JPS5865302A - Oil pressure control apparatus - Google Patents

Abstract

PURPOSE:To minimize a loss of energy by controlling a discharge rate of a variable displacement pump to the minimum necessary flow rate during idling or running respectively in no relation to the number of revolution of an engine. CONSTITUTION:A variable displacement pump 2 is driven by the rotation of an engine 1. During idling, a pressure control valve 17 is operated, a piston 9b is moved, in the left direction, to the position where it is balanced with a restriction spring 9a, and a cam plate 2a is rotated clockwise to reduce the inclined angle of the pump, thereby controlling the discahrge rate of the pump to the minimum necessary flow rate. Further, during running, a changeover valve 15 is controlled to operate a power steering cylinder 14. Also, at this time, the piston 9b is positioned where it has already moved to the left direction, thereby controlling the discharge rate of the pump to the minimum constant flow rate in no relation to the number of revolution of said engine 1. Further, during operation, said piston 9b is moved, to the right end to maximize the inclined angle of said pump, thereby controlling the discharge rate of said pump to the maximum flow rate corresponding to the number of revolution of said engine 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic control device in a hydraulic circuit of a forklift, a loader, etc., and specifically relates to a variable displacement pump driven by an engine, and a first f. a 70-depider that divides the flow into the duct and the second duct and has a restriction on the first duct side, a first actuator connected to the first duct via a first switching valve, and a second duct. The present invention relates to a hydraulic control device in a hydraulic circuit having a second actuator connected to the @20 switching valve.

FIG. 1 is a circuit diagram showing an example of a conventional hydraulic control device of this type, which is applied to a forklift. In FIG. 1, 21 is a fixed displacement pump driven by the engine 1, and 4 is a first conduit through which oil discharged from the engine 21 flows through a throttle 93, which in this example is connected to a power steering cylinder (first actuator). ) A round power steering switching valve (first switching valve) that operates 14 communicates with the tank 11 via a neutral boat 15. 5 is diaphragm #)
The second branched via pressure control 9P17 on the upstream side of 3
The working switching valve 7 is connected to the neutral boats of the working switching valves (second switching valves) 7a and 7b by a conduit, and when the working switching valves 7a and 7b are neutral, the neutral boats communicate with the tank 11. 's7b is switched from the neutral position to the operating position and the tilt cylinder 6a and lift cylinder 6b are activated.
616as16b is a rounded type that supplies a part of the discharged oil of the bonder 2 to the second actuator to operate each cylinder 6't6', respectively. Monthly cut W
The surge pressure generated when switching between Isho 7* and 7b is transferred to tank 1.
This is a relief box to let you escape to 1.

In such a conventional device, when the engine l is rotated, one fixed displacement pump 21 is driven.

When the switching valves 15, 7 & 7b are not operated and they are all in the idle link state, the pump 2.0
The discharged oil flows into the tank 11 through the first conduit 40 constriction D3, and the pressure control valve 17 is operated by the differential pressure generated in the constriction D3, and a part of the pump discharged oil flows through the jIz conduit 5 and the switching valve ya#yb.
It flows into Tank 1 through the neutral boat. When the forklift is running, the switching valve 15 is operated to operate the power steering cylinder 14. When the engine is running, the oil discharged from the pump 2s is supplied to the power steering cylinder 14 through the throttle arm 3, and the pressure at both ends of the throttle arm '30 increases, but the differential pressure therebetween remains constant. Also, during work, the switching valves 7a and yb
to operate the 1/E2F) actuators such as the tilt cylinder 6a and lift cylinder 6b. At this time ζ
The flow rate required for the operation of each cylinder 5m and 5b is the second pipe 5.
It is supplied through.

However, due to the lack of conventional equipment like this, it is necessary to use G when working! Since the flow rate is the highest, and the discharge rate of the fixed displacement pump 210 is determined according to this, the flow rate during one idle link will be higher than necessary, and of course the energy loss due to the excess flow rate will be large. The flow rate during operation is about % of the flow rate during operation, and the pressure is less than half, and even when the pump is running, about ~ ~ of the pump discharge I is a surplus flow rate, and the energy loss due to this is large. Furthermore, in the case of a forklift, about half of the total working time is spent traveling, so it is extremely difficult to minimize energy loss during traveling.

Therefore, in the present invention, the pump driven by the engine is a variable displacement type 1 pump, and the discharge amount of this variable displacement pump is adjusted independently of the engine speed during idling and running. It is an object of the present invention to provide a hydraulic control device that can control the flow rate to the minimum required flow rate, and control the pump discharge amount to the maximum flow rate depending on the engine rotation speed during work by supplying pump discharge oil.

A first embodiment of the present invention, which achieves the above objects, will be described below as shown in FIG.

In this first embodiment, a variable displacement pump 2 is reversely driven by an engine 1, and the oil discharged from the variable displacement pump 2 is divided into a first path 4 and a second f path 5, and 1
Flow-f with diaphragm 3 in w path 411 and e
A power steering cylinder 14 connected to the x pipe 4 via a power steering switching valve 15, and a tilt cylinder 6a and a tilt cylinder 6b connected to the second pipe 5 via work switching valves 7a and 71. In the hydraulic circuit, a g4 pipe line 8 is provided which communicates with the first port 7a in the neutral position when the work switching valve 7't7b is neutral, and a g4 pipe line 8 is provided at one end of the cam plate 2Ik of the variable displacement pump 2. ,
A piston rod 911 of a piston ygb regulated by a regulating spring 9a is always connected to the discharge rate increasing side, and the fourth piston rod 91 is connected to the discharge rate decreasing side port 90 of a constant discharge rate control device that controls the discharge rate of the pump 2. The pipe line 8 is connected, and the discharge rate increasing side port 911 of the constant discharge rate control device 9 is connected to the downstream side of the throttle 3 through a third pipe line 10, and the work switching valve 71t7bK and each cylinder 5a are connected to each other. , 5b is activated, and the rounded 6 passage connecting the fourth pipe line 8 to the tank 11? 7J is a working switching valve 7m.

7m) K is provided and configured.

In addition, 9. is a constant discharge amount control device 90 hydraulic cylinder, 9g
is the rod side cylinder chamber (one chamber on the side where the discharge amount increases), 9
f is a relief valve having the same function as 16CFi16 and 16b, which is the head side cylinder chamber (the other chamber on the side where the discharge amount decreases).

Since the first embodiment has the above-described configuration, the piston 9b is initially moved to the right by the regulating spring 9 to the right end in FIG. 2, and the pump inclination angle is at its maximum. When the engine 1 rotates, the variable displacement pump 2 is driven.

When the switching valves 15e7a*7b are not operated and all of them are in a neutral state at idle, the oil discharged from the pump 2 flows into the tank 11 through the restrictor 3, and the pressure control valve 17 is activated by the differential pressure generated across the restrictor 3. do. As a result, a part of the pump discharge oil is transferred to the first port 7 of the Igz pipe line 51 switching squares 7a and 7b.
At the same time, the oil in the rod side cylinder chamber 9g is transferred from the discharge rate decreasing side port 9C through the fourth pipe line 8 to the head side cylinder '1iQfKlt' to the tank through the third pipe line 10. 11, the piston 9b moves to the left to a position where it is in equilibrium with the regulating spring 91, and the cam plate 2a is rotated clockwise to reduce the pump inclination angle and control the pump discharge amount to the required minimum flow rate.

When the vehicle is running, the switching valve 15 is operated to operate the power steering cylinder 14. At this time, the oil discharged from the pump 2 is supplied to the power steering cylinder 14 through the throttle gear 3, and the pressure at both ends of the throttle gear 3 increases, but the differential pressure remains constant. 4 pipe line 5.8 and the discharge amount decreasing side port) 90 to the head side cylinder W19f and %
The piston 9b is connected to the rod side cylinder chamber 9g via the II3 pipe line 10 and the discharge amount increasing side port 911.
Due to this differential pressure, the cam plate 2a is moved to the left to a position that is in equilibrium with the spring direction of the regulating spring 9a in the same manner as above, and the rotational position is of the cam plate 2a and the pump inclination are maintained in a corresponding state.
The pump discharge amount is controlled to a constant required minimum flow rate regardless of engine speed.

During work, switch fP 7' e 7 bk from the neutral position to the working position to supply part of the oil discharged from pump 2 to the tilt cylinder 6a + lift cylinder 6b, and return oil from the cylinder to tank 1. Activate the tilt cylinder 61 + lift cylinder 6b. In this case, the operation of the lift cylinder 6b is to raise the elevator of the forklift. At this time, the 1st head side cylinder block 9f is the discharge volume reduction side port) 9c, fourth pipe line 8 and passage 7a.

It communicates with the tank 11 through 7m or 7b. As a result, due to the spring force of the ZESTON gbH regulation spring 9a and the pressure of the third pipe line 10, it moves to the right end,
The cam plate 2a is rotated counterclockwise to set the pump inclination angle to the maximum inclination angle, and the pump discharge amount is controlled at the maximum flow rate K11lJ according to the rotational speed of the engine l.

When the switching valve 7b is operated so that the forklift elevator descends, the lift cylinder 6b operates by receiving the supply of pump discharge oil (according to the load of the elevator), so in this case, , 'As in the case of idle linking or running, the head side cylinder m9f is not communicated with the tank 11, and the pump discharge amount is controlled to the minimum necessary flow rate.

As described above, according to the first embodiment, the discharge amount of the variable displacement pump can be controlled to the minimum necessary amount regardless of the engine rotation speed during idling and driving, so that the energy consumption is reduced. Loss can be minimized, and when working by supplying pump discharge oil, the pump discharge amount can be controlled to the maximum flow rate according to the engine speed, so work can be carried out efficiently. play.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.
This is a case where a horsepower limiting device is attached to the device of the embodiment so as not to interfere with the constant discharge amount control device.In other words, in this second embodiment, one end of the cam plate 2 at 6 is attached to the device of FIG. The pilot boat 12 of the horsepower limiting device 12 is connected to the other end of the cam plate 2a and controls the human power of the variable displacement pump 2. It is installed in parallel with the piston rod 911 of the constant discharge amount control device 9 and is in contact with one end of the cam plate 2a by a spring 121. Only, horsepower limiter 120
Horsepower lll1 @ operating rod 12 of the cam plate 2& that resists the spring force of the control spring 120 and provides an operating force to one end of the cam plate 2&
b pilot port) 1211 and the upstream side of throttle) 3 (
It is connected to the discharge outlet of the variable displacement pump 2 by the fifth pipe line 13, and is constructed of a 7-t type. , pilot pressure) 9. Pilot pressure to 121L. an outer piston that is slid in the direction of increasing inclination angle via p<Ilot screw) y12g;
12h is a control spring 12cK inside this outer piston 12f.
an inner piston that is slid in the direction of decreasing inclination against the
12h1 is the rod, and 121 is a round spring that always keeps the actuating rod 12b in contact with one end of the cam plate 2a.Since the second embodiment has the above-mentioned configuration, initially,
The piston 9b is moved to the right by the regulating spring 9a until it reaches the right end in Fig. 3, and the pilot port k12 &
Since no pilot pressure is applied to the pistons 12h and 12f, the inner and outer pistons 12h and 12f are moved to the right by the spring force of the contact spring 121 to the right end in FIG. When the engine 1 rotates, the variable displacement pump 2 is driven. During fitting when the switching valves 1st7atTb are not operated and both of these are in a neutral state, the oil discharged from the pump 2 flows through the throttle 3 to the tank 11,
3, differential pressure occurs. 9 pressure generated upstream 11 of the throttle 3 passes through the fifth pipe 13 and the pilot boats 1za, 12a as pilot pressure to the pilot piston 12g.
and the operating rod 12m) K addition, biro [area difference between the Reston 12g and the operating rod 12b] The inner and outer pistons 13h and 12f move to the left to the left end. Cam plate 2
& by rotating one end of the cam plate 2a to the piston rod 9.
Ths4C is brought into contact with each other. The pressure control valve 17 is actuated by the differential pressure generated across the diaphragm 3. As a result, a part of the pump discharge oil is transferred to the second f passage 5 and the Ml port of the switching valves 7a and 7b) 7
m, and the fourth pipe 8t-to the discharge amount decreasing side port) 90] At the same time as the head side cylinder '119fK flows into the rod side cylinder! 19g of oil is on the side where the discharge amount increases) 911
Ygst road 10 tM tank 1] Kji! At the ninth stage, the piston 9b moves to the left until it is in equilibrium with the regulating spring 9a, and the cam plate 2a is moved in the hour hand direction K (i1) to reduce the pump inclination angle and control the pump discharge amount to the required minimum flow rate.

Even when driving, the pilot pressure applied to the actuating rod 12b resists the control spring 120K and activates the drive limiting device 12! - Instead, the dK pump discharge amount is controlled to a constant required minimum flow rate regardless of the engine speed.

During work, if the load is not large enough to exceed the output of engine 1, the pump discharge amount should be adjusted to the engine 10 as described above.
Controls the maximum flow rate according to the rotation speed. When the load is large and the pump discharge pressure rises to the point that it almost exceeds the output of the engine 1, the pilot pressure built up from the upstream side of the restrictor 3 through the fifth pipe line 13 increases. Pilot port 12a
The pilot pressure introduced from the pilot piston 1
2g to operate the outer piston 12f to the left end and maintain a good condition, push the pilot port 12 (the pilot pressure introduced from l is the operating rod 12t) to the left,
Rotate the cam plate 2& clockwise to remove the inner piston 12h.
is moved to the right against the control spring 120. The cam plate 2a is rotated clockwise to a position where the pilot pressure acting on the operating rod 12m) and the spring force of the control spring 120 are balanced;
Decrease the pump inclination angle and reduce the pump displacement to the flow rate corresponding to the maximum engine output. That is, horsepower control is performed. In this case, the head side cylinder chamber 9f is the tank II.
Since the piston 9b is in a state of being moved to the right end due to the spring force of the regulating spring 91 and the pressure of the third pipe line, the constant discharge amount control device 9 and the horsepower limiting device 120 are controlled. will not interfere.

As mentioned above, in the second embodiment, not only does it have the same effect as the first embodiment, but also the horsepower limiting device is installed together without interfering with the constant discharge amount control device.
As soon as the load increases and is about to exceed the engine output, the horsepower limiting device is activated and the pump discharge amount can be reduced to a flow rate corresponding to the maximum engine output, without causing the engine to stop.

It goes without saying that the present invention is applicable not only to forklifts but also to loaders and the like.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional device, FIG. 2 is a circuit diagram showing a first embodiment of the device of the present invention, and FIG. 3 is a circuit diagram showing a second embodiment of the device of the present invention. 1・・・・・・・・・Engine, 2・・・・・・・・・
Variable displacement pump 12 & cam plate 3
・・・・・・・・・Aperture, 4・・・・・・・・・lXl
Conduit, 5... Second W line, 5a...
...Tilt cylinder (second actuator), 6
b...Lift cylinder (second actuator), 7a, 7b...Work switching valve (second switching box), 711. 7'1e7J・・・・・・Aisle, 7a,・・・・
...First port, 8...4th path, 9... Constant discharge amount control device, 9&...
...Regulation spring, 9b...Piston, 9b weight...Piston rod, 9C.
...Boat on the side where the discharge amount decreases, 91...
...Discharge rate increasing side boat, 9e...
Hydraulic cylinder, 9g...Rod side cylinder chamber (one chamber on the side where the discharge amount increases), 9f...
・Head cylinder chamber (the other chamber on the side where the discharge amount decreases),
10...Third conduit, 11...
...Tank, 12... Horsepower limiting device, 1
21L, 12d...d...Pilot port, 1
2b......Operating rod, 12C...
...Control spring,]2e...Case,
12f... Group... Outer piston, 12g...
...Pimit piston, 12h...Town...Inner piston, 12h,...Inner piston rod, 13...5th pipe line, 14...-
...Power steering cylinder (first 7 units), 15......Power steering monthly switching box (first switching box), 5...Flow divider . Procedural amendment (spontaneous) 11th February 11, 111 Haruki Shimada, Commissioner of the Japan Patent Office, 1. Indication of the case Showa era Patent Application No. 161710 2. Invention 1st title hydraulic control device 3. Case of the person making the amendment Relationship with 41tli JlI person 421 Japan Steel Works Co., Ltd. Specifications and drawings. 6. Contents of the amendment (1) The scope of the 4I claims will be amended in a separate document. (2) Lines 7 to 15 of the specification include “This constant discharge amount...
・・・Seshime,'' is deleted. (3) ``Oil'' in the 4th line from the bottom of page 8 is corrected to ``Air JK,'' in the 3rd line from the bottom of page 8, ``returns to tank 11 through the third pipe lOt'' to ``is released into the atmosphere.'' . (4) In line 9 of the same 9th line, add ``3rd path 10 and'' and insert ``opened to the atmosphere'' after ``through'' in line 9ji of the same 9ji. (5) 10 of the same line PA is removed from the 8th line of ``and the pressure of the third pipe 10'', and the 3rd line from the bottom of the same page 10 is the next K after ``Control.''
``In addition, in the first example of JIIl, as shown in the third diagram, 4!
2shi30 downstream side and discharge amount increase side port) 9 (it-If connected with the third pipe lO, even better control is possible.) (6) In the same 15 true 9 line, add "No, ”, then add “In addition, in the second embodiment, the third conduit 10 does not have to be connected as in the first embodiment.” Correct it as follows.Special!F!Fill's request: (1) A variable displacement pump that is driven by an engine, and the discharge oil of this variable displacement pump is connected to the first pipe and the second pipe. A flow divider that divides the flow into the #Il pipe and has a restriction on the #Il pipe side, a gl actuator connected to the Jl!1 pipe via the first switching valve, and a second switching valve connected to the second pipe. In a hydraulic circuit having a second actuator connected through the hydraulic cylinder q of the constant discharge amount control device connected to one end of the cam plate of the variable displacement pump, the other chamber on the discharge output reduction side and the second The switching valve is connected to the electric 4-ponite of the switching valve, and the second switching valve is configured so that the first boat and the second pipe are connected when it is in neutral, and the first boat and the tank are connected when it is switched. (2) A variable displacement pump driven by F/JIN, and the discharge 1111 of this variable displacement pump is divided into IIl pipe line and jIz pipe line. 's1f A 70-divider having a throttle 9 on the road side, a first actuator connected to the first line via a first switching valve, and a first actuator connected to the second pipe line via a second switching valve. In a hydraulic circuit having a second actuator that is connected to a hydraulic cylinder of a constant discharge amount control device that faces one end of a cam plate of a variable displacement pump, the other actuator on the side that reduces the discharge amount and the second actuator of the second switching valve The cam plate is connected to the first boat, and the switching valve of Ji2 is configured so that the first boat and the second pipe are connected when neutral, and the first boat and the tank are connected when switching. a pilot boat for a horsepower limiting device that is connected to the other end and controls the input of the variable displacement pump; and a pilot boat for the operating rod of the nine horsepower limiting device that is arranged in parallel with the hydraulic cylinder and faces one end of the cam plate. Port and discharge 1 of variable displacement pump
Hydraulic control device that was created by installing *1.

Claims (1)

[Claims] A variable volume pump driven (by a re-engine);
A 70-depider that divides the discharge oil of this variable displacement pump into the 1f line and the second line and has a restrictor on the first line side is connected to the first line through a first switching valve. l to the first actuator and the second pipe line via the second switching valve.
A hydraulic circuit having a 20th actuator and a 9th actuator connected to one end of the cam plate of the variable displacement pump is connected to one chamber on the discharge volume increasing side of the hydraulic cylinder of the constant discharge volume control device and 70- It branches from the downstream side of the restrictor O of the depider and connects it to the 9th third sound passage, and connects the other chamber of the hydraulic cylinder to the 1st port of the 2nd switching valve. An oil stop control device characterized in that when the switching valve is in neutral, the first port and the second viewing path are connected to each other, and when the switching valve is switched, the ill boat and tank are connected. (2) A variable displacement pump driven by an engine, a flow divider that divides oil discharged from the variable displacement pump into a first pipe line and a second pipe line and has a restriction on the 1f line side, and a 1st V In a hydraulic circuit having a first actuator connected to the circuit via a first switching valve and a second actuator connected to a second pipe line via a second switching valve, a variable displacement type One chamber of the discharge increasing side of the hydraulic cylinder of the constant discharge rate control device, which is opposite to one end of the cam plate of the pump, is connected to the third passage ii branched from the downstream side of the restrictor of the flow divider. The other chamber on the discharge volume reduction side of the cylinder is connected to the first boat of the second switching valve, and when this l/E2 switching valve is in neutral, the first boat and the second pipe are connected, and the switching valve is connected to the first boat of the second switching valve. Sometimes, the wg1 port is connected to the tank, and the other end of the cam plate is read and connected to the pilot boat of the horsepower 1tlJ device that controls the input of the variable displacement pump, and the hydraulic cylinder. A hydraulic control device is constructed by connecting a pilot boat of a 9-horsepower limiting device which operates a 9-horsepower limiting device and connected to a discharge amount of a variable displacement pump, which is provided in contact with one end of a cam plate.