Door Lock Position Sensor

1. Field of the Invention

The present invention relates in general to a position sensor for sensing a position of a movable member, and more particularly to a position sensor which is installed in a door lock to sense or detect the position of a pivotal component of the door lock.

2. Description of the Prior Art

Nowadays, a so-called passive seat belt system has been proposed and put into practical use in the field of passenger motor vehicles, which is designed to automatically move a seat belt to a passenger restraining position when the vehicle door is closed.

For sensing the door closing, various sensors have been hitherto proposed, two of which will be outlined in the following in order to clarify the task of the invention. They are disclosed in Japanese Utility Model Second Provisional Publication No. 61-22011 and Japanese Patent Second Provisional Publication No. 61-49471, respectively.

In the former case, as is shown in FIG. 3 of the accompanying drawings, a micro switch "MS" is mounted in a door lock at a position above a latch plate "L". An actuating pin "A" of the switch "MS" is in contact with a peripheral side surface of the latch plate "L" as shown. Upon closing of the vehicle door, a striker "ST" secured to the vehicle body pushes back the latch plate "L" to the full-latch position as shown by a phantom line. During this, the peripheral side surface of the latch plate "L" moves and thus pushes the actuating pin "A" thereby causing ON or OFF condition of the switch "MS". With this, the open and close conditions of the door are detected.

In the latter case, a rotary switch is mounted outside of the door lock having its rotating shaft coaxially connected with a pivot shaft of the latch plate. Upon pivoting of the latch plate due to closing of the door, the rotating shaft is forced to pivot thereby causing ON or OFF condition of the rotary switch.

However, due to the inherent constructions, the above-mentioned conventional sensors have the following drawbacks.

That is, in the former case, the micro switch "MS" is easily affected by cold weather and dust. When, for example in winter, some parts of the switch "MS" are iced even weakly, the actuating pin "A" fails to closely follow the movement of the peripheral side surface of the latch plate "L". This causes malfunction of the switch "MS".

In the latter case, the entire construction of the door lock is bulky because of presence of the rotary switch coaxially mounted thereon. This makes installation of the door lock in the door difficult or at least troublesome. Furthermore, because the rotary switch is arranged outside of the door lock proper, it fails to have a satisfied resistance against water and dust.

It is therefore an object of the present invention to provide a door lock position sensor which is free of the above-mentioned drawbacks.

According to the present invention, there is provided, in a door lock having a housing, and a pivotal member pivotally connected to the housing through a pivotal shaft, an improved position sensor. The position sensor comprises a rotary switch securely connected to the housing, the rotary switch having a rotating shaft which causes ON and OFF conditions of the switch upon rotation thereof, and a link mechanism operatively interposed between the rotating shaft and the pivotal member so that a pivotal movement of the pivotal member induces a simultaneous pivotal movement of the rotating shaft of the rotary switch, wherein the rotary switch is placed at a position other than a position where an axis of the pivotal shaft of the pivotal member is placed.

Other objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a front view of a door lock to which a position sensor according to the present invention is practically applied, with a cover plate removed for clarification of the interior of the door lock;

FIG. 2 is an exploded view of essential parts of the door lock position sensor; and

FIG. 3 is a view similar to FIG. 1, but showing a conventional door lock position sensor.

In the following, the words, "upward", "downward", "above", "below", "right", "left" and the like are to be understood with respect to the drawing on which the corresponding part is illustrated.

Referring to FIGS. 1 and 2, particularly FIG. 1, there is shown a door lock 1 to which a position sensor according to the present invention is practically applied.

The door lock 1 comprises a base plate 2 on which a known latching and unlatching mechanism is mounted. In FIG. 1, the mechanism is placed behind the base plate 2 and thus the same is not viewed from this side. Denoted by numeral 3 is a plastic housing which houses therein essential parts of the door lock 1. A cover plate (not shown) is secured to the housing 3 through bolts, which conceals the interior of the housing 3.

The housing 3 is formed at its generally middle portion with a guide groove 3a into which a striker 8 secured to a vehicle body gets upon closing of the door. Designated by numeral 5 is a generally U-shaped latch plate which is pivotally held by a pivot shaft 4 which extends between the bottom of the housing 3 and the cover plate (not shown) above the guide groove 3a. The latch plate 5 is thus formed with first and second pawl portions 5a and 5b between which a recess 5d is defined. These first and second pawl portions 5a and 5b are exposed to the guide groove 3a.

Like a conventional door lock, the latch plate 5 can assume three particular positions, which are a release position as shown by a phantom line in FIG. 1, a full-latch position as shown by a solid line and a half-latch position (not shown) defined between the release and full-latch positions. When the latch plate 5 comes to the release position, the second pawl portion 5b thereof is brought into contact with a stopper 6 defined by the housing 3. In this condition, the door lock 1 is ready for receiving or catching the striker 8.

Below the guide groove 3a, there is arranged a shaft 7 which extends in parallel with the pivot shaft 4 of the latch plate 5. That is, the shaft 7 passes through the base plate 2, the bottom of the housing 3 and the cover plate and is rotatable about its axis. An arcuate pawl 7a is integrally connected to the shaft 7 to rotate therewith.

An open lever (not shown) is secured to the shaft 7 behind the base plate 2, so that the open lever and the pawl 7a rotate together. In response to operation of the open lever, the pawl 7a is latchingly engageable with the first and second pawl portions 5a and 5b of the latch plate 5 allowing the latch plate 5 to assume the above-mentioned three positions.

When the door is closed, the striker 8 on the vehicle body gets into the guide groove 3a and pushes back the latch plate 5 to the full-latch position (as shown by a solid line) getting over the second pawl portion 5b, wherein the latch plate 5 fully latches the striker 8 having the second pawl portion 5b thereof sustained by the pawl 7a. That is, in this full-latch position, a counterclockwise rotation of the latch plate 5 is suppressed.

When the door lock 1 assumes the half-latch position, the first pawl portion 5a of the latch plate 5 engages at its inboard side 5c with the pawl 7a. Under this condition, the striker 8 is halfly latched by the latch plate 5.

When, in response to rotation of the open lever (not shown), the pawl 7a is disengaged from a traveling way of the outermost free end (viz., the tops of the first and second pawl portions 5a and 5b) of the latch plate 5, the latch plate 5 is released from the pawl 7a thereby cancelling the full or half latched condition of the striker 8. Thus, the door is ready for opening. When thereafter the door is opened, the latch plate 5 is pivoted to the release position (as shown by the phantom line) due to a work of a biasing spring 9 which constantly biases the latch plate 5 in a counterclockwise direction in FIG. 1.

Designated by numeral 10 is a shock absorber which is placed at the inmost end of the guide groove 3a for softly stopping the striker 8.

The position sensor according to the present invention is installed in the door lock 1 in such a manner as will be described in the following.

Within the housing 3, there is disposed a rotary switch 11 which is placed near the shaft 4 of the latch plate 5. A screw 12 is used for detachably fastening the switch 11 to the housing 3.

As is best seen from FIG. 2, a link mechanism comprising first and second links 14 and 15 is arranged between the rotary switch 11 and the latch plate 5. The first link 14 has at its both ends shorter and longer pins 14a and 14b respectively, while, the second link 15 has at its both ends circular and rectangular openings 15a and 15b respectively. The longer pin 14b is pivotally engaged with the circular opening 15a, so that the two links 14 and 15 are pivotally movable relative to each other. The shorter pin 14a of the first link 14 is pivotally engaged with an opening 13 formed in the latch plate 5, while the rectangular opening 15b of the second link 15 is unmovably engaged with a rectangular projection 11b of a rotating shaft 11a of the rotary switch 11. As is seen from FIG. 1, the opening 13 is formed in an upper part of the second pawl portion 5b of the latch plate 5. Preferably, the rotating shaft 11a is arranged in parallel with the pivot shaft 4 of the latch plate 5. The detail of the rotary switch 11 will be described hereinafter. With the link mechanism as described in the above, it will be appreciated that the pivotal movement of the latch plate 5 causes a simultaneous pivotal movement of the rotating shaft 11a of the rotary switch 11. It is to be noted that when the latch plate 5 assumes the release position as shown by the phantom line in FIG. 1, the first and second links 14 and 15 define therebetween an acuate angle, while, when the latch plate 5 assumes the full-latch position as shown by the solid line, the two links 14 and 15 define therebetween an obtuse angle. Thus, the angular velocity of the second link 15 gradually increases when the latch plate 5 is pivoted in a direction from the release position to the full-latch position.

For smoothing the pivotal movements of the first and second links 14 and 15, an arcuate guide groove 16 is formed in the housing 3, to which groove a leading end of the longer pin 14b (viz., the end of the pin projected from the opening 15a of the second link 15) is slidably engaged. The groove 16 is concentric with the rotating shaft 11a of the rotary switch 11. With the provision of the concentric groove 16, the rotating shaft 11a of the rotary switch 11 is prevented from being forced radially outwardly during the pivotal movement of the latch plate 5. When the cover plate (not shown) is properly mounted on the housing 3, the inner surface of the cover plate approaches very closely to the first link 14 thereby preventing disjointing of the links 14 and 15 from their associated parts 5 and 11a.

The rotary switch 11 used in the invention is described in U.S. patent application No. 079,394 filed July 30, 1987 by the same applicant. The switch 11 is of a sealed rotary switch which is so designed that when the rotating shaft 11a is turned by a given angle, ON or OFF condition of the switch 11 is changed to the other condition. Of course, other sealed rotary switches are also usable in the invention.

When, with the construction as described hereinabove, the latch plate 5 is pivoted to the full-latch position as shown by the solid line in FIG. 1, the link mechanism causes the rotating shaft 11a of the rotary switch 11 to turn in a clockwise direction. With this, the switch 11 issues ON or OFF signal representing that the door is closed. When the latch plate 5 is pivoted from this full-latch position in a counterclockwise direction in FIG. 1, the link mechanism causes the rotary switch 11 to issue OFF or ON signal representing that the door is opened.

When the latch plate 5 is pivoted to the release position as shown by the phantom line, the link mechanism causes the rotating shaft 11a to turn in a counterclockwise direction by a given angle. With this, the rotary switch 11 issues OFF or ON signal representative of the opening of the door.

In the following, advantages of the present invention will be described.

First, since the pivotal latch plate of the door lock and the rotary switch are connected through a mechanically robust link mechanism, the movement of the latch plate is assuredly transmitted to the rotating shaft of the switch thereby achieving a high reliability of the position sensor. That is, even when some parts of the rotary switch are iced in winter or contaminated with dust, the rotating shaft of the rotary switch is assuredly rotated upon movement of the associated latch plate of the door lock.

Second, since the position sensor including the rotary switch and the link mechanism (or arm) is arranged in a manner to effectively use a space defined in the door lock, the door lock can be constructed compact in size. In fact, unlike the afore-mentioned conventional sensor arrangement wherein the rotary switch is coaxially arranged with respect to the pivotal shaft of the latch plate, the rotary switch is arranged beside the pivotal shaft of the latch plate in accordance with the present invention. This allows reduction in thickness of the entire construction of the door lock.