JP2001301516A - Cargo receiving platform elevating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrences of impact during starting and stoppage of a cargo receiving platform. SOLUTION: This cargo receiving platform elevating device 10 is provided with a lift member 11 supported by a load-carrying platform 2, a load receiving platform 12 supported by the lift member 11, a lift cylinder device 15 elevating the lift member 11, and an oil passage 19 supplying pressure oil of a hydraulic pump 17 to the lift cylinder device 15 and draining it therefrom, and a valve 23 for lifting controlling the lift cylinder device 15 is interposed in the oil passage 19 to the lift cylinder device 15. A drain oil passage 27 conducting the pressure oil of the hydraulic pump 17 and the pressure oil of the lift cylinder device 15 to a tank 18 is branched from the oil passage 19, and a flow proportional valve 28 is interposed in the drain oil passage 27. By this, a drain flow rate of the lift cylinder device is gradually increased by the flow proportional valve for gently starting in a lowering operation initial stage and a supply flow rate of the lift cylinder device is gradually decreased by the flow proportional valve for gently stopping in an operation terminal stage for preventing impacts during starting and stoppage of lowering of the load receiving platform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loading / unloading device, and more particularly to a buffering technology at the time of starting and stopping the loading device. Effective technology.

[0002]

2. Description of the Related Art In order to facilitate the lifting and lowering of luggage with respect to the rear part of a cargo truck, there is a truck equipped with a loading / unloading device at the rear of the truck. In general, a cradle lifting device of a lorry has a cradle rotatably supported at a free end of a lift arm having one end rotatably supported on the cradle. A tilt cylinder device that opens and closes the load receiving table is interposed, and a lift cylinder device that raises and lowers the load receiving table is provided.These tilt cylinder devices and lift cylinder devices use the tilt cylinder device to move the load receiving table. The motor is driven by the hydraulic oil of the hydraulic pump driven by the motor when closing or raising the loading platform by the lift cylinder device, and the motor is driven when opening the loading platform or lowering the loading platform. Instead, it operates by the weight of the receiving platform.

That is, a lift cylinder device and a tilt cylinder device are branched and connected to an oil passage for supplying and discharging pressure oil of a hydraulic pump driven by a motor, and are connected to the oil passage connected to the lift cylinder device. Is provided with a lift valve, and a tilt valve is provided in an oil passage connected to the tilt cylinder device. The lift cylinder device is operated by the opening and closing operation of the lift valve to rotate the lift arm, and the tilt cylinder device is operated by the opening and closing operation of the tilt valve to open and close the load receiving table.

[0004]

However, in the above-described conventional loading / unloading device, since the weight of the load and the weight of the load are added to the load, the impact occurs when the load is started and stopped. There is a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus for lifting and lowering a load receiving cradle which can prevent the occurrence of an impact when the loading cradle is started and stopped.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a lifting / lowering device for a loading tray, wherein the lifting member is supported on the loading platform so as to be able to move up and down, a loading tray supported by the lifting member, and a lift cylinder which lifts and lowers the lifting member. A lift valve for controlling the lift cylinder device in the supply / discharge oil passage for supplying / discharging hydraulic oil of a hydraulic pump to / from the lift cylinder device. In the loading / lifting device in which is provided, a discharge oil passage for guiding the hydraulic oil of the hydraulic pump and the hydraulic oil of the lift cylinder device to a tank is branched from the supply / drain oil passage,
A flow proportional valve is interposed in the discharge oil passage.

According to the above-described means, for example, at the beginning of the lowering operation of the lift cylinder device, the lift cylinder device is slowly started by gradually increasing the discharge flow rate of the pressure oil by the flow proportional valve. Further, at the end of the lowering operation of the lift cylinder device, the flow rate of the pressure oil supplied to the lift cylinder device is gradually reduced by the flow proportional valve, so that the lift cylinder device is gently stopped. As described above, the lowering operation of the lift cylinder device is slowly started at the initial stage, and is slowly stopped at the end stage, thereby preventing the impact at the time of starting and stopping the lowering of the load receiving platform.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

[0009] As shown in FIG. 2, a loading tray lifting device 10 according to the present invention is provided at the rear end of the loading platform 2 of the truck 1. That is, the loading tray elevating device 10 includes a pair of lift arms 11, and both lift arms 11, 1
Numerals 1 are symmetrically arranged below the rear end of the loading platform 2 and one end of each is rotatably supported. A load receiving table 12 is rotatably supported between the free ends of the two lift arms 11 and 11 so as to maintain the horizontal position. Receiving platform 1
2 is made of a material having corrosion resistance and rigidity, such as aluminum or iron, and is formed in a rectangular panel shape having a size corresponding to the loading platform 2. A cart stopper 13 is provided near an end of the upper surface of the loading tray 12 opposite to the loading tray 2.
Are laid along the edges, and the cart stopper 13
Are configured to prevent a cart as a load placed on the receiving tray 12 from falling off.

[0010] A pair of tilt cylinder devices 14 for opening and closing the load receiving table are interposed between the lower surface of the rear end side of the load table 2 and the load side of the load receiving table 12 in a symmetrical manner. The cylinder devices 14 and 14 are configured to reciprocally rotate the load receiving table 12 between the vertical posture and the horizontal posture with respect to the lift arm 11. A pair of lift cylinder devices 15 for raising and lowering the load receiving platform are interposed symmetrically between the lower side of the rear end of the loading platform 2 and the end of the loading platform 12 on the loading platform side. The lift cylinder devices 15 and 15 are configured to raise and lower the load receiving platform 12 between the height position of the loading platform 2 and the ground contact position.

As shown in FIG. 1, each of the tilt cylinder device 14 and the lift cylinder device 15 is constituted by a single-acting hydraulic cylinder device.
Pressure oil is supplied from a hydraulic pump 17 driven by a motor 16. Tilt cylinder device 1
Numeral 4 operates to close the loading tray 12 by supplying the pressure oil, and the lift cylinder device 15 operates to raise the loading tray 12 by the supply of the pressure oil. The tilt cylinder device 14 is configured to open the receiving tray 12 by discharging the supplied pressure oil by its own weight, and the lift cylinder device 15 transfers the supplied pressure oil to the own weight of the receiving tray 12. , The loading tray 12 is lowered. A tank 18 is connected to a suction port of the hydraulic pump 17. The oil passage 19 connected to the discharge port of the hydraulic pump 17
(Hereinafter referred to as a tilt oil passage) 20 and an oil passage (hereinafter referred to as a lift oil passage) 21 to the lift cylinder device 15 at a branch point 20a. .

A control valve (hereinafter, referred to as a tilt valve) 22 for controlling the tilt cylinder device 14 is provided in the tilt oil passage 20, and a lift cylinder device 15 is provided in the lift oil passage 21. Control valve for controlling (hereinafter,
It is called a lift valve. ) 23 are interposed. Each of the tilt valve 22 and the lift valve 23 is a 2-port / 2-port
It consists of a position, a spring offset, and an electromagnetic switching valve. A check valve 24 and a control valve (hereinafter, referred to as a lowering valve) 25 are provided in series in the oil passage 19 between the hydraulic pump 17 and the branch point 20a. The lowering valve 25 is composed of a two-port, two-position, spring offset, electromagnetic switching valve.

A discharge oil passage 27 branches from an intermediate portion between the check valve 24 and the lowering valve 25 in the oil passage 19, and the other end of the discharge oil passage 27 is connected to the tank 18. A discharge valve (hereinafter, referred to as a flow proportional valve) 28 composed of a flow proportional valve is interposed in the discharge oil passage 27, and the flow proportional valve 28 operates to shorten the tilt cylinder device 14 and the lift cylinder device 15. That is, it is configured to control the operation of the loading tray 12 opening by its own weight and the operation of lowering the loading tray 12 by its own weight. Hydraulic pump 17 and check valve 2
The relief oil passage 29 is branched from the middle of the oil passage 19 between the four and connected to the discharge oil passage 27, and a relief valve 30 is interposed in the middle of the relief oil passage 29.

The DC motor 16 is connected to a battery 32 via a relay switch 31a of a motor relay 31. The battery 32 is connected to a power terminal 35a of the controller 35 via the main switch 33. The relay coil 31b of the motor relay 31 is connected to a motor relay terminal 35b. Further, a rotation sensor 34 for detecting the number of rotations is connected to the DC motor 16, and the rotation sensor 34 is connected to a motor rotation detection terminal 35 c of the controller 35.

The solenoid of the flow proportional valve 28 is connected to a current detection terminal 35 of a controller 35 through a current detection resistor 36.
d and is connected to a flow proportional valve terminal 35e. The solenoid of the lowering valve 25 is connected to a lowering valve terminal 35f of the controller 35. The solenoid of the lift valve 23 is connected to a lift valve terminal 35g of the controller 35, and the solenoid of the tilt valve 22 is connected to a tilt valve terminal 35h of the controller 35.

An operation box 37 is connected to an operation signal terminal 35j of the controller 35.
Reference numeral 7 denotes a switch (hereinafter, referred to as an open switch) 38 for instructing the opening operation of the loading tray 12, a switch (hereinafter, a closing switch) 39 for instructing the closing operation of the loading tray 12, and the loading tray 12. (Hereinafter, referred to as a lowering switch) 40 for instructing a lowering operation of the vehicle and a switch (hereinafter, referred to as a lowering switch) for instructing an uppering operation of the loading tray 12.
It is called an up switch. ) 41 are provided respectively.

The input end of the controller 35 is provided with a tilt sensor 42 for detecting the inclination of the receiving tray 12 and the receiving tray 1.
A lift sensor 43 for detecting the lift position of the
Is connected to an inclination angle sensor 44 for detecting the inclination angle. As shown in FIG. 2, the tilt sensor 42 is installed on the mounting portion of the tilt cylinder device 14 of the loading tray 12, and detects the opening angle of the loading tray 12 by measuring the inclination of the loading tray 12. It is configured as follows. The lift sensor 43 is provided on the lift arm 11, and is configured to detect the height position of the load receiving table 12 by detecting the rotation angle of the lift arm 11. The tilt angle sensor 44 measures the tilt angle of the loading platform 2 which is a reference for measuring the tilt of the loading tray 12, and is illustrated as being attached to the loading platform 2 in FIG. 2 is mounted on a base of a controller 35 installed in the controller 2.

The controller 35 is constituted by a microcomputer or the like, and based on programs and tables stored in the memory, commands from the operation box 37, detection outputs of the sensors 34, 42, 43 and 44, etc. Relay 31, flow proportional valve 28, lowering valve 2
5. The operation of the lift valve 23 and the tilt valve 22 is controlled.

Next, the loading / unloading device 1 according to the above configuration
The operation of 0 will be described.

In FIG. 1, when the up switch 41 or the close switch 39 is operated with the main switch 33 turned on, the relay coil 31b is excited by the controller 35 and the relay switch 3 is turned on.
1a is turned on. As a result, D
Electricity flows through the C motor 16 and the pressure oil of the hydraulic pump 17 is supplied to the oil passage 19. At this time, the controller 35
The number of rotations of the motor 16 is recognized based on the detection value from the rotation sensor 34, and the supply flow rate of the hydraulic pump 17 is calculated based on the number of rotations.

When the raising switch 41 is operated,
The solenoid of the lift valve 23 is excited by the controller 35 to switch the lift valve 23, and the oil passage 19
And the pressure oil in the lift oil passage 21 is supplied to the lift cylinder device 1
5 and the receiving platform 12 is raised. At this time, the flow rate supplied to the lift cylinder device 15 by the flow rate proportional valve 28 is released to the tank 18 (bleed off), so that the rising speed can be changed.

When the close switch 39 is operated,
The solenoid of the tilt valve 22 is excited by the controller 35 to switch the tilt valve 22 and the oil passage 19
And the pressure oil in the tilt oil passage 20 is the tilt cylinder device 1
4 and the receiving table 12 is closed. At this time, the closing speed can be changed by releasing (bleed-off) the flow supplied to the tilt cylinder device 14 to the tank 18 by the flow proportional valve 28.

In FIG. 1, when the lowering switch 40 or the opening switch 38 is operated with the main switch 33 turned on, the solenoid of the lowering valve 25 is energized and switched, and the hydraulic oil in the oil passage 19 is switched. Is supplied to the discharge oil passage 27.

When the down switch 40 is operated,
The solenoid of the lift valve 23 is excited by the controller 35 to switch the lift valve 23, and the pressure oil in the lift cylinder device 15 is lowered by the weight of the load receiving table 12 and the weight of the load on the load receiving table 12. The oil is returned to the tank 18 via the valve 25, the discharge oil passage 27, and the flow proportional valve 28. At that time, by controlling the flow proportional valve 28, the flow rate returned to the tank 18 can be controlled, and the lowering speed can be changed.

When the opening switch 38 is operated,
The solenoid of the tilt valve 22 is excited by the controller 35 to switch the tilt valve 22, and the pressure oil in the tilt cylinder device 14 is lowered by the own weight of the loading tray 12 and the weight of the load on the loading tray 12. The oil is returned to the tank 18 via the valve 25, the discharge oil passage 27, and the flow proportional valve 28. At this time, by controlling the flow proportional valve 28, the flow rate returned to the tank 18 can be controlled, and the opening speed can be changed.

Next, the operation of the slow start and slow stop of the loading tray lifting device 10 will be described. First, the lift cylinder device 1
5 shows the action of slow start and slow stop in the lowering operation of FIG.
A description will be given along the flowchart shown in FIG.

When the lower switch 40 is turned on by the operator to lower the lift arm 11, the controller 35 starts the control flow of the lowering operation shown in FIG. In the first step A1, the controller 35
Monitors the stroke of the lift cylinder device 15 at any time based on the detection signal of the lift sensor 43.

In the second step A2, the controller 35 determines whether "the down switch 40 is turned on". When the down switch 40 is turned on (YE
In S), the process proceeds to the third step A3. If the down switch 40 is not turned on (NO), a fourteenth step A1 is performed.
Proceed to 4. Note that when the down switch 40 is not turned on, it means that the operator has stopped turning on the down switch 40.

In the third step A3, the controller 35 energizes the solenoid of the lift valve 23 to open the lift valve 23, and proceeds to a fourth step A4. Fourth step A
In step 4, the controller 35 energizes the solenoid of the lowering valve 25 to open the lowering valve 25, and the fifth step A5
Proceed to.

In the fifth step A5, the controller 35 determines the current relationship between the target flow rate Qc and the stroke as shown in FIG.
The target flow rate Qc that should be present is obtained by comparing the strokes No. 5 and the process proceeds to the sixth step A6. Incidentally, the relational characteristics between the target flow rate Qc and the stroke shown in FIG. It is remembered.

In the sixth step A6, the controller 35 determines whether or not the target flow rate Qc to be present is equal to or less than the current gentle operation flow rate Qs of the flow proportional valve 28, ie, "Qc ≦ Qs".
"Is determined. If the target flow Qc is larger than the gentle operation flow Qs (NO), the process proceeds to the seventh step A7, and if the target flow Qc is less than the gentle operation flow Qs (YES), the process proceeds to the thirteenth step A13. .

Here, the gentle operation flow rate Qs is a flow rate for returning the pressurized oil in the lift cylinder device 15 to the tank 18, and the initial value is "0".

In the seventh step A7, the controller 35 determines whether "the measured time Ts of the slow start slow stop timer has exceeded the slow start unit flow rate change time Tu", that is, "Ts>T".
u ”. If “Ts> Tu” is not satisfied (NO), the seventh step A7 is repeated, and if “Ts> Tu” is satisfied (YES), the flow proceeds to the eighth step A8.

In the eighth step A8, the controller 35 adds "1" as the flow rate per unit time (= Tu) to the gentle operation flow rate Qs, that is, calculates "Qs = Qs + 1", and proceeds to the ninth step A9.

In the ninth step A9, the slow operating flow rate Q
s, ie, pressurized oil in the lift cylinder device 15
Since the flow returning to 8 is controlled by the flow proportional valve 28,
The memory of the proportional valve flow rate Qv of the controller 35 is stored in the memory of the slow operation flow rate Qv so that the proportional valve flow rate Qv becomes the slow operation flow rate Qs.
Replace with s. Next, the controller 35 proceeds to a tenth step A10.

In a tenth step A10, the controller 35 compares the current proportional valve flow rate Qv with the relationship characteristic between the target current Ic of the flow proportional valve 28 and the proportional valve flow rate Qv shown in FIG. 4B. Thus, the target current Ic is obtained, and the process proceeds to the eleventh step A11. By the way, FIG.
The relationship characteristic between the target current Ic of the flow proportional valve 28 and the proportional valve flow Qv shown in (b) is obtained in advance as a table by an empirical method such as an experiment, a past result, and a simulation by a computer. It is stored in the internal memory in advance.

In the eleventh step A11, the controller 35 determines whether "the target current Ic is equal to the detection current If of the current detection terminal 35d", that is, "Ic = If". Two steps A12
If it is equal (YES), the process returns to the first step A1.

In the twelfth step A12, the controller 35 sends the flow proportional valve 2 through the flow proportional valve terminal 35e.
The target current Ic is applied to the solenoid No. 8, and the process returns to the eleventh step A11. Then, the controller 35 sets “Ic =
Until If, the feedback control that repeats the closed loop of the eleventh step A11 and the twelfth step A12 is executed.

In the eleventh step A11, "Ic = I
When the control returns to the first step A1 at the step f), the controller 35 repeats the routine of the first step A1 to the twelfth step A12 until “Qc ≦ Qs” in the sixth step A6.

First step A1 to twelfth step A12
As shown in FIG. 4 (c), the lowering speed of the lift arm 11 gradually increases with the gradient of the set time Tu of the slow start slow stop timer as shown in FIG. It will be. That is, in the state where the lift valve 23 and the lowering valve 25 are opened (third step A3 and fourth step A4), the flow proportional valve 2
When the proportional valve flow rate Qv of No. 8 is gradually increased (fifth step A5 to twelfth step A12), the flow rate of the pressure oil discharged from the lift cylinder device 15 to the tank 18 is gradually increased. Therefore, the lowering operation of the load receiving table 12 by the lift cylinder device 15 is slowly started.

During or after the slow start, the lift cylinder strokes, and Qc shown in FIG.
When c ≦ Qs ”, the process proceeds to the thirteenth step A13 by the sixth step A6. In the thirteenth step A13,
The slow flow Qs is replaced by the target flow Qc, and the process proceeds to the ninth step A9. That is, the controller 35 sets “Q
s ← Qc ”, and the process proceeds to the ninth step A9.

In the ninth step A9, the slow operating flow rate Q
s, ie, pressurized oil in the lift cylinder device 15
Since the flow returning to 8 is controlled by the flow proportional valve 28,
The memory of the proportional valve flow rate Qv of the controller 35 is stored in the memory of the slow operation flow rate Qv so that the proportional valve flow rate Qv becomes the slow operation flow rate Qs.
Replace with s. Next, the controller 35 proceeds to a tenth step A10.

In a tenth step A10, the controller 35 compares the current proportional valve flow rate Qv of the flow proportional valve 28 with the above-mentioned relationship characteristic between the target current Ic of the flow proportional valve 28 and the proportional valve flow rate Qv, thereby obtaining the target current Ic is obtained, and the process proceeds to an eleventh step A11. Eleventh step A1
In 1, the controller 35 determines whether "the target current Ic is equal to the detection current If of the current detection terminal 35d", that is, "Ic = If". If not (NO), the controller 35 proceeds to the twelfth step A12, In this case (YES), the process returns to the first step A1.

In the twelfth step A12, the controller 35 sends the flow proportional valve 2 through the flow proportional valve terminal 35e.
The target current Ic is applied to the solenoid No. 8, and the process returns to the eleventh step A11. Then, the controller 35 sets “Ic =
Until If, the feedback control that repeats the closed loop of the eleventh step A11 and the twelfth step A12 is executed.

In the eleventh step A11, "Ic = I
f ”and returns to the first step A1, the controller 35 determines that the first step A1 to the sixth step A6, the thirteenth step A13, the ninth step A9, the tenth step A1
0, the eleventh step A11, the twelfth step A12 and the routine of the first step A1 are repeated until the switch is turned off in the second step A2.

By controlling the target current Ic by the controller 35 in this routine, the lowering speed of the lift arm 11 becomes the speed of the target flow rate Qc by the cylinder stroke, as shown in FIG. When the lowering valve 25 is opened (third step A3 and fourth step A4), the proportional valve flow rate Qv of the flow proportional valve 28 is controlled to the target flow rate Qc (fifth step A5, sixth step A6, 13th step A13, 9th step A9, 10th step A10, 11th step A
11, twelfth step A12), lift cylinder device 1
FIG. 4A shows the flow rate of the pressure oil discharged from the tank 5 to the tank 18.
Therefore, the lowering operation of the load receiving table 12 by the lift cylinder device 15 is gradually stopped from the speed conversion point before the ground contact point.

When the lower switch 40 is turned off, the lower switch 4 is turned on in the second step A2.
When it is determined that 0 is not on (NO), the controller 35 proceeds to a fourteenth step A14. In a fourteenth step A14, the controller 35 sets the target flow rate Q
c is set to zero, that is, “Qc = 0”, and the process proceeds to the fifteenth step A15.

In the fifteenth step A15, the controller 35 determines whether "the target flow rate Qc is equal to the gentle operation flow rate Qs". That is, the controller 35 sets “Qc
= Qs ”. The controller 35 sets the target flow rate Qc
If is equal to the gentle operation flow rate Qs (YES), the flow proceeds to the sixteenth step A16, and if not (NO), the flow proceeds to the nineteenth step A19.

In the sixteenth step A16, the controller 35 stops energizing the solenoid of the lift valve 23, closes the lift valve 23, and proceeds to a seventeenth step A17. In the seventeenth step A17, the controller 35
The power supply to the solenoid of the lowering valve 25 is stopped to close the lowering valve 25, and the process proceeds to the eighteenth step A18.

In the eighteenth step A18, the controller 35 sends the flow proportional valve 2 through the flow proportional valve terminal 35e.
The energization of the solenoid 8 is stopped, the flow proportional valve 28 is closed, and the control flow for stopping the lowering operation of the lift cylinder device 15 is ended.

In turn, in the fifteenth step A15,
When the controller 35 determines that the target flow rate Qc is not equal to the gentle operation flow rate Qs (NO) and proceeds to the nineteenth step A19, the controller 35 determines in step N19 that the measurement time Ts of the slow start slow stop timer is slow. Stop unit flow rate change time Td
Has been exceeded ”, that is,“ Ts> Td ”is determined. When “Ts> Td” is not satisfied (NO), the controller 35 repeats the nineteenth step A19. When “Ts> Td” is satisfied (YES), the controller 35 proceeds to a twentieth step A20.

In the twentieth step A20, the controller 35 subtracts "1" as the flow rate per unit time from the gentle operation flow rate Qs, that is, calculates "Qs = Qs-1", and proceeds to the ninth step A9.

In the ninth step A9, the proportional valve flow rate Q
v is replaced by the gentle operation flow rate Qs. Then, in a tenth step A10, the controller 35 subtracts the relation characteristic between the target current Ic of the flow rate proportional valve 28 and the proportional valve flow rate Qv shown in FIG. The target current Ic is obtained by collating the proportional valve flow rate Qv in the eleventh step A1.
Proceed to 1.

In the eleventh step A11, the controller 35 determines whether "the target current Ic is equal to the detection current If of the current detection terminal 35d", that is, "Ic = If". Two steps A12
If it is equal (YES), the process returns to the first step A1.

In the twelfth step A12, the controller 35 sends the flow proportional valve 2 through the flow proportional valve terminal 35e.
The target current Ic is applied to the solenoid No. 8, and the process returns to the eleventh step A11. Then, the controller 35 sets “Ic =
Until If, the feedback control that repeats the closed loop of the eleventh step A11 and the twelfth step A12 is executed.

In the eleventh step A11, "Ic = I
f ”and returns to the first step A1, the controller 35 determines that the first step A1, the second step A2, the fourteenth step A14, the nineteenth step A19, the twentieth step A20, the ninth step A9, The routine of the tenth step A10, the eleventh step A11, the twelfth step A12 and the first step A1 is repeated until "Qc = Qs" in the fifteenth step A15.

By controlling the target current Ic in this routine, as shown in FIG. 4C, the lowering speed of the lift arm 11 is reduced by the set period T of the slow start slow stop timer.
It becomes a gentle thing that gradually descends only during s. That is, when the proportional valve flow rate Qv of the flow proportional valve 28 is gradually reduced in a state where the lift valve 23 and the lowering valve 25 are open, the lift cylinder device 15
The flow rate of the pressurized oil discharged to the container is gradually reduced, so that the loading cylinder 12
The lowering operation becomes a gentle speed.

Thereafter, in the twentieth step A20, the gentle operation flow rate Qs becomes zero, and the controller 35 determines that "Qc = Qs" in the fifteenth step A15 (YE).
S), the controller 35 ends the control flow of the lowering operation through the sixteenth step A16, the seventeenth step A17, and the eighteenth step A18.

As described above, the control of the flow proportional valve 28 by the controller 35 causes the lift cylinder device 15
In the lowering operation, the speed is gradually increased or decreased during a predetermined time or range in starting and stopping, so that an impact is prevented from being applied to the loading tray 12 when the loading tray 12 is started and stopped. can do.

As described above, the slow start and slow stop control by the controller 35 is executed even when the lower switch 40 is turned off and on during the lowering operation of the lift cylinder device 15, so that the lower switch is controlled. 40
Is turned off and on in the middle,
It is possible to prevent an impact from being applied to the load receiving tray 12 at the time of stopping during the descent of 2 and at the time of restarting.

Next, the action of the slow start and slow stop in the lifting operation of the lift cylinder device 15 will be described with reference to the flowchart shown in FIG.

The lift arm 1 shown in FIG.
When 1 is raised, the lift valve 23 shown in FIG. 1 is opened, the lowering valve 25 is set to the normal position, and the DC motor 16 is operated. As a result, the lift cylinder device 15 is extended, the lifting arm 11 is raised, and the load receiving table 12 is raised. At this time, the speed of the raising operation is changed by controlling the flow rate supplied to the lift cylinder device 15 by returning the flow rate of the hydraulic pump 17 to the tank 18 by the flow rate proportional valve 28.

When the raising switch 41 is turned on by the operator to raise the lift arm 11, the controller 35 starts the control flow of the raising operation shown in FIG. In the first step B1, the controller 35
Calculates the stroke of the lift cylinder device 15 as needed based on the detection signal of the lift sensor 43 and monitors the stroke.

In the second step B2, the controller 35 determines whether or not the raising switch 41 is turned on. When the raising switch 41 is turned on (YE
In S), the process proceeds to the third step B3. If the raising switch 41 is not turned on (NO), a fifteenth step B1 is performed.
Go to 5. Note that, when the raising switch 41 is not turned on, it means that the operator has stopped turning on the raising switch 41.

In the third step B3, the controller 35 determines whether "the motor relay 31 is turned on". When the motor relay 31 is turned on (YE
In S), the process proceeds to a fourth step B4. If the motor relay 31 is not turned on (NO), a twelfth step B4 is performed.
Proceed to 22.

In the twenty-second step B22 to the twenty-fifth step B25, the flow proportional valve 28 is fully opened in order to initialize the supply flow rate to the lift cylinder device 15 to "0", and "pump flow <proportional valve" This is the step of controlling the flow rate.

In the twenty-second step B22, the controller 35 sets the proportional valve current Ic to the full-open current Im. That is, “Ic ← Im” is set, and the process proceeds to the twenty-third step B23.

In the twenty-third step B23, the controller 35 judges "Ic = If". If not equal (NO), the controller 35 proceeds to the twenty-fourth step B24. Go to Step B25.

In the twenty-fourth step B24, the controller 35 applies the proportional current Ic to the solenoid of the flow proportional valve 28 through the flow proportional valve terminal 35e, and returns to the twenty-third step 23. Then, the controller 35 sets “Ic
= If ”, the feedback control that repeats the closed loop of the twenty-third step B23 and the twenty-fourth step 24 is executed.

The controller 35 executes the twenty-third step B2.
In step 3, "Ic = If", and the twenty-fifth step B
25, the motor relay 31 is turned on through the motor relay terminal 35b in a twenty-fifth step B25,
The process returns to the third step B3 and proceeds to the fourth step B4.

In the fourth step B4, the controller 35 energizes the solenoid of the lift valve 23 to open the lift valve 23, and proceeds to the fifth step B5.

In the fifth step B5, the controller 35 determines the relationship between the target flow rate Qc and the stroke as shown in FIG.
The target flow rate Qc that should be present is obtained by comparing the strokes of No. 5 and the process proceeds to the sixth step B6. In the case of the lifting operation of the lift cylinder device 15, FIG.
The stroke in the table (a) starts from the ground contact side.

In the sixth step B6, the controller 35 determines whether or not the target flow rate Qc to be present is equal to or greater than the current gentle operation flow rate Qs of the flow proportional valve 28, ie, "Qc ≦ Qs".
"Is determined. If the target flow rate Qc is less than the slow operation flow rate Qs (NO), the process proceeds to the seventh step B7. If the target flow rate Qc is equal to or greater than the slow operation flow rate Qs (YES), the process proceeds to the fourteenth step B14.

Here, the gentle operation flow rate Qs is a flow rate supplied to the lift cylinder device 15, and the initial value is "0".

In the seventh step B7, the controller 35 determines whether "the measurement time Ts of the slow start slow stop timer has exceeded the slow start unit flow rate change time Tu", that is, "Ts>T".
u ”. If "Ts>Tu" is not satisfied (NO), the seventh step B7 is repeated, and if "Ts>Tu" (YES), the flow proceeds to the eighth step B8.

In the eighth step B8, the controller 35 adds "1" as the flow rate per unit time to the slow operation flow rate Qs. That is, “Qs = Qs + 1” is calculated, and the process proceeds to the ninth step B9.

In the ninth step B9, the controller 35 calculates the flow rate Qp of the hydraulic pump 17, and proceeds to the tenth step B10. In the tenth step B10, the controller 35 obtains the flow rate Qv of the flow proportional valve 28 by subtracting the gentle operation flow rate Qs from the hydraulic pump flow rate Qp, and proceeds to the eleventh step B11. That is, the controller 35 sets “Qv
= Qp−Qs ”, and the process proceeds to an eleventh step B11.

In the eleventh step B11, the controller 35 compares the current proportional valve flow rate Qv with the relation characteristic between the target current Ic of the flow proportional valve 28 and the proportional valve flow rate Qv shown in FIG. 4B. Thus, the target current Ic is obtained, and the process proceeds to the twelfth step B12.

In the twelfth step B12, the controller 35 determines whether "the target current Ic is equal to the detection current If of the current detection terminal 35d", that is, "Ic = If". Three steps B13
If it is equal (YES), the process returns to the first step B1.

In the thirteenth step B13, the controller 35 sets the flow proportional valve 2 through the flow proportional valve terminal 35e.
The target current Ic is applied to the solenoid No. 8 and the process returns to the twelfth step B12. Then, the controller 35 sets “Ic
= If ", the feedback control is executed to repeat the closed loop of the twelfth step B12 and the thirteenth step B13.

In the twelfth step B12, "Ic = I
When the controller 35 returns to the first step B1 as f), the controller 35 repeats the routine from the first step B1 to the thirteenth step B13 until “Qc ≦ Qs” in the sixth step B6.

First step B1 to thirteenth step B13
By the control on the target current Ic by the routine of (1), the raising speed of the lift arm 11 becomes gentle gradually rising only during the set period Ts of the slow start slow stop timer. That is, in a state where the motor relay 31 is turned on and the lift valve 23 is opened (third step B3 and fourth step B4), as shown in FIG. 4C, the gentle operation flow rate Qs is gradually increased. (Fifth step B5 to thirteenth step B13), the flow rate of the pressurized oil supplied from the hydraulic pump 17 to the lift cylinder device 15 is gradually increased. The lifting operation of the loading table 12 by 15 has a slow speed.

During or after the slow start, the lift cylinder strokes, and Qc shown in FIG.
When c ≦ Qs ”, the process proceeds to the fourteenth step B14 by the sixth step B6. In the fourteenth step B14,
The gentle operation flow rate Qs is replaced with the target flow rate Qc, and the process proceeds to the ninth step B9. That is, “Qs ← Qc” is set, and the process proceeds to the ninth step B9.

In the ninth step B9, the controller 35 calculates the flow rate Qp of the hydraulic pump 17, and proceeds to the tenth step B10. In the tenth step B10, the controller 35 calculates “Qv = Qp−Qs”, and proceeds to the eleventh step B11. In an eleventh step B11,
The controller 35 calculates the target current Ic, and proceeds to the twelfth step B12. In the twelfth step B12, the controller 35 determines "Ic = If", and if not equal (NO), proceeds to the thirteenth step B13, and if equal (YES), returns to the first step B1.

In the thirteenth step B13, the controller 35 sets the flow proportional valve 2 through the flow proportional valve terminal 35e.
The target current Ic is applied to the solenoid No. 8 and the process returns to the twelfth step B12. Then, the controller 35 sets “Ic =
Until If, the feedback control that repeats the closed loop of the twelfth step B12 and the thirteenth step B13 is executed.

In the twelfth step B12, "Ic = I
f ”and returns to the first step B1, the controller 35 determines that the first step B1 to the sixth step B6, the fourteenth step B14, the ninth step B9 to the twelfth step B1
2 and the first step B1
This operation is repeated until the raising switch 41 is turned off in Step 2.

By controlling the target current Ic by the controller 35 in this routine, as shown in FIG. 4A, the lifting speed of the lift arm 11 becomes the speed of the target flow rate Qc by the cylinder stroke, and the motor relay 3
1 is turned on and the lift valve 23 is opened (third step B3 and fourth step B4), the flow proportional valve 28
Is proportional pump flow rate Qp = (pump flow rate Qp−target flow rate Qc)
(Fifth step B5, sixth step B6, fourteenth step B14, ninth step B9 to thirteenth step B13), and the flow rate supplied to the lift cylinder device 15 is controlled by the cylinder stroke shown in FIG. Therefore, the lifting operation of the load receiving table 12 by the lift cylinder device 15 is gently stopped from the speed change point just before the upper limit position.

If the up switch 41 is turned off in the middle, and it is determined in the second step B2 that the up switch 41 is not on (NO),
The controller 35 proceeds to the fifteenth step B15. In the fifteenth step B15, the controller 35 sets the target flow rate Qc to zero, that is, “Qc = 0”, and proceeds to the sixteenth step B16.

In the sixteenth step B16, the controller 35 determines whether "the target flow rate Qc is equal to the gentle operation flow rate Qs". That is, the controller 35 sets “Qc
= Qs ”. The controller 35 sets the target flow rate Qc
If is equal to the gentle operation flow rate Qs (YES), the process proceeds to a seventeenth step B17, and if not (NO), the process proceeds to a twentieth step B20.

In the seventeenth step B17, the controller 35 stops energizing the solenoid of the lift valve 23, closes the lift valve 23, and proceeds to an eighteenth step B18. In an eighteenth step B18, the controller 35
Turns off the motor relay 31 through the motor relay terminal 35b, and proceeds to the nineteenth step B19.

In the nineteenth step B19, the controller 35 controls the flow proportional valve 2 through the flow proportional valve terminal 35e.
The power supply to the solenoid 8 is stopped, the flow proportional valve 28 is closed, and the control flow for stopping the lifting operation of the lift cylinder device 15 is terminated.

On the other hand, in the sixteenth step B16, the controller 35 determines that the target flow rate Qc is not equal to the gentle operation flow rate Qs (NO), and proceeds to the twentieth step B20. "The measurement time Ts of the slow start slow stop timer is the slow stop unit flow change time Td.
Has been exceeded ”, that is,“ Ts> Td ”is determined. The controller 35 repeats the twentieth step B20 when “Ts> Td” is not satisfied (NO), and proceeds to the twenty-first step B21 when “Ts> Td” is satisfied (YES).

In the twenty-first step B21, the controller 35 subtracts "1" as the flow rate per unit time from the gentle operation flow rate Qs, that is, calculates "Qs = Qs-1", and proceeds to the ninth step B9.

In the ninth step B9, the controller 35 calculates the flow rate Qp of the hydraulic pump 17, and proceeds to a tenth step B10. In the tenth step B10, the controller 35 calculates “Qv = Qp−Qs”, and proceeds to the eleventh step B11. At this time, the slow operation flow rate Qs after the subtraction
Is used. In an eleventh step B11, the controller 35 determines the target current Ic, and in a twelfth step B1
Proceed to 2. In the twelfth step B12, the controller 35 determines that “Ic = If”, and if not equal (N
In the case of O), the process proceeds to the thirteenth step B13.
In ES), the process returns to the first step B1.

In the thirteenth step B13, the controller 35 sends the flow proportional valve 2 through the flow proportional valve terminal 35e.
The target current Ic is applied to the solenoid No. 8 and the process returns to the twelfth step B12. Then, the controller 35 sets “Ic =
Until If, the feedback control that repeats the closed loop of the twelfth step B12 and the thirteenth step B13 is executed.

In the twelfth step B12, "Ic = I
f ”and returns to the first step B1, the controller 35 determines that the first step B1, the second step B2, the fifteenth step B15, the sixteenth step B16, the twentieth step B20, the twenty-first step B21. , Ninth step B9,
The routine of the tenth step B10, the eleventh step B11, the twelfth step B12, the thirteenth step B13, and the first step B1 is referred to as “Q
Repeat until c = Qs ”.

By controlling the target current Ic in this routine, as shown in FIG. 4C, the lifting speed of the lift arm 11 is reduced by the set period T of the slow start slow stop timer.
It becomes a gentle thing that gradually descends only during s. That is, when the gentle operation flow rate Qs is gradually reduced in a state where the motor relay 31 is turned on and the lift valve 23 is opened, the flow rate of the pressure oil supplied from the hydraulic pump 17 to the lift cylinder device 15 is gradually reduced. Therefore, the lifting operation of the load receiving table 12 by the lift cylinder device 15 becomes a gentle speed.

Thereafter, in the twenty-first step B21, the gentle operation flow rate Qs becomes zero, and the controller 35 determines that "Qc = Qs" in the sixteenth step B16 (Y
ES) and the controller 35 executes a seventeenth step B17,
After the eighteenth step B18 and the nineteenth step B19, the control flow of the raising operation is ended.

As described above, the control of the flow proportional valve 28 by the controller 35 causes the lift cylinder device 15
Since the speed of the lifting operation is gradually increased or decreased during a predetermined time or range in starting and stopping, it is possible to prevent a shock from being applied to the loading tray 12 when the loading tray 12 is started and stopped. can do.

As described above, the slow start and slow stop control by the controller 35 is executed even when the lift switch 41 is turned off and on in the middle of the lift operation of the lift cylinder device 15. 41
Is turned off and on in the middle,
It is possible to prevent an impact from being applied to the loading tray 12 at the time of stopping and restarting during the ascent of 2.

According to the present embodiment, the receiving table 12
For the expansion and contraction operation of the tilt cylinder device 14 that opens and closes, the control of the slow start and the slow stop can be executed.
However, the control is similar to the control for the lift cylinder device 15 described with reference to the flowcharts shown in FIGS.

As described above, according to the present embodiment, the operation speed can be automatically reduced at the beginning and end of the lifting and lowering operation of the lift arm and the opening and closing operation of the load receiving table, so that the operator is troublesome. Can be prevented and the impact applied to the load receiving table can be prevented, and as a result, the load can be safely lifted and lowered. Further, the life of the components can be extended by reducing the impact applied to each component.

[0103] The present invention is not limited to the above embodiment, but may be modified without departing from the scope of the invention.
It goes without saying that various changes are possible.

For example, the stroke of the lift cylinder device and the stroke of the tilt cylinder device are not limited to being detected by the lift sensor and the tilt sensor, but may be detected by integrating the flow rate. In that case, the lift sensor and the tilt sensor can be omitted.

The lift member is not limited to a lift arm whose one end is rotatably supported on a shaft, but may be an elevator supported at the rear end of the carrier so as to be able to move up and down.

At the time of opening / closing operation of the loading tray, since no load is loaded on the loading tray, the slow start and slow stop control of the tilt cylinder device may be omitted.

[0107]

As described above, according to the present invention,
Since the slow start and the slow stop can be automatically executed when the loading / unloading platform is moved up and down, it is possible to omit troublesome operations by the operator and prevent the occurrence of an impact, so that the loading / unloading of the load can be performed safely. .

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a lifting / lowering device of a pallet truck according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a mounting state of a loading tray elevating device.

FIG. 3 is a flowchart showing a lowering operation of the lift cylinder device.

FIG. 4 is a diagram illustrating the operation thereof.

FIG. 5 is a flowchart showing a lifting operation of the lift cylinder device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lorry car, 2 ... Carrier, 10 ... Lifting device for cargo carrier, 1
DESCRIPTION OF SYMBOLS 1 ... Lift arm (lift member), 12 ... Loading table, 13
... Cart stopper, 14 ... Tilt cylinder device, 15 ...
Lift cylinder device, 16 DC motor, 17 hydraulic pump, 18 tank, 19 oil path, 20 oil path for tilt, 20a branch point, 21 oil path for lift, 22 valve for tilt, 23 ... Lift valve, 24 ... check valve, 25 ... lowering valve, 27 ... discharge oil passage, 28 ... flow proportional valve, 29 ... relief oil passage, 30 ... relief valve, 31 ... motor relay, 3
1a ... relay switch, 31b ... relay coil, 32 ...
Battery 33, Main switch 34 Rotation sensor 35 Controller 35a Power supply terminal 35b
Motor relay terminal, 35c ... Motor rotation detection terminal, 35
d: current detection terminal, 35e: flow proportional valve terminal, 35f:
Lowering valve terminal, 35g Lift valve terminal, 35h Tilt valve terminal, 35j Operation signal terminal, 36 Current detection resistor, 37 Operation box, 38 Open switch, 39
... Close switch, 40 Down switch, 41 Up switch, 42 Tilt sensor, 43 Lift sensor, 44
... Tilt angle sensor.

Claims (1)

[Claims] A lift member supported on the carrier so as to be able to move up and down, a carrier supported by the lift member, a lift cylinder device for moving the lift member up and down, and pressurized oil of a hydraulic pump to the lift cylinder device. An oil supply / discharge passage for supplying / discharging, wherein the supply / discharge oil passage to the lift cylinder device is provided with a lift valve for controlling the lift cylinder device. A drain oil passage for guiding the pressure oil of the hydraulic pump and the pressure oil of the lift cylinder device to the tank is branched from the oil discharge passage, and a flow proportional valve is interposed in the discharge oil passage. Characteristic loading / unloading platform lifting device.