Inhibitor switch

Electricity: circuit makers and breakers – Special application – Actuated concurrently with operation or use of art device

Reexamination Certificate

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Details

C200S061280

Reexamination Certificate

active

06506988

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inhibitor switch for detecting change gear range positions of an automatic transmission.
2. Description of the Related Art
Conventionally, as an inhibitor switch, there has been an inhibitor switch which makes a movable contact rotating along with an axial rotation of a manual valve shaft of an automatic transmission slidably moved relative to a fixed contact mounted on a transmission case side of the above mentioned automatic transmission and detects the changeover of a change gear range of the automatic transmission in response to the position of the movable contact to the fixed contact. With respect to the detection using such a slidable contact, there has been a problem that the contact control of the surface of the contact is extremely difficult and hence, there are so much noise signals that the control with a microcomputer becomes difficult.
To the contrary, an inhibitor switch adopting a non-contacting method can eliminate noise signals derived from the contacting and hence, it is suitable for the control using a microcomputer. As such an inhibitor switch adopting the non-contacting method, there has been an inhibitor switch which provides magnetic sensors at respective change gear positions and detects the changeover of the change gear range based on ON/OFF signals of respective sensors or an inhibitor switch which reduces the number of the magnetic sensors and detects the changeover of the change gear range based on the combination of signals of the magnetic sensors.
As the inhibitor switch which provides magnetic sensors at respective change gear positions, there has been an inhibitor switch shown in
FIG. 18
to
FIG. 20
, which is described in Japanese Utility Model Publication No. 101623/1980, for example. To briefly explain the constitution of the inhibitor switch first of all, a rotary element
105
is mounted on a manual valve shaft
103
of an automatic transmission
101
and a permanent magnet
107
is supported on the rotary element
105
. Further, on a housing
109
side of the automatic transmission
101
, magnetic sensors
111
which are arranged corresponding to change gear range positions are supported. These magnetic sensors
111
are constituted by lead switches.
Then, when the permanent magnet
107
is moved due to the rotation of the manual valve shaft
103
in response to the changeover of the change gear range, a contact of any one of magnetic sensors
111
which faces this permanent magnet
107
in an opposed manner is closed and any one of the change gear range positions can be detected by reading the resistance values connected to respective magnetic sensors
111
which are different each other.
However, in such a structure, it is necessary to provide the magnetic sensors
111
at respective change gear positions so that the number of magnetic sensors becomes large and there exits a limit with respect to the miniaturization of the inhibitor switch. Accordingly, it has been almost difficult to arrange the inhibitor switch in the inside of a transmission case.
Further, the inhibitor switch having the above mentioned structure has a problem that there exists a limit with respect to an accurate detection. That is, when the manual valve shaft
103
is rotated due to the transmission manipulation and the permanent magnet
107
is moved between respective magnetic sensors
111
in response to this rotation, at an intermediate position between these magnetic sensors
111
, a state that the magnetic sensors
111
disposed in front of and behind the magnetic sensor
107
turn OFF or a state that both of such magnetic sensors
111
turn ON may arise. When both of the magnetic sensors
111
turn OFF, it is impossible to detect where the change gear range position of the automatic transmission
101
exists while when both of the magnetic sensors
101
turn ON, it becomes impossible to detect which position the change gear range exists.
Accordingly, in the state that the permanent magnet
107
is disposed in such an intermediate position, when the inhibitor switch suffers from a failure, it has been impossible to detect the change gear range position where the failure occurs so that the detection accuracy is low. Accordingly, the detection having an improved reliability has been requested.
In the inhibitor switch which reduces the number of magnetic sensors and performs the detection based on the combination of signals of the magnetic sensors, by changing the combination of sensor signals at respective change gear range positions, the reliability of the inhibitor switch when the sensor suffers from the failure can be enhanced. That is, in the above-mentioned structure which turns ON/OFF the magnetic sensors
111
of respective change gear ranges, when any one of the magnetic sensors
111
is connected due to a failure such as a short-circuiting or the like, even when a shift lever is manipulated from N (neutral range) to D (drive range), there is a possibility that a signal indicative of P (parking range) is outputted or the like. With use of the above-mentioned combination of signals, such an erroneous outputting can be suppressed.
However, only with the mere combination of several kinds of signals corresponding to the change gear range positions, when any one of the magnetic sensors suffers from the failure, it gives rise to a common combination mode at different change gear range positions and there is a possibility that the correct signals can not be distinguished from error signals. Accordingly, in a usual case, the combination modes are prevented from becoming in common with the use of a combination signal which is added with one bit to the combination signal.
That is, when the combination modes of signals are made in common at different change gear ranges due to the failure and hence, a signal that the change gear range is changed directly from P to N is outputted or the like, it is possible to distinguish the correct signals from error signals by storing conditions that there is no possibility that the change gear range is directly shifted from P to N into the microcomputer. However, at an end portion such as P, even when the shift lever is not manipulated, a signal that the change gear range is shifted from P is outputted and hence, there is a possibility that the accurate signal can not be distinguished from the error signal. Accordingly, in a usual case, the provision is made such that one bit is added to the combination signal so that even when any one of the magnetic sensors suffers from the failure, signals which agree with each other are not generated at respective detection positions. Accordingly, the number of magnetic sensors is increased correspondingly so that it also gives rise to a problem that the inhibitor switch becomes large-sized.
Further, the inhibitor switch also has a problem that the detection accuracy at the intermediate position is low as in the case of the previously-mentioned inhibitor switch.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an inhibitor switch, which can miniaturize the constitution thereof and also can remarkably enhance the detection reliability.
The inhibitor switch according to the present invention has the following characteristics.
(1) The inhibitor switch according to the present invention comprises a permanent magnet and a magnetic sensor which detects a magnetic force of the permanent magnet in a non-contacting state and outputting a linear change in a voltage value in response to a change in a relative position between the permanent magnet and the magnetic sensor, wherein either one of the permanent magnet and the magnetic sensor is mounted on a manual valve shaft side for changing over a change gear range position of the automatic transmission by operating a manual valve of the automatic transmission in an interlocking manner with the manual valve shaft, and the other one of the permanent magnet and the magnetic sensor is mounted on a transmission case side of the automatic tra

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