US2754452A - Headlight dimmer system - Google Patents

Description

July 10, 1956 G. W. ONKSEN, JR., ETAL HEADLIGHT DINNER SYSTEM Filed June 1, 1950 W m. p

nited States Patent HEADLIGHT DIMM'ER SYSTEM George W. Onksen, Jr., and Charles W. Miller, Anderson, Ind, assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application June 1, 1950, Serial No. 165,392 11 Claims. (Cl. 315-83) The present invention relates to light sensitive control systems and more particularly to such light sensitive control systems as operate headlight control means for automotive vehicles for automatically switching between high beam and low beam filaments. Conventional automobile headlighting systems provide both what may be termed an upper and a lower beam, the first being utilized for high speed country night driving where it is necessary for the operator to see some distance ahead of the car. However, this amount of light and its direction are considerably annoying to an approaching driver and prevent him from adequately seeing his path ahead. In passing other vehicles, therefore, it is customary to switch the headlights to the low beam, which concentrates the lighting just ahead of the vehicle and prevents it from shining into the eyes of the oncoming driver. These systems have in the past been operated by a foot dimmer switch on the floor of the drivers compartment. However, it has been proposed to actuate means for changing from high beam to low beam due to approaching light rays automatically, and such a system is disclosed and illustrated in a co-pending application S. N. 37,984, filed July 10, 1948, in the names of George W. Onksen and Charles W. Miller, issued as Patent No. 2,679,616 on May 25, 1954. The present disclosure is an improvement over the above identified application.

In both of these disclosures the main system may be described as consisting of an electronic system which is energized from a suitable source of power to maintain the headlights on upper beam position for normal open country driving. Upon the appearance of oncoming light of sufiicient intensity, the electronic system is biased to cut off, deenergizing the electromagnetic switching means and permitting spring means to pull additional switching means to the low beam position. An auxiliary foot switch is also provided in either system to provide means for overriding the automatic and give a high beam at the will of the operator. In the system disclosed in S. N. 37,984, a phototube was used as the sensitive light element which was connected to a voltage amplifier tube and caused the latter to conduct when the oncoming light intensity reached a predetermined value.

It is an object of the present invention to provide a single light sensitive and amplifying means toprovide the controlling voltages for the headlight dimmer system.

It is a further object of our invention to utilize a photomultiplier tube to provide the controlling voltages, for a headlight dimmer system.

It is a still further object of our invention to provide a satisfactory high voltage power supply for the headlight dimming system utilizing a photomultiplier tube.

It is a still further object of our invention to provide an automatic headlight dimming system which is substantially unaffected by interference such as created by the ignition systems of internal combustion engines.

It is a still further object of our invention to provide an automatic electronic headlight dimming system that maintains stable operation over long periods without necessitating readjustment.

2,754,452 Patented July 10, 1956 It is a still further object of our invention to provide an automatic electronic headlight control system which uses commercially available tubes without the necessity for special selection.

With these and other objects in view which will become apparent as the specification proceeds, our invention will be best understood by reference to the following specification and claims and the illustrations in the accompanying drawings, in which the figure represents a schematic circuit diagram of a headlight dimmer system utilizing the embodiments of our invention.

Referring now more specifically to said diagram, there is shown therein an incoming power line 2 connected to a multiple position switch 4 which may engage either one of two stationary contacts 6 or 8. Contact 8 is connected through conductor 10 to a radio frequency choke coil 12 and thence through one section of condenser 14 to line 16, terminating in the mid-point of a transformer primary coil 18 of transformer 20. One end of the primary 18 is connected through line 22 to a stationary contact 24 of multiple contact vibrator 26. The other side of the transformer primary 18 is connected in like manner through line 28 to spaced opposed stationary contact 30 and also to one end of the vibrator operating coil 32. The other end of the operating coil is connected directly to the vibratory reed 34, which is in turn connected through its mounting and conductor 36 to the other side 38 of the condenser 14 and to ground. A second pair of spaced stationary contacts 40 and 42 are connected through lines 44 and 46 respectively, with the outside terminals of the secondary coil 48 of the transformer 20. A resistor 50 and condenser 52 are connected in series across the secondary 48.

The center tap of the secondary 48 is connected through line 54 to one end of a resistor 56, which is connected in series with two additional resistors 58 and 60 to form a voltage divider, the remote terminal of the latter being connected to ground through line 62. A condenser 64 is connected between line 54 and ground. A conductive line 66 is connected between resistances 58 and 56 and extends to a voltage regulator tube 68 and thence through line 70 to the input circuit of a high frequency oscillator. The oscillator system is enclosed in dash outline in the lower left hand corner of the figure and is adapted to utilize a regulated portion of the output of the multiple contact vibrator power pack, which may be, for example, 150 volt D. C. and change this to high frequency and of the proper high voltage. The dash outline around the oscillator indicates an aluminum shield 72 which is grounded.

The oscillator tube 74 has its plate 76 connected through line 78 with a tuned resonant circuit consisting of an industance 80, a variable capacitor 82 and a fixed capacitor 90, the opposite terminals of which are connected to incoming line 70 and also through line 84 and resistor 86 back to screen grid 88 of the tube 74. Inductance forms one part of a multi-part air core transformer group consisting of coil 80, coil 92 and coil 94, all of which are mounted in juxtaposition, so that currents flowing in one will induce corresponding proportional currents in the others. Condenser 96 is connected between grid 88 and ground. Control grid 98 of the tube 74 is connected through line 100 to line 102, which is in turn connected to one terminal of the coil 94. The opposite terminal of the coil 94 is connected through line 104 and through a filter network composed of capacitor 106 and resistance 108 in parallel to ground and to the cathode 110 of the tube. A variable condenser 112 is connected between line 100 and line 78. Coil 92 has one terminal directly connected to the anode 114 of a diode rectifier 116, the cathode 118 of which is grounded. The other terminal of the coil 92 is filtered to ground through condenser 93 and is connected through line 120 with one end of a plurality of small resistances 122, 124, 126, 128, 130, 132, 134, 136, 138 and 140 in series, the number of resistances equaling the number of stages in the photomultiplier tube 188. This provides a required high D. C.

voltage supply for the photo-multiplier tube and it may of the series, is connected through line 62 to ground. The

intermediate points between each of the series of resistors just referred to are connected through protective resistances 144, 146, 148, 150, 152, 154,156, 153 and 16% to a plurality of dynodes 164i, 166, 163, 17%), 172, 174, 176, 178 and 180 respectively. The first or lowest resistor 222 has its outside terminal connected in like manner through resistor 182 to a central cathode 184.

The output electrode or plate 186 of the photo-multiplier tube 188 is connected through line 196 with gri- 1-92 of the current amplifying tube 1%, the plate 1% of which is directly connectedthrough line 198 with line 200, which ex'tendsto one terminal of control relay 262.

The opposite terminal of control relay 202 is connected through line 204 to a point intermediate resistors 56 and 58. Line 1% is also connected to one end of a resistor 206, the opposite end of which is connected through line 208 to a tap between resistors 58 and 6d. The cathode 2100f the tube 194 is directly connected to adjustable tap 207 on resistor 58 to adjust the release of the circuit without affecting the dimming point whatsoever. An adjustable tap 212 on resistance 266 is connected through line 214 to cathode 216 of a diode rectifier tube 213. The anode 220 of this last named tube is connected through line 222 to control grid 224 of a current amplifier tube 226. The control grid 224 is also connected through line 228 and resistor 23% to ground. The cathode 231 is connected to ground. The plate 232 of tube 226 is connected through a limiting resistor 234 to line 2%.

Line 260 is also connected through resistor 236 to line 238 and thence to an auxiliary overriding foot switch 240,

which provides manual override for the system. Line 242, which is connected to some suitable source of power, is also connected to the movable armature 244 of relay 2132, which is normally spring biased by spring 246 to be spaced away from its stationary contact 248, but which is brought into contact therewith when the relay 292 is energized. Contact 248 is connected to line 25%) which extends to a further stationary spaced contact 252, engageable by a movable switch arm 254, which is the standard ratchet type foot switch and oscillates between stationary contact 252 and stationary contact 256, and is for highlow beam operation. Resistor 243-condenser 245 network is connected between lines 242 and 250 to prevent arcing between armature 244 and contact 243.

Contact 256 is'connected through line 258 to stationary contact 6. Oscillatory contact 254 is connected through line 260 to relay coil 262, the opposite terminal of which is grounded. Movable armature 264 of relay 262 is connected to a suitable source of power and is spring biased as shown by spring 270 to engage an upper stationary contact 266 which completes the circuit through line 268 to the low beam filaments. Thus, with the spring dominating, the circuit will be maintained on low beam. if, however, relay 262 is energized, attracting its armature 26 in opposition to spring 270, it will come down into contact with stationary contact 272, which is connected through line 274 with the high beam filament circuit and thus through this switching action the low beam elements are deenergized and the high beam energized.

In the operation of the device lead 2 is connected to the standard headlighting switch and may be considered to be the main source of power. Selector switch 4 is a manually operated switch and determines from its position whether the headlight system shall be conditioned for socalled standard foot switch operation or shall be automatically electronically controlled. When switch d is in its upper position, the system is conditioned for normal foot switch control and when foot switch 254 is depressed against contact 256, an obvious circuit is completed through relay 262 to energize the same, attract its armature, and close a system through line 274 to the high beam filaments. Since switch 254, 256, 252 is the conventionai ratchet type foot switch, upon the next operation of the button, arm 254 will be placed in contact with stationary contact 252 and away from contact 256. Its contact with stationary contact 252 has no effect, inasmuch as the electronic portion of the system is deenergized, but its movement away from contact 256 deenergizes relay 2622, allowing spring 270 to pull armature 264- up into contact with stationary contact 266 to energize the low beam. Thus, with the manual switch 4 in its upper posit. n, operation of the foot switch 254 alternately energizes high and low beam filaments.

if the operator turns switch 4 to its lower position contact with stationary contact 8, then the electronic system is energized to place the system under automatic operation. Foot switch 254 is adjusted to be in its uppermost position and the operation is as foilows: the multiple contact vibrator 26 in the upper left hand corner of the circuit receives D. C. power over line it through choke it, the taps on condenser 14, and line 16 to center of the primary coil 18. As the reed 34 moves back and forth through action of its coil 32 between the two sets of stationary contacts, the primary and secondary halfcircuits of the transformer are alternately energized to provide D. C. power on the output line 54 from the multiple contact vibrator section of the system. This voltage appearing on line 54 is applied to one end of a voltage divider or potentiometer consisting of three resistances, 56, 58 and 60 in series to ground. A tap line as is provided to take off a desired voltage from this voltage divider, which voltage then proceeds through voltage regulator tube 68 and appears on line 76 which is the input line to' a high frequency, high voltage oscillator.-

The voltage appearing on line 76 is a stable voltage since it has been regulated by the tube 68 and may for example, of the order of volts D. C. The oscillator tube 74in the high frequency, high voltage section receives this 150 volt input and generates through the normal oscillator action of such a system a high frequency voltage inthe coils 3t) and 94 of the air core transformer. The high frequency oscillator may be adjusted through the use of two variable condensers 82 and 112, although in some instances one of thesecondensers may be eliminated and only one used to provide the high frequency variation. This high frequency A. C. voltage is industively applied'to the secondary coil 2 of the air core transformer. The output of secondary coil 92 of the transformer is rectified by a rectifier tube 116 in circuit therewith,and the rectifier is so connected that tne voltage appearing on line 120 is negative with respect to ground rather than positive.

This negative voltage of a desired value is thus applied directly across a plurality of small resistors 122i4ii inclusive in series, and in this manner applies proper potential steps to each of the dynodes of the photo-multiplier tube 188. Line 120 is connected to the main cathode 184 through protective resistor 182 and an intermediate point between each of the other resistances is in like manner connected'through a protective resistance to each of the dynodes 'of the tube. 'Thus, the high frequency, high voltage power supply provides the necessary D. C. potentials for operating the phototube 133. The protective resistors 182 and 144 through inclusive are supplied in order to protect the phototube from becoming damaged due to the suns rays impinging thereon, and we have found that-when so protected thesephoto-multiplier tubes may be used in daylight with no damage thereto.

Light impinging upon the photocell causes an emission from the cathode which induces a plurality of sequential steps of secondary emission around the dynodes, each step causing an amplification of the emission until the anode is reached, at which time the feeble original currents have been amplified many times to reach a very useable and sizeable value at the anode. The photomultiplier tube therefore performs both a light sensitive pick-up function and an amplifier function and takes the place of two tubes and a control grid resistor of extremely high value in the system disclosed in our earlier filed application above identified. By having this action take place within one tube the difiiculties of introducing or picking up interference on the input to the first amplifier are avoided and permit the use of this system in proximity to internal combustion engine ignition systems.

The output from the anode is applied directly to the control grid 192 of a current amplifier tube 194, whose flow partially controls the operation of the main relay 202. This output current is also connected through tap 21.2 on resistor 206 with the cathode in the diode 218 which is directly connected to the control grid of a second current amplifier tube 226, having in its output a limiting resistor 234, which in turn is connected to relay 202. In the operation of this portion of the system, when both tubes 194 and 226 conduct, relay 202 is energized to attract its armature 244 and close an obvious circuit from the power line 242 through relay 262 to energize the latter and pull the headlights to high beam. Upon a decrease in current fiow in tube 194, which is biased to cut off first through the voltage applied to cathode 210 from the voltage divider, relay 202, being energized, will not drop out, there still being a sufficient flow through tube 226, which is biased at a much lower point, to maintain this relay energized. However, assuming that the current has now decreased below this value through tube 226 alone, the relay now drops out, permitting the headlights to go to low beam due to the action of the spring 270. If the current now begins to rise, it will increase first through tube 226 until it reaches the maximum value in that tube, which will still be insufiicient to pull in realy 202 until such time as tube 194 conducts to energize this realy and close its switch 244-248 to return the headlights to upper beam. Thus adjustment of capacitors 82 and 112 to vary the output of the oscillator will determine the dimming point when tube 226 falls to such a value that relay 202 drops and adjustment of tap 207 on resistor 58 will determine the reenergizing point of relay 202.

Let us thus assume normal country driving with the manual switch 4 set in its lower position, foot switch 254 in its upper position, and no light falling on the photocell. With no light on the photocell, substantially no current flows through line 190 and control grid 192 of "tube 194 is approximately at the same voltage potential as cathode 210. Also for the same reason control grid 224 of tube 226 is at the same voltage potential of its cathode. Under these conditions both tube 194 and 226 conduct current and relay 202 is energized. Switch 244 248 actuated thereby is closed, energizing relay 262 and closing switch 264272 thus energizing the headlights on the high beam. Assume a vehicle is approaching and the impinging light from its headlights falls on the photo-multiplier tube 188, causing it to conduct and amplify, lowering the potentials of grids 192 and 224 to first a point at which tube 194 cuts off and thereafter to a point at which tube 226 falls below the required current passage to retain relay 202 energized. That relay then becomes deenergized, permitting switch 244248 to open, deenergizing relay 262, and permitting the spring operation of 270 to switch the headlights to low beam. They will be retained on low beam until the light is removed from the photo-multiplier tube to a sufiicient degree to first cause increased flow through tube 226, and latterly flow through tube 194, which latter will permit b relay 202 to become energized and attract its armature 244, again switching to high beam. It is to be noted in this regard that the ratio of current flow through the two tubes 194 and 226 may be varied by moving the adjustable resistor tap 212 along resistor 206.

If, upon having the automatic system of the car switch the headlights to low beam, the operator then desires to manually override the system, since perhaps the oncoming driver has refused to dim his lights, and give a momentary high beam flicker, this may be accomplished by the operator closing a second foot switch 249, which closes an obvious energizing circuit for relay 292 and will keep that relay energized as long as it is closed to maintain the headlights on high beam.

The multiple contact vibrator system is, of course, utilized in order to provide a relatively high voltage from a low voltage source such, for example, as a storage battery, and may in this instance supply a sufficient voltage to line 54 to give a desired regulated D. C. voltage on line 79, which, as mentioned above, may be, in the present system, in the order of volts. It is, of course, well-known that the photo-multiplier tube does require a high voltage, and this is provided by the high frequency oscillator 7 4. The voltage needed by the photomultiplier tube may vary, it has been found, from 1100 volts to 400 volts, and it might be added in this regard that it is preferred in the present instance to use a negative voltage rather than a positive one. The desired variation between 400 and 1100 volts may be provided by adjustment of the condenser 32 or condenser 112, but once this adjustment has been made for the actual phototube installed and for the transformer S0-9492 used, it is not necessary to again make any further adjustment. While the output of the high frequency oscillator has been shown as rectified to supply D. C. voltage, A. C. can in many instances be used if the losses are not too great between the oscillator and photo-multiplier tube.

The resistances in series with each of the dynodes have een inserted therein in order to permit the usage of the photo-multiplier tube in daylight, as it was found early that these tubes could not be used without a current limiting means in series therewith in sunlight, or they would burn out. It has been found that the present system is much less sensitive to interference from the automobile ignition system that it is much less sensitive to variations due to moisture, and that the stability in continued operation is very good. The pick-up and bulk of the amplification takes place in the photo-multiplier tube per se, and is, therefore, much less apt to be affected by outside conditions.

We claim:

1. In a system for automatically dimming multiple filament headlamps, a regulated source of power, switching means for alternately energizing different filaments of the headlamps, high frequency oscillator means connected to the source of power to supply high voltage, photomultiplier means having input and output circuits, said input circuit being connected to the high voltage supply, current amplifier means connected to the output of the photo-multiplier means and to the switching means to control the energization of the filaments in response to the radiation falling on the photo-multiplier means.

2. In a system for automatically dimming multiple filament headlamps, a regulated source of power, switching means for alternately energizing dilferent filaments of the headlamps, high frequency oscillator means connected to the source of power to supply high voltage, voltage divider means connected to the output of the high frequency generator, a photo-multiplier tube having a plurality of electrodes, :1 portion of which are connected to the voltage divider, an output circuit connected to another electrode and to the switching means to control the same as the output of the photo-multiplier tube changes due to variations in radiation falling thereon.

3. In a power supply system, a fluctuating source of low voltage-D. C., amplifying means connected thereto to change-the'low voltage-D. C. to a higher voltage D. (3., voltage regulating means connected to the higher D. C. voltage, adjustable high frequency oscillator means connected to the regulated D. C. voltage to generate a still higher A; C. voltage and rectifier means connected to the output of the oscillator to reconvert the A. C. to an adjustable, stable D. C.

4. In a photosensitive control system, a source of regulated voltage, an adjustable high frequency oscillator connected'thereto, rectifier means connected to the output of the oscillator to convert it to D. C., a voltage divider connected to the rectified output, a photo-multiplier tube connected to the voltage divider and supplied with power for actuation, electron amplifier means connected to the output of the photo-multiplier tube, relay means connected to and controlled by the output of the electron amplifier means, the adjustment of the oscillator varying the power supply for the photo-multiplier tube, therefore the amount of light required to operate the relay.

5. In a photosensitive control system, a source of regulated voltage, a hi h frequency oscillator connected thereto, rectifier means connected to the output of the oscillator to convert it to D. C., a voltage divider connected to the rectified output, a photo-multiplier tube having a plurality of electrodes therein, circuit means connecting a portion of the electrodes with the voltage divider and impedance means in series with each circuit to each electrode;

6. In a photosensitive control system for automatically dimming multiple filament headlamps, a source of regulated voltage, a high frequency oscillator connected thereto, rectifier means connected to the output of the oscillator to convert it to D. C., a voltage divider connected to the rectified output, a photo-multiplier tube having a plurality of electrodes therein, circuit means connecting a portion of the electrodes with the voltage divider, impedance means in series with each circuit to each electrode, an output circuit connected to a further electrode, current amplifier means connected to said output and switching means connected to the current amplifier means and to the multiple filaments to control the same.

7. In a photosensitive control system for automatically dimming multiple filament headlamps, a source of low voltage, D. C. multiple contact vibrator means connected thereto for amplifying the same to a higher D. C. voltage, a high frequency oscillator connected to said higher D. C. voltage as a supply, rectifier means connected to said oscillator output, a voltage divider connected to said rectifier means having a high D. C. voltage thereacross, a photo-multiplier tube having a plurality of electrodes, conductive means connecting a portion of the electrodes to the voltage divider including an impedance in series with each connected electrode, an output circuit connected to another of the electrodes of the photo-multiplier tube and switching means connected to said output circuit and to the multiple filaments to cause selective energization of the filaments depending on the output of the photo-multiplier tube as determined by radiation falling thereon.

8. In a system for automatically dimming multiple filament headlamps, a source of power, switching means for alternately energizing difierent filaments of the headlamps, light sensitive means connected to the source, amplifier means connected to the light sensitive means including a pair of electronic tubes in parallel of different outputs and biased to conduct at different voltages, relay means connected to-the amplifier output and operating said switching means and independent means for adjusting'the bias on one of the tubes only to determine the reenergizing point for the relay means.

9. in a system for automatically dimming multiple filament headlamps, a source of power, switching means for alternately energizing different filaments of the headlamps, light sensitive means connected to the source, amplifier means connected to said light sensitive means, relay means connected to the amplifier output and operating said switching means, said amplifier means including a pair of electronic tubes in parallel relation whose combined conductivity operates the relay means, said tubes being biased to conduct at different input voltages, a limiting resistor in series with one of. the tubes to reduce its output so that relay energization and deenergization will take place at difierent levels of intensity of light and means for adjusting the bias on the tube not having resistance in series therewith to vary the point of relay reenergization.

10. In a photosensitive control system for automatically dimming multiple filament headlamps, a source of D. C. power, switching means for alternately energizing different filaments of the headlamps, an adjustable high frequency oscillator connected to said source, light sensitive means connected to the oscillator output, amplifier means connected to the light sensitive means including a pair of electronic tubes in parallel of different outputs and biased to conduct at different voltages, relay means connected to the amplifier output and operating said switching means of the headlamps, and independent means connected to the source of power and one of the tubes to adjust the bias on that tube so that the point of reenergization of the relay can be adjusted thereby and the point of deenergization by adjustment of the oscillator.

11. In a system for switching between a plurality of lamp filaments, a source of electrical power, switching means for selectively energizing different lamp filaments, an oscillator connected to the source of power to supply high voltage, photo-multiplier means having input and output circuits, said input circuit being connected to the oscillator for high voltage supply, and amplifier means connected to the'output circuit of the photo-multiplier means and to the switching means to control the energization of the filaments in response to the amount of light radiation falling on the photo-multiplier means.

Ret'erenees Cited in the file of this patent UNITED STATES PATENTS 2,004,778 Bedford June 11, 1935 2,104,463 Johnson Ian. 4, 1938 2,144,237 Wohlfarth Jan. 17, 1939 2,198,233 Snyder Apr. 23, 1940 2,227,095 Liebmann Dec. 31, 1940 2,276,832 Dome Mar. 17, 1942 2,280,303 Reynold Apr. 21, 1942 2,290,775 Snyder July 21, 1942 2,396,706 Kott Mar. 19, 1946 2,407,564 Martin et al Sept.'10, 1946 2,431,394 Friedman Iov. 25, 1947 2,446,718 Ray Aug. 10, 1948 2,463,119 Pyle et al. Mar. 1, 1949 2,476,389 Schmidt July 19, 1949 2,558,969 Le Croy July 3, 1951

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