GB2293152A - Control device for an electrically powered hinged rearview mirror for a vehicle - Google Patents

Description

Control device for an electrically powered hinged rearview mirror for a vehicle The present invention relates to an electrically powered hinged rearview mirror for a vehicle and especially to a control device for an electrically powered hinged rearview mirror for an automobile controlled by using a latching relay.

It has already been proposed to have an electrically powered hinged rearview mirror for an automobile to be constructed to project from a vehicle body side when in use and to be pivoted inwardly towards the vehicle body when the automobile is to be parked. For example, as disclosed in Japanese Utility Model Registration Application Publication Sho 63-169341, an electrically-powered hinged rearview mirror may comprise a motor fixed on a frame of a mirror body to turn the mirror body on its hinge electrically, a shaft extending upwardly from a base on which the mirror body is mounted, a gear engageably and removably mounted on the shaft and a speed reduction mechanism provided between the motor and the gear.The gear is disposed around the shaft and has a clutch mechanism so that when the mirror body is turned electrically, the gear is in a fixed condition with the shaft, while the mirror body is forced to turn, the gear is free of the shaft. An end gear of the speed reduction mechanism engages a clutch gear, both the speed reduction mechanism containing the end gear and the frame for supporting said mechanism are normally and counter rotated, centred around the shaft, by operation of the motor, and the mirror body is held in an extended position or a retracted position.

The turning mechanism for the mirror body will be described. Mirror body positioning means comprise a stopper plate and steel balls and are provided between a shaft root portion which extends upwardly from an extension of a base and a frame root portion.

Steel balls are supported on a concave spherical seat which is formed on an under surface of the frame root portion so as to rotate with the frame when the mirror body is turned, so that when the mirror body reaches its fully extended position, the steel balls contact an abutment shoulder of a buffer plate.

A convex portion is provided on a flange portion of the shaft which is fixed on the extension of the base, and arc-shaped grooves are provided under the frame root portion to receive the said convex portion so as to comprise turning limit-stop means. When the frame turns, centred around the shaft, the arc-shaped grooves of the frame side are guided by the convex portion and turn. When the mirror body is held in the retracted position, the convex portion which constitutes part of the turning limitstop means for the mirror body in a retracted position abuts one end of arc-shaped grooves to inhibit further turning of the mirror body.

The motor driving circuit is cut out to stop the mirror body turning once it has reached either its fully extended position or its retracted position. The cutting out of the motor driving circuit is achieved by a mechanical switch (limit switch or a plate contact switch or the like), and as disclosed in Japanese Utility Model Registration Application Publication No. Hei 4-76196, there is another method to utilize a characteristic of a PTC component (a positive temperature coefficient device), and the motor driving circuit may be cut out by a rapid increased resistance value caused by an increased electric current when the motor rotation is locked. Furthermore it has been proposed to control the motor by a sensor such as a photo reflector or a magnetic induction component or element so as to detect the motor rotation, as in US-A5,315,442.

However in a conventional method of cutting out the motor driving circuit as described above such as a mechanical switching method, it is difficult to switch a circuit so that it is operated at either the fully extended position of the mirror or the fully retracted position, and erroneous operation such as an imperfect contact or the like is easily caused by foreign particles in the rotating contact portion. Moreover in the method of using a PTC component, during a large time lag from the occurrence of the overload on the motor for a given temperature of the PTC component, the electric power remains supplied to the motor.Consequently there is a risk that the positioning accuracy for the mirror body is so poor that the mirror body moves beyond the desired position, the motor is damaged by overheating, the durability of parts is reduced because of the driving circuit being loaded excessively, or heat generation within the equipment may be caused by a continuous over-current through the circuit so that the circuit parts become inferior, or possibly even so that circuit parts ignite.

Moreover in the method of detecting the motor rotation by a magnetic sensor element there is a risk that dust particles or other contaminants stick to the sensor portion and cause a wrong operation of the device.

Furthermore, owing to a complicated electronic circuit composed of an amplifier circuit or a driving circuit or the like which is necessary for forwarding a sensor signal to the motor control, the system is expensive.

It is an aim of the present invention to provide a control device for an electrically powered hinged rearview mirror which is capable of obviating the foregoing problems and which can have a simple circuit.

Accordingly, the present invention is directed to a control device for an electrically powered hinged rearview mirror for a vehicle comprising a shaft extending upwardly from a base; a mirror body having a motor; turning limit-stop means mounted around the shaft; the mirror body being turned around the shaft by a normal and a reverse rotation of the motor, the turning being stopped at an extended position and a retracted position of the mirror body by the turning limit-stop means; in which the control device further comprises a switching circuit for changing the electrical polarity of a voltage applied to the motor so as to turn the mirror body to the extended position or the retracted position, and a control circuit which has a latching relay and a shunt resistance for interrupting a driving current to the motor when the mirror body reaches the extended position and the retracted position and the motor is locked against rotation by the turning limit-stop means, and in which in the control circuit, the motor is locked when the mirror body reaches the extended position and the retracted position, a voltage occurs across the ends of a shunt resistance which becomes larger than a detect voltage of the latching relay, and the latching relay is actuated in reverse to interrupt the power supply to the motor and the interrupted condition is maintained before the condition of an operating switch is changed thereafter.

The latching relay may have a coil connectable in series with the motor, the shunt resistance being connected in parallel with the coil, and a pair of relay contacts connected in series with the motor and energised to be actuated by the latching relay exclusively.

Preferably the relay contacts comprise a make contact connected to one pole of the motor and a break contact connected to other pole thereof.

The switching circuit may comprise co-operated operation switches connected in series with a pair of see -saw switches.

The control circuit may further comprise the latching relay and an NTC thermistor (positive temperature coefficient thermistor) connected in series with each other and a capacitor connected in parallel with the said series connection so as to delay and relax a surge current supplied to the motor when the operation switch is switched ON.

The circuit may comprise two diodes which are connected in parallel with each other with their respective forward directions of bias opposed so that one or other of them is in a forward bias connection without reference to a flow direction of the current, which are connected in series with the coil, and which are connected in parallel with the shunt resistance.

The control circuit may alternatively comprise a pair of Zener diodes connected in series with each other so that their respective forward directions of bias are opposed and are set through the latching relay, and the diode circuit and the shunt resistance are connected in parallel with each other.

There is a problem that when the motor and the coil are connected in series to supply an electric current, the driving current fluctuates in accordance with any irregular rotation of the motor or the like, and the wrong operation of the latching relay may result. To overcome this problem, a shunt resistance may be connected in parallel with the coil shunt resistance since the driving current is limited by an excess shunt resistance value.

A typical detect voltage for the relay circuit is 1 Volt and can not readily be set low by choice. In consideration of this, the shunt voltage is set to be lower than the detect voltage for a normal rotation of the motor and it is set to be higher than the latter when the motor rotation is locked. In a preferred embodiment, the detect voltage and the shunt resistance are adequately combined to be used, and it is preferable that the detect voltage is set to be under 5 Volts and more preferably, by 0.5 to 2 Volts. Further the shunt resistance is preferably set to be under 5 Ohms and it is most preferable to set it to be 0.5 to 2 Ohms.

The actuation of the motor is started by turning the switching circuit ON. However, an incorrect operation of the latching relay may be caused by a surge current injected for actuating the motor. To overcome this, a capacitor may be connected in parallel with the coil and the NTC thermistor may be connected in series with the coil. The surge current is absorbed by the capacitor described above to relax the build-up shunt voltage, and erroneous operation of the latching relay circuit is inhibited.

An NTC thermistor has a characteristic that the resistance value thereof is high (up to 10 Ohms) at a low temperature, while that value is rapidly decreased (under 1 Ohm) when the temperature rises by Joule heat or the like. Therefore the temperature of an NTC thermistor is low (the resistance value is high) just before switching the motor electrically ON, a high voltage drop is caused in the NTC thermistor, and the latching relay is not subjected to a higher voltage and can be inhibited from operation erroneously. Thereafter the resistance value drops as described hereinbefore. In the embodiment described above, the NTC thermistor and the capacitor are used together to inhibit the erroneous operation. However they can be used separately.

An example of a control device for an electrically powered hinged rearview mirror for a vehicle, in accordance with the present invention will now be described with reference to the accompanying drawings, in which Figure 1 is an electrical circuit diagram of circuitry in such a device; Figure 2A is a side view of a latching relay used in the circuitry of Figure 1; Figure 2B is a further view of the relay shown in Figure 2A, shown in a different condition; Figures 3 and 4 are respective circuit diagrams of modified latching relay circuits for the device; Figure 5 is a partial cut-away, partially axial sectional front view of a rearview mirror provided with the device; Figure 6 is an enlarged axial sectional front elevational view of a shaft assembly of the mirror shown in Figure 5;; Figure 7 is an enlarged perspective view from a rear side of an annular limit stop-plate used in the device; and Figure 8 is a projected view of the plate shown in Figure 7, a ball and the shaft root portion shown in Figure 7 at the limits of relative movement, in which Figure 8A shows the relative positioning of the parts when the mirror body is in its fully extended position and Figure 8(b) when it is in its retracted position.

As shown in Figure 1, a control device 1 for an electrically powered hinged rearview mirror comprises a power source E, a switching circuit 2, a control circuit 3, and a motor (control) circuit 4.

The switching circuit 2 includes two-contacts and two-circuit switches to which a pair of seesaw switches are connected in parallel so that the plus of the power source E is connected to a mirror extended side contact Al and a mirror retracted side contact B2 and the minus of the power source E is connected to contacts A2, B1 respectively. The switch can be changed and movable contact elements 5, 6 cooperate with each other to reverse the plus and minus voltages to common contacts COM1, COM2. The operable switch is mounted on an interior instrument panel or the like around the driver's seat to be operated by the driver.

The switching circuit 2 is not limited to a mechanical switch as shown in Figure 1: it is possible instead to have an electronic circuit disclosed in United States patents Nos 4,981,347 and 4,973,146 or United States Patent Application No. 08/159,439.

The control circuit 3 is provided between the switching circuit 2 and a motor M to pass or cut off an electric driving current of the motor M. In the circuit 3, an NTC thermistor, a latching relay RY which includes a coil RC and the motor M are connected in series on a line 7 connected to the movable contact element 5. Branch lines 10 and 11 are provided on the line 7 so that a shunt resistance R which is connected in parallel to the coil RC is disposed on the branch line 10 and a capacitor C is disposed on the branch line 11 so as to be connected in parallel with the latching relay RY and with the shunt resistance R. The capacitor C is provided for relaxing a surge current caused on the motor when the switch is put ON.On lines 7, 8 connected respectively to the movable contact elements 5, 6, a pair or relay contacts are provided and are operated to be actuated exclusively by the latching relay. The relay contacts are composed of a break contact ra connected with one pole N of the motor M and a make contact rb connected with the other pole B thereof.

Moreover branch lines 12, 13 are provided on lines 7, 8 respectively. A diode D1 is disposed on the line 12 to be connected in parallel with the break contact ra and a diode D2 is disposed on the line 13 to be connected in parallel with the make contact rb.

Normally the switching circuit 2 is contained in the instrument panel and the control circuit 3 and the motor M are assembled in the mirror body side (as described in accordance with Figure 5 hereinafter). However it is possible to assemble a unit of the switching circuit 2 and the control circuit 3 in the instrument panel inside the vehicle.

Latching Relay Composition.

The actuating condition of the normal relay is set to be self-held by a self contact thereof. However it returns to its original condition when the power source is OFF. By a magnetic latching mechanism, the latching relay does not return to its original condition immediately upon switching off of the power source, but rather has a degree of hysteresis so that its condition immediately before such a change in the connection of the power source is maintained for a while before an artificial return condition will be effected.

As shown in Figure 2A, in the latching relay RY, the coil RC is wound on a core 14, a permanent magnet 16 is attached to an end of a contact element 15 supported by a COM terminal (common terminal), and an NC terminal (normally closed terminal) and a NO terminal (normally open terminal) are provided within the rotational range of the contact element 15. The electric current value of the latching relay is determined by a magnetic force of the permanent magnet 16 and the core 14, while an actuation starting current corresponds to an actuation starting voltage owing to a constant coil resistance. In the ensuing description, this is called a detect voltage.

When the rearview mirror is turned from its extended position to its retracted position, the driver switches the switch to its ON position to supply electric current to the coil RC to turn the rearview mirror.

The electric current flows through the component parts of the circuitry in the following order : the power source e to coil RC NC terminal b COM terminal of the contact element 15 e the motor e the power source. The current provides a magnetic field in a direction which reduces the force with which the permanent magnet 16 is held by the core 14. However, the strength of this magnetic field is not sufficient to release the magnet 16.

Nonetheless, this current is sufficient for a normal rotation of the motor and the mirror is turned to its retracted position. Then a turning limit-stop means 70 (as shown in Figure 6) which is mounted for the extended condition does not function in regard to the turning of the mirror to its retracted position. Therefore the rearview mirror is turned towards its retracted position keeping the contact condition of the COM terminal with the NC terminal.

The turning of the rearview mirror is locked by the said locking mechanism which is mounted for the retracted position, and in accordance therewith a large locking current is supplied.

The magnetic field caused by the said locking current is sufficient to release the permanent magnet 16 so as to operate the latching relay and the permanent magnet is moved from the position it occupies in Figure 2A to the one in Figure 2B. Thus the permanent magnet is moved away from the upper end portion of the core to be held by the lower end portion. Therefore the contact condition of the COM terminal and the NC terminal is released and the current for the motor is interrupted to stop the rearview mirror turning any further. To turn the mirror from its retracted position to its extended condition, the steps just described are carried out in reverse order.

To assemble the contact element 15 in the control circuit 3 of Figure 1, as described above, it comprises a pair of relay contacts which are exclusively actuated in relation to each other, that is the break contact ra connected with one pole N of the motor M and the make contact rb connected with the other pole B.

Modified Latching Relay Circuit.

In the embodiment just described, a shunt resistance R is connected in parallel with the coil RC. It is further possible to construct the circuitry as shown in Figure 3 and Figure 4. In Figure 3 diodes D3 and D4 are connected in parallel with one another, and each.in series with the coil RC with their bias directions opposed, so that the diodes D3 and D4 can supplement the bias direction respectively so as to supply any direct current. To supply a forward direct current, it is necessary to apply voltage which is over a built-in-potential on the PN junction.

This voltage is about 0.6 Volts (in the case of a silicon semi-conductor) and if the voltage is under that value, erroneous operation caused by a surge voltage or a noise or the like can be inhibited. As shown in Figure 4, Zener Diodes D5 and D6 are series connected at the two ends of the coil RC respectively in a manner that their bias directions are opposed. If the shunt voltage is increased to apply a large voltage to the Zener Diodes D5 and D6, one of the Zener Diodes D5 or D6 is prior actuated, and thereafter the other diode is actuated. Therefore one or other of the Zener diodes D5 and D6 is in a Zener breakdown condition for a large voltage normally, and erroneous operation caused by the surge voltage is inhibited.

Operation of the control device will now be described.

Figure 1 indicates the control device for the electrically powered hinged rearview mirror in a condition ready for turning the mirror to its retracted position.

This mirror can also be in any intermediate position (a refuge position) between its retracted position and its extended position. It can also be in a forward refuge position, in which it is turned inwardly and forwardly in the direction of travel of the vehicle. The mirror can be placed in an intermediate position or a forward refuge position by an external force. Hereinafter, when the mirror body is turned from its retracted position, to its extended position, the mirror rotation is called an extending rotation, while when the mirror body is turned from its extended position to its retracted position, the motor rotation is called a retracting rotation.

(1) The rearview mirror is in the extended position: As shown in Figure 1, in the control circuit 3, the break contact ra is ON and the make contact rb is OFF. The switching circuit 2 is switched ON to the retracted position side contacts Al, A2 to apply the plus voltage to the COM1 terminal and the minus voltage to the COM 2 terminal, the electric current passing through the NTC thermistor is supplied to the parallel circuits 10, 11 of the shunt resistance R and the coil RC, the relay contact ra, the motor M and diode D2 so as to rotate the motor M.

The mirror body is turned to the retracted position by the retracting rotation of the motor until it reaches the retracted position. Thereafter, the turning is mechanically stopped by the limit-stop means 70 as shown in Figure 6. This increases the motor electric current (this is called the lock current). As a result the shunt voltage across the shunt resistance R is above the determined value (the detect voltage of the latching relay). The latching relay RY is therefore actuated as shown by Figure 2B to turn the break contact ra OFF and to turn the make contact rb ON.

In this embodiment, the parameters are so set that the latching relay RY actuates when the voltage becomes 2 Volts with a 2 Ohms shunt resistance and a 1 amp lock current.

If in the condition as shown in Figure 1, the switching circuit 2 is switched ON to the extended position side contacts B1, B2 to apply the plus voltage to the COM2 terminal, the motor M can not rotate owing to the reverse bias connection of the diode D2 since the make contact rb is in the OFF condition. Therefore if the driver operates improperly, the rearview mirror is not turned.

(2) The rearview mirror is in the retracted position.

The latching relay RY is held in the condition shown in Figure 2B, and in the control circuit 3, the break contact ra is ON and the break contact rb is OFF. The control switch 2 is switched ON to the extended position side contacts B1, B2 to apply the plus voltage to the COM terminal 2 and to apply the minus voltage to the COM terminal 1. The motor current passes to the COM terminal 1 through the relay contact rb, the motor M, diode D1, the coil RC and the shunt resistance R. Thereby the motor M is rotated to turn the mirror body towards its extended position. When the mirror body reaches its extended position, the turning of the mirror is mechanically stopped to supply the lock current so as to actuate the latching relay RY instantly to result in the condition shown in Figure 2A.

In the condition of the circuit with the mirror body in its retracted position, operation of the switch 2 to switch ON the retracted position side contacts Al, A2 to apply the plus voltage to the COM terminal 1 will not cause rotation of the motor owing to the reverse bias connection of the diodes D1, since the break contact ra is OFF.

(3) The rearview mirror is in the forward refuge position.

The mirror body may have been substantially in the retracted position or the extended position, but owing to an obstruction or the like, it may be moved out of position into a forward refuge position. When the mirror body is moved from its extended position to a refuge position, the control circuit 3 is in a condition as shown in Figure 1. Therefore when the operable switch 2 is switched to its ON position for the retracted position side contacts Al, A2 to rotate the motor M and thus to turn the mirror to the retracted position, the mirror is stopped in its retracted position. However, if the switch 2 is switched to its ON position for the extended position side contacts B1, B2, as described already, the motor M can not rotate owing to the reverse bias connection of the diode D2.

Also, when the mirror body is moved out from its retracted position to a forward refuge position in the control circuit 3, the break contact ra is OFF and the make contact rb is ON and the mirror will not turn to its retract position by moving the switch 2 to its corresponding position. However, once the switch 2 is switched to its position for moving the mirror body to its extended position, by establishing contact with the extended position side contacts B1, B2, the mirror is stopped at its extended position and the circuit is changed to the condition shown in Figure 1. Thereafter, when the switch is operated to contact the retracted position side contacts Al, A2, the mirror is turned to the retracted position.

(4) The mirror body is positioned between the retracted position and the extended position.

When the mirror body is moved to such a refuge position from the retracted position the control circuit 3 is in a condition in which the break contact ra is OFF and the make contact rb is ON, and the operable switch 2 is first switched ON for the extended position side contacts B1, B2 to return the mirror body to the extended position. When the mirror body is moved out from the extended position towards the retracted position, the control circuit 3 is left in the condition shown in Figure 1. Therefore the operable switch 2 is first switched ON for the retracted position side contacts Al, A2 to return the mirror body to the retracted position.

The relationship between the circuit condition, the mirror body position and the mirror actuation is described in the following table.

Relationship between the Circuit Condition, the Mirror Body Position, the Switch Actuation and the Consequent Mirror Movement.

circuit mirror body switch mirror condition position actuation movement ready for forward to extend none turnlng refuge the to retract to the mirror retracted body to position the ready for retracted turning to position the extended to retract to the retracted position ready for turnlng to the extended position retracted to extend none to retract none but circuit condition changed to one ready for turning the mirror body extended position ready for forward to extend toth turning refuge extended the mirror position, body to ready for the turning to position position to retract none extended to extend none, but circuit condition changed to one ready for turning mirror retracted position to retract none intermediate to extend to the extended position ready for turning to the refracted position to retract none retracted to extend to the extended posltlon to retract none In the actuation already described, when the mirror body reaches its retracted position or its extended position turning of the mirror body is mechanically stopped and a large driving current is simultaneously supplied to the motor M. As a result the latching relay RY is instantly actuated to interrupt the electric power supply to the motor M. When the motor M is driven normally and the mirror body is turned to its retracted position or its extended position, erroneous operation is so inhibited that the latching relay RY is not actuated by passing a driving current (a normal actuating current) and the normal driving current is partially shunted by the shunt resistance R.

The control circuit 3 has substantially no time lag and is actuated rapidly. When the driving current for turning the mirror body is interrupted, for example, in the case of an emergency, such as when a human arm or a finger are accidentally positioned in the mirror whilst the mirror body is being turned, further turning of the mirror body is stopped to interrupt the driving force instantly, and there is little risk of serious injury to arms or fingers.

The starting of the motor M is performed by switching the operable switch 2 to an ON position. There is then a risk of an erroneous operation owing to the latching relay RY and the flow of a surge current.

Therefore as already described, capacitor and the NTC thermistor are connected to relax the surge current.

Now the rearview mirror assembly including the foregoing control device will be described.

As shown in Figure 5, in an electrically powered hinged rearview mirror assembly 20, a frame 26 is assembled on a cylindrical shaft 23 extending upwardly from an extension 22 of a base 21 to support a mirror body 25 so that it can be turned to an extended and a retracted position. The frame 26 has a root portion 27 provided with a sleeve 28 to receive the shaft therethrough and a wing portion 29 which extends almost vertically from the root portion 27. The wing portion 29 is fixed on the inner wall of the mirror body 25 by a screw 19 and an actuator unit (not shown) is attached on the front surface of the wing portion so as to adjust the mirror reflecting angle.

The electric driving means in the form of a motor 30 and a speed reduction mechanism 33 are mounted on the root portion 27 of the frame 26 and a gear 40 is mounted around the shaft 23 in a manner having a clutch function so that it is coupled to the shaft for normal use (the mirror body is in its extended position) and is free to move relative to the shaft when acted upon by an undesirable turning force. The last step gear of the speed reduction mechanism 33 engages the gear 40 to turn or to forcible rotate the mirror body electrically. The upper surface of a shaft flange 24 and the frame root portion 27 are constructed and arranged to have surfaces in contact with each other and limit-stop means 70 comprise a projection 71 which is mounted on the shaft flange portion 24 and an arcshaped groove 72 which is formed on an underside of the root portion 27 to receive the projection 71.An upright wall 53 is mounted on the root portion 27 of the frame 26 around the shaft and a gear box 52 is provided by stacking an upper plate 54 on the wall 53 as shown in Figure 5 and Figure 6.

The speed reduction mechanism 33 includes a first step and a second step speed reduction gear 34 and 37 and an end gear 39. The first step speed reduction gear 34 as shown by broken lines includes a worm wheel to engage a worm pinion 32 which is fixed on a motor axis 31 and a worm to engage a worm wheel of the second step speed reduction gear 37. The second step speed reduction gear 37 includes a worm wheel to engage the worm of the first step speed reduction gear 34 and a plane gear to engage the end gear 39. The end gear 39 engages a gear 40 which is provided with a ball clutch and releasably engages the shaft 23.

On an upper portion of the gear 40 which is supported by the shaft 23, there are provided steel balls 42, a ball guide 43 provided with a flange portion 44, a sleeve 46, a lower washer 47, a coil spring 48, an upper washer 49 and a fastener 50 in such a manner that the steel balls 42 are always elastically in contact with the upper surface of the gear 40 (as shown in Figure 5 and Figure 6).

The steel balls 42 are engaged in respective concave portions 41 formed on the upper surface of the gear 40 and respective upper halves of the steel balls 42 are loosely inserted in small holes 45 which are formed on the flange portion 44 of the ball guide 43 mounted on the shaft 23 in a rotationally locking manner. In Figure 5, numeral 55 indicates a harness line which extends through the hollow portion of the shaft to drive and control the motor. A unit 80 of the control circuit is mounted on an upper plate 54 of the frame.

In the control device, the motor 30 is actuated to rotate the end gear 39 of the speed reduction mechanism 33 and the gear 40 is in a fixed condition relative to the shaft 23 by the clutch mechanism constituted by the steel balls 42 and the concave portions 41. The whole of the frame is rotated, centred around the shaft 23 so as to turn the mirror body 25 to the retracted position or the extended position. The speed reduction mechanism 33 is not limited to the illustrated mechanism, and can alternatively be constructed as a speed reduction mechanism comprising a plane gear train (not shown) which is disclosed in United States Patent Application No. 08/042154 of Toshihiro Mochizuki.

At the bottom portion of the frame root portion 27, there are, concentric with the shaft 23, annular groove 63 to contain a plate limit-stop element 65 for positioning the mirror body 25, a ring-shaped sliding portion 75, an annular groove 77 to engage a shaft rib 76 and an arcshaped groove 72 to be part of the limit-stop means as shown in Figure 6. Corresponding to the above, semispherical concave portions 61 to support steel balls 62, a contact surface (sliding surface) 73 opposite to the sliding portions 75 and a convex portion 71 engaging the annular shaft rib 76 and accommodated in the arc-shaped groove 72, are disposed on the shaft flange portion 24.

As shown in Figure 7, which is a perspective view from the rear side of the limit-stop element 65, two recessed portions 66 having shoulders 67, 68 are symmetrically disposed to form surfaces H and L. Steel balls 62 are respectively supported by semi-spherical concave portions 61 and are inserted in the recessed portions 66. Positioning means composed of the limit-stop element 65 and steel balls 62 are double protected by a first barrier constituted by the shaft rib 76 and the annular groove 77 and a second barrier constituted by the ring shape sliding portion 75. Position means are also protected from water ingress, dust or foreign contamination and the rotation and moving ability of the steel balls can be maintained. Therefore, accurate and constant turning and stopping of the mirror body can be achieved.

Figure 8 is a partially cut-away projected view of the annular-shaped plate limit-stop element 65 and an abutment of the steel balls 62 and the plate limit-stop element 65 is shown . Figure 8A shows the condition of the mirror body in its extended position and Figure 8B shows the mirror body in its retracted position. Gaps G1 and G2 respectively are formed between the top of the steel ball and the plate limit-stop element 65 to protect surfaces H and L from abrasion.

When the mirror body is turned from its extended position to its retracted position, the motor 30 is actuated to rotate the end gear 39 of the speed reduction mechanism and the gear 40 which engages the said gear 39 starts to rotate, while as described hereinbefore, the gear 40 is already coupled to the shaft by the ball clutch, and as a result the frame 26 is rotated. By the rotation of the frame 26, the steel balls 42 which are loosely guided in the small hole 45 are set for rotation from the concave portion 41 of the gear 40 to the gear surface to press a coil spring 47 in the direction shown by the arrow.

When the mirror body is turned to its extended position, the shoulder 67 of the plate limit-stop element 65 which constitute positioning means for the extended position contacts with the ball 62 (Figure 8A) and the motor rotation is mechanically stopped. By the stopping of the motor rotation, the power source supply to the motor is cut off by the control device owing to the increased electric driving current as described hereinbefore.

Furthermore when the mirror is turned to its retracted position, the convex portion 71 which constitutes a turning limit-stop for the retracted position of the mirror body contacts the end portion of the arc-shaped groove 72 to stop the rotation of the shaft of the motor 30 mechanically, and the electric power source supply is cut off by an operation of the control device.

When the mirror body is forced to turn from the controlled position by an external force, the steel balls 62 are set for rotation from the shoulder 67 and the surface H of the plate limit-stop element 65 is slid, and the frame is moved slightly upwardly from the shaft flange portion 24. Then the driver may connect either the switch contacts Al and A2 or B1 and B2 to rotate the mirror body to the correct position.

The shaft rib 76 protrudes from the base of the shaft 23 in a convex annular shape to engage the annular groove 77 of the frame, and the positioning means 60 can be protected from contaminants such as water, dust or the like to inhibit an irregular rotation of the frame 26 that may be caused by such contamination.

As described above, in the control device for the electric powered hinged rearview mirror, the latching relay is used for the position control device of the rearview mirror, and a small number of parts assembled in the control device can achieve a simple, compact and inexpensive construction for the position control device.

Moreover it is possible to mount the control device on a vehicle interior side to achieve a light-weight electrically powered hinged rearview mirror. Further the rearview mirror can be stopped simultaneously with the stopping of the motor rotation, and the stop positioning accuracy of the mirror is improved to achieve greater reliability. There is substantially no time lag for an emergency so that driving safety is improved. The device comprises a small number of assemblies and the circuit is simple and compact so that assembly of the control circuit on the mirror body side is possible.

Claims (14)

Claims:

1. A control device for an electrically powered hinged rearview mirror for a vehicle comprising a shaft extending upwardly from a base; a mirror body having a motor; turning limit-stop means mounted around the shaft; the mirror body being turned around the shaft by a normal and a reverse rotation of the motor, the turning being stopped at an extended position and a retracted position of the mirror body by the turning limit-stop means; in which the control device further comprises a switching circuit for changing the electrical polarity of a voltage applied to the motor so as to turn the mirror body to the extended position or the retracted position, and a control circuit which has a latching relay and a shunt resistance for interrupting a driving current to the motor when the mirror body reaches the extended position and the retracted position and the motor is locked against rotation by the turning limit-stop means, and in which in the control circuit, the motor is locked when the mirror body reaches the extended position and the retracted position, a voltage occurs across the ends of a shunt resistance which becomes larger than a detect voltage of the latching relay, and the latching relay is actuated in reverse to interrupt the power supply to the motor and the interrupted condition is maintained before the condition of an operating switch is changed thereafter.

2. A control device cording to claim 1, in which the latching relay has a coil connectable in series with the motor, the shunt resistance being connected in parallel with the coil, and a pair of relay contacts connected in series with the motor and energised to be actuated by the latching relay exclusively.

3. A control device according to claim 2, in which the relay contacts comprise a make contact connected to one pole of the motor and a break contact connected to other pole thereof.

4. A control device according to any preceding claim, in which the switching circuit comprises co-operated operation switches connected in series with a pair of seesaw switches.

5. A control device according to any preceding claim, in which the resistance value of the shunt resistance is less than 5 ohms.

6. A control device according to claim 5, in which the resistance value of the shunt resistance is substantially in the range from 0.5 ohms to 2 ohms.

7. A control device according to any preceding claim, in which the detect voltage of the latching relay is less than 5 Volts.

8. A control device according to claim 7, in which the detect voltage is substantially in the range from 0.5 volts to 2 volts.

9. A control device according to any preceding claim, in which the control circuit comprises the latching relay and an NTC thermistor (positive temperature coefficient thermistor) connected in series with each other and a capacitor connected in parallel with the said series connection so as to delay and relax a surge current supplied to the motor when the operation switch is switched ON.

10. A control device according to any preceding claim, in which the control circuit comprises two diodes which are connected in parallel with each other with their respective forward directions of bias opposed so that one or other of them is in a forward bias connection without reference to a flow direction of the current, which are connected in series with the coil, and which are connected in parallel with the shunt resistance.

11. A control device according to any one of claims 1 to 9, in which the control circuit comprises a pair of Zener diodes connected in series with each other so that their respective forward directions of bias are opposed and are set through the latching relay, and the diode circuit and the shunt resistance are connected in parallel with each other.

12. An electrically powered hinged rearview mirror comprising a base; a shaft extending upwardly from the base and having a flange portion; a mirror body mounted so that it can be turned around the shaft; a frame mounted in the mirror body and having a root portion formed with a hole through which the shaft extends and a wing portion to support a mirror element; electric driving means and a speed reduction gear mechanism which are fixed on the frame root portion for turning the mirror body; a gear box mounted on the frame root portion to surround the shaft and the speed reduction gear mechanism; a clutch gear which engages the shaft to engage an end gear of the speed reduction gear mechanism; turning limit-stop means for the mirror body provided between the flange upper surface of the shaft and the frame root portion.

an upright wall mounted on the frame root portion to form the bottom portion of the gear box; an outer plate engaging an upper portion of the gear box to support the upper end of the shaft; and a control circuit unit assembled on the outer plate.

13. A control device according to claim 1 and substantially as described herein with reference to an as illustrated in the accompanying drawings, with or without one of the modifications shown in Figures 3 and 4.

14. An electrically powered hinged rearview mirror substantially as described herein with reference to and as illustrated in the accompanying drawings.