JP3399241B2 - Flow switching valve of hydraulic drive system in vehicle lift system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a flow rate switching valve of a hydraulic drive device in a lifting device for cargo handling work provided on a rear surface of a cargo bed of a vehicle such as a truck. 2. Description of the Related Art Generally, a vehicle lift device L of this kind is
As shown in FIG. 5, the platform 3 can be moved up and down in a horizontal posture via two columns 2 and 2 arranged along both sides of the rear surface of the loading platform 1, and is rotated upward at the storage height by loading the platform 3 upward. The platform 3 is configured to be retractable at a closed position along the rear surface, and both the lifting operation and the opening / closing operation of the platform 3 are performed using a hydraulic cylinder as a drive source. In such a lifting device L , it is desirable that the platform 3 be moved up and down in a horizontal posture at a high speed in order to speed up the cargo handling work, and that the opening and closing operations be performed at a lower speed in consideration of its safety. . For this reason, as shown in FIG. 6, the present applicant has interposed a flow rate switching valve 6 between a hydraulic cylinder 4 and a hydraulic source 5 to reduce the operating speed of the hydraulic cylinder 4 when the platform is raised and lowered and when the platform is opened and closed. By switching, a lifting device is provided in which the elevating operation is performed at a high speed while the opening and closing operation is performed at a lower speed (Japanese Patent Application No. 8-85180). [0004] However, there is still a point to be improved in this lift device. That is, the closing operation of the platform 3 is performed by the operation of the hydraulic cylinder 4 switched to the low speed side.
The opening operation of the platform 3 is performed not by the positive operation of the hydraulic cylinder 4 but by the weight of the platform 3. [0005] This is because the hydraulic cylinder 4 normally used as a drive source for this type of lift device L is a single-acting type for the purpose of cost reduction and the like, and a thrust force is applied to a side requiring a larger force. The hydraulic cylinder 4 is used in the direction in which That is, in the case of a type in which the platform 3 is rotated upward against the gravity and closed, the thrust of the hydraulic cylinder 4 is applied to the closing operation of the platform 3 which requires a larger force, while the platform 3 is closed. For the opening operation (downward rotation), the hydraulic cylinder 4 is not operated positively, but is opened using the own weight of the platform 3. Therefore, the hydraulic cylinder 4 as a driving source is configured such that the platform 3 It only operates passively as a result of opening operation due to its own weight. However, the pressure of the hydraulic oil generated by the weight of the platform 3 is lower than the pressure of the hydraulic oil positively generated by the hydraulic source 5 mainly composed of a hydraulic pump. Although the amount of hydraulic oil flowing is large, the amount of hydraulic oil flowing during the opening operation is small. As a result, the opening / closing speed of the platform 3 varies rapidly such that the closing operation is fast and the opening operation is slow. Therefore, there is a problem that usability is not good. The present invention has been made to solve this problem. In a vehicle lift device, the platform is moved up and down at a high speed, and the opening and closing operations are performed at a lower speed, and the opening and closing operations are performed at substantially the same speed. Hydraulic drive
It is an object to provide a flow switching valve . [0008] For this reason, the present invention provides
The flow rate switching valve has the configuration described in the claims. This flow rate
According to the switching valve , the speed at the time of raising and lowering operation of the platform, at the time of closing operation and at the time of opening operation is individually controlled ,
As a result, the closing operation and the opening operation of the platform are performed at the same speed.
The vehicle lifting device
You can improve your selfishness. Here, during the opening operation of the platform, the hydraulic actuator only operates passively by the weight of the platform. On the other hand, the closing operation of the platform is performed by positively operating the hydraulic actuator by the high-pressure hydraulic oil generated by the hydraulic source. For this reason, the pressure of the hydraulic oil generated by the platform's own weight during the opening operation of the platform is lower than that during the closing operation. If the pressure of the hydraulic oil is low, the operating speed of the hydraulic actuator will be low, so that the rotation speed of the platform will be low. In this regard, the flow switching valve according to the first aspect has the following features.
Then , the oil passage between the hydraulic actuator for driving the platform and the oil pressure source is switched and its cross-sectional area (flow area)
By changing the platform open
The flow path area during the operation of closing the platform
Platform opening by making it larger than the product
Platform even with low pressure hydraulic oil during operation
Make sure that approximately the same amount of hydraulic oil flows as when closing
Which allows hydraulic actuators to operate at approximately the same speed.
When activated, the closing and opening operations of the platform can be performed at approximately the same speed. Since the closing operation and the opening operation of the platform are performed at the same speed, the usability of the lift device is improved. Further, according to the flow rate switching valve of the first aspect , the second switching member closes the medium flow rate oil passage by a compression spring during the platform closing operation, and the medium flow rate by the pressure of the hydraulic oil during the platform opening operation. Since the configuration is such that the hydraulic oil flow path is opened and the hydraulic oil flow rate is switched to the medium flow rate side, the switching between the low flow rate and the medium flow rate can be automatically performed by the second switching member having a simple configuration, and the flow rate switching valve is provided. Can be simplified and the cost can be reduced. Here, "same speed" means not only a case where the speed is exactly the same value but also a case where the speed is closer to the closing speed (substantially the same speed) by positively increasing the opening speed of the platform. Including. Further , the flow switching valve is simply called from its name.
Since it has only the function to switch (change) the flow rate
No oil passage is provided when hydraulic oil pressure is constant.
By changing the flow path area by switching, literally work
The function to change the flow rate of hydraulic oil and the pressure of hydraulic oil change
Switch the oil passage and change the passage area when
Function to keep the hydraulic oil flow constant.
Have. Accordingly, in this specification, "flow rate switching
The phrase “valve” changes the flow path area by switching oil passages
It is used as a valve. Next, an embodiment of the present invention will be described with reference to FIGS.
A description will be given based on FIG. Flow switching valve 1 of the present embodiment
0 (in the present embodiment the hydraulic cylinder 4) the hydraulic actuator as a drive source are interposed between the hydraulic pressure source 5. The present embodiment is characterized by the flow rate switching valve 10, and the other points of the vehicle lift device L do not need to be particularly changed as compared with the conventional structure. The hydraulic cylinder 4 is a single-acting type. When the hydraulic cylinder 4 is positively operated toward the rod projecting side by supplying hydraulic oil to the head side, the platform 3 is raised, or the platform 3 is lowered at the storage height. When the supply of the hydraulic oil from the hydraulic pressure source 5 is stopped and the head side of the hydraulic cylinder 4 is opened while being rotated in the closing direction, the platform 3 is lowered by its own weight or turned downward from the closed state. The hydraulic cylinder 4 is passively operated toward the rod retracting side. The details of the flow switching valve 10 of the present embodiment are shown in FIGS. The flow switching valve 10 includes a case 11 and a spool 12. The input port 11a of the case 11 is connected to a hydraulic source 5 via a hose (not shown), and the output port 11b is connected to the head side of the hydraulic cylinder 4 via a hose (not shown). At the center of the case 11, a spool 12 as a first switching member is incorporated so as to be movable in the vertical direction in the figure. The upper surface of the spool 12 and the case 1
1, a compression spring 14
The spool 12 is urged downward in the figure. An electromagnetic coil 13 is built in the upper part of the case 11, and when the electromagnetic coil 13 is excited, the spool 12 moves upward against the compression spring 14, and when demagnetized, the spool 12 moves downward by the compression spring 14. Move. The lower limit of the spool 12 is
The lower surface is regulated by contacting the lower cover 15 attached to the lower surface of the case 11, and the upper limit is regulated by the upper surface contacting the upper cover 16. Electromagnetic coil 13
FIG. 1 shows a state in which the spool 12 is moved down due to demagnetization, and FIG. 2 shows a state in which the spool 12 is moved up when the electromagnetic coil 13 is excited. The excitation of the electromagnetic coil 13 is performed based on an ON operation of a limit switch for detecting that the platform 3 has reached the storage height. As shown in FIG. 1, in a state where the electromagnetic coil 13 is demagnetized and the spool 12 is moved downward, a small-diameter shaft portion 12c formed to have a smaller diameter than other parts is provided substantially at the center of the spool 12 in the longitudinal direction. On the inner peripheral surface of 11, the position is shifted downward with respect to the small-diameter hole portion 11 c having the same diameter as the other portions, so that an annular oil passage 17 is formed between the two portions 11 c and 12 c. Input port 1 via this oil passage 17
1a is directly connected to the output port 11b, so that a large amount of hydraulic oil flows between the ports 11a and 11b. Hereinafter, this switching position is referred to as “large flow side” of the flow switching valve 10. When the platform 3 moves up and down, the electromagnetic coil 13 is demagnetized and the flow rate switching valve 10
Is switched to the large flow rate side, and thereby the hydraulic cylinder 4
The platform 3 is moved up and down at a high speed by supplying a large flow of hydraulic oil to the hydraulic cylinder 4 and opening the head side of the hydraulic cylinder 4 to discharge the large flow of hydraulic oil. On the other hand, as shown in FIG. 2, when the electromagnetic coil 13 is excited and the spool 12 moves up,
When the oil passage 17 is almost closed, the oil passage 17
Is restricted to a very small amount. As a result, the hydraulic oil mainly flows through a small flow rate oil passage described below, whereby the flow rate of the hydraulic oil is reduced as compared with the large flow rate side. Hereinafter, this switching position is referred to as “small flow rate side” of the flow rate switching valve 10. At the time of opening / closing operation of the platform 3, since the storage height detection limit switch is ON, the electromagnetic coil 13 is excited, and the flow rate switching valve 10 is switched to the small flow rate side, whereby the flow of hydraulic oil is reduced. As a result, the operating speed of the hydraulic cylinder 4 is reduced, so that the opening and closing operation of the platform 3 is performed at a lower speed than the above-described elevating operation. The oil passage for small flow will be described. The spool 12 has a first oil passage 12a and a second oil passage 12b.
Are formed. The first oil passage 12a is formed to penetrate between the upper and lower end surfaces along the axis, and the second oil passage 12b is formed to penetrate in the radial direction at a small diameter shaft portion 12c formed substantially at the center in the longitudinal direction. The two oil passages 12a and 12b intersect and communicate with each other. When the electromagnetic coil 13 is excited and the spool 12 moves upward as shown in FIG. 2, an oil passage 18 is opened between the lower surface of the spool 12 and the lower cover 15, and the oil passage 18 and the first The input port 11a and the output port 11b are connected to each other via a small flow rate oil passage including the second oil passages 12a and 12b. When the flow switching valve 10 is switched to the small flow side, the oil passage 17 is extremely narrowed as described above, so that the hydraulic oil mainly flows through the small flow passage, and as a result, the flow is reduced. Next, when the flow rate switching valve 10 is switched to the small flow rate side, the flow rate of the hydraulic oil is further switched to the middle flow rate side. That is, as shown in FIGS. 3 and 4, on the outer peripheral side of the lower portion of the spool 12, an annular switching ring 20 as a second switching member is disposed so as to be movable in the vertical direction in the figure. The switching ring 20 is urged upward in the figure by a compression spring 21 interposed between the switching ring 20 and the lower cover 15. On the other hand, on the inner peripheral surface of the case 11, below the small-diameter hole portion 11c, a flange portion 11d is formed in a protruding shape with a constant width toward the inner peripheral side.
A switching ring 20 is pressed by a compression spring 21 on the lower surface of the. As shown in FIG. 3, when the switching ring 20 is pressed against the lower surface of the flange portion 11d, an annular oil passage 23 formed between the spool 12 and the switching ring 20 and the spool 12 and the flange portion are formed. 11d through the same annular oil passage 27 formed between the oil passage 1 and the oil passage 1d.
8 and the output port 11b are communicated. Both oil passages 23, 27
Constitutes a part of the oil passage for small flow. On the other hand, as shown in FIG.
Is pushed down against the compression spring 21 and separated from the flange portion 11d, the oil passage 18 and the output port 11b
Is in addition to the oil passage for small flow passing through the oil passages 27 and 23,
Oil passage 24 between flange 11d and switching ring 20
In addition, the fluid is communicated by a path passing through an oil passage 25 between the switching ring 20 and the inner peripheral hole of the case 11. This oilway 2
The path passing through 4, 25 corresponds to the medium flow passage described in the claims. For this reason, when the switching ring 20 is pressed against the lower surface of the flange portion 11d, the hydraulic oil flows only through the oil passages 23 and 27 (oil passages for small flow), so that the flow amount is the smallest. The flow rate of the working oil at this time is regulated by the oil passage 23 having a smaller width. The width (about 20 μm) of the oil passage 23 is the width (about 40 μm) of the oil passage 27
It is set to about half. When the switching ring 20 is separated from the flange portion 11d, the oil passages 24, 25 in addition to the small flow oil passage are provided.
Since the hydraulic oil flows through the medium flow oil passage consisting of: However, the flow rate at this time is set to be smaller than that at the time of switching to the large flow rate side.
7, 25 and the amount of movement of the switching ring 20 (oil passage 2
4) and the biasing force of the compression spring 21 is appropriately set. When the supply of the hydraulic oil from the hydraulic pressure source 5 is stopped, the switching ring 20 moves downward in the figure against the compression spring 21 by the pressure of the hydraulic oil on the output port 11b side. That is, when the supply of the hydraulic oil from the hydraulic source 5 is stopped and the hydraulic cylinder 4 is actuated toward the rod retracting side by the weight of the platform 3 at the stage of the opening operation of the platform 3 as described later, The switching ring 20 moves against the compression spring 21 due to the pressure of the working oil. According to the vehicle lift device L having the flow rate switching valve 10 configured as described above, the platform 3
At the stage of moving up and down in the horizontal state, the limit switch for detecting the storage height is not turned on, so the electromagnetic coil 13 of the flow rate switching valve 10 is demagnetized.
As shown in (1), the spool 12 is moved downward, and the flow rate switching valve 10 is switched to the large flow rate side. In the state in which the oil flow has been switched to the large flow rate side, the oil passage 1
7 is open, when hydraulic oil is supplied from the hydraulic pressure source 5 to raise the platform 3, the hydraulic oil flows from the input port 11 a through the oil passage 17 to the output port 1.
1b. Accordingly, in this case, a large flow rate of hydraulic oil is supplied to the head side of the hydraulic cylinder 4. Similarly, when the supply of the hydraulic oil is stopped and the head side of the hydraulic cylinder 4 is opened in a state where the flow switching valve 10 is switched to the large flow side, the hydraulic oil on the head side is also output through the oil passage 17. From the port 11b, it flows to the input port 11a. Therefore, also in this case, a large flow of hydraulic oil is returned from the hydraulic cylinder 4 to the oil tank of the hydraulic source 5. As described above, when the flow switching valve 10 is switched to the large flow side, a large flow of hydraulic oil flows through the flow switching valve 10, whereby the platform 3 is moved up and down at a high speed, and the cargo handling work is performed. Speed up. On the other hand, when the platform 3 reaches the storage height, the limit switch is turned on, so that the electromagnetic coil 13 of the flow switching valve 10 is excited. Electromagnetic coil 1
When the coil 3 is excited, the spool 12 moves upward as shown in FIG. 2, so that the oil passage 17 is almost closed, while the oil passage 18 is opened, and the flow switching valve 10 is switched to the small flow side. . When hydraulic oil is supplied from the hydraulic source 5 to close the platform 3 with the flow switching valve 10 switched to the small flow side, the hydraulic oil is mainly supplied to the small flow oil passage (input port 11a → second port). Oil passage 12b → first oil passage 12
a → oil passage 18 → oil passage 23 → oil passage 27) and flows into the output port 11b. In this case, since the switching ring 20 is pressed against the lower surface of the flange portion 11d by the pressure of the compression spring 21 and the flowing hydraulic oil as shown in FIG. Flows into the output port 11b in the most narrowed state via the oil passage 23, and is then supplied to the head side of the hydraulic cylinder 4 so that the platform 3 rotates in the closing direction at a lower speed than the lifting / lowering operation. On the other hand, when the head side of the hydraulic cylinder 4 is opened in a state where the supply of the hydraulic oil from the hydraulic power source 5 is stopped in order to open the platform 3, the switching ring 20
Due to the pressure of the hydraulic oil on the 1b side, the hydraulic oil moves downward in the figure against the compression spring 21, whereby the middle flow oil passage (oil passage 27 → oil passage 24 → oil passage 25 → oil passage 18) is opened. The flow switching valve 10 is switched to the middle flow. For this reason, the hydraulic oil on the head side of the hydraulic cylinder 4 flows from the output port 11b into the oil passage 18 via both the small flow oil passage and the medium flow oil passage, and thereafter, the first oil passage. The oil is returned to the oil tank of the hydraulic power source 5 through a path of 12a → second oil path 12b → input port 11a. in this way,
When the platform 3 is opened, the oil passage 27 → the oil passage 23
In addition to the path, the path from the oil path 24 to the oil path 25 is added, so that the pressure of the hydraulic oil generated by its own weight during the opening operation of the platform 3 is supplied by the hydraulic power source 5 during the closing operation of the platform 3. Even if the pressure is lower than the pressure of the operating oil, almost the same amount of operating oil can flow, and as a result, the platform 3 can be opened and closed at almost the same speed. As described above, according to the lift device L of the present embodiment, when the platform 3 is moved up and down, the flow switching valve 10 is switched to the large flow side, so that the lifting and lowering operation is performed at a high speed and the cargo handling work is performed. On the other hand, at the time of opening / closing operation of the platform 3, the flow switching valve 10 is switched to the small flow side at the time of opening / closing operation of the platform 3, so that the opening / closing operation is performed at a lower speed than the raising / lowering operation, thereby ensuring safety. In addition, during the opening operation of the platform 3, the flow switching valve 10 is automatically switched to the medium flow side, so that the opening operation is performed at a higher speed than in the prior art.
As a result, the platform 3 can be opened at substantially the same speed as the closing operation, so that the usability of the vehicle lift device L can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing an embodiment of the present invention, and is a longitudinal sectional view of a flow rate switching valve in a state where it is switched to a large flow rate side. FIG. 2 is a longitudinal sectional view of a flow switching valve in a state where the flow switching valve is switched to a small flow side. FIG. 3 is a detailed view of a portion A in FIG. 2; FIG. 4 is a detailed view of a portion A of the flow rate switching valve in a state where the flow rate is switched to a middle flow rate side. FIG. 5 is a side view of a vehicle provided with a lift device on a rear surface of a loading platform. FIG. 6 is a diagram showing a configuration of a hydraulic drive device. [Description of Signs] L: Lift device for vehicle 3 ... Platform 4 ... Hydraulic cylinder (hydraulic actuator) 5 ... Hydraulic source 10 ... Flow rate switching valve (3 position type) 11a ... Input port, 11b ... Output port, 11c ... Small diameter hole 11d Flange 12 Spool (first switching member) 12a First oil passage (for small and medium flow), 12b Second oil passage (for small and medium flow) 13 Electromagnetic coil 17 Oil passage (large) 18 ... oil passage (for small / medium flow) 20 ... switching ring (second switching member) 23 ... oil passage (for small / medium flow) 24 ... oil passage (for medium flow) 25 ... oil passage (for medium flow) 27) Oil passage (for small and medium flow)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16K 11/07 B60P 1/44 F16K 17/30 B66F 9/22 B66F 17/00

Claims (1)

(57) [Claim 1] A platform capable of moving up and down in a horizontal posture and capable of opening and closing vertically at a storage height , and the platform
A hydraulic drive device for driving the home,
Drive device has a flow rate control valve between the hydraulic actuator and the hydraulic pressure source, the flow rate switching valve, during platform lifting operations before switching the first switching member to the large flow rate side
Serial platform was moved up and down at high speed, at the time of the platform opening and closing operations more is opened and closed at a low speed of the platform is switched to the first switching member to the small flow rate side and front
In a state in which serial first switching member is switched to the small flow rate side, the platform opening during the closing operation the Purattoho <br/> over beam by switching the <br/> second switching member of said flow control valve to the medium flow rate side The flow rate switching valve of the hydraulic drive device in the vehicle lift device that can be opened at the same speed as the operation
A is, the second switching member, the platform closed during operation to close the medium flow rate oil passage by a compression spring, the platform opening operation to open the oil passage for the in flow rate by the pressure of the working oil, medium hydraulic oil flow Oil in a vehicle lift device characterized by being configured to switch to a flow side
Flow switching valve of pressure drive device .