JP4637402B2 - Hydraulic control device for industrial vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a hydraulic control device for an industrial vehicle.
[0002]
[Prior art]
Conventionally, for example, as shown in FIG. 2, the forklift 101 includes a mast 113 that is tilted by a tilt cylinder 103 at a front portion of a vehicle body, and a fork 114 that moves up and down by the lift cylinder 105 along the mast 113. Insert the bag into the bottom of the luggage to lift or carry the luggage.
[0003]
A work attachment (not shown) such as a clamp device is attached to the forklift 101 corresponding to the cargo handling work, and this work attachment is also driven by a hydraulic actuator.
[0004]
This type of forklift 101 is conventionally provided with , for example, hydraulic control devices (1) and (2) .
[0005]
(1) In FIG. 3, 204 is a tilt control valve that controls supply / discharge of hydraulic oil to / from the tilt cylinder 103, and 206 is a lift control valve that controls supply / discharge of hydraulic oil to / from the lift cylinder 105. Reference numerals 207 and 208 denote attachment control valves for controlling supply / discharge of hydraulic oil to / from each attachment cylinder. 211 and 212 are shuttle valves, respectively, and the shuttle valve 211 selects the higher one of the downstream pressure of the metering throttle 210 provided in the lift tilt control valve 206 and the downstream pressure of the metering throttle 209 provided in the tilt control valve 204. To do. Reference numeral 213 denotes a pressure compensation valve. This pressure compensation valve 213 responds to the differential pressure between the pressure introduced through the shuttle valves 211 and 212 and the upstream pressure of the metering throttles 210 and 209 to adjust the required flow rate to the lift cylinder 105. The flow is divided into the tilt cylinder 103 , and the surplus flow is supplied to the attachment cylinder.
[0006]
(2) In FIG. 4, reference numeral 104 denotes a tilt control valve that controls supply / discharge of hydraulic oil to / from the tilt cylinder 103, and reference numeral 106 denotes a lift control valve that controls supply / discharge of hydraulic oil to / from the lift cylinder 105. Reference numerals 107 and 108 denote attachment control valves for controlling supply / discharge of hydraulic oil to / from each attachment cylinder.
[0007]
All the control valves 104, 106, 107, 108 have neutral passages at their neutral positions, and hydraulic oil discharged from the hydraulic pump P flows to the tank T through the neutral passages, and the tilt cylinder 103, lift Pressure oil is supplied to the cylinder 105 and each attachment cylinder through parallel paths.
[0008]
[Problems to be solved by the invention]
However, such a conventional forklift has the following problems because the required flow rates of the tilt cylinder 103 and the attachment cylinder are smaller than the required flow rate of the lift cylinder 105.
[0009]
In the hydraulic control device of (1) , since the entire flow rate of the hydraulic fluid discharged from the hydraulic pump P is supplied to the tilt section and the attachment section when the lift is not operated, the tilt actuator or the attachment actuator The pressure increases and moves too fast.
[0010]
In the hydraulic control device (2) , when all the control valves 104, 106, 107, 108 are switched to the neutral position, the tilt control valve 104 and the attachment control valves 107, 108 are also discharged from the hydraulic pump P. Since the entire amount of hydraulic fluid flows, the flow passage cross-sectional area of the neutral passage must be ensured to be equal to that of the lift control valve 106 in the tilt control valve 104 and the attachment control valves 107 and 108 having a small required flow rate at the operating position. However, the control valve and the like become larger than necessary.
[0011]
The present invention has been made in view of the above-described problems, and an object thereof is to provide a hydraulic control device for an industrial vehicle that can operate a tilt cylinder and an attachment cylinder without being affected by the operation of a lift cylinder. .
[0012]
[Means for Solving the Problems]
The first invention includes a lift cylinder that operates by supplying and discharging hydraulic oil, a lift control valve that switches supply and discharge of hydraulic oil to and from the lift cylinder, an auxiliary actuator that operates by supplying and discharging hydraulic oil, and hydraulic oil for the auxiliary actuator And an auxiliary control valve that switches between supply and discharge of the hydraulic fluid, and is applied to a hydraulic control device for an industrial vehicle in which the flow rate of hydraulic oil supplied to the auxiliary actuator is smaller than the flow rate of hydraulic oil supplied to the lift cylinder.
[0013]
A metering throttle is provided in the oil passage for supplying the hydraulic oil to the auxiliary actuator, and the auxiliary control valve is used to adjust the required flow rate of the hydraulic oil supplied from the hydraulic source in response to the differential pressure across the metering throttle. And a pressure compensation valve that diverts the surplus flow to the lift cylinder via the lift control valve, and includes a tilt cylinder and an attachment cylinder as auxiliary actuators, and hydraulic oil is supplied to the tilt cylinder and attachment cylinder. A metering throttle is provided in each of the oil passages to be supplied, and a shuttle valve is provided which selects a higher one of the pressures on the downstream side of each metering throttle and leads the pressure compensation valve .
[0014]
According to a second aspect, in the first aspect, the lift control valve includes a neutral passage that returns the hydraulic oil supplied from the hydraulic pressure source to the tank side at a neutral position where the supply and discharge of the hydraulic oil to and from the lift cylinder is stopped. Was characterized.
[0016]
Operation and effect of the invention
According to the first invention, the pressure compensation valve divides the necessary flow rate of the hydraulic oil supplied from the hydraulic source to the auxiliary actuator and supplies the surplus flow rate to the lift cylinder. Therefore, it is possible to avoid the operation of the lift cylinder from affecting the operation of the auxiliary actuator.
[0017]
Although the pressure guided to the lift cylinder fluctuates due to fluctuations in the flow rate supplied to the auxiliary actuator, the capacity of the auxiliary actuator is smaller than the capacity of the lift cylinder, so that the effect on the operating speed of the lift cylinder can be kept small. . Since the shuttle valve selects the higher one of the pressures downstream of each metering restrictor and guides it to the pressure compensation valve, the pressure compensation valve is operated from the hydraulic source when the load of the tilt cylinder or attachment cylinder is high. Are supplied to the tilt cylinder and the attachment cylinder. For this reason, the number of auxiliary actuators can be increased using a shuttle valve.
[0018]
According to the second invention, when the auxiliary actuator and the lift cylinder are not operated, the entire amount of hydraulic oil supplied from the hydraulic source flows through the neutral passage of the lift control valve and is returned to the tank side, so that the pressure loss can be kept small. . At this time, since the hydraulic oil flows around the auxiliary control valve, it is not necessary to form a neutral passage in the auxiliary control valve, so that the auxiliary control valve can be prevented from being enlarged and the cost of the product can be avoided.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0021]
FIG. 1 shows a hydraulic control device provided on a work machine of a forklift as an industrial vehicle. In the figure, 3 indicates two tilt cylinders for tilting the mast of the work machine, and 5 indicates raising and lowering the fork 14 along the mast. Two lift cylinders 7 to be operated are attachment cylinders for driving a work attachment such as a clamp device.
[0022]
The attachment cylinder 7 and the tilt cylinder 3 constitute an auxiliary actuator, and the flow rate of hydraulic fluid supplied to them is smaller than the flow rate of hydraulic fluid supplied to the lift cylinder 5.
[0023]
In the figure, P is a hydraulic pump driven by the engine, T is a tank, 6 is a lift control valve for controlling supply / discharge of hydraulic oil to / from the lift cylinder 5, and 4 is a tilt control for controlling supply / discharge of hydraulic oil to / from the tilt cylinder 3. A valve 8 is an attachment control valve that controls supply / discharge of hydraulic oil to / from the attachment cylinder 7. The tilt control valve 4 and the attachment control valve 8 constitute an auxiliary control valve.
[0024]
In the figure, reference numeral 9 denotes a pressure compensation valve. The pressure compensation valve 9 divides a necessary flow rate of the hydraulic oil discharged from the hydraulic pump P into the attachment cylinder 7 and the tilt cylinder 3 and sends the surplus flow rate to the lift cylinder 5. Supply.
[0025]
In the figure, reference numeral 80 denotes a relief valve. This relief valve 80 opens when the discharge pressure of the hydraulic pump P rises above a predetermined value, and determines the maximum discharge pressure.
[0026]
The tilt control valve 4, the attachment control valve 8, the pressure compensation valve 9, the relief valve 80 and the like are housed in the control valve 1. The lift control valve 6 is housed in the control valve 2.
[0027]
The spool of the tilt control valve 4 is slidably inserted in the spool hole of the control valve 1 and is switched to the neutral position c, the backward tilt position a, and the forward tilt position b according to the sliding position.
[0028]
The spool of the tilt control valve 4 is held at the neutral position c as shown by the biasing force of the centering spring. In this neutral position c, the supply oil passage 22, the rod-side oil passage 32, and the bottom-side oil passage 33 are closed, and the pilot oil passage 34 is communicated with the tank oil passage 29. Thereby, the expansion / contraction operation of the tilt cylinder 3 is stopped.
[0029]
When the spool of the tilt control valve 4 slides in the left direction in the drawing, it is switched to the backward tilt position a, the supply oil passage 22 and the rod side oil passage 32 communicate with each other via the metering restrictor 10, and the bottom side oil passage 33. And the tank oil passage 29 communicate with each other, and the tilt cylinder 3 is contracted. The hydraulic oil discharged from the hydraulic pump P when the tilt cylinder 3 is contracted is discharged oil passage 21 → pressure compensation valve 9 → supply oil passage 22 → metering throttle 10 → load check valve 35 → rod side oil passage 32 in this order. It flows and is supplied to the rod side oil chamber 38. On the other hand, the hydraulic oil in the bottom side oil chamber 39 flows in the order of the bottom side oil passage 33 → the tank oil passage 29 and is returned to the tank T.
[0030]
When the spool of the tilt control valve 4 slides in the right direction in the drawing, it is switched to the forward tilt position b, the supply oil passage 22 and the bottom oil passage 33 communicate with each other via the metering restrictor 10 ', and the rod side oil The passage 32 and the tank oil passage 29 communicate with each other via the counter balance valve 37, and the tilt cylinder 3 is extended. The hydraulic oil discharged from the hydraulic pump P when the tilt cylinder 3 is extended is discharged oil passage 21 → pressure compensation valve 9 → supply oil passage 22 → metering throttle 10 ′ → load check valve 35 → bottom side oil passage 33. It flows in order and is supplied to the bottom side oil chamber 39. On the other hand, the hydraulic oil in the rod side oil chamber 38 flows in the order of the rod side oil passage 32 → the counter balance valve 37 → the tank oil passage 29 and is returned to the tank T. The counter balance valve 37 adjusts the amount of hydraulic oil returned from the rod side oil chamber 38 to the tank T according to the discharge pressure of the hydraulic pump P.
[0031]
The spool of the attachment control valve 8 is slidably inserted in the spool hole of the control valve 1 and is switched to the neutral position c, the operating position a, and the release position b according to the sliding position.
[0032]
The spool of the attachment control valve 8 is held at the neutral position c as shown by the biasing force of the centering spring. In this neutral position c, the supply oil passage 22, the rod side oil passage 42, and the bottom side oil passage 43 are respectively closed, and the pilot oil passage 44 is communicated with the tank oil passage 29. Thereby, the expansion-contraction operation | movement of the attachment cylinder 7 is stopped.
[0033]
When the spool of the attachment control valve 8 slides in the left direction in the figure, it is switched to the operating position a, the supply oil passage 22 and the rod side oil passage 42 communicate with each other via the metering restrictor 10, and the bottom side oil passage 43 and The tank oil passage 29 is communicated, and the attachment cylinder 7 is contracted. The hydraulic fluid discharged from the hydraulic pump P when the attachment cylinder 7 is contracted is discharged oil passage 21 → pressure compensation valve 9 → supply oil passage 22 → metering throttle 11 → load check valve 45 → rod side oil passage 42 in this order. It flows and is supplied to the rod side oil chamber 48. On the other hand, the hydraulic oil in the bottom side oil chamber 49 flows in the order of the bottom side oil passage 43 → the tank oil passage 29 and is returned to the tank T.
[0034]
When the spool of the attachment control valve 8 slides in the right direction in the figure, it is switched to the release position b, the supply oil passage 22 and the bottom oil passage 43 communicate with each other via the metering restrictor 10 ', and the rod side oil passage. 42 and the tank oil passage 29 communicate with each other, and the attachment cylinder 7 is extended. The hydraulic oil discharged from the hydraulic pump P when the attachment cylinder 7 is extended is discharged oil passage 21 → pressure compensation valve 9 → supply oil passage 22 → metering throttle 11 ′ → load check valve 45 → bottom side oil passage 43. It flows in order and is supplied to the bottom side oil chamber 49. On the other hand, the hydraulic oil in the rod side oil chamber 48 flows in the order of the rod side oil passage 42 → the tank oil passage 29 and is returned to the tank T.
[0035]
The spool of the lift control valve 6 is slidably inserted in the spool hole of the control valve 2, and is switched to the neutral position c, the raised position a, and the lowered position b according to the sliding position.
[0036]
The spool of the lift control valve 6 is held at the neutral position c as shown in the figure by the urging force of the centering spring, the bottom side oil passage 53 is closed, and the expansion / contraction operation of the lift cylinder 5 is stopped. In this neutral position c, the supply oil passage 23 is communicated with the tank oil passage 28 via the neutral passage 15, and the surplus hydraulic oil that has been diverted to the supply oil passage 23 via the pressure compensation valve 9 passes through the neutral passage 15 to the tank. Since the pressure is returned to T, the pressure loss can be kept small.
[0037]
When the spool of the lift control valve 6 slides in the left direction in the figure, it is switched to the raised position a, the supply oil passage 23 and the bottom oil passage 53 communicate with each other, and the single-acting lift cylinder 5 is extended. In this ascending position a, the surplus hydraulic oil that has flowed to the supply oil passage 23 via the pressure compensation valve 9 flows in the order of the load check valve 55 → the bottom oil passage 53 and is supplied to the oil chamber of the lift cylinder 5.
[0038]
When the spool of the lift control valve 6 slides in the right direction in the drawing, the position is switched to the lowered position b, the bottom side oil passage 33 and the tank oil passage 28 communicate with each other, and the lift cylinder 5 contracts. In this lowered position b, the supply oil passage 23 is communicated with the tank oil passage 28 via the neutral passage 15, and the surplus hydraulic oil that has been diverted to the supply oil passage 23 via the pressure compensation valve 9 passes through the neutral passage 15 to the tank. Since the pressure is returned to T, the pressure loss can be kept small.
[0039]
The pressure compensation valve 9 has a position a that connects the discharge passage 21 to the supply oil passage 22 and a position b that connects the discharge passage 21 to the supply oil passage 23. The pressure compensation valve 9 is supplied with the upstream pressure of the metering restrictors 10, 10 ′, 11, 11 ′ from the supply oil passage 22 via the pilot oil passage 19, and at the same time the metering restrictor 10 via the pilot oil passage 18. The downstream pressure of 10 ', 11, 11' is introduced.
[0040]
A pilot oil passage 34 and a pilot oil passage 44 are selectively communicated with the pilot oil passage 18 via the shuttle valve 17. Shuttle valve 17 communicates pilot oil passage 34 and pilot oil passage 44 with the higher pressure to pilot oil passage 18.
[0041]
The pilot oil passage 18 communicates with the tank oil passage 29 via the relief valve 16. The relief valve 16 opens when the pressure in the pilot oil passage 18 rises above a predetermined value. Thereby, it is suppressed that the pressure of the pilot oil path 34 and the pilot oil path 44 rises too much, and the tilt cylinder 3, the attachment cylinder 7, etc. are protected.
[0042]
Since the shuttle valve 17 selects a high pressure and guides it to the pressure compensation valve 9, when the differential pressure across the metering throttles 10, 10 'or the differential pressure across the metering throttles 11, 11' is smaller than a predetermined value, the pressure compensation valve 9 is held in the position a as shown by the biasing force of the spring, and the hydraulic oil discharged from the hydraulic pump P flows in the order of the discharge oil passage 21 → the pressure compensation valve 9 → the supply oil passage 22 in the order of the tilt cylinder 3 and the attachment. It is supplied to the cylinder 7.
[0043]
When both the differential pressure across the metering throttles 10, 10 'and the differential pressure across the metering throttles 11, 11' rise above a predetermined value, the pressure compensation valve 9 is switched to position b against the ring spring. The hydraulic oil discharged from the hydraulic pump P flows in the order of the discharge oil passage 21 → the pressure compensation valve 9 → the supply oil passage 23 and is supplied to the lift control valve 6.
[0044]
The pressure compensation valve 9 is configured as described above. The pressure compensation valve 9 divides the necessary flow rate of the hydraulic oil discharged from the hydraulic pump P into the attachment cylinder 7 and the tilt cylinder 3 and supplies the surplus flow rate to the lift cylinder 5. 5, the operation of the attachment cylinder 7 or the tilt cylinder 3 can be controlled independently. That is, the pressure guided to the attachment cylinder 7 or the tilt cylinder 3 does not fluctuate due to fluctuations in the flow rate supplied to the lift cylinder 5, and the operation of the lift cylinder 5 affects the operation speed of the attachment cylinder 7 or the tilt cylinder 3. Can be avoided.
[0045]
The pressure guided to the lift cylinder 5 varies depending on the flow rate supplied to the attachment cylinder 7 or the tilt cylinder 3, but the capacity of the attachment cylinder 7 and tilt cylinder 3 is smaller than the capacity of the lift cylinder 5. The influence given to the operating speed of the cylinder 5 can be suppressed small.
[0046]
Further, when the tilt control valve 4, the attachment control valve 8, and the lift control valve 6 are all switched to the neutral position c, the total amount of hydraulic fluid discharged from the hydraulic pump P is discharged oil passage 21 → pressure compensation valve 9 → supply. The oil passage 23 → the neutral passage 15 → the tank oil passage 28 are flowed in this order and returned to the tank T, so that the pressure loss is kept small and the energy consumption of the hydraulic pump P is reduced. At this time, since the hydraulic oil flows around the tilt control valve 4 and the attachment control valve 8, there is no need to form a neutral passage in the tilt control valve 4 and the attachment control valve 8, and the tilt control valve 4 and the attachment control valve 8 Can be avoided.
[0047]
Since the lift control valve 6 is larger than the tilt control valve 4 and the attachment control valve 8 corresponding to the large capacity of the lift cylinder 5, the lift control valve 6 is formed by forming the neutral passage 15. The increase in size can be suppressed and the cost of the product can be avoided.
[0048]
The shuttle valve 17 selects the higher one of the downstream pressure of the metering throttles 10 and 10 ′ and the downstream pressure of the metering throttles 11 and 11 ′ and guides it to the pressure compensation valve 9, so that the tilt cylinder 3 or the attachment cylinder 7 When the load is high, the pressure compensation valve 9 supplies hydraulic oil from the hydraulic pump P to the tilt cylinder 3 and the attachment cylinder 7. For this reason, the number of auxiliary actuators can be increased using a shuttle valve, and a plurality of sets of attachment cylinders and attachment control valves can be provided.
[0049]
The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention.
FIG. 2 is a side view of a forklift showing a conventional example.
FIG. 3 is a hydraulic circuit diagram showing a conventional example.
FIG. 4 is a hydraulic circuit diagram showing a conventional example.
[Explanation of symbols]
3 Tilt cylinder 4 Tilt control valve 5 Lift cylinder 6 Lift control valve 7 Attachment cylinder 8 Attachment control valve 9 Pressure compensation valve 10 Metering throttle 11 Metering throttle 15 Neutral passage 17 Shuttle valve P Hydraulic pump

Claims (2)

A lift cylinder that operates by supplying and discharging hydraulic fluid, a lift control valve that switches between supply and discharge of hydraulic fluid to and from this lift cylinder, an auxiliary actuator that operates by supplying and discharging hydraulic fluid, and supply and discharge of hydraulic fluid to and from this auxiliary actuator and an auxiliary control valve for switching, in the hydraulic control device for a small industrial vehicles than the flow rate of the hydraulic fluid flow rate of the hydraulic fluid supplied to the auxiliary actuator is supplied to the lift cylinder, supplying hydraulic fluid to the auxiliary actuator to the oil passage a metering throttle interposed, to shunt the required flow rate of the hydraulic oil supplied from the hydraulic pressure source in response to differential pressure across the metering throttle to the auxiliary actuator through the auxiliary control valve with a pressure compensating valve for diverting the excess flow to the lifting cylinder via the lift control valve, A tilt cylinder and an attachment cylinder are provided as auxiliary actuators, and the metering throttle is provided in each oil passage for supplying hydraulic oil to the tilt cylinder and the attachment cylinder, respectively. A hydraulic control apparatus for an industrial vehicle, comprising a shuttle valve that selects a higher one and guides it to the pressure compensation valve . 2. The neutral passage which returns the hydraulic fluid supplied from a hydraulic source to the tank side in the neutral position where the lift control valve stops the supply and discharge of the hydraulic fluid to the lift cylinder. Hydraulic control device for industrial vehicles.

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