192 clutches and power-stop control – Transmission and brake – Motor vehicle
Reexamination Certificate
2002-04-25
2004-02-10
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Transmission and brake
Motor vehicle
C074S335000, C074S473120
Reexamination Certificate
active
06688448
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a device for shifting a mechanical shifting device between a first shifting state and at least one second shifting state, especially for engaging and disengaging a parking brake for an automatic transmission.
BACKGROUND OF THE INVENTION
Automatic transmissions with a mechanical parking brake have been known from the state of the art. At least four modes of operation, which correspond to the following shift positions of a gearshift lever, namely, “P,” “R,” “N” and “D,” are usually associated with a conventional automatic transmission for motor vehicles. In the individual shift positions, “P” designates the state “Parking,” in which the transmission is usually blocked mechanically against the transmission of movements by the parking brake. “R” designates the “reverse movement,” “D” designates the “forward movement,” and the shift position “N” corresponds to the “neutral operation,” in which there is no mechanical coupling between the engine and the wheels.
A usual safety requirement is that the mechanical parking brake of the automatic transmission can always be engaged or is always engaged with the vehicle not moving.
This safety requirement can be satisfied relatively easily with an automatic shifting, in which a mechanical transmission member, e.g., a gearshift cable or a gearshift linkage, is provided between the gearshift lever and the automatic transmission, because a coupling is forced to take place between the actual shifting state of the transmission and the indicated shifting state of the gearshift lever because of the mechanical transmission member, at any rate as long as the mechanical transmission member is not defective. The gearshift lever can be brought into the shift position “P” and the automatic transmission can be shifted via the mechanical coupling into the corresponding state with the parking brake engaged even in case of a power failure in the vehicle.
However, electromechanical transmission members have recently been developed for the automatic shifting, wherein a mechanical coupling between the automatic transmission and the gearshift lever is no longer present. The shifting states of the gearshift lever are detected electronically in this case and are sent in the form of electric signals associated with the shifting states to a device (transmission actuator mechanism), which brings the automatic transmission into the mode of operation corresponding to the shift position of the gearshift lever instead of the mechanical transmission member. Such an electromechanical shifting operation is also called “shift by wire” in English.
However, it is possible with the electromechanical coupling between the gearshift lever and the automatic transmission that in the case of a power failure in the vehicle, a different mode of operation is set for the transmission than is indicated by the gearshift lever, because the gearshift lever can be actuated independently from the transmission actuator mechanism. However, the above-mentioned safety requirement can thus no longer be satisfied in all cases.
SUMMARY OF THE INVENTION
The basic object of the present invention is to provide a device with which the above-mentioned safety requirement for an automatic transmission can be satisfied even in case of the use of an electromechanical transmission member.
The device according to the present invention for shifting the gears of a mechanical shifting device between a first shifting state and at least one second shifting state has an adjusting member coupled with the shifting device shifting between the shifting states, wherein the adjusting member can be coupled with a control member via a coupling device.
A certain position of the adjusting member is associated with each shifting state of the shifting device, so that the shifting device can be shifted into any desired shifting state from the first shifting state and from the at least one second shifting state by the adjusting member being brought into the position associated with the desired shifting state. A change in the position of the adjusting member may be brought about, e.g., by displacement, rotation or pivoting.
In the coupled state, the adjusting member can be driven or actuated by the control member, and the control member itself is actuated or driven by a drive device. The adjusting member can consequently be brought into the different positions associated with the shifting states by driving the control member. A certain position of the control member, into which this control member can be brought by means of the drive means, is in turn associated for this with each of the aforementioned positions of the adjusting member.
The coupling device can be actuated by means of an electric signal, i.e., the adjusting member is coupled with the control member by this coupling device when the electric signal assumes a certain state. It may be nearly any state as long as it is ensured that it differs from the signal state occurring in case of loss of the electric signal, e.g., a power failure. In case of loss of the electric signal, the coupling between the adjusting member and the control member is then released by the coupling device, so that these two members are again uncoupled from one another.
For the reliable resetting of the shifting device into the first shifting state in case of loss of the electric signal, a spring means is coupled with the adjusting member and with an abutment, the spring means being tensioned in each shifting state that is different from the first shifting state in relation to the adjusting member such that in case of an uncoupling between the adjusting member and the control member, the adjusting member is shifted by the spring means into the position associated with the first shifting state while the tension of the spring means decreases, as a result of which the shifting device is also shifted into the first shifting state. Since the spring means is coupled with the adjusting member and the abutment, the tension of the spring means that is necessary for the resetting of the adjusting member into the position associated with the first shifting state can be built up by a change in the relative position between the adjusting member and the abutment or by a relative movement of the adjusting member and the abutment.
The device according to the present invention may be used wherever a certain shifting state of at least two shifting states of a mechanical shifting device shall be engaged with certainty in case of a power failure. However, the device according to the present invention is preferably used to engage and disengage a parking brake of an automatic transmission. The shifting device is now designed as the parking brake of the automatic transmission, where the first shifting state corresponds to the state of the engaged parking brake and the at least one second shifting state corresponds to the state of the disengaged parking brake.
The adjusting member may be coupled with the shifting device with a common lever mechanism. However, the adjusting member is preferably coupled with the shifting device via a shaft, in which case the shifting device is shifted by a rotary movement of the shaft between the first and at least one second shifting states. The adjusting member is connected to the shaft, rotating with it in unison in this case.
In the coupled state, the control member may transmit a translatory movement, which can be converted at the adjusting member into a rotating movement for shifting between the different states. However, the control member is preferably mounted rotatably in relation to the shaft, in which case the adjusting member and the control member are connected to one another rotating in unison in the coupled state. The shaft can thus be rotated by a rotary movement of the control member in the coupled state via the adjusting member for shifting the shifting device between the shifting states.
The coupled state of the adjusting member and the control member may be embodied by means of a common positive-locking and non-pos
Börgerding Reimund
Giefer Andreas
Meyer Jörg
Rake Ludger
Bonck Rodney H.
McGlew & Tuttle P.C.
ZF Lemförder Metallwaren AG
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