JPH0790824B2 - Front and rear wheel steering system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front / rear wheel steering device for a vehicle, and more particularly to a front / rear wheel steering device for a vehicle that steers a single rear wheel in conjunction with front wheels.

(Prior Art) As a vehicle provided with a single rear wheel, for example, there is a motorcycle, in which the motorcycle is steered only by the front wheels, the rear wheels are supported by the vehicle body so as to be driven by an internal combustion engine, and steering is performed. You can't.

By the way, research and development has been conducted on a bicycle, in which not only the front wheels but also the rear wheels are steered in conjunction with the front wheels to improve straight running stability.

(Problems to be solved by the invention) Even in a vehicle having a single rear wheel such as a motorcycle, if the front wheel is steered by operating the steering wheel and the rear wheel is steered in conjunction with the front wheel, the vehicle goes straight. The stability can be improved. By the way, if the front wheels and the rear wheels are steered in conjunction with each other in this way, the rear wheels may be swayed in conjunction with each other if the rider inadvertently moves the steering wheel during braking. On the other hand, when an external force from the road surface acts on the rear wheels during braking, the rear wheels may sway, which may cause the steering wheel to sway and the running during braking to become unstable. On the other hand, traveling stability is required even during acceleration.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a front / rear wheel steering system for a vehicle, which ensures straightness of rear wheels during braking or acceleration and further improves running stability. Has an aim.

(Means for Solving the Problems) In order to solve the above problems, the present invention rotatably supports a single rear wheel on a rear arm pivotally supported by a vehicle body via a suspension. At the same time, the rear wheel is rotatably supported with a steering pivot fixed to the rear arm as a fulcrum, and the rear wheel is configured to be steered in conjunction with the front wheel. The turning center axis is inclined in the front-rear direction of the vehicle body, and the turning center axis intersects a vertical line passing through the ground contact point of the rear wheel.

(Operation) In this invention, when braking force is applied during braking, the load of the vehicle body is applied to the front wheel side, and the rear side of the vehicle body floats up and the suspension extends. For this reason, the rear side of the rear arm pivotally supported by the vehicle body descends relatively, the turning center axis of the rear wheels inclines rearward of the vehicle body, and the turning center axis passes through the grounding point of the rear wheels. Cross over against.

Therefore, if the rider inadvertently moves the steering wheel during braking, or conversely, braking causes an external force from the road surface to act on the rear wheels, causing the rear wheels to flutter and change direction to the left or right, The resistance pushes the surface of the tire back to the point of least resistance. For this reason, the rear wheel naturally keeps straightness while traveling, and the flutter is reduced.

On the other hand, even at the time of acceleration, the rear side of the vehicle body squeezes in due to the driving force transmitted from the internal combustion engine to the rear wheels, and the rear part of the rear arm is relatively lifted, so that the turning center axis of the rear wheels is inclined toward the front of the vehicle body This turning center axis intersects with a vertical line passing through the ground contact point of the rear wheel. Therefore, when the direction of the rear wheels is changed in conjunction with the front wheels, the driving force acts in the direction of the rear wheels that are turning, so steering performance is good and traveling stability during acceleration is further improved.

(Embodiment) An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

In the figure, reference numeral 1 is a vehicle body frame, and a steering pipe 3 is rotatably provided on a head pipe 2 of the vehicle body frame 1. A front fork 4 is supported on the steering shaft 3 via an upper bracket 5 and a lower bracket 6, and the front fork 4 turns around the steering shaft 3 as a fulcrum. A front wheel 7 is attached to the lower end of the front fork 4, and a handle 8 is attached to the upper end.

An internal combustion engine 11 is mounted between a main frame 9 extending rearward from the head pipe 2 and a pair of down tubes 10, and a fuel tank 12 is provided in the main frame 9 above the internal combustion engine 11. A seat 13 is mounted on a seat rail 14 behind the fuel tank 12, and the seat rail 14 is connected between a main frame 9 and a back stay 15 extending upward from the rear of the down tube 10.

Brackets behind the pair of down tubes 10
16 are provided, and a front end portion 18a of a rear arm 18 is swingably supported by a pivot shaft 17 provided between the brackets 16. Rear end 18b of rear arm 18 has suspension 1
It is supported by the back stay 15 via 9.

As shown in FIGS. 4 and 5, the rear arm 18 extends rearward on the left side, and a rear wheel 20 is cantilevered at a rear end portion 18b.

A support shaft 21 fixed to the rear end portion 18b of the rear arm 18 is rotatably provided with a vehicle body side rotation shaft 22 via a bearing 23, and a brake drum 25 of a drum brake 24 is provided outside the vehicle body side rotation shaft 22. It is provided so that it can rotate integrally. On the outside of this brake drum 25, a sprocket 26
The sprocket 26 is fixed by the sprocket 26 and is connected to the sprocket 30 provided on the drive shaft 29 of the internal combustion engine 11 via the chain 28 which is a winding type power transmission means. Internal combustion engine
11 drive force is drive shaft 29, sprocket 30, chain
It is transmitted to the vehicle body side rotation shaft 22 via the sprocket 26, the brake drum 25 and the sprocket 26.

A pair of brake shoes 31 are arranged in the brake drum 25, and the brake shoes 31 can be spread on a back plate 32 formed integrally with a support shaft 21 fixed to the rear arm 18. A cam shaft 33 for expanding the brake shoe 31 is rotatably provided on the back plate 32, and an operation lever 35 connected to the brake rod 34 is fixed to the cam shaft 33.

The front side of the brake rod 34 is engaged with the link 36 as shown in FIGS. 3 and 4. The link 36 is fixed to the left side of a rotating shaft 39 supported between brackets 37 and 38 fixed to the pair of down tubes 10. A coil spring 40 is wound around the right side of the rotating shaft 39. The coil spring 40 has a bracket 38 at one end 40a and a brake pedal at the other end 40b.
The brake pedal 41 is locked to 41 and always urges the brake pedal 41 to a predetermined position.

The vehicle body side knuckle arm 42 is fixed to the rear arm 18 with bolts 43. The upper arm 42a and the lower arm 42b of the vehicle body side knuckle arm 42 include the upper arm 44a and the lower arm 44 of the wheel side knuckle arm 44.
b is provided so as to be rotatable around the steering pivots 45 and 46 as fulcrums. The turning center axis P of the rear wheel 20 is set by the steering pivots 45 and 46.

As shown in FIG. 3, the turning center axis P of the rear wheel 20 causes a relative change in the angle of the rear arm 18 with respect to the road surface when the suspension 19 expands and contracts due to load fluctuations during acceleration and braking. Therefore, the turning center axis P1 at the time of acceleration tilts forward, and the turning center axis P2 at the time of braking tilts backward.

The wheel side knuckle arm 44 is fixed to a support shaft 47 by a bolt 48, and a wheel side rotation shaft 50 is rotatably provided on the support shaft 47 via a bearing 49. Wheel side rotating shaft
A hub 51 of the rear wheel 20 is provided at 50 so as to be integrally rotatable.

The vehicle body side rotating shaft 22 and the wheel side rotating shaft 50 are integrally rotatably connected by a universal joint 52. The pair of yoke portions 53 and 54 of the universal joint 52 are provided on the vehicle body side rotary shaft 22.
And the wheel-side rotating shaft 50 can be integrally rotated. Spiders 55 are provided between the opposing yoke portions 53 and 54, and the journals of the spider 55 are respectively arranged in the yoke portions.
By engaging with 53, 54, the rotational force of the vehicle body side rotating shaft 22 is transmitted to the wheel side rotating shaft 50.

A rear wheel side lever 56 is fixed to the support shaft 47, and the rear wheel side lever 56 is connected to a link 58 via an adjusting rod 57. The link 58 is a bracket 59 inside the rear arm 18.
Fixed to the lower end of the vertical rotating shaft 60 that is supported by
A link that crosses above the rear arm 18 is provided above the rotary shaft 60.
61 is fixed, and the rear end portion 62a of the operation wire 62 is connected to the end portion of this link 61 via a ball shaft.

The operation wire 62 extends to the front side along the rear arm 18, further extends to the lower side of the head pipe 2 through the left side of the internal combustion engine 11, and its front end portion 62b is connected to a support 63 fixed to the lower bracket 6. The operation wire 62 is supported by being fastened and fixed to both a bracket 64 provided on the rear arm 18 and a bracket 65 provided on the down tube 10 with both nuts.

The connection between the operation wire 62 and the support 63 is shown in FIGS.
It is configured as shown in the figure.

FIG. 6 is a bottom view of the head pipe portion, and FIG. 7 is FIG. 6 VII.
A VII sectional view is shown. The support 63 is fixed to the lower portion of the lower bracket 6 by screws 66 from above and bolts 67 from the front side. A front wheel side lever 68 is provided below the support 63, and an adjusting body 70 is slidably arranged in a guide groove 69 formed in the front wheel side lever 68. A ball shaft 71 is provided in the lower portion of the adjusting body 70, and the front end portion 62a of the operation wire 62 is supported by the ball shaft 71. An adjusting bolt 72 is inserted through the adjusting body 70, and the rotating of the adjusting bolt 72 causes the adjusting body 70 to screw on the shaft and move in the guide groove 69. A fixing bolt 73 is screwed onto the adjusting body 70, and when the fixing bolt 73 is tightened, the adjusting body 70 is fixed at a predetermined position. The length of the operation wire 62 is adjusted as the adjusting body 70 moves away from the steering shaft 3.
It is designed to be stretched.

The front wheel side levers 68 provided on the support 63 are arranged within the width D of the left and right front forks 4 in the vehicle width direction so that the front wheel side levers 68 do not come into contact with obstacles during traveling. Further, the front wheel side lever 68 does not interfere with an operation cable arranged around the head pipe 2.

The front wheel side lever 68 pulls or pushes the operation wire 62 according to the steering angle of the front wheel 7 by the operation of the handle 8, and moves the link 61 provided on the rotary shaft 60 of the rear arm 18 in the front-back direction as shown in FIG. Let By moving this link 61,
The rear wheel side lever 56 is operated via the link 58 and the adjustment rod 57 to rotate the rear wheel 20 with the steering pivot shafts 45 and 46 as fulcrums.
0 is turned according to the steering angle of the front wheels 7.

Next, the operation of this embodiment will be described.

The driving force of the internal combustion engine 11 is transmitted from the drive shaft 29 to the sprocket 26 of the rear wheel 20 via the chain 28, and the vehicle body side rotation shaft 22 is rotated via the brake drum 25 of the drum brake 24.

The rotating force of this vehicle body side rotating shaft 22 is a universal joint.
It is transmitted to the wheel-side rotary shaft 50 via 52, and the wheel-side rotary shaft 50 is transmitted.
The rear wheel 20 fixed to the vehicle is integrally rotated to travel.

In this traveling, for example, when the steering wheel 8 is operated to the right, the front fork 4 turns to the right around the steering shaft 3, whereby the front wheels 7 are steered to the right. By this operation of the handle 8, the front wheel side lever 68 of the support 63 also rotates in accordance with the steering angle of the front wheel 7, and pulls the operation wire 62. Therefore, the link 61 provided on the rotary shaft 60 of the rear arm 18 is pulled, the link 58 provided at the lower end of the rotary shaft 60 is rotated clockwise in FIG. 4, and the rear wheel side is moved through the adjusting rod 57. Pull the lever 56. Therefore, the rear wheels 20 rotate counterclockwise about the turning center axis P set by the steering pivots 45 and 46, and steer the rear wheels 20 to the position indicated by the imaginary line in conjunction with the front wheels.

When the steering wheel 8 is operated in the left direction, the operation wire 62 is pushed according to the steering angle of the front wheels 7, and the operation is performed in the opposite manner to rotate the rear wheels 20 in the clockwise direction with the steering pivots 45 and 46 as fulcrums. To steer. In this way, since the front wheels 7 and the rear wheels 20 turn in conjunction with each other, the wheel base extends and the center of gravity relatively moves forward, so that straight running stability against disturbance is improved.

During normal traveling, as shown in FIG. 8, the rear arm 18 is in a position substantially parallel to the road surface, and the intersection a1 between the turning center axis P of the rear wheel 20 and the road surface is the same as the ground contact point b1 of the rear wheel 20. I am doing it.

When the brake pedal 41 is stepped on as shown in FIG. 4 during this traveling, the brake rod 34 passes through the rotary shaft 39 and the link 36.
Is pulled and the operation lever 35 rotates clockwise in FIG. 3, and the brake shoe 31 of the drum brake 24 is moved to the cam shaft 33.
Then, the brake drum 25 is expanded and is pressed against the brake drum 25 that rotates integrally with the vehicle body side rotation shaft 22 to brake.

Due to this braking, the center of gravity of the vehicle body moves to the front side, and the rear portion of the vehicle body tends to lift, and the suspension 19 extends. As a result, the rear arm 18 floats up on the side of the pivot shaft 17, the steering pivot shafts 45 and 46 of the rear wheel 20 tilt rearward, and a steering tilt angle α is generated between the turning center axis P2 and the road surface.
Due to this angle α, the turning center axis P2 intersects the vertical line passing through the grounding point of the rear wheel 20. Thus, the front wheels 7 and the rear wheels 20
However, the rider may inadvertently move the steering wheel 8 during braking, or conversely, braking may cause external force from the road surface to act on the rear wheels 20, and the rear wheels 20 Even if you turn to the left or right due to frustration, the resistance of the road surface pushes the tire surface and pushes it back to the position with the least resistance. For this reason, the rear wheel 20 naturally keeps straightness during traveling, which reduces flutter and further improves straightness. On the other hand, when the grip provided on the right side of the handlebar 8 is operated to increase the output of the internal combustion engine 11 and accelerate it, a tensile force is generated in the chain 28 and the rear arm 18 is pulled upward, so that the suspension 19 is compressed. Lift up. In addition, the load applied to the rear wheel 20 increases due to the acceleration force, and the rear side of the vehicle body sinks. Therefore, the turning center axis P1 of the rear wheel 20 is inclined forward as shown in FIG. 3, the steering tilt angle α is generated behind the turning center axis P, and the turning center axis P1 is the contact point of the rear wheel 20. Crosses a vertical line passing through the point.

Therefore, when the front wheel 7 is operated and the rear wheel 20 is turned, the steering force is improved because the driving force acts on the rear wheel 20 in the direction of the wheel whose direction is changed, and the running stability during acceleration is further improved. improves.

In addition, although the motorcycle has been described in the above embodiment,
Various vehicles can be similarly implemented as long as they have a single rear wheel.

(Effects of the Invention) As described above, according to the present invention, the turning center axis of the rear wheel that is steered in conjunction with the front wheel is tilted in the longitudinal direction of the vehicle body during braking or acceleration, and the turning center axis is the rear wheel. Since it crosses the vertical line passing through the ground contact point of the vehicle, the rear wheels naturally keep straightness when braking while driving, which reduces flutter and improves straightness. At the same time, since the driving force acts in the direction of the rear wheels that turn when accelerating, the steering performance is good and the traveling stability during acceleration is further improved.

[Brief description of drawings]

FIG. 1 is a side view of a motorcycle to which the invention is applied, and FIG.
The drawing is a plan view of a motorcycle with a part cut away, FIG. 3 is a side view of a main part, FIG. 4 is a plan view of the main part, and FIG. 5 is a V of FIG.
-V sectional view, FIG. 6 is a bottom view near the head pipe, FIG.
FIG. 7 is a sectional view taken along line VII-VII of FIG. 6, and FIG. 8 is an explanatory view showing an operating state. 4 …… Front fork 7 …… Front wheel, 11 …… Internal combustion engine 18 …… Rear arm, 19 …… Suspension 20 …… Rear wheel, 22 …… Vehicle side rotating shaft 42 …… Vehicle side knuckle arm 44 …… Wheel side knuckle Arm 50 …… Wheel side rotating shaft 52 …… Universal joint 62 …… Operating wire, 64 …… Support 68 …… Front wheel side lever

Claims (1)

[Claims] 1. A single rear wheel is rotatably supported by a rear arm pivotally supported by a vehicle body through a suspension, and a rear pivot is fixed to a steering pivot that is fixed to the rear arm. Is supported so that it can turn, and the rear wheel is steered in conjunction with the front wheel.When braking or accelerating, the center axis of turning of the rear wheel is inclined in the longitudinal direction of the vehicle body, and the center axis of turning is A front / rear wheel steering system for a vehicle, characterized in that it crosses a vertical line passing through a ground contact point of the wheel.