192 clutches and power-stop control – Transmission and brake – Motor vehicle
Reexamination Certificate
2003-01-23
2004-12-07
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Transmission and brake
Motor vehicle
C074S473240, C074S532000, C192S220200, C361S160000
Reexamination Certificate
active
06827195
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a locking and unlocking mechanism with an electromagnet, which mechanism is used preferably to assume a key and/or shift lock function in motor vehicles.
BACKGROUND OF THE INVENTION
Mechanisms that block or release certain mechanical elements for manual actuation by a user as a function of preset states are needed for a very great variety of purposes. A typical application of such mechanisms is the key and/or shift lock function in a motor vehicle with automatic shifting. The purpose of the locking and unlocking mechanism is to make possible the actuation of the selector lever, especially the shifting from the “Park” position into the reverse position or into the “Drive” position, e.g., only if the ignition key is in a certain position in the ignition lock or when the brake [pedal] is depressed. Such locking and unlocking mechanisms are embodied with the use of an electromagnet, which is energized depending on the desired behavior (locking or unlocking) in corresponding positions of the ignition key and/or state of actuation of the brake pedal.
One example of such a locking mechanism is known from DE 198 25 479 A1. The mechanism comprises essentially a check plate, which is pivotable with the selector lever, an electromagnet fastened to the selector lever housing, and a permanent magnet arranged on the check plate. A blocking pin, which engages openings of the gear shift gate, is blocked or released for moving it out of the said openings by means of the check plate via an unlocking tongue.
In the device described in the document, the electromagnet is attracted by the permanent magnet in the non-energized state and the permanent magnet is held as a result at the electromagnet together with the check plate. As a result, the blocking pin is blocked against being moved out of an opening of the gear shifting gate by means of an unlocking tongue of the check plate. It e.g., the electromagnet at the selector lever housing is energized, e.g., by actuating the brake pedal, a magnetic field is built up, by which the permanent magnet that is in contact with it is repelled together with the check plate and the blocking pin is released by the unlocking tongue of the check plate.
The shift lever can be brought from the “Park” position into the “Drive” position only by a corresponding actuation by the user. The attraction and repelling of the permanent magnet by the electromagnet is associated with an undesired noise generation. The noise level additionally depends on the actual onboard voltage present, which is usually between 9V and 16V. A possibility of eliminating at least the effects of possible fluctuations in the onboard voltage and minimizing the noise level at the same time is to send a direct voltage-rated pulse width signal to the electromagnet. In case of energization of the electromagnet, a pulsating voltage (PWM voltage; PWM =English Pulse Width Modulation) with constant effective value, preferably 9 V, is sent to the electromagnet.
Any fluctuations in the voltage of the onboard system are converted by the pulse width modulation providing the PWM voltage only in the form of changed pulse widths of the pulse width signal sent to the electromagnet. Despite the noise reduction resulting herefrom, the noise which continues to occur during locking and unlocking, which is caused by the impact of the electromagnet with metallic parts or a permanent magnet, is sometimes still felt to be disturbing.
SUMMARY OF THE INVENTION
The object of the present invention is to design a locking and unlocking mechanism, by which the noise generation during the transition from one state into the other is reduced, so that any noise is practically not perceived any longer.
The object is accomplished with a locking and unlocking mechanism having the features of the principal claim. Advantageous embodiments or variants of the present invention are described in the subclaims. The locking and unlocking mechanism, which is preferably used to embody a key and/or shift lock function in a motor vehicle, is based in the known manner on the act that mechanical elements are blocked or released for manual actuation depending on the preset states, and this is achieved by energizing an electromagnet. Metallic parts are attracted and held or at least a permanent magnet is repelled during the energization of the electromagnet by the magnetic field built up as a result. To energize the electromagnet, a pulsating electric voltage is used as a direct voltage-rated pulse width signal (PWM voltage). However, the effective value of the PWM voltage, time-controlled by a circuit unit associated with the pulse width modulator, is increased according to the present invention at the beginning of a phase of energization over at least three voltage pulses from an off-load voltage value to a preset final voltage value. Conversely, the effective value of the PWM voltage again drops at the end of the phase of energization over at least three voltage pulses to a resting voltage value that is no longer sufficient for attracting metallic parts or for repelling the permanent magnet or the permanent magnets.
The three voltage pulses during the rise in the effective value also comprise the last offload voltage pulse before the rise in the effective value and the first final voltage pulse after this last off-load voltage pulse. Furthermore, the three voltage pulses during the drop of the effective value comprise the last final voltage pulse before the drop of the effective value and the first offload voltage pulse after this last final voltage pulse.
The rise and drop of the effective value of the PWM voltage takes place with at least three different voltage values, and the effective value is controlled by varying the pulse-width repetition rate of the PWM voltage by means of the circuit unit. The off-load voltage value and the final voltage value are also counted as voltage values during the rise or drop of the effective value, so that at least one voltage value of the different voltage values is located between the off-load voltage value and the final voltage value.
The effective value, which forms a square mean value, always applies here only to the particular period to be considered, and the duration of a period is obtained from the time period between the beginning of a pulse and the beginning of the next pulse. If the pulse width repetition rate changes from one period to the next, the effective value changes as a function of the pulse width repetition rate as well.
At the beginning of the rise, the amount of the change in the effective value between two consecutive pulses is preferably greater than near the end of the voltage rise. Furthermore, the amount of the change in the effective value between two consecutive pulses is greater at the beginning of the voltage drop than near the end of the voltage drop.
A locking and unlocking mechanism designed in this manner can be used, of course, not only in connection with the embodiment of the key and/or shift lock function in a motor vehicle. The principle of the present invention can rather be readily applied to a plurality of applications. Thus, the description, which is related below primarily to the application in a motor vehicle, does not represent any limitation of the subject of the present invention.
Corresponding to a practical design of the locking and unlocking mechanism, the effective value of the PWM voltage rises exponentially degressively at the beginning of the phase of energization of the electromagnet, whereas it drops exponentially degressively at the end of the phase of energization. The time constant for reaching the preset effective voltage during energization and for reaching the off-load voltage during an interruption of the energization can be set in the circuit unit directly associated with the pulse width modulator. This circuit unit may be a timer or, in a possible embodiment of the present invention, an RC network, whose time constant determines the delay in the rise or drop of the effect
Bonck Rodney H.
ZF Lemförder Metallwaren AG
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