JPH02128604A - Hydraulic device for riding tractor - Google Patents

Abstract

PURPOSE:To eliminate the need for piping of an oil return hose between a frontal lifting cylinder and a front and back changeover block and simplify a piping structure by providing an overload escape valve in the front and back changeover block. CONSTITUTION:A front and back changeover block 30 is collectively provided with the first and second poppet valves 641 and 642, a cam shaft 65, a slow lowering valve 66 and an overload escape valve 67 and removed from a distribution block 29 to facilitate inspection, maintenance, etc. Since the front and back changeover block 30 is provided with the slow lowering valve 66 and overload escape valve 67, the structure of a front lifting cylinder 14 is simplified and only connection of one hydraulic hose 111 to the frontal lifting cylinder 14 is sufficient. Thereby, the piping structure is also simplified.

Description

Detailed Description of the Invention A0 Objective of the Invention (1) Industrial Application Field The present invention provides a front lift cylinder for raising and lowering a working machine connected to the front end of a vehicle body, and a front lift cylinder for raising and lowering a working machine connected to the rear end of a vehicle body. a rear lift cylinder, a hydraulic source, and a front/rear switching valve that selectively connects the hydraulic source to the front lift cylinder or the rear lift cylinder to supply pressure oil to the front lift cylinder or the rear lift cylinder to provide a lifting motion; , a gradual lowering valve that regulates the speed of oil discharge from the front lift cylinder when the front lift cylinder is lowered, and an overflow valve that releases the excess oil pressure when the oil pressure in the front lift cylinder rises excessively. The present invention relates to a hydraulic system for a riding tractor, which is equipped with a load relief valve.

(2) Prior Art In the conventional hydraulic system, a front/rear switching valve is provided in the cylinder head of the rear lift cylinder, and the front lift cylinder 1-
A slow descent valve and an overload relief valve are provided in the cylinder head of the cylinder.

(3) Problems to be Solved by the Invention In the conventional structure as described above, in addition to the hydraulic hose connecting the front/rear switching valve provided on the rear lift cylinder and the front lift cylinder, there is also a hydraulic hose provided on the front lift cylinder. A long oil return hose is required from the overload relief valve to the oil sump, resulting in a total piping length of 71M.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide the above-mentioned hydraulic system with a simple piping structure that does not require an oil return hose from the front lift cylinder.

B0 Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention installs a distribution block in the vicinity of the rear lift cylinder, which has a first oil passage connected to a hydraulic power source. The distribution block is provided with a second oil passage connected to the rear lift cylinder, and the front/rear switching block joined to the distribution block is provided with a third oil passage connected to a hydraulic hose connecting the block and the front lift cylinder, and a first oil passage connected to the rear lift cylinder. A front/rear switching valve that selectively communicates the oil passage with the second oil passage or the third oil passage, a slow descent valve connected to the third oil passage, and an overload relief valve also connected to the third oil passage. It is characterized by having the following.

(2) Effects According to the above configuration, the front lift cylinder or the rear lift cylinder can be connected to the hydraulic power source by operating the front/rear switching valve, and a lifting operation can be selectively applied to these lift cylinders.

The lowering movement of the front lift cylinder is controlled by the slow descent valve, which controls the oil discharge speed from it to a low speed.
It is done slowly.

When the hydraulic pressure in the front lift cylinder increases excessively due to an excessive load being applied to the front lift cylinder, the excess amount is released from the overload relief valve to the oil sump through the front/rear switching block, and thus the AR weight is absorbed. Since the overload relief valve is provided in the front/rear switching block, there is no need to install an oil return hose between the front lift cylinder and the front/rear switching block.

(3) Examples An embodiment of the present invention will be described below with reference to the drawings.

First, in FIG. 1, an engine 3 is mounted on the front portion of a body frame 2 of a riding type tractor 1, and a pair of left and right front ends 4 are suspended so as to be steerable. A transmission unit 5 is attached to the rear end of the vehicle body frame 2, and a pair of left and right rear wheels 6 are suspended below the transmission unit 5 so as to be steerable.

Further, a worker seat 7 is disposed above the transmission unit 5, and the front end of the seat 7 is supported via a pivot 9 by a bracket 8 fixed to the upper surface of the transmission unit 5, and the seat 7 is in the normal use position (the position shown by the solid line). and a forward-leaning maintenance position (position shown by chain lines).

At an intermediate position W between the seat 7 and the engine 3, a handle column 10 is erected on the vehicle body frame 2, and a handle wheel 11 for steering the front and rear wheels 4, 6 is pivoted on this column. be done.

The transmission unit 5 includes a clutch, a transmission, a rear differential, and a front wheel drive shaft so that it can receive power from the engine 3 and drive not only the rear wheels 6 but also the front wheels 4.

At the front end of the vehicle body frame 2, an elevating arm 13 having a hitch box 12 at the front end for connecting a working machine is pivotally supported so as to be able to swing downward. This elevating arm 13 has a vehicle body frame 2
A piston 15 of a single-acting front lift cylinder 14 installed above is connected via a link mechanism 16, and the piston 1
The lifting arm 13 is raised by the hydraulic drive of 5, and the lifting arm 13 is lowered by its own weight by releasing the hydraulic pressure.

As shown in FIGS. 1 and 2, a rear lift cylinder 17 is installed on the transmission unit 5 directly below the seat 7, and a working machine 18 such as a rotary tiller, which is raised and lowered by the rear lift cylinder 17, is connected to a link mechanism. It is connected to the rear end of the transmission unit 5 via 19.

The link mechanism 19 includes one top link 20 that is pivotally supported to the transmission unit l-5 so as to be able to swing vertically, and a left and right link that is pivotably supported to the transmission unit 5 below the top link 20 so as to be pivotable up and down. A pair of lower links 21 and 21 are provided to allow the working machine 18 to move up and down with respect to the tractor 1 and tilt left and right. Further, the link mechanism 19 includes a pair of left and right lift arms 2222, and these lift arms 2.
a pair of left and right lift rods 23.23 connecting the 2° 22 to the 11th lower link 21.21, respectively;
The foot arms 22, 22 shown in are attached to the rear lift cylinder 1.
It is fixed to an elevating drive shaft 25 that is linked to a piston 24 of No. 7.

Thus, the lift arm 2 is hydraulically driven by the piston 24.
According to the upward swing of 2, the working machine 18 can be raised via the link mechanism 19, and when the hydraulic pressure is released, the working machine 18 can be lowered by its own weight.

One of the pair of lift rods 23, 23, the right lift rod 23' in the illustrated example, is partially configured with a double-acting telescoping cylinder 26 to be extendable and retractable, and the operation of the telescoping cylinder 26 This allows the work implement 18 to be tilted left and right with respect to the tractor 1 and maintained in a horizontal state.

A hydraulic control device 28 for controlling the supply of pressure oil to the three cylinders 14, 17.26 and the external hydraulic loader 27 is provided on one side of the rear lift cylinder 17, on the right side in the illustrated example.

As shown in FIG. 3, this hydraulic control device 28
A substantially cubic distribution block 2 is removably connected to the right side of the rear lift cylinder 17 with bolts directly below the rear lift cylinder 17.
9, a front-rear switching block 30 detachably joined to the rear R of the distribution block 29 with bolts, a horizontal control block 31 detachably attached to the front F of the distribution block 29, and an outer surface of the distribution block 29. As shown in FIG. 4, the system is composed of an ascending control valve 32 and a descending control valve 33 that are detachably attached to the upper surface T of the distribution block 29, and a hydraulic pressure take-out bronck 34 that is detachably attached to the upper surface T of the distribution block 29. In addition, the distribution block 29 includes a main relief valve 35 and a diversion valve 3.
6, an unload valve 37, a one-way valve 38 and a lowering valve 39 are provided. Oil passage 40 connected to the inlet of the main relief valve 35
Oil in an oil reservoir 57 is pumped by a hydraulic pump 56.

The hydraulic pump 56 is attached to the transmission unit 5 and driven by a clutch input member therein, and the oil reservoir 57 is formed by the bottom wall of the transmission unit 5.

Pressure oil sent from the hydraulic pump 56 and regulated by the main relief valve 35 flows into the inlet 36a of the branch valve 36 via the oil passage 40, the oil pressure outlet block 34, and the oil passage 41. Then, the diversion valve 36 allows a constant flow of pressure oil to flow out from the first outlet 36b and the remaining pressure oil from the second outlet 36c, and the pressure oil from the first outlet 36b passes through the oil path 42. Pressure oil from the horizontal control block 31 and the second outlet 36c is sent to the ports 37a and 38a of the unload valve 37 and the one-way valve 38 via the oil passage 43.

The one-way valve 38 opens only when the pressure at the outlet 38a becomes higher than that at the outlet 38b, and the outlet 38b communicates with the inlet 39a of the descending valve 390, and also communicates with the front/rear switching block 30 via the oil passage 44. do.

The descending valve 39 has a valve body 58 that opens and closes between the opening 39a and the opening 39b, and a back pressure chamber 59 into which hydraulic pressure can be introduced to press the valve body 58 toward the closing side. 59 is the above-mentioned population 3 through an orifice 60 provided in the valve body 58.
It communicates with 9a. The outlet 39b is open to the oil sump 57, and the control oil passage 48 extending from the back pressure chamber 59 communicates with the oil sump 57 via the lowering control valve 33.

The unloading valve 37 has a population 37a, a protrusion 3b, and a back pressure chamber 62 into which hydraulic pressure for pressing toward the closing side can be introduced.
3 communicates with the population 37a. Further, the outlet 37b is open to the oil reservoir 57, and the control oil passage 49 extending from the back pressure chamber 62 communicates with the oil reservoir 57 via the rise control valve 32.

The rise control valve 32 is constituted by a normally open solenoid valve,
Further, the descending control valve 33 is constituted by a normally closed solenoid valve.

When the lift control valve 32 is closed while the drop control valve 33 is closed in order to give the front lift cylinder 14 or the rear lift cylinder 17 a lift operation, the unload valve 3 is closed.
In step 7, the pressure oil coming out of the second outlet 36c of the diverter valve 36 passes through the orifice 63 and is held in the back pressure chamber 62, so that the valve body 61 receives the oil pressure and closes the inlet 37a. Further, in the descending valve 39 as well, the pressure oil that has passed through the one-way valve 38 passes through the orifice 60 and is held in the back pressure chamber 59, so that the valve body 58 receives the oil pressure and closes the outlet 39b. As a result, the pressure oil that has passed through the one-way valve 38 is transferred to the oil passage 44 and the front/rear switching valve.
via the link 30 to the front lift cylinder 14 or the rear lift cylinder 17, giving them a lifting motion.

In addition, in order to give a downward movement to the front lift cylinder 14 or the rear lift cylinder 17, when the downward control valve 33 is opened with X while the upward control valve 32 is open, the back pressure chamber 6259 of the unload valve 37 and downward valve 39 is opened to the oil sump 57 via the rise control valve 32 and the fall control valve 33, respectively, so the valve bodies 61 and 5B open by the pressure of the respective inlets 37a and 39a in the unload valve 37 and the fall valve 39,
The pressure oil that has exited the second outlet 36e of the diversion valve 36 passes through the unload valve 37, that is, returns to the oil sump 57 from its outlet 37b. Further, the oil that was first sent to the front lift cylinder 14 or the rear lift cylinder 17 passes through the front/rear switching block 30 and the lowering valve 39, that is, its outlet 39b.
The oil is then refluxed to the oil sump 57. As a result, the front lift cylinder 14 or the rear lift cylinder 17 performs a landing motion due to the weight of its load side.

The front and rear switching block 30 includes first and second poppet valves 6.
4. ．． 64z, a camshaft 65 for opening and closing these poppet valves 64164□, a gradual lowering valve 66, and an overload relief valve 67 are provided.

The first and second poppet valves 641, 64□ are both normally closed types, and the camshaft 65 has different phases to alternately open and close these poppet valves 641, 642 by reciprocating rotation at a predetermined angle. A pair of cams 65a and 65b are provided. This camshaft 65 is rotated by a switching lever 68 fixed to one end thereof. Both poppet valves 64.
, 64□ and the camshaft 65 constitute the front/rear switching valve of the present invention.

First and second poppet valves 64. ．． The inlets 642 communicate with each other and with the oil passage 44. Also the first
Poppet valve 64. The outlet of the oil passage 45 in the distribution block 29 and the oil passage 1 passing through the wall of the rear lift cylinder 17
10 to the hydraulic chamber 7o of the rear lift cylinder 17, and the outlet of the second poppet valve 64□ is connected to the lowering valve 66.
It communicates with the entrance 66a of the.

Then, the camshaft 65 is rotated in one direction to open the first poppet valve 64. When only the rear lift cylinder 17 is opened, only the rear lift cylinder 17 is communicated with the oil passage 44 of the distribution block 29, and the lift control valve 32 is opened.
By controlling the lowering control valve 33 as described above, the vertical movement becomes possible. Also, the camshaft 65 is rotated in the other direction and the second
By opening only the poppet valve 64□, the rear lift cylinder 1
7 is communicated with the oil passage 44, and the lifting control valve 32 and the lowering control valve 33 are controlled to enable vertical movement.

The slow F valve 6G includes a check valve 71 that allows oil to flow from the inlet 66a to the outlet 66b but prevents oil from flowing in the opposite direction, and an adjustment bolt 72 that adjusts the minimum opening degree of the check valve 71. The outlet 66b is connected to the front lift cylinder 1 via an oil passage 47 and a hydraulic hose 111 (see FIG. 1) extending from the front/rear switching block 30.
It is connected to the hydraulic chamber 69 of No. 4.

Therefore, when the pressure oil that has passed through the second poppet valve 64□ flows into the inlet 66a of the slow-down valve 66, the check valve 71
opens wide, the pressure oil quickly passes through the slow descent valve 66 and is supplied to the hydraulic chamber 69 of the front lift cylinder 14.
Give it a rising motion at a relatively fast speed. On the contrary, during the descending operation, the oil discharged from the hydraulic chamber 69 flows backward from the outlet 66b of the gradual descending valve 66 to the inlet 66a.
The check valve 71 is held at a minimum opening degree by an adjustment bolt 72 to regulate the oil discharge speed. As a result, the front lift cylinder 14 performs a landing operation at a slow speed.

The overload relief valve 67 has its inlet connected to the outlet 6 of the slow descent valve 66.
6b and the front lift cylinder 14, and when the pressure in this oil path 47 increases excessively, the valve is opened and the excess pressure is released to the oil sump 57. It has become. Therefore, the front lift cylinder 14
Even if the working machine that has been raised by the above is overloaded due to, for example, a collision with another object, the load can be alleviated.

As mentioned above, the front and rear switching block 3o is equipped with the first and second poppet valves 642, 64g, the camshaft 65, the gradual lowering valve 66, and the overload relief valve 67, so inspection and maintenance of these valves can be carried out before and after. This can be easily done by removing the switching block 30 from the distribution block 29. At that time, only relatively small diameter oil passages are opened at the separation surfaces of the distribution block 29 and the front/rear switching block 30, so there is extremely little risk of dust etc. entering. Since the relief valve 67 is provided in the front/rear switching block 30, the structure of the front lift cylinder 14 is simplified, and the front lift cylinder 14 is equipped with a single hydraulic hose 1.
11 is sufficient, and the piping structure is also simplified.

In FIG. 5, the cylinder head 73 of the rear lift cylinder 17 is provided with a gradual lowering valve 74 and an overload relief valve 75. The slow lowering valve 74 is used to slowly lower the rear lift cylinder 17, and the overload relief valve 75 is used when an overload is applied to the rear lift cylinder 17 and the pressure in its hydraulic chamber 70 increases excessively. At this time, the excess pressure is released to the oil sump 57. Their structures are basically the same as those of the slow descent valve 66 and overload relief valve 67, so a description of these structures will be omitted.

Referring again to FIG. 4, the horizontal control block 31 includes a switching valve 76, a first . Second solenoid valve 77, . 77□, 1st. Second orifice 78. ．． 7L and a relief valve 79.

The switching valve 76 consists of a spool 80, a return spring 81 that urges the spool 80 to a neutral position, and a housing 82 that houses them.The housing 82 has an inlet 83 in the center and a pair of outlets on both sides. 84. ．． 84□, and a pair of relief holes 85. on both sides of it. , 85□, and a pair of pressure receiving chambers 861.86z on both sides thereof. The inlet 83 communicates with the oil passage 42 of the distribution block 29 via the oil passage 51, and the outlet 841.84□ connects a pair of hydraulic hoses to the upper and lower oil chambers 26a, 26b (Fig. 8) of the telescopic cylinder 26. 87 and 87 respectively.

Further, the first relief port 851 is the first orifice 78. and the first pressure receiving chamber 86 via the oil passage 53, and the oil sump 57 via the first orifice 78 and the first solenoid valve 771.
I also communicate with you. The second relief port 85□ is the second orifice 78
．． and the second pressure receiving chamber 86 through the oil passage 54. It also communicates with the oil sump 57 via the second orifice 78□ and the second solenoid valve 77. Furthermore, both escape ports 851, 85
．． also communicates with the oil reservoir 57 via a relief valve 79.

1st. 2nd TM valve? ? , , 77□ are all of the normally open type.

When the inclination sensor (not shown) installed on the tractor 1 detects that the tractor 1 is descending to the right, the first solenoid valve IL is activated.
A valve closing signal is sent to the second electromagnetic valve 77□ when a downward movement to the left is detected.

When the first electromagnetic valve 77 closes, the pressure in the first pressure receiving chamber 861 of the switching valve 76 increases, causing the spool 80 to move to the right in the figure. When the spool 80 moves to the right, the first outlet 84 . is blocked from the first relief port 851 and communicates with the inlet 83, and the second outlet 84□ is blocked from the inlet 83 and communicated with the second relief port 852, so that the pressure sent from the dividing valve 36 to the inlet 83 is The oil is at the first outlet 84. The upper oil chamber 26 of the telescopic cylinder 26
supplied to a. On the other hand, the oil in the lower oil chamber 26b is discharged to the oil reservoir 57 through the second outlet 84□, the second relief port 85□, the second orifice 78□, and the second electromagnetic valve 77□. As a result, the telescopic cylinder 26 extends and causes the work implement 18 to rotate to the right (rotate) relative to the tractor l which is tilting to the left.

Also, when the second electric valve 77□ closes, the second electric current valve 77□ closes.
The pressure in the pressure receiving chamber 86□ rises, causing the spool 80 to move to the left in the figure. When the spool 80 moves to the left, the second outlet 84□ is cut off from the second relief port 85□, communicates with the inlet 83, and the first
Exit 84. is blocked from the inlet 83 and the first relief port 85. Therefore, the pressure oil sent from the flow dividing valve 36 to the inlet 83 passes through the second outlet 84□ and enters the lower oil chamber 2 of the telescopic cylinder 26.
6b, the oil in the upper oil chamber 26a is discharged to the oil reservoir 57 through the first outlet 841, the first relief port 853, the first orifice 781, and the first electromagnetic valve 77. As a result, the telescopic cylinder 26 contracts and causes the work implement 18 to tilt to the left relative to the tractor 1 which tilts to the right. In this way, the working machine 18 is always kept in a horizontal state.

When the work machine 18 becomes horizontal, both solenoid valves 7777□ return to the open state, and the first solenoid valve 7777□ returns to the open state. Second pressure receiving chamber 86. ．． 86.
Since the pressure of is released, the spool 80 returns to the spring 81
is held in a neutral position by In the neutral position of the spool 80, the inlet 83 is connected to both relief ports 85. ．． 85□, so these relief ports 85. , 85□ and both orifices 78. , 78□, the inlet 83
Pressure oil flowing into the upper and lower oil chambers 26 of the telescopic cylinder 26
Pressure is applied approximately equally to a and 26b. In this way, the telescopic cylinder 26 is fixed at its current length.

As shown in FIG. 8, the outer surface of the horizontal control block 31 has the first. Second exit 84. 842 respectively. Second hose connection pipes 893, 89□ are attached. On the other hand, on the outer surface of the telescoping cylinder 26, there is a first cylinder connected to the upper oil chamber 26a and the lower oil chamber 261), respectively. Second hose connection pipe 90, . 90□ is attached. and the first hose connection pipe 89. ．． 90. The one hydraulic hose 87 is connected to the same dirt floor, and the second hose connection pipe 892.90
Both ends of the other hydraulic hose 87 are connected to □.

The pair of hoses 87, 87 are formed to have approximately the same length and are tied together by a coil member 91 with a fixed distance shifted from each other in the hair direction. Correspondingly, in the horizontal control block 31, the distal end of the first hose connecting pipe 891 is made to protrude from the distal end of the second hose connecting pipe 892 by the above distance, and on the contrary, in the telescopic cylinder 26, the distal end of the first hose connecting pipe 891 is made to protrude by the above distance.
Hose connection pipe 90. Connect the tip of the second hose connection pipe 90. The tip is set back by the distance I.

Therefore, when piping, both hydraulic hoses 87.87
and the first and second hose connection pipes 89 of the horizontal control block 31. ．． 89 □ and the same thing that is close to each other” = is connected,
Also, the other ends of both hydraulic hoses 87 and 87 and the telescopic cylinder 26
1st. Second hose connection pipe 90. ．． 90! If you connect two parts that are close to each other, the first hose connection pipe 8 will inevitably be connected to the first hose connection pipe 8.
91.89□ and the second hose connection pipe 90. ．． 90
□ will be connected to each other, for example, the first hose connection pipe 89. It is possible to prevent erroneous connections such as connecting the second hose connection pipe 90□. That is, both hydraulic hoses 87
．． Not only the direction of 87, but also the first direction of famous hose 87. Second
Connecting pipe 89. ．． 90. Since there is no need to equally consider compatibility with 89□ and 902, piping work can be performed accurately and quickly.

Referring again to FIG. 4, the hydraulic outlet bronck 34 is connected to the first and second hose connection ports 92. ．． 92□, and an oil passage 93.94 which communicates with the oil passage 40.41 which opens these hose connection ports 921. The conch 95 is arranged so as to.

The cock 95 opens the oil passage 9 in its open position 0 (see Fig. 7).
3 and 94, and a groove 98 that short-circuits both oil passages 93 and 94 at the closed position IC (see FIG. 7).

First hose connection port 92. A high-pressure hose 100 connected to the high-pressure part of the external hydraulic loader 99 is connected to the second hose connection port 92 □, and a low-pressure hose 101 connected to the same low-pressure part is connected to the second hose connection port 92 □.

When the conc 95 is opened and rotated to position 0 in order to operate the external hydraulic loader 99, the pressure oil sent from the hydraulic pump 5G is supplied to the external hydraulic loader 99 through the oil passages 40, 93 and the high pressure hose. The pressurized oil that has been operated is sent to the diversion valve 36 through the low pressure hose 101 and oil passages 94 and 41. When the external hydraulic loader 99 is in operation, the front and rear lift cylinders 14 and 17 are normally inactive, so the pressure oil that has exited the second outlet 36c of the diverter valve 3G is released when the unload valve 37 is opened. When the conch 95 is rotated to the closing position C to stop the operation of the external hydraulic loader 99 that returns the flow to the oil sump 57, the oil passages 93 and 94 are short-circuited, and pressure oil is supplied from the external hydraulic port to the da 99. will be stopped. Then, oil passage 9
3, 94, the front and rear lift cylinders 14.
It becomes possible to supply pressure oil to 17.

As shown in FIGS. 6 and 7, the hydraulic extraction block 34
is formed flat so that it can be placed in a small space between the distribution flock 29 and the sheet 7, and the conc 9
5 is arranged horizontally, and hose connection ports 92+, 9
22 are provided on both left and right side surfaces of the hydraulic pressure extraction block 34 so that the high and low pressure hoses too and iot are not interfered with by the seat 7.

An operating lever 102 is pivotally supported 103 at the end of the row of cocks 95. This operating lever 102 can be rotated between a storage position where it falls coaxially with the cock 95 and a use position where it stands up at right angles to the cock 95. A torsion coil spring 104 is attached to bias the torsion coil spring 104 in the opposite direction. Incidentally, reference numeral 105 is a retaining plate that prevents the concrete 95 from being pulled out from the hydraulic pressure extraction block 34.

Therefore, when operating the cock 95, first rotate the seat 7 forward about the pivot 9 (the state shown by the chain line in FIG. 1).
, by opening the -F side of the oil pressure extraction block 34 and then raising the operating lever 102 to the operating state, the cock 95 can be opened via the operating lever 102 without being obstructed by the seat 7 and can be moved to the 0 or closed position. It can be easily rotated to 2c.

After operation, if you release your hand from the operating lever 102, the spring 104
The operating lever 102 immediately returns to the retracted position with the force of
Even when the sheet 7 is set in a fixed position, interference with the sheet 7 is avoided.

In addition, in blocks 29, 30, and 31 of Fig. 4, the oil sump 5
All oil passages shown as being open to 7 actually pass through distribution block 29 .

FIG. 9 shows an example in which the front lift cylinder 14 and the external hydraulic loader 99 are not provided. In this case, the first cover plate 105 is connected to the rear R of the distribution block 29 in place of the front/rear switching block 30, and the first cover plate 105 is connected to the upper surface T of the distribution block 29 in place of the oil pressure extraction block 34 with bolts. be done. The first cover plate 105 has oil passages 44 and 45.
Since the communication passage 107 is provided between the rear lift cylinders 17 and 17, the rear lift cylinder 17 can be caused to rise and fall by controlling the rise control valve 32 and the fall control valve 33 as described above. Further, the second cover plate 106 has oil passages 40 and 4.
Since the communication path 108 is provided to connect the two parts, pressure oil can be supplied to the flow dividing valve 36 without any problem.

According to the present invention, a distribution block having a first oil passage connected to a hydraulic pressure source is installed in the vicinity of the rear lift cylinder, and this distribution block has a first oil passage connected to the rear lift cylinder. Two oil passages are provided, and the front/rear switching block connected to the distribution block has a third oil passage connected to a hydraulic hose connecting the block and the front lift cylinder, and a third oil passage that connects the first oil passage to a second oil passage or A front and rear switching valve that selectively communicates with the third oil passage, a slow descent valve that is connected to the third oil passage, and an overload relief valve that is also connected to the third oil passage are provided, so the front and rear lift It is enough to connect one hydraulic hose to the cylinder.
In addition to simplifying the piping structure, it is also possible to simplify the structure of the front lift cylinder.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; Fig. 1 is a side view of a riding tractor, Fig. 2 is a rear perspective view of the same tractor with a working machine connected to the rear, and Fig. 3 is a hydraulic control of the same tractor. A perspective view of the device, Fig. 4 is a hydraulic circuit diagram of the same 1-actor, Fig. 5 is a vertical sectional side view of the main part of the rear hydraulic cylinder in the 1-actor, and Fig. 6 is a cross-sectional view of the hydraulic pressure take-off block of the hydraulic control device. A plan view, FIG. 7 is a view in the direction of the ■ arrow in FIG. 6, FIG. 8 is a piping diagram between the horizontal control block of the hydraulic control device and the telescopic cylinder for horizontal control of the working machine, and FIG. It is a hydraulic circuit diagram when a front/rear switching block and a hydraulic pressure extraction block are removed from the control device. l... Passenger tractor, 14... Front lift cylinder, 17... Rear lift cylinder, 29... Distribution block, 30... Front/rear switching block, 44... First oil passage, 45... ...Second oilway, 47...Third oilway, 56.
...Hydraulic pump as a hydraulic source, 64. ．． 642.65
...The first boven F-valve, the second which constitutes the front and rear cut-off IQ valve.
Bopent valve and camshaft, 66... slow descent valve, 67...
・Overload relief month (Figure 2)

Claims (1)

[Claims] A front lift cylinder that raises and lowers a working machine connected to the front end of the vehicle body, a rear lift cylinder that raises and lowers a working machine that is connected to the rear end of the vehicle body, a hydraulic power source, and a hydraulic power source that connects the hydraulic power source to the front lift cylinder or the rear lift cylinder. A front/rear switching valve selectively connects a hydraulic source to these lift cylinders to supply pressurized oil to provide upward movement, and a forward/backward switching valve that regulates the rate of oil discharge from the front lift cylinder during downward movement. A hydraulic system for a passenger tractor, comprising a lowering valve and an overload relief valve that releases excess hydraulic pressure when the hydraulic pressure in the front lift cylinder increases excessively,
A distribution block having a first oil passage connected to a hydraulic power source is installed near the rear lift cylinder, and this distribution block includes:
A second oil passage connected to the rear lift cylinder is provided, and a third oil passage connected to the hydraulic hose connecting between the block and the front lift cylinder is provided in the front/rear switching block joined to the distribution block.
an oil passage, a front-rear switching valve that selectively communicates the first oil passage with the second oil passage or the third oil passage, a slow descent valve connected to the third oil passage, and a slow descent valve that is also connected to the third oil passage. A hydraulic system for a riding tractor, characterized in that it is provided with an overload relief valve.