate a magnetic field in the area of the magneto-rheological fluid upon activation.

8. The shift actuator assembly according to claim 2, wherein the controller (20) is arranged to control the adaptive brake mechanism such that the predetermined period of time of arrestment of movement of the actuator is within the range 0.05 to 0.9 seconds.

9. The shift actuator assembly according to claim 2, wherein the shift actuator is a shift lever.

10. The shift actuator assembly according to claim 2, wherein the shift actuator (2) is a rotary knob.

Description

[0016] The invention will in the following be described in connection with an exemplary embodiment and by illustrating the performance of such shift actuator assembly according to the present invention, wherein in the drawings:

[0017] FIG. 1 shows a schematical cross-sectional view of a shift actuator according to the invention which is includes a rotary knob,

[0018] FIG. 2 shows a graph of the angular velocity of the rotary knob of FIG. 1 as a function of time when the rotary knob is rotated through several subsequent predetermined shift positions; and

[0019] FIG. 3 shows a graph of the torque needed to rotate the rotary knob as a function of time when the rotary knob is rotated through several subsequent predetermined shift positions.

[0020] FIG. 1 shows a schematical cross-section of a shift actuator which includes a rotary knob 2. The rotary knob 2 is fixed to a shaft 4 which is mounted in a housing (not shown) so as to be rotatable around its longitudinal axis. A rotor 6 is fixed to the shaft 4. The rotor 6 is disposed within a housing 8 and is freely rotatable therein. At its outer periphery the rotor projects into an annular chamber 10 within the housing, which chamber is filled with a magneto-rheological fluid. Disposed adjacent to the chamber 10 filled with magneto-rheological fluid a coil 12 is provided in the housing 8. If electricity is supplied to the coil 12 a magnet field is generated which also penetrates the chamber 10 and the magneto-rheological fluid. In response to a magnet field the viscosity of the fluid abruptly rises, and consequently the shear forces of the magneto-rheological fluid in the chamber 10 drastically increase so that a high braking force is exerted on the rotor 6 and thus on the rotary knob 2 which brings the rotary knob to a stop. For further details regarding design and operation of magneto-rheological brake mechanisms reference is made to US 2013/0175132 A1.

[0021] Supply of electricity to the coil 12 is controlled by a controller 20. The controller 20 is further connected to an angular position sensor 24 which senses a signal representative for the angular position of the shaft 4.

[0022] There is furthermore a mechanical detent mechanism, namely a detent plunger 30 which is urged by a spring 32 onto the surface of the shaft 4. In this region the surface of the shaft 4 is provided with a detent track. The detent track comprises a number of recesses which are circumferentially distributed around the circumference of the shaft 4. For each of the predetermined positions of the rotary knob 2 there is a corresponding recess which comes into engagement with the detent plunger 30 at the particular predetermined position of the rotary knob 2. One of these detent recesses is indicated in FIG. 1 by a dot 34 in the middle of the shaft 4.

[0023] The controller 20 is arranged to supply electricity to the coil 12 to generate a magnetic field such that the magneto-rheological brake is active when the rotary knob 2 reaches one of its predetermined angular positions and the mechanical detent mechanism also became engaged. In fact, the controller 20 has to supply electricity to the coil 12 a short time in advance, before the rotary knob 2 reaches a particular of the predetermined positions in order to take into account the response time of the magneto-rheological fluid. This can be achieved by starting supply of electricity to the coil already at a small angular distance before the predetermined angular position, which small angular distance is chosen such that this small angular distance is equal to the response time times an estimated average angular velocity of the rotary knob 2.

[0024] FIG. 2 shows a graph of the angular velocity as a function of time when the rotary knob 2 is rotated by applying a given constant torque to rotate the rotary knob to pass several subsequent predetermined shift positions, for example P, R, N, D. Between subsequent predetermined shift positions the constant torque applied results in a constant angular velocity (a relative angular velocity of 100% is shown). After about 0.5 s the rotary knob approaches the next predetermined shift position. The controller receives information from the angular position sensor 24 and activates the adaptive brake mechanism to apply a predetermined maximal brake force. This brake or resistance force is chosen such that it is not possible to rotate the knob further by manual force so that the rotary knob stops, i.e. the angular velocity drops to zero. The rotary knob is arrested at the shift position for a predetermined period of time, in FIG. 2 for about 0.5 s. This sequence is repeated while the rotary knob is rotated along the sequence of predetermined shift positions over the time interval shown in FIG. 2.

[0025] FIG. 3 shows, for same rotary movement of the rotary knob along the sequence of predetermined shift positions as in FIG. 2, the torque needed to rotate the rotary knob. The torque is indicated in arbitrary units. Between predetermined shift positions a small torque is needed to overcome friction to rotate the rotary knob. When the rotary knob is approaching one of the predetermined shift positions after about 0.5 s the controller activates the adaptive brake mechanism to apply a maximal braking or resistance force. This maximal resistance force is chosen such that the torque (Max. T) that would be needed to overcome the resistance to rotate the rotary knob is so high that is exceeds any manual force a human driver could normally apply. Therefore, the rotary knob is stopped for the predetermined period of time, i.e. the angular velocity is zero as shown in FIG. 2 when the adaptive brake mechanism is activated. After the predetermined period of time of activation of the adaptive brake mechanism the controller deactivates adaptive brake mechanism so that the rotary knob can be rotated further by applying a small torque as shown in FIG. 3 until the rotary knob approaches the next of the predetermined shift positions.

[0026] FIGS. 2 and 3 show an embodiment of the invention in which the shift actuator is forced to stop at each of the predetermined shift positions unconditionally. As mentioned above, there is an alternative concept that the forced stop at a predetermined shift position is skipped in case the shift actuator has a velocity above a threshold velocity when reaching this predetermined shift position. The latter embodiment is not shown in the drawings.

[0027] An adaptive brake mechanism utilizing the effect of a magneto-rheological fluid has a quick response time. However, there is a brief, known delay time between activation and full effect of the brake mechanism. The controller is adapted to take into account this delay time by activating the adaptive brake mechanism already in advance at a position of the shift actuator at a short distance away from the predetermined shift position. This distance is chosen such that at a typical movement velocity of the shift actuator the known response time of the adaptive brake mechanism is over when the shift actuator reaches the predetermined shift position.