JPS62297571A - Control valve device of hydraulic cylinder for lifting/ lowering working machine - Google Patents

Abstract

PURPOSE:To enable a light and forcible opening of main and sub valves at all times irrespective of the magnitude of the hydraulic pressure in a hydraulic cylinder by providing a shaft penetrating through a sub valve seat and projecting to an open valve rod side in a sub valve. CONSTITUTION:A check valve is constructed with a main valve seat 109, a main valve 106, a sub valve seat 112 and a sub valve 107. A shaft 114 penetrating through the sub valve seat 112 and projecting to an open valve rod side so as to open the sub valve forcibly 107 prior to the main valve 106 is provided in the sub valve 107. Furthermore, the diameter of said projecting shaft 114 is reduced in step toward the tip. With such structure, main and sub valves can be opened lightly and forcibly at all times.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention A0 Objective of the Invention +11 Industrial Application Field The present invention relates to a control valve device for controlling a hydraulic cylinder for lifting and lowering a working machine installed in an agricultural tractor or the like. ,especially,
A manual valve and a check valve are installed in series from the hydraulic pump side in the oil path connecting the hydraulic cylinder for lifting and lowering the work equipment and the hydraulic pump.The manual valve releases the hydraulic oil discharged from the hydraulic pump to the oil tank. The check valve is configured so that it can be shifted to a stop position where the hydraulic oil is supplied to the hydraulic cylinder side, a raised position where the hydraulic oil is supplied to the hydraulic cylinder side, and a lowered position where the hydraulic oil from the hydraulic cylinder side is returned to the oil tank, and the check valve is moved from the hydraulic cylinder side to the manual valve side. Improved control valve device configured to prevent backflow of hydraulic fluid, and in which the manual valve is connected to a valve opening rod that forcibly opens the check valve in response to the shift of the valve to the lowered position. Regarding.

(2) Conventional technology Conventionally, this type of control valve device was developed, for example, in
This is already known as disclosed in Japanese Patent No. 841.

(3) Problems to be Solved by the Invention In the control valve device having the above configuration, when the check valve is in a closed state that prevents backflow of high-pressure hydraulic oil, the closing force of the valve due to hydraulic pressure is extremely high. However, there is a drawback in that a large operating force is required to forcefully open the valve opening rod by operating the valve opening rod in order to move the hydraulic cylinder back.

The present invention has been made in view of the above circumstances, and even when the check valve is in a closed state that prevents the backflow of high-pressure hydraulic oil, it is possible to forcefully open the check valve and cause the hydraulic cylinder to move back. It is an object of the present invention to provide a simple and effective control valve device capable of controlling the speed of return movement according to the operating amount of the valve opening rod.

B0 Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention provides a check valve that
A main valve seat that allows hydraulic oil to flow, a main valve that cooperates with the main valve seat to prevent backflow of the hydraulic oil and is forcibly opened by a valve opening rod, and a main valve that is formed on the main valve to allow the hydraulic oil to flow. Deputy Benza and
The sub-valve works with the sub-valve seat to prevent backflow of hydraulic oil and is forcibly opened by the valve opening rod.The sub-valve has a smaller pressure-receiving area than the main valve. The valve is characterized in that a protruding shaft that penetrates the auxiliary valve seat and protrudes toward the valve opening rod side is provided in order to forcibly open the valve prior to the opening, and the diameter of the protruding shaft is gradually reduced toward the tip. .

(2) Operation When both the main and auxiliary valves of the check valve are closed, when the manual valve is shifted from the stop position to the lowered position, the valve opening rod will move first, then the auxiliary valve, and then the main valve. Open the valves in sequence.

Since the sub-valve has a relatively small pressure-receiving area and a relatively small closing force due to hydraulic pressure, a small opening operation force is sufficient. When this sub-valve is opened, the hydraulic oil in the hydraulic cylinder passes through the sub-valve seat and returns to the oil tank via the manual valve, so that the hydraulic cylinder starts to move back.

During the opening process of the auxiliary valve, the flow rate of hydraulic oil at the auxiliary valve seat gradually increases due to the protruding shaft as the operating amount of the valve opening rod increases. Since the return speed of the hydraulic cylinder can be controlled in stages accordingly, the desired return speed can be easily obtained by adjusting the position of the manual valve.

When the sub-valve is opened, the pressure difference before and after the main valve remains, so the opening operation force for the main valve is also small.

By opening the main valve, the flow rate of the hydraulic oil is further increased, and the hydraulic cylinder can be quickly moved back.

(3) Embodiment An embodiment of the present invention will be described with reference to drawings. First, in FIG. 5, 5 are suspended so that they can be steered. Further, a transmission unit 4 is attached to the rear end of the vehicle body frame 2, and a pair of left and right rear wheels 6, 6 are suspended below the transmission unit 4 so as to be steerable. Further, a seat 7 for a worker is installed on the transmission unit 4.

A handle column 8 is installed upright on the vehicle body frame 2 at an intermediate position between the seat 7 and the engine 3, and the front and rear wheels 5 are connected to the handle column 8.
, 5; 6, 6 are pivoted.

The transmission unit 4 is constructed by integrally coupling a clutch 10, a transmission 11, and a rear differential 12, and a crankshaft 14 of the engine 3 is connected to an input shaft 13 of the clutch 100 via a drive shaft 15. . The rear differential 12 is arranged between the left and right rear wheels 6.6 so as to be able to drive them. Further, a front differential device 16 is disposed between the left and right front wheels 5, 5 to drive these, and its input member is a propulsion shaft 17.
The transmission member is connected to the output member of the transmission all via.

Therefore, while the engine 3 is operating, its power is transmitted to the rear wheels 6, 6 via the drive shaft 15, clutch 10, transmission 11, and rear differential 12, and then from the transmission 11 to the propulsion shaft 17 to the front wheels. 5.5 and can drive all wheels simultaneously.

At the front end of the vehicle body frame 2, a front lifting arm 21r having a hitch box 20f for connecting a working machine at the front end is pivotally supported so as to be swingable up and down. This front lifting arm 21" has a front hydraulic cylinder 22f installed on the vehicle body frame 2.
A piston 23f is connected via a link mechanism 24f, and hydraulically driven by the piston 23f, the front lifting arm 21f is raised, and when the hydraulic pressure is released, the lifting arm 21f is lowered by its own weight.

In addition, a hitch box 20 is provided at the rear end of the transmission unit 4.
A rear lifting arm 21r having a rear end 21r is pivotally supported so as to be able to swing up and down. This rear elevation! lN21r has the piston 2 of the rear hydraulic cylinder 22r installed on the transmission unit 4.
3r is connected via a link mechanism 24r, and the piston 2
The rear lifting arm 21r is raised by the hydraulic drive of the pump 3r, and the lifting arm 21r is lowered by its own weight when the hydraulic pressure is released.

A hydraulic control unit 25 for controlling the operation of the front and rear hydraulic cylinders 221.22r is attached to the transmission unit 74. This hydraulic control unit 25 has a suction pipe 27 and a return pipe 28 connected to an oil tank 26 installed adjacent to it.
(see FIG. 9), and also a hydraulic conduit 29
Front and rear hydraulic cylinders 22f and 22 via r and 29r
It is also in communication with the hydraulic chamber r, and can force the hydraulic oil sucked from the ura tank 26 to the respective hydraulic cylinders 22f and 22r, and can return the hydraulic oil to the oil tank 26.

The hydraulic control unit 25 also includes first and second control levers 31 and 32 arranged beside the seat 7, and the front and rear hydraulic cylinders 22f and 22r are controlled by operating the first control lever 3I. Select operation, second control fal
Hydraulic cylinder 22 selected by operating l lever 32
The supply and release of hydraulic pressure to f or 22r can be controlled.

Hereinafter, this hydraulic control unit 25 will be explained in detail with reference to FIGS. 2 to 12.

As shown in FIGS. 2 and 4, the hydraulic control unit 25
consists of a hydraulic pump 33 and a control valve device 34 which are arranged adjacent to each other in the left and right direction of the tractor 1, and both 33 and 34 share a casing 35 for unitization. This casing 35 is attached to the transmission unit 4
A plurality of bosses 36a protruding from the front surface of the casing 36,
The hydraulic control unit 25 is attached to the transmission unit 4 by fixing the hydraulic control unit 25 to the transmission unit 4 by fixing the hydraulic control unit 25 to the transmission unit 36a with a plurality of pins 37 and 37.

The hydraulic pump 33 has a casing 3 as shown in FIG.
The shafts 39a of the pump gears 39 and 40 are configured in a gear type having a pair of pump gears 39 and 40 that are accommodated in the gear chambers 38 of 5 and mesh with each other.

One end of 40a is a front end plate 4 that closes the front surface of gear chamber 38.
1 and the other end are respectively supported by bearing blocks 42 fitted in the gear chamber 38 together with the pump gears 39 and 40, and this bearing block 42 is fitted with a rear end plate 43 that closes the rear surface of the gear chamber 38. position. Both end plates 41.43 are connected to each other with the casing 35 sandwiched therebetween by a plurality of through bolts 44.44.

On the back of the rear fM4N, 43 is one pump gear 39.
A connecting cylinder 43a that faces the shaft 39a inward is integrally protruded, and when the casing 35 is attached to the transmission unit 4, the connecting cylinder 43a is connected to the power outlet 45 that opens in the casing 36 of the transmission unit 4. A shaft 39a of the pump gear 39 is connected via a joint 48 to a pump drive shaft 47 that is fitted through a seal member 46 and interlocks with the manual member of the clutch 10. Since the hydraulic pump 33 is driven by the input member of the clutch 100 in the transmission unit 4 in this way, the hydraulic pump 33 is always maintained in an operating state while the engine 3 is operating, regardless of whether the clutch 10 is opened or closed, and the hydraulic pressure is maintained. can be secured.

A suction boat 50 and a discharge boat 51 are bored in the casing 35 and open into the gear chamber 38 across the meshing portion of the single pump gears 39 and 40. These ports 1-50.51 are arranged linearly along the arrangement direction of the hydraulic pump 33 and the control valve device 34.

Such an arrangement is effective in allowing the shell cores of each part to be easily discharged through these boats 50, 51 after the casing 35 is cast.

A connecting short pipe 52 is fitted into the inlet of the suction boat 50, and the suction pipe 27 is connected to this.

As shown in FIG. 7, FIG. 9, and FIG. A manual valve 56 that controls the supply and release of hydraulic pressure to, a throttle valve 57 that adjusts the operating speed of each hydraulic cylinder 22f, 22r, each hydraulic cylinder 22f,
It consists of a check valve 58 that stops the double movement of the hydraulic pump 22r, a relief valve 59 that defines the upper limit of the discharge pressure of the hydraulic pump 33, and a safety valve 60 that avoids overload, and these are housed in the casing 35 as follows. .

That is, as shown in FIGS. 3, 7, and 8, the casing 35 has a first valve hole 61 that extends perpendicularly to the arrangement direction of the hydraulic pump 33 and the control valve device 34, and a first valve hole 61 that extends at right angles to the arrangement direction of the hydraulic pump 33 and the control valve device 34. 6
A second valve hole 62 extends above and parallel to the second valve hole 62, and a hydraulic pump 33 and a control valve device 34 are connected above the second valve hole 62.
a third valve hole 63 extending in the arrangement direction;
A fourth valve hole 64 is bored above and parallel to the fourth valve hole 64, and a manual valve 56 is installed in the first valve hole 61, and a manual valve 56 is installed in the second valve hole 62.
A check valve 58 and a safety valve 60 are disposed in the third valve hole 63 , a throttle valve 57 is disposed in the fourth valve hole 64 , a switching valve 55 is disposed in the fourth valve hole 64 , and a relief valve 59 is built in the manual valve 56 .

In FIG. 9, the outlet of the discharge boat 51 of the hydraulic pump 33 opens directly into the first valve hole 61, thereby allowing the hydraulic pump 33 and the control valve device 34 to communicate with each other.

Further, a supply boat 65 and a discharge boat 66 open to the I-th valve hole 61 with the outlet of the discharge boat 51 interposed therebetween, and the outlet of the supply boat 65 opens to the second valve hole 62 . A high-pressure boat 67 opens in the second valve hole 62, and a central boat 68 opens in the fourth valve hole 64, and a middle part of an oil passage 69 connecting these boats 67 and 68 is coaxial with the third valve hole 63. Aperture hole 70
is formed. Further, the fourth valve hole 64 has a central boat 68.
A pair of front and rear output ports 71f and 71r are opened with the front and rear output ports 71f and 71r in between.
The hydraulic conduits 29f and 29r are connected to the rear hydraulic cylinders 22f and 22r, respectively.

The outlet of the υ outlet port 66 communicates with the oil chambers 72 and 73 formed on both front and rear sides of the casing 35 via an oil passage 74, and supplies oil to the outlet lower 5 which opens into the front oil chamber 72. The return pipe 28 connected to the tank 26 is connected. Therefore, the oil discharged into the oil chambers 72, 73 is returned to the oil tank 26.

Each open surface of the oil chamber 72.73 has a rear end tff176 before being fastened to the casing 35 with a pole 1-78.79.
．． 77 (see FIG. 5).

Now, to explain the structure of each of the above-mentioned fields, first, the switching valve 55 is formed in the shape of a cock which rotatably fits into the fourth valve hole 64 as shown in FIGS. 7 and 8. The central boat 68 can be selectively communicated with the front and rear output port doors 1f and 71r. This switching valve 55 has one end protruding from the right side surface of the casing 35, and the first control lever 31 is attached to it. Therefore, when the first control lever 31 is rotated, the switching valve 55 is rotated.

A regulating plate 82 for regulating the rotation range of the first control lever 31 is fixed to the casing 35 with bolts 83 (see FIG. 5). This regulating plate 82 is connected to the circumferential groove 84 of the switching valve 55.
(See Fig. 8) and also functions to prevent it from coming off.

The manual valve 56 has a first valve hole 6 as shown in FIG.
It is formed into a spool shape that is slidably fitted into the holder 1, and has three positions: a stop position A in the center, a raised position B on the negative side, and a lowered position C on the other side. This manual valve 56
A pin 87 is protruded from the side surface of one end projecting into the rear oil chamber 73, and a fork 88 fixed to the rotation shaft 32a of the second control lever 32 is engaged with the pin 87.

Therefore, the manual valve 5G is slidably operated by the recess vJ of the second control lever 32.

The manual valve 56 includes, in order from the left in Fig. 9, a first land 901, a first large group 91 for discharge (see Fig. 8), a first small group 92 for ascending throttle, (see Fig. 10). , a second land 90□, a second small group 92□ for descending throttle (see FIG. 11), and a second large group 91z for discharge. The discharge boat 51 and the discharge boat 66 are communicated via the
, to cut off the discharge boat 51 and the discharge boat 66, and the second land 90□ to cut off the supply boat 65 and the front oil chamber 72, and at the same time, the first large group 91. communicates between the discharge boat 51 and the supply boat 65 via
Further, at the lowered position C, when the discharge boat 51 and the supply boat 65 are cut off by the second land 90□, communication is established between the supply boat 65 and the front oil chamber 72 via the second large group 91□. Further, at each intermediate position between the stop position A, the upper W position B, and the lowered position C, the first small group 92. Alternatively, the second small group 92□ intervenes.

Each of the above groups 91. ．． 91□, 92. ．． 922 is formed by chamfering opposing portions of the outer peripheral surface of the manual valve 56. In this way, a sliding surface that is not cut into groups remains on the outer periphery of the manual valve 56 over its entire length, so that good sliding properties of the contact area 56 can be obtained.

The manual valve 56 has a large-diameter valve chamber 93 extending in the axial direction, a small-diameter guide hole 94 coaxially connected to the inner end of the valve chamber 93, and a guide hole 94 adjacent to the valve chamber 93. 1 large group 91. A through hole 95 that communicates with the front oil chamber 72 and a through hole 96 that opens the valve chamber 93 to the front oil chamber 72 are provided, and an inner end wall of the valve chamber 93 is formed in a valve seat 97 . The valve chamber 93 has a valve seat 97
A conical valve 98 that cooperates with the conical valve 98 and a valve spring 99 that biases the contact area 98 in the closing direction, that is, toward the valve seat 97, are housed, and these constitute the relief valve 59.

The conical valve 98 integrally includes a valve rod 98a that extends across the through hole 95, and a small piston 98b that is formed at the tip of the valve rod 98a and slides into the guide hole 94.

In the front oil chamber 72, one end of the manual valve 56 has a
A bolt 100 is screwed to support the fixed end of the valve spring 99, and at this time, the manual valve 56 and the bolt 1
00, the interlocking arm 101 for opening the check valve 58, which will be described later, is clamped.

As clearly shown in FIG. 9A, the check valve 5 includes a valve cylinder 105 that is fitted into the second valve hole 62 and whose end communicates with the supply boat 65, and a valve cylinder 105 disposed within the valve cylinder 105. The main valve 106 includes a cup-shaped main valve 106, a sub-valve 107 disposed within the main valve 106, and a valve spring 108 that biases the sub-valve 107 in the closing direction. The one end of the valve cylinder 105 is formed into a main valve seat 109 that cooperates with the main valve 1.6, and the end of the main valve 106 opposite to the main valve seat 109 is formed with the main valve 106.
A piston 106a that slides on the inner circumferential surface of the valve cylinder 105 is embedded integrally to prevent the valve from tilting.

The valve cylinder 105 is located before and after this piston 106a.
Through holes 110 and 111 that communicate the inside of the with the high pressure boat 67
is bored in the valve cylinder 105.

The end wall of the cup-shaped main valve 106 is formed with a sub-valve seat 112 that cooperates with a sub-valve 107, and a piston 107a that slides on the inner circumferential surface of the main valve 106 at a position apart from the sub-valve seat 112.
is integrally connected to the sub-valve 107, so that the sub-valve 107
is prevented from tilting.

The main valve 106 is connected between the piston 107a and the sub-valve seat 112.
The main valve 106 has a through hole 113 that communicates the inside of the main valve 106 with its outer peripheral side.
to be drilled.

A protruding shaft 114 passing through the sub-valve seat 112 is integrally connected to the sub-valve 107, and this protruding shaft 114 is connected to the large-diameter portion 114 on the base end side.
A and a small diameter portion 114b on the tip side form a two-stage shape. A valve opening rod 115 is disposed opposite the tip of the protruding shaft 114. The valve opening rod 115 is slidably supported on the partition wall between the second valve hole 62 and the front oil chamber 72, and is connected to the interlocking arm 101 in the front oil chamber 72, so that the manual valve 56 is stopped. During operation from position A to lowered position C, the protruding shaft 114 and the main valve 106 are sequentially pushed.

In order to press and fix one end of the valve cylinder 105 to the step portion 62a of the second valve hole 62, the valve cylinder 105 is inserted into the second valve hole 62.
A partition member 118 abutting the other end is fitted, and
A hollow bolt 119 that fixes the partition member 118 is screwed. The hollow portion of this bolt 119 is closed at its open end with a screw plug 120 to form a valve chamber 121. On the side of this valve chamber 121, a partition member 118 has a valve seat 12 that communicates with the inside of the valve cylinder 105.
6 is formed. A spherical field 122 cooperates with this valve seat 126, and this spherical field 122 is connected to a conical recess 123 on the front surface.
A retainer 123 supported by a and a valve spring 124 that biases the spherical field 122 in the closing direction via the retainer 123 are housed in the valve chamber 121.
0 is configured.

The valve chamber 121 is opened to the rear oil chamber 73 through a through hole 125 formed in the bolt 119.

Referring again to FIG. 9, the throttle valve 57 is screwed into the third valve hole 63. The throttle valve 57 has a tapered portion 57a inserted into the throttle hole 70 at its inner end, and a hexagonal head 57 at its outer end.
b are provided respectively, and by fitting a spanner into the head 57b and rotating it, the taper portion 57a can be advanced or retreated depending on the direction of rotation to increase or decrease the opening degree of the throttle hole 70, and the opening degree of the throttle hole 70 can be increased or decreased. The throttle hole 70 can be closed at the limit.

Next, to explain the operation of this embodiment, FIG. 9 shows a state in which the manual valve 56 is placed at the stop position A. If the hydraulic pump 33 is operating in this state, the hydraulic oil sucked from the oil tank 26 by the hydraulic pump 33 and discharged to the discharge boat 51 will be transferred to the first large group 9I of the manual valve 56.
0, the discharge boat 51 returns to the oil tank 26 without resistance via the discharge boat 66, the oil passage 74, and the front oil chamber 72.
High oil pressure is not generated.

At this time, if the switching valve 55 is placed in a position communicating with the central boat 68 and the rear output port door 1r, the rear lifting arm 21
The hydraulic pressure generated in the hydraulic chamber of the rear hydraulic cylinder IJ cylinder 22r due to its own weight (actually, the weight of the work equipment connected to it is also added) passes through the switching valve 55, the throttle hole 70, and the high pressure boat 67 to the check valve 58. The hydraulic fluid is transmitted to the inside of the valve cylinder 105 and acts on the back surfaces of both the main and auxiliary valves 106, 107 to keep them closed, so the hydraulic oil does not flow out from the rear hydraulic cylinder 22r and the rear lifting arm 21r The current position can be maintained.

When the working machine connected to the hitch box 20r of the rear lifting arm 21r receives an overload in the downward direction during work, the oil pressure in the valve cylinder 105 of the check valve 58 increases, and the sphere 122 of the safety valve 60 increases. Since the valve opens while contracting the valve spring 124 in response to the hydraulic pressure at the front, the excess hydraulic pressure is released to the rear oil chamber 73 side through the valve seat 126, valve chamber 121 and through hole 125, and the work machine is overloaded. can be protected from.

Now, in order to raise the rear lifting arm 21r, the manual valve 56 is moved to the raising position 1117 by operating the second control lever 32.
When shifting to B, the first land 90 first blocks the discharge boat 51 and the discharge boat 66, and the second land 90□ blocks the supply boat 65 and the front oil chamber 7.
Since the space between the two is cut off, hydraulic pressure is generated in the discharge boat 51 by the hydraulic pump 33. And the discharge boat 51
is the first small group 92. When communicating with the supply boat 65 via the first small group 92, the hydraulic pressure is transmitted to the supply boat 65 side while being subjected to a throttling action in the first small group 92, and then acts on the front surface of the main valve 106 of the check 58. is pushed open and transmitted to the hydraulic chamber of the rear hydraulic cylinder 22r via the main valve seat 109, the hole 110 of the valve cylinder 105, the high pressure port 67, the throttle hole 70, the central boat 6, the switching valve 55, and the rear output port 71r. This oil pressure drives the piston 23r to raise the rear lifting arm 21r, but the rate of rise is mainly determined by the first small group 92. of the manual valve 56. The speed is controlled slowly by the throttling action of The speed of this slow increase can be slightly adjusted by adjusting the opening degree of the throttle hole 70 using the throttle valve 57.

When the manual valve 56 is shifted to the ascending position ff1B, the first large group 91. As a result, the transmission speed of hydraulic pressure increases, and the speed at which the rear lifting arm 21r rises is accelerated. However, even in this case, since the throttle valve 57 restricts the throttle hole 70 to a certain extent and regulates the upper limit of the transmission speed of the hydraulic pressure, a sudden rise of the rear elevation arm 21r is suppressed.

During the above action, the discharge pressure of the hydraulic pump 33 acts on the front surface of the conical valve 9B of the relief valve 59 through the through hole 95, so that the discharge pressure rises above the specified value determined by the cent load of the valve spring 99. Then, the conical valve 98 opens against the force of the valve spring 99 and releases the excess discharge pressure into the valve chamber 93.
and is discharged to the front oil chamber 72 side through the through hole 96. When the discharge pressure of the hydraulic pump 33 returns to the specified value due to this pressure release, the conical valve 98 returns to the closed state by the force of the valve spring 99.

During such opening/closing operations of the conical valve 98, the small piston 98b integrated therewith slides in the guide hole 94, thereby preventing the conical valve 98 from tilting. Also small piston 9
The oil flowing through the sliding gap between the guide hole 8b and the guide hole 94 can prevent the conical valve 98 from being disturbed.

Next, in order to lower the rear lifting arm 21r, the manual valve 5
When the supply boat 65 is shifted beyond the stop position ff1A to the lowering position C, the supply boat 65 is first cut off from the discharge boat 51 by the second land 90□, and is also It communicates with the front oil chamber 72, and then the protruding shaft 114 of the sub-valve 107 in the check valve 58 is pushed by the valve-opening rod 115 to open the sub-valve 107. The pressure receiving area of this sub valve ↑107 facing into the valve cylinder 105 is relatively small, so the sub valve 1 due to the high oil pressure inside the valve cylinder 105
Since the valve closing force of valve 07 is relatively small, the sub valve 107 can be easily opened by a light pushing force of the valve opening rod 115.

When the sub-valve 107 opens, the hydraulic pressure of the rear hydraulic cylinder 22r is applied to the switching valve 55, the throttle hole 70, the high-pressure boat 67, and the valve cylinder 105.
through hole 110 of main valve 106, through hole 113 of main valve 106, sub valve seat 112
, the supply boat 65 and the second small group 92□ and are discharged into the front oil chamber 72, so that the rear lifting arm 21r can be lowered, and the lowering speed is the same as that of the sub valve 107 and the second small group. The speed is controlled slowly by the throttling action of group 92□.

Therefore, the opening degree of the sub-valve 107 is determined by the protruding shaft 114 at the initial stage of opening.
The throttle action by the auxiliary valve 107 changes into two levels of strength and weakness as the valve opening rod 115 moves forward, and is controlled to a small degree by the large diameter part 114a of the valve opening. Accordingly, the slow control U of the descending speed of the rear lifting arm 21r can be performed in two slow stages. Furthermore, the speed can be minutely adjusted by adjusting the opening of the throttle hole 70 using the throttle valve 57.

When the sub valve 107 opens, the pressure difference between the inside and outside of the main valve 106 decreases, so the valve opening rod 115 is further advanced to open the main valve 10.
By pushing 6, you can easily open the valve.

When the main valve 106 opens, the hydraulic pressure from the rear hydraulic cylinder 22r is quickly released through the main valve seat 109, so that the lowering speed of the rear lifting arm 21r is accelerated. but,
At this time, if the second small group 91□ is still interposed between the supply boat 65 and the front oil chamber 72, the increase in the descending speed of the rear lifting arm 21r can be appropriately suppressed by its throttling action.

When the manual valve 56 is shifted to the lowered position C, the second large group 91 is moved between the supply boat 65 and the front oil chamber 72.
□, the release speed of hydraulic pressure from the rear hydraulic cylinder 22r is further accelerated, and the lowering speed of the rear lifting arm 2■r becomes maximum. This maximum downward speed is limited by the opening degree of the throttle hole 70 adjusted by the throttle valve 57.

The above has described the raising and lowering of the rear lifting arm 21r, but if the central boat 68 is communicated with the front output port door 1f by switching the switching valve 55, the front lifting arm 21f is raised and lowered by the same action as described above. It is understood that this is possible.

When the front and rear lifting arms 21r, 21r are stopped at appropriate raised positions and the tractor 1 is left for a long time, the throttle valve 57 is sufficiently tightened to close the throttle hole 70. In this way, for example, as shown in FIG. 9, even if the rear output capo 71r connected to the rear hydraulic cylinder 22' communicates with the central boat 6th via the switching valve 55, the safety valve 60 on the hydraulic circuit The throttle valve 57 interposed between the switching valve 55 and the rear hydraulic cylinder 22r reliably prevents hydraulic pressure from being discharged, so that the rear lifting arm 21f is held immobile for a long period of time regardless of the magnitude of the load applied thereto. On the other hand, since the front output port door 1 connected to the front hydraulic cylinder 22f is closed by the switching valve 55, the front lifting arm 21f is also kept stationary for a long time regardless of the magnitude of the load applied to it. can do.

C9 Effects of the Invention As described above, according to the present invention, the check valve is forcibly opened by a main valve seat through which hydraulic oil flows, and a valve opening rod that cooperates with the main valve seat to prevent backflow of hydraulic oil. A main valve is formed on the main valve, a sub-valve seat is formed on the main valve to allow hydraulic oil to flow, and the main valve is forcibly opened by a valve-opening rod. Consists of a sub-valve with a smaller pressure-receiving area than the valve, and the sub-valve has a protruding shaft that penetrates the sub-valve seat and protrudes toward the valve opening rod in order to forcibly open the contact field before the main valve. Therefore, when the manual valve is shifted to the lower position, the closing force of the hydraulic pressure of the sub-valve that opens first is small, and when the sub-valve is opened, the pressure difference before and after the main valve decreases, so that the pressure of the hydraulic cylinder is reduced. Regardless of the level of oil pressure, the main control valve can always be easily and strongly controlled.

In addition, since the diameter of the protruding shaft is gradually reduced toward the tip, the flow rate of hydraulic oil at the sub-valve seat can be controlled in stages according to the amount of actuation of the valve opening rod during the opening process of the sub-valve. Therefore, the return speed of the hydraulic cylinder can be easily adjusted by adjusting the position of the manual valve.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a side view of an agricultural tractor, FIG. 2 is a plan view of a unitized hydraulic pump and control valve device in the hydraulic system of the agricultural tractor, and FIG. Figures and Figure 4 are Iff III of Figure 2.
Figure 5 is a cross-sectional view taken along the line IV-IV in Figure 2, Figure 6 is a cross-sectional view taken along the VI-VT line in Figure 4, and Figure 7 is a cross-sectional view taken along the line VI-VT in Figure 4.
8 is a sectional view taken along the line ■-■ in FIG. 7, FIG. 9 is a vertical sectional view of the control valve device, FIG. 9A is an enlarged view of a part of FIG. Figures 10 and 11 are X-X in Figure 9.
12 is a hydraulic circuit diagram of the hydraulic system.

Claims (1)

[Claims] A manual valve and a check valve are installed in series in the oil passage connecting the hydraulic cylinder for lifting and lowering the work equipment and the hydraulic pump, starting from the hydraulic pump side, and the manual valve is operated by the discharge from the hydraulic pump. The check valve is configured to be shiftable to a stop position where oil is released to the oil tank, a raised position where the hydraulic oil is supplied to the hydraulic cylinder side, and a lowered position where the hydraulic oil from the hydraulic cylinder side is returned to the oil tank. It is configured to prevent backflow of hydraulic oil from the cylinder to the manual valve side, and the manual valve is connected to a valve opening rod that forcibly opens the check valve in response to the shift of the valve to the lowered position. In a control valve device for a hydraulic cylinder for lifting and lowering work equipment, the check valve is forcibly opened by a main valve seat that allows hydraulic oil to flow, and a valve opening rod that works with this main valve seat to prevent backflow of hydraulic oil. A main valve is formed on the main valve, a sub-valve seat is formed on the main valve to allow hydraulic oil to flow, and the main valve is forcibly opened by a valve-opening rod. Consists of a sub-valve with a smaller pressure-receiving area than the valve, and the sub-valve is connected to a protruding shaft that penetrates the sub-valve seat and protrudes toward the valve opening rod in order to forcibly open the valve before the main valve. A control valve device for a hydraulic cylinder for lifting and lowering a working machine, characterized in that the diameter of the protruding shaft is gradually reduced toward the tip.