JP4649060B2 - 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 has conventionally been 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. 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 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 by 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 first hydraulic pump that supplies hydraulic oil to the auxiliary actuator via the auxiliary control valve and a second hydraulic pump that supplies hydraulic oil to the lift cylinder via the lift control valve are provided and discharged from the first hydraulic pump. A metering throttle is installed in the oil passage that supplies the operating oil to the auxiliary actuator, and the auxiliary control valve controls the required flow rate of the hydraulic oil discharged from the first hydraulic pump in response to the differential pressure across the metering throttle. And a pressure compensation valve that divides the surplus flow rate with the hydraulic fluid discharged from the second hydraulic pump and supplies it to the lift cylinder via the lift control valve. The tilt cylinder and the attachment serve as the auxiliary actuator. Cylinder, and each oil passage that supplies hydraulic oil to the tilt cylinder and attachment cylinder Grayed squeeze interposed respectively, shall comprising the shuttle valve leading to the pressure compensating valve by selecting the higher of the pressure at the downstream side of the throttle each metering.
[0014]
According to a second aspect, in the first aspect, the hydraulic oil supplied from the first hydraulic pump and the second hydraulic pump to the tank side at a neutral position where the lift control valve stops supplying and discharging the hydraulic oil to and from the lift cylinder. A neutral passage for returning was provided.
[0016]
Operation and effect of the invention
According to the first aspect of the invention, the pressure compensation valve operates to divert the required flow rate of the hydraulic oil discharged from the first hydraulic pump to the auxiliary actuator via the auxiliary control valve and to discharge the surplus flow rate from the second hydraulic pump. The oil is combined with oil and supplied to the lift cylinder via a lift control valve. For this reason, it becomes possible to control the operation of the auxiliary actuator independently of the lift cylinder, and it is possible to avoid the operation of the lift cylinder from affecting the operation of the auxiliary actuator.
Since the shuttle valve selects the higher one of the pressures downstream of each metering throttle and guides it to the pressure compensation valve, the pressure compensation valve is supplied from the first hydraulic pump when the load of the tilt cylinder or the attachment cylinder is high. Supply hydraulic oil to tilt cylinder and attachment cylinder. For this reason, the number of auxiliary actuators can be increased using a shuttle valve.
[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. .
[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 first hydraulic pump and the second hydraulic pump flows through the neutral passage of the lift control valve and is returned to the tank side. , 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, P1 and P2 are first and second hydraulic pumps driven by the engine, T is a tank, 6 is a lift control valve that controls supply and discharge of hydraulic oil to and from the lift cylinder 5, and 4 is hydraulic oil to the tilt cylinder 3. A tilt control valve 8 controls supply / discharge, and an attachment control valve 8 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]
The first hydraulic pump P 1 supplies hydraulic oil to the tilt cylinder 3 via the tilt control valve 4 and supplies hydraulic oil to the attachment cylinder 7 via the attachment control valve 8. The second hydraulic pump P <b> 2 supplies hydraulic oil to the lift cylinder 5 via the lift control valve 6.
[0025]
In the figure, reference numeral 9 denotes a pressure compensation valve. This pressure compensation valve 9 divides a necessary flow rate of the hydraulic oil discharged from the first hydraulic pump P1 into the attachment cylinder 7 and the tilt cylinder 3 and transfers the surplus flow rate to the second. The hydraulic oil discharged from the hydraulic pump P <b> 2 is merged and supplied to the lift cylinder 5 via the lift control valve 6.
[0026]
In the figure, reference numerals 80 and 16 denote relief valves. The relief valve 80 opens when the discharge pressure of the first hydraulic pump P1 rises above a predetermined value, and the relief valve 16 has a predetermined discharge pressure of the first hydraulic pump P2. When the pressure rises above the value, the valve opens and determines the maximum discharge pressure for each.
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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 first hydraulic pump P1 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 and 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.
[0031]
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 first hydraulic pump P1 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. It flows in the order of 33 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 first hydraulic pump P1.
[0032]
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.
[0033]
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.
[0034]
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 oil discharged from the first hydraulic pump P1 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 and 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.
[0035]
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 first hydraulic pump P1 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. It flows in the order of 43 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.
[0036]
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.
[0037]
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 hydraulic oil discharged from the second hydraulic pump P2 and the pressure compensation valve 9 discharged from the first hydraulic pump P1 are passed through. Since the surplus hydraulic oil that has flowed through the supply oil passage 23 through the neutral passage 15 is returned to the tank T, the pressure loss can be kept small.
[0038]
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 the ascending position a, the hydraulic oil sent from the second hydraulic pump P2 or the first hydraulic pump P1 flows in the order of the load check valve 55 → the bottom side oil passage 53 and is supplied to the oil chamber of the lift cylinder 5.
[0039]
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.
[0040]
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.
[0041]
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.
[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 at the position a as shown by the urging force of the spring, and the hydraulic oil discharged from the first hydraulic pump P1 flows in the order of the discharge oil passage 21 → the pressure compensation valve 9 → the supply oil passage 22, and the tilt cylinder 3 , And supplied to the attachment 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 first hydraulic pump P 1 flows in the order of the discharge oil passage 21 → the pressure compensation valve 9 → the check valve 51 → 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, so that the necessary flow rate of the hydraulic oil discharged from the first hydraulic pump P1 is divided into the attachment cylinder 7 and the tilt cylinder 3, and the surplus flow rate is supplied to the lift cylinder 5. The operation of the attachment cylinder 7 or the tilt cylinder 3 can be controlled independently of the lift cylinder 5. 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 lift cylinder 5 is led through a lift control valve 6 by the combined amount of hydraulic fluid discharged from the second hydraulic pump P2 and surplus hydraulic fluid discharged from the first hydraulic pump P1. 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 operation speed of can be suppressed small.
[0046]
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 oil discharged from the first hydraulic pump P1 is changed to the discharge oil passage 21 → the pressure compensation valve 9 → Supply oil passage 23 → neutral passage 15 → tank oil passage 28 is flowed back to the tank T, and the total amount of hydraulic oil discharged from the second hydraulic pump P2 is supplied to the supply oil passage 23 → neutral passage 15 → It flows in the order of the tank oil passage 28 and is returned to the tank T. Thereby, a pressure loss is restrained small and the energy consumption of the 1st hydraulic pump P1 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. When the load is high, the pressure compensation valve 9 supplies the hydraulic oil from the first hydraulic pump P1 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 P1 First hydraulic pump P2 Second hydraulic pump

Claims (2)

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, the first hydraulic supplying hydraulic fluid through the auxiliary control valve to the auxiliary actuator a pump, wherein a second hydraulic pump for supplying hydraulic oil through the lift control valve to the lift cylinders, the metering throttle to the oil path for supplying to the auxiliary actuator operating oil discharged from the first hydraulic pump interposed, the excess flow while diverting the required flow rate of the hydraulic oil discharged in response to differential pressure across the metering throttle from the first hydraulic pump to said auxiliary actuator through the auxiliary control valve the pressure compensating valve to be supplied to the lift cylinder through the lift control valve is combined with the hydraulic oil discharged from the second hydraulic pump For example, the a tilt cylinder and the attachment cylinder as auxiliary actuator, the metering throttle to the oil passage for supplying hydraulic oil to the tilt cylinder and the attachment cylinder interposed respectively, the downstream side of the throttle each metering A hydraulic control device for an industrial vehicle, comprising a shuttle valve that selects a higher one of the pressures and guides it to the pressure compensation valve . The lift control valve includes a neutral passage for returning the hydraulic oil supplied from the first hydraulic pump and the second hydraulic pump to the tank side in a neutral position where supply and discharge of the hydraulic oil to and from the lift cylinder is stopped. The hydraulic control device for an industrial vehicle according to claim 1.

Images