JP4166175B2 - Hydraulic circuit structure of work vehicle - Google Patents

Description

  The present invention relates to a hydraulic circuit structure in a work vehicle such as a backhoe or a wheel loader.

Some backhoes, which are examples of work vehicles, have a hydraulic circuit structure as disclosed in Patent Document 1, for example. In Patent Document 1, a control valve (V5, V6, V7, V8 in FIGS. 2 and 3 of Patent Document 1) for supplying hydraulic oil to a backhoe device (corresponding to a working device), hydraulic oil is supplied to a traveling device, and the like. A control valve (V1, V2, V3, V4 in FIGS. 2 and 3 of Patent Document 1) is provided. A variable displacement hydraulic pump (Pa in Fig. 2 and Fig. 3 in Patent Document 1) that supplies hydraulic oil to the control valve of the backhoe device is provided, and is based on the maximum work load among the work loads applied to the backhoe device. In addition, load sensing means for changing the discharge flow rate of the hydraulic pump is provided.
In this case, in Patent Document 1, the control valve for the backhoe device (V5, V6, V7, V8 in FIG. 2 and FIG. 3 in Patent Document 1) and the control valve for the traveling device (FIGS. 2 and 3 in Patent Document 1). V1, V2, V3, V4) are connected in a line to form a straight unit.

JP 2001-355257 A (FIGS. 2 and 3)

  When a control valve provided with load sensing means and a control valve not provided with load sensing means are provided as in Patent Document 1, if these control valves are configured in a straight unit, Depending on the arrangement of members, devices, etc., a straight unit may be arranged only in a fixed direction (for example, a straight unit may be arranged only in a horizontal direction), so there is room for improvement.

  For example, when connecting a pipe from a hydraulic pump to a straight unit, the pipe from the hydraulic pump is connected to a predetermined part of the straight unit, and an external pipe is connected from this predetermined part to another part of the straight unit. Since they may be connected, there is room for improvement in terms of simplifying the structure and reducing production costs.

  In the hydraulic circuit structure of a work vehicle, when a control valve provided with load sensing means and a control valve not provided with load sensing means are provided, the control valve can be easily arranged. The purpose is to simplify the structure and reduce production costs.

[I]
(Constitution)
The first feature of the present invention resides in the following configuration in the hydraulic circuit structure of a work vehicle.
Same as the first control valve unit in which a plurality of control valves are arranged in a row, the second control valve unit in which a plurality of control valves are arranged in a row, and the first and second control valve units arranged in a row A base unit connected across the end of the side. A variable displacement hydraulic pump that supplies hydraulic oil to the control valve of the first control valve unit is provided, and the hydraulic oil of the control valve of the first control valve unit is supplied to the working device provided in the machine body. Load sensing means is provided for changing the discharge flow rate of the hydraulic pump based on the maximum work load of the work loads applied to the work device.

(Function)
According to the first feature of the present invention, the first and second control valve units and the base unit are configured as one unit, but the first and second control valve units and the base unit are, for example, U-shaped, A unit that is bent like a J-shape.
As a result, the first characteristic unit (first and second control valve units, base unit) of the present invention is not so long as compared to the straight line unit of Patent Document 1, so that other members and devices are used. The first feature of the present invention is relatively easy without being restricted, since it is unlikely that a unit (first and second control valve unit, base unit) can be arranged only in a fixed direction due to the arrangement of These units (first and second control valve units, base unit) can be arranged.

  According to the first feature of the present invention, since the base unit is positioned between the first and second control valve units, for example, if a pipe from a hydraulic pump is connected to the base unit, the oil inside the base unit An internal oil passage can be arranged in parallel from the base unit to the first and second control valve units so that the hydraulic oil of the hydraulic pump is supplied to the first and second control valve units via the passage. Therefore, it is less likely that many external pipes are connected across the first and second control valve units.

  According to the first aspect of the present invention, in the case where the load sensing means for changing the discharge flow rate of the hydraulic pump is provided based on the maximum work load of the work loads applied to the work device, the control valve provided with the load sensing means In the control valve not provided with the load sensing means, the control valves provided with the load sensing means are grouped as a first control valve unit. Thus, according to the first feature of the present invention, the base unit is located between the first and second control valve units, so that the first control valve unit (the control valve provided with the load sensing means) The unit is separated from the second control valve unit (the control valve not provided with the load sensing means), and an oil passage for the load sensing means is provided in the first control valve unit. it can.

(The invention's effect)
According to the first aspect of the present invention, in a hydraulic circuit structure of a work vehicle, when a control valve provided with load sensing means and a control valve not provided with load sensing means are provided, it is relatively easy without restriction. The units (first and second control valve units, base unit) can be arranged in the unit, and the flexibility of the units (first and second control valve units, base unit) can be improved.

  According to the first aspect of the present invention, an internal oil passage can be arranged in parallel from the base unit to the first and second control valve units, and a large number of external passages can be provided across the first and second control valve units. Since it is less likely to connect the pipes, the structure of the units (first and second control valve units, base unit) can be simplified.

  According to the first feature of the present invention, the control valve provided with the load sensing means can be integrated as a first control valve unit, and an oil passage for the load sensing means can be provided in the first control valve unit. Thus, the structure of the unit (first and second control valve units, base unit) can be simplified.

[II]
(Constitution)
The second feature of the present invention resides in the following configuration in the hydraulic circuit structure of the work vehicle of the first feature of the present invention.
A working device is provided in the front part of the machine body, and the first control valve unit is arranged so as to be positioned on the front part side of the machine body relative to the second control valve unit.

(Function)
According to the second feature of the present invention, the “action” described in the preceding item [I] is provided in the same manner as the first feature of the present invention, and in addition to this, the following “action” is provided.
When the load sensing means for changing the discharge flow rate of the hydraulic pump is provided based on the maximum work load of the work loads applied to the work device, according to the second feature of the present invention, the control valve provided with the load sensing means includes: The first control valve unit is arranged as a first control valve unit, and the first control valve unit is arranged closer to the front side (working device side) of the machine body than the second control valve unit.
Thus, according to the second feature of the present invention, the piping from the first control valve unit to the working device can be shortened. The piping from the first control valve unit to the working device and the second control valve The piping from the unit is less likely to interfere with each other.

(The invention's effect)
According to the second feature of the present invention, the “effect of the invention” described in the preceding item [I] is provided in the same manner as the first feature of the present invention. In addition, the following “effect of the invention” is provided. ing.
According to the second feature of the present invention, the piping from the first control valve unit to the working device can be shortened, and the piping from the first control valve unit to the working device and the second control valve unit Since the pipes hardly interfere with each other, the arrangement of the units (first and second control valve units, base unit) is advantageous in terms of simplification of the structure.

[1]
FIG. 1 shows an entire side surface of a backhoe as an example of a work vehicle. A swivel base 2 is supported by rubber crawler type right and left traveling devices 1, and a vertical axis P1 around a front portion of the swivel base 2 A support bracket 7 is swingably supported, and a double-acting fourth hydraulic cylinder 14 that drives the support bracket 7 to the right and left is provided. The backhoe device 3 (corresponding to a working device) is provided on the support bracket 7. Is provided.

  As shown in FIG. 1, the backhoe device 3 includes a boom 4 that is driven up and down by a double-acting first hydraulic cylinder 11, an arm 5 that is driven back and forth by a double-acting second hydraulic cylinder 12, The bucket 6 is configured to be driven back and forth by a dynamic third hydraulic cylinder 13. A dozer 8 is provided between the right and left traveling apparatuses 1, and a double-acting fifth hydraulic cylinder 15 that drives the dozer 8 up and down is provided. A driver's seat 16 is provided at the rear of the swivel base 2, an engine 36 is provided below the driver's seat 16, and a control tower 17 is provided at the front of the swivel base 2. Leveres 9 and 10, right and left traveling levers 19 are provided, and an operation pedal 20 is provided below the control tower 17.

[2]
Next, the first control valve unit 91, the second control valve unit 92, the spacer unit 93 (corresponding to the base unit), and the inlet unit 94 (corresponding to the base unit) will be described.
2 and 3, the first control valve 21 of the first hydraulic cylinder 11, the second control valve 22 of the second hydraulic cylinder 12, the third control valve 23 of the third hydraulic cylinder 13, and the fourth hydraulic cylinder. 14, the fifth control valve 25, the ninth control valve 29 of the service port 39, and pressure compensation valves 61, 62, 63, 65, 69, which will be described later, and a shuttle valve 79.

  2 and 3, the first control valve 21, the pressure compensation valve 61, and the shuttle valve 79 are configured as one block, and the second control valve 22, the pressure compensation valve 62, and the shuttle valve 79 are integrated. The third control valve 23, the pressure compensation valve 63, and the shuttle valve 79 are configured in one block. The fifth control valve 25, the pressure compensation valve 65, and the shuttle valve 79 are configured as one block, and the ninth control valve 29 and the pressure compensation valve 69 are configured as one block. These five blocks are connected in a line to form a first control valve unit 91.

  As shown in FIGS. 2 and 3, the switching valve 40, the fourth control valve 24 of the turning motor 18 that drives the turntable 2 to turn, the sixth control valve 26 of the right traveling device 1, and the first control valve 26 of the left traveling device 1. 7 control valve 27 and the eighth control valve 28 of the fifth hydraulic cylinder 15 are provided. Each of the switching valve 40, the fourth control valve 24, the sixth control valve 26, the seventh control valve 27, and the eighth control valve 28 is configured as one block, and these five blocks are connected in a line. Thus, the second control valve unit 92 is configured.

  As shown in FIGS. 2 and 3, a block-like spacer unit 93 is provided, and a block-like inlet unit 94 including a merging valve 54 described later is provided, and the spacer unit 93 and the inlet unit 94 are connected to each other. Has been. The first and second control valve units 91 and 92 are arranged side by side, the end of the first control valve unit 91 on the second control valve 22 side, and the end of the second control valve unit 92 on the sixth control valve 26 side, The spacer unit 93 and the inlet unit 94 are connected to each other, and the first and second control valve units 91 and 92, the spacer unit 93, and the inlet unit 94 are integrally formed in a U shape (J shape). Has been. In this case, the second control valve unit 92 is shorter than the first control valve unit 91.

  As shown in FIG. 1, a right bonnet 58 is provided on the right side of the driver's seat 16 in the swivel base 2, and first and second control valve units 91 and 92, a spacer unit 93, An inlet unit 94 is disposed. The first and second control valve units 91 and 92 are located on the upper side, the spacer unit 93 and the inlet unit 94 are located on the lower side, and the first control valve unit 91 and the spacer unit 93 are located on the front side (backhoe device). 3 side). In this case, since the second control valve unit 92 is shorter than the first control valve unit 91, the second control valve unit 92 is lower than the first control valve unit 91.

[3]
Next, the hydraulic circuit structure of the first control valve unit 91, the second control valve unit 92, the spacer unit 93, and the inlet unit 94 will be described.
As shown in FIG. 2, a variable displacement first hydraulic pump 41 driven by an engine 36, a variable displacement second hydraulic pump 42, a third hydraulic pump 43 and a pilot pump 44 are provided.

  As shown in FIGS. 2 and 3, the oil passages 30 and 35 from the first and second hydraulic pumps 41 and 42 are connected to the inlet unit 94 and connected to the junction valve 54. In the inlet unit 94, the oil passages 37 and 38 from the merging valve 54 are joined, and the oil passages 37 and 38 are connected to the oil passage 46 of the spacer unit 93. The oil passage 47 passes through five blocks of the first control valve unit 91 and is connected to the oil passage 46, and the first, second, third, fifth and ninth control valves 21, 22, 23, 25, 29 are oil. It is connected to the path 47. The oil passage 48 passes through the five blocks of the first control valve unit 91 and the spacer unit 93 and is connected to the hydraulic oil tank 45. In the spacer unit 93, the oil passage 46 is connected to the oil passage 48 via the relief valve 57. It is connected.

  As shown in FIG. 3, the first, second and third control valves 21, 22 and 23 are pilot operated by pilot pressure, and are configured as a center bypass type neutral return type. The fifth control valve 25 is a machine-operated type that is operated by the operation pedal 20 (see FIG. 1), and is configured as a center bypass type neutral return type. The ninth control valve 29 is a mechanically operated type operated by an operating lever (not shown), and is configured as a center bypass type neutral return type.

  As shown in FIG. 3, in the inlet unit 94, oil passages 49, 50 are extended from the junction valve 54, and the oil passage 49 passes through the block of the sixth control valve 26 of the second control valve unit 92 and enters the sixth. The oil passage 50 is connected to the seventh control valve 27 through the blocks of the sixth and seventh control valves 26 and 27 of the second control valve unit 92. The sixth and seventh control valves 26 and 27 are mechanically operated by the travel lever 19 (see FIG. 1) and are configured as a center bypass type neutral return type. The oil passage 51 passes through the five blocks of the second control valve unit 92 and the inlet unit 94, and the oil passage 52 is connected across the oil passages 48 and 51 in the spacer unit 93. The sixth and seventh control valves 26, 27 are connected to the oil passage 51, and the oil passages 49, 50 are connected to the oil passage 51 via the relief valve 59 in the inlet unit 94.

  As shown in FIGS. 2 and 3, the oil passage 53 from the third hydraulic pump 43 is connected to the switching valve 40 block of the second control valve unit 92 and is connected to the switching valve 40. In the block of the switching valve 40 of the valve unit 92, the oil passage 53 is connected to the oil passage 51 via a relief valve 64. Oil passages 55 and 56 extending from the oil passage 53 pass through the blocks of the fourth and eighth control valves 24 and 28 of the second control valve unit 92 and are connected to the fourth and eighth control valves 24 and 28. Has been. The fourth control valve 24 is a pilot operated type using a pilot pressure and is configured as a center return type neutral return type, and the fifth control valve 28 is a machine operated type operated by an operating lever (not shown). Bypass type neutral return type.

  As shown in FIG. 3, the center bypass oil passage 66 of the fourth and eighth control valves 24, 28 blocks the switching valve 40, the fourth and eighth control valves 24, 28 of the second control valve unit 92. It penetrates and is connected to the switching valve 40. In the block of the switching valve 40 of the second control valve unit 92, the oil passage 67 from the switching valve 40 is connected to the oil passage 51, and from the switching valve 40 to the outside of the block of the switching valve 40 of the second control valve unit 92. The external oil passage 68 is extended, and the external oil passage 68 is connected to the spacer unit 93 and connected to the oil passage 46.

[4]
Next, the switching valve 40 and the junction valve 54 will be described.
As shown in FIG. 3, the merging valve 54 connects the oil passages 30, 35 to the oil passages 37, 38 and blocks the oil passages 49, 50, and connects the oil passage 30 to the oil passage 49. The oil passage 35 is connected to the oil passage 50 and is configured to be operated at a second position 54b where the oil passages 37 and 38 are blocked, and is biased to the first position 54a by a spring. As shown in FIGS. 2 and 3, the pilot oil passage 70 is branched from the oil passage 85 from the pilot pump 44, and the pilot oil passages 75 and 77 branched from the pilot oil passage 70 are connected to the second control valve unit 92. It is connected to the block of the switching valve 40 and the inlet unit 94.

  As shown in FIGS. 2 and 3, the pilot oil passage 77 is connected to the merging valve 54, and the pressure sensor 84 is connected to the pilot oil passage 77. A pilot oil passage 78 branched from the pilot oil passage 77 in the inlet unit 94 passes through the blocks of the sixth and seventh control valves 26 and 27 of the second control valve unit 92, and the sixth and seventh control valves 26 and 27. The pilot oil passage 78 is connected to the oil passages 51 and 52 in the inlet unit 94.

  As shown in FIG. 3, the switching valve 40 connects the oil passage 66 to the oil passage 67 and connects the oil passage 53 to the first position 40 a and the oil passages 53 and 66 to connect to the external oil passage 68. Thus, the oil passage 67 is configured to be freely operated at the second position 40b, and is urged to the first position 40a by a spring. The pilot oil passage 80 branched from the pilot oil passage 75 in the block of the switching valve 40 of the second control valve unit 92 is connected to the switching valve 40, and the pilot oil passage in the block of the switching valve 40 of the second control valve unit 92. A pilot oil passage 83 branched from 80 is connected to a pilot oil passage 77 through the blocks of the sixth and seventh control valves 26 and 27 of the second control valve unit 92 and the inlet unit 94.

  As shown in FIG. 3, the pilot oil passage 95 branched from the pilot oil passage 77 in the inlet unit 94 is the first, second, third, fifth, and ninth control valves 21 and 22 of the spacer unit 93 and the first control valve unit 91. , 23, 25, 29 passes through the first, second, third, fifth and ninth control valves 21, 22, 23, 25, 29, and the pilot oil passage 95 is connected to the oil passage 48. ing.

  The state shown in FIG. 3 is a state in which the sixth and seventh control valves 26, 27 are operated to the neutral position (the stopped state of the right and left traveling devices 1), and the pilot oil passages 77, 78, 80, 83 are shown. 95, the pilot pressure is reduced, the merging valve 54 is operated to the first position 54a, and the switching valve 40 is operated to the first position 40a. In the state shown in FIGS. 2 and 3, the hydraulic oil of the first and second pumps 41, 42 passes through the oil passages 30, 35, the first position 54 a of the merging valve 54, and the oil passages 37, 38, 46, 47. The first, second, third, fifth and ninth control valves 21, 22, 23, 25 and 29 are supplied. The hydraulic oil of the third hydraulic pump 43 is supplied to the fourth and eighth control valves 24 and 28 via the oil passages 53, 55 and 56.

  When the sixth or seventh control valve 26, 27 is operated to the travel position from the state shown in FIG. 3 (the operating state of the right or left travel device 1), the pilot is operated by the sixth or seventh control valve 26, 27. The oil passage 78 is shut off, the pilot pressure in the pilot oil passages 77 and 78 increases, and the merging valve 54 is operated to the second position 54b. As a result, the hydraulic oil of the first and second pumps 41 and 42 flows through the oil passages 30 and 35, the second position 54 b of the merging valve 54, and the oil passages 49 and 50, the sixth and seventh control valves 26, 27. In this case, an increase in pilot pressure in the pilot oil passages 77 and 78 is detected by the pressure sensor 84, and a buzzer (not shown) is activated.

  As described above, the sixth or seventh control valve 26, 27 is operated to the traveling position (the operating state of the right or left traveling device 1) (the state where the merging valve 54 is operated to the second position 54b). When any one of the first, second, third, fifth and ninth control valves 21, 22, 23, 25 and 29 is operated from the neutral position, the first, second, third, fifth and ninth control valves 21 and 22 are controlled. , 23, 25, 29, the pilot oil passage 95 is shut off, the pilot pressure in the pilot oil passages 80, 83, 95 increases, and the switching valve 40 is operated to the second position 40b. Thereby, in addition to the hydraulic oil of the third hydraulic pump 43 being supplied to the fourth and eighth control valves 24 and 28 via the oil passages 53, 55 and 56, the hydraulic oil of the third hydraulic pump 43 is Are supplied to the oil passage 46 through the oil passages 53 and 66, the second position 40b of the switching valve 40 and the external oil passage 68, and the first, second, third, fifth and ninth control valves 21, 22, 23 and 25 are supplied. , 29.

[5]
Next, operation of the backhoe device 3 and the swivel base 2 by the right and left operation levers 9 and 10 will be described.
As shown in FIG. 5, the right operating lever 9 is configured to be freely movable in the front / rear and left / right directions. The pilot valve 31 generates pilot pressure by the front and rear operations of the right operating lever 9 and the right and left of the right operating lever 9. A pilot valve 33 that generates a pilot pressure by operation is provided. Similarly, the left operating lever 10 is configured to be freely movable in the front / rear and left / right directions. A generating pilot valve 34 is provided.

  As shown in FIGS. 2 and 5, the pilot pressure of the pilot pump 44 is supplied to the pilot valves 31 to 34 via the oil passage 85. The pilot valve 31 and the first control valve 21 are connected via a pilot oil passage, and the pilot valve 33 and the third control valve 23 are connected via a pilot oil passage. The pilot valve 32 and the second control valve 22 are connected via a pilot oil passage, and the pilot valve 34 and the fourth control valve 24 are connected via a pilot oil passage.

  As shown in FIGS. 3 and 5, when the right operation lever 9 is operated backward, the first control valve 21 is operated to the raised position 21a by the pilot pressure of the pilot valve 31, and the first hydraulic cylinder 11 is extended to operate the boom. 4 is driven upward. When the right operating lever 9 is pre-operated, the first control valve 21 is operated to the lowered position 21b by the pilot pressure of the pilot valve 31, the first hydraulic cylinder 11 is contracted, and the boom 4 is driven downward.

  As shown in FIGS. 3 and 5, when the right operating lever 9 is operated to the right, the third control valve 23 is operated to the earth discharging position by the pilot pressure of the pilot valve 33, and the third hydraulic cylinder 13 is contracted to operate the bucket. 6 is driven to the soil removal side. When the right operation lever 9 is operated to the left, the third control valve 23 is operated to the scraping position by the pilot pressure of the pilot valve 33, the third hydraulic cylinder 13 is extended, and the bucket 6 is driven to the scraping side.

  As shown in FIGS. 3 and 5, when the left operation lever 10 is operated backward, the second control valve 22 is operated to the lowered position by the pilot pressure of the pilot valve 32, and the second hydraulic cylinder 12 is extended to operate the arm 5. Is driven downward. When the left operating lever 10 is pre-operated, the second control valve 22 is operated to the ascending position by the pilot pressure of the pilot valve 32, the second hydraulic cylinder 12 is contracted and the arm 5 is driven to the ascending side.

  As shown in FIGS. 3 and 5, when the left operating lever 10 is operated to the right, the fourth control valve 24 is operated to the right turning position by the pilot pressure of the pilot valve 34, and the turning table 2 is turned to the right by the turning motor 18. Driven to the rotation side. When the left operating lever 10 is operated to the left, the fourth control valve 24 is operated to the left turning position by the pilot pressure of the pilot valve 34, and the turning table 2 is driven to the left turning side by the turning motor 18.

  As shown in FIGS. 3 and 5, the pilot pressures of the pilot valves 31 to 34 are configured to increase as the right and left operation levers 9 and 10 are largely operated from the neutral position. Accordingly, as the right and left operation levers 9 and 10 are operated more greatly from the neutral position, the pilot pressures of the pilot valves 31 to 34 increase corresponding to the operation positions of the right and left operation levers 9 and 10. The fourth control valves 21 to 24 are operated to the large flow rate side, and the first, second, and third hydraulic cylinders 11, 12, and 13 and the swivel are increased as the right and left operation levers 9 and 10 are operated more greatly from the neutral position. The motor 18 operates at high speed.

[6]
Next, the first control valve 21 and the second, third, fifth, and ninth control valves 22, 23, 25, and 29 will be described.
As shown in FIGS. 3 and 4, oil passages 86 and 87 are connected across the first hydraulic cylinder 11 and the first control valve 21, and an oil passage 88 across the oil passage 48 and the first control valve 21. Is connected. A pressure compensation valve 61 is provided on the lower side of the first control valve 21, an oil passage 89 from the first control valve 21 is connected to the pressure compensation valve 61, and an oil passage 90 from the pressure compensation valve 61 is the first. Connected to the control valve 21.

  As shown in FIG. 4, when the first control valve 21 is operated to the neutral position 21c, the oil passages 86, 87 are shut off, and the oil passage 48, the oil passages 88, 89, 90, and the pressure compensation valve 61 are connected. Communicate. When the first control valve 21 is operated to the raised position 21a, the hydraulic oil in the oil passage 47 is moved to the raised position 21a, the oil passage 89, the pressure compensation valve 61, the oil passage 90, and the first control valve 21 of the first control valve 21. Of the first hydraulic cylinder 11 and the hydraulic oil in the lower oil chamber of the first hydraulic cylinder 11 is supplied to the oil passage 87 and the first control valve 21. Is returned to the oil passage 48 through the oil passage 88, the first hydraulic cylinder 11 is extended, and the boom 4 is driven upward.

As shown in FIG. 4, when the first control valve 21 is operated to the lowered position 21b, the hydraulic oil in the oil passage 47 is moved to the lowered position 21b, the oil passage 89, the pressure compensation valve 61, the oil passage of the first control valve 21. 90, the lowering position 21b of the first control valve 21 and the oil passage 87 are supplied to the lower oil chamber of the first hydraulic cylinder 11, and the hydraulic oil in the upper oil chamber of the first hydraulic cylinder 11 is supplied to the oil passage. 86, the first control valve 21 is returned to the oil passage 48 via the lowered position 21b and the oil passage 88, and the first hydraulic cylinder 11 is contracted to drive the boom 4 downward.
As shown in FIG. 3, pressure compensating valves 62, 63, 65, and 69 are provided on the lower side of the second, third, fifth, and ninth control valves 22, 23, 25, and 29, and the first control valve shown in FIG. The second, third, fifth, and ninth control valves 22, 23, 25, and 29 have the same configuration as the control valve 21.

[7]
Next, an after orifice type load sensing means will be described.
As shown in FIGS. 3 and 4, pressure compensating valves 61, 62, 63, 65, 69 are provided on the lower side of the first, second, third, fifth, ninth control valves 21, 22, 23, 25, 29. Therefore, the pressure on the upper side of the first, second, third, fifth and ninth control valves 21, 22, 23, 25, 29 (pressure in the oil passage 47) and the pressure compensating valves 61, 62, 63, 65 69, the difference from the pressure on the lower side (pressure in the oil passage 90) is maintained at a predetermined differential pressure.

  As shown in FIG. 2, a flow compensation cylinder 60 for changing the discharge flow rates of the first and second hydraulic pumps 41 and 42 and a pilot operated flow compensation valve 71 are provided. The pilot pressure in the oil passage 30 is configured to be supplied to the flow compensation cylinder 60 via the pilot oil passage 72, the flow compensation valve 71, and the pilot oil passage 73, and the pilot pressure in the oil passage 30 passes through the pilot oil passage 74. Thus, the pilot pressure in the pilot oil passage 73 is discharged through the flow compensation valve 71 and the pilot oil passage 76.

  As shown in FIGS. 2 and 3, the pilot oil passage 97 branched from the oil passage 47 in the spacer unit 93 passes through the inlet unit 94 and is connected to the flow compensation valve 71, so that the pilot pressure in the oil passage 47 is the first. The discharge pressure PPS of the first and second hydraulic pumps 41 and 42 is applied to the flow compensation valve 71. In the first, second, third, fifth and ninth control valves 21, 22, 23, 25, 29, the pressure on the lower side of the pressure compensating valves 61, 62, 63, 65, 69 (pressure in the oil passage 90) The pilot pressure is taken out through the oil passage 96 and the shuttle valve 79, and the highest pilot pressure on the lower side of the pressure compensation valves 61, 62, 63, 65, 69 is supplied to the maximum control signal through the pilot oil passage 80. A pressure PLS is applied to the flow compensation valve 71. The pilot oil passage 80 is branched from the pilot oil passage 96 in the spacer unit 93 and passes through the inlet unit 94 and is connected to the flow rate compensation valve 71.

  As a result, as shown in FIG. 2, the flow rate compensation valve is maintained so that the difference between the discharge pressure PPS of the first and second hydraulic pumps 41 and 42 and the maximum control signal pressure PLS is maintained at the set control differential pressure. 71 and the flow rate compensation cylinder 60 change the discharge flow rates of the first and second hydraulic pumps 41 and 42. The after orifice type load sensing means is configured as described above.

  As shown in FIG. 2, the aforementioned control differential pressure is set by a spring 81 and a differential pressure cylinder 82 provided in the flow rate compensation valve 71. As a result, when the rotational speed of the engine 36 is increased and the discharge flow rate of the pilot pump 44 is increased, the control differential pressure is increased by the differential pressure cylinder 82 and the discharge flow rates of the first and second hydraulic pumps 41 and 42 are increased. Is changed to the increasing side. On the contrary, when the rotational speed of the engine 36 is reduced and the discharge flow rate of the pilot pump 44 is reduced, the control differential pressure is reduced by the differential pressure cylinder 82 and the discharge flow rates of the first and second hydraulic pumps 41 and 42 are reduced. Changed to decrease.

[8]
Next, the auto idle means will be described.
As shown in FIG. 3, the pilot oil passage 98 branched from the pilot oil passage 75 in the block of the switching valve 40 of the second control valve unit 92 is connected to the switching valve 40, the fourth, sixth, seventh of the second control valve unit 92. 8, 8 control valves 24, 26, 27, 28, through the inlet unit 94 and through the fourth, sixth, seventh, eighth control valves 24, 26, 27, 28, and the pilot oil passage 98 is oil Connected to paths 51 and 52. A pressure sensor 99 is connected to the pilot oil passages 95 and 98.

  Accordingly, when the sixth or seventh control valve 26, 27 is operated to the traveling position, or when the fourth or eighth control valve 24, 28 is operated from the neutral position, the fourth, sixth, seventh, eighth control is performed. The pilot oil passage 98 is blocked by the valves 24, 26, 27, and 28, and the pilot pressure in the pilot oil passage 98 increases. When any one of the first, second, third, fifth and ninth control valves 21, 22, 23, 25 and 29 is operated from the neutral position, the first, second, third, fifth and ninth control valves 21, 22, and 23 are operated. , 25, 29, the pilot oil passage 95 is blocked, and the pilot pressure in the pilot oil passage 95 increases.

An actuator (not shown) for operating the accelerator portion of the engine 36 is provided, and auto idle means (not shown) for operating the actuator based on a detection signal of the pressure sensor 99 is provided.
As a result, when the pilot pressure in the pilot oil passages 95 and 98 is reduced as described above (when all of the first to ninth control valves 21 to 29 are operated to the neutral position), the engine 36 is operated by the actuator. The accelerator part is operated to the idling position. When the pilot pressure in the pilot oil passages 95 and 98 rises (when any of the first to ninth control valves 21 to 29 is operated from the neutral position), the accelerator portion of the engine 36 is moved to the set position on the high speed side by the actuator. Operated. In this case, the setting position on the high speed side can be arbitrarily changed arbitrarily.

[Another Embodiment of the Invention]
In the above-mentioned [Embodiments of the invention], instead of the after-orifice type load sensing means, the pressure compensating valve is located on the upper side of the first, second, third, fifth and ninth control valves 21, 22, 23, 25, 29. A before-orifice type load sensing means provided with 61, 62, 63, 65, 69 may be provided.

Overall side view of backhoe The figure which shows the external appearance of a 1st and 2nd control valve unit, a spacer unit, an inlet unit, and the hydraulic circuit of the vicinity of a 1st and 2nd hydraulic pump Hydraulic circuit diagram of first and second control valve unit, spacer unit, inlet unit Hydraulic circuit diagram near the first control valve and pressure compensation valve Hydraulic circuit diagram of right and left control lever and pilot valve

Explanation of symbols

3 Working device 21, 22, 23, 25, 29 Control valve 24, 26, 27, 28 Control valve 41, 42 Hydraulic pump 91 First control valve unit 92 Second control valve unit 93, 94 Base unit

Claims (2)

A first control valve unit in which a plurality of control valves are arranged in a row, a second control valve unit in which a plurality of control valves are arranged in a row, and the first and second control valve units arranged in a row A base unit connected across the end on the same side,
A variable displacement hydraulic pump for supplying hydraulic oil to the control valve of the first control valve unit is provided, and the hydraulic oil for the control valve of the first control valve unit is supplied to a work device provided in the fuselage. And
A hydraulic circuit structure for a work vehicle, comprising: load sensing means for changing a discharge flow rate of the hydraulic pump based on a maximum work load among work loads applied to the work device.   2. The hydraulic circuit for a work vehicle according to claim 1, further comprising: a work device provided at a front portion of the machine body, wherein the first control valve unit is disposed on a front side of the machine body with respect to the second control valve unit. Construction.

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