GB2191748A - A rear view mirror for a motor vehicle - Google Patents

Abstract

The rear view mirror comprises a housing 4, a self-adhesive pad 6 on the housing for enabling the rear view mirror to be mounted in position, a mirror glass 8 which has a front face 10, a front plate 12 which is made of a transparent material and which is mounted between the front face of the mirror glass and an open face 14 of the housing, and a solenoid 32,34,36 16 for causing the mirror glass to pivot between normal and anti-glare positions. The mirror glass is provided with a partially light reflective coating which is such as to allow from five to twenty per cent, e.g. nine per cent, of light falling on the mirror glass to pass through the mirror glass, and a photo sensor 18 positioned inside the housing energises the solenoid when a predetermined light intensity is sensed. <IMAGE>

Description

SPECIFICATION A rear view mirror for a motorvehicle This invention relates to a rearview mirrorfor a motor vehicle.

Accordingly, this invention provides a rear view mirrorfor a motor vehicle, which rear view mirror comprises a housing, mounting means on the housing for enabling the rear view mirror to be mounted in position, a mirror glass which has a front face, a front plate which is made of atransparent material and which is mounted between the front face of the mirror glass and an open face ofthe housing, and automatically operable pivot means for causing the mirror glass to pivot between a normal viewing position in which it lies adjacent the front plate to an anti-glare viewing position in which it is tilted with respectto the front plate in dependence upon the presence or absence of light of a predetermined intensity from a following motor vehicle, the mirror glass being provided with a partially light reflective coating which is such asto allow from five to twenty per cent of light falling on the mirror glass to pass through the mirror glass, and the automatically operable pivot means including a photo sensor which is positioned inside the housing and which is for sensing the presence or absence of lightofa predetermined intensity which has passed through the mirror glass wherebythe automatically operable pivot means operates to pivot the mirror glass between its normal viewing position and its anti-glare viewing position consequent upon the intensity of light passing through the mirror glass and being sensed bythe photo sensor.

Hitherto, some rearview mirrors for motor vehicles have been such thatthe mirror glass has had to be provided with an aperture through which the photo sensor faces, in order that the photo sensor can receive the light from a following motor vehicle. Because the photo sensor looks through the aperture, it can often only receive lightfrom a relatively narrow angle, for example of 35". By providing the mirror glass with the partially light reflective coating, the photo sensor as used in the rear view mirror of the present invention may be able to receive light from relatively very wide angles, for example of 150 to 2000. In addition to being able to sense light from wide angles, it will be apparentthat there is no need to provide a hole in the mirror glass which obviously saves on a manufacturing operation. Thus the rear view mirror of the present invention can be relatively cheap and easy to produce and assemble. Sealing the mirror against the ingress of moisture can also be facilitated by avoiding the need to provide a hole through the mirrorglassforthe photo sensor.

The photo sensor may be provided in the middle of the rear view mirror so that it works equally well for right and left and driving.

The rear view mirror of the present invention lends itself to being preset so thatthere is no need to provide adjustment potentiometer means such for example as an external thumb wheel, foradjusting the sensitivity of the rearview mirror. The rearview mirror can be arranged to operate at a preset value and the construction of the rearview mirror is such that it is not so sensitive and does not require so much variation in operating perameters as some known rearviewmirrors.

The rearview mirror ofthe present invention can thus be very cost effective to produce. Thefront plate may be effective to help seal the inside ofthe housing and so help prevent the ingress of moisture, which moisture may adversely affect parts insidethe housing, such for example as the miorror glass. The elimination of the wedge of glass that is often used in known mirrors is believed to be a cause of the good image definition that is achievable by the rear view mirrorofthe present invention.

The mirror glass will usually pivot about its lower edge. In this edge, the mirror glass and the front plate may both fit in a groove formed in a lower portion ofthe housing. Alternatively, the mirror glass may pivot about a centre portion ofthe mirror glass.

In its anti-glare viewing position, the mirror glass preferably makes an angle of seven degrees with the front plate.

The pivot means may be an electro magnetic device ora motor unit.

The photo sensor is preferably a photo diode.

The rear view mirror preferably includes ambient light compensation means for compensating forthe affect of ambient light and so helping to prevent premature pivoting of the mirrorglassto its anti-glare position in bright ambient lig htconditions.

The ambient light compensation means may include a photo sensor, for example a photo diode.

The photo sensor which is for sensing the presence or absence of light of a predetermined intensity which has passed through the mirror and the photo sensor of the ambient light compensation means may be arranged in a bridge circuit.

The photo sensor of the ambient light compensation means may also be positioned inside the housing and it is not necessary to provide the mirror glass with an aperture through which the photo sensor of the ambient light compensation means faces. The photo sensor of the ambient light compensation means may be able to sense the ambient light through the mirror glass and this obviously facilitates ease of manufacture and assembly of the rear view mirror. If desired, the photo sensor of the ambient light compensation means may face through a bottom wall ofthe housing.

The rearview mirror may include separator means for separating the mirror glass and the front plate when the mirror glass is in its normal viewing position.

The separator means may be a pad, for example a pad of a resilient material.

The housing may be a single moulded item or it may be made in several parts. The housing is preferably made from a plastics material but other materials such for example as metals may be employed.

The mounting means may be a ball and socket joint The ball and socket joint may be provided with a tightening nut for securing the ball and socket joint in the desired position. Other mounting means such for example as adhesive pads may be employed.

Generaliy, it will be appreciated that the type of mounting means employed will depend upon where the mirror is to be located, for example inside or outsidethemotorvehicle, oron awindscreen or bulkhead portion ofthe motor vehicle.

The mirror glass may be plain mirror glass having for example a silvered light reflective coating.

Preferably, the light reflective coating is such as to allow approximately 9% of light falling on the mirror glass to pass through the mirror glass.

The mirror coating may advantageously be an aluminium coating, a stainless steel coating or a copper alloy coating. Other materials may be employedforthe mirror coating.

The rearview mirror may include circuit means and switch means for enabling the pivoting ofthe mirror glass, the circuit means being such as to prevent operation ofthe switch means until a first circuit including the photo sensorwhich is for sensing the presence or absence of lightofa predetermined level that has passed through the housing, and a second circuit including the photo sensorforsensing ambient light conditions, are both in a condition requiring the mirror glass to pivot.

The mirror glass may be biased to its non-pivoted condition. Thus, for example, the mirror glass may be spring biased to its non-pivoted condition.

Where the pivot means for pivoting the mirror glass to its anti-glare position is an electro magnetic device, then the electro magnetic device is preferably provided with a pair of poles that are relatively far apart. Such an arrangement may enable the magnetic force capability of the electro magneitc arrangementto be increased by up to 40%, compared with known arrangements.

The electro magnetic device may be provided with associated electrical circuitry such that more current is provided for actual pivoting of the mirror glass than is provided just to maintain the rear mirror in an operable condition and also justto hold the pivoted mirror glass in its pivoted position.Thus,for example, the associated electrical circuitry may include a hold on circuit that can operate it, for example, sixvolts so that a 600 milliamp milliamp solenoid may be used for example, whilstthefacility may be provided for stepping up the currentto twelve volts for effecting the pivoting of the mirror glass.Afterthe pivoting ofthe mirror glass, the circuitry can be such as to drop the current required back down to the original level ofsixvolts. Such stepping up and down ofthe current requirements of the rearview mirror are effective to minimise on heat dissipated by the electrical circuitry.

The rearview mirror may include a second solenoid to drive a relay to let in the higher current required of, for example, twelve volts. Directly a first solenoid seesthe higher currentfor effecting the pivoting ofthe mirror, then a second relay may be effective to pull the circuit back to its lower current operating condition.

The front plate is preferably made of a plastics material. Any acrylic plastics material is presently preferred. The front plate may also be made of glass if desired.

Advantageously, the front plate is provided with a darkened appearance. The darkened appearance may be achieved by using a smoked front plate, for example a smoked acrylic plastics material front plate. The front plate need not be darkened and it can be clear if desired.

In an alternative embodiment of the invention, the rear view mirror is provided with an electro magnetic device operable such as positivelyto drivethemirror glass from its normal viewing position to its anti-glare position, and also from its anti-glare position to its day time normal viewing position.

The electro magnetic device may include polarity reversing means for reversing polarity of a main solenoid such that the main solenoid attracts the mirrorglassto one position and repelsthe mirror glass to the other position. Preferably, the electro magnetic device attracts the mirror glass to its anti-glare position, and repels the mirror glass to its normal viewing position. Such an arrangement reduces the amount of operational current required.

The electro magnetic device may comprise a main solenoid for attracting and repelling the mirror glass, and a relay for driving the main solenoid and reversing the polarity of the solenoid. The relay may comprise a varistor connected across an auxiliary solenoid.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure lisa front perspective view of a rearview mirror for a vehicle, the rear view mirror being shown in a partially exploded condition; Figure2 is a cross section through the rear view mirror shown in Figure 1; and Figures 3 and 4 show two alternative circuits for the rearview mirror shown in Figures 1 and 2.

Referring to Figures 1 and 2, there is shown a rear view mirror 2 for a motorvehicle (not shown). The rearview mirror2 comprises a housing 4and mounting means in the form of a self-adhesive pad 6 forenablingthe rearview mirror2to be mounted in position on the inside of a vehicle windscreen (not shown) or on a vehicle bulkhead (not shown).

The rear view mirror 2 is provided with a mirrror glass 8 which has a front face 10. The rear view mirrror 2 is also provided with a front plate 12which is mounted between the front face 10 of the mirror glass 8 and an open face 14 ofthe housing 4.

The rearview mirror 2 is further provided with automatically operable pivot means 16 for causing the mirror glass 8 to pivot between a daytime normal viewing position in which the mirror glass 8 lies adjacentthe front plate 12 (as shown in dotted lines in Figure 2) and a nighttime anti-glare viewing position in which the mirror glass 8 is tilted with respect to thefront plate 12 (as shown in full lines in Figure 2). The pivot means 16 causes the pivoting in dependence upon the presence or absence of light of a predetermined intensity from following motor vehicle (not shown).

The mirror glass 8 is provided with a partially light reflective coating which is such asto allow from five to twenty per cent of light falling on the mirror glass 8 to passthroughthe mirrorglass8.

The pivot means includes a photo sensor 18 which is positioned inside the housing as shown and which is for sensing the presence or absence of light of a predetermined intensitywhich is passed through the mirror glass. The rear view mirror 2 is such thatthe pivot means 16 operates to pivot the mirror glass 8 between its daytime normal viewing position and its nighttime anti-glare viewing position consequent upon the intensity of light passing through the mirror glass 8 being sensed by the photo sensor 18.

The rear view mirror 2 is provided with ambient light compensating means for compensating forthe affect of ambient light on the rear view mirrror 2. The ambient light compensating means includes an ambientsetting photo sensor 20. Asshown,the photo sensor 20 is also positioned inside the housing 4 and itfaces through the mirror glass 8. If desired, the photo sensor 20 could face downwardly through an aperture (not shown) in a bottom wall 22 ofthe housing 4.

The pad 6 is connected to a mounting lug 24 on the rear of the housing 4 by means of a ball and socket type joint 26. The joint 26may be of a preset strength or it may be adjustable by means of a locking nut.

The joint 26 enables the housing 4to be tiled with respectto the pad 6 for the convenience of a driver of the motor vehicle.

The rear view mirror 2 is such that the mirror glass 8 is pivotable about its lower edge 28. The lower edge 28 may fit in a groove 30 in the bottom wall 2 of the housing 4.

The pivot means 16 comprises a solenoid coil 32 which is relatively long so that magnetically energised plates 34,36 are spaced relatively far apart from each other and this gives a high degree of electro magnetism. The plates 34,36 attract complementary steel plates 38,40 respectively secured, for example by an adhesive, to the rearface 42 ofthe mirrorglass8.

When the coil 32 is de-energised, a return spring 44 is effective to pivot the mirror from its pivoted night time anti-glarn viewing position as shown in full lines in Figure 2 to its non-pivoted day time viewing position as shown in dotted lines in Figure 2.

The circuitforthe rearview mirror 2 is mounted on a printed circuit board 46 as shown in Figure 1.

Figure 3 shows a circu it 48 for the rear view mirror.

As shown, the photo sensor 20 is connected to an ambient light trigger switch 50 and the trigger switch 50 is itself connected to an ambient light level adjustment potentiometer 52. Similarly, the photo sensor 18 is connected to a trigger switch 54 and the trigger switch 54 is itself connected to an adjustment potentiometer 56. Signals from both of the trigger switches 50,54 go to an AND gate 58. Signals from the gate 58 are passed to a timer 60. The timer 60 is linked to a holding chopper device 62, a solenoid driver device 64 and the solenoid coil 32.

The potentiometers 52,56 are able to give sensitivity control. The gate 58 is such that both of the trigger switches 50,54 must be triggered before any signals pass through the gate 58. The timer 60 is such that it may be on full power for approximately one second in order to achieve positive and fast pivoting of the mirror glass 8 to its pivoted position as shown in full lines in Figure 2. The timer 16 is then effective to bring in the holding chopper device 62 which keeps the mirror glass 8 in its pivoted position but not on the full pivoting current and only on a reduced holding current. This reduces the amount of current consumed by the circuit 48 and thus minimises on heat generated. The solenoid driver device 64 is effectively the outward stage ofthe circuit which drives the solenoid coil 32.When the rearviewmirror2 is no longer subject to lightfrom a following vehicle ofthe predetermined density, then the gate 58 switches off, the solenoid coil 32 becomes de-energised and the return spring 44 is able to pivot the mirror glass 8 backto its non-pivoted condition as shown in dotted lines in Figure 2.

Referring now to Figure 4, there is shown a circuit 70 comprising a photo sensor 72 which is positioned inside the housing 4 and which is for sensing the presence or absence of light of a predetermined insensity which has passed through the mirror glass 8. The circuit 70 also includes a photo sensor 74 which is also positioned inside the housing 4and which forms ambient light compensating means.

The photo sensors 72,74 are connected via line 76 to a 741 device. The 741 device is connected to a variable resistance 78 via line 80. The variable resistance 78 is connected in series with a resistance 82 as shown. The circuit 70 also includes a diode 84, a capacitor 86, a resistance 88, a transistor 90 and a relay 92. The relay 92 comprises a resistance 94 and a diode 96 connected across the resistance 94 as shown. Also included across the circuit is a protection diode 98.

The circuit 70 includes a relay 100. The relay 100 comprises an auxiliary solenoid 102 and a varistor 104. The solenoid 102 is provided with relay contacts 106, 108. The varistor 104 acts like a diode but aborts back emf from the winding of the solenoid 102 in both directions when the polarity of the auxiliary solenoid 102 is changed. The solenoid 102 in effect forms a miniature relay which is effective to drive a main drive solenoid (not shown) on a printed circuit board (not shown) in the mirror housing 4.The mirrorglass (not shown) will normally be in its day time normal viewing position and, when the photo sensor 72 sees a change in light conditions due to the headlights of a following vehicle at night,the polarity ofthe solenoid 102 is changed and the main solenoid is effective to repel the mirror glass to the nighttime anti-glare position. With such an arrangement, it is not necessaryto hold the mirror glass in the normal viewing position and not much operational current is employed during use ofthe mirror. A spring or springs such for example as the return spring 44, can beemployedto assist in repelling the mirrorfrom its nighttime anti-glare position to its daytime normal viewing position and for holding the mirror in its day time normal viewing position.

The rear surface of the mirror glass (not shown) is provided with magnetic material such for example as the plates 34,36 shown in our earlier patent application. Advantageously, these plates 38,40 are replaced with a single plate or with two separate plates which are made from Bisbell magnetic material. Such material can be made very thin which helps produce the mirror in a compactform.

Where a spring or springs are employed, these can be strongerspringsthan usual and this again facilitates a very quick reaction time between pivoting the mirrorfrom one position to another position.

The varistor 104 will usually be mounted on the outside ofthe relay 100.

It isto be appreciatedthatthe embodiments ofthe invention described above with reference to the drawings have been given byway of example only and that modifications may be effected. Thus, for example, the shape ofthe housing 4 may be varied and differenttypes of mounting means otherthan the pad 6 may be employed.

One or more pieces of magnetic material may be employed for the plates 34,36. A presently preferred magnetic materiai is that available from Bisbel Magnetic Products Limited of Burton-on-Trent, England. This magnetic material is available in very thin pieces which facilitate the formation of a compact rearview mirror. The rearview mirror may also include memory means for enabling the mirror to be angled at two or more different standard positions so that, for example, the mirror may easily be adjusted by a husband orwife who may be driving the same vehicle and who may require the mirrorto be at differenttilt angles due to the husband and wife being of different heights. As often occurs, where one or more children also may be driving a vehicle, then other normal viewing angles may need to be provided in the memory means. the memory means may be arranged to control mover means for automatically moving the mirror to a predetermined position on actuation of appropriate switch means.

Claims (26)

1. A mar view mirror for a motorvehicle, which rear view mirror comprises a housing, mounting means on the housing for enabling the rearview mirror to be mounted in position, a mirror glass which has a front face, a front plate which is made of a transparent material and which is mounted between the front face of the mirror glass and an open face ofthe housing, and automatically operable pivot means for causing the mirrorto pivot between a normal viewing position in which it lies adjacentthefront plate to an anti-glare viewing position in which it is tilted with respect to the front plate in dependence upon the presence or absence of light of a predetermined intensity from a following motor vehicle, the mirror glass being provided with a partially light reflective coating which is such as to allowfrom five to twenty per cent of light falling on the mirror glass to pass through the mirror glass, and the automatically operable pivot means including a photo sensor which is positioned inside the housing and which isforsensing the presence of absence of light of a predetermined intensity which has passed through the mirrorglasswherebythe automatically operable pivot means operates to pivot the mirror or glass between its normal viewing position and its anti-glare viewing position consequent upon the intensity of light passing through the mirror glass and being sensed bythe photo sensor.

2. Arearviewmirror according to claim 1 in which the photo sensor is provided in the middle of the rear view mirror so that it works equally well for right and left hand driving.

3. A rear view mirror according to claim 1 or claim 2 in which the mirror glass pivots about its lower edge.

4. A rear view mirror according to any one ofthe preceding claims in which, in its anti-glare viewing position, the mirror glass makes an angle of seven degrees with the front plate.

5. A rear view mirror according to any one ofthe preceding claims in which the plate sensor is a photo diode.

6. A rear view mirror according to any one ofthe preceding claims and including ambient light compensation means for compensating for the affect of ambient light and so helping to prevent premature pivoting of the mirror glass to its anti-glare position in bright ambient light conditions.

7. A rear view mirror according to claim 6 in which the ambient light compensation means includes a photo sensor.

8. A rear view mirror according to claim 7 in which the photo sensor which is for sensing the presence of absence of light of a predetermined intensity which has passed through the mirror and the photo sensor of the ambient light compensation means are arranged in a bridge circuit.

9. A rearview mirror according to any one ofthe preceding claims and including separator means for separatig the mirror glass and the front plate when the mirror glass is in its viewing position.

10. A rear view mirror according to claim 9 in which the separator means is a pad of a resilient material.

11. A rearview mirroraccordingto anyone ofthe preceding claims in which the mounting means is a ball and socket joint.

12. A rear view mirror according to any one ofthe preceding claims in which the light reflective coating is such as to allow approximately 9% of lightfalling on the mirror glass to passthrough the mirror glass.

13. A rearview mirroraccording to any one ofthe preceding claims in which the partially light reflective coating is an aluminium coating, a stainless steel coating or a copper alloy coating.

14. A rear view mirror according to any one ofthe preceding claims and including circuit means and switch means for enabling the pivoting of the mirror glass, the circuit means being such asto prevent operation ofthe switch means until a first circuit including the photo sensor which isforsensing the presence or absence of light of a predetermined level that has passed through the housing, and a second circuit including a photo sensorforsensing ambient light conditions, are both in a condition requiring the mirror glass to pivot.

15. A rear view mirror according to claim 14 in which the mirorr glass is biased to its non-pivoted condition.

16. A rear view mirror according to any one of the preceding claims in which the pivot means for pivoting the mirror glass to its anti-glare position is an electro magnetic device, and in which the electro magnetic device is provided with a pair of polesthat are relatively far apart.

17. A rear view mirror according to claim 16 in which the electro magnetic device is provided with associated electrical circuitry such that more current is provided for actual pivoting of the mirror glass than is provided justto maintain the rear view mirror in an operable condition and also just to hold the pivoted mirror glass in its pivoted position.

18. A rear view mirror according to claim 17 and including a second solenoid to drive a relayto letin the higher current required.

19. Arearview mirror according to any one of claims 1 to 13 and including an electro magnetic device operable such as positively to drive the mirror glass from its normal viewing position to its anti-glare position, and also from its anti-glare position to its normal viewing position.

20. A rear view mirror according to claim 19 in which the electro magnetic device includes polarity reversing means for reversing polarity of a main solenoid such that the main solenoid attracts the mirrorglassto one position and repelsthe mirror glass to the other position.

21. A rearview mirror according to claim 20 in which the electro magnetic device attracts the mirror glass to its anti-glare position, and repels the mirror glass to its normal viewing position.

22. A rear view mirror according to claim 21 or claim 22 in which the electro magneitcdevice comprises the main solenoid for attracting and repelling the mirror glass, and a relay for driving the main solenoid and reversing the polarity of the solenoid.

23. A rear view mirror according to claim 22 in which the relay comprises a varistor connected across an auxiliary solenoid.

24. A rear view mirror according to any one ofthe preceding claims in which the front plate is made of an acrylic plastics material.

25. A rear view mirror according to any one ofthe preceding claims in which the front plate is provided with a darkened appearance.

26. A rear view mirror substantially as herein described with reference to the accompanying drawings.