JP2579857B2 - 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.

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 necessary. It cannot be changed. Further, the Ackerman steering and the attitude of the vehicle a can be corrected only when the traveling direction is A or B.

On the other hand, in addition to the above, Japanese Patent Publication No. 63-4449
The multi-directional traveling vehicle shown in No. 1 has been proposed. According to this proposal, the switching lever of the switching mechanism can perform a straight turn, a turn, a super turn, and the like in the front-rear direction and the lateral direction by the backward tilt operation, the forward tilt operation, and the neutral operation of the switching lever, and perform a smooth turn. It is stated that it will be done.

[0006]

However, in the above-described multi-directional traveling vehicle disclosed in Japanese Patent Publication No. 63-44591, a multi-stage gear incorporating a plurality of sector gears, a clutch and the like are used in order to achieve the above object. However, there is a problem that the mechanism is extremely complicated and expensive. As described above, the correction of the attitude of the vehicle can be performed only in the front-rear direction and the left-right direction of the vehicle.
The present invention has been devised in view of the above-described problems, and its object is to simplify the entire steering system based on the driving feeling of a normal reach-type forklift, and to proceed regardless of the vehicle body center line. To provide a reach-type forklift capable of continuously changing the direction in all directions, eliminating the need for conventional mode switching, and correcting the posture of the vehicle body in all traveling directions. It is in.

[0007]

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 a travel angle input means for instructing a travel angle of the vehicle body is provided, and the drive wheel passes through a steering center of each of the left and right road wheels. Assuming an axis on which the turning centers are arranged, an axis on which the turning centers are arranged by the advancing angle instructed by the advancing angle input means is defined by an axis connecting the steering centers of the left and right road wheels and a steering center of each of the left and right road wheels. Rotational movement about the center of a circle tangent to each of the axes drawn along the vehicle body center line, and an axis on which the turning centers after the rotation are aligned, From the steering center of the drive wheel, the intersection point with the axis drawn along the steering angle of the drive wheel is set as the turning center, and the axis connecting the turning center and the steering center of each of the left and right road wheels is determined. The angle formed between the axis connecting the turning center and the steering center of each of the left and right road wheels and the axis where the turning centers before rotation are aligned is to be steered as the steering angle of the left and right road wheels. It is.

[0008]

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 10 and 10 protruding from the main body 2 so that the load wheels 12L and 12R can be steered. A steerable drive wheel 11 is provided.

Further, between the straddle arms 10, 10, it is possible to slide back and forth and
A mast 3 for locking a cargo handling device 4 such as a fork or various attachments so as to be able to move up and down is provided.

The main body 2 has a hydraulic operation lever 7 for operating the cargo handling device 4, an accelerator command to a traveling motor for rotating and driving the drive wheel 11, and a traveling operation for instructing a traveling angle of the forklift 1. A lever 8 (described later) is provided.

Next, the steering mechanism of the road wheel will be described in detail with reference to FIGS. The left load wheel 12 </ b> L is rotatably supported on a support shaft 14 via a bearing, and the support shaft 14 is fixed to the bracket 13. On the upper surface of the bracket 13, a steering shaft 16L is rotatably supported by the straddle arm 10 via a bearing 21.

A fan-shaped spur gear 20 is fixed to the inner end of the bracket 13 with bolts 23, and a spur gear 19 meshing with the fan-shaped spur gear 20 is fitted into the drive shaft 17. The drive shaft 17 is provided with the steering shaft 16L.
And are rotatably supported by the boss 22,
A timing pulley 18 is fixed to the upper end.

A steering motor 34L is fixed in the straddle arm 10. A pinion 33 has a single-stage reduction gear 31, a coaxially formed idle gear 32 and a two-stage reduction gear 30, and a rotating shaft 29L. Can be rotated. Further, a spur gear 26 is fixed to the upper part of the rotating shaft 29, and the detection gear 2 of the potentiometer 28 is
7, so that the steering angle of the road wheel 12L can be detected.

A timing pulley 25 is fixed to the upper end of the rotary shaft 29, and the torque of the steering motor 34L is transmitted to the timing pulley 18 of the drive shaft 17 via a timing belt 35, so that the load wheel 1
2L can be steered. As shown in FIG. 2, the center line of the road wheel 12L and the steering shaft 16L
The center of turning is eccentric by the distance e, so that the driving torque during steering can be reduced. The other road wheel 12R also has the same configuration, and is configured symmetrically with respect to the vehicle body center line of the forklift 1.

Next, the traveling operation lever will be described with reference to FIG. The traveling operation lever 8 is provided at one corner of the main body 2 of the forklift 1, and uses a so-called two-dimensional joystick lever that can be tilted in any of the front-back direction, the left-right direction, and the oblique direction. The component is taken out as an accelerator command for instructing the traveling speed, and the lateral displacement component is taken out as an angular velocity command for the advancing angle (described later) of the forklift 1 and is subjected to control described later. still,
As described above, the accelerator command and the angular velocity command of the advance angle should not be interpreted as being limited to a configuration capable of integrally indicating them, and a lever or the like may be separately provided so that both can be individually specified.

As shown in FIG. 6, the drive wheel 11 is configured such that the steering torque applied to the steering wheel 6 is transmitted from a sprocket 46 to a sprocket 44 via a chain 45.
And the input shaft 4 fixed to the sprocket 44
7. Steering can be performed by rotating the turning gear 37 transmitted to the output shaft 48, the universal joint 42, the drive shaft 39, and the drive gear 38 via the steering torque detector 43.

The turning gear 37 has a drive wheel 1
1 is fixedly mounted on a swivel gear case 36. Further, the steering torque detector 43 detects a relative twist between the input shaft 47 and the output shaft 48, and drives and rotates the power steering motor 41 in response thereto, via the gear case 40 having a built-in reduction mechanism. The assist torque is the drive shaft 39
And the steering torque is reduced. Also,
The turning gear 37 is meshed with a detection gear 51 of a potentiometer 50 so that the steering angle of the drive wheel 11 can be detected. The travel motor 49 is controlled based on an accelerator command of the travel operation lever 8.
Is driven to rotate, and the drive wheel 11 can be driven to rotate via a speed reducer (not shown) built in the turning gear case 36.

Next, the basic concept of the present invention will be described with reference to FIGS. In FIG. 9, the steering center of the drive wheel 11 is O, the left and right road wheels 12
Let G be the axis on which the turning centers connecting the steering centers M and N of L and 12R are arranged. The left and right road wheels 12L, 12R
The steering centers M, N of the steering shafts 16L, 1
It can be considered as the center of 6R. Here, forklift 1
The traveling direction is defined as a traveling direction, and the traveling angle is defined as an angle between the traveling direction and the vehicle body center line CL. The steering angles θL, θR of the left and right road wheels 12L, 12R are respectively the axis G and the axes (H, I in FIG. 9) drawn from the steering centers M, N of the road wheels 12L, 12R to the centers of the respective wheels. ).
Further, the steering angle θ1 of the drive wheel 11 refers to an angle formed by an axis parallel to the x-axis and an axis (F in FIG. 9) drawn from the steering center O to the wheel center. Further, the description will be made assuming that the traveling angle θ0 is zero when it is along the vehicle body center line CL.

FIG. 10 shows an initial state in which the steering angles of the left and right road wheels 12L, 12R and the drive wheel 11 are zero, and the traveling angle of the forklift 1 is also zero.

Next, the axis G on which the turning centers are lined up by the advancing angle input by the traveling operation lever 8 is set to the axis G
And the center of a circle (hereinafter, simply referred to as a representative point E) tangent to each of the axes J and K drawn from the steering center of each of the right and left road wheels along the vehicle body center line (hereinafter referred to simply as a representative point E). In the case of (1), the traveling angle is zero, so that the state remains as it is.

Further, the intersection of an axis F drawn from the steering center O of the drive wheel 11 along the steering angle of the drive wheel 11 and an axis G on which the turning center is arranged is defined as a turning center P (in FIG. (Shown). In this case, since the steering angle of the drive wheel 11 is zero,
The turning center P (not shown) is theoretically a point at infinity on the axis G where the turning centers are arranged.

Also, the axes H and I connecting the turning center P and the steering centers M and N of the left and right road wheels 12L and 12R form an angle with the axis G where the turning centers before the rotational movement are formed. In this case, the steering angles of the left and right road wheels 12L and 12R are both zero, and the vehicle travels straight when an accelerator command is issued from the traveling operation lever 8. .

Next, the case where the traveling angle is zero and the steering angle of the drive wheel is θ1 will be described with reference to FIG. As in the case described above, since the advancing angle is zero, the axis G on which the turning centers are arranged does not change. Further, an intersection point between an axis F drawn along the steering angle θ1 of the drive wheel 11 from the steering center O of the drive wheel 11 and an axis G on which the turning centers are arranged is determined, and this point becomes the turning center P.

Here, similarly to the above, the axes H and I connecting the turning center P and the steering centers M and N of the left and right road wheels 12L and 12R are the axes G on which the turning centers before the rotational movement are arranged. The corners are both zero and the left and right road wheels 1
Both 2L and 12R are not steered.

From the above, it is apparent that the traveling angle is zero,
That is, when the vehicle is along the vehicle center line CL, the left and right road wheels 12L and 12R are not steered, and remain in a straight running state. Can be

Next, from the state shown in FIG.
When only the advancing angle is given, the state shown in FIG. 12 is obtained. In this case, the axis G on which the turning centers are aligned is referred to as the traveling angle θ0
Is rotated only around the representative point E, and an axis D on which the turning centers after rotation are aligned is determined. From the axis D on which the turning centers are aligned and the steering center O of the drive wheel 11, the steering angle of the drive wheel 11 is determined. The intersection with the axis F drawn along θ1 is the turning center P.

Further, the axes H and I connecting the turning center P and the steering centers M and N of the left and right road wheels 12L and 12R respectively form an angle θL and an angle GL with an axis G on which the turning centers before the rotational movement are arranged. θR is set to the left and right road wheels 12L and 12R.
Is determined and controlled.

Next, as shown in FIG. 13, when the advancing angle is made equal to the steering angle of the drive wheel 11, that is, when θ0 = θ1, the axis G on which the turning centers are arranged is set to the representative point E in the same manner as described above. Rotate and move it to the center by the advance angle θ0,
An axis D on which the turning centers after rotation are arranged is determined, and an axis F drawn along the steering angle θ1 of the drive wheel 11 from the axis D on which the turning centers are arranged and the steering center of the drive wheel 11.
Is the turning center P, but in this example, the axis D on which the turning centers are arranged and the axis F drawn from the steering center of the drive wheel 11 along the steering angle θ1 of the drive wheel 11 are parallel. And the turning center P (not shown) is theoretically at infinity with respect to the axis D on which the turning centers are arranged.

Therefore, the axes H and I connecting the turning center P and the steering centers M and N of the left and right road wheels 12L and 12R respectively form the angles θL and θR is equal to the traveling angle θ0 and the steering angle θ1 of the drive wheel. In such a situation,
The so-called skew traveling, in which the forklift 1 travels along the advancing angle θ0 without changing the posture of the vehicle body, can be performed.

The above is the basic concept of the present invention. By performing the above-described control, Ackerman steering can be performed in all running states. By giving a command of the advance angle, for example, in the state shown in FIG. 12, the vehicle center line CL of the forklift 1 is vertical in the figure, but as if the vehicle center line CL
, The steering by the drive wheel 11 can be performed. Therefore, no matter what direction the vehicle center line CL of the forklift 1 actually is, an arbitrary advance angle is given, and the attitude of the forklift 1 can be corrected based on this advance angle.

Next, means for embodying the above concept will be described in detail with reference to a control block diagram shown in FIG.

An accelerator signal, which is a displacement component in the front-rear direction, and an angular velocity signal of a traveling angle, which is displacement in the left-right direction, are separated and taken out from the traveling operation lever 8 and input to the A / D converter 53. . Similarly, the steering angle signal of the drive wheel 11 and the left and right road wheels 12L, 1L,
The 2R steering angle signal is output to each of the potentiometers 50 and 28.
R and 28L are input to the A / D converter 53.
The A / D converter 53 converts the input signal from an analog signal to a digital signal, and the accelerator signal is output from the MPU via the bus line to the traveling motor drive circuit 60 such as a chopper circuit.
Drive.

After the angular velocity signal of the traveling angle is converted into a digital signal, it is used for calculating the steering angle of the left and right road wheels 12L, 12R based on the steering angle signal of the drive wheel 11. Note that this calculation processing procedure
, Which will be described later.

Further, the calculation results of the steering angles of the road wheels 12L, 12R calculated by the MPU described above are based on the deviation between the calculation results and the current steering angle detection value, based on the left and right road wheels 12L, 12L. After the turning speed of the 12R is determined and converted into an analog signal by the D / A converter 58,
Through the logic circuit 59, the left and right steering motors 34L,
It is output to each of 34R.

The steering torque signal of the steering torque detector 43 is input to the A / D converter 53, converted into a digital signal, and the MPU determines an assist torque corresponding to the steering signal. The power steering motor 41 is driven to rotate via a circuit 59. still,
A control signal is input from the MPU to the logic circuit 59, and controls such as forward rotation, reverse rotation, and forced lock of the steering motors 34L and 34R and the power steering motor 41 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
And the like are initialized (S1, S2), and initialization is performed to make the traveling angle of the forklift 1 zero (S3).

Next, the steering angle of the drive wheel 11 and the advancing angle of the forklift 1 input from the traveling operation lever 8 are read (S4, S5). Further, it reads the accelerator command and outputs it to the traveling motor drive circuit 60 (S
6, S7).

Next, the left and right road wheels 12L, 1L, which are determined by the advancing angle and the steering angle of the drive wheel 11.
The 2R steering angle is calculated (S8). Further, the steering torque signal is read, and the assist torque of the steering wheel 6 is calculated and output based on the steering torque signal (S9, S10, S11).

Next, the current left road wheel 12L
Is read via the A / D converter 53 (S
12) The speed at which the road wheel 12L is steered is calculated based on the deviation of the steering angle calculation value of the left road wheel 12L calculated in step S8 described above (S1).
3), output the steering speed to the D / A converter 58 (S14).

As for the right road wheel 12R,
The turning speed is output as in the case of the left side described above (S15).
To S17), a loop process for reading the current steering angle of the drive wheel 11 is performed again (S4). This processing procedure is stored in the ROM, and is performed for each sampling cycle.

Next, among the processing procedures of the MPU, the procedure for calculating the steering angles of the left and right road wheels 12L and 12R performed in step S8 will be described in detail with reference to FIG. Now, as shown in the figure, the traveling angle of the forklift 1 is θ0,
The steering angle of the drive wheel 11 is assumed to be θ1. Consider the orthogonal coordinate axes (xy) where the representative point E is the origin and the y-axis is coincident with the vehicle body center line CL.

Further, the left and right road wheels 12L, 1L
The axis on which the turning centers connecting the steering centers M and N of the 2R are arranged is G, and the axis G is rotated about the representative point E by the advancing angle θ0 as described above. D is determined, and the intersection of the axis D and the axis F drawn from the steering center O of the drive wheel 11 along the steering angle θ1 of the drive wheel 11 is defined as the turning center P.

First, consider a transformed coordinate axis (XY) obtained by rotating and moving the above-described orthogonal coordinate axis (xy) by the advancing angle θ0, and consider the left and right road wheels 12L, 12R in the transformed coordinate axis (XY). The coordinates of the steering centers M and N are determined.

The steering center M of the left road wheel 12L
(XL, YL) can be obtained by Expressions 1 and 2.

(Equation 1)

(Equation 2)

Where W is the left and right road wheels 12L,
Distances from the steering centers M and N of 12R to the y-axis, and S and L are horizontal and vertical distances from the representative point E to the steering center O of the drive wheel 11, respectively.

Similarly, the coordinates (XR, YR) of the steering center N of the right road wheel 12R can be obtained by Expressions 3 and 4.

(Equation 3)

(Equation 4)

Further, the coordinates (Xo, Yo) of the steering center O of the drive wheel 11 can be obtained by Expressions 5 and 6.

(Equation 5)

(Equation 6)

Next, the coordinates (XP, YP) of the turning center P on the transformed coordinate axes (XY) are calculated. It is clear that YP = W for YP. Calculate.

(Equation 7)

The tangent of the difference between θL and θ0 is given by equation (8).

(Equation 8)

From equation (8), the steering angle θL of the left road wheel 12L can be obtained from equation (9).

(Equation 9)

Similarly, the steering angle θR of the right road wheel 12R can be obtained by Expression 10.

(Equation 10)

The steering angles .theta.L and .theta.R of the left and right road wheels 12L and 12R obtained by the above calculation are output, and each road wheel is steered.

However, in Equations 9 and 10, (θ1−θ
If (0) becomes π / 2, the tangent becomes infinity, which is inconvenient for the calculation in the MPU. Therefore, the steering angle θ1 of the drive wheel may be limited in advance to, for example, a range shown in Expression 11. good.

[Equation 11]

That is, the range of the steering angle θ1 at which the drive wheel can be steered may be limited by the advancing angle θ0 specified by the traveling operation lever 8.
By expanding and rearranging, (θ1−θ0) does not always take a value of π / 2 as shown in Expression 12.

(Equation 12)

Although described in detail above, the present invention should not be construed as being limited to the above embodiment. For example, the lateral displacement of the travel operation lever 8 is set as the angular velocity command of the traveling angle,
It may be configured to give a direct advance angle command,
The road wheel steering mechanism may be configured using transmission means such as various gears and links in addition to the timing belt.

[0056]

According to the present invention, as a result of employing the above method,
In all running states, Ackerman steering is possible, and there is no discontinuous operation such as mode switching.
Also, since it is possible to give a command of the advance angle continuously in all directions, no matter which direction the center line of the body of the forklift is actually facing, by giving an arbitrary advance angle, in all the advance directions, The posture of the forklift can be corrected. Further, the steering mechanism of the road wheel does not require any complicated steering unit as in the related art, so that an extremely simplified steering mechanism can be used.

[Brief description of the drawings]

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

FIG. 2 is a front view illustrating a road wheel.

FIG. 3 is a side view illustrating a road wheel.

FIG. 4 is a plan view illustrating a road wheel.

FIG. 5 is a perspective view for explaining a traveling operation lever.

FIG. 6 is a diagram for explaining a steering mechanism of a drive wheel.

FIG. 7 is a control block diagram of the present invention.

FIG. 8 is a flowchart of the present invention.

FIG. 9 is a diagram for explaining a method of calculating a steering angle of a road wheel.

FIG. 10 is a diagram for explaining a basic concept of the present invention.

FIG. 11 is a diagram for explaining a basic concept of the present invention.

FIG. 12 is a diagram for explaining a basic concept of the present invention.

FIG. 13 is a diagram for explaining a basic concept 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 6 Handle 10 Straddle arm 11 Drive wheel 12L Road wheel 12R Road wheel 28L Potentiometer 28R Potentiometer 34L Steering motor 34R Steering motor 50 Potentiometer

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, provided with a traveling angle input means for instructing a traveling angle of a vehicle body, and assuming an axis on which turning centers passing through steering centers of the left and right road wheels are aligned. An axis on which the turning centers are arranged by the traveling angle designated by the traveling angle input means is drawn along the vehicle body center line from the axis connecting the steering centers of the left and right road wheels and the steering center of each of the left and right road wheels. Rotational movement around the center of a circle that is in contact with each axis, and the axis on which the rotation center after the rotation is aligned, and the drive wheel is being steered From the heart, the intersection of an axis drawn along the steering angle of the drive wheel is defined as a turning center, and an axis connecting the turning center and the steering centers of the left and right road wheels is determined. The reach type forklift is characterized in that the angle between the axis connecting the steering centers of the left and right road wheels and the axis where the turning centers before rotation are aligned is steered as the steering angle of the left and right road wheels. Control method.