JP2674785B2 - Front and rear wheel steering system for motorcycles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for steering both front and rear wheels of a motorcycle.

[Prior Art] Conventionally, in a motorcycle, only the front wheels are generally steered. However, in recent years, it has been considered to steer not only the front wheels but also the rear wheels in order to improve the running stability, especially during medium- and high-speed running. It has been experimentally confirmed that it is effective to steer the rear wheels in the same phase as the front wheels in order to improve the stability of medium and high speed running.

On the other hand, in a four-wheeled vehicle, as described in Japanese Patent Publication No. 60-44186, when the steering angle of the front wheels is within a predetermined range,
A steering method has been proposed in which the rear wheels are in-phase with the front wheels and the rear wheels are steered so that the ratio of the steering angle of the front wheels to the steering angle of the rear wheels changes.

In the above publication, the steering unit for controlling the steering angle of the rear wheels has a slide cam connected to the rear end of the first conductive member (reference numeral 1 in FIG. 1 of the publication) extending rearward from the steering device for the front wheels. Then, the movement amount of the cam follower arranged in the cam groove formed in the slide cam is transmitted to the second transmission member (reference numeral 5) to steer the left and right rear wheels.

[Problems to be solved by the invention]

As described above, when the transmission member is provided in front of the rear wheel steering unit, the number of connecting portions increases, and naturally there is a gap in the connecting portions, so that play is accumulated. Further, although a lever is interposed in the transmission member, the amount of movement of the lever and the rod connected to this rotation angle is not constant, which is not preferable when finely controlling the steering angle of the rear wheels.

In addition, the steering system of an automobile is located between the left and right wheels and is not located in the radial direction of the wheels, but it is difficult to remove it from the radial direction in a motorcycle, and the muddy water that winds up the wheels causes the flying stones to easily hit. Become.

In recent motorcycles, a steering shaft cylinder is provided in front of a front fork that supports the front wheel, and a steering shaft with a handle attached is inserted into it to connect the steering shaft and the front fork with a steering rod. There is a vehicle that steers the front wheels to secure a large luggage compartment inside the vehicle body cover above the front fork. It is an object of the present invention to provide a front and rear wheel steering device that does not impair the characteristics of the vehicle and does not cause a problem when mounting a rear wheel steering unit on such a vehicle.

[Means for solving the problem]

The present invention detects the steering angle of the front wheel 3 steered by the steering wheel 5, and when the steering angle is less than or equal to a predetermined angle, steers the rear wheel 18 in phase with the front wheel 3 and at a constant ratio to obtain a steering angle of a predetermined angle or more. In the case of, in the front and rear wheel steering device of the motorcycle, which is configured to hold the rear wheel 18 at the rear wheel steering angle at the predetermined angle, the front steering bracket 5b is attached to the lower portion of the steering shaft 5a, Below the front steering bracket 5b, a casing 9 composed of an upper case 9a and a lower case 9b of the rear wheel steering unit 8 is arranged, and the upper case 9a is a steering shaft tube which pivotally supports the steering shaft 5a. 2b and the vehicle body frame 2, fixed to the lower end of the steering shaft 5a inserted in the casing 9 is a fan-shaped drive gear 10, and a slide cam 11 is provided behind the drive gear 5a. The slide cam 11 includes a rectangular plate-shaped cam portion 11a having a slit-shaped cam groove 13 and Is arm portion 11a integrally formed rack portion 11b that meshes with the gear portion 10b of the drive gear 10
And a cam follower 15 arranged in the cam groove 13 configured to move in the front-rear direction by rotation of the steering shaft 5a.
Support shaft 15a of the above through the upper case 9a of the interlocking rod 1
In addition to being fixed to 5b, the interlocking rod 15b is axially supported by a guide member 16 fixed to the upper surface of the upper case 9a so as to be movable at right angles to the moving direction of the slide cam 11, and at the end of the interlocking rod 15b. One end of the transmission mechanism is connected, and the other end of the transmission mechanism is connected to the steering bracket 20 of the rear wheel 18 pivotally supported by the rear arm, and the moving amount of the cam follower 15 is changed to the rear wheel.
The feature is that it is transmitted to the 18 side to steer the rear wheels.

[Action]

In the present invention, the fan-shaped drive gear 10 fixed to the lower end of the steering shaft 5a and the rack portion 11b protruding laterally from the side edge of the cam portion 11a of the slide cam 11 to the drive gear 10 are meshed, Since the slide cam 11 is moved in the front-rear direction by the rotation of the steering shaft 5a, it is necessary to provide a conductive member including a rod and a lever on the front side of the slide cam 11 of the rear wheel steering unit 8 which is prone to rattling. However, since there is only a slight backlash between the drive gear 10 and the gear of the rack portion 11b, the amount of movement of the cam follower 15 arranged in the cam groove 13 of the slide cam 11 depends on the rotation angle of the steering handle 5. With high accuracy and in direct proportion, the steering angle of the rear wheels 18 can be finely and accurately controlled as a result.

Further, since the slide cam 11 is formed by integrally forming the rectangular plate-shaped cam portion 11a and the rack portion 11b protruding from the side edge of the rectangular cam portion to the side of the drive gear 10, the entire slide cam is formed. Can be compactly covered with a rectangular box-shaped casing 9.

Therefore, the rear wheel steering unit 8 does not break down due to muddy water splashed up by the front wheels 3 or hit by flying stones. The support shaft 15a of the cam follower 15 arranged in the cam groove 13 of the slide gum 11 penetrates the upper case 9a, and the interlocking rod 15b to which the support shaft 15a is fixed slides outside the casing 9a. Is disposed on the upper surface side of the casing 9a and the upper portion of the front wheel 3 is covered with the vehicle body cover, so that water or the like does not enter from above.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 to 4 are drawings for explaining a front and rear wheel steering system for a motorcycle according to a first embodiment of the present invention.

In the figure, 1 is a scooter type motorcycle to which the device of the present embodiment is adopted, and a front fork 4 which pivotally supports a front wheel 3 at its lower end is pivoted to the left and right at a front end portion of a body frame 2 thereof. It is supported. A steering shaft tube 2b is fixed to a bracket 2a extending forward from the body frame 2, and a steering shaft 5a fixed to a steering handle 5 is inserted in the steering shaft tube 2b. Has been done. A front steering bracket 5b extending outward in the vehicle width direction is fixed to the lower portion of the steering shaft 5a, and the front end of the steering rod 7 is attached to both ends of the bracket 5b via ball joints 6. Are connected. The rear end of the steering rod 7 is also connected to both ends of the rear steering bracket 4a via the ball joint 6, and the bracket 4a is fixed to the front fork 4. In this way, a front wheel steering device is configured that steers the front wheels 3 via the steering rod 7 when the steering handle 5 is rotated right and left.

A rear wheel steering unit 8 is mounted on the lower side of the front steering bracket 5b of the steering shaft 5a. The unit 8 is mainly composed of a casing 9, a drive gear 10, a slide cam 11 and master cylinders 12a and 12b.

The casing 9 is a rectangular box-shaped upper case 9a and lower case 9
The upper and lower parts of the upper case 9a are fixed to the lower end of the steering shaft tube 2b and the bracket 2a, respectively.

The drive gear 10 has a fan-like shape in which a base portion 10a and an arc-shaped gear portion 10b are integrally formed, and the base portion 10a is attached to the lower end of the steering shaft 5a inserted in the casing 9 by a bolt 1
It is fastened and fixed at 0c.

The slide cam 11 is formed by integrally forming a rod-shaped rack portion 11b at one end of a rectangular plate-shaped cam portion 11a.
A linear bearing 14 for linearly sliding the slide cam 11 in the front-rear direction is arranged between the lower case 9b and the lower case 9b.
The rack portion 11b meshes with the gear portion 10b of the drive gear 10, and the cam portion 11a has a slit formed by connecting front and rear straight groove portions 13a and 13b extending in the vehicle front-rear direction with inclined groove portions 13c. The cam groove 13 is formed.

A cam follower 15 is arranged in the cam groove 13, and the support shaft 15a of the cam follower 15 is a casing 9
It is fixed to the interlocking rod 15b on the outside. The interlocking rod 15b extends in the vehicle width direction and is slidably supported by a guide member 16 fixed to the upper case 9a.

The piston rods 12c of the left and right master cylinders 12a and 12b are connected to the left and right ends of the interlocking rod 15b.
The left and right master cylinders 12a, 12b are connected to the hydraulic hoses 17a, 1
7b is connected to the left and right wheel cylinders 19a, 19b of the rear wheel 18. The components from the master cylinders 12a and 12b to the wheel cylinders 19a and 19b constitute the transmission mechanism of the present invention. Each wheel cylinder 19a,
Although not shown, 19b is connected to the front and rear ends of a steering bracket 20 pivotally supported by a rear arm that supports a rear wheel 18. Further, a kingpin 20a, which serves as a steering center for the rear wheels 18, is planted in the bracket 20.

Next, the operation and effect of the apparatus of this embodiment will be described mainly with reference to FIG.

First, the general operation of the apparatus of this embodiment will be described. When the steering handle 5 is rotated right and left, the front steering bracket 5b fixed to the steering shaft 5a rotates the rear steering bracket 4a via the steering rod 7, whereby the front wheels 3 are steered left and right. It At this time, the drive gear 10 in the rear wheel steering unit 8 rotates to move the slide cam 11 back and forth. Then, as the cam 11 moves, the cam follower 15
Moves left and right along the inclination of the cam groove 13, which causes the left and right master cylinders 12a, 12b to generate hydraulic pressure. This hydraulic pressure is transmitted to the left and right wheel cylinders 19a and 19b of the rear wheel 18, and the rear wheel is steered to the left and right according to the hydraulic pressure.

Next, the steering direction and the steering amount of the rear wheels will be described in detail. First, in the neutral state in which the steering handlebar 5 is straightened, the cam follower 15 is located at the center of the inclined portion 13c of the cam groove 13, the left and right master cylinders 12a, 12b generate the same hydraulic pressure, and the rear wheels 18 is also in a straight state. When the steering handle 5 is steered to the right a little, the drive gear 10 also turns to the right, the slide cam 11 retracts, and the inclined groove 13c of the cam 11 moves the cam follower 15 to the right. The hydraulic pressure of the cylinder 12b becomes high. As a result, the right wheel cylinder 19b extends to steer the rear wheel 18 to the right, that is, in-phase with the front wheel 3. The inclined part
Since 13c is linear, while the cam follower 15 is in sliding contact with the inclined portion 13c, that is, when the steering angle is less than a predetermined steering angle, the front and rear wheels 3 and 18 are in phase and at a constant ratio. Steered.

When the steering wheel 5 is further steered,
The straight portion 13a of the cam groove 13 comes into sliding contact with the cam follower 15, so that the movement amount of the cam follower 15 does not change,
As a result, when the steering angle of the front wheels 3 exceeds a certain value, the rear wheels 18 are held at a constant steering angle. When the steering handle 5 is returned to its original position, the inclined portion 13c comes into sliding contact with the cam follower 15 again, so that the steering angle decreases at a constant rate. The same applies when the steering wheel 5 is steered to the left.

As described above, in the present embodiment, when the steering angle of the front wheels 3 is equal to or smaller than the reference, the rear wheels are controlled to the steering angle obtained by multiplying the front wheel steering angle by a certain ratio. The steering angle, that is, the turning angle of the steering wheel 5 can be easily estimated, and the driving becomes easier and more reliable, and the traveling stability is improved.

Further, when the front wheel steering angle becomes equal to or greater than the reference angle, the rear wheels are held at a constant steering angle, so that driving is facilitated from this point as well, and traveling stability is improved.

As described in the first embodiment, the present invention is characterized in that the front and rear wheel steering control is realized by the above mechanical structure.

On the other hand, the control operation described above can also be realized by using a microcomputer as shown in FIGS. The examples shown in FIGS. 5 and 6 are not included in the present invention.

In the figure, reference numeral 31 is a potentiometer that detects the steering angle of the front wheels, and outputs a voltage signal corresponding to the rotation angle of the steering shaft, for example. 32 is a vehicle speed sensor that detects the vehicle speed by counting the number of rotations of the front wheels, 33 is the detected steering angle,
Outputs a valve opening signal according to the detected vehicle speed to the hydraulic control valve 34.
CPU, 35 is a hydraulic unit that generates a predetermined hydraulic pressure, and 36 is an actuator such as a wheel cylinder that is supplied with the hydraulic pressure from the unit 35 according to the valve opening of the hydraulic control valve 34 and steers the rear wheels.

The CPU 33 detects that the detected vehicle speed is the reference speed (for example, 40k
m / hr) or less, the output is 0% regardless of the detected steering angle, that is, a fully closed signal is output, and when it is higher than the reference speed, the detected steering angle-valve opening map (No. 6 (b)), the valve opening corresponding to the detected steering angle is read out, and an opening signal corresponding to the opening is output to the hydraulic control valve 34. Here, FIG. 6 (b) is a map showing a target front-wheel steering angle-rear-wheel steering angle characteristic (FIG. 6 (a)).
In order to obtain (see), the relationship between the front wheel steering angle-rear wheel steering angle-valve opening is obtained in advance by experiments or the like. Further, the front-wheel steering angle-rear-wheel steering angle characteristic of the present embodiment is that when the front-wheel steering angle is equal to or less than the reference steering angle (for example, 10 °), it is multiplied by a constant ratio (for example, 0.1) to obtain the rear-wheel steering angle. , When the steering angle is greater than the reference steering angle, the rear wheel steering angle at the reference steering angle (1 ° in this example)
It has the property of being fixed to.

In the apparatus shown in FIGS. 5 and 6, the rear wheels are not steered when the vehicle speed is lower than the reference speed. Then, when the detected vehicle speed becomes higher than the reference, the CPU 33 sets the detected front wheel steering angle to 0.1
A valve opening signal corresponding to the target rear wheel steering angle, which is obtained by multiplying by the ratio, is output to the hydraulic control valve 34, and the hydraulic pressure corresponding to the opening of the valve 34 is supplied to the actuator 36. It is controlled by the steering angle. When the detected rudder angle is greater than the reference rudder angle,
The target rear wheel rudder angle does not change from the target rear wheel rudder angle at the reference rudder angle, and as a result, as shown in FIG. 6 (a),
Steering control of the rear wheels is performed.

〔The invention's effect〕

As described above, according to the front and rear wheel steering device of the present invention,
Since the steering angle of the rear wheels is controlled according to the steering angle of the front wheels, it is possible to improve the handling and running stability of the vehicle.

Further, a fan-shaped drive gear fixed to the lower end of the steering shaft and a rack portion protruding in a rod shape from the side edge of the cam portion of the slide gum to the side of the drive gear are engaged with each other, and the slide cam is rotated by the rotation of the steering shaft. Since there is a slight backlash between the drive gear and the gear of the rack, the amount of movement of the cam follower arranged in the cam groove of the slide cam is the same as that of the steering handle. It is highly accurate and directly proportional to the turning angle, and as a result, the steering angle of the rear wheels can be finely and accurately controlled.

Further, since the slide cam is integrally formed with a rectangular plate-shaped cam portion and a rack portion projecting from the side edge of the rectangular portion to the side of the drive gear in a rod shape, the entire slide cam has a rectangular box shape. Can be compactly covered with the casing of
This has the effect of avoiding problems such as the rear wheel steering unit malfunctioning due to muddy water adhering to it or flying stones hitting it.

[Brief description of the drawings]

1 to 4 are views for explaining a front and rear wheel steering system for a motorcycle according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram thereof, FIG. 2 is a cross-sectional side view of a rear wheel steering unit portion, FIG. 3 is a plan view with an upper case of the unit removed, and FIG. 4 is an automatic view to which the embodiment is applied. A side view of the front portion of the motorcycle, FIGS. 5 and 6 show a front and rear wheel steering device outside the scope of the present invention, FIG. 5 is a block diagram of the same, and FIG. 6 (a) is a front wheel steering angle-rear wheel. A steering angle characteristic diagram, FIG. 6B is a front wheel steering angle-valve opening degree characteristic diagram.

Claims (1)

(57) [Claims] 1. A steering angle of a front wheel steered by a steering wheel is detected. When the steering angle is equal to or larger than a predetermined angle, the rear wheel is steered in phase with the front wheel at a constant ratio. In a front-rear wheel steering system for a motorcycle, wherein the rear wheels are held constant at the rear wheel steering angle at the predetermined angle, a front steering bracket is attached to the lower part of the steering shaft, and the front steering bracket is A casing consisting of an upper case and a lower case of the rear wheel steering unit is arranged on the lower side, and the upper case is fixed to a steering shaft tube and a vehicle body frame that pivotally support the steering shaft, and is inserted into the casing. A fan-shaped drive gear is fixed to the lower end of the steering shaft, and a slide cam is arranged behind the drive gear, and the slide cam includes a rectangular plate-shaped cam portion having a slit-shaped cam groove, The drive gear is formed integrally with the cam. It is configured to move in the front-back direction by the rotation of the steering shaft, and the supporting shaft of the cam follower arranged in the cam groove is fixed to the interlocking rod by penetrating the upper case. At the same time, the interlocking rod is axially supported by a guide member fixed to the upper surface of the upper case so as to be movable at right angles to the moving direction of the slide cam, and one end of the transmission mechanism is connected to the end of the interlocking rod. The other end of the transmission mechanism is connected to a steering bracket for a rear wheel which is pivotally supported by a rear arm, and the movement amount of the cam follower is transmitted to the rear wheel side to steer the rear wheel. Front and rear wheel steering system.