JPH01172027A - Wheel drive device - Google Patents

Abstract

PURPOSE:To facilitate the setting of the starting point of motor drive portions by providing a plurality of the motor drive portions at a steering shaft, rotating a plurality of wheel portions thereby and controlling its rotation based on the output of an encoder which detects the rotary angle of each wheel portion. CONSTITUTION:This wheel drive device D has a rectangular parallelopiped box structure 2 fixed to a steering shaft 1 and motor driving shafts 4a, 4b provided on two faces opposite to each other in the box structure 2. Wheel portions 3a, 3b driven by these driving portions 4a, 4b are rotatably fixed to respective driving portion 4a, 4b to construct direct drive motors 5a, 5b. At this time, a rotor provided in wheel portions 3a, 3b is inserted inside the stator 7 of each motor 5a, 5b, a rotary encoder 19 is arranged inside this rotor 10 and the output signal of each encoder 19 is serviceable for the rotation control of respective wheel portions 3a, 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a motor-driven wheel drive device used in automatic guided vehicles and the like.

(Conventional technology and its problems) FIG. 5 is a conceptual diagram of a conventional wheel drive device.

In the figure, the wheel drive device D' includes a steering shaft S8, a steering drive motor M8 that drives the steering shaft S8, and a drive shaft S perpendicular to the steering shaft SS. , a wheel W of a drive shaft S, and a wheel drive motor M coupled to the drive shaft S.

The steering drive motor M8 is a motor for controlling the direction angle around the steering shaft S to point in a desired direction, and is equipped with an encoder (not shown) to detect the angle around the steering shaft S80. . Note that the steering drive motor M8 is fixed to the upper surface of a frame F corresponding to the vehicle body. Further, the wheel drive motor M- is a motor for rotating the wheel W and moving the wheel drive device D' and the frame F with respect to the floor surface G, and detects the rotation angle of the wheel W.
In order to measure the position, speed, etc. of frame F, an encoder (not shown) is provided.

Incidentally, in such a device, an incremental encoder is used as the encoder for the purpose of precise control. Therefore, when the power is turned on, it is necessary to rotate the motor approximately one revolution in order to find the reference position set on the rotary disk of the encoder (hereinafter, this will be referred to as "origin alignment").

Therefore, the conventional wheel drive device D' shown in FIG.
Also, when the power is turned on, it is necessary to rotate each of the drive motors M, M by about one rotation in order to align the origin of the encoder of each of the drive motors M, M.

However, since a plurality of wheel drive devices ifD' are normally provided on the frame, the origin alignment is performed by rotating the drive motor M8.M of each of the plurality of wheel drive devices D' immediately after power is turned on. For example, FIG. 6 shows a transport vehicle T in which a frame F is provided with four wheel drive devices D' to D4'.
FIG. Wheel drive device D
Rotate each wheel of 1' to D4' individually,
Since it is difficult to spin idly against the frictional force with the floor surface G, four wheel drive devices D are required to align the origin.
' to D4' are rotated at the same time. However, since each wheel may be oriented in an arbitrary direction when the power is turned on, there is a problem in that the transport vehicle T' moves in an unexpected direction. Further, there is a problem in that when the wheel drive devices D1' to D4' try to drive the frame F in mutually opposite directions, the wheels do not rotate and the origin cannot be aligned. On the other hand, in order to avoid these problems, in order to align the origin, it is necessary to make the transport vehicle T' float in the air by jacking up the entire transport vehicle T' and separate each wheel from the floor surface G, or a separate device for this purpose is required. Another problem arises.

(Purpose of the Invention) This invention was made to solve the above-mentioned problems, and the purpose of this invention is to align the origin of the encoder necessary for detecting the direction angle around the steering shaft and the rotation angle of the wheel. An object of the present invention is to obtain a wheel drive device that can easily perform the following operations.

(Means for Achieving the Object) In order to achieve the above object, the present invention provides a motor-driven wheel drive device comprising a plurality of motor drive sections attached to a steering shaft, and a plurality of motor drive sections. a plurality of wheel parts which are rotatably attached to each of the plurality of wheel parts, and which are rotatably driven by the plurality of motor drive parts with a rotational axis direction perpendicular to the steering shaft; and a rotation angle of each of the plurality of wheel parts. Detect = 4 - the axis of the steering shaft is provided with a plurality of encoders, and the plurality of driving parts are operated in coordination so that the plurality of wheel parts rotate in the same direction or in opposite directions to each other, thereby detecting the axis of the steering shaft. The surrounding direction angle and the rotational state of the plurality of wheel parts are controlled.

(Example) A. Structure of a wheel drive device FIG. 1 is a schematic cross-sectional view of a main part of a wheel drive device which is an embodiment of the present invention, and FIG. 2(a) is a plan external view thereof, and FIG. FIG. 2(b) is a front external view. In Figure 2, the wheel drive device is the steering shaft 1.
and a rectangular parallelepiped box structure 2 fixed to the steering shaft 1.
and motor drive parts 4a and 4b provided on two opposing sides of the box structure 2. Motor drive parts 4a, 4b
Wheel portions 3a and 3b having the same structure are rotatably attached to the wheel portion 3a.

3b is rotationally driven by motor drive units 4a and 4b, respectively. Note that the wheel parts 3a and 3b are provided so that their rotational axes A are perpendicular to the steering shaft 1 and are positioned symmetrically to each other with respect to the steering shaft 1. Corresponds to the axis. Also, as will be described later, wheel portions 3a, 3b and a drive portion 4a.

4b collectively constitute direct drive motors 5a and 5b, respectively. Since these direct drive motors 5a and 5b have the same structure,
The structure of one of the die reflexes 1 to the drive motor 5a will be explained below.

As shown in FIG. 1, the stator housing 6 of the direct drive motor 5a is fixed to the box structure 2. As shown in FIG. A stator 7 is fixed to the inner circumference of the cylindrical stator housing 6.

This stator 7 has stator windings 9 wound through slots (not shown) in a stator core 8.

A rotor 10 is inserted inside the stator 7, and the rotor 10 has a rotor yoke 11 and a magnet 12 attached to its outer peripheral surface.

Further, the rotor 10 is formed integrally with the wheel 13. A tire 14 is fixed to the outer peripheral surface of the wheel 13, and the wheel 13 and tire 14 are connected to the wheel portion 3.
It forms a. Furthermore, a bearing 15 such as a cross roller bearing or a four-point contact ball bearing is disposed on the inner peripheral surface of the wheel 13. This bearing 15 is held between the inner peripheral stepped portion of the wheel 13 and a fixing ring 16. The wheel 13 and the stator housing 6 are rotatably connected by a bearing 15.

An encoder shaft 18 is provided inside the rotor 10 and is fixed to the wheel 13 via a fixing plate 17 at the center of the outer surface of the rotor 10 . The encoder shaft 18 is an incremental rotary encoder 1
A rotary disk 20 having a slit arrangement is fixed to the tip of the encoder shaft 18 . The encoder 19 also has a fixed disk 1 light emitting diode.

There is no reference number for the photodetector transistor. ) etc., but since their structure is well known, detailed explanation will be omitted. This encoder 19 is for detecting the rotation angle of the direct drive motor 5a, thereby making it possible to measure the rotation angle, two rotation directions, and one rotation speed of the wheel portion 3.

Although not shown, the power supply lines from an external power source to the direct drive motors 5a and 5b, the power supply line to the encoder 19, and the signal line taken out from the encoder 19 are connected to the inside of the box structure 2 and the steering shaft 1. is passing through.

Direct drive motor 5a configured as above
(5b) is a so-called brushless DC motor, and the drive section 4a such as the stator 7 and rotor 10 and the wheel section 3a collectively form one brushless DC motor.

In addition, the entire wheel drive device has a bearing 21.
The steering axis 1 corresponds to the frame F corresponding to the vehicle body.
installed on. Unlike conventional devices, there is no motor at the upper end of the steering shaft 1.

B. Basic operation method of wheel drive device The basic operation of the wheel drive device as described above will be explained. FIG. 3 is a conceptual diagram showing the basic operation of the wheel drive device. In the figure, the wheel drive device has a rectangular wheel portion 3.3b and a dotted wheel center C.

a Cb, a linear drive shaft S connecting wheel centers C8 and Cb, and a drive shaft S. The steering shaft S8 is shown as a dotted steering axis S8 in the center of the wheel drive device, and is a schematic plan view of the wheel drive device. Further, the solid line and the broken line indicate the state before and after the operation, respectively, and FIG. 3(a) shows the straight-ahead operation. In straight motion,
It is sufficient to drive the wheel portions 3.3b by the same amount in the same direction. Therefore, the wheel portion 3a.

Direct drive motors 5a each drive motors 3b and 3b.
, 5b in the same direction at a constant speed, and if the rotational speed at this time is controlled, the wheel drive device if
The speed of movement of D can be controlled.

At this time, the encoders provided in the direct drive motors 5a and 5b respectively are connected to the wheel portions 3a and 3b.
The rotation direction and rotation speed of the wheel drive device can be detected, and based on this, the position, direction and speed of the wheel drive device can be measured.

FIG. 3(b) does not show the "in-situ rotation motion". That is,
By rotating the wheel portion 3.3b at a constant speed in the opposite direction, the position of the steering shaft S8 remains unchanged and only the rotation angle θ around the shaft can be changed. At this time,
The encoders provided in the direct drive motors 5a and 5b respectively detect circular arcs A, I11, . In addition to detecting the length of the arc, the speed at which the arc is drawn is also detected from its temporal change. Since the distance l between the wheel center C8° and Cb is constant, the arc 1. J! .

By detecting the length of , and detecting its advancing speed from its time change with each encoder, it is possible to know the rotation angle (angle θ) and rotation speed δ around the steering shaft S8.

FIG. 3(C) shows the movement to pivot 1. That is, without moving the wheel portions 3a or 3b), the wheel portions 3.
(or if you rotate only 3a), the wheel center Ca
The entire wheel drive device rotates using the position (or Cb) as a fulcrum. At this time, the rotation angle of the steering shaft S8 around that axis is the distance between the wheel centers C and Cb @
The data detected by the encoder 19 of the direct drive motor 5b (or 5a) is equal to the angle θ of the fan shape, where l is the radius and the arc 1b (or Aa) drawn by the wheel portion 3b (or 3a) is the circumference. Accordingly, the rotation angle (angle θ) and rotation speed θ of the steering shaft S8, that is, the traveling direction and traveling speed of the wheel drive device can be known.

FIG. 3(d) shows the nulling operation. That is, by making the rotational speeds of the wheel parts 3a and 3b different, the entire wheel drive device rotates about a point O located on a line that is an extension of the line segment connecting the wheel centers C8 and Cb. The rotation radius R of the steering shaft S8 at this time
1 angle θ and the rotational speed θ are determined by the distance 1 between the wheel centers C and Cb and the relative difference between the rotational speeds of the wheel portions 3a and 3b. These can also be determined from the detection data of the encoders 19 of the two direct drive motors 5a and 5b, respectively, as described above.

As described above, the wheel drive device in this embodiment is controlled to move in any direction and speed by controlling the rotational state of the wheel portion 3.3b. Further, its direction and speed are determined by the rotation angle 2 rotation direction and rotation speed of the wheel portion 3.3b. Therefore, the wheel part 3.

Direct drive motors 5a each drive motors 3b and 3b.
, 5b, using encoders 19 built in, respectively.
Each direct drive motor 5a.

By detecting and controlling the rotational position and rotational speed of the wheel 5b, the operation of the entire wheel drive device can be controlled.

Example of Application to C0 Transport Vehicle FIG. 4 is a conceptual diagram showing a transport vehicle T using four wheel drive devices D1 to D4, FIG. 4(a) is a plan view, and FIG. 4(b) shows a side view. In the figure, a thin rectangular parallelepiped-shaped frame F has a first
Four wheel drive devices D to D4 having the same structure as the wheel drive device shown in the figure are provided. Further, encoders E to E4 are provided at the upper ends of steering shafts 81 to S4 (corresponding to the steering shaft 1 in FIG. 1) of each wheel drive device D to D4, respectively. These encoders E to E4 are fixed to the upper surface of the frame F, and are used to detect the angle of each steering axis S-84.

As mentioned above, the rotation angles around the respective steering shafts 81 to $4 are determined by the two wheel portions 3a and 3b (
i.e. two direct drive motors 5a, 5b)
is determined by the rotation angle of Therefore, it is not necessary to provide encoders E to E4 as shown in Fig. 4, but in this application example, in order to improve the accuracy of detecting the rotation angle around each of the steering axes S to S4, encoders E to E4 as shown in FIG. Further encoders E to E4 are provided.

On the top surface of the frame F are wheel drive devices D1 to D4.
a power supply device B for supplying power to the encoder E1;
A control device C is provided which receives angle data from the wheels D to E4 and controls the wheel drive devices D to D4. Power supply device B and each wheel drive device D ~
Each of D4 is connected by a power supply wiring LB, and the control device C is connected to each of wheel drive devices D1 to D4 and encoders E to E4 by control wiring. connected with.

This conveyance vehicle T operates four wheel drive devices D1 to D4 in coordination under the control device C.
It can be controlled to move at any position, direction, and speed. That is, as shown in FIG. 3, each of the wheel drive devices D to D4 can arbitrarily control the angle and speed of the steering shaft S-84 by controlling the rotation of the two wheel parts, respectively. If the wheel drive devices D1 to D4 are controlled to move in coordination with each other, the movement of the entire transport vehicle T can also be controlled arbitrarily.

Even in such a transport vehicle T, when the power is turned on, the encoder E-E4 and each wheel drive device D to D4 are
Each of the two direct drive motors has two
It is necessary to align the origin of the encoder 19 of the stand.

However, in this carrier T, each wheel drive device D
-D4 can be rotated in place as shown in FIG. 3(b). Therefore, if you first rotate each wheel drive device D1 to D4 on the spot immediately after power is turned on, you can easily align the origin of each of the two encoders E1 to E4 and each wheel drive device D to D4. can be done. Further, at this time, the position of the entire transport vehicle T remains unchanged, and unlike the conventional transport vehicle T, the transport vehicle T does not move in an unexpected direction.

D. Modifications It should be noted that the present invention is not limited to the above-mentioned embodiments, and for example, the following modifications are also possible.

(2) The wheel part and the drive part do not need to be integrally constructed as a direct drive motor, but may be formed as separate parts and connected by other connecting means. Further, it goes without saying that each structure is not limited to the above embodiments.

■Examples to which the wheel drive device is applied are not limited to the above-mentioned conveyance vehicles, but also in cases where the wheel drive device is applied to three vehicles.
The vehicle may be a stand or a transport vehicle in which only some of the wheels are wheel drive devices. It is sufficient to attach two wheel sections to one wheel axle, but even if three or more wheel sections are attached,
As long as they are driven in coordination, there is no particular problem.

(2) The object of the present invention can be achieved even with a single wheel drive device, and the present invention can be applied to devices other than transport vehicles.

(Effects of the Invention) As explained above, according to the present invention, the steering shaft is provided with a plurality of wheel parts, each of which is driven by a motor, and the plurality of wheel parts are rotated in coordination with each other. Since an encoder is provided to detect the rotation angle of each wheel section, by rotating the plurality of wheel sections according to a predetermined rule, it is possible to rotate the plurality of wheel sections on the spot about the steering shaft. Therefore, even when the power is turned on, the origin of the encoders of each wheel section can be easily aligned.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of essential parts of a wheel drive device as an embodiment of the invention, FIG. 2 is an external view of a wheel drive device as an embodiment of the invention, and FIG. FIG. 4 is a conceptual diagram of a conveyance vehicle to which the wheel drive device as an embodiment of the present invention is applied, and FIG. 5 is a diagram of the basic operation of a wheel drive device as an embodiment of the present invention. Conceptual Diagram of Device FIG. 6 is a conceptual diagram showing the operation of a transport vehicle to which a conventional wheel drive device is applied. DESCRIPTION OF SYMBOLS 1... Steering shaft, 2... Box structure, 3a,
3b...Wheel part, 4a, 4b...Drive part, 5a
, 5b... Direct drive motor, 7... Stator, 10... Rotor, 13... Wheel, 14... Tire, 1... Encoder

Claims (2)

[Claims] (1) A motor-driven wheel drive device, comprising: a plurality of motor drive units attached to a steering shaft; and a motor drive unit rotatably attached to each of the plurality of motor drive units; , a plurality of wheel parts that are rotationally driven with a direction perpendicular to the steering axis as a rotation axis direction, and a plurality of encoders that detect rotation angles of each of the plurality of wheel parts, and the plurality of wheel parts are Controlling the direction angle around the axis of the steering shaft and the rotational state of the plurality of wheel parts by operating the plurality of motor drive parts in coordination so as to rotate in the same direction or in opposite directions. A wheel drive device featuring: (2) The wheel drive device according to claim 1, wherein the drive section is a direct drive motor, and the wheel section is configured integrally with a rotor of the direct drive motor.