JP5353464B2 - Forklift hydraulic device and hydraulic pump - Google Patents

Description

  The present invention relates to a forklift hydraulic device and a hydraulic pump.

  Conventionally, forklift hydraulic devices disclosed in FIGS. 10 and 11 of Patent Document 1 are known. In this hydraulic apparatus, a hydraulic pump capable of discharging pressure oil to a discharge pipe and capable of changing a discharge capacity by a variable capacity mechanism is driven by an engine. As shown in FIG. 3 of Patent Document 1, the variable capacity mechanism is attached to a control cylinder, a control piston provided so as to be movable back and forth with respect to the control cylinder, and a direction to increase the discharge capacity against the control piston. And a control spring having power. An oil chamber is formed between the control cylinder and the control piston. Further, the control cylinder is formed with a through hole capable of supplying and discharging pressure oil to and from the oil chamber regardless of the position of the control piston. When pressure oil is supplied from the through hole into the oil chamber, the control piston moves forward, the inclination angle of the swash plate of the hydraulic pump is reduced, and the discharge capacity is reduced.

  Further, in this hydraulic apparatus, as shown in FIGS. 10 and 11 of Patent Document 1, a cargo handling control valve is provided in the discharge pipe. The cargo handling control valve diverts the pressure oil discharged from the hydraulic pump into a required flow rate of the power steering circuit and a remaining cargo handling circuit flow rate. The flow rate for the cargo handling circuit is supplied to a lift cylinder and a tilt cylinder which are cargo handling circuits.

  In the discharge pipe line leading to the cargo handling control valve, there is disposed a throttle switching valve that is pilot operated by the pressure of the cargo handling circuit and throttles the flow rate of the pressure oil supplied to the cargo handling control valve. In addition, a downstream pressure pilot line is branched in the discharge line between the throttle switching valve and the cargo handling control valve, and a downstream pressure introduction line is branched in the downstream pressure pilot line. The downstream pressure introduction line communicates with the flow control valve. Further, the downstream pressure introduction pipe communicates with the drain through a throttle. An upstream pressure pilot pipe is branched on the upstream side of the throttle switching valve, and an upstream pressure introduction pipe is branched on the upstream pressure pilot pipe. The upstream pressure introduction line is also communicated with the flow control valve. The flow rate control valve is pilot-operated by a differential pressure before and after the throttle switching valve guided from the downstream pressure pilot line and the upstream pressure pilot line. A control line is disposed between the flow control valve and the through hole of the flow rate variable mechanism.

  In this hydraulic apparatus, during cargo handling, the pressure on the downstream side of the throttle switching valve becomes higher than the set value, and as shown in FIG. 10 of Patent Document 1, the throttle switching valve is pushed to the left and has no throttle. A passage is selected. Since the differential pressure does not occur in the throttle switching valve, the upstream pressure introduction line does not communicate with the control line, the control line communicates with the drain, and the pressure oil in the oil chamber is discharged to the drain through the downstream pressure introduction line. Is done. For this reason, the control piston moves backward, the inclination angle of the swash plate of the hydraulic pump increases, and the discharge capacity increases.

  Further, at the time of unloading, the pressure on the downstream side of the throttle switching valve becomes lower than the set value, and as shown in FIG. 11 of Patent Document 1, the throttle switching valve selects a passage with a throttle by spring force. The capacity control valve controls the supply of pressure oil to the control line so that the differential pressure between the upstream side and the downstream side of the throttle switching valve is constant. For this reason, the control piston moves forward until the differential pressure reaches the set value, the inclination angle of the swash plate is reduced, and the discharge capacity is reduced.

  In this way, this hydraulic device can increase the flow rate as the engine speed increases during cargo handling, and can continue to operate at a constant small flow rate regardless of the engine speed during non-loading operations. is there. And since this hydraulic apparatus can change a flow volume so that it may become a flow volume required for cargo handling work, compared with the case where a driving | operation is always continued with a big flow volume, it is possible to suppress a useless power loss.

Japanese Patent Laid-Open No. 3-186600

  However, in the above conventional hydraulic device, the lift cylinder and the tilt cylinder are not distinguished in the cargo handling circuit. Therefore, the hydraulic pump generally discharges by a lift operation that requires a large discharge capacity and a tilt operation that does not require a large discharge capacity. The capacity cannot be changed. For this reason, in this hydraulic device, the hydraulic pump may increase the discharge capacity while performing a tilt operation that does not require a large discharge capacity, resulting in a large power loss.

  For this reason, as shown in FIGS. 1 and 2 of Patent Document 1, it is conceivable to change the biasing force of the spring of the flow control valve with an electromagnet. For example, when the tilt operation is performed, the urging force of the spring of the flow control valve is reduced. As a result, the pressure oil in the upstream pressure introduction pipe is supplied from the through hole into the oil chamber, the control piston moves forward, the inclination angle of the swash plate is reduced, and the discharge capacity is reduced. For this reason, even when the tilt operation is performed, it is possible to continue the operation at a constant small flow rate regardless of the engine speed, and it is possible to suppress power loss.

  However, in this case, the flow rate during the tilt operation is always a small constant value regardless of the engine speed, and the tilt operation cannot be adjusted by the driver's own intention. If the load of the tilt operation is large, there is a risk of engine stall.

  The present invention has been made in view of the above-described conventional situation, and provides a hydraulic device for a forklift that can suppress power loss and can increase or decrease a flow rate during a tilt operation, and a hydraulic pump suitable for the hydraulic device. Is a problem to be solved.

The hydraulic device for a forklift of the present invention is capable of discharging pressure oil to a discharge pipe, and a hydraulic pump capable of changing a discharge capacity by a variable capacity mechanism;
A cargo handling control valve provided in the discharge pipe and for diverting the pressure oil to a required flow rate of a lift cylinder and a tilt cylinder;
A throttle switching valve that is disposed in the discharge pipe leading to the cargo handling control valve, is pilot operated by the pressure of the tilt cylinder or the lift cylinder, and throttles the flow rate of the pressure oil supplied to the cargo handling control valve;
A pilot operated by a differential pressure before and after the throttle switching valve, and a flow rate control valve for controlling supply and discharge of the pressure oil,
The displacement variable mechanism is provided so as to be able to advance and retreat with respect to the control cylinder and the control cylinder, and is supplied with the pressure oil into an oil chamber formed between the control cylinder and itself, so that the discharge capacity is increased. A control piston to reduce
The control cylinder has a main through hole through which the pressure oil can be supplied to and discharged from the oil chamber regardless of the position of the control piston, and the control piston between the maximum capacity position and the intermediate capacity position. A sub through hole capable of supplying the pressure oil to the oil chamber is formed,
Furthermore, a control line disposed between the main through hole and the flow rate control valve;
A tilt pressure introducing conduit for guiding the pressure oil in the tilt cylinder to the sub-passage hole;
Provided in the control line and pilot-operated by the pressure in the tilt cylinder, supplying the pressure oil into the oil chamber, discharging the pressure oil in the oil chamber, and supplying the pressure oil to the oil chamber A flow path switching valve capable of switching between supply and exhaust stop is provided (claim 1).

  In the hydraulic apparatus of the present invention, when the lift is raised, the pressure on the downstream side of the throttle switching valve becomes higher than the set value. For this reason, the flow rate control valve does not supply pressure oil to the oil chamber, and the pressure oil in the oil chamber is discharged through the control line, the flow path switching valve, and the flow rate control valve. For this reason, the control piston moves backward, and the discharge capacity of the hydraulic pump increases.

  When the tilt operation is not performed during unloading, for example, while the forklift is traveling without unloading, the pressure on the downstream side of the throttle switching valve becomes lower than the set value. For this reason, the flow control valve supplies pressure oil to the oil chamber, the control piston moves forward, and the discharge capacity of the hydraulic pump decreases.

  When the tilt operation is performed, the flow path switching valve is pilot-operated by the pressure in the tilt cylinder, and stops the supply and discharge of the pressure oil to the oil chamber through the main through hole. Further, if the control piston is in front of the intermediate capacity position, the pressure oil in the tilt cylinder is introduced into the tilt pressure introduction pipe and supplied into the oil chamber from the sub through hole. If the control piston exceeds the intermediate capacity position as the piston advances due to the supply of pressure oil into the oil chamber, the pressure oil will not be supplied into the oil chamber from the sub-through hole. For this reason, the control piston does not advance beyond the intermediate capacity position, and the hydraulic pump has an intermediate capacity. For this reason, this hydraulic device can continue to operate at an intermediate flow rate when performing a tilt operation, and power loss can be suppressed. Since the tilt cylinder does not require as much oil as the lift cylinder, there is no problem in operation even at an intermediate flow rate.

  Further, since the hydraulic pump is fixed at an intermediate capacity during the tilting operation, the flow rate can be adjusted depending on the rotational speed of the engine or the like according to the driver's own intention.

  Therefore, according to the hydraulic apparatus of the present invention, power loss can be suppressed, and the flow rate during the tilt operation can be increased or decreased. For this reason, since this hydraulic device can suppress power loss more than before, the fuel consumption of the forklift can be further improved, and it is possible to prevent deterioration due to an increase in the oil temperature or the like. In this hydraulic device, for example, in an engine-driven forklift, the discharge capacity of the hydraulic pump is small and the load is reduced during a tilt operation, so it is possible to avoid engine stall without increasing the engine speed. .

  In addition, this hydraulic device does not need to employ an electromagnet for the flow rate control valve, and therefore it is possible to avoid an increase in cost.

  It is preferable that the tilt pressure pilot pipe branches from a supply pipe connecting the cargo handling control valve and the bottom of the tilt cylinder. In this case, the hydraulic pump can have an intermediate capacity during the forward tilt operation. Since the forward tilting operation is often performed slowly, an intermediate flow rate is suitable.

  The tilt pressure introduction pipe is preferably branched from the tilt pressure pilot pipe. In this case, the piping around the tilt cylinder can be easily handled.

  It is preferable that a check valve is provided in the tilt pressure introduction pipe between the branch point of the tilt pressure pilot pipe and the sub through hole. In this case, it is possible to prevent problems caused by the pressure oil supplied through the flow rate control valve, the control line, and the main through-hole flowing back through the tilt pressure introduction line.

A hydraulic pump according to the present invention includes a drive shaft supported in a sealed space formed by a housing and an end cover, and a cylinder block having a plurality of bores parallel to the axis of the drive shaft and rotating together with the drive shaft. And a swash plate pivotally supported by the housing and changing the tilt angle by a variable capacity mechanism, and a shoe moored to be able to rotate and slide with the swash plate, according to the tilt angle of the swash plate A plurality of pistons reciprocating in each bore,
The variable displacement mechanism, the discharge capacity and the control cylinder, movably provided with respect to the control cylinder, the oil chamber formed between the control cylinder and the self by pressure oil moves forward is supplied A control piston to reduce
The control cylinder has a main through hole through which the pressure oil can be supplied to and discharged from the oil chamber regardless of the position of the control piston, and the control piston between the maximum capacity position and the intermediate capacity position. A sub through hole capable of supplying the pressure oil to the oil chamber is formed,
Flow path switching connected to a pilot line and capable of switching between supply of the pressure oil into the oil chamber, discharge of the pressure oil in the oil chamber, and stop of supply and discharge of the pressure oil to the oil chamber And a valve (claim 5).

  If this hydraulic pump is employed, the effect of the hydraulic device for forklifts of the present invention can be achieved without the need for separately preparing a flow path switching valve.

FIG. 4 is a circuit diagram illustrating the forklift hydraulic device according to the first embodiment when the lift is lifted or tilted after tilting. It is sectional drawing of the hydraulic pump which concerns on the hydraulic device for forklifts of Example 1. FIG. FIG. 5 is a cross-sectional view of the forklift hydraulic device according to the first embodiment, which is related to the variable capacity mechanism and the flow path switching valve, when the lift is lifted, tilted backward, or is unloaded. FIG. 4 is a cross-sectional view of the forklift hydraulic device according to the first embodiment when the tilt is tilted forward, according to the variable capacity mechanism and the flow path switching valve. FIG. 3 is a circuit diagram during non-loading traveling according to the forklift hydraulic device of the first embodiment. FIG. 3 is a circuit diagram when tilting forward in the forklift hydraulic device according to the first embodiment. 3 is a graph illustrating a relationship between the engine speed and the flow rate in the forklift hydraulic device according to the first embodiment. It is a graph which shows the relationship between the rotation speed of an engine, and flow volume regarding the hydraulic device for forklifts of a comparative example. It is sectional drawing of the hydraulic pump which concerns on the hydraulic device for forklifts of Example 2. FIG.

  Embodiments 1 and 2 embodying the present invention will be described below with reference to the drawings.

Example 1
The forklift hydraulic device according to the first embodiment is mounted on an unillustrated engine-driven forklift. In this hydraulic apparatus, as shown in FIG. 1, a variable displacement hydraulic pump 1 is driven by an engine.

  As shown in FIG. 2, the hydraulic pump 1 forms a sealed space 5 by fastening a front housing 2, a center housing 3, and an end cover 4. In the sealed space 5, a drive shaft 9 that is pivotally supported by the front housing 2 by the bearing device 6 and the shaft seal device 7 and is pivotally supported by the end cover 4 by the bearing device 8 is rotatably provided. The front housing 2 and the center housing 3 are housings.

  A spline 9 a is formed on the drive shaft 9, and a cylinder block 10 having a plurality of bores 10 a parallel to the axis O is fitted to the spline 9 a so as to be displaceable along the axis O. Further, the front housing 2 is formed with a guide surface 2a, and a swash plate 11 is provided so as to swing around a direction orthogonal to the axis O by the guide surface 2a.

  A plurality of shoes 12 are moored on the rear surface of the swash plate 11 so as to be able to rotate and slide. A piston 13 is moored to each shoe 12. Each piston 13 is accommodated in the bore 10a of the cylinder block 10 so as to reciprocate.

  Between the cylinder block 10 and the end cover 4, a valve plate 14 having a suction port 14 a and a discharge port 14 b is fixed to the end cover 4. The suction port 14a communicates with each bore 10a in the suction stroke, and the discharge port 14b communicates with each bore 10a in the discharge stroke. The end cover 4 is formed with a suction port 4a and a discharge port 4b communicating with the suction port 14a and the discharge port 14b, respectively. The suction port 4 a communicates with the tank 32 via the suction conduit 31 shown in FIG. 1, and the discharge port 4 b communicates with the discharge conduit 33.

  As shown in FIG. 2, a plurality of compression springs 15 are arranged at equiangular intervals at the front end of the cylinder block 10. A pivot 16 is disposed at the front end of the compression spring 15. The compression spring 15 urges the cylinder block 10 along the axis O toward the end cover 4 and urges the pivot 16 along the axis O in the opposite direction to the cylinder block 10. The pivot 16 is swingably anchored to a shoe retainer 17 that anchors each shoe 12 so as to be slidable in the radial direction.

  In the sealed space 5, a variable capacity mechanism 20 is provided on the top dead center side of the piston 13. The variable capacity mechanism 20 has a control cylinder 21 fixed to the end cover 4 and a control piston 22 provided in the control cylinder 20 so as to be able to advance and retract in the direction of the axis O. An oil chamber 23 is formed between the control cylinder 21 and the control piston 22. The control piston 22 moves forward when pressure oil is supplied into the oil chamber 23. The control piston 22 is in contact with the back surface of the swash plate 11 via a ball 24. On the other hand, the front end of the control spring 25 is fixed to the front housing 2 at a symmetrical position across the swash plate 11. The rear end of the control spring 25 is in contact with the front surface of the swash plate 11 via the contact member 26.

  The control cylinder 21 is formed with a main through hole 21 a that can supply and discharge pressure oil to and from the oil chamber 23 regardless of the position of the control piston 22. The main through hole 21 a communicates with a first through hole 4 c formed in the end cover 4. Further, the control cylinder 21 is formed with a sub through hole 21 b extending to the peripheral surface of the control piston 22. The sub through hole 21 b communicates with a second through hole 4 d formed in the end cover 4. An annular pressure guiding groove 22a is recessed in the peripheral surface of the control piston 22, and the pressure guiding groove 22a communicates with the oil chamber 23 through a through hole 22b. The sub through hole 21b communicates with the pressure guiding groove 22a until the control piston 22 advances from the retracted end to the intermediate capacity position.

  In this hydraulic apparatus, as shown in FIG. 1, a cargo handling control valve 34 including a diversion valve is provided in the discharge pipe 33. Supply pipelines 34a, 34b and 34c are connected to the cargo handling control valve 34. The cargo handling control valve 34 diverts the pressure oil discharged from the hydraulic pump 1 to the required flow rate of the lift cylinder 35 through the supply line 34a, and the pressure oil is supplied to the tilt cylinder 36 through the supply line 34b or the supply line 34c. Divide to the required flow rate. The supply pipeline 34b is connected to the bottom of the tilt cylinder 36, and the supply pipeline 34c is connected to the top of the tilt cylinder 36 through a throttle 36a. The cargo handling control valve 34 also diverts the pressure oil to a required flow rate of a power steering circuit (not shown).

  The cargo handling control valve 34 can derive the pressure of the lift cylinder 35 or the tilt cylinder 36 through a pilot pipe line 37. A throttle switching valve 38 is disposed in the discharge pipe 33 leading to the cargo handling control valve 34. The throttle switching valve 38 has a spool that can take a position that does not cause a differential pressure in the front-rear direction and a position that generates a differential pressure in the front-rear direction. This spool is provided so as to move by the pilot pressure by the pilot pipe line 37 and the urging force of the spring 38a.

  Further, a downstream pressure pilot pipe 39 is branched into the discharge pipe 33 between the throttle switching valve 38 and the cargo handling control valve 34. An upstream pressure pilot pipe 40 is branched on the upstream side of the throttle switching valve 38, and an upstream pressure introduction pipe 41 is branched on the upstream pressure pilot pipe 40. The upstream pressure introduction pipe 41 communicates with the flow control valve 42. The flow rate control valve 42 communicates with the tank 32 via the drain line 43 and also communicates with the control line 44.

  The flow rate control valve 42 does not communicate the upstream pressure introduction line 41 with the control line 44 but communicates the control line 44 with the drain line 43 and the upstream pressure introduction line 41 with the control line 44. It has a spool that can take the position to be made. This spool includes the pilot pressure P2 downstream of the throttle switching valve 38 guided from the downstream pressure pilot line 39 and the urging force of the spring 42a, and the pilot upstream of the throttle switching valve 38 guided from the upstream pressure pilot pipe 40. It is provided so as to move with the pressure P1.

  The control line 44 communicates with the main through hole 21a through the first through hole 4c of the hydraulic pump 1. A flow path switching valve 45 is provided in the control pipeline 44. A tilt pressure pilot pipe 46 is branched from the supply pipe 34 b, and a tilt pressure introduction pipe 47 is branched from the tilt pressure pilot pipe 46. A check valve 48 is provided in the tilt pressure introduction conduit 47, and the tip communicates with the sub through hole 21 b through the second through hole 4 d of the hydraulic pump 1.

  As shown in FIGS. 3 and 4, the flow path switching valve 45 has a valve chamber 51 a formed in the valve cases 50 and 51. A spool 52 is movably accommodated in the valve chamber 51a, and the spool 52 is urged toward the valve case 50 by a spring 45a. The valve case 50 is provided with a through hole 50a communicating with the valve chamber 51a from the outside. A tilt pressure pilot pipe 46 is connected to the through hole 50a. The valve case 51 has through holes 51b and 51c that communicate with the valve chamber 51a. The through hole 51 b communicates with the inside of the valve chamber 51 a on the valve case 50 side, and the through hole 51 b communicates with the second through hole 4 d through a tilt pressure introduction passage 47. The through hole 51c communicates with the inside of the valve chamber 51a at a position farther from the valve case 50 than the through hole 51b, and also communicates with the outside. A control pipe 44 is connected to the through hole 51c. The valve case 51 is also formed with a drain hole 51 d that connects the valve chamber 51 a to the tank 32.

  An annular communication groove 52 a is recessed in the peripheral surface of the spool 52. Depending on the position of the spool 52, the through hole 51c allows the control pipe 44 and the first through hole 4c to communicate with each other through the communication groove 52a, or blocks the control pipe 44 and the first through hole 4c. It is like that. That is, the spool 52 is moved by the pilot pressure Pt generated by the tilt pressure pilot pipe 46 and the urging force of the spring 45a.

  In this hydraulic apparatus, as shown in FIG. 1, when the lift is lifted or tilted after tilting, the pilot pressure P2 on the downstream side of the throttle switching valve 38 becomes higher than the set value. At this time, since the pilot pressure Pt is not high in the flow path switching valve 45, as shown in FIG. 3, the control pipe 44 and the first through hole 4c are communicated with each other through the communication groove 52a. Therefore, as shown in FIG. 1, the flow control valve 42 does not connect the upstream pressure introduction pipe 41 to the control pipe 44 and does not supply pressure oil to the oil chamber 23 (see FIG. 2). On the contrary, the flow rate control valve 42 communicates the control line 44 with the drain line 43, so that the pressure oil in the oil chamber 23 is controlled by the control line 44, the flow path switching valve 45, the flow rate control valve 42 and the drain line 43. And then discharged to the tank 32. For this reason, the control piston 22 shown in FIG. 2 moves backward, the inclination angle of the swash plate 11 increases, and the discharge capacity of the hydraulic pump 1 increases to the maximum capacity. In this state, as shown in FIG. 7, it is possible to raise the engine speed from idling and increase the flow rate. If a sufficient flow rate can be secured when the lift rises, power loss can be suppressed by setting the flow rate as an upper limit if the engine speed exceeds a certain level.

  When the lift operation and the tilt operation are not performed at the time of unloading, for example, while the forklift is traveling without unloading, the pilot pressure P2 on the downstream side of the throttle switching valve 38 becomes lower than the set value. Also in this case, since the pilot pressure Pt is not high in the flow path switching valve 45, as shown in FIG. 3, the control pipe 44 and the first through hole 4c are communicated with each other through the communication groove 52a. The through hole 51b is closed by the spool 52, and the function of the check valve 48 is also exhibited. For this reason, as shown in FIG. 5, the flow rate control valve 42 communicates the upstream pressure introduction pipe 41 with the control pipe 44 and supplies pressure oil to the oil chamber 23 (see FIG. 2). On the contrary, since the flow control valve 42 does not connect the control pipe 44 to the drain pipe 43, the pressure oil in the oil chamber 23 is not discharged. Therefore, the control piston 22 shown in FIG. 2 moves forward, the inclination angle of the swash plate 11 is reduced, and the discharge capacity of the hydraulic pump 1 is reduced. In this state, as shown in FIG. 7, it is possible to continue the operation at a constant small flow rate regardless of the engine speed.

  When the forward tilt operation is performed, the pilot pressure Pt increases. Therefore, as shown in FIG. 4, the flow path switching valve 45 blocks the control pipe 44 and the first through hole 4c, and supplies pressure oil to the oil chamber 23 (see FIG. 2) through the main through hole 21a. Stop excretion. If the control piston 22 is between the maximum capacity position and the intermediate capacity position, the pressure oil in the tilt cylinder 36 is introduced into the tilt pressure introduction pipe 47 and supplied into the oil chamber 23 from the sub through hole 21b. The If the control piston 23 exceeds the intermediate capacity position as the control piston 22 advances due to the supply of pressure oil into the oil chamber 23, the pressure oil will not be supplied into the oil chamber 23 from the sub through hole 21 b. For this reason, the control piston 23 shown in FIG. 2 does not advance beyond the intermediate capacity position, and the hydraulic pump 1 has an intermediate capacity.

  In particular, in this hydraulic apparatus, since the tilt pressure pilot pipe 46 is branched from the supply pipe 34b, the hydraulic pump 1 can have an intermediate capacity during the forward tilt operation. That is, the hydraulic device is in the state shown in FIG. For this reason, this hydraulic device can continue operation at an intermediate flow rate when performing a tilt forward tilt operation, and can suppress power loss. Since the forward tilting operation is often performed slowly, an intermediate flow rate is suitable.

  In the hydraulic device of Patent Document 1, since the forward tilt is handled in the same manner as the lift up or the rear tilt, the relationship shown in FIG. 8 may occur. In the relationship shown in FIG. 8, the hydraulic pump increases the discharge capacity due to the increase in the engine speed while performing a tilt forward tilt operation that does not require a large discharge capacity, which clearly causes a large power loss. .

  In this regard, in the hydraulic apparatus of the first embodiment, the hydraulic pump 1 has an intermediate capacity during the tilt forward tilt operation, so that the flow rate can be adjusted by the rotational speed of the engine or the like by the driver's own intention. . In this state, as shown in FIG. 7, it is possible to increase the flow rate with the increase of the engine speed at the intention of the driver, not the flow rate when the lift is raised or tilted after tilting.

  Therefore, according to this hydraulic apparatus, it is possible to suppress power loss and to increase or decrease the flow rate during the tilt forward tilt operation. Moreover, since this hydraulic device can suppress power loss more than before, it is possible to further improve the fuel consumption of the forklift, to suppress an increase in oil temperature, and to prevent deterioration. In this hydraulic apparatus, the pressure oil in the tilt cylinder 36 is released through the throttle 36a when tilting forward, so that the pressure in the tilt cylinder 36 tends to increase. At this time, the discharge capacity of the hydraulic pump 1 is increased. This makes it possible to avoid engine stall even when idling.

  Further, in this hydraulic apparatus, since the tilt pressure introduction conduit 47 is branched from the tilt pressure pilot conduit 46, the piping around the tilt cylinder 36 can be easily handled.

  Further, in this hydraulic apparatus, since the check valve 48 is provided in the tilt pressure introduction pipe 47, the pressure oil supplied through the flow rate control valve 42, the control pipe 44 and the main through hole 21a becomes the tilt pressure introduction pipe. It is possible to prevent problems caused by flowing back through the path 47.

  In addition, this hydraulic device does not require an electromagnet for the flow rate control valve 42, thus avoiding an increase in cost.

(Example 2)
As shown in FIG. 9, the forklift hydraulic device according to the second embodiment employs a hydraulic pump 100 including a flow path switching valve 45.

  That is, the valve chamber 4i is formed in the end cover 4 of the hydraulic pump 100, and the spool 52 is movably accommodated in the valve chamber 4i. The end cover 4 has through holes 4f and 4h communicating with the valve chamber 4i. The through hole 4f communicates with the valve chamber 4i on the valve case 50 side, and the through hole 4f communicates with the sub through hole 21b through the second through hole 4e. The through hole 4f and the second through hole 4e are shut off from the outside by a plug material 4g. The through hole 4h communicates with the valve chamber 4i at a position farther from the valve case 50 than the through hole 4f, and also communicates with the outside. A control line 44 is connected to the through hole 4h. The end cover 4 is also formed with a drain hole 4j that connects the valve chamber 4i to the sealed space 5. The through hole 4f and the second through hole 4e correspond to the tilt pressure introduction passage 47 of the first embodiment, and the contact surface between the valve case 50 and the spool 52 corresponds to the check valve 48 of the first embodiment. Other configurations are the same as those of the first embodiment, and the same components are denoted by the same reference numerals and detailed description thereof is omitted.

  If this hydraulic pump 100 is employed, it is not necessary to prepare the flow path switching valve 45 separately, and the same effects as those of the first embodiment can be achieved.

  In the above, the present invention has been described with reference to the first and second embodiments. However, the present invention is not limited to the first and second embodiments, and can be appropriately modified and applied without departing from the spirit of the present invention. Needless to say.

  The present invention can be used for a forklift.

DESCRIPTION OF SYMBOLS 33 ... Discharge pipeline 20 ... Capacity variable mechanism 1 ... Hydraulic pump 36 ... Tilt cylinder 34 ... Cargo handling control valve 38 ... Restriction switching valve 45 ... Flow control valve 21 ... Control cylinder 23 ... Oil chamber 22 ... Control piston 25 ... Control spring 21a ... Main passage hole 21b ... Sub passage hole 44 ... Control line 46 ... Tilt pressure pilot line 47 ... Tilt pressure introduction line 45 ... Flow path switching valve 34c ... Supply line 48 ... Check valve 2, 3 ... Housing ( 2 ... Front housing, 3 ... Center housing)
DESCRIPTION OF SYMBOLS 4 ... End cover 5 ... Sealed space 9 ... Drive shaft O ... Shaft center 10a ... Bore 15 ... Compression spring 10 ... Cylinder block 11 ... Swash plate 12 ... Shoe 13 ... Piston 16 ... Pivot 17 ... Shoe retainer

Claims (5)

A hydraulic pump capable of discharging pressure oil to the discharge pipe and changing the discharge capacity by a variable capacity mechanism;
A cargo handling control valve provided in the discharge pipe and for diverting the pressure oil to a required flow rate of a lift cylinder and a tilt cylinder;
A throttle switching valve that is disposed in the discharge pipe leading to the cargo handling control valve, is pilot operated by the pressure of the tilt cylinder or the lift cylinder, and throttles the flow rate of the pressure oil supplied to the cargo handling control valve;
A pilot operated by a differential pressure before and after the throttle switching valve, and a flow rate control valve for controlling supply and discharge of the pressure oil,
The displacement variable mechanism is provided so as to be able to advance and retreat with respect to the control cylinder and the control cylinder, and is supplied with the pressure oil into an oil chamber formed between the control cylinder and itself, so that the discharge capacity is increased. A control piston to reduce
The control cylinder has a main through hole through which the pressure oil can be supplied to and discharged from the oil chamber regardless of the position of the control piston, and the control piston between the maximum capacity position and the intermediate capacity position. A sub through hole capable of supplying the pressure oil to the oil chamber is formed,
Furthermore, a control line disposed between the main through hole and the flow rate control valve;
A tilt pressure introducing conduit for guiding the pressure oil in the tilt cylinder to the sub-passage hole;
Provided in the control line and pilot-operated by the pressure in the tilt cylinder, supplying the pressure oil into the oil chamber, discharging the pressure oil in the oil chamber, and supplying the pressure oil to the oil chamber A hydraulic device for a forklift, comprising: a flow path switching valve capable of switching between supply and discharge stop.   The hydraulic device for a forklift according to claim 1, wherein a tilt pressure pilot pipe branches from a supply pipe connecting the cargo handling control valve and the bottom of the tilt cylinder.   The hydraulic device for a forklift according to claim 2, wherein the tilt pressure introduction pipe branches from the tilt pressure pilot pipe.   The hydraulic device for a forklift according to claim 3, wherein a check valve is provided in the tilt pressure introduction pipe between the branch point of the tilt pressure pilot pipe and the sub through hole. A drive shaft supported in a sealed space formed by the housing and the end cover, a cylinder block having a plurality of bores parallel to the axis of the drive shaft and rotating together with the drive shaft, and swinging on the housing The swash plate is pivotally supported and the tilt angle is changed by a capacity variable mechanism, and a shoe moored so as to be able to rotate and slide with the swash plate, and reciprocatingly moves in each bore according to the tilt angle of the swash plate. A plurality of pistons,
The variable displacement mechanism, the discharge capacity and the control cylinder, movably provided with respect to the control cylinder, the oil chamber formed between the control cylinder and the self by pressure oil moves forward is supplied A control piston to reduce
The control cylinder has a main through hole through which the pressure oil can be supplied to and discharged from the oil chamber regardless of the position of the control piston, and the control piston between the maximum capacity position and the intermediate capacity position. A sub through hole capable of supplying the pressure oil to the oil chamber is formed,
Flow path switching connected to a pilot line and capable of switching between supply of the pressure oil into the oil chamber, discharge of the pressure oil in the oil chamber, and stop of supply and discharge of the pressure oil to the oil chamber A hydraulic pump comprising a valve.

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