OA18846A - Sub headlight unit and sub headlight system for use in vehicle that leans into turns, and vehicle that leans into turns. - Google Patents

Abstract

To provide a sub headlight unit for use in a vehicle that leans into turns, by which occurrence of a situation where a rider feels uncomfortable about a change in an illumination range can be suppressed. A sub headlight unit for use in a vehicle that leans into turns, wherein the sub headlight unit includes a sub headlight light source that illuminates, at one side with respect to a width direction of the vehicle, an area ahead and outward of the vehicle with respect to the width direction of the vehicle, the brightness of the sub headlight light source changes in accordance with a lean angle of the vehicle, when the lean angle of the vehicle leaning to the one side with respect to the width direction of the vehicle reaches a reference value that is set for the sub headlight light source, the sub headlight light source lights up with a first brightness, and when the lean angle of the vehicle is equal to or greater than a lower value that is less than the reference value and less than the reference value, the sub headlight light source lights up with a brightness gradually increasing in a range lower than the first brightness according to the increase of the lean angle.

Description

SUB HEADLIGHT UNIT AND SUB HEADLIGHT SYSTEM FOR USE IN VEHICLE THAT LEANS INTO TURNS, AND VEHICLE THAT LEANS INTO TURNS

[0001]

The present invention relates to a sub headlight unit and a sub headlight System for use in a vehicle that leans into tums, and to a vehicle that leans into tums.

[0002]

In general, in a vehicle that leans into tums (such as saddle-ride type vehicles including motorcycles, three-wheeled motor vehicles, snowmobîles, and ATVs (ail terrain vehicles)), when the vehicle comers or tums at an intersection, a rider opérâtes a handlebar and additionally shifts his/her own weight in order to counteract centrifugal force acting on a vehicle body. Thereby, the vehicle tums with an attitude (hereinafter, also referred to as “lean attitude”) leaning to the inner side of a curve. On the other hand, in a vehicle that does not lean into tums, for example, in an automobile, when the vehicle corners or turns at an intersection, a rider opérâtes a steering wheel and tums with centrifugal force acting on a vehicle body. Therefore, in the vehicle that does not lean into tums, the vehicle body leans to the outer side of a curve due to the centrifugal force.

[0003]

In the vehicle that leans into tums, the tuming is made with an active use of the weight shifting of the rider hîmself/herself. Therefore, the vehicle body largely leans. In the vehicle that does not lean into tums, the vehicle body leans to the outer side of the curve due to the centrifugal force. The degree of this leaning varies depending on the running speed of the vehicle and the magnitude (radius) of the curve, and this leaning of the vehicle body is not utilized for the tuming. In the vehicle that does not lean into tums, it is préférable that the amount of leaning to the outer side of the curve due to the centrifugal force is small.

[0004]

Thus, at a time of comering or tuming at an intersection, the vehicle that leans into tums causes the vehicle body to lean to the inner side of the curve with a relatively large amount of leaning, while the vehicle that does not lean into tums causes the vehicle body to lean to the outer side of the curve with a relatively small amount of leaning.

[0005]

Normally, a vehicle is provided with a plurality of lights irrespective of whether or not the vehicle leans into turns. The lights include a light intended mainly to ensure a field of view of a rider of the vehicle and a light intended mainly to enable a surrounding vehicle or the like to recognize the presence of the own vehicle. A headlight is the light intended mainly to ensure the field of view of the rider of the vehicle, and in general, is configured to switch between a high beam (running headlight) and a low beam (passing headlight).

[0006]

The high beam, which emits light in a horizontal (upward) direction, ensures a field of view at a long distance. Generally, in order to avoid dazzling a rider of a surrounding vehicle, the high beam is used in a situation where there is no vehicle or the like existing ahead at night. The low beam, which emits light in a downward direction, is used even in a situation where there is a vehicle or the like existing ahead. Therefore, in a normal case, a vehicle often runs with the low beam tumed on.

[0007]

When the vehicle that leans into tums is running on a straight road, an illumination range of a headlight light source (low beam) spreads evenly to the left and right in an area ahead in an advancing direction and below a horizontal plane including the headlight light source. When the vehicle that leans into tums is running on a road curving to the left, the vehicle runs with the vehicle body inclined to the left. Accordingly, the illumination range of the headlight light source spreads downward to the left. As a resuit, a nearer position on a running lane is illuminated. Thus, the illumination range in an area inside the curve and ahead in the advancing direction is reduced.

[0008]

Therefore, a vehicle has been proposed in which, in addition to a main headlight that illuminâtes an area ahead of the vehicle, a pair of right and left sub headlights that are tumed on depending on the magnitude of a lean angle (angle of inclination of a vehicle body to the inner side of a curve relative to an upright state thereof) are provided as the headlight (WO 2010/061651 ). Each of the sub headlights includes two light sources (filaments). In the vehicle disclosed in WO 2010/061651, when the lean angle increases and reaches a predetermined value, one of the two light sources included in the sub headlight is tumed on. When the lean angle further increases and reaches a predetermined value, the two light sources are tumed on.

[0009]

Such a vehicle is known from WO 2010/061651.

[0010]

A situation where the vehicle comers or tums at an intersection is not always the same, and there are a wide variety of running scenes. The present inventors hâve studied cases where the vehicle disclosed in WO 2010/061651 runs in a wide variety of scenes, and found out the following problems.

[OOll]

In the vehicle disclosed in WO 2010/061651, when the vehicle corners or tums at an intersection, the illumination range of the sub headlight within a rider’s field of view largely changes, which sometimes causes the rider to feel uncomfortable.

[0012]

For example, even on a road having a curve with the same radius, some vehicles pass through the curve at a relatively low speed, and other vehicles pass through the curve at a relatively high speed. At this time, the lean angle of the vehicle passing at the high speed is changed more rapidly than the lean angle of the vehicle passing at the low speed. That is, even though a vehicle passes through a road having a curve with the same radius, the amount of change in the lean angle per unit time varies depending on the vehicle speed.

[0013]

Furthermore, even when the vehicle is running at the same speed, the lean angle is gently changed in a curve with a large radius while the lean angle is rapidly changed in a curve with a small radius. Accordingly, for example, in a case of continuously passing through a plurality of curves having different radii during touring on a mountain road, the amount of change in the lean angle per unit time changes in each curve, even though the speed does not change so much.

[0014]

In the vehicle disclosed in WO 2010/061651, the two light sources of the sub headlight are sequentially tumed on in accordance with an increase in the lean angle. Accordingly, at a time point when a light source is tumed on, an illumination range of this light source is additionally provided, which can suppress a réduction in the illumination range which may be caused by inclination ofthe vehicle.

Here, in accordance with an increase in the lean angle of the vehicle, an illumination range of a sub headlight produced on a road surface continuously approaches to the vehicle, and accordingly a cut-off line of the sub headlight also approaches to the vehicle. The speed of movement of the cut-off line of the sub headlight light source varies depending on the amount of change in the lean angle per unit time. In other words, the speed of movement of the cut-off line varies depending on a running scene.

Therefore, in a case where the speed of movement ofthe cut-off line largely changes upon each tum in a curve or in a case where the speed of movement of the cut-off line increases, the rider may feel uncomfortable.

[0015]

The présent invention has been made in view of the problems described above, and an object ofthe présent invention is to prevent a rider from feeling uncomfortable about a change in an illumination range in the course of an increase or decrease in the lean angle of a vehicle body.

[0016]

To solve the problems described above, the présent invention adopts the following configurations.

(l) A sub headlight unit for use in a vehicle that leans into tums, wherein the sub headlight unit includes a sub headlight light source that illuminâtes, at one side with respect to a width direction of the vehicle, an area ahead and outward of the vehicle with respect to the width direction of the vehicle, the brightness of the sub headlight light source changes in accordance with a lean angle of the vehicle, when the lean angle of the vehicle leaning to the one side with respect to the width direction of the vehicle reaches a reference value that is set for the sub headlight light source, the sub headlight light source lights up with a first brightness, and in a period from when the lean angle of the vehicle reaches a lower value that is less than the reference value to when the lean angle ofthe vehicle reaches the reference value, the sub headlight light source lights up with a brightness lower than the first brightness.

[0017]

In a State where a main headlight light source or a sub headlight light source (hereinafter also referred to as a first headlight light source) included în the vehicle has been already tumed on, when the lean angle increases, an illumination range produced on a road surface is reduced so that a cut-off line of the first headlight light source that has been already tumed on approaches to the vehicle. Therefore, the illumination range of the first headlight light source gradually moves away from a position a rider desires to see toward the vehicle.

In a configuration of (l), under such a situation, at a time point when the lean angle reaches the lower value that is less than the reference value before the lean angle reaches the reference value ofa second sub headlight light source that will be turned on next, the second sub headlight light source lights up with a brightness lower than the first brightness. As a resuit, an illumination range of the second sub headlight light source that is currently tumed on partially overlaps the cut-off line of the first headlight light source that has been previously tumed on. Here, the brightness of the second sub headlight light source is lower than the first brightness. Therefore, a situation where the tum-on of the second sub headlight makes the rider feel uncomfortable is suppressed.

Then, along with an increase in the lean angle, the illumination range of the first headlight light source is reduced so that the cut-off line approaches to the vehicle, and when the lean angle reaches the reference value that is set for the second headlight light source, the second headlight light source lights up with the first brightness. Accordingly, when the illumination range ofthe first headlight light source is moving away from the position the rider desires to see, the illumination range of the second headlight light source can spread over the position the rider des ires to see.

As a resuit, the cut-off line of the second headlight light source is more conspicuous to the rider than the cut-off line ofthe first headlight light source. An illumination range having a predetermined illuminance is enlarged along with an increase in the brightness of the second headlight light source from the brightness lower than the first brightness to the first brightness. Therefore, an effect of reducing the speed of approach of the cut-off line to the vehicle is exerted. Since the effect of reducing the speed of movement of the cut-off line is exerted, a change in the speed of movement of the cut-off line which occurs in each tum can be made small. This enables suppression of an uncomfortable feeling, which may otherwise be given to the rider.

Since a réduction in the illumination range of the headlight is suppressed, occurrence of a situation where the position the rider desires to see is not sufïiciently covered by the illumination range of the headlight can be suppressed. This enables suppression of an uncomfortable feeling, which may otherwise be given to the rider.

[0018]

Here, in order to suppress the speed of movement of the cut-off line, it is conceivabie to gradually increase the brightness of the headlight light source in accordance with a length of time having elapsed since the lean angle reached the reference value. In this case, however, a change in the brightness of the headlight light source is linked to time. Accordingly, the responsiveness to a change in the lean angle decreases, and there is a risk that a time period may occur during which the position the rider desires to see is not coïncident with the illumination range of the headlight.

in this respeck in the configuration of (l), the brightness of the headlight light source changes in accordance with the lean angle of the vehicle. This can reduce a change in the speed of movement ofthe cut-off line which occurs in each tum while ensuring the responsiveness to a change in the lean angle. This also enables suppression of occurrence of a time period during which the position the rider desires to see is not sufficiently covered by the illumination range of the headlight.

[0019] (2) The sub headlight unit according to ( l ), wherein when the lean angle of the vehicle reaches the lower value that is set for the sub headlight light source, an illumination range of the sub headlight light source contains a space above a horizontal line, when the lean angle of the vehicle reaches the reference value that is set for the sub headlight light source, the illumination range of the sub headlight light source is located in a space below the horizontal line.

[0020]

In a configuration of (2), when the lean angle of the vehicle reaches the reference value so that the sub headlight light source lights up with the first brightness, the illumination range of the sub headlight light source is located in a space below the horizontal line. Accordingly, occurrence of glare can be suppressed. When the lean angle reaches the lower value, the illumination range of the sub headlight light source contains a space above the horizontal line. However, the sub headlight light source lights up with a brightness lower than the first brightness, and therefore occurrence of glare can be suppressed.

[0021] (3) The sub headlight unit according to (l) or (2), wherein a cut-off line of the sub headlight light source obtained when the lean angle of the vehicle reaches the reference value that is set for the sub headlight light source is doser to horizontal than the cut-off line of the sub headlight light source obtained when the lean angle of the vehicle reaches the lower value that is set for the sub headlight light source.

[0022]

In a configuration of (3), when the lean angle reaches the reference value, the cut-off line of the sub headlight light source is close to horizontal. Accordingly, when the headlight light source lights up with the first brightness, a wide illumination range can be ensured on a road surface, with prévention of glare.

[0023] (4) The sub headlight unit according to any one of (l) to (3), wherein the sub headlight light source comprises a plurality of the sub headlight light sources, the reference value and the lower value are individually set for each of the sub headlight light sources.

[0024]

In a configuration of (4), along with an increase in the lean angle, the sub headlight light sources, sequentially from the one having the smallest reference value set therefor, lights up with the brightness lower than the first brightness and then lights up with the first brightness. Sequentially changing the brightness of each sub headlight light source in this manner can slow the speed of movement ofthe cut-off line while suppressing a réduction in the illumination range ofthe sub headlight light source in accordance with the increase in the lean angle.

[0025] (5) The sub headlight unit according to (4), wherein the reference value of one sub headlight light source is equal to or smaller than the lower value of another sub headlight light source for which the next greatest reference value after that of the one sub headlight light source is set.

[0026]

There is the upper limit in an output of the headlight light source, and energy such as fuel loaded on the vehicle is also limited. Therefore, it is préférable to make effective use of the headlight light source based on the relationship between the energy efficiency and the illumination range. Even if the second headlight light source lights up with a brightness lower than the first brightness before the first headlight light source lights up with the first brightness, it is difïicult to ftilly enjoy the advantage of compensation of the illumination range by the second headlight light source, because the brightness of the first headlight light source will be subsequently increased. Therefore, in a configuration of (5), in the course of an increase in the lean angle, the second headlight light source is caused to light up with a brightness lower than the first brightness after the first headlight light source lights up with the first brightness. This allows an effective use ofthe respective headlight light sources.

Here, the first headlight light source means such a headlight light source that the reference value of the lean angle set therefor is the first to be reached in the course ofthe lean angle increasing and reaching the reference value of the headlight light source. The second headlight light source means such a headlight light source that the reference value of the lean angle set therefor is the next to be reached after the reference value of the first headlight light source is reached.

[0027] (6) The sub headlight unit according to any one of (l) to (5), wherein an optical axis of the sub headlight light source is fixed, the sub headlight light source whose optical axis is fixed lights up with the first brightness when the lean angle of the vehicle reaches the reference value that is set for the sub headlight light source, and lights up with a brightness lower than the first brightness in the period from when the lean angle of the vehicle reaches the lower value that is less than the reference value to when the lean angle ofthe vehicle reaches the reference value.

[0028]

In order to suppress the speed of movement of the cut-off line, it is conceivable to provide a movable mechanism and a movable member for physically changîng the orientation of the light source and to control the movable mechanism and the movable member in accordance with an increase in the lean angle, thereby adjusting the orientation of the light source. However, to provide the movable mechanism and the movable member, it is necessary that a space for them is ensured in the vehicle. Therefore, this method is not suitable for a relatively small vehicle.

In this respect, in a configuration of (6), the optical axis of the headlight light source is fixed. Therefore, any movable mechanism and any movable member for moving the optical axis of the headlight light source are not required. This enables avoidance of an increase in the size ofthe sub headlight unit.

[0029] (7) A sub headlight system for use in a vehicle that leans into tums, the sub headlight system including:

the sub headlight unit according to any one of (l) to (6);

a control part that changes the brightness of the sub headlight light source in accordance with the lean angle ofthe vehicle; and a détection part that detects a variable available for obtaining the lean angle of the vehicle, wherein, when the lean angle of the vehicle leaning to the one side with respect to the width direction of the vehicle reaches the reference value that is set for the sub headlight light source, the control part causes the sub headlight light source to light up with the first brightness, and in the period from when the lean angle of the vehicle reaches the lower value that is less than the reference value to when the lean angle of the vehicle reaches the reference value, the control part causes the sub headlight light source to light up with a brightness lower than the first brightness.

[0030]

In a configuration of (7), an AFS (Adaptive Front-Lighting System) is achieved that enables suppression of occurrence of a situation where the rider feels uncomfortabie about a change in the illumination range.

[0031] (8) The sub headlight system according to (7), wherein the sub headlight system includes a voltage detector that detects a supply voltage value of a voltage that is supplied from a battery provided in the vehicle to the sub headlight light source, the control part performs:

a comparison process for comparing the supply voltage value detected by the voltage detector against a reference voltage value of the battery; and an adjustment process for adjustîng, based on a resuit of the comparison. the brightness of the sub headlight light source that changes in accordance with the lean angle of the vehicle.

[0032]

A configuration of (8) can suppress a change in the illumination range of the sub headlight light source which is caused by a variation in the supply voltage supplied from the battery to the sub headlight light source. Accordingly, occurrence of glare can be suppressed.

[0033]

The present invention can also adopt the following configurations.

(8-l) The sub headlight system according to (7), wherein the sub headlight system includes a température detector that detects the température of the sub headlight light source or the vicinity of the sub headlight light source, the control part performs an adjustment process for adjustîng, based on the température detected by the température detector, the brightness of the sub headlight light source that changes în accordance with the lean angle of the vehicle.

[0034]

A configuration of (8-l) can correct a réduction in the brightness of the sub headlight light source (for example, an LED) caused by a température rise.

[0035] (8-2) The sub headlight system according to (7), wherein the control part perforais:

a distance information acquisition process for acquirîng distance information indicating a distance the vehicle has traveled; and an adjustment process for adjusting, based on the distance information acquired in the distance information acquisition process, the brightness of the sub headlight light source that changes in accordance with the lean angle of the vehicle.

[0036] (8-3) The sub headlight system according to (7), wherein the control part performs:

a time information acquisition process for acquiring time information indicating a period of use of the vehicle or the sub headlight light source; and an adjustment process for adjusting, based on the time information acquired in the time information acquisition process, the brightness of the sub headlight light source that changes in accordance with the lean angle of the vehicle.

[0037]

A configuration of (8-2) or (8-3) can correct a réduction în the brightness of the sub headlight light source caused by a long-term use.

[0038] (9) The sub headlight system according to (8), wherein when the lean angle of the vehicle is in a range of at least the lower value and less than the reference value, the control part performs the adjustment process, while when the lean angle of the vehicle is out of the range, the control part does not perform the adjustment process.

[0039]

In a configuration of (9), when the lean angle of the vehicle is out of the range, the adjustment process is not performed. Accordingly, at a time of causing the sub headlight light source to light up with a relatively high output in accordance with the lean angle, the output can be made without limitation because the adjustment process is not performed. Therefore, a wide illumination range can be ensured.

[0040]

The configuration of (9) is also adoptable in the sub headlight system according to any one of (8-l) to (8-3) described above.

[0041]

ΙΟ (ΙΟ) A vehicle that leans Into tums, the vehicle including the system according to any one of (7) to (9).

[0042]

A configuration of (10) enables suppression of occurrence of a situation where the rider feels uncomfortable about a change in the illumination range.

[0043] (l l) A method to control a sub headlight unit for use in a vehicie that leans into tums, with a sub headlight light source, wherein the sub headlight light source illuminâtes, at one side with respect to a width direction of the vehicle, an area ahead and outward of the vehicle with respect to the width direction of the vehicle, the brightness of the sub headlight light source changes in accordance with a lean angle of the vehicle, when the lean angle of the vehicle leaning to the one side with respect to the width direction of the vehicle reaches a reference value that is set for the sub headlight light source, the sub headlight light source lights up with a first brightness, and in a period from when the lean angle of the vehicle reaches a lower value that is less than the reference value to when the lean angle of the vehicle reaches the reference value, the sub headlight light source lights up with a brightness lower than the first brightness.

[0044] (12) A method to control a sub headlight unit for use in a vehicle that leans into tums, with a sub headlight light source according to (11), wherein when the lean angle of the vehicle reaches the lower value that is set for the sub headlight light source, an illumination range of the sub headlight light source contains a space above a horizontal line, when the lean angle of the vehicle reaches the reference value that is set for the sub headlight light source, the illumination range of the sub headlight light source is located in a space below the horizontal line.

[0045] (13) A method to control a sub headlight unit for use in a vehicle that leans into tums, with a sub headlight light source according to (12), wherein a cut-off line of the sub headlight light source obtained when the lean angle of the vehicle reaches the reference value that is set for the sub headlight light source is doser to horizontal than the cut-off line of the sub headlight light source obtained when the lean angle of the vehicle reaches the lower value that is set for the sub headlight light source.

[0046] (14) A method to control a sub headlight unit for use in a vehicle that leans into tums, with a sub headlight light source according to (13), wherein

U the reference value and the lower value are individually set for each of a piurality of sub headlight light sources, the reference value of one sub headlight light source is equal to or smaller than the lower value of another sub headlight light source for which the next greatest reference value after that of the one sub headlight light source is set.

[0047] (15) A method to control a sub headlight unit for use in a vehicle that leans into tums, with a sub headlight light source according to (14), wherein an optîcal axis ofthe sub headlight light source is fixed, the sub headlight light source whose optical axis is fixed lights up with the first brightness when the lean angle of the vehicle reaches the reference value that is set for the sub headlight light source, and lights up with a brightness lower than the first brightness in the period from when the lean angle of the vehicle reaches the lower value that is less than the reference value to when the lean angle of the vehicle reaches the reference value.

[0048]

Here, in the present invention, the optical axis is a straight line that passes through a light source and the center of a maximum illuminance portion of emitted light. The center of the maximum illuminance portion of the emitted light can be identified by emitting light from a light source to a screen that is placed ahead of the light source. This screen illuminance test can be implemented by a method specified in JIS D1619. Also, the cut-off line and the illumination range having the predetermined illuminance can be identified based on a resuit (such as an isolux distribution map) of the screen illuminance test mentîoned above. In the present invention, the illumination range means an illumination range having a predetermined illuminance, and this predetermined illuminance is not particularly limited. The cut-off line and the illumination range having the predetermined illuminance in a plan view can be identified based on a roadsurface light distribution that is obtained by converting the resuit of the screen illuminance test mentîoned above into the road-surface light distribution. The conversion into the road-surface light distribution can be implemented by a conventionally known method. To be spécifie, through commonly-used drawing and géométrie calculation, conversion from a screen illuminance value into a road-surface illuminance value can be performed. In such a case, the following expression (I) is usable. In the following expression (I), D represents a light source, E represents a point on a road surface, and F represents a point of intersection at which the screen placed between D and E intersects with a straight line connecting D to E.

Road-surface illuminance (Lx) = Screen Illuminance (Lx) x [(Distance between D and F (m)) / (Distance between D and E (m))]² ... (I)

[0049]

These and other objects, features, aspects and advantages of the present invention will become apparent to those skiiled in the art from the following detailed description, which, taken in conjunction with the accompanying drawings, discloses some embodiments of the présent invention.

[0050]

The présent invention enables suppression of occurrence of a situation where a rider feels uncomfortable about a change in an illumination range.

[0051]

[FIG. I] A front elevational view schematically showing a motorcycle according to a first embodiment of the présent invention.

[FIG. 2] A block diagram showing a basic configuration conceming sub headlight light sources of the motorcycle shown in FIG. I.

[FIG. 3] A front elevational view schematically showing optical axes and cut-off lines of the sub headlight light sources ofthe motorcycle in an upright State.

[FIG. 4] A chart showing the relationship between a lean angle of the motorcycle and the brightnesses of the sub headlight light sources according to the first embodiment of the présent invention.

[FIG. 5] (a) is a diagram schematically showing a screen light distribution obtained when the lean angle ofthe motorcycle takes a value that is in the range from a lower value Ti to a reference value Ki and is relatively close to the lower value Ti; (b) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle takes a value that is in the range from the lower value Ti to the reference value K] and is greater than the lean angle shown in (a); and (c) is a diagram schematically showing a screen light distribution obtained when the lean angle ofthe motorcycle takes the reference value Ki.

[FIG. 6] (a) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle takes an upper value Ui ; (b) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle takes a value that is in the range from a lower value T2 to a reference value K.2; and (c) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle takes the reference value K2.

[FIG. 7] (a) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle takes a value that is in the range from a lower value T3 to a reference value K3; and (b) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle takes the reference value K3.

[FIG. 8] A diagram illustrating a light distribution, schematically showing an illumination range of a headlight produced on a road surface at a time when the lean angle of the motorcycle takes a value that is in the range from the lower value Ti to the reference value Ki and is relatively close to the lower value T|.

[FIG. 9] A diagram illustrating a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle takes a value that is in the range from the lower value Ti to the reference value K[ and is greater than the lean angle shown in FIG. 8.

[FIG. 10] A diagram illustrating a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle takes the reference value Kj.

[FIG. 11] A diagram illustrating a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle takes the upper value Ui.

[FIG. 12] A diagram illustrating a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle takes a value that is in the range from the lower value T₂ to the reference value K₂.

[FIG. 13] A diagram illustrating a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle takes the reference value K₂.

[FIG. 14] A diagram illustrating a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle takes an upper value U₂.

[FIG. 15] A diagram illustrating a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle takes a value that is in the range from the lower value T₃ to the reference value K₃.

[FIG. 16] A diagram illustrating a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle takes the reference value K₃.

[FIG. 17] A diagram illustrating a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle takes the upper value U₃.

[FIG. 18] A diagram showing the relationship between the lean angle of the motorcycle and an illumination distance of the headlight illuminating a path of the motorcycle according to the first embodiment ofthe present invention.

[FIG. 19] A chart showing the relationship between the lean angle of the motorcycle and the brightnesses of the sub headlight light sources according to a second embodiment of the present invention.

[FIG. 20] A diagram showing the relationship between the lean angle of the

I4 motorcycle and the illumination distance of the headlight illuminating a path of the motorcycle according to the second embodiment of the present invention,

[0052] <First Embodiment>

FIG. I is a front elevational view schematically showing a motorcycle according to a first embodiment of the present invention.

A motorcycle 10 is an example of a vehicle that leans into tums according to the present invention. In the present invention, no particular limitation is put on the vehicle that leans into tums. For example, saddie-ride type vehicles including motorcycles, three-wheeled I0 motor vehicles, snowmobîles, and ATVs (ail terrain vehicles) may be mentioned. In the following description, the terms “front” and “back” are terms with respect to an advancing direction of the vehicle, the terms “up” and “down” are terms with respect to the vertical direction of the vehicle, and the terms “right” and “left” are terms with respect to a rider.

[0053]

The motorcycle 10 includes a handlebar 12. An operation switch 15 is provided in a left portion of the handlebar 12 with respect to a width direction of the vehicle. The operation switch 15 includes a beam switch 15B and a flasher switch 15F (see FIG. 2). A steering shaft (not shown) is fixed to a center portion of the handlebar 12 with respect to the width direction of the vehicle. The steering shaft extends downward through a headpipe (not shown). A 20 frontfork 17 is provided at a lower end of the steering shaft. A front wheel 16 is rotatably supported at the lower end of the frontfork 17. The headpipe is a member constituting a vehicle body frame. In the present invention, no particular limitation is put on the vehicle body frame, and a conventionally known configuration is adoptable.

[0054]

A front cover 18 covers a front part of the headpipe having the steering shaft passing therethrough. On a front surface of the front cover 18, a main headlight 11 is provided in a center portion with respect to the width direction of the vehicle. The main headlight 11 includes a high beam light source HH (running headlight) and a low beam light source l IL (passing headlight). The high beam light source l IH illuminâtes an area ahead of the motorcycle 10 at a height equal to or above a horizontal plane of the main headlight l L The low beam light source l IL illuminâtes an area ahead of the motorcycle 10 at a height below the horizontal plane of the main headlight 11.

[0055]

The high beam light source HH and the low beam light source l IL are configured 35 such that only one of them is tumed on in accordance with an operation performed on the beam switch I5B (see FIG. 2) by the rider.

[0056]

The motorcycle 10 includes a sub headlight 13. The sub headlight 13 is composed of two sub headlight units 13L and 13R of variable light distribution type. Each of the sub headlight units 13L and 13R is provided at each side with respect to the width direction of the vehicle. The sub headlight unit 13L includes a plurality of sub headlight light sources l3La, l3Lb, and l3Lc. The sub headlight light sources l3La, l3Lb, and l3Lc are arranged in this order from the center toward the upper left with respect to the width direction of the vehicle. The sub headlight light sources I3La, l3Lb, and l3Lc illuminate an area ahead and left-lateral with respect to the width direction of the vehicle. Illumination ranges of the sub headlight light sources l3La, l3Lb, and l3Lc are arranged in this order from the center toward the upper left with respect to the width direction of the vehicle. The illumination ranges of the sub headlight light sources l3La, l3Lb, and !3Lc overlap one another. The sub headlight unit 13R includes a plurality of sub headlight light sources l3Ra, l3Rb, and l3Rc. The sub headlight light sources l3Ra, l3Rb, and !3Rc are arranged in this order from the center toward the upper right with respect to the width direction of the vehicle. The sub headlight light sources l3Ra, l3Rb, and l3Rc illuminate an area ahead and right-lateral with respect to the width direction of the vehicle. Illumination ranges of the sub headlight light sources l3Ra, l3Rb, and l3Rc are arranged în this order from the center toward the upper right with respect to the width direction of the vehicle. The illumination ranges of the sub headlight light sources l3Ra, l3Rb, and l3Rc overlap one another. Optica! axes ofthe sub headlight light sources l3La to l3Lc, !3Ra to l3Rc are fixed, and not rnoved in accordance with a lean angle. A reflector (not shown) of the sub headlight light source is also fixed, and not rnoved in accordance with the lean angle. In this embodiment, no particular limitation is put on the sub headlight light source. For example, an LED is adoptable. A mono-focus type light source is also adoptable as the sub headlight light source. As for how the sub headlight light sources l3La to !3Lc, !3Ra to l3Rc are arranged in the motorcycle 10, the above-described arrangement manner is merely an illustrative example of the present invention. The present invention is not limited to this example.

[0057]

Flashers 14L and 14R, serving as direction indicators, are provided at both sides ofthe motorcycle 10 with respect to the width direction of the vehicle. The flashers 14L and 14R are configured such that only one of them is tumed on in accordance with an operation performed on the flasher switch 15F (see FIG. 2) by the rider.

[0058]

The plurality of sub headlight light sources !3La, l3Lb, and I3Lc, which are positioned at the left side in the motorcycle 10 with respect to the width direction of the vehicle, are arranged between the main headlight 11 and the flasher 14L. The plurality of sub headlight light sources l3Ra, l3Rb, and l3Rc, which are positioned at the right side in the motorcycle 10, are arranged between the main headlight 11 and the flasher 14R. In the present invention, no particular limitation is put on the positional relationship between the sub headlight light source and the flasher with respect to the width direction of the vehicle. For example, it may be acceptable that the sub headlight light source is provided outside the flasher with respect to the width direction of the vehicle.

[0059]

The plurality of sub headlight light sources I3La, l3Lb, and l3Lc are provided above the main headlight 11 and the flasher 14L. The plurality of sub headlight light sources !3Ra, l3Rb, and l3Rc are provided above the main headlight 11 and the flasher I4R.

[0060]

The plurality of sub headlight light sources l3La to l3Lc, which are provided to the left with respect to the width direction of the vehicle, illuminate an area ahead of and left-lateral to the motorcycle 10. The plurality of sub headlight light sources 13Ra to I3Rc, which are provided to the right with respect to the width direction of the vehicle, illuminate an area ahead of and right-lateral to the motorcycle 10,

[0061]

FIG. 2 is a block diagram showing a basic configuration conceming the sub headlight light sources !3Lato l3Lc, !3Rato l3Rc ofthe motorcycle 10 shown in FIG. I.

[0062]

The operation switch 15 includes the beam switch 15B and the flasher switch I5F. The beam switch 15B is connected to the high beam light source HH and the low beam light source HL included in the main headlight 11. When the rider opérâtes the beam switch 15B, tum-on/tum-off of the high beam light source HH and the low beam light source HL is switched in accordance with the operation performed on the beam switch 15B.

[0063]

The flasher switch 15F îs connected to the flashers I4L and 14R. When the rider opérâtes the flasher switch 15F, one of the flashers I4L and 14R is caused to flash in accordance with the operation performed on the flasher switch 15F.

[0064]

In the motorcycle I0, a lean angle sensor 22 and a vehicle speed sensor 23 are provided. In this embodiment, the lean angle sensor 22 is a gyro sensor that detects the angular velocity about an axis in the front-back direction of the motorcycle 10. The lean angle sensor 22 supplies, to a controller 20, a signal indicating the detected angular velocity (roll rate) about the axis in the front-back direction. The vehicle speed sensor 23 detects the vehicle speed, and supplies, to the controller 20, a signal indicating the detected vehicle speed. Each time a predetermined timing cornes during running, the controller 20 calculâtes the lean angle of the motorcycle 10 based on the angular velocity about the axis in the front-back direction and the vehicle speed.

[0065]

In this embodiment, the roll rate is integrated over time, and the vehicle speed is used as correction information, thereby calculating the lean angle. However, in the present invention, a method for calculating the lean angle is not limited to this example. In the calculation ofthe lean angle, the vehicle speed is not an essential variable. For calculating the lean angle, a conventionally known method is adoptable. For example, the calculation may be performed based on a static equilibrium équation by using the yaw rate (angular velocîty about an axis in the vertical direction) and the vehicle speed. The correction information is not limited to the vehicle speed. For example, it may be acceptable to provide a plurality of gyro sensors and G sensors and use values obtained from these sensors and the vehicle speed as the correction information. Instead of the vehicle speed, GPS position information and/or geomagnetic information may be used as the correction information. No particular limitation is put on sensors (détection part) for detecting variables that are available for obtaining the lean angle. An appropriate sensor may be provided in accordance with variables available for the calculation.

[0066]

The controller 20 includes a memory (not shown).

The memory stores, in the form of data, a plurality of reference values K(°) to be compared with the lean angle. In this embodiment, the memory stores three reference values (a first reference value Ki, a second reference value K.2, and a third reference value K₃). The first reference value Ki, the second reference value Ki, and the third reference value K3 satîsfy the relationship of‘'first reference value Ki < second reference value K2 < third reference value K3”.

[0067]

The memory stores, in the form of data, lower values T(°) to be compared with the lean angle. The lower value corresponds to the lean angle obtained when a light source that has been tumed off is starting to light up in the course of an increase in the lean angle.

In this embodiment, the memory stores three lower values (a first lower value Ti, a second lower value T2, and a third lower value T₃). The first lower value Ti, the second lower value T₂, and the third lower value T3 satîsfy the relationship of “first lower value Ti < second lower value T2 < third lower value T3”. Each of the lower values T is smaller than each corresponding reference value K. To be spécifie, the relationship of “first lower value Ti < first reference value Kj” is satisfied.

[0068]

The memory stores, in the form of data, upper values U(°) to be compared with the lean angle. The upper value corresponds to the lean angle obtained when a light source is starting to light up with the highest brightness in the course of an increase in the lean angle.

In this embodiment, the memory stores three upper values (a first upper value Ui, a second upper value U2, and a third upper value U₃). The first upper value Ui, the second upper value U2, and the third upper value U3 satisfy the relationship of “first upper value Ui < second upper value U₂ < third upper value U3”. Each of the upper values U is greater than each corresponding reference value K. To be spécifie, the relationship of “first reference value Ki < first upper value Ui” is satisfied.

[0069]

The memory stores, in the forni of data, spécifie values I(°) to be compared with the lean angle. The spécifie value corresponds to the lean angle obtained when a light source that has lighted up with the highest brightness is starting to dim in the course of an increase in the lean angle.

In this embodiment, the memory stores two spécifie values (a first spécifie value Ii and a second spécifie value I2). The first spécifie value li and the second spécifie value I2 satisfy the relationship of “first spécifie value Ii < second spécifie value b”. Each of the spécifie values I is greater than each corresponding upper value U. To be spécifie, the relationship of “first upper value Ui < first spécifie value ΙΓ is satisfied.

[0070]

The memory stores, in the form of data, defined values J(°) to be compared with the lean angle. The defined value corresponds to the lean angle obtained when the lowest brightness îs achieved in the course of an increase in the lean angle beyond the spécifie value. While the lean angle is equal to or greater than the defined value, the state (brightness) obtained when the lean angle takes the defined value is maintained.

In this embodiment, the memory stores two defined values (a first defined value Ji and a second defined value J2). The first defined value Ji and the second defined value J2 satisfy the relationship of “first defined value Ji < second defined value J₂”. Each ofthe defined values J is greater than each corresponding spécifie value I. To be spécifie, the relationship of “first spécifie value h < first defined value Ji” is satisfied.

[0071]

The first reference value Ki, the first lower value Ti, the first upper value Ui, the first spécifie value Ii, and the first defined value J i are associated with the sub headiight light sources l3La and l3Ra.

The second reference value K2, the second lower value T₂, the second upper value U₂, the second spécifie value I₂, and the second defined value J₂ are associated with the sub headiight light sources l3Lb and !3Rb.

The third reference value K3, the third lower value T3, and the third upper value U3 are associated with the sub headiight light sources l3Lc and (3Rc. The sub headiight light sources l3Lc and !3Rc, with which the greatest reference value is associated, hâve no spécifie value and no defined value associated therewith.

The relationship between each variable and the brightness of the sub headiight light source will be detaîled later with reference to FIG. 4.

[0072]

An answerback main unît 21 is connected to the controller 20. The answerback main unit 21 receives a signal radio wave from a remote control key 25.

[0073]

The sub headlight light sources l3La to l3Lc, l3Ra to l3Rc are connected to the controller 20. A power source 26 (battery) is connected to the high beam light source l IH and the low beam light source l IL via the beam switch I5B. The power source 26 is connected to the flashers 14L and 14R via the flasher switch 15F. The power source 26 is connected to the controller 20.

[0074]

The controller 20 Controls the brightnesses of the sub headlight light sources l3La to l3Lc, !3Ra to l3Rc. In this embodiment, the sub headlight light sources l3La to l3Lc, l3Ra to l3Rc are configured of LEDs. The controller 20 performs a puise width modulation control (PWM control) to adjust the duty cycle, and thereby the brightnesses are controlled (dimming control).

A method for performing the dimming control on the sub headlight light source is not partîcularly limited. For example, it may be conceivable to control a current to be supplied to the sub headlight light source, or to control a voltage to be supplied to the sub headlight light source.

[0075]

Alternatively, a single sub headlight light source may include a plurality of light sources having different brightnesses. In this case, the dimming control on the sub headlight light source can be implemented by switching which of the light sources is tumed on. For example, in a case where a single sub headlight light source includes two light sources having different brightnesses, the brightness of the light source can be controlled by switching the tumed-on light source from the light source configured to light up with a first brightness to the light source configured to light up with a second brightness.

[0076]

Furthermore, a single sub headlight light source may include a plurality of light sources. In this case, the dimming control on the sub headlight light source can be implemented by changing the number or combination of light sources that are tumed on. The brightnesses of the plurality of light sources may be either different or the same. For example, in a case where a single sub headlight light source includes a plurality of light sources (for example, four light sources) having the same brightness, tuming on part of the plurality of light sources enables the sub headlight light source to light up with the first brightness, while tuming on ail the plurality of light sources enables the sub headlight light source to light up with the second brightness.

[0077]

In the motorcycle 10, though not shown in FIG. 2, a voltage detector (not shown) for detecting a supply voltage that is supplied from the power source 26 to each ofthe sub headlight light sources !3La to !3Lc, I3Ra to l3Rc may be provided in a cable that connects the controller 20 to each of the sub headlight light sources l3La to l3Lc, l3Ra to 13Rc. A supply voltage value detected by the voltage detector is, in the form of data, supplied to the controller 20 at a predetermined timing, for example.

In this case, data indicating a reference voltage value of the power source 26 is stored in the memory of the controller 20. The controller 20 performs an information acquisition process for acquiring data indicating the supply voltage value from the voltage detector, and compares the supply voltage value against the reference voltage value, to calculate a différence between the supply voltage value and the reference voltage value.

The memory of the controller 20 stores a data table indicating a correspondence relationship ofthe rate ofcorrection of the brightness of the sub headlight light source relative to the différence between the supply voltage value and the reference voltage value. In this data table, as the absolute value of the différence between the supply voltage value and the reference voltage value increases, the absolute value of the rate of correction of the brightness of the sub headlight light source increases. When a différence of the supply voltage value from the reference voltage value is a positive value, the rate of correction is set to be a négative value. Accordingly, after correction, the brightness of the sub headlight light source is reduced as compared with that before the correction. On the other hand, when a différence ofthe supply voltage value from the reference voltage value is a négative value, the rate of correction is set to be a positive value. Accordingly, after correction, the brightness of the sub headlight light source is increased as compared with that before the correction. A correction object to be corrected is not particularly limited. At least one of a voltage value, a current value, and a duty cycle value may be adopted as the correction object.

It may be also acceptable that the memory stores a table associating the supply voltage value with the rate of correction of the brightness of the sub headlight light source. In this table data, the rate of correction is set based on the reference voltage value. In a case of using such a table data, it is not always necessary that the reference voltage value is stored in the memory, and the controller 20 does not hâve to calculate the différence of the supply voltage value from the reference voltage value. In this case, an indirect comparison between the supply voltage value and the reference voltage value is performed. Furthermore, although the above-described example describes a case where the memory includes the data table, the rate of correction may be calculated through computing with use of the supply voltage value or with use ofthe différence of the supply voltage value from the reference voltage value. Then, based on the rate of correction thus obtained, the value of the correction object (such as the voltage, the current, the duty cycle) is corrected. Thereby, a change in the brightness of each of the sub headlight light sources 13La to 13Lc, 13Ra to 13Rc, which is caused by a variation in the supply voltage of the power source 26, can be suppressed. Here, it may be also possible that the controller 20 Controls the supply voltage supplied to each of the sub headlight light sources l3La to 13Lc, so that the supply voltage supplied from the controller 20 to each of the sub headlight light sources 13La to 13Lc, 13Ra to 13Rc is made constant. In this case, the brightness of each of the sub headlight light sources 13La to 13Lc, 13Ra to 13Rc can be controlled by adjusting the current value or the duty cycle.

In this embodiment, when the lean angle of the motorcycle 10 is in a range of at least a lower limit value and less than the reference value, the above-described brightness control (adjustment process) is performed on the sub headlight light sources 13La to 13Lc, 13Ra to 13Rc, while when the lean angle is out of this range, the brightness control is not performed. Accordingly, at a time of causîng the sub headlight light source to light up with a high brightness, an output of the sub headlight light source can be made without limitation, to make it possible to ensure a wide illumination range. However, the present invention is not limited to this example. The above-described brightness control may be performed irrespective of the lean angle of the motorcycle 10.

[0078]

FIG. 3 is a front elevational view schematically showing optical axes and cut-off lînes ofthe sub headlight light sources 13Lato 13Lc, 13Rato 13Rc ofthe motorcycle 10 în an upright State.

[0079]

The motorcycle 10 stands upright on a fiat ground G. An optical axis Ao ofthe low beam light source 11L is located below a horizon H of the low beam light source 11 L. A cutoff line Lo of the low beam light source 1 IL is located above the optical axis Ao, and located below the horizon H of the low beam light source 1 IL. The cut-off line Lo extends right and left along the width direction of the vehicle. An illumination range of the low beam light source 1 IL covers both of the right and left sides with respect to the width direction of the vehicle.

[0080]

The optical axes ALi to ALj of the sub headlight light sources 13La to 13Lc are located outward in the order of the optical axes ALi to ALj with respect to the width direction of the vehicle. The optical axes ALi to AL3 of the sub headlight light sources l3La to 13Lc are located above the optical axis Ao of the low beam light source 1 IL.

[0081]

Inclination angles Θ1 to Θ3 of cut-off fines LLi to LL3 of the sub headlight light sources l3La to !3Lc increase in the order of the inclination angles θι to 63.

The inclination angles Oi to Θ3 of the cut-off lines LLi to LL3 of the sub headlight light sources 13La to 13Lc are set to be values increasing at intervals from 0° to θι, (h, and Θ3 in this order. The interval between 0° and 0j is Θ]. When the interval between 0₂ and θι is defined as 5 0₂’ and the interval between Θ3 and 02 is defined as Θ3’, the intervals θι, θ2’, and 63’ satisfy

0i>0₂’>0₃’. In other words, a larger inclination angle (θι to 63) has a smaller interval (θι, θ₂’, θ3’). Here, in the present invention, the relationship among the inclination angles (θι to Θ3) is not limited to this example. The intervals (θι, θ₂’, Θ3’) may be regular intervals, that is, the relationship of θι=θ₂’=θ3’ may be established.

[0082]

No particular limitation is put on the relationship between the inclination angle (θι to Θ3) of the cut-off line (LLi to LL3) of each sub headlight light source (13La to 13Lc) and the reference value (Ki to K₃) set for the sub headlight light source (13La to 13Lc). These values (angles) may be either different or the same. A state where these values are the same includes a 15 state where these values are substantially the same.

[0083]

The cut-off lines LLi to LL3 ofthe sub headlight light sources I3La to 13Lc define the upper end edges of the illumination ranges of the sub headlight light sources 13La to l3Lc, respectively, though not shown in FIG. 3. Therefore, the illumination ranges of the sub 20 headlight light sources 13La to 13Lc are located below the cut-off lines LLi to LL3 ofthe sub headlight light sources 13La to 13Lc. Accordingly, each of the illumination ranges of the sub headlight light sources 13La to 13Lc includes a space above the horizon H, and their locations are higher in ascending order of the illumination range of the sub headlight light source 13La, the illumination range of the sub headlight light source 13Lb, and the illumination range of the sub 25 headlight light source I3Lc. The illumination ranges of the sub headlight 13La to 13Lc are located at the left side with respect to the width direction of the vehicle.

Except for whether the sub headlight light sources are provided at the right side or the left side of the symmetry, the sub headlight light sources 13Ra to 13Rc are identical to the sub headlight light sources 13La to 13Lc described above. Therefore, a description thereof will be 30 omitted.

[0084]

Next, a change in the brightness of the sub headlight 13 in accordance with an increase in the lean angle will be described with reference to FIG. 4.

FIG. 4 is a chart showing the relationship between the lean angle ofthe motorcycle 10 35 and the brightnesses of the sub headlight light sources 13La to 13Lc according to the first embodiment ofthe present invention. Among brightnesses Qi to Q3 ofthe sub headlight light sources 13La to 13Lc, Qi represents a first brightness, Q₂ represents a second brightness, and Q₃ represents a third brightness. The brightnesses Qi to Qj of the sub headlight light sources l3La to l3Lc satisfy the relationship of Qs<Qi<Q2.

[0085]

[Lean Angle - 0°]

When the lean angle is 0°, each of the light sources of the sub headlight 13 îs in the following state.

The sub headlight light source l3La is not tumed on.

The sub headlight light source !3Lb is not tumed on.

The sub headlight light source l3Lc is not tumed on.

[0086]

[0° < Lean Angle(°) < First Reference Value Ki]

In the course of an increase in the lean angle from 0°, each of the light sources of the sub headlight 13 is as follows.

The sub headlight light source l3La starts to light up when the lean angle reaches the first lower value Ti that is set for the sub headlight light source l3La. When the lean angle is in the range from the first lower value Ti to the first reference value Ki, the brightness of the sub headlight light source !3La continuously increases along with the increase in the lean angle. That is, when the lean angle is in the range from the first lower value Ti to the first reference value Ki, the sub headlight light source I3La lights up with a brightness lower than the first brightness Qi.

The sub headlight light source l3Lb is not turned on.

The sub headlight light source l3Lc is not tumed on.

[0087]

[Lean Angle(°) = First Reference Value Ki]

When the lean angle reaches the reference value Ki that is set for the sub headlight light source l3La, each ofthe light sources ofthe sub headlight 13 is in the following state.

The sub headlight light source !3La lights up with the first brightness Qi.

The sub headlight light source 13Lb is not tumed on.

The sub headlight light source l3Lc is not tumed on.

[0088]

[First Reference Value Ki < Lean Angle(°) < Second Reference Value K2]

In the course of an increase in the lean angle from the first reference value Ki, each of the light sources of the sub headlight 13 is as follows.

The brightness of the sub headlight light source 13La continuously increases along with the increase in the lean angle until the lean angle reaches the first upper value Ui. When the lean angle reaches the first upper value Ui, the sub headlight light source !3La lights up with the second brightness Q2. When the lean angle is in the range from the first upper value Ui to the first spécifie value II, the sub headlight light source l3La lights up with the second brightness 02.

The sub headlight light source l3Lb starts to light up when the lean angle reaches the second lower value T₂ that is set for the sub headlight light source l3Lb. When the lean angle îs in the range from the second lower value T₂ to the second reference value K₂, the brightness of the sub headlight light source I3Lb continuously increases along with the increase in the lean angle.

The sub headlight light source l3Lc is not tumed on.

[0089]

[Lean Angle(°) = Second Reference Value K₂]

When the lean angle reaches the reference value K₂ that is set for the sub headlight light source l3Lb, each of the light sources of the sub headlight 13 is in the following state.

The sub headlight light source l3La lights up with the brightness Q₂.

The sub headlight light source !3Lb lights up with the brightness Qi.

The sub headlight light source l3Lc is not tumed on.

[0090]

[Second Reference Value K₂ < Lean Angle(°) < Third Reference Value K.3]

In the course of an increase in the lean angle from the second reference value K₂, each of the light sources of the sub headlight 13 is as follows.

The sub headlight light source 13La lights up with the second brightness Q₂ until the lean angle reaches the first spécifie value Ii. After the lean angle reaches the first spécifie value Ii, the brightness of the sub headlight light source 13La continuously decreases along with the increase in the lean angle.

The brightness of the sub headlight light source 13Lb continuously increases along with the increase in the lean angle when the lean angle is in the range from the second reference value K₂ to the second upper value U₂. When the lean angle reaches the second upper value U₂, the sub headlight light source 13Lb lights up with the second brightness Q₂.

The sub headlight light source 13Lc starts to light up when the lean angle reaches the third lower value Tj that is set for the sub headlight light source 13Lc. When the lean angle is in the range from the third lower value T3 to the third reference value K3, the brightness of the sub headlight light source 13Lc continuously increases along with the increase in the lean angle.

[0091]

[Lean Angle(°) = Third Reference Value K 3 J

When the lean angle reaches the reference value K3 that is set for the sub headlight light source 13Lc, each of the light sources ofthe sub headlight 13 is in the following state.

The sub headlight light source 13La lights up with a brightness lower than the second brightness Q₂ and higher than the third brightness Q3.

The sub headlight light source l3Lb lights up with the second brightness Q2.

The sub headlight light source l3Lc lights up with the first brightness Qi.

[0092]

[Third Reference Value K3 < Lean Angle(⁰)]

In the course of an increase in the lean angle from the reference value K3, each of the light sources of the sub headlight 13 is as follows.

The brightness of the sub headlight light source l3La continuously decreases along with the increase in the lean angle until the lean angle reaches the first defined value Ji. When the lean angle is equal to or greater than the first defined value Ji, the sub headlight light source l3La lights up with the brightness Q3.

The sub headlight light source l3Lb lights up with the second brightness Q2 until the lean angle reaches the second spécifie value I2. After the lean angle reaches the second spécifie value I2, the brightness of the sub headlight light source l3Lb continuously decreases along with the increase in the lean angle. When the lean angle is equal to or greater than the second defined value J2, the sub headlight light source l3Lb lights up with the brightness Q3.

The sub headlight light source l3Lc lights up with the brightness Q2 when the lean angle is equal to or greater than the upper value U3.

[0093]

The brightnesses of the sub headlight light sources l3La to l3Lc are changed in accordance with the lean angle, as follows.

When the lean angle is equal to or greater than 0° and less than the lower value Ti to T3 that is set for the sub headlight light source l3La to l3Lc, the corresponding sub headlight light source l3La to l3Lc is turned off.

When the lean angle is equal to or greater than the lower value Ti to T3 that is set for the sub headlight light source l3La to l3Lc and less than the reference value Κι to K3 that is set for the sub headlight light source l3La to l3Lc, the corresponding sub headlight light source l3La to l3Lc lights up with a brightness lower than the first brightness Qi. When the lean angle is equal to or greater than the lower value Ti to T3 and less than the reference value Ki to K3, the brightness of the corresponding sub headlight light source l3La to !3Lc continuously increases along with an increase in the lean angle, and the brightness of the corresponding sub headlight light source l3La to l3Lc continuously decreases along with a decrease in the lean angle.

When the lean angle takes the reference value Ki to K3, the corresponding sub headlight light source 13La to l3Lc lights up with the first brightness Qi.

When the lean angle is greater than the reference value Ki to K3 and less than the upper value U] to U3, the corresponding sub headlight light source l3La to l3Lc lights up with a brightness higher than the first brightness Qi and lower than the second brightness Q2. When the lean angle is greater than the reference value Ki to K3 and less than the upper value Ut to U3, the brightness of the corresponding sub headlight light source I3La to l3Lc continuously increases along with an increase in the lean angle, and the brightness of the corresponding sub headlight light source l3La to I3Lc continuously decreases along with a decrease in the lean angle.

When the lean angle takes the upper value Ut to U3, the corresponding sub headlight light source 13La to 13Lc lights up with the second brightness Q2.

In this embodiment, when the lean angle is equal to or greater than the lower value Ti to T3 that is set for the sub headlight light source 13La to 13Lc and less than the reference value K, to K3 that is set for the sub headlight light source 13La to 13Lc, the brightness of the corresponding sub headlight light sources 13La to 13Lc continuously increases along with an increase in the lean angle. However, the present invention is not limited to this example. In the present invention, it sufïices that, when the lean angle takes the lower value Ti to T3, the corresponding sub headlight light source 13La to 13Lc lights up with a brightness lower than the first brightness Qi. Therefore, the corresponding sub headlight light source 13La to 13Lc may light up with a predetermined brightness lower than the first brightness Qi. However, when the lean angle is equal to or greater than the lower value Tl to T3 that is set for the sub headlight light source 13La to 13Lc and less than the reference value Kl to K3 that is set for the sub headlight light source 13La to 13Lc, continuously increasing the brightness of the sub headlight light source I3La to 13Lc in accordance with an increase in the lean angle causes the brightness of the sub headlight light source 13La to 13Lc to gradually increase. This can suppress occurrence of a situation where the corresponding headlight light source 13La to 13Lc suddenly lights up with a high brightness to make the rider feel uncomfortable.

[0094] in this embodiment, the spécifie value and the defined value are not set for the sub headlight light source 13Lc having the greatest reference value set therefor among the plurality of sub headlight light sources 13La to 13Lc. Thus, even when the lean angle increases beyond the upper value U3, the sub headlight light source 13Lc having the greatest reference value set therefor keeps lighting up with the second brightness Q2.

On the other hand, for the sub headlight light sources 13La and 13Lb having the reference values smaller than the greatest reference value set therefor, the spécifie values h and I2 and the defined values Ji and J2 are set, respectively.

When the lean angle is greater than the upper value Ui, U2 and equal to or less than the spécifie value Ii, I₂, the corresponding sub headlight light source 13La, l3Lb having the reference value smaller than the greatest reference value set therefor lights up with the second brightness Q2. When the lean angle is greater than the spécifie value h, I2 and less than the defined value Ji, J₂, the corresponding sub headlight light source 13La, 13Lb having the référencé value smaller than the greatest reference value set therefor lîghts up with a brightness lower than the second brightness Qz and higher than the third brightness Q3. When the lean angle is greater than the spécifie value Ii, h and less than the defined value Ji, Jz, the brightness ofthe corresponding sub headlight light source l3La, l3Lb having the reference value smaller than the greatest reference value set therefor continuously decreases along with an increase in the lean angle, and the brightness of the corresponding sub headlight light source l3La, 13Lb having the reference value smaller than the greatest reference value set therefor continuously increases along with a decrease in the lean angle. When the lean angle is equal to or greater than the defined value Ji, Jz, the corresponding sub headlight light source l3La, l3Lb lights up with the third brightness Q3.

This embodiment describes a case where the spécifie value and the defined value are not set for one sub headlight light source !3Lc having the greatest reference value set therefor. However, the present invention is not limited to this example. It may be acceptable that the spécifie values and the defined values are set for ali the sub headlight light sources l3La to l3Lc.

[0095]

In FIG. 4, the duty cycle of a voltage supplied to the sub headlight light source is adopted as an index of the brightness of the sub headlight light source. However, in the present invention, the index of the brightness of the sub headlight light source is not limited to this example. Examples of the index include a supply voltage, a supplied current, an illuminance obtained at a position at a predetermined distance from the light source, and a luminance of the light source. When any index is adopted, the above-described magnitude relationship (Qî^^Qz) among the brightnesses of the sub headlight light source is established. The brightnesses Qi, Q2, and Q3 are not particularly limited, and appropriately set as needed. In this embodiment, the sub headlight light sources l3La to l3Lc and the sub headlight light source l3Ra to l3Rc adopt the same brightnesses Qi, Q₂, and Q3. However, the present invention is not limited to this example, and appropriate setting is made as needed.

[0096]

Next, a change in a screen light distribution of the headlight in accordance with the lean angle of the motorcycle 10 will be described with reference to FIGS. 5 to 7.

[0097]

FIG. 5(a) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle IO takes a value that is in the range from the lower value Ti to the reference value Ki and is relatively close to the lower value Ti.

An illumination range LB of the low beam light source l IL is located ahead in front of the motorcycle IO. An illumination range SHi of the sub headlight light source l3La is located above a left portion of the illumination range LB. The cut-off line LLi of the sub headlight light source 13La is located above the horizon H. Here, the sub headlight light source l3La lights up with a brightness lower than the brightness Qi (FIG. 4).

[0098]

FIG. 5(b) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle 10 takes a value that is in the range from the lower value lj to the reference value Ki and is greater than the lean angle shown in FIG. 5(a).

In FIG. 5(b), the illumination ranges LB and SHi tilt toward the lower left as compared with FIG. 5(a). The cut-off line LLi of the sub headlight light source l3La is adjacent to the horizon H at a location above the horizon H. Here, the sub headlight light source l3La lights up with a brightness lower than the brightness Qi and higher than the brightness in the State shown in FIG. 5(a) (FIG. 4).

[0099]

FIG. 5(c) is a diagram schematically showing a screen light distribution obtained when the lean angle ofthe motorcycle 10 takes the reference value Ki.

In FIG. 5(c), the illumination ranges LB and SHi tilt toward the lower left as compared with FIG. 5(b). The cut-offline LLi ofthe sub headlight light source l3La is located below the horizon H. The illumination range SHj of the sub headlight light source !3La is located in a space below the horizon H. Here, the sub headlight light source l3La lights up with the brightness Qi (FIG. 4).

[0100]

FIG. 6(a) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle 10 takes the upper value Ui.

In FIG. 6(a), the illumination ranges LB and SHi tilt toward the lower left as compared with FIG. 5(c). The cut-offline LLj ofthe sub headlight light source I3La is located below the horizon H while tilting toward the lower left. Here, the sub headlight light source l3La lights up with the brightness Q₂ (FIG. 4).

The cut-off line LLi obtained when the lean angle takes the reference value Ki (FIG. 5(c)) is closer to horizontal than the cut-off line LLi obtained when the lean angle takes the upper value Ui (FIG. 6(a)) and the cut-off line LLi obtained when the motorcycle 10 is in the upright state (FIG. 3). The same applies to the cut-off lines LL₂ and LL3, too, though not shown.

[010I]

FIG. 6(b) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle I0 takes a value that is in the range from the lower value T₂ to the reference value K₂.

In FIG. 6(b), the illumination ranges LB and SHi tilt toward the lower left as compared with FIG. 6(a). An illumination range SH₂ of the sub headlight light source l3Lb is located above the illumination range SHi. The cut-off line LL₂ of the sub headlight light source l3Lb is adjacent to the horizon H at a location above the horizon H. Here, the sub headlight light source l3Lb lights up with a brightness lower than the brightness Qi (FIG. 4).

[0102]

FIG. 6(c) is a diagram schematically showing a screen light distribution obtained when the lean angle ofthe motorcycle 10 takes the reference value K₂.

In FIG. 6(c), the illumination ranges LB, SHi, and SH₂ tilt toward the lower left as compared with FIG. 6(b). The cut-offline LL₂ of the sub headlight light source 13Lb is located below the horizon H. The illumination range SH₂ of the sub headlight light source 13Lb is located in a space below the horizon H. Here, the sub headlight light source 13Lb lights up with the brightness Qi (FIG. 4).

[0103]

FIG. 7(a) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle 10 takes a value that is in the range from the lower value T3 to the reference value K3.

In FIG. 7(a), the illumination ranges LB, SHi, and SH₂ tilt toward the lower left as compared with FIG. 6(c). An illumination range SH3 ofthe sub headlight light source 13Lc is located above the illumination range SH₂. The cut-offline LL3 ofthe sub headlight light source 13Lc is adjacent to the horizon H at a location above the horizon H. Here, the sub headlight light source 13Lc lights up with a brightness lower than the brightness Qi (FIG. 4).

[0104]

FIG. 7(b) is a diagram schematically showing a screen light distribution obtained when the lean angle of the motorcycle 10 takes the reference value K.3.

In FIG. 7(b), the illumination ranges LB, SHi to SH3 tilt toward the lower left as compared with FIG. 7(a). The cut-offline LL3 of the sub headlight light source 13Lc is located below the horizon H. The illumination range SH3 of the sub headlight light source 13Lc is located in a space below the horizon H. Here, the sub headlight light source 13Lc lights up with the brightness Q₂ (FIG. 4).

In the course ofan increase in the lean angle of the motorcycle 10 (FIGS. 5(a) to 7(b)), it is préférable that the illumination range SHi, SH₂, or SH3 of the sub headlight light source 13La, 13Lb, or 13Lc produced when the lean angle of the motorcycle 10 reaches the lower value Ti T₂, or T3 set for this sub headlight light source 13La, 13Lb, or 13Lc partially overlaps the illumination range LB or the illumination range SHi or SH₂ ofthe low beam light source I IL or the sub headlight light source 13La or 13Lb, that has been tumed on hnmediately before this sub headlight light source 13La, 13Lb, or 13Lc.

[0105]

Next, a change in an illumination range of the headlight in accordance with the lean angle of the motorcycle 10 will be described with reference to FIGS. 8 to 17. In FIGS. 8 to 17,

X represents a straight ahead direction of the motorcycle 10 that leans into tums, and Y represents the left side with respect to the width direction of the motorcycle 10. The reference numéral 80 dénotés a path of the motorcycle 10. The path 80 curves to the left, with a predetermined radius.

[0106]

FIG. 8 illustrâtes a light distribution, schematically showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle 10 takes a value that is în the range from the lower value Ti to the reference value Ki and is relatively close to the lower value Ti.

[0107]

The illumination range LB ofthe low beam light source 1 IL having an illuminance Li spreads ahead of the motorcycle 10 along the advancing direction X. Since the motorcycle 10 is inclined to the left, the cut-off line Lo of the low beam light source 1 IL approaches to the motorcycle 10 from the left side of the motorcycle 10. Accordingly, on the path 80, only a région relatively close to the motorcycle 10 is covered by the illumination range having the illuminance Li.

In running, the rider normally looks at a position on the path 80 ahead of the motorcycle 10. Therefore, the cut-off line Lo approaching to the motorcycle 10 enters the rider’s field of view.

[0108]

On the other hand, the sub headlight light source 13La produces illumination along the optical axis ALi. Therefore, on the path 80, the illumination range SHi of the sub headlight light source 13La covers the cut-off line Lo of the low beam light source 1 IL. Accordingly, the movement ofthe cut-off line Lo ofthe low beam light source 1 IL within the rider’s field of view is less likely to be conspicuous. Moreover, the cut-off line LL, of the sub headlight light source l3La is located at a relatively farther position ahead of the motorcycle 10. In a state shown in FIG. 8, the cut-off line LLi îs less clear than the cut-off line Lo.

Moreover, a région on the path 80 covered by the illumination range having the illuminance Li is elongated. The illumination range SHi of the sub headlight light source 13La spreads over a position the rider désirés to see.

[0109]

FIG. 9 illustrâtes a light distribution, schematically showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle 10 takes a value that is in the range from the lower value Ti to the reference value Ki and is greater than the lean angle shown in FIG. 8.

[0110]

In a state shown in FIG. 9, the lean angle of the motorcycle 10 increases as compared with the State shown in FIG. 8. Therefore, the cut-off line Lo of the low beam light source 1 IL further approaches to the motorcycle 10 as compared with the State shown in FIG. 8. Accordingly, the région on the path 80 covered by the illumination range LB of the low beam light source 1 IL having the illuminance Li is shortened.

[OUI]

On the other hand, the brightness of the sub headlight light source 13La increases in accordance with the increase in the lean angle, and therefore the illumination range SHj is enlarged. As a resuit, the illumination range SH] of the sub headlight light source 13La still covers the cut-off line Lo of the low beam light source 1 IL on the path 80. Accordingly, the movement of the cut-off line Lo of the low beam light source 11L within the rider’s field of view is less likely to be conspicuous. Moreover, the cut-off line LLi of the sub headlight light source 13La is located at a relatively farther position ahead ofthe motorcycle 10. In the State shown in FIG. 9, the cut-off line LLi is less clear than the cut-off line Lo.

In the State shown in FIG. 9, the lean angle increases as compared with the state shown in FIG. 8, but the brightness ofthe sub headlight light source 13La increases so that a région on the path 80 covered by the illumination range having the illuminance Li is ensured to the same extent as in the state shown in FIG. 8. As a resuit, the illumination range SHi of the sub headlight light source 13La spreads over the position the rider desires to see (on the path 80).

[0112]

FIG. 10 illustrâtes a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle 10 takes the reference value K|.

[0113]

In a state shown in FIG. 10, the lean angle of the motorcycle 10 increases as compared with the state shown in FIG. 9. Therefore, the cut-off line Lo of the low beam light source 11L further approaches to the motorcycle 10 as compared with the state shown in FIG. 9. Accordingly, the région on the path 80 covered by the illumination range LB of the low beam light source 11L having the il luminance Li is further shortened.

[0H4]

On the other hand, the sub headlight light source 13La is lighting up with the first brightness Qi, and the brightness of the sub headlight light source 13La increases in accordance with the increase în the lean angle. Therefore, the illumination range SHi is enlarged. As a resuit, the illumination range SHi of the sub headlight light source 13La still covers the cut-off line Lo of the low beam light source 1 IL on the path 80. Accordingly, the movement of the cutoff line Lo of the low beam light source 1 IL within the rider’s field of view is less likely to be conspicuous.

In the state shown in FIG. 10, the lean angle increases as compared with the state shown in FIG. 9, but the brightness of the sub headlight light source l3La increases so that a région on the path 80 covered by the illumination range having the illuminance Li is ensured to the same extent as in the State shown in FIG. 9. As a resuit, the illumination range SHi ofthe sub headlight light source l3La spreads over the position the rider desires to see (on the path 80). The cut-off line LLi of the sub headlight light source 13La is located at the side (X side) of the illumination range SHi to which the motorcycle 10 is advancing. The cut-off line LLi extends right and left along the width direction of the vehicle (Y direction).

[0H5]

FIG. Il illustrâtes a light distribution, schematically showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle 10 takes the upper value Uj. In this embodiment, the lower value T2 is less than the upper value Uj. Therefore, when the lean angle of the motorcycle IO takes the upper value Uj, the sub headlight light source l3Lb has already started to light up. However, the illumination range SH2 ofthe sub headlight light source l3Lb is not shown in FIG. 11.

[0H6]

In a State shown in FIG. 11, the lean angle of the motorcycle IO increases as compared with the State shown in FIG. I0. Therefore, the cut-off line Lo of the low beam light source 11L further approaches to the motorcycle IO as compared with the State shown in FIG. I0. In addition, the cut-off line LLi of the sub headlight light source l3La also approaches to the motorcycle I0 from the left side of the motorcycle IO.

[0H7]

On the other hand, while the lean angle is increasing from the reference value Ki to the upper value Ui, the brightness of the sub headlight light source l3La is increasing from the first brightness Qi to the second brightness Q2. Therefore, the illumination range SHi of the sub headlight light source l3La is enlarged. In FIG. 11, a région SHi’ enclosed by the broken line indicates an illumination range of the sub headlight light source l3La obtained when the sub headlight light source l3La lights up with the first brightness Qi. The illumination range SHi ofthe sub headlight light source l3La is larger than the région SHi’ enclosed by the broken line.

[0H8]

Thus, in the motorcycle IO, when the lean angle increases from the reference value Ki to the upper value Uj, the cut-off line LLi of the sub headlight light source !3La approaches to the motorcycle IO along with the increase in the lean angle, but the illumination range SHi is enlarged în accordance with the increase in the brightness of the sub headlight light source l3La from the first brightness Qi to the second brightness Q2. Thereby, the speed of approach ofthe cut-off line LLi to the motorcycle IO can be reduced.

[0119]

FIG. 12 illustrâtes a light distribution, schematically showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle 10 takes a value that is in the range from the lower value T₂ to the reference value K2.

[0120]

In a state shown in FIG. 12, the lean angle of the motorcycle IO increases as compared with the state shown in FIG. 11. Therefore, the cut-off line LL] of the sub headlight light source !3La further approaches to the motorcycle IO as compared with the state shown in FIG. H. Accordingly, a région on the path 80 covered by the illumination ranges LB and SHi is shortened.

[0I21]

On the other hand, the sub headlight light source l3Lb produces illumination along the optical axis AL2. Therefore, on the path 80, the illumination range SH₂ of the sub headlight light source l3Lb covers the cut-off line LLi of the sub headlight light source l3La. Accordingly, the movement of the cut-off line LLi of the sub headlight light source l3La within the rider’s field of view is less likely to be conspicuous. Moreover, the cut-off line LL₂ of the sub headlight light source l3Lb is located at a relatively farther position ahead ofthe motorcycle

IO. In the state shown in FIG. 12, the cut-off line LL₂ is less clear than the cut-off line LLi.

Moreover, a région on the path 80 covered by the illumination range having the illuminance Li is elongated. The illumination range SH₂ of the sub headlight light source l3Lb spreads over the position the rider desires to see.

[0122]

FIG. 13 illustrâtes a light distribution, schematically showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle IO takes the reference value K₂.

[0123]

In a state shown in FIG. 13, the lean angle ofthe motorcycle IO increases as compared with the state shown in FIG. I2. Therefore, the cut-off line LLi of the sub headlight light source l3La further approaches to the motorcycle IO as compared with the state shown in FIG. 12. Accordingly, the région covered by the illumination range SHi of the sub headlight light source !3La having the illuminance Li is further shortened.

[0124]

On the other hand, the sub headlight light source l3Lb is lighting up with the first brightness Qi, and the brightness of the sub headlight light source l3Lb increases along with the increase in the lean angle. Therefore, the illumination range SH₂ is enlarged. As a resuit, the illumination range SH₂ ofthe sub headlight light source l3Lb still covers the cut-off line LLi of the sub headlight light source l3La on the path 80. Accordingly, the movement of the cut-off line LLi of the sub headlight light source l3La within the rider’s field of view is less likely to be conspicuous.

In the state shown in FIG. 13, the lean angle increases as compared with the state shown in FIG. 12, but the brightness of the sub headlight light source l3Lb increases so that a région on the path 80 covered by the illumination range having the illuminance Li is ensured to the same extent as in the state shown in FIG. 12. As a resuit, the illumination range SH₂ of the sub headlight light source l3Lb spreads over the position the rider desires to see (on the path 80). The cut-off line LLi of the sub headlight light source !3Lb is located at the side (X side) of the illumination range SH₂ to which the motorcycle I0 is advancing. The cut-off line LL₂ extends right and left along the width direction of the vehicle (Y direction).

[0I25]

FIG. I4 illustrâtes a light distribution, schematicaiiy showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle 10 takes the upper value U₂. In this embodiment, the lower value T3 is less than the upper value U2. Therefore, when the lean angle of the motorcycle 10 takes the upper value LJ₂, the sub headlight light source l3Lc has already started to light up. However, the illumination range SHa ofthe sub headlight light source !3Lc is not shown in FIG. 14.

[0126]

In a state shown in FIG. 14, the lean angle of the motorcycle 10 increases as compared with the state shown in FIG. 13. Therefore, the cut-off line LLi of the sub headlight light source 13La further approaches to the motorcycle 10 as compared with the state shown in FIG.

13. The cut-off line LL₂ of the sub headlight light source 13Lb also approaches to the motorcycle 10 from the left side of the motorcycle 10.

[0127]

On the other hand, while the lean angle is increasing from the reference value K₂ to the upper value U2, the brightness of the sub headlight light source 13Lb is increasing from the first brightness Qi to the second brightness Q2. Therefore, the illumination range SH2 of the sub headlight light source 13Lb is enlarged. In FIG. 14, a région SH₂’ enclosed by the broken line indicates an illumination range of the sub headlight light source 13Lb obtained when the sub headlight light source 13Lb lights up with the first brightness Qi. The illumination range SH2 of the sub headlight light source 13Lb is larger than the région SH2’ enclosed by the broken line.

[0128]

Thus, in the motorcycle 10, when the lean angle increases from the reference value K.2 to the upper value U₂, the cut-off line LL2 of the sub headlight light source 13Lb approaches to the motorcycle 10 along with the increase in the lean angle, but the illumination range SH2 is enlarged along with the increase in the brightness ofthe sub headlight light source 13Lb from the first brightness Qi to the second brightness Q₂. Thereby, the speed of approach of the cut-off line LL2 to the motorcycle 10 can be reduced.

[0129]

FIG. 15 illustrâtes a light distribution, schematically showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle 10 takes a value that is in the range from the lower value T3 to the reference value K3.

[0130]

In a state shown in FIG. 15, the lean angle of the motorcycle 10 increases as compared with the state shown in FIG. 14. Therefore, the cut-off line LL2 of the sub headlight light source 13Lb further approaches to the motorcycle 10 as compared with the state shown in FIG.

14. Accordingly, a région on the path 80 covered by the illumination ranges LB, SHi, and SH2 is shortened.

[0131]

On the other hand, the sub headlight light source 13Lc produces illumination along the optical axis AL3. Therefore, on the path 80, the illumination range SH3 of the sub headlight light source 13Lc covers the cut-off line LL? of the sub headlight light source 13Lb. Accordingly, the movement of the cut-off line LL2 of the sub headlight light source 13Lb within the rider’s field of view is less likely to be conspicuous.

Moreover, a région on the path 80 covered by the illumination range having the illuminance Li is elongated. The illumination range SH3 of the sub headlight light source 13Lc spreads over the position the rider desires to see.

[0132]

FIG. 16 illustrâtes a light distribution, schematically showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle 10 takes the reference value K3.

[0133]

In a state shown in FIG. 16, the lean angle of the motorcycle 10 increases as compared with the state shown in FIG. 15. Therefore, the cut-off line LL? of the sub headlight light source 13Lb further approaches to the motorcycle 10 as compared with the state shown in FIG.

15. Accordingly, the région covered by the illumination range SH2 of the sub headlight light source 13Lb having the illuminance Li is further shortened.

[0134]

On the other hand, the sub headlight light source 13Lc is lighting up with the first brightness Qi, and the brightness ofthe sub headlight light source 13Lc increases along with the increase in the lean angle. Therefore, the illumination range SH3 is eniarged. As a resuit, the illumination range SH3 of the sub headlight light source 13Lc still covers the cut-off line LL2 of the sub headlight light source 13Lb on the path 80. Accordingly, the movement ofthe cut-off line LL2 ofthe sub headlight light source 13Lb within the rider’s field of view is less likely to be conspicuous.

In the state shown in FIG. 16, the lean angle increases as compared with the state shown in FIG. 15, but the brightness of the sub headlight light source l3Lc increases so that a région on the path 80 covered by the illumination range having the illuminance Li is ensured to the same extent as in the state shown in FIG. 15. As a resuit, the illumination range SH3 of the sub headlight light source l3Lc spreads over the position the rider desires to see (on the path 80). The cut-off line LL3 of the sub headlight light source l3Lc is located at the side (X side) ofthe illumination range SH3 to which the motorcycle 10 is advancing. The cut-off line LL3 extends right and left along the width direction of the vehicle (Y direction).

£0135]

FIG. 17 illustrâtes a light distribution, schematîcally showing an illumination range of the headlight produced on a road surface at a time when the lean angle of the motorcycle 10 takes the upper value U3.

[0136]

In a state shown in FIG. 17, the lean angle of the motorcycle 10 increases as compared with the state shown in FIG. I6. Therefore, the cut-off line LL2 of the sub headlight light source l3Lb further approaches to the motorcycle 10 as compared with the state shown in FIG.

16. The cut-off line LL3 of the sub headlight light source l3Lc also approaches to the motorcycle 10 from the left side of the motorcycle I0.

£0137]

On the other hand, while the lean angle is increasing from the reference value K₃ to the upper value U3, the brightness of the sub headlight light source l3Lc is increasing from the first brightness Qi to the second brightness Q2. Therefore, the illumination range SH3 of the sub headlight light source !3Lc is enlarged. In FIG. 17, a région SH3’ enclosed by the broken line indicates an illumination range of the sub headlight light source !3Lc obtained when the sub headlight light source l3Lc lights up with the first brightness Qi. The illumination range SH3 ofthe sub headlight light source !3Lc is larger than the région SH3’ enclosed by the broken line.

£0138]

Thus, in the motorcycle 10, when the lean angle increases from the reference value K3 to the upper value U3, the cut-off line LL₃ of the sub headlight light source l3Lc approaches to the motorcycle 10 along with the increase in the lean angle, but the illumination range SH3 is enlarged along with the increase in the brightness ofthe sub headlight light source l3Lc from the first brightness Qi to the second brightness Q₂. Thereby, the speed of approach of the cut-off line LL3 to the motorcycle 10 can be reduced.

£0139]

FIG. 18 is a diagram showing the relationship between the lean angle of the motorcycle 10 and an illumination distance of the headlight illuminating the path of the motorcycle 10 according to the first embodiment of the present invention. The points P8 to PI7 correspond to situations shown in FIGS. 8 to 17, respectively.

[0140]

As the motorcycle 10 is inclined to the left so that the lean angle increases from 0°, the cut-off line Lo of the low beam light source l IL approaches to the motorcycle 10 from the left side of the motorcycle I0. Therefore, a path irradiation range (which means a distance on the path 80 from the motorcycle 10 to the most distal end of the illumination range) becomes shorter along with the increase in the lean angle. Then, when the lean angle exceeds the lower value Ti, the sub headlight light source l3La is tumed on so that the illumination range SHi of the sub headlight light source 13La is produced (P8). This extends the path irradiation range. Then, along with the increase in the lean angle, the brightness of the sub headlight light source l3La increases to enlarge the illumination range SHi, thus extending the path irradiation range (P9 to PIO).

[0141]

After the lean angle reaches the reference value Ki (PIO), the cut-off line LLi of the sub headlight light source l3La approaches to the motorcycle 10 along with the increase in the lean angle. On the other hand, the brightness of the sub headlight light source l3La increases from the first brightness Qi to the second brightness Q₂, to enlarge the illumination range SHi. As a resuit, the speed of movement of the cut-off line LLi to the motorcycle 10 drops, which suppresses a réduction in the path irradiation range along with the increase in the lean angle (PU).

[0142]

When the lean angle further increases, the sub headlight light source 13Lb is tumed on so that the illumination range SH₂ of the sub headlight light source 13Lb is produced. Then, along with the increase in the lean angle, the brightness of the sub headlight light source 13Lb increases to enlarge the illumination range SH₂, thus extending the path irradiation range (Pl2).

[0143]

After the lean angle reaches the reference value K₂ (P13), the cut-off line LL₂ of the sub headlight light source 13Lb approaches to the motorcycle 10 along with the increase in the lean angle. On the other hand, the brightness of the sub headlight light source 13Lb increases from the first brightness Qi to the second brightness Q₂, to enlarge the illumination range SH₂. As a resuit, the speed of movement of the cut-off line LL₂ to the motorcycle 10 drops, which suppresses a réduction in the path irradiation range along with the increase in the lean angle (P14).

[0144]

When the lean angle further increases. the sub headlight light source 13Lc is tumed on so that the illumination range SHj of the sub headlight light source 13Lc is produced. Then, along with the increase in the lean angle, the brightness of the sub headlight light source 13Lc increases to enlarge the illumination range SH3, thus extending the path irradiation range (P 15).

[0l45]

After the lean angle reaches the reference value K3 (PI 6), the cut-off line LL3 ofthe sub headiight light source l3Lc approaches to the motorcycle IO along with the increase in the lean angle. On the other hand, the brightness of the sub headiight light source I3Lc increases from the first brightness Qi to the second brightness Q2, to enlarge the illumination range SH3. As a resuit, the speed of movement of the cut-off line LL3 to the motorcycle IO drops, which suppresses a réduction in the path irradiation range along with the increase in the lean angle (Pl7).

[0146] <Second Embodiment>

In the case îllustrated in the above-described first embodiment, when the lean angle reaches the reference value K (Kj to K3), the sub headiight light source lights up with the first brightness Qi, and when the lean angle is shifting from the reference value K (Kj to K3) to the upper value U (Ui to U3), the brightness of the sub headiight light source changes from the first brightness Qi to the second brightness Q2. However, the présent invention is not limited to this example. For exampie, a second embodiment is adoptable.

[0147]

FIG. 19 Îs a chart showing the relationship between the lean angle of the motorcycle IO and the brightnesses of the sub headiight light sources l3La to l3Lc according to the second embodiment of the présent invention.

[0148]

In the motorcycle IO according to the second embodiment of the présent invention, the upper value U (Ui to U3) is not set. In the motorcycle IO according to the second embodiment. as shown in FIG. 19, when the lean angle of the motorcycle IO reaches the lower value T (Ti to T3), the sub headiight light source 13 (l3La to l3Lc) starts to light up, and the brightness ofthe sub headiight light source 13 (l3La to l3Lc) gradually increases in accordance with an increase in the lean angle. When the lean angle of the motorcycle IO takes the reference value K (Ki to K3), the sub headiight light source 13 (13La to 13Lc) lights up with the second brightness Q2.

When the lean angle is equal to or greater than the reference value K (Ki to K3), the sub headiight light source 13 (13La to !3Lc) lights up in the same manner as in the first embodiment (FIG. 4), except that, at a time point when the lean angle takes the reference value K, the sub headiight light source 13 (13La to 13Lc) lights up with the second brightness Q₂. Therefore, a description ofthe manner will be omitted.

[0149]

FIG. 20 is a diagram showing the relationship between the lean angle of the motorcycle 10 and the illumination distance of the headiight illuminating the path of the motorcycle 10 according to the second embodiment of the présent invention. The points P8, P9,

PIO, Pl2, P13, Pl5, and Pl6 correspond to situations shown in FIGS. 8, 9, 10, 12, 13, 15, and 16, respectively.

[0150]

As the motorcycle 10 is inclined to the left so that the lean angle increases from 0°, the cut-off line Lo ofthe low beam light source l IL approaches to the motorcycle 10 from the left side ofthe motorcycle 10. Therefore, the path irradiation range becomes shorter along with the increase in the lean angle. Then, when the lean angle exceeds the lower value Ti, the sub headlight light source l3La is tumed on so that the illumination range SHi ofthe sub headlight light source l3La is produced (P8). This extends the path irradiation range. Then, along with the increase in the lean angle, the brightness ofthe sub headlight light source l3La increases to enlarge the illumination range SHi, thus extending the path irradiation range (P9). When the lean angle reaches the reference value Ki, the sub headlight light source l3La lights up with the second brightness Q₂ (PIO).

[0151]

After the lean angle reaches the reference value Ki, the cut-off line LLj of the sub headlight light source l3La approaches to the motorcycle 10 along with the increase in the lean angle. On the other hand, when the lean angle reaches the lower value T₂, the sub headlight light source l3Lb is tumed on so that the illumination range SH₂ of the sub headlight light source l3Lb is produced. Then, along with the increase in the lean angle, the brightness of the sub headlight light source l3Lb increases to enlarge the illumination range SH₂, thus extending the path irradiation range (P 12). When the lean angle reaches the reference value K₂, the sub headlight light source 13Lb lights up with the second brightness Q₂ (PI3).

[0152]

After the lean angle reaches the reference value K₂, the cut-off line LL₂ of the sub headlight light source 13Lb approaches to the motorcycle 10 along with the increase in the lean angle. On the other hand, when the lean angle reaches the lower value Tj, the sub headlight light source 13Lc is tumed on so that the illumination range SHj of the sub headlight light source 13Lc îs produced. Then, along with the increase in the lean angle, the brightness of the sub headlight light source 13Lc increases to enlarge the illumination range SH3, thus extending the path irradiation range (P 15). When the lean angle reaches the reference value K3, the sub headlight light source 13Lc lights up with the second brightness Q₂ (PI6).

[0153]

As thus far described, in the motorcycle 10, at a time point when the lean angle reaches the lower value T, the sub headlight light source 13La to 13Lc lights up with a brightness lower than the first brightness Qi (the second brightness Q₂ in the second embodiment), and when the lean angle reaches the reference value K, the sub headlight light source 13La to 13Lc lights up with the first brightness Qi (the second brightness Q₂ în the second embodiment). Accordingly, when the illumination range of the low beam light source l IL or the sub headlight light source l3La or l3Lb that has been aiready tumed on is moving away from the position the rider desires to see, the illumination range of the sub headlight light source !3La to l3Lc that is subsequently tumed on can spread over the position the rider desires to see. As a resuit, the cut-off line LLi to LL3 of the sub headlight light source l3La to l3Lc that is subsequently tumed on is likely to be conspicuous. The illumination range of the sub headlight light source l3La to l3Lc that is subsequently tumed on is enlarged along with an increase in the brightness. Therefore, an effect of reducing the speed of approach of the cut-off line LLi to LL3 to the motorcycle IO is exerted. This enables suppression of an uncomfortable feeling, which may otherwise be given to the rider.

Since a réduction in the illumination ranges of the sub headlight light sources l3La to l3Lc is suppressed, occurrence of a time period during which the position the rider desires to see is not sufficiently covered by the illumination ranges SHi to SH3 of the headlight can be suppressed. This enables suppression of an uncomfortable feeling, which may otherwise be given to the rider.

Moreover, when the lean angle is in the range between the lower value T (Ti to T3) and the reference value K (Ki to K3), the sub headlight light source !3La to l3Lc lights up with a brightness lower than the first brightness Qi(the second brightness Q2 in the second embodiment), and when the lean angle subsequently reaches the reference value K (Ki to K3), the sub headlight light source l3La to l3Lc lights up with the first brightness Qi (the second brightness Q2 in the second embodiment). This enables suppression of occurrence of a situation where the sub headlight light sources l3La to l3Lc suddenly lights up with a high brightness, which may make the rider feel uncomfortable.

[0153]

In the motorcycle IO according to these embodiments, the sub headlight 13 is composed of the sub headlight units 13L and 13R, each of which is provided at each side with respect to the width direction of the vehicle. However, the present invention is not limited to this example. For example, in a possible configuration, the sub headlight units 13L and 13R each provided at each side with respect to the width direction of the vehicle are formed integra! with each other, as a single sub headlight unit. In this case, the single sub headlight unit has, at each side thereof with respect to the width direction of the vehicle, a plurality of headlight light sources that generate illumination ranges at one side with respect to the width direction of the vehicle.

[0155]

These embodiments describe a case where each ofthe sub headlight units 13L and 13R is a physically integrated unit. However, the present invention is not limited to this example. It may be possible that the sub headlight unit I3L is physically divided into the sub headlight light sources 13La to l3Lc. In this case, it may be possible that these sub headlight light sources l3La to 13Lc are assembled into a single sub headlight unit 13L which is then installed in the motorcycle IO (vehicle). It may be also possible that each of the sub headlight light sources l3La to l3Lc is individually installed in the motorcycle 10. In this case, the sub headlight light sources l3Lato !3Lc, in a state of being installed in the motorcycle IO, constitute a single sub headlight unît 13L.

[0156]

In these embodiments, the sub headlight units 13L and 13R are members separate from the main headlight 11, However, the present invention is not lîmited to this example. It may be acceptable that a sub headlight unit is integrated with a main headlight.

[0157]

The lean angle sensor 22 and the vehicle speed sensor 23 correspond to a détection part for detecting variables available for obtaining the lean angle of the motorcycle 10. Although the détection part includes the lean angle sensor 22 and the vehicle speed sensor 23 in these embodiments, the present invention is not limited to this example. For example, the détection part may include the lean angle sensor 22 while not including the vehicle speed sensor 23. The controller 20 corresponds to a control part of the present invention. However, a hardware configuration of the present invention is not limited to this example. The control part détermines whether or not the lean angle of the motorcycle 10 has reached the reference value based on the variables detected by the détection part. At this time, it is not always necessary that the control part calculâtes the lean angle. No particular limitation is put on details of processing performed in the control part. For example, it may be possible that a memory provided in the controller 20 serving as the control part stores, in the form of data, a table in which the angular veloclty (roll rate) and the vehicle speed are associated with a resuit of whether or not the lean angle has reached a first reference value. In this case, the control part refers to the table based on the angular velocity and the vehicle speed, and thereby can détermine whether or not the lean angle has reached the first reference value without calculating the lean angle.

[0158]

In these embodiments, the lean angle is the angle of inclination of the vehicle body to the inner side of a curve relative to the upright state (vertical direction). However, the present invention is not limited to this example. The lean angle may be the angle of inclination of the vehicle body to the inner side of a curve relative to a direction perpendîcular to a road surface. As a method and a device for measuring the angle of Inclination of the vehicle body to the inner side of a curve relative to the direction perpendicular to the road surface, conventionally known ones are adoptable.

[0159]

These embodiments describe a case where the sub headlight units 13L and 13R are members separate from the control part (controller 20) and the détection part (the lean angle sensor 22 and the vehicle speed sensor 23). However, the présent invention is not limited to this example. The sub headlight unit may include at least one of the control part, the communication part, and the détection part.

[0160]

In these embodiments, three sub headlight light sources are provided at each side ofthe vehicle with respect to the width direction of the vehicle. In the présent invention, however, no particular limitation is put on the number of light sources. It is préférable that the number of sub headlight light sources that illuminate one side of the vehicle with respect to the width direction of the vehicle is at least three.

[0161]

In these embodiments, each of the sub headlight light sources and the low beam light source is constituted of one light source, and one reference value is set for this one light source. However, in the présent invention, the number of light sources that constitute one sub headlight light source or the low beam light source is not particularly limited. For example, it may be acceptable that one sub headlight light source or the low beam light source is constituted of a plurality of light sources and one reference value is set for the plurality of light sources.

[0162]

These embodiments describe a case where the reference value used when the lean angle increases so that the brightness of the sub headlight light source increases is the same as the reference value used when the lean angle decreases so that the brightness of the sub headlight light source decreases. Instead. these reference values may be different from each other.

[0163]

These embodiments describe a case where the sub headlight light source is tumed on in accordance with the lean angle. However, the présent invention is not limited to this example. The sub headlight light source may be configured such that a tum-on fonction in accordance with the lean angle is manually activated or deactivated. To be spécifie, it may be possible that the fonction is manually put into a standby state and, in the standby state, the sub headlight light source is tumed on in accordance with the lean angle. In this case as well, the sub headlight light source is tumed on not manually but in accordance with the lean angle. In the flasher, on the other hand, flashing/tum-off is manually switched. Also, in the main headlight, the illuminating direction is manually switched. In this manner, the sub headlight light source is different from the flasher and the main headlight.

The sub headlight light source may be also configured such that an instruction for tumon or turn-off is manually inputted. In such a case, when the instruction ts not inputted, the brightness of the sub headlight light source is changed in accordance with the lean angle, while when the instruction is inputted, tum-on or tum-off is performed in accordance with the instruction. For example, when the instruction for tum-on is inputted, the sub headlight light source is tumed on irrespective of the lean angle. When the instruction for tum-off is inputted, the sub headlight light source is tumed off irrespective of the lean angle. In such a case, the sub headlight system includes an input part (for example, a switch) to which the instruction for tuming on or off the sub headlight light source is manually inputted. When the instruction is inputted, the control part tums on or off the sub headlight light source in accordance with the instruction. When the instruction is not inputted, the control part changes the brightness of the sub headlight light source in accordance with the lean angle. In this case as well, the sub headlight light source is different from the flasher and the main headlight, in that a function of tuming on the sub headlight light source in accordance with the lean angle is provided.

The sub headlight light source may be configured such that, when the lean angle is equal to or larger than a minimum reference value, the brightness is changed in accordance with the lean angle, while when the lean angle is less than the minimum reference value (for example, at a time of running straight ahead), the brightness is manually changed. In this case as well, the sub headlight light source is different from the flasher and the main headlight, in that a function of tuming on the sub headlight light source in accordance with the lean angle is provided.

[0164]

In the description of this embodiment, the sub headlight light source is tumed on in accordance with the lean angle. Here, the sub headlight light source is tumed on în accordance with the lean angle because the sub headlight light source functions mainly as a light for ensuring the field of view of the rider of the vehicle. Therefore, in a well-lit situation, for example, in daytime, the sub headlight light source may not necessarily be tumed on in accordance with the lean angle.

[0165]

The above embodiments descrîbe a case where the voltage detector for detecting the supply voltage value of the voltage that is supplied to the sub headlight light source is provided. However, the present invention is not limited to this example. For example, a température detector for detecting the température of the sub headlight light source or the vicinity thereof may be provided.

In this case, the control part (controller) perforais such a control that the brightness of the sub headlight light source increases as the température detected by the température detector is higher. Alternatively, the control part may perform such a control that the brightness of the sub headlight light source increases in a case where the température detected by the température detector is equal to or higher than a predetermined température. This can correct a réduction in the brightness of the sub headlight light source caused by a température rîse.

[0l 66]

In the present invention, it may be possible that the control part performs a distance information acquisition process and an adjustment process. In the distance information acquisition process, distance information indicating a distance the vehicle has traveled is acquired from a tripmeter or the like. In the adjustment process, the brightness of the sub headlight light source, which changes in accordance with the lean angle of the vehicle, ts adjusted based on the distance information. In this case, the control part (controller) performs such a control that the brightness of the sub headlight light source increases as the distance the vehicle has traveled is longer. This can correct a réduction in the brightness of the sub headlight light source caused by a long-term use.

[0167]

Furthermore, in the present invention, it may be possible that the control part performs a time information acquisition process and an adjustment process. In the time information acquisition process, time information indicating a period of use of the vehicle or the sub headlight light source is acquired. In the adjustment process, the brightness of the sub headlight light source, which changes in accordance with the lean angle of the vehicle, is adjusted based on the time information acquired as a resuit of the time information acquisition process. In this case, the control part can acquire the time information based on information of the current time, which is obtained by a clock or the like, and information indicating the time and date when the use of the vehicle or the sub headlight light source was started, which is stored in the memory. It may be also possible that the vehicle is configured to acquire, through wireless communication, the time information indicating the period of use of the vehicle or the sub headlight light source from an extemal storage device (for example, a server) remote from the vehicle. In this case, the control part performs such a control that the brightness of the sub headlight light source increases as the period of use indicated by the time information is longer. This can correct a réduction in the brightness of the sub headlight light source caused by a long-term use.

[0168]

In the above-described example, the brightness of the sub headlight light source, which changes in accordance with the lean angle, is corrected based on the température, the travel distance, and the period of use. In the present invention, when the lean angle of the vehicle is in a range of at least the lower limit value and less than the reference value, such a correction (adjustment process) is performed, while when the lean angle of the vehicle is out of this range, such a correction is not performed. Accordingly, at a time of causing the sub headlight light source to light up with a high brightness, an output of the sub headlight light source can be made without limitation, to make it possible to ensure a wide illumination range. However, the present invention is not limited to this example. The above-described brightness control may be performed irrespective of the lean angle of the vehicle.

[ΟΙ 69] motorcycle (vehicle that leans into tums) main headlight

11H high beam light source

IL low beam light source handlebar sub headlight

I3L, 13R sub headlight unit

13La, 13Lb, 13Lc, I3Ra, 13Rb, 13Rc sub headlight light source

14L, 14R flasher operation switch front wheel frontfork front cover controller lean angle sensor vehicle speed sensor path

Claims (10)

1. CLAIMS [Claim 1J

   A sub headlight unit for use in a vehicle that leans into turns, wherein the sub headlight unit includes a sub headlight light source that illuminâtes, at one side with respect to a width direction of the vehicle, an area ahead and outward of the vehicle with respect to the width direction of the vehicle, the brightness of the sub headlight light source changes in accordance with a lean'angle ofthe vehicle, when the lean angle of the vehicle leaning to the one side with respect to the width direction of the vehicle reaches a reference value that is set for the sub headlight light source, the sub headlight light source lights up with a first brightness, and when the lean angle of the vehicle is equal to or greater than a lower value that is less than the reference value and less than the reference value, the sub headlight light source lights up with a brightness gradually increasing in a range lower than the first brightness according to the increase of the lean angle.
2. [Claim 2]

   The sub headlight unit according to claim 1, wherein when the lean angle of the vehicle reaches the lower value that is set for the sub headlight light source, an illumination range of the sub headlight light source contains a space above a horizontal line, when the lean angle of the vehicle reaches the reference value that is set for the sub headlight light source, the illumination range of the sub headlight light source is located in a space below the horizontal line.
3. [Claim 3]

   The sub headlight unit according to claim 1 or 2, wherein a cut-off line of the sub headlight light source obtained when the lean angle of the vehicfe reaches the reference value that is set for the sub headlight light source is doser to horizontal than the cut-off line of the sub headlight light source obtained when the lean angle of the vehicle reaches the lower value thaï is set for the sub headlight light source.
4. [Claim 4]

   The sub headlight unit according to claim 1 or 2, wherein the sub headlight light source comprises a plurality of the sub headlight light sources, the reference value and the lower value are individually set for each of the sub headlight light sources.
5. [Claim 5]

   The sub headlight unit according to claim 4, wherein the reference value of one sub headlight light source is equal to or smaller than the lower value of another sub headlight tight source for which the next greatest reference value after that of the one sub headlight light source is set.
6. [Claim 6]

   The sub headlight unit according to claim 1 or 2, wherein an optical axis of the sub headlight light source is fixed, the sub headlight light source whose optical axis is fixed lights up with the first brightness when the lean angle of the vehicle reaches the reference value that is set for the sub headlight light source, and lights up with a brightness lower than the first brightness in the period from when the lean angle of the vehicle reaches the lower value that is less than the reference value to when the lean angle of the vehicle reaches the reference value.
7. [Claim 7]

   A sub headlight system for use in a vehicle that leans into turns, the sub headlight system comprising:

   the sub headlight unit according to any one of daims 1 to 6;

   a control part that changes the brightness of the sub headlight light source in accordance with the lean angle of the vehicle; and a détection part that detects a variable available for obtaining the lean angle of the vehicle, wherein, when the lean angle of the vehide leaning to the one side with respect to the width direction of the vehicle reaches the reference value that is set for the sub headlight light source, the control part causes the sub headlight light source to light up with the first brightness, and în the period from when the lean angle of the vehicle reaches the lower value that is less than the reference value to when the lean angle of the vehicle reaches the reference value, the control part causes the sub headlight light source to light up with a brightness lower than the first brightness.
8. [Claim 8]

   The sub headlight system according to claim 7, wherein the sub headlight system includes a voltage detector that detects a supply voltage value of a voltage that is supplied from a battery provided in the vehicle to the sub headlight light source, the control part performs:

   a comparison process for comparing the supply voltage value detected by the voltage detector against a reference voltage value ofthe battery; and ' an adjustment process for adjusting, based on a resuit of the comparison, the brightness of the sub headlight light source that changes in accordance with the lean angle of the vehicle.
9. [Claim 9]

   The sub headlight system according to claim 8, wherein when the lean angle of the vehicle is in a range of at least the lower value and less than the reference value, the control part performs the adjustment process, while when the lean angle of the vehicle is out of the range, the control part does not perform the adjustment process.
10. [Claim 10]

    A vehicle that leans into turns, the vehicle comprising the system according to any one of claims 7 to 9,