JP4266848B2 - Backhoe hydraulic circuit structure - Google Patents

Description

  The present invention relates to a hydraulic circuit structure of a backhoe.

In the backhoe hydraulic circuit structure, for example, as disclosed in Patent Document 1, the backhoe device includes a hydraulic pump that supplies hydraulic oil to the traveling device, and the traveling device is in a stopped state (backhoe stopped state). Some hydraulic pump hydraulic fluid is supplied to the backhoe device, and the hydraulic pump hydraulic fluid is supplied to the traveling device when the traveling device is in a driving state (backhoe moving state).
In general, when the traveling device is in a stopped state (backhoe stopped state), the backhoe device is often driven to perform work, and in the traveling device driven state (backhoe moving state), the backhoe device is rarely driven. In order to appropriately cope with these two states, Patent Document 1 adopts the above-described configuration.

In Patent Document 1, in the driving state of the traveling device (backhoe moving state), when hydraulic fluid of the hydraulic pump is supplied to the traveling device, most of the hydraulic oil of the hydraulic pump is supplied to the traveling device. When attempting to drive the boom (backhoe device) upward while moving it, there may be a shortage of hydraulic oil for driving the boom (backhoe device) upward.
Accordingly, in Patent Document 1, an auxiliary hydraulic pump that supplies hydraulic oil to a turning motor that drives to turn the swivel is provided separately from the hydraulic pump described above. For example, the boom (backhoe device) is raised while the backhoe is moved. When driving to the side, the hydraulic oil of the auxiliary hydraulic pump is supplied to the backhoe device.

JP-A-10-37907 (FIGS. 1 and 3)

Since the arm and bucket are supported by the boom in the backhoe device, a relatively large force is required to drive the boom to the ascending side. For example, as disclosed in Patent Document 1, the boom (backhoe) is moved while the backhoe is moved. When the device is driven to the ascending side, the operating oil for driving the boom (backhoe device) to the ascending side may be insufficient even if the operating oil from the auxiliary hydraulic pump is supplied to the backhoe device.
Furthermore, for example, when the boom (backhoe device) is driven to the upward side while moving the backhoe, when the swivel is driven to turn at the same time, the auxiliary hydraulic pump is also operated to the swivel motor that drives the swivel. Since oil is supplied, it is conceivable that the hydraulic oil for driving the boom (backhoe device) to the ascending side is insufficient.

  In the hydraulic circuit structure of the backhoe according to the present invention, when the traveling device is in a stopped state (backhoe stopped state), hydraulic oil of the hydraulic pump is supplied to the backhoe device, and the traveling device is in a driving state (backhoe moving state). When the hydraulic pump hydraulic oil is supplied to the traveling device, for example, when the boom (backhoe device) is driven to the upward side while moving the backhoe, the boom (backhoe device) is raised. The purpose of this is to make it possible to drive properly.

(Constitution)
The first feature of the present invention resides in the following configuration in the hydraulic circuit structure of the backhoe.
A traveling device, a backhoe device, a hydraulic cylinder that drives a boom of the backhoe device up and down, a hydraulic pump and an auxiliary hydraulic pump driven by an engine, and the hydraulic oil of the auxiliary hydraulic pump is routed through the first oil path . The relief valve is connected to the oil passage branched from the first oil passage, and when the traveling device is in a stopped state, the hydraulic oil of the hydraulic pump is supplied to the backhoe. The hydraulic pump hydraulic oil can be supplied to the oil chamber on the boom raising side of the hydraulic cylinder, and the switching means that supplies hydraulic fluid to the hydraulic pump when the traveling device is in the drive state. The operation position is set to the proper ascending position, the descent position where hydraulic oil can be supplied to the oil chamber on the lower side of the boom of the hydraulic cylinder, and the neutral position where hydraulic oil is not supplied to the hydraulic cylinder. A Do control valve, a check valve provided in the second oil passage to the control valve the hydraulic oil from the hydraulic pump, a first oil passage, a second oil passage which is located downstream of the check valve The supply oil passage is connected to the supply oil passage and can be operated to a supply position where the hydraulic oil for the auxiliary hydraulic pump can be supplied to the hydraulic cylinder and a stop position where the hydraulic oil for the auxiliary hydraulic pump is not supplied to the hydraulic cylinder. An operation valve, a throttle part, and a check valve are provided, and when the control valve is operated to the raised position, the operation valve is operated to the supply position, and the operation valve is operated to the supply position. When the swivel base is swiveled by the swivel motor in this state, the hydraulic oil from the first oil passage is supplied to the oil chamber on the boom raising side of the hydraulic cylinder via the supply oil passage and the control valve. is there.

(Function)
When the traveling device is in the stopped state (backhoe stopped state), the hydraulic pump hydraulic oil is supplied to the backhoe device, and when the traveling device is in the driven state (backhoe moving state), the hydraulic pump hydraulic oil is transferred to the traveling device. In Patent Document 1, for example, when the boom (backhoe device) is to be driven upward while moving the backhoe, hydraulic oil of the auxiliary hydraulic pump is supplied to the backhoe device. The hydraulic oil of the auxiliary hydraulic pump is supplied over the entire backhoe device (boom, arm and bucket).

  On the other hand, according to the first feature of the present invention, for example, if the boom of the backhoe device is driven upward while moving the backhoe, the auxiliary hydraulic pump is connected to the hydraulic cylinder that drives the boom of the backhoe device up and down. Is supplied through the operation valve. Thus, according to the first feature of the present invention, the hydraulic oil of the auxiliary hydraulic pump is not supplied over the entire backhoe device (boom, arm and bucket) (Patent Document 1), but the boom of the backhoe device is used. Since the hydraulic oil of the auxiliary hydraulic pump is supplied to the hydraulic cylinder that is driven up and down, it is unlikely that the hydraulic oil for driving the boom of the backhoe device will be insufficient.

According to the first aspect of the present invention, a supply position capable of supplying hydraulic oil of the auxiliary hydraulic pump to the hydraulic cylinder that drives the boom of the backhoe device up and down, and the auxiliary hydraulic pump to the hydraulic cylinder that drives the boom of the backhoe device up and down. An operation valve which can be operated at a stop position where no hydraulic oil is supplied is provided, and when the control valve is operated to the raised position, the operation valve is operated to the supply position.
As a result, according to the first feature of the present invention, the operating valve can reliably cause the operating oil to be supplied to the hydraulic cylinder that drives the boom of the backhoe device up and down. When the hydraulic oil for the auxiliary hydraulic pump does not need to be supplied to the hydraulic cylinder that drives the boom of the backhoe device up and down, the hydraulic oil for the auxiliary hydraulic pump must be reliably supplied to the swing motor that drives the swivel. Can do.

(The invention's effect)
According to the first feature of the present invention, in the hydraulic circuit structure of the backhoe, for example, when attempting to drive the boom of the backhoe device to the upward side while moving the backhoe, the hydraulic oil for driving the boom of the backhoe device to the upward side As a result, the backhoe device can be driven on the rising side of the boom appropriately, and the work performance of the backhoe can be improved.

  According to the first aspect of the present invention, the state in which the hydraulic oil of the auxiliary hydraulic pump is supplied to the hydraulic cylinder that drives the boom of the backhoe device up and down can be reliably displayed by the operation valve. When it is not necessary to supply the hydraulic oil of the auxiliary hydraulic pump to the hydraulic cylinder that drives the boom up and down, the hydraulic oil of the auxiliary hydraulic pump can be reliably supplied to the swing motor that drives the swivel to rotate. As a result, the work performance of the backhoe was improved.

[1]
FIG. 1 shows the entire side surface of the backhoe. A swivel base 2 is supported by rubber crawler type right and left traveling devices 1, and a support bracket 7 swings around a vertical axis P1 at the front of the swivel base 2. A double-acting fourth hydraulic cylinder 14 that is supported freely and drives the support bracket 7 to the right and left is provided, and the backhoe device 3 is provided on the support bracket 7.

  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 part of the swivel base 2, and a control tower 17 is provided at the front part of the swivel base 2. The operation pedal 20 is provided below the control tower 17.

[2]
Next, the operation of the backhoe device 3 and the swivel base 2 by the hydraulic circuit structure and the right and left operation levers 9 and 10 will be described.
As shown in FIGS. 2 and 3, a first control valve 21 (corresponding to a control valve) of the first hydraulic cylinder 11, a second control valve 22 of the second hydraulic cylinder 12, and a third control valve of the third hydraulic cylinder 13 23, the fourth control valve 24 of the turning motor 18, the fifth control valve 25 of the fourth hydraulic cylinder 14, the sixth control valve 26 of the right traveling device 1, the seventh control valve 27 of the left traveling device 1, and the fifth. An eighth control valve 28 of the hydraulic cylinder 15 is provided. Variable displacement first and second hydraulic pumps 41 and 42 (corresponding to a hydraulic pump), a third hydraulic pump 43 (corresponding to an auxiliary hydraulic pump), and a pilot pump 44 driven by the engine 36 are provided.

  As shown in FIGS. 2 and 3, the oil passages 30 and 35 for supplying hydraulic oil to the first, second, third and fifth control valves 21, 22, 23 and 25, and the sixth and seventh control valves 26 and 27 are provided. Oil passages 37 and 38 for supplying hydraulic oil are provided, and oil passages 39 and 40 of the first and second hydraulic pumps 41 and 42 are connected to a switching valve 29 (corresponding to switching means), and an oil passage 30 is provided. , 35, 37, and 38 are connected to the switching valve 29. The switching valve 29 has a first position 29a for supplying hydraulic oil from the first and second hydraulic pumps 41, 42 to the oil passages 30, 35, and an oil passage 37 for supplying the hydraulic oil from the first and second hydraulic pumps 41, 42 to the oil passages 37, 35. 38 is a pilot operated type that is configured to be freely operated at a second position 29b to be supplied to 38, and is biased to the first position 29a. Oil passages 46 and 47 connected to the hydraulic oil tank 45 are provided.

  As shown in FIG. 3, the oil passages 48 and 49 of the third hydraulic pump 43 are connected to the fourth and eighth control valves 24 and 28, and the relief valve 73 is connected to the oil passage 48. A switching valve 51 is connected to the oil passage 50 from the center bypass of the eight control valves 24 and 28, and oil passages 52 and 53 from the switching valve 51 are connected to the oil passages 30 and 46. The switching valve 51 is configured to be freely operated at a first position 51a for supplying the hydraulic oil in the oil passage 50 to the oil passage 46 and a second position 51b for supplying the hydraulic oil in the oil passage 50 to the oil passages 30 and 35. It is an operation type and is biased to the first position 51a.

  As shown in FIG.2 and FIG.3, the 1st-4th control valves 21-24 are comprised by the pilot operation type by pilot pressure, and the neutral return type | mold. The fifth control valve 25 is a mechanically operated and neutral return type operated by the operation pedal 20 (see FIG. 1). The sixth and seventh control valves 26 and 27 are mechanically operated by the right and left travel levers 19 (see FIG. 1) and are configured to be neutral return types. The eighth control valve 28 is a mechanically operated type operated by an operation lever (not shown), and is configured as a neutral return type.

  As shown in FIG. 4, the right operation lever 9 is configured to be freely movable in the front, rear, left, and right directions. The pilot valve 31 generates pilot pressure by the front and rear operations of the right operation lever 9, and the right and left of the right operation 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. The pilot valve 32 generates pilot pressure by the front and rear operations of the left operating lever 10, and the pilot pressure is controlled by the right and left operations of the left operating lever 10. The generated pilot valve 34 is provided, and the pilot pressure of the pilot pump 44 (see FIG. 2) is supplied to the pilot valves 31 to 34. The pilot valve 31 and the first control valve 21, 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, and the pilot valve 34 and the fourth control valve 24 are connected via a pilot oil passage.

  As shown in FIGS. 3 and 4, 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 operated in advance, 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. 2 and 4, when the right operation 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. 2 and 4, 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 4, 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. 2, 3, and 4, 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.

[3]
Next, the operation of the switching valves 29 and 51 will be described.
As shown in FIG. 2, pilot oil passages 54 and 55 are extended from the pilot pump 44, the pilot oil passage 54 is connected to the sixth and seventh control valves 26 and 27, and the pilot oil passage 55 is switched. Connected to the valve 29. When the sixth and seventh control valves 26 and 27 are operated to the neutral position (the right and left traveling devices 1 are stopped), the switching valve 29 is operated to the first position 29a and the first and second hydraulic pressures are operated. The hydraulic oil of the pumps 41 and 42 is supplied to the oil passages 30 and 35.

  As a result, as shown in FIG. 2, the sixth and seventh control valves 26, 27 are operated to the neutral position, and the switching valve 29 is operated to the first position 29a (the right and left traveling devices 1). In the stop state), the hydraulic oil of the first and second hydraulic pumps 41 and 42 is supplied to the first, second, third, and fifth control valves 21, 22, 23, and 25, as described in [2] above. The boom 4 is driven up and down, the arm 5 is driven up and down, the bucket 6 is driven on the soil removal side and the scraping side, and the support bracket 7 is driven right and left.

  As shown in FIG. 2, when the sixth or seventh control valve 26, 27 is operated to the travel position, the switching valve 29 is operated to the second position 29b by the pilot pressure in the pilot oil passage 55, and the first and second control valves 26, 27 are operated. The hydraulic oil of the second hydraulic pumps 41 and 42 is supplied to the oil passages 37 and 38. As a result, in the state where the sixth or seventh control valve 26, 27 is operated to the traveling position and the switching valve 29 is operated to the second position 29b, the hydraulic oil of the first and second hydraulic pumps 41, 42 is changed to the first. The right and left traveling devices 1 are driven by being supplied to the sixth and seventh control valves 26 and 27.

As shown in FIGS. 2 and 3, pilot oil passages 56 and 57 are extended from the pilot pump 44, and the pilot oil passage 56 is connected to the first, second, third and fifth control valves 21, 22, 23 and 25. The pilot oil passage 57 is connected to the switching valve 51.
Thereby, the sixth and seventh control valves 26 and 27 are operated to the neutral position, and the switching valve 29 is operated to the first position 29a (the stopped state of the right and left traveling devices 1). Alternatively, when the first, second, third, and fifth control valves 21, 22, 23, and 25 are operated to the neutral position (the boom 4, the arm 5, the bucket 6, and the support bracket 7 are stopped), the switching valve 51 is the first. The oil passage 50 from the center bypass of the fourth and eighth control valves 24 and 28 is connected to the oil passage 53 by operating to the position 51 a.

  As shown in FIGS. 2 and 3, the sixth or seventh control valve 26, 27 is operated to the traveling position, and the switching valve 29 is operated to the second position 29b (first and second hydraulic pumps 41). , 42 is supplied to the sixth and seventh control valves 26, 27), any one of the first, second, third, fifth control valves 21, 22, 23, 25 is operated from the neutral position. Then, the switching valve 51 is operated to the second position 51b by the pilot pressure of the pilot oil passage 57, the oil passage 50 from the center bypass of the fourth and eighth control valves 24, 28 is connected to the oil passage 52, Connected to the oil passages 30 and 35. As a result, the hydraulic oil of the third hydraulic pump 43 is supplied to the first, second, third and fifth control valves 21, 22, 23 and 25 via the switching valve 51 and the oil passage 52. Driving on the ascending side and descending side, driving on the ascending side and descending side of the arm 5, driving on the soil discharging side and scraping side of the bucket 6, and driving on the right and left of the support bracket 7 can be performed.

[4]
Next, an after orifice type load sensing means will be described.
As shown in FIGS. 2 and 3, pressure compensating valves 61, 62, 63, 65 are provided on the lower side of the first, second, third, fifth control valves 21, 22, 23, 25. As shown in FIG. 3, the oil passage 58 from the first control valve 21 is connected to the pressure compensation valve 61, and the oil passages 59 and 60 from the pressure compensation valve 61 are connected to the first control valve 21. When the first control valve 21 is operated to the neutral position 21c, the oil passages 30, 35, 58, 59, 60 are blocked by the neutral position 21c of the first control valve 21.

  As shown in FIG. 3, when the first control valve 21 is operated to the raised position 21a, the hydraulic oil in the oil passage 30 is moved to the raised position 21a of the first control valve 21, the oil passage 58, the pressure compensation valve 61, the oil passage. 59, supplied to the oil chamber on the ascending side of the first hydraulic cylinder 11 via the ascending position 21a of the first control valve 21 (the oil passage 35 is blocked by the ascending position 21a of the first control valve 21). 1 The hydraulic cylinder 11 is extended and the boom 4 is driven upward. When the first control valve 21 is operated to the lowered position 21b, the hydraulic oil in the oil passage 35 is moved to the lowered position 21b, the oil passage 58, the pressure compensation valve 61, the oil passage 60, and the first control valve 21 of the first control valve 21. Is supplied to the lower hydraulic chamber of the first hydraulic cylinder 11 through the lowering position 21b (the oil passage 30 is blocked by the lowering position 21b of the first control valve 21), and the first hydraulic cylinder 11 is contracted. Then, the boom 4 is driven downward.

  The structures of the first control valve 21 and the pressure compensation valve 61 shown in FIG. 3 are similarly provided in the second, third and fifth control valves 22, 23, 25 and the pressure compensation valves 62, 63, 65 shown in FIG. The pressure compensation valves 61, 62, 63, 65 allow the pressure on the upper side of the first, second, third, and fifth control valves 21, 22, 23, 25 shown in FIGS. And the pressure on the lower side of the pressure compensation valves 61, 62, 63, 65 (pressure in the oil passages 59, 60) is maintained at a predetermined differential pressure.

  As shown in FIG. 2, a flow compensation cylinder 64 for changing the discharge flow rates of the first and second hydraulic pumps 41 and 42 and a pilot operated flow compensation valve 66 are provided, and the pilot pressure in the oil passage 39 is The oil is supplied to the flow compensation cylinder 64 through the pilot oil passage 67, the flow compensation valve 66 and the pilot oil passage 68. A pilot oil passage 69 is connected across the switching valve 29 and the flow compensation cylinder 64. When the switching valve 29 is operated to the first position 29a as described in [3], the oil passage 30, A pilot pressure of 35 is applied as a discharge pressure PPS of the first and second hydraulic pumps 41 and 42 to the flow compensation valve 66 via the switching valve 29 and the pilot oil passage 69, and the switching valve 29 is operated to the second position 29b. In this case, the discharge pressure PPS of the first and second hydraulic pumps 41 and 42 is not applied to the flow rate compensation valve 66.

  As shown in FIG. 2, the pilot oil passages 70 are extended from the lower side of each of the pressure compensation valves 61, 62, 63, 65, and the pilot oil passages 70 are joined and connected to the flow compensation valve 66. The highest pressure of the pressures on the lower side of the pressure compensation valves 61, 62, 63, 65 (pressure in the oil passages 59, 60) is applied to the flow compensation valve 66 as the control signal pressure PLS. As a result, the flow compensation valve 66 and the flow compensation cylinder 64 perform the first control so that the difference between the discharge pressure PPS of the first and second hydraulic pumps 41 and 42 and the control signal pressure PLS is maintained at the set control differential pressure. The discharge flow rates of the first and second hydraulic pumps 41 and 42 are changed. As described above, the after orifice type load sensing means is configured.

  As shown in FIG. 2, the aforementioned control differential pressure is set by a spring 71 and a differential pressure cylinder 72 provided in the flow rate compensation valve 66. 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 72 and the discharge flow rates of the first and second hydraulic pumps 41 and 42 are increased. Becomes larger. Conversely, 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 72 and the discharge flow rates of the first and second hydraulic pumps 41 and 42 are reduced. Get smaller.

[5]
As shown in FIG. 3, a check valve 77 is provided in an oil passage 78 extending between the oil passage 30 and the first control valve 21, and a supply oil passage 74 is extended from the oil passage 48 to supply a supply oil passage. 74 is connected between the first control valve 21 and the check valve 77 in the oil passage 78. A check valve 75 and a throttle portion 76 are provided in the supply oil passage 74, and an operation valve 79 is provided in a portion between the check valve 75 and the throttle portion 76 in the supply oil passage 74. The operation valve 79 is a pilot-operated type that is configured to be freely operated at a supply position 79a for communicating with the supply oil passage 74 and a stop position 79b for blocking the supply oil passage 74, and is urged to the stop position 79b by a spring 79c. Yes. A pilot oil passage 80 extends from a pilot oil passage connecting the pilot valve 31 and the operating portion at the raised position 21 a of the first control valve 21, and the pilot oil passage 80 is connected to the operation valve 79.

  As a result, as described in [3], the sixth or seventh control valve 26, 27 is operated to the travel position, and the switching valve 29 is operated to the second position 29b (first and second). In the state where the hydraulic oil of the hydraulic pumps 41 and 42 is supplied to the sixth and seventh control valves 26 and 27), any one of the first, second, third and fifth control valves 21, 22, 23 and 25 is in the neutral position. , The switching valve 51 is operated to the second position 51 b by the pilot pressure in the pilot oil passage 57, and the oil passage 50 from the center bypass of the fourth and eighth control valves 24, 28 is changed to the oil passage 52. Connected to the oil passages 30 and 35. In this state, the operation valve 79 is still operated to the stop position 79b.

  As shown in FIGS. 2, 3, 4 and [2], the pilot pressures of the pilot valves 31 to 34 are increased as the right and left operation levers 9 and 10 are largely operated from the neutral position. Yes. Thereby, 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 as the right and left operation levers 9 and 10 are largely operated from the neutral position. 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.

  As a result, the operation valve 79 is operated to the supply position 79a by the pilot pressure when the right operation lever 9 is operated to the limit position (maximum speed position) of the post-operation, and the right operation lever 9 is moved to the limit position (maximum position of the post-operation). With the pilot pressure when operated between the high speed position) and the neutral position, the strength of the spring 79c is set so that the operation valve 79 remains at the stop position 79b. In this case, the pilot pressure at which the operation valve 79 is operated to the supply position 79a can be changed by changing the strength of the spring 79c.

  As described above, when the switching valve 51 is operated to the second position 51b, the first control valve 21 is operated to the raised position 21a and the boom 4 is moved by the first hydraulic cylinder 11 as shown in FIG. When driven upward, the operation valve 79 is operated to the supply position 79 a by the pilot pressure in the pilot oil passage 80. In this state, the oil passages 48 and 49 are at a low pressure with respect to the supply oil passage 74 (since the supply oil passage 74 is at a high pressure with respect to the oil passages 48 and 49), the hydraulic oil in the oil passage 48 is supplied oil It does not flow into the path 74.

  As described above, in the state where the switching valve 51 is operated to the second position 51b and the operation valve 79 is operated to the supply position 79a, as shown in FIG. When the swivel base 2 is driven to the right turn side (left turn side) by the turning motor 18, a high load is applied at the start of driving of the turn table 2 to the right turn side (left turn side). Occurs, the relief valve 73 is opened, and the oil passages 48 and 49 become high pressure with respect to the supply oil passage 74 (because the supply oil passage 74 becomes low pressure with respect to the oil passages 48 and 49). The hydraulic oil flows into the supply oil passage 74.

  As described above, when the first control valve 21 is operated to the ascending position 21a as shown in FIG. 3 in the state where the hydraulic oil in the oil passage 48 flows into the supply oil passage 74, it is described in the preceding item [4]. As shown, the hydraulic oil in the oil passages 30 and 78 passes through the rising position 21a of the first control valve 21, the oil passage 58, the pressure compensation valve 61, the oil passage 59, and the rising position 21a of the first control valve 21. In addition to being supplied to the oil chamber on the rising side of the first hydraulic cylinder 11, the hydraulic oil in the oil passage 48 merges from the supply oil passage 74 to the oil passage 78, and the oil on the rising side of the first hydraulic cylinder 11. Supplied to the chamber.

Overall side view of backhoe Hydraulic circuit diagram of backhoe device and traveling device Hydraulic circuit diagram near the first control valve, pressure compensation valve and third hydraulic pump Hydraulic circuit diagram of right and left control lever and pilot valve

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Traveling apparatus 2 Swing stand 3 Backhoe apparatus 4 Boom 11 Hydraulic cylinder 18 Swing motor 21 1st control valve (control valve)
29. Switching valve (switching means)
41, 42 Hydraulic pump 43 Auxiliary hydraulic pump 48 oil passage (first oil passage)
73 Relief valve 74 Oil supply path 75 Check valve
76 Restriction section 77 Check valve 78 Oil passage (second oil passage)
79 Operation valve

Claims (1)

A travel device, a backhoe device, a hydraulic cylinder that drives a boom of the backhoe device up and down, a hydraulic pump and an auxiliary hydraulic pump driven by an engine, and hydraulic oil of the auxiliary hydraulic pump is used as a first oil And a relief valve is connected to the oil passage branched from the first oil passage.
Switching so that hydraulic oil of the hydraulic pump is supplied to the backhoe device when the traveling device is in a stopped state, and hydraulic oil of the hydraulic pump is supplied to the traveling device when the traveling device is in a driven state. And a raised position where hydraulic oil for the hydraulic pump can be supplied to the oil chamber on the boom raising side of the hydraulic cylinder, and a lowered position where the hydraulic oil for the hydraulic pump can be supplied to the oil chamber on the boom lower side of the hydraulic cylinder. And a control valve that can be operated at a neutral position that does not supply hydraulic oil of the hydraulic pump to the hydraulic cylinder,
A check valve is provided in a second oil passage for supplying hydraulic oil from the hydraulic pump to the control valve, and spans the first oil passage and the second oil passage located downstream of the check valve. Connect the supply oil path,
An operation valve which can be freely operated to a supply position where the hydraulic oil of the auxiliary hydraulic pump can be supplied to the hydraulic cylinder, and a stop position where the hydraulic oil of the auxiliary hydraulic pump is not supplied to the hydraulic cylinder; And a check valve,
When the control valve is operated to the raised position, together with the operating valve is configured to be operated in the supply position,
When the swivel motor is swiveled by the swivel motor in a state where the operation valve is operated to the supply position, hydraulic oil from the first oil passage passes through the supply oil passage and the control valve to the hydraulic pressure. A hydraulic circuit structure of a backhoe configured to be supplied to an oil chamber on the boom raising side of a cylinder .

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