JPS6357376A - Steering device for electric motor vehicle - Google Patents

Abstract

PURPOSE:To prevent the damage of the floor surface by the steer without driving under the stop condition of a vehicle by interlockingly steering front wheels and rear wheels in opposite directions and deviating the steering shaft of each wheel from the wheel center in a vehicle using two wheels at diagonal positions as driving wheels, such as a floor sweeping vehicle. CONSTITUTION:When this invention is applied for the steering device of a self-advancing floor sweeping robot, traveling DC motors 12 are integrally assembled to two wheels 10A, 10C at diagonal positions among four wheels 10 (10A-10D) having the same diameter, and these wheels 10A, 10C are made to function as driving wheels. Individual wheels 10 are rotatably provided around the vertical steering shafts 16 (16A-16D). In this case, the steering shafts 16 of individual wheels 10 are set at positions deviated to the inside of a vehicle body on the wheel shafts from the wheel centers A-D. The left and right front wheels 10A, 10B and rear wheels 10C, 10D are interlocked so as to be integrally steered by gear trains respectively, and the steering angles are controlled by motors 20, 22.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is characterized in that each pair of front wheels and rear wheels is arranged in a square shape, two wheels at diagonal positions are used as drive wheels, and each wheel is connected to a vertical steering axis. The present invention relates to a steering device for an electric vehicle that rotates around the vehicle to steer the vehicle.

(Background of the Invention) In an electric vehicle for cleaning floors, etc., two wheels at diagonal positions among four wheels arranged in a square shape are used as driving wheels,
Electric vehicles have been considered in which each wheel can be steered around a vertical steering axis.

In this case, the configuration was simplified by integrating the driving electric motor and the drive wheels to form a unit, and configuring the entire two units to rotate around a vertical steering axis for steering. There are some (for example, Japanese Patent Application No. 60-27989)
No. 2). Conventionally, these two units were mounted rotatably around a steering axis passing through the grounding point of the drive wheel, and the other two non-drive wheels were caster wheels.

In a vehicle in which the driving wheels are steered around their grounding point and the non-driving wheels are caster wheels, the driving wheels strongly hit the floor when the vehicle is steered while the vehicle is stopped, that is, when performing a stationary turn. This results in the problem of damaging the floor surface. Furthermore, depending on the running direction after the stationary turn, the caster wheels, which are non-driven wheels, may not be able to smoothly follow the running direction, and this poses a problem in that the initial movement after the stationary turn is not particularly smooth.

(Objective of the Invention) The present invention was made in view of the above circumstances, and is an electric vehicle in which two diagonally positioned wheels are used as drive wheels and all wheels are steerable. To provide a steering device for an electric vehicle, which does not cause damage to the floor surface even when the steering is turned in a fixed direction, and allows smooth running after the steering is turned in a fixed direction.

(Structure of the Invention) According to the present invention, the object is to provide a pair of left and right front wheels and a pair of left and right rear wheels, and use the two diagonally positioned wheels as drive wheels, while each wheel rotates around a vertical steering axis. In a steering device for an electric vehicle that rotates and steers, two front wheels and two rear wheels are respectively steered in opposite directions, and the steering axis of each wheel is deflected from the center of the wheel in the direction of the wheel axis. This is achieved by a steering device for an electric vehicle, which is characterized in that the

(Embodiment) FIG. 1 is a plan view showing a steering device of a self-propelled floor cleaning robot which is an embodiment of the present invention, and FIG. 2 is a perspective view of this robot.

In these figures, reference numerals 10 (10A-10D) are four wheels of the same diameter. Each wheel 10 is arranged to form a quadrangle, and a driving DC motor 12.12 is integrally assembled to the two wheels 10A and IOC at diagonal positions.
)14.14 is formed. This unit 14.1
Wheels 10A and IOc included in No. 4 serve as driving wheels. Each wheel 10 is rotatably held on a truck 18 by a vertical steering shaft 16 (16A-16D) that is offset toward the inside of the vehicle body on a wheel axis from a wheel center A-D.

The left and right front wheels 10A and IOB are interlocked by a gear train so that they are integrally steered, and the steered angle is controlled by an electric motor 20. The left and right rear wheels 10c and 10D are similarly linked to integrally steered by a gear train, and their steered angles are controlled by an electric motor 22.

In FIG. 2, 24 is a battery, 26 is a rotating pad, and 2
8 is a water spray/recovery tank, 30 is a controller, and 32 is an operation panel. A zero-rotation pad 26 polishes the floor surface while the robot is running. 34. 34 is a suction device that sucks and collects detergent, water, wax, etc. sprayed from the front of the rotary pad 26 while the robot is running behind the rotary pad 26. This robot is automatically controlled to clean by moving all over the floor while avoiding contact with walls using a large number of distance sensors.

If you drive electric @20.22 while the robot is stopped,
The pair of left and right front wheels 10A, 10B or the pair of left and right rear wheels 10C, IOD are steered left and right about their respective steering shafts 16 by the gear train. At this time, since the steering axis 16 is deviated from the center A-D of each wheel 10 on the wheel axis, each wheel lO moves on a circle centered on the steering axis 16.

In other words, since the steering shaft 16 is not located on the grounding point of each wheel 10, the wheels 10 do not strongly rub the floor surface due to steering, and the floor surface is not damaged.

In addition, since the non-drive wheels 10B and IOD are not caster wheels but are steered in conjunction with the drive wheels 10A and IOC, the non-drive wheels 1OB and IOD are steered while the vehicle is stationary, that is, when driving after stationary steering. It follows smoothly and enables smooth running.

FIG. 3 is a plan view showing a steering device according to another embodiment. This embodiment is suitable when the driving DC motors 12, 12 are connected in series. That is, if both electric motors 12.12 are connected in series in this way, the electric motor a12.1
2 control systems are sufficient for one set, which simplifies the configuration.

However, in this case, if the configuration is as in the embodiment shown in FIG. 1 and the front wheels 10A to IOB and the rear wheels IOC, 100 are steered in opposite directions, the two electric motors 12, 12 will both speed up or decelerate. When turning to the left (or right) in FIG. 1, when the drive wheels 10A are steered to the left (or right) and the drive wheels 10c are steered to the right (or left), both the steering shafts 16A, In this way, when both electric motors 12.12 speed up (or decelerate) together, the speed of each electric motor 12.12 increases (or decelerates) in order to transfer in the running direction (or backwards) with respect to 16C. The back electromotive voltage increases (or decreases), which increases the total fluctuation of the back electromotive voltage, making stable operation of the motor 12, 12 impossible.

The embodiment of FIG. 3 solves this problem. That is, the steering axes 16A and 16B of the front wheels 10A and 10B are
Contrary to the case shown in the figure, the wheels are located on the outside of the vehicle body at the wheel centers A and H.

Therefore, when turning left, the outer drive wheel 10A decelerates, the inner drive wheel 10c accelerates, and the sum of the two becomes approximately zero and cancel each other out. Therefore, the total back electromotive voltage hardly changes, and stable operation of both electric fi12.12 is possible.

In the above embodiments, both front axles 10A and IOB or both rear wheels 10c and IOD are linked using a gear train, but in the present invention, instead of this, they are linked by a link mechanism or by another mechanism. Of course, you can.

In addition, in the embodiment shown in FIG. 3, the front wheels 10A and IOB are connected to the steering axis 1.
6A and 16B are arranged on the inside of the vehicle body, but the same effect can be obtained by arranging the front wheels on the outside of the vehicle body with respect to the steering shaft and the rear wheels on the inside of the vehicle body with respect to the steering shaft when moving forward and backward.

(Effects of the Invention) As described above, the present invention steers the front and rear wheels in opposite directions, and also deviates the steering axis of each wheel from the center of the wheel in the direction of the wheel axis. To make the wheels roll without strongly scraping the floor surface during stationary steering when the vehicle is stopped. This allows for smooth steering without damaging the floor surface.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of the present invention, FIG. 2 is a perspective view of a cleaning robot to which the same is applied, and FIG. 3 is a plan view showing another embodiment. 10A, IOC...driving wheel, 10B, IOD... non-driving wheel, 12... DC electric motor for driving, 16... steering axis, A-D... wheel center.

Claims (4)

[Claims] (1) A steering device for an electric vehicle that is equipped with a pair of left and right front wheels and a pair of left and right rear wheels, and uses the two diagonally positioned wheels as drive wheels, while rotating each wheel around a vertical steering axis to steer the vehicle. An electric vehicle characterized in that two front wheels and two rear wheels are respectively steered in opposite directions in conjunction with each other, and the steering axis of each wheel is offset from the center of the wheel in the direction of the wheel axis. Steering device. (2) The electric vehicle according to claim 1, wherein a DC motor for driving is attached to each of the two drive wheels, and the electric motor and the drive wheels are steered as a unit. Steering device. (3) The steering device for an electric vehicle according to claim 1, wherein both electric motors are connected in series. (4) Position each steering axis of the two front wheels between the two front wheels,
4. A steering device for an electric vehicle according to claim 3, wherein each of the steering axes of the two rear wheels is located on the outer side of both rear wheels.