JP3695743B2 - forklift - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for positioning a fork pallet including a tilt operation.
[0002]
[Prior art]
Conventionally, an example of a forklift is shown in FIG. This is because a pair of outer masts 2a are erected on a vehicle body 1 having front and rear wheels 1a and 1b so as to be tiltable about an axis O concentric with the front wheels 1a, and a pair of inner masts 2b is provided on both outer masts 2a. A fork 4 is attached to a lifting body 3 that can be moved up and down via a lift, and a lift cylinder 5 for raising and lowering the lifting body 3 and the fork 4 and a tilt cylinder 6 for tilting the masts 2a and 2b are provided. ing. Further, a pendulum tilt angle detector 7 is disposed on the lifting body 3 and is wound around a rope 9 such as a chain wound between wheels 8 provided at the upper and lower ends of the inner mast 2b and connected to the lifting body 3 at both ends. A fork lift detector 10 composed of a matching potentiometer or the like is attached to the inner mast 2b. Further, a steering lever 1 a for operating the handle 11, the lift cylinder 5, and a tilt lever 12 b for operating the tilt cylinder 6 are provided in the control section 1 a of the vehicle body 1.
[0003]
In the above configuration, for example, when the work W on the pallet P stored in the storage space of the storage 13 is unloaded, the vehicle body 1 is moved to approach the work W and the lift lever 12a is operated to expand and contract the lift cylinder 5. By driving, the fork 4 is moved up and down and positioned on the pallet P, and then the vehicle body 1 is moved forward to insert the fork 4 into the pallet P. The lift cylinder 5 is driven to extend and the fork 4 passes through the pallet P. The workpiece W is lifted, and then the vehicle body 1 is moved backward, and the tilt cylinder 12 is operated to reduce the tilt cylinder 6 so that the masts 2a and 2b are tilted backward by a predetermined angle θ1 to raise and lower the workpiece W. 3 is pressed against the backrest 3a, the vehicle body 1 is run, and the workpiece W is carried out to a predetermined position.
[0004]
[Problems to be solved by the invention]
In the above conventional configuration, as shown by the solid line in FIG. 5, the lift cylinder 5 is extended and retracted while the masts 2a and 2b are tilted rearward to align the fork tip 4a with the pallet P, and then to FIG. As indicated by the phantom line, when the tilt cylinder 6 is driven to extend and the masts 2a and 2b are tilted to bring the fork 4 into a horizontal state, the fork tip 4a is displaced by a predetermined interval t from the state before the tilt operation. In this case, it is necessary for the operator to again drive the lift cylinder 5 to lift the fork 4 by lift operation, which is troublesome.
[0005]
Further, since the fork tip 4a is pushed out by the tilting operation, when the fork tip 4a is approaching the hangar 13, the fork tip 4a causes the receiving shelf 13a of the hangar 13 and the work W to be struck, and the vehicle There was a risk of shock to the operator through the load, collapse of the workpiece W, and damage.
[0006]
An object of the present invention is to provide a forklift capable of maintaining the lifted height of a fork tip substantially constant during a tilt operation in view of the above-described conventional drawbacks.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a mast that is erected on a vehicle body and that can be tilted by a tilt drive device, and an elevator that is disposed on the mast and can be lifted and lowered by a lift drive device. A tilt angle detecting device for detecting a tilt angle of the mast and a tilt angle of the mast detected by the tilt angle detecting device in a forklift comprising a body and a fork disposed on the lifting body A fork tip lift calculating device for detecting the tip lift of the fork, a storage device for storing the fork tip lift before the tilt operation of the mast detected by the fork tip lift calculating device, A fork tip lifting height control device for storing the fork tip lifting height immediately before the tilt stop, which is stored in the storage device, before the tilt operation. [0008], wherein the door
The present invention also provides a mast that is erected on the vehicle body, a lifting body that is disposed on the mast and that can be moved up and down by a lifting drive device, and a tilt drive device that is disposed on the lift body. In a forklift comprising a fork made to be tiltable,
A tilt angle detection device for detecting a tilt angle of the fork, a fork tip height calculation device for detecting a tip lift height of the fork corresponding to the tilt angle of the fork detected by the tilt angle detection device, and the fork A storage device for storing the fork tip lifting height before the tilt operation of the fork detected by the tip lifting height computing device, and a fork tip lifting height immediately before the fork tilt stop is stored in the storage device. And a fork tip lift control device for raising the fork tip lift before operation.
[0009]
Another feature of the present invention is that the fork tip lift control device repeatedly reads the fork tip lift during the tilt operation of the mast detected by the fork tip lift calculation device, An arithmetic device that repeatedly calculates the difference in lift between the fork tip lift read by the reading device and the fork tip lift before the tilt operation stored in the storage device, and the arithmetic device And a lift command device that continuously lifts and lowers the lift drive device so that the difference in lift is zero.
[0010]
Another feature of the present invention is that the fork tip lift control device repeatedly reads the fork tip lift during the tilt operation of the mast detected by the fork tip lift calculation device, An arithmetic device for calculating a difference in lift between the fork tip lift height read last before the tilt stop by the reading device and a fork tip lift height before the tilt operation stored in the storage device; and And a lift command device that lifts and lowers the lift drive device so that the calculated height difference becomes zero.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a counterbalance type forklift according to an embodiment of the present invention. The lift height Ho of the fork tip 4a before the tilting operation is calculated, and the lift height H of the fork tip 4a is calculated during the tilting operation. The operation of the lift cylinder 5 was controlled such that the calculation was repeated, and the lift height H calculated repeatedly matched the lift height Ho. Since the configuration other than the above is substantially the same as that of the conventional example shown in FIG.
[0012]
FIG. 2 shows the control action of the control unit 15 comprising a microcomputer for controlling various devices of the forklift. Based on detection signals from the tilt angle detector 7 and the fork lift height detector 10, before the tilt operation. The lift height Ho of the fork tip 4a is calculated and stored in the memory 16, which is a storage device, and the lift cylinder proportional electromagnetic control valve 17 is controlled based on the lift height Ho stored in the memory 16. is there. That is, the control unit 15 functions as a device that calculates the lift height Ho of the fork tip 4a or repeatedly calculates the lift height H, and a fork tip lift height calculation device. The control unit 15 also functions as a device for variably controlling the lift height H of the fork tip 4a and a fork tip lift control device. Further, the control unit 15 functions as an arithmetic device that repeatedly calculates a difference in height between the lift height H of the fork tip 4 a and the lift height Ho stored in the memory 16. The control unit 15 also functions as a lift command device that issues a lift command to a lift drive device for lifting the fork 4. Further, the control unit 15 issues a drive command to the lift cylinder proportional electromagnetic control valve 17 and the hydraulic motor 18 for sending pressure oil to the lift cylinder 5 by operating the lift lever 12a.
[0013]
Explaining the principle of the present invention, as shown by a solid line in FIG. 3, the lift height Ho of the fork tip 4a when the masts 2a and 2b are tilted backward by a predetermined angle θ1 is Ho = L × sin (θ1 + θf). expressed.
[0014]
Note that L = d / cos θf and θf = arc tan h / d. Where d is the horizontal distance from the axial center O when the fork 4 is leveled to the fork tip 4a, θf is the inclination angle of the fork tip 4a when the fork 4 is leveled, and h is the level when the fork 4 is leveled The vertical distance from the axial center O to the fork tip 4a is detected by the fork height detector 10. Θ1 is the tilt angle of the masts 2a and 2b and is detected by the tilt angle detector 7.
[0015]
The lift height H of the fork tip 4a, which is repeatedly calculated during the tilt operation, is also expressed by the same formula as the lift height Ho.
[0016]
The output value S of the lift cylinder proportional electromagnetic control valve 17 is expressed by S = a × (H−Ho). Note that a is a gain.
[0017]
The control action of the control unit 15 will be described with reference to FIG. As shown in FIG. 1, the case where the forks 4 are leveled from the state in which the masts 2a and 2b are tilted in advance by a predetermined angle θ1 and the forks 4 are inclined rearward will be described as an example. In step S1, it is determined whether or not the lift lever 12a is ON (operated). If YES, there is no control of the present invention and the lift cylinder 5 is simply driven to raise and lower the fork 4. If NO, the process proceeds to step S2, and it is determined whether or not the tilt lever 12b is turned on (operated). If NO, the process proceeds to step S3, and if there is a tilt operation (corresponding to when step S7 is executed), the tilt stop is performed. If the tilt is stopped, the tilt stop is performed as it is. Next, the process proceeds to step S4, the lift height Ho of the fork tip 4a is calculated, and the calculation result Ho is stored (step S5). If there is a lift operation (corresponding to the execution of step S11), the lift is stopped. If the lift is stopped, the lift is stopped as it is (step S6).
[0018]
On the other hand, if YES in step S2, the tilt operation corresponding to the tilt operation is performed (step S7), and the lift height H of the fork tip 4a during the tilt operation is calculated (step S8). Next, the process proceeds to step S9, where the output value S is calculated, and the lift height H of the fork tip 4a is made to coincide with the lift height Ho by a lift operation. In step S2, if the tilt lever 12b is continuously turned on, steps S7 to S9 are repeated, and the lift height H of the fork tip 4a is continuously maintained during the tilt operation. When the tilt lever 12b is not turned on, the process proceeds to step S3 described above.
[0019]
According to the above configuration, since the lifting height H of the fork tip 4a is kept substantially constant with reference to the lifting height Ho of the fork tip 4a before the tilting operation (H = Ho), the tilting operation is completed as in the prior art. Thereafter, it is not necessary for the operator to drive the lift cylinder 5 again to adjust the lift height H of the fork tip 4a, and the operation is easy.
[0020]
Further, even if the fork tip 4a is pushed out by performing a tilt operation with the fork tip 4a approaching the pallet P stored in the storage 13, for example, the lift height H of the fork tip 4a is substantially constant. The fork tip 4a is inserted into the pallet P, and the receiving shelf 13a and the workpiece W of the storage 13 are not struck by the fork tip 4a as in the prior art, and the cargo handling operation can be performed safely.
[0021]
In the above embodiment, the case where the fork 4 is leveled from the state in which the masts 2a and 2b are tilted backward by a predetermined angle θ1 and the fork 4 is inclined has been described as an example, but the present invention is not limited thereto. However, the present invention can also be applied to the case where the masts 2a and 2b are tilted by tilting the masts 2a and 2b by a predetermined angle θ1 (or θ2) from the state where the masts 2a and 2b are in a vertical state and the fork 4 is in a horizontal state. . Further, the present invention can also be applied to a case where the fork 4 is leveled from a state where the mast 2a, 2b is tilted forward by a predetermined angle θ2 and the fork 4 is inclined.
[0022]
The above describes the control in which the lift operation is continuously performed during the tilt operation and the lift height H of the fork tip 4a is always kept at the lift height Ho before the tilt operation. Next, a description will be given of the control in which the lift height H of the fork tip 4a immediately before the tilt stop is made to be the lift height Ho before the tilt operation without performing the lift operation during the lift operation. Referring to FIG. 5, in step S1, it is determined whether or not the lift lever 12a is turned on (operated). If YES, there is no control of the present invention and the lift cylinder 5 is simply driven to raise and lower the fork 4. If NO, the process proceeds to step S2, and it is determined whether or not the tilt lever 12b is turned on (operated). If NO, the process proceeds to step S3, and if there is a tilt operation (corresponding to when step S7 is executed), the tilt stop is performed. If the tilt is stopped, the tilt stop is performed as it is. Next, the process proceeds to step S4, the lift height Ho of the fork tip 4a is calculated, and the calculation result Ho is stored (step S5). If there is a lift operation (corresponding to the execution of step S11), the lift is stopped. If the lift is stopped, the lift is stopped as it is (step S6).
[0023]
On the other hand, if YES in step S2, the tilt operation corresponding to the tilt operation is performed (step S7), and the lift height H of the fork tip 4a during the tilt operation is calculated (step S8). Next, in step S9, it is determined whether or not the tilt lever 12b is ON. If YES, the tilt operation (step S7) is performed, and if NO, the process proceeds to step S10, and from the lifting height H that is the last calculated value in step S8. The output value S is calculated, and the lift height H of the fork tip 4a is made to coincide with the lift height Ho by a lift operation. That is, in the control of this example, the operation of making the lift height H of the fork tip 4a immediately before the tilt stop coincide with the lift height Ho is performed only once.
[0024]
According to the above configuration, the lift height H of the fork tip 4a is set to the lift height Ho before the tilt operation after the tilt stop, based on the lift height Ho of the fork tip 4a before the tilt operation. After the operation is completed, it is not necessary for the operator to drive the lift cylinder 5 again to adjust the lift height H of the fork tip 4a, and the operation is easy.
[0025]
The above has described two examples of the tilt operation of the masts 2a and 2b that are generally applied to counterbalance forklifts. The present invention is not limited to this, and the masts 2a and 2b are not tilted, and can be applied to the case where the fork 4 is tilted. Specifically, referring to FIG. 6, the reach-type forklift has a structure in which the masts 2 a and 2 b are not tilted but only the fork 4 is tilted by the tilt cylinder 19 (see a one-dot chain line in FIG. 6). Also in this case, similarly to the control described above, the lift height Ho of the fork tip 4a before the tilt operation is stored, and the lift height H of the fork tip 4a during the tilt operation and immediately before the tilt stop is set to Ho. The lift height Ho of the fork tip 4a before operation is stored, and control is performed so that the lift height H of the fork tip 4a immediately before the tilt stop is set to Ho.
[0026]
【The invention's effect】
According to the first or second aspect of the present invention, the lift of the fork tip is kept constant by controlling the drive of the lift cylinder based on the lift of the fork tip before the tilting operation. Therefore, unlike the conventional case, after the tilting operation is completed, it is not necessary for the operator to drive the lift cylinder again to adjust the lift height of the fork tip, and operation is easy.
[0027]
According to the invention described in claim 3, even if the fork tip is pushed out by performing a tilt operation in a state where the fork tip is brought close to, for example, a pallet housed in a hangar, the lift height of the fork tip is substantially constant. Therefore, the tip of the fork is inserted into the pallet, and unlike the conventional case, the receiving shelf of the hangar and the workpiece are not pushed by the fork tip, and the cargo handling operation can be performed safely.
[0028]
In the invention according to claim 4, since the fork tip lift after the tilt operation can be the lift before the tilt operation, the lift operation after the tilt operation by the operator can be eliminated, and the lift work of the operator can be reduced. be able to.
[Brief description of the drawings]
FIG. 1 is a side view of a counterbalance forklift according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a control action of the control unit.
FIG. 3 is a diagram illustrating the principle of the present invention.
FIG. 4 is a flowchart illustrating an example of control by the control unit.
FIG. 5 is a flowchart illustrating another example of control of the control unit.
FIG. 6 is a side view of a reach-type forklift that is another embodiment of the present invention.
FIG. 7 is a side view showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Car body 2a Outer mast 2b Inner mast 3 Lifting body 4 Fork 4a Fork tip 5 Lift cylinder 6 Tilt cylinder 7 Tilt angle detector 10 Fork lift detector 15 Control part 16 Memory 17 Proportional electromagnetic control valve Ho for lift cylinder Before tilt operation Fork tip lift height H Fork tip lift height during tilting

Claims (4)

A mast standing on the vehicle body and capable of being tilted by a tilt drive device, a lift body disposed on the mast and capable of being lifted and lowered by a lift drive device, and disposed on the lift body A forklift comprising a fork,
A tilt angle detection device for detecting a tilt angle of the mast, a fork tip height calculation device for calculating a tip lift height of the fork corresponding to the tilt angle of the mast detected by the tilt angle detection device, and the fork A storage device for storing the lift height of the fork tip before the tilt operation of the mast calculated by the tip height calculation device, and a tilt operation before the tilt motion of the fork tip just before the tilt stop of the mast is stored in the storage device. And a fork tip lifting control device for lifting the fork tip. A mast erected on the vehicle body, an elevating body disposed on the mast and disposed so as to be movable up and down by the elevating drive device, and disposed on the elevating body and tiltable by the tilt drive device. A forklift comprising a fork,
A tilt angle detecting device for detecting a tilt angle of the fork, a fork tip lifting height calculating device for calculating a tip lift height of the fork corresponding to the tilt angle of the fork detected by the tilt angle detecting device, and the fork A storage device for storing the fork tip lift before the tilt operation of the fork calculated by the tip lift calculation device, and a fork tip lift immediately before the fork tilt stop is stored in the tilt device. A fork lift control device for lifting the fork tip before operation. The fork tip lift control device repeatedly reads the fork tip lift during the tilt operation of the mast detected by the fork tip lift calculation device, and the fork tip lift read by the reading device. An arithmetic unit that repeatedly calculates the difference in height between the height and the fork tip lift before tilt operation stored in the storage device, and the elevation so that the difference in height calculated by the arithmetic device is zero The forklift according to claim 1, further comprising a lift command device that continuously lifts and lowers the drive device. The fork tip lift control device is a reading device that repeatedly reads the fork tip lift during the tilting operation of the mast calculated by the fork tip lift calculation device, and at the end immediately before the tilt stop by the reading device. An arithmetic device for calculating a lift difference between the read fork tip lift and the fork tip lift before the tilt operation stored in the storage device, and the lift difference calculated by the calculator is 0 The forklift according to claim 1, further comprising a lift command device that lifts and lowers the lift drive device.

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