JP2949181B2 - 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 reach-type forklift capable of steering left and right road wheels, and more particularly, to an extremely small turn in response to a steering wheel operation. The present invention relates to a reach type forklift capable of continuously traversing from time to time.

[0002]

2. Description of the Related Art In recent years, as represented by Japanese Patent Application No. 3-306767 previously proposed by the present applicant, a reach type forklift has been improved and various traveling modes (hereinafter referred to as "traveling modes"). There has been proposed a forklift capable of performing the following.

As shown in FIG. 9, such a forklift F supports a main body 2 and left and right straddle arms 20, 20 projecting from the main body 2 so as to steer road wheels 5, 6, respectively. The section 2 includes a drive wheel 4 that can be steered by a steering wheel 3.

[0004] The drive wheel 4
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.

[0005] A cargo handling 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 by pivot brackets 8 and 9 that can pivot 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, the left and right road wheels 5, 6 can be steered by rotating the steering motors 11, 12, respectively.

The output shafts of the steering motors 11 and 12 have 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.

[0008] Forklift F constructed as described above
Is configured such that a desired traveling mode can be selected by operating the switches A and B of the traveling mode selection device 15. For example, when switch A is selected, FIG.
As shown in FIG. 0, an axis G in which the turning center point P is continuous is in a so-called anti-phase mode in which the axis G is controlled to be located below the left and right road wheels 5 and 6. This control has an effect as if the wheelbase is shortened, and the vehicle can turn with a small turning radius.

On the other hand, when the switch B is selected, as shown in FIG. 11, the steering angle θR of one road wheel 6 is set to about 9
The steering is fixed at 0 degrees, and the steering is controlled so as to be in a traversing mode in which the axis G where the turning center point P is continuous can be parallel to the vehicle center line. By such control, usually, the forklift F
Performs steering with the y direction as the traveling direction. In the traversing mode, Ackerman steering control can be performed with the traveling direction as the x direction.

[0010]

However, since each of the above-mentioned driving modes is controlled independently, for example, it is necessary to perform steering in the traversing mode while driving the forklift F in the opposite phase mode. To do so, the forklift F is once stopped, and the above-described traveling mode selection device 1
An operation of switching 5 is required. In this case, since the driver once releases his / her hand from the steering wheel or the accelerator lever, there is a danger that the operation is temporarily interrupted and the running is not continuous.

The present invention has been devised in view of the above circumstances, and its object is to make it possible to turn with a small turning radius continuously with the operation of the steering wheel, based on the driving feeling of a normal reach-type forklift. Finally, it is an object of the present invention to provide a reach type forklift capable of continuously traversing from straight ahead.

According to the present invention, a drive wheel steerable by a steering wheel and provided with 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. In a reach-type forklift provided with means capable of detecting the steering angle of the drive wheel, an angle having the same magnitude as the steering angle of the drive wheel and having the opposite direction is determined as the steering angle of one road wheel, The drive wheel
An extension of the rotation axis of the road wheel and the rotation axis of the one road wheel
A control device that calculates a turning center point determined from an intersection with an extension line of the road wheel and that performs a steering control so that an extension line of the rotation axis of another road wheel can coincide with the turning center point. It is what it was.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. Note that the configuration of the forklift 1 is the same as that described in FIG.
Since the configuration is the same as that described above, the description here is omitted, and the control device 16 provided in the main body 2 will be described in detail below. However, there is no need to particularly provide the traveling mode selection device 15 as in the related art.

As shown in FIG. 1, the control unit 16 includes an A / D converter, a ROM in which programs and the like are stored, a RAM as a working memory, an MPU as a microprocessor,
It comprises a D / A converter and a motor controller 19, which are connected by a bus line or I / O.

The A / D converter supplies the steering angles θ D,
θR and θL are input. In the A / D converter,
The input signal is converted from an analog signal to a digital signal, and the MPU calculates the steering angles θL and θR of the left and right road wheels 5 and 6 based on the signal. still,
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 determined based on the deviation between the calculation result and the current steering angle detection value. 6 is determined and is converted into an analog signal by a D / A converter.
Are output to the left and right steering motors 11 and 12 respectively.

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, a memory such as a RAM and an I / O and hardware are initialized (S1, S2).

Next, the steering angle θD of the drive wheel 4 of the forklift 1 and the steering angles θL and θR of the left and right road wheels 5 and 6 are read into the RAM (S3 to S).
5). Here, as shown in FIG. 3, the steering angles θL and θR of the left and right road wheels 5 and 6 are respectively determined from the steering centers L and R of the road wheels 5 and 6 by the center of the rotation axis (not shown) of each road wheel. An extension line HL, HR (hereinafter simply referred to as an extension line HL, HR) of the line and an angle formed by the horizontal axis in plan view of FIG. Therefore, in the state illustrated in FIG. 3, the steering angles θ of the left and right road wheels 5 and 6 are set.
L and θR are both zero.

Similarly, the steering angle θD of the drive wheel 4
Is an extension HD of the center line of the rotation axis of the drive wheel 4.
(Hereinafter simply referred to as an extension HD) and an angle formed by the horizontal axis in plan view of FIG. 3, and all angles are considered to be positive in a counterclockwise direction. Therefore, when the steering angle θD of the drive wheel 4 is positive, the forklift is turned rightward, and when the steering angle θD is negative, it is turned leftward.

Next, the MPU determines whether the steering angle θD of the drive wheel 4 of the forklift 1 is zero, that is, whether the vehicle is in a straight running state or a turning state (S6). If the steering angle θD of the drive wheel 4 is zero (Y in S6), the steering angles θL and θR of the left and right road wheels 5, 6 are both set to zero (S7, S8) and output to the motor controller 19 (S9). ). Therefore, the above-described motor controller 1
9, the steering angle θR of the left and right road wheels 5, 6
Feedback control is performed so that both θL become zero.

If the steering angle θD of the drive wheel 4 is not zero (N in S6), that is, if the vehicle is in a turning state, the direction is detected (S10). If the steering angle of the drive wheel 4 is positive as schematically shown in FIG.
0 and Y), the forklift 1 is turned right as described above. In such a case, the steering angle θ of the right road wheel 6
R is determined as the same angle as the steering angle θD of the drive wheel 4 and in the opposite direction (S11).

On the other hand, the steering angle θL of the left road wheel 5
Is determined so that the extension line HL intersects a geometric turning center determined by the steering angles of the drive wheel 4 and the right road wheel 5 (S12).

Similarly, when the forklift 1 is in a left turning state,
That is, when the steering angle θD of the drive wheel 4 is negative as shown in FIG. 8 (N in S10), the steering angle θL of the left road wheel 5 is the same as the steering angle θD of the drive wheel 4. And an angle in the opposite direction (S1).
3).

The steering angle θR of the right road wheel 6 is
It is determined that the extension line HR intersects a geometric turning center point determined by the steering angles of the drive wheel 4 and the left road wheel 5 (S14).

It should be noted that the term "same" in the angle size referred to in the specification of the present application does not mean that the angles are physically completely the same, and in the field of so-called control technology, there is some error. However, it must be understood as what is considered to be the same from a general and common sense point of view.

Considering an orthogonal coordinate system (XY) with the origin (0, 0) being the steering center point D of the drive wheel 4, the coordinates of the steering centers L and R of the left and right road wheels 5 and 6 are respectively defined. (XL, YL), (XR, YL)
As will be briefly described below, means for calculating the steering angle θL of the left road wheel when the drive wheel steering angle is positive and in the state shown in FIG.

The turning center point P1 of the forklift 1 may be obtained by finding the intersection of the extension HD of the drive wheel 4 and the extension HR of the right road wheel 6. Here, the linear equation of the extension HD of the drive wheel 4 in the above-described coordinate system is expressed by Equation 1, and the linear equation of the extension HR of the right road wheel is expressed by Equation 2 by substituting -θD into θR. Can be represented.

(Equation 1)

(Equation 2)

By solving Equations 1 and 2 simultaneously, each coordinate (XP1, YP1) of the turning center point P1 can be obtained, and these coordinates can be expressed by Equations 3 and 4.

(Equation 3)

(Equation 4)

Next, the left road wheel 5 is adjusted so that the extension line HL of the left road wheel 5 coincides with the turning center point P.
Is determined. The steering angle θL of the left road wheel 5 can be obtained by Expression 5 (S11).

(Equation 5)

Similarly, as shown in FIG. 8, when the steering angle θD of the drive wheel 4 is negative, the right road wheel 6
The procedure for calculating the steering angle θR will be described. The straight line equation of the extension line HD of the drive wheel 4 is the same as the above equation 1, but the straight line equation of the extension line HL of the left road wheel can be expressed by equation 6 by substituting -θD for θL. .

(Equation 6)

By solving equations 1 and 6 simultaneously, the coordinates of the turning center point P2 in this case can be expressed by equations 7 and 8.

(Equation 7)

(Equation 8)

Next, the steering angle θR of the right road wheel 6 is determined so that the extension HR of the right road wheel 6 can coincide with the turning center point P2. The steering angle θR of the right road wheel 6 can be obtained by Expression 9 (S14).

(Equation 9)

As described above, the forklift 1 completely satisfies Ackerman-Jantt's theory in which all the extension lines HD, HL and HR intersect at one point, and can maintain a very smooth turning state. The above is the basic concept of the present invention. These will be described based on specific numerical values using a forklift shown in FIG.

First, the dimensions of the forklift 1 are represented by the coordinates of the steering center D of the drive wheel 4 as (0,
0), and the coordinates of the steering centers L and R of the left and right road wheels are (−275, 1350) and (875, 135), respectively.
0). (Unit is mm).

In this case, an angle diagram of the steering angles of both the drive wheel 4 and the left and right road wheels calculated using the above procedure is shown in FIG. 5, and further, a locus diagram of the turning center points P1, P2 of the forklift 1. Are shown in FIG.

As is apparent from FIG. 5, when the steering angle θD of the drive wheel 4 is steered in a positive direction from zero (ie, when the forklift 1 turns right), the steering of the right road wheel 5 is performed. Since the angle θR can be changed linearly in proportion to the steering angle θD of the drive wheel 4, extremely stable and favorable steering can be performed.

In this example, the steering angle θD of the drive wheel 4 is approximately +58 (deg), and the turning center point P coincides with the steering center point R of the right road wheel 6 (ie, the steering of the left road wheel 5). Angle θL = 0), and from this point, the phases of the left and right road wheels 5 and 6 start to be reversed to so-called opposite phases. Further, when the steering angle θD of the drive wheel 4 is increased and θD becomes +90 (deg), the steering angle θR of the right road wheel 6 becomes −90 (deg), and the steering angle θL of the left road wheel becomes +90 (deg). Become.

Such a state is the same as a so-called traversing mode in which the forklift 1 can travel straight while being completely turned sideways. In this case, as is clear from the locus diagram of the turning center point in FIG.
Is at infinity and approaches the straight line K.
Note that the straight line K is a steering center point R of the right road wheel 6, and
It passes through the midpoint of the horizontal displacement with respect to the steering center point D of the drive wheel.

Further, when the steering wheel is turned and the steering angle of the drive wheel is increased in the positive direction, the turning center point approaches the forklift 1 from infinity and gradually moves away from the straight line K. Will be migrated. This means that steering can be performed in a state where the vehicle is facing sideways.

Similarly, the steering angle θD of the drive wheel 4
When the steering wheel is steered from zero to a negative direction (i.e., when the forklift 1 turns left), the same operation as described above can be obtained, and the phase of the left and right road wheels 5 and 6 is such that the steering angle of the drive wheel 4 is approximately-. Inversion starts at 78 (deg), and the same operation as described above is obtained, so that the steering angle θD of the drive wheel 4 becomes −90 (de).
g), the steering angle θL of the left road wheel 5 is +90 (deg)
, The steering angle θR of the right road wheel 6 is also -90 (deg), and the vehicle is in a traversing state.

In such a state, in the trajectory diagram of the turning center point, the turning center point P2 is located at infinity and becomes a curve asymptotic to the straight line T. Further, when the steering wheel is further cut, the forklift 1 approaches the forklift 1 from infinity and moves away from the straight line T to perform steering in a traversing state.

The steering angle θD of the drive wheel 4 is +
The turning center point at the moment when it reaches 90 (deg) or -90 (deg) becomes infinity and causes inconvenience in calculation, but in such a case, the steering angles θL of the left and right road wheels 5 and 6,
The problem is solved by fixing both θR to 90 (deg).

As described in detail above, according to the present invention, the vehicle can be turned from the straight traveling state to the turning state without releasing the handle from the steering wheel.
In addition, since it is possible to shift from the turning state to the traversing state only by operating the steering wheel and it is possible to continuously perform steering even in the traversing state, traveling and cargo handling work in narrow warehouse passages are possible, Can increase efficiency.

The steering mechanism of the road wheel shown in the above embodiment can be variously formed by using various gear mechanisms and transmission means such as links, in addition to the transmission tool such as a belt. Furthermore, a so-called kingpin offset can be provided to reduce the steering torque of the road wheel.

[0047]

According to the present invention, as a result of employing the above method,
A reach-type forklift that can turn with a small turning radius continuously with the steering wheel operation based on the driving feeling of a normal reach-type forklift, and finally enables continuous traversing from straight ahead Can be provided.

As a result, there is no need to temporarily stop the forklift and switch the mode changeover switch or the like when switching the traveling mode as in the prior art, and the traveling mode can be switched only by operating the steering wheel without releasing the hand from the steering wheel. .

Further, since steering in a traversing state is made possible, even when facing a load in front of a narrow warehouse aisle, the load can be moved laterally, and positioning with respect to the load can be easily performed. In addition, the passage area can be reduced, and the space for storing cargo can be improved accordingly.

Also, since control on either one of the left and right road wheels can always be performed in proportion to the steering angle of the drive wheel, the steering angle of one of the road wheels does not change drastically, and extremely stable steering is achieved. Control becomes possible.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device used in the present invention.

FIG. 2 is a flowchart for explaining an embodiment of the present invention.

FIG. 3 is a conceptual diagram of a reach type forklift for explaining a steering angle.

FIG. 4 is a diagram for explaining specific numerical values of a reach type forklift.

FIG. 5 is an angle diagram of a steering angle of a drive wheel and a steering angle of a left and right road wheel.

FIG. 6 is a trajectory diagram of a turning center point of the forklift according to the present invention.

FIG. 7 is a conceptual diagram for explaining a calculation procedure of a turning center point of the reach type forklift.

FIG. 8 is a conceptual diagram for describing a calculation procedure of a turning center point of the reach type forklift.

FIG. 9 is a plan view for explaining a conventional reach-type forklift.

FIG. 10 is a diagram for explaining an anti-phase mode of the reach type forklift.

FIG. 11 is a view for explaining a traversing mode of the reach type forklift.

[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 16 Control device 18 Potentiometer 20 Straddle arm

Claims (1)

(57) [Claims] 1. A drive wheel steerable by a steering wheel, comprising 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 the drive wheel. in reach type forklift shift having a means capable of detecting angular, by the steering angle the same size and of the drive wheel, and determines the angular direction is reversed as the steering angle of over road wheels, the drive Wheel rotation axis
And an extension of the rotation axis of the one road wheel
A reach type forklift comprising a control device for calculating a turning center point determined from an intersection with the steering wheel, and performing a steering control so that an extension of a rotation axis of another road wheel can coincide with the turning center point .