United States Patent
`
`[191
`
`[11] Patent Number:
`
`4,868,720
`
`Sep. 19, 1989
`[45] Date of Patent:
`Miyauchi et al.
`
`[54] ROAD SURFACE-SENSITIVE BEAM
`PATTERN LEVELING SYSTEM FOR A
`VEHICLE HEADLAMP
`
`FOREIGN PATENT DOCUMENTS
`
`5618430 4/1981 Japan .
`
`Primary Examiner—-Ira S. Lazarus
`Assistant Examiner—Richard R. Cole
`Attorney, Agent, or Firm—Sughrue, Mion, Zinn,
`Macpeak & Seas
`
`ABSTRACT
`[57]
`A motorcycle headlamp capable of emitting a light
`beam with a beam pattern calculated to provide opti-
`mum forward illumination. In order to maintain the
`beam pattern in a level position about the lamp axis
`despite the lateral tipping of the motorcycle, at least one
`road sensor is employed for detecting the lateral angu-
`lar position of the vehicle with respect to the road sur-
`face by transmitting radiation such as an ultrasonic
`wave or infrared rays toward the road surface and re-
`ceiving its reflection from the road surface. Electric
`signals representative of lateral vehicle inclinationare
`fed to a central processor unit, which then causes ener-
`gization of a reversible electric motor built into the
`headlamp unit for leveling the beam pattern by revolv-
`ing the bulb and control lens of the headlamp unit rela-
`tive to the lamp housing. Thus, as the lateral angular
`position of the vehicle is detected in reference to the
`road surface, instead of to the perpendicular, the beam
`pattern can be maintained in the level position with
`respect to the road surface regardless of whether the
`road is banked or unbanked. Several different methods
`of detecting lateral vehicle inclination are disclosed.
`
`17 Claims, 20 Drawing Sheets
`
`[75]
`
`Inventors: Shizuya Miyauchi; Kiyoshi Wada,
`both of Shimizu, Japan
`
`[73] Assignee:
`
`Koito Seisakusho Co., Ltd., Shizuoka,
`Japan
`
`[21] Appl. No.: 206,449
`
`[22] Filed:
`
`Jun. 14, 1988
`
`Foreign Application Priority Data
`[30]
`Aug. 17, 1937 [JP]
`Japan ................................ 62-203804
`
`[51]
`
`Int. c1.4 ........................ B60Q 1/10; B60Q 11/oo;
`B62] 6/00
`
`[52] U.s. Cl. ........................................ 362/69; 362/71;
`A
`362/72; 362/287
`[53] Field of Search ....................... 362/66, 69, 71, 72,
`362/285, 237, 429
`
`[56]
`
`References Cited
`I
`U.S. PATENT DOCUMENTS
`
`3,939,339 2/1976 Alphen .................................. 362/72
`4,075,469
`2/1978 Alphen
`362/72
`4,204,270 5/1980 Poirier d’Ang d’Orsay .
`.. 362/71
`4,223,375 9/1980 Alphen .......
`362/72
`4,237,524 12/1980 Hundemer
`.. 362/71
`4,583,152 4/1986 Kawai et al.
`....... 362/71
`4,620,267 10/1986 Cibie ........ ..
`.. 362/66 X
`4,733,334
`3/1988 Krey ..................................... 362/71
`
`
`
`
`
`KOITO 103
`
`
`
`Koito Manufacturing v. Adaptive Headlam
`|PR2016-0007
`
`1
`
`KOITO 1032
`Koito Manufacturing v. Adaptive Headlamp
`IPR2016-00079
`
`

`
`U.S. Patent
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`Sep.19,1989
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`Sep.19, 1989
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`4,868,720
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`US. Patent
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`Sep. 19,1989
`
`Sheet 18 of 20
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`4,868,720
`
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`U.S. Patent
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`Sep. 19,1989
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`Sheet 19 of 20
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`4,868,720
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`1
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`4,868,720
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`2
`workability has proved to be very inconvenient because
`road surfaces are not necessary horizontal in their trans-
`verse direction. Curves in highways in particular are
`usually banked; that is, they tilt laterally upward from
`the inside edge to the outside edge so as to help vehicles
`smoothly round the curves without the possibility of
`being centrifugally carried off the track.
`Let us suppose that the motorcycle with the prior art
`beam pattern leveling system is taking a banked curve,
`with the vehicle laterally slanting out of the perpendicu-
`lar and into right angular relationship with the roadbed.
`Since the vehicle is then at an angle to the perpendicu-
`lar, the prior art system will detect this angle gyroscopi-
`cally and correspondingly readjust the beam pattern
`into an angled position with respect to the bank. Such
`readjustment
`is unnecessary or,
`indeed, undesirable.
`The beam pattern should have stayed in the level posi-
`tion with respect to the slanting road surface, just as
`when the vehicle is running an unbanked road.
`SUMMARY OF THE INVENTION
`
`We have hereby succeeded in overcoming the noted
`weakness of the prior art and in providing a truly satis-
`factory beam pattern leveling system which is respon-
`sive to the lateral tipping of the vehicle with respect to
`the road surface rather than to the perpendicular.
`Our invention may be summarized as a beam pattern
`leveling headlamp system for use on a motorcycle or
`like vehicle that is subject to lateral tipping as when
`taking a curve, comprising a headlamp unit on the vehi-
`cle for emitting a light beam having a prescribed beam
`pattern, the headlamp unit being capable of angularly
`displacing the beam pattern about the lamp axis. The
`headlamp unit is provided with beam pattern leveling
`means acting thereon for causing the headlamp unit to
`angularly displace the beam pattern about the lamp axis.
`The headlamp system further comprises vehicle inclina-
`tion detector means sensitive to a“road surface on which
`the vehicle is traveling, for detecting the degree of
`lateral tipping of the vehicle with respect to the road
`surface. In response to signals from the vehicle inclina-
`tion detector means, control means actuates the beam
`pattern leveling means so as to cause the head lamp unit
`to angularly displace the beam pattern about the lamp
`axis to an extent necessary for leveling the beam pattern
`in the face of the lateral tipping of the vehicle out of the
`right angular relationship to the road surface.
`According to more specific aspects of our invention,
`the vehicle inclination detector means comprises at least
`one road sensor which transmits some radiation, such as
`an ultrasonic wave or infrared rays, toward the road
`surface and which receives the reflection of the radia-
`tion from the road surface. One or two such road sen-
`sors may be employed in combination with the same
`number of angle sensor or sensors. By oscillating the
`road sensor or sensors transversely of the road while the
`vehicle is running, there can be obtained signals repre-
`sentative of the direction (either rightward or leftward
`of the vehicle) and angle of the lateral tipping of the
`vehicle with respect to the road surface. Alternatively,
`a greater number of road sensors may be fixedly
`mounted to the vehicle in suitable arrangement for pro-
`viding such signals.
`Thus, as the lateral inclination of the vehicle is de-
`tected with respect to the road surface, instead of to the
`perpendicular, in accordance with our invention, the
`beam pattern can always be maintained in the level
`
`ROAD SURFACE-SENSITIVE BEAM PATTERN
`LEVELING SYSTEM FOR A VEHICLE
`HEADLAMP
`
`BACKGROUND OF THE INVENTION
`
`Our invention relates generally to vehicular head-
`lamps and more specifically to those suitable for use on
`motorcycles or like vehicles that tilt laterally as when
`taking a curve or bend in a road. Still more specifically,
`our invention pertains to a system for use with such
`vehicular headlamps for automatically maintaining the
`pattern of the light beam, particularly the lower beam,
`thrown thereby in a level position about the beam axis
`in the face of variations in the lateral angle of the vehi-
`cle with respect to the road surface.
`Vehicle headlamps today are usually constructed to
`provide the so called “upper beam” and “lower beam”.
`The upper beam is intended primarily for distant illumi-
`nation when the vehicle is not meeting or following
`other vehicles. The lower beam is intended to illuminate
`the road ahead of the vehicle when it is meeting or
`following another vehicle. The pattern or cross sec-
`tional shape of the lower beam, in particular, is defi-
`nitely determined (see FIG. 10 of the drawing attached
`hereto) for the dual purpose of providing optimum road
`illumination for safe driving and of protecting other
`drivers from glare.
`A problem has been encountered in connection with
`such two beam headlamps on motorcycles or like two
`wheeled vehicles. The vehicles of this class must tilt
`laterally when taking a curve or bend in a road, in order
`to avoid being centrifugally carried off the road or
`toppling over. As the vehicle tips in either of the oppo-
`site lateral directions, so does the pattern of the lower
`beam emitted by its headlamp. Thus angularly displaced
`from its level position, the lower beam pattern fails to
`perform its intended functions, illuminating the road
`either too close to, or too far away from, the vehicle, or
`not illuminating its lane at all, and possibly dazzling the
`drivers of oncomming vehicles.
`Miyauchi et al. U.S. patent application Ser. No.
`07/137,021, pending filed Dec. 22, 1987, represents an
`attempted solution to the above stated problem. This
`prior application teaches a motorcycle headlamp unit
`wherein the bulb and the control lens are rigidly inter-
`connected for joint bidirectional rotation, within limits,
`about the lamp axis with respect to the lamp housing,
`thereby making possible the angular displacement of the
`beam pattern about the lamp axis. It also suggests a
`gyroscopic vehicle inclination detector for detecting
`the lateral, as well as longitudinal, tilting of the motor-
`cycle with respect to the perpendicular. As an electric
`output signal of the detector indicates the lateral tilting
`of the vehicle in either direction, the interconnected
`bulb and control lens of the headlamp unit is revolved in
`the required direction to such an extent that the beam
`pattern is maintained level about the lamp axis despite
`the vehicle tipping.
`We have found this known beam pattern leveling
`system unsatisfactory because of the use of the gyro-
`scopic vehicle inclination detector. Operating gyro-
`scopically, the prior art vehicle inclination detector can
`find the lateral vehicle angle with respect to the perpen-
`dicular and not to the road surface on which the vehicle
`is traveling. For this reason the known leveling system
`works well only as long as the vehicle is running on a
`road surface that is horizontal transversely. This limited
`
`10
`
`15
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`20
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`25
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`4,868,720
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`3
`position required by the lateral angle between the vehi-
`cle and the road surface. We are using the term “level
`position” of the light beam in reference to the transverse
`angle of the road surface which, of course, is not neces-
`sarily horizontal. When the road is banked, the vehicle
`will naturally incline out of the perpendicular into right
`angular relation with the road surface. Then the beam
`pattern will be in the “level position” with respect to
`the road surface even though it will be at an angle to the
`horizon. Thus our invention will contribute materially
`to safe driving on both banked and unbanked roads in
`the nighttime through enhancement of forward visibil-
`ity and reduction of glare.
`The above and other features and advantages of our
`invention and the manner of realizing them will become
`more apparent, and the invention itself will best be
`understood, from a study of the following description
`and appended claims, with reference had to the at-
`tached drawings showing some preferable embodiments
`of the invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`10
`
`20
`
`25
`
`30
`
`4
`lateral angle of the vehicle with respect to the road
`surface, the section being taken along a vertical plane
`transverse to the motorcycle to which the detector is
`mounted;
`FIG. 13 is a section through the vehicle inclination
`detector of FIG. 12, taken along the line XIII—XIII in
`FIG. 12;
`FIG. 14 is an exploded perspective view of the road
`sensor, "angle sensor, and road sensor drive motor in-
`cluded in the vehicle clination detector of FIGS. 12 and
`13;
`FIG. 15 is a vertical section through a modified vehi-
`cle inclination detector in accordance with our inven-
`tion;
`FIG. 16 is a vertical section through another modi-
`fied vehicle inclination detector in accordance with our
`invention;
`FIG. 17 is a section through the vehicle inclination
`detector of FIG. 16, the section being taken along the
`line XVII—XVII in FIG. 16;
`FIG. 18 is a block diagram of the general electrical
`configuration of the beam pattern leveling headlamp
`system in accordance with our invention;
`FIG. 19 is a block diagram showing in more detail the
`electric circuitry associated with the road sensor used in
`any of the three different forms of the vehicle inclina-
`tion detector shown in FIGS. 12-17;
`FIG. 20 is a diagram of waveforms appearing in the
`various parts of the road sensor circuitry of FIG. 19, the
`waveforms being useful in explaining the operation of
`the road sensor circuitry;
`FIG. 21 is a schematic electrical diagram, partly in
`block form, of the circuitry for controllably driving the
`reversible electric motor of the beam pattern leveling
`mechanism incorporated with the headlamp assembly
`of FIGS. 24;
`FIG. 22 is a schematic electrical diagram, partly in
`block form, of the circuitry associated with the angle
`sensor used in any of the three different forms of the
`vehicle inclination detector shown in FIGS. 12-17;
`FIG. 23 is a waveform diagram showing signals use-
`ful in explaining how the direction and angle of lateral
`tipping of the vehicle are ascertained from the output
`signals of the angle sensor circuitry of FIG. 22 and the
`road sensor circuitry of FIG. 19;
`FIG. 24 is a side elevation of a motorcycle, shown
`together with a rider thereon, having a pair of vehicle
`inclination detectors mounted thereto as an alternative
`means for detecting the lateral tipping of the vehicle
`with respect to the road surface;
`FIG. 25 is a schematic illustration of how the pair of
`vehicle inclination detectors of FIG. 24 scan the road
`surface for the detection of lateral vehicle inclination;
`FIG. 26 is a schematic illustration of how the pair of
`vehicle inclination detectors of FIG. 24 detects the
`lateral tipping of the vehicle when it is rounding a right-
`ward curve;
`FIG. 27 is a front elevation of a motorcycle, shown
`together with a rider thereon, having a plurality of road
`sensors mounted thereto as a second alternative means
`for detecting the lateral tipping of the vehicle with
`respect to the road surface, the view being explanatory
`of the arrangement of the road sensors as seen from the
`front of the motorcycle;
`FIG. 28 is a side elevation of the motorcycle of FIG.
`27, the view being explanatory of the arrangement of
`the road sensors as seen from the side of the vehicle; and
`
`FIG. 1 is a block diagram showing the general con-
`figuration of the road surface sensitive beam pattern
`leveling system in accordance with our invention;
`FIG. 2 is a top plan of the motorcycle headlamp
`assembly suitable for use with the beam pattern leveling
`system of our invention;
`FIG. 3 is a side elevation of the headlamp assembly of
`FIG. 2;
`FIG. 4 is an axial section through the headlamp as-
`sembly, taken along the line IV——IV in FIG. 2;
`FIG. Sis a perceptive view showing in particular the
`interconnected bulb and control lens of the headlamp
`assembly which are jointly rotatable relative to the 35
`lamp housing in order to revolve the beam pattern
`about the lamp axis;
`FIG. 6 is an enlarged perspective view of the bulb of
`the headlamp assembly;
`FIG. 7 is an enlarged end elevation of the bulb shown 40
`together with the connector, by which the bulb is con-
`nected to the control lens as best seen in FIG. 5, and
`means for mounting the bulb to the connector in the
`correct angular position about the lamp axis;
`FIG. 8 is a transverse section through the shield cap
`of the bulb, taken along the line VIII—VIII in FIG. '6
`and explanatory of how the lower beam of the desired
`pattern is emitted by the bulb;
`FIG. 9 is a diagram the lower beam pattern produced
`by the bulb having the shield cap of FIG. 8;
`FIG. 10 is a more concrete illustration of the pattern
`of the lower beam emitted by the bulb, the lower beam
`pattern being shown as actually thrown on the road on
`which the motorcycle is traveling;
`FIG. 11A is a end elevation of the motorcycle, to-
`gether with a rider thereon, incorporating the beam
`pattern leveling headlamp system of our invention, the
`view being explanatory of how the lateral vehicle angle
`is detected with respect to the road surface when the
`vehicle is traveling in an upstanding attitude or at righ
`angles with the road surface;
`'
`FIG. 11B is an illustration similar to FIG. 11A and
`explanatory of how the lateral vehicle angle is detected
`with respect to the road surface when the vehicle is
`running at an angle thereto;
`FIG. 12 is a section through the vehicle inclination
`detector, forming a part of the beam pattern leveling
`headlamp system of our invention, for detecting the
`
`45
`
`50
`
`55
`
`65
`
`23
`
`23
`
`

`
`5
`FIG. 29 is a rear elevation of the motorcycle of
`FIGS. 27 and 28, the vehicle being shown inclined in
`order to explain how such vehicle inclination is de-
`tected by the road sensors.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`1. General
`
`We will now describe the road surface sensitive beam
`pattern leveling system of our invention in detail as
`adapted for use with a motorcycle headlamp. The gen-
`eral organization of the leveling system will become
`apparent from its block diagrammatic representation in
`FIG. 1. The leveling system has a central processor unit
`(CPU) or very small computer 10, commercially avail-
`able in the form of a microprocessor on an integrated
`circuit chip, for performing the various processing and
`control functions hereinafter set forth. Connected to the
`CPU 10 is, first of all, a vehicle inclination detector 12
`for detecting the lateral angular position of the vehicle
`with respect to the road surface and, if the vehicle is
`laterally inclined out of the right angular relation with
`the road surface, the direction and angle of the inclina-
`tion. A beam pattern angle detector 14 is also connected
`to the CPU 10 for delivering thereto a signal representa-
`tive of the actual lateral inclination of the beam pattern‘
`about the beam axis.
`In response to the incoming signals indicative of the
`vehicle tilt and of the actual lateral beam pattern incli-
`nation, the CPU 10 activates, via a motor drive circuit
`which is not shown in FIG. 1, a reversible electric
`motor forming a part of a beam pattern leveling mecha-
`nism 16. When so energized, the beam pattern leveling
`‘motor will drive the required parts of the motorcycle
`headlamp for revolving the beam pattern about the
`lamp axis in such a direction, and through such an angle,
`that the beam pattern remains level with respect to the
`road surface despite the vehicle tilt.
`A vehicle speed detector 18 of conventional design is
`also coupled to the CPU 10 for delivering thereto a
`signal suggestive of the traveling speed of the vehicle.
`The CPU10 controls the operation of the beam pattern
`leveling mechanism 16 in order that the beam pattern
`may be angularly displaced to the level position at a
`speed matching the traveling speed of the vehicle.
`Shown connected to the vehicle angle detector 12 is a
`headlamp lighting switch 20 for turning the headlamp
`on and off. The complete beam pattern leveling system
`is to be electrically set into operation when the head-
`lamp is lit up by the closure of the switch 20.
`The following is a discussion in more concrete terms
`of a motorcycle headlamp assembly incorporating the
`beam pattern leveling system in accordance with the
`principles of FIG. 1. We will divide such discussion
`under several headings, with or without subheadings,
`for the ease of understanding.
`
`10
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`2. Lamp Unit
`
`2-1. Outline
`As shown in FIGS. 2-4, the headlamp assembly 22
`embodying our invention includes a lamp unit 23 having
`a lamp housing 24. Within this lamp housing 24 there
`are mounted a bulb or like light source 26, a paraboloi-
`dal reflector 28 and a control lens 30 in alignment about
`the lamp axis x—x. As better seen in FIG. 5, a metal
`made connector 32 rigidly interconnects the bulb 26 and
`the control lens 30 in prescribed relative angular posi-
`tions about the lamp axis x—x. The interconnected bulb
`
`65
`
`24
`
`4,868,720
`
`6
`26 and control lens 30 are jointly rotatable within limits
`in both directions about the lamp axis x-—x with respect
`to the lamp housing 24 and reflector 28 for the lateral
`leveling of the pattern of the beam emitted by the lamp
`unit 23.
`Both FIGS. 4 and 5 reveal the noted beam pattern
`leveling mechanism 16, including a reversible electric
`motor 34, which is compactly accommodated in the
`space bounded between the lamp housing 24 and the
`reflector 28. We will refer to the motor 34 as the level-
`ing motor in contradistinction from other motors to be
`set forth subsequently. The leveling mechanism 16 acts
`in this embodiment to bidireetionally revolve the bulb
`26 and control lens 30 about the lamp axis x-—x for
`maintaining the beam pattern in the level position with
`respect to the road surface despite the lateral tipping of
`the motorcycle. Seen in the same figures, the aforesaid
`beam pattern angle detector 14 functions to detect the
`lateral inclination of the beam pattern on the basis of the
`angular displacement of the bulb 26 and control lens 30
`with respect to the nonrotatable parts of the lamp unit
`23.
`The headlamp assembly 22 further includes a vertical
`aiming adjustment mechanism 36, FIG. 2, for adjusting
`the aim or beam angle in the vertical plane. The aiming
`adjustment can be of any known or suitable construc-
`tion and bears no direct pertinence to the beam pattern
`leveling system of our invention. Suffice it to say for the
`moment that the aiming adjustment mechanism 36 acts
`to pivot the lamp unit 23 about a horizontal axis extend-
`ing transversely of the motorcycle in order to compen-
`sate for the possible tilting of the vehicle in its longitudi-
`nal direction with a change in the load thereon.
`2-2. Lamp Housing
`As shown in FIGS. 2-4, the lamp housing 24 may be
`described as being substantially bowl shaped, opening
`forwardly of the motorcycle to which the lamp assem-
`bly 22 is mounted. It comprises a bowl shaped major
`portion 38, and an annular rim 40 screwed or otherwise
`fastened as at 42, FIG. 4, to the front edge of the major
`portion so as to form a forward extension thereof. The
`major portion 38 of the lamp housing 24 is mounted
`between a pair of support arms 44 for pivotal motion
`about a horizontal axis extending transversely of the
`motor cycle, as will be later described in more detail in
`connection with the vertical aiming adjustment mecha-
`nism 36.
`2-3. Reflector
`
`I Coaxially and immovably mounted within the lens
`housing 24 as in FIG. 4, the paraboloidal reflector 28
`has a reflective surface 46 in the shape of a paraboloid of
`revolution. The front edge portion of the reflector 28 is
`formed to provide two concentric L shaped flanges 48
`and 50 for supporting the control lens 30 and a cover
`lens 52 in a manner to be detailed presently. A circular
`opening 54 is formed concentrically in the rear end of
`the reflector 28. The edge of the reflector 28 bounding
`the opening 54 has an annular rim 56 protruding rear-
`wardly therefrom. The bulb 26 concentrically extends
`through the reflector opening 54 and is supported in a
`manner set forth hereafter for rotation relative to the
`reflector 28.
`2-4. Lens Mounting Means
`As shown also in FIG. 4, a mounting ring 58 is fitted
`over the reflector 28 in the vicinity of its front end. The
`mounting ring 58 has a plurality of lugs 60, one seen,
`formed in one piece therewith at constant circumferen-
`
`24
`
`

`
`4,868,720
`
`,
`
`7
`tial spacings. Disposed just forwardly of the mounting
`ring 58 is a retaining ring 62 which is firmly fitted over
`the flange 48 of the reflector 28. The retaining ring 62
`has an inturned rim 64 for closely engaging the thick-
`ened periphery of the cover lens 52 between itself and
`the reflector flange 48. With the cover lens 52 so
`mounted in position, the retaining ring 62 is welded or
`otherwise affixed to the lugs 60 of the mounting ring 58,
`which in turn is secured to the rim 40 of the lamp hous-
`ing 24 in any convenient manner. The lamp housing rim
`40 is fastened as at 42 to its major portion 38 after the
`mounting ring 58 has been secured thereto. The cover
`lens 52 may be considered a part of the housing means
`comprising the lamp housing 24.
`Disposed immediately behind or inside the cover lens
`52, the control lens 30 has its periphery slidably en-
`gaged between the L shaped flange 50 on the reflector
`28 and the periphery of the cover lens 52. The control
`lens 30 has a cylindrical recess 66 formed centrally
`therein for slidably receiving a cylindrical boss 68 on
`the cover lens 52. Thus the control lens 30 is rotatable
`relative to the reflector 28 and cover lens 52.
`2-5. Connection between Bulb and Control Lens
`The bulb 26 and the control lens 30 are rigidly inter-
`connected as aforesaid by the metal made connector 32
`for joint rotation about the lamp axis x—x with respect
`to the reflector 28 and cover lens 52. As best pictured in
`FIG. 5, the connector 32 has a disklike portion 70 which
`is centered about the lamp axis x—x and which has a
`hole 72, FIG. 4, formed centrally therein for concentri-
`cally surrounding the bulb 26. A plurality of, four in this
`embodiment, ribs 74 extend radially outwardly from the
`disklike portion 70 of the connector 32 at constant angu-
`lar spacings. The connector ribs 74 are each gently
`curved to extend along the reflective surface 46 of the
`reflector 28 and have their extremities embedded in the
`thickened periphery of the control lens 30.
`The connector 32 further includes a cylindrical por-
`tion 76 extending rearwardly from the edge of the disk-
`like portion 70 bounding the hole 72. The cylindrical
`portion 76 protrudes rearwardly of the reflector 28 by
`rotatably extending through the hole 54 in the reflector.
`A bulb mounting sleeve 78 is concentrically received in
`the cylindrical portion 76 and partly extends rearwardly
`therefrom. The cylindrical portion 76 of the connector
`32 and the bulb mounting sleeve 78 are rigidly intercon-
`nected as by welding. A bulb base sleeve 80 is concen-
`trically nested in the bulb mounting sleeve 78.
`As drawn on an enlarged scale in FIG. 6, the bulb
`base sleeve 80 coaxially surrounds the cylindrical base
`82 of the bulb 26 and is welded or otherwise secured
`thereto. The bulb base sleeve 80 has a plurality of, three
`in this embodiment, positioning lugs 84, 86 and 88 ex-
`tending radially outwardly from its rear end at constant
`angular spacings (lug 88 seen in FIG. 4). The lug 84,
`which is shown oriented upwardly in FIGS. 4-6,
`is
`wider than the other two lugs 86 and 88. These position-
`ing lugs 84, 86 and 88 are engaged in recesses 90, 92 and
`94, respectively, in the bulb mounting sleeve 78 (recess
`94 indicated in FIG. 7). The recess 90 is made wider
`than the other two recesses 92 and 94 for engagement
`with the wider lug 84 on the bulb base sleeve 80. Thus
`the bulb 26 can be mounted to the connector 32 via the
`sleeves 78 and 80 in the correct angular position relative
`to the control lens 30 and connector 32 and further
`locked against angular displacement relative to the
`same. A bulb retainer 96, FIG. 4, retains the bulb 26
`against axial displacement with respect to the connector
`
`8
`32. It is now apparent that the bulb 26 rotates with the
`control lens 30 and connector 32 about the lamp axis
`x—x relative to the reflector 28, cover lens 52 and so
`forth.
`2-6. Light Source
`With particular reference to FIG. 6 the light source
`of this headlamp unit 23 typically takes the form of the
`familiar double filament, halogen cycle incandescent
`bulb 26 for vehicular headlamp use. The bulb 26 has, in
`addition to the base 82, an envelope 98 of vitreous mate-
`rial within which there are coaxially mounted a lower
`beam filament 100 and an upper beam filament 102, with
`the former disposed forwardly of the latter. Also
`mounted within the envelope 98 is a shield cap 104
`approximately in the shape of a dish shielding the lower
`half and front of the lower beam filament 100. The
`shield cap 104 has a pair of opposite side edges 106 and
`108. FIG. 8 is explanatory of the relative angular posi-
`tions of these side edges 106 and 108 of the shield cap
`104 with respect to the lamp axis x when the wider
`positioning lug 84 on the bulb base sleeve 80 is oriented
`vertically upwardly. It will be noted that the left hand
`side edge 106, as seen in FIG. 8 which shows the shield
`cap 104 as viewed from the base end of the bulb 26, of
`the shield cap is located 15 degrees below the horizontal
`plane H—H containing the lamp axis x. The right hand
`side edge 108, on the other hand, of the shield cap 104
`is located on the horizontal plane H—H.
`When the bulb 26 is mounted in position within the
`lamp unit 23, as best depicted in FIG. 4, the upper beam
`filament 102 is positioned at the focus F of the reflector
`28. The lower beam filament 100 is located slightly
`forwardly of the reflector focus F.
`2-7. Beam Pattern
`Let us suppose that the bulb 26 is in the angular posi-
`tion of FIG. 7 about the beam axis x—x. The wider
`positioning lug 84 is displaced 15 degrees in a clockwise
`direction from its vertical position, with the result that
`the left hand side edge 106 of the shield cap 104 is on the
`horizontal plane containing the lamp axis x—x whereas
`the right hand side edge 108 is 15 degrees below the
`horizontal plane.
`FIG. 9 shows the resulting distribution of the beam
`thrown by the lamp unit 23 when the lower beam fila-
`ment 100 is lit up. The light zone includes an upwardly
`oriented region 110 which is located above the horizon-
`tal plane H—H containing the lamp (beam) axis and on
`the left hand side of the vertical plane V—V containing
`the beam axis. Further the upwardly oriented region
`110 slants down the beam axis at an angle of 15 degrees.
`Part of the light rays that have been emitted by the
`lower beam filament 100 pass over the lower right hand
`side edge 108 of the shield cap 104, to be reflected by
`the lower part of the paraboloidal reflector 28. As has
`been stated, the lower beam filament 100 is positioned
`slightly forwardly of the focus F of the reflector 28.
`Consequently, on being reflected by the reflector 28,
`such light rays will be inverted both horizontally and
`vertically, thereby creating the upwardly oriented re-
`gion 110.
`FIG. 10 is an illustration of the actual pattern 112 of
`the lower beam thrown as above by the lamp unit 23
`when the vehicle is running over a road 114 in the nor-
`mal vertical attitud