JP2639868B2 - Control method of reach type forklift - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a reach-type forklift capable of steering a road wheel, the attitude of which can be corrected in any traveling direction.

[0002]

2. Description of the Related Art A multidirectional vehicle disclosed in Japanese Patent Publication No. 58-15342 has been proposed. This vehicle a
As shown in FIG. 14, when the traveling direction is set to A, the caster wheels c and f are turned and fixed, and the cylinders are hydraulically controlled so that the caster wheels d can be turned. By steering, Ackerman can be steered.

As shown in FIG. 15, when the traveling direction is set to B, the caster wheels d and f are turned and fixed along the traveling direction, and the cylinders are hydraulically controlled so that the caster wheels c can be turned. Then, the Ackerman steering can be performed in the same manner as described above by steering the steering wheel b.

[0004]

However, when switching the traveling direction between A and B, individual operations such as pressing a button switch or the like after stopping the vehicle a, so-called mode switching, are required. The traveling direction cannot be changed continuously. Further, the Ackerman steering and the posture of the vehicle a are corrected only when the traveling direction is A or B.

The present invention has been devised in view of the above problems, and its object is to change the traveling direction continuously in all directions while maintaining the driving feeling of a normal reach-type forklift, and to use the Ackerman. An object of the present invention is to provide a reach-type forklift that completely satisfies Junt's theory and that can correct the posture of a vehicle body in all traveling directions.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a road wheel is steerably supported on each of left and right straddle arms, and means for detecting a steering angle of the left and right road wheels is provided. A reach-type forklift comprising a drive wheel and a means for detecting a steering angle of the drive wheel, wherein the forklift travels in a reference direction along a center line of a vehicle body and an angle between the reference direction and a traveling direction that can be arbitrarily determined. A traveling angle input means capable of instructing the traveling angle is provided, and when the traveling angle is on the right side with respect to the reference direction, the steering angle of the right road wheel is made to coincide with the traveling angle, and the right road The turning center of the vehicle body determined by the geometric relationship between the wheel and the drive wheel is calculated, and the extension of the center line of the rotation axis of the left road wheel intersects the turning center. The steering control the cormorant left load wheel
If the advancing angle is on the left,
Match the steering angle, the left road wheel and the drive
The turning center of the body determined by the geometric relationship with the wheel
Calculate the extension line of the center line of the rotation axis of the right road wheel
Controls the right road wheel to cross the turning center.
If the advancing angle is zero,
The above-mentioned problem is solved by the configuration in which the steering angle of the wheel is set to zero.
It is decided.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a reach type forklift (hereinafter, referred to as a forklift)
The forklift 1 simply supports the main body 2 and the left and right straddle arms 20, 20 protruding from the main body 2 so as to steer the load wheels 5, 6, respectively. It has a steerable drive wheel 4.

[0008] The drive wheel 4 is
Swivel swing gear 17 mechanically linked to handle 3
The turning gear 17 is provided with a potentiometer 18 capable of detecting the amount of rotation of the turning gear 17, whereby the steering angle of the drive wheel 4 can be detected. Although not shown, caster wheels are arranged beside the drive wheel 4 in order to secure running stability.

A loading / unloading device 7 is mounted between the straddle arms 20 so as to be able to slide back and forth and to be able to move up and down by a lift cylinder (not shown).

The load wheels 5 and 6 are rotatably supported on pivot brackets 8 and 9 that are pivotable with respect to the straddle arm 20. The pivot brackets 8 and 9 have a transmission tool 10 such as a chain or a belt. The steering motors 11 and 12 are mounted via the motors 10 and 10, respectively. Therefore, by rotating the steering motors 11 and 12, the left and right road wheels 5 and 6 can be steered about the steering center points L and R, respectively. still,
In this example, the center of the road wheel is the steering center point. However, a so-called kingpin offset may be provided by a predetermined amount.

The output shafts of the steering motors 11 and 12 are provided with a potentiometer 1 capable of detecting the amount of rotation.
3 and 14 are attached so that the steering angles of the left and right road wheels 5 and 6 can be detected.

The main unit 2 is provided with a control device 16 and a travel angle input device 15. The travel angle input device 15
Is preferably arranged near a driver's seat (not shown) so that the driver can arbitrarily set the potentiometer.

The travel angle input device 15 is illustrated as an example in which an arrow is provided on the surface of the operation unit as shown in the figure. The arrow indicates the direction of travel, and the driver
Is shown so that the user can easily know which direction the current traveling direction is, and the details will be described later.

Next, the basic concept of the present invention will be described together with the operation with reference to FIGS. In FIG.
The steering center of the drive wheel 4 is D, the axis on which the turning centers connecting the steering centers L and R of the left and right road wheels 5 and 6 are arranged is G (hereinafter simply referred to as axis G), and the forklift 1
Is the center line of the vehicle.

Here, the direction in which the forklift 1 travels is referred to as the traveling direction, and when the steering angles of the left and right road wheels 5, 6 are zero (the state shown in FIG. 4), the vehicle body center line C The traveling direction S coincides with the traveling direction S. The traveling direction S
Is a direction which is a reference when the forklift 1 is steered. Usually, the driver turns the steering wheel to the left or right from the neutral position facing the front in that direction, and thereby the steering Change the attitude angle of the vehicle body. Therefore, if the steering angle of the drive wheel is zero when the traveling direction S is considered as a reference, the forklift 1 travels straight.

Next, the advancing angle means an angle between the vehicle body center line C and the advancing direction S. Accordingly, in the state illustrated in FIG. 4, the vehicle center line C and the traveling direction S coincide with each other, and thus become zero.

In the present invention, the traveling direction S can be arbitrarily determined, and can be set by operating the aforementioned traveling angle input device 15. In other words, irrespective of the actual direction of the vehicle body, the forklift 1 can be steered as if the vehicle center line C is in a direction coinciding with an arbitrarily determined traveling direction. Therefore, the driver can steer the forklift with reference to the direction of the arrow shown on the advancing angle input device 15.

Next, the steering angles θL and θR of the left and right road wheels 5 and 6 are respectively calculated from the axis G and the steering centers L and R of the road wheels 5 and 6 with respect to the center line of the rotation axis of each road wheel. Extension lines HL, HR (hereinafter simply extension lines HL
, HR).

The steering angle θ 1 of the drive wheel 4 refers to an angle between an extension line F (hereinafter simply referred to as an extension line F) of the center line of the rotation axis of the drive wheel 4 and an axis perpendicular to the vehicle body center line C. Each angle is considered to be counterclockwise as positive.

FIG. 5 shows that the traveling angle of the forklift 1 is zero,
The moment when the steering angle of the drive wheel 4 is traveling at θ1 is shown. In this case, since the traveling direction S coincides with the vehicle center line C, the steering angles of the left and right road wheels are both set to zero. The turning center P of the forklift 1 is geometrically determined by the axis G and the steering angle θ1 of the drive wheel 4, and the forklift 1 is turning around this point.

FIG. 6 shows the moment when the traveling angle of the forklift 1 is indicated by θ0 by the traveling angle input device 15 and the steering angle of the drive wheel 4 is θ1. In this case, the steering angle θL of the left road wheel 5 is made equal to the advancing angle θ0, and the intersection of the extension line HL of the left road wheel 5 and the extension line F of the drive wheel 4 in that state is defined as the turning center P. I do.

The extension HR of the right road wheel 6
Is steered so that the right road wheel can coincide with the turning center P.

FIG. 7 shows the moment when the forklift 1 is traveling when the traveling angle of the forklift 1 is indicated by θ0 by the traveling angle input device 15 and the steering angle θ1 of the drive wheel 4 is equal to the traveling angle θ0. Accordingly, as described above, the steering angle θL of the left road wheel 5 is steered to be equal to the advance angle θ0, and the intersection of the extension line HL of the left road wheel 5 and the extension line F of the drive wheel 4 is determined as the turning center P. However, in such a state, the extension lines HL and F are parallel to each other, and the turning center P is located at infinity of the axis G on which the turning centers are arranged.

Further, an extension HR of the right road wheel 6
To match the turning center P, the extension line HR
Is parallel to both extension lines HL and F, and the forklift 1
Is an oblique traveling in which the vehicle travels along the traveling direction S without changing the direction of the vehicle body. This is because the steering angle of the drive wheel 4 becomes zero when the traveling direction S is considered as a reference for steering the forklift 1.

Next, FIG. 8 shows a moment when the forklift 1 is traveling when the traveling angle θ0 = π / 2 is specified by the traveling angle input device 15 and the steering angle of the drive wheel 4 is θ1. . Therefore, as described above, the steering angle θL of the left road wheel 5 is set to π / 2, the intersection of the extension line HL of the left road wheel 5 and the extension line F of the drive wheel 4 is set as the turning center P, and the right road wheel The steering of the right road wheel is controlled so that the extension line HR of 6 can coincide with the turning center P.

In such a state, the actual wheelbase becomes very short as L1, so that the posture change of the forklift 1 can be extremely severely performed.

When the drive wheel 4 is further cut from the state shown in FIG. 8 and the steering angle θ1 of the drive wheel is set to + π / 2, the forklift 1 moves along the traveling direction S as described with reference to FIG. Ride in the same direction without changing the body posture. Moreover, by steering the drive wheel 4 in the traveling direction S, the posture can be corrected.

FIG. 9 shows the traveling angle −θ in the minus direction.
The case where 0 is indicated is exemplified. In this case, the steering angle θL of the right road wheel 6 is made equal to the advancing angle −θ0, and the extension HR of the right road wheel 6 and the extension F
Is defined as the turning center P. Then, the left road wheel 5 is steered so that the extension line HL of the left road wheel 5 can coincide with the turning center P.

FIG. 10 shows the case where the advancing angle θ0 = −π / 2. In this case, the wheel base is L2, which can be made slightly longer than in the case of FIG.

FIG. 11 exemplifies a case where both the traveling angle θ0 and the steering angle of the drive wheel are −π / 2.

The above is the basic concept of the present invention. By performing the above-described control, the Ackerman-Jant theory can be satisfied in all traveling directions.
Also, by giving an instruction of the traveling angle, for example, in the state shown in FIG. 6, the vehicle center line C of the forklift 1 is vertical in the figure, but as if the vehicle center line C is at the specified traveling angle θ0. The posture of the forklift 1 can be corrected on the assumption that the vehicle exists in the traveling direction S along the vehicle.

Therefore, no matter what direction the vehicle center line C of the forklift 1 actually is, an arbitrary traveling direction S is given, and the posture of the forklift 1 can be corrected based on the traveling direction S.

The means for realizing the above concept will be described in detail with reference to the control block diagram shown in FIG.

The control unit 16 includes an A / D converter, a ROM in which programs and the like are stored, and an RA as a working memory.
M, an MPU as a microprocessor, a D / A converter, and a motor controller 19, which are connected by a bus line or I / O.

The A / D converter includes a traveling angle input device 1
5 and the steering angles .theta.D, .theta.R and .theta.L from the potentiometers 18, 14, and 13, respectively.
The A / D converter converts an input signal from an analog signal to a digital signal.

Based on these signals, the MPU calculates the steering angles θL and θR of the left and right road wheels 5 and 6. Note that this calculation processing procedure is stored in the ROM, and will be described later.

The steering angles θL and θR of the left and right road wheels 5 and 6 calculated by the MPU are calculated based on the deviation between the calculation result and the current steering angle detection value. The turning speed of No. 6 is determined, and is converted into an analog signal by the D / A converter 58, and then output to the left and right steering motors 11 and 12 via the motor controller 19.

The motor controller 19 has an MPU
A control signal is input via the I / O via the I / O, and controls such as forward rotation and reverse rotation of the steering motors 11 and 12, and forced locking in the event of an abnormality are performed.

Next, the processing procedure of the MPU will be described with reference to the flowchart shown in FIG. First, memory and I / O
Are initialized (S1, S2), and initialization is performed so that the advancing angle θ0 of the forklift 1 is set to zero (S3).

Next, the advance angle θ 0 of the forklift 1 and the drive wheel 4 input from the advance angle input device 15
Is stored in the RAM (S4, S4).
5).

Next, coordinate conversion is performed on a later-described reference coordinate axis by the advance angle θ0 (S6). If the advancing angle is zero (Y in S7), both steering angles θL and θR of the left and right road wheels 5, 6 are set to zero (S8, S9) and output (S8).
10).

On the other hand, if the advancing angle θ0 is not zero (N in S7), it is determined whether or not the advancing angle θ0 is positive (S11).
If the traveling angle θ0 is positive (Y in S11), the steering angle θL of the left road wheel 5 is made equal to the traveling angle θ0 (S1).
2) The steering angle θR of the right road wheel 6 is calculated and output (S13, S10).

Further, if the advancing angle θ0 is negative (S11)
N), the steering angle θR of the right road wheel 6 is changed to the advance angle θ0.
(S14), the steering angle θ of the left road wheel 5
L is calculated and output (S15, S10).

Next, among the processing procedures of the MPU, the procedure of the coordinate conversion performed in step S6 and the subroutine of the steering angle calculation in steps S13 and S15 will be described.
This will be described in detail with reference to FIGS.

Now, as shown in FIG. 12, the advancing angle of the forklift 1 is + θ0 (that is, Y in step S11 of the flowchart of FIG. 3), and the steering angle of the drive wheel 4 is +
θ1.

Here, consider a rectangular coordinate axis (xy) in which the y-axis coincides with the vehicle body center line with the representative point E arbitrarily defined on the vehicle body center line as the origin. The steering center points L and R of the left and right road wheels 5 and 6 on this orthogonal coordinate axis (xy)
And the coordinates of the steering center point D of the drive wheel 4 are (xL
, YL), (xR, yR) and (xD, yD).

First, consider a transformed coordinate axis (XY) obtained by rotating the above-described orthogonal coordinate axis (xy) by the advancing angle θ0, and consider the steering center points L, R on the transformed coordinate axis (XY). And coordinates (XL, YL), (XR, YR) and (XD, YD) of D and D. These coordinates are expressed as
Can be obtained by

(Equation 1)

(Equation 2)

(Equation 3)

Next, the coordinates (Xp, Yp) of the turning center P on the transformed coordinate axes (XY) are calculated. Therefore, the intersection between the extension HL of the left road wheel 5 and the extension F of the drive wheel 4 is determined.

The extension line HL of the left road wheel 5 is expressed by Equation 4 on the transformed coordinate axis (XY).

(Equation 4)

The extension line F of the drive wheel is expressed by the following equation 5 on the transformed coordinate axis (XY).

(Equation 5)

When the intersection of both straight lines is obtained, it is clear that Y = YL for the Y coordinate, and the X coordinate X
P can be represented by Equation 6.

(Equation 6)

Here, the steering angle θR of the right road wheel 5
And the tangent of the difference between the advancing angle and the advancing angle θ0 is as shown in Expression 7.

(Equation 7)

From Equation 7, the steering angle θ of the right road wheel 6 is obtained.
R can be obtained by Expression 8.

(Equation 8)

Similarly, FIG. 13 shows that the advancing angle of the forklift 1 is -θ0 (that is, N in step S11 of the flowchart of FIG. 3), and the steering angle of the drive wheel 4 is +.
This shows the state of θ1. In this case, the extension line HR of the right road wheel 5 is expressed by Expression 9 on the transformation coordinate axis (XY).

(Equation 9)

The extension line F of the drive wheel is expressed by the above equation 5 on the transformed coordinate axis (XY).

When the intersection of the two straight lines is found, it is clear that Y = YR for the Y coordinate, and the X coordinate is
Can be represented by

(Equation 10)

Here, the steering angle θL of the difference road wheel 5
And the tangent of the difference between the traveling angle and the traveling angle θ0 is as shown in Equation 11.

[Equation 11]

From equation (11), the steering angle θL of the left road wheel 5 can be obtained from equation (12).

(Equation 12)

The steering angles θL and θR of the left and right road wheels 5 and 6 obtained by the above calculation are output, and each road wheel is steered.

The coordinates of the steering center points L and R of the road wheels 5 and 6 and the steering center point D of the drive wheel 4 are represented by (xL, yL), (xR, yR) and (xD, y).
D) and the like are stored in the ROM in advance.

Although the present invention has been described in detail, the present invention is not limited to the above-described embodiment. For example, the steering mechanism of the road wheel is constituted by using transmission means such as various gears and links other than the belt. It may be something.

Further, the origin E of the rectangular coordinate system (xy) can be variously used other than the one shown in this embodiment, and may be other than on the vehicle center line.

[0063]

According to the present invention, as a result of employing the above method,
Since the vehicle satisfies the Ackerman-Jantt theory in all running states, the road wheel can be prevented from slipping as much as possible, and smooth steering can be performed.

Further, since the traveling direction can be continuously changed in all directions without discontinuous operation such as mode switching, no matter in which direction the forklift body is actually facing, the traveling direction is arbitrary. , The posture of the body of the forklift can be corrected. Therefore, the required traveling area can be minimized, and the passage space required for traveling can be saved as much as possible in the warehouse.

[Brief description of the drawings]

FIG. 1 is a plan view of a reach type forklift used in the present invention.

FIG. 2 is a control block diagram of the present invention.

FIG. 3 is a flowchart of the present invention.

FIG. 4 is a plan view illustrating the operation of the present invention.

FIG. 5 is a plan view illustrating the operation of the present invention.

FIG. 6 is a plan view illustrating the operation of the present invention.

FIG. 7 is a plan view illustrating the operation of the present invention.

FIG. 8 is a plan view illustrating the operation of the present invention.

FIG. 9 is a plan view illustrating the operation of the present invention.

FIG. 10 is a plan view illustrating the operation of the present invention.

FIG. 11 is a plan view illustrating the operation of the present invention.

FIG. 12 is a plan view illustrating the control content of the present invention.

FIG. 13 is a plan view illustrating the control content of the present invention.

FIG. 14 is a plan view for explaining a conventional multidirectional traveling vehicle.

FIG. 15 is a plan view for explaining a conventional multi-directional traveling vehicle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reach type forklift 2 Main part 3 Handle 4 Drive wheel 5 Left road wheel 6 Right road wheel 11 Steering motor 12 Steering motor 13 Potentiometer 14 Potentiometer 15 Advance angle input device 16 Control device 18 Potentiometer 20 Straddle arm

Claims (1)

(57) [Claims] 1. A drive wheel steerable by a steering wheel, comprising a means for supporting a road wheel on each of left and right straddle arms so as to be steerable and detecting a steering angle of the left and right road wheels, and steering of the drive wheel. A reach type forklift provided with means capable of detecting an angle, wherein a traveling direction is an angle between a reference direction along the center line of the vehicle body and a traveling direction that can be arbitrarily determined,
A traveling angle input means capable of instructing the traveling angle is provided, and when the traveling angle is on the right side with respect to the reference direction, the steering angle of the right road wheel is matched with the traveling angle, and the right road wheel and the The turning center of the vehicle body, which is determined by the geometric relationship with the drive wheel, is calculated, and the left road wheel is steered so that the extension of the center line of the rotation axis of the left road wheel intersects with the turning center. If
The steering angle of the left road wheel.
The geometric relationship between the drive wheel and the drive wheel
Calculates the turning center of the body determined from the right road wheel
So that the extension of the center line of the axis of rotation intersects the center of rotation.
Steering control of the right road wheel, the travel angle is zero
In this case, the steering angles of the left and right road wheels should be zero.
And a method for controlling a reach-type forklift.