JP5429098B2 - Hydraulic circuit for construction machinery - Google Patents

Description

  The present invention relates to a hydraulic circuit for a construction machine, such as a hydraulic excavator, which includes a lower traveling body, an upper swing body, and a work attachment.

  The background art will be described using a hydraulic excavator as an example.

  As shown in FIG. 3, the excavator is mounted on a crawler-type lower traveling body 1 so that an upper swing body 2 can be swung around an axis X perpendicular to the ground. The arm 4 and the bucket 5 and the work (excavation) attachment 9 comprising the cylinders 6, 7, and 8 for the boom, the arm, and the bucket that operate the arm 4 are mounted.

  As other hydraulic actuators, left and right traveling motors that drive the lower traveling body 1 (left and right crawlers) and a turning motor 12 that turns the upper rotating body 2 (not shown) are provided.

In this hydraulic excavator, as shown in Patent Document 1, in order to ensure the independence of the turning operation and other actuator operations, the entire circuit is
i. a first circuit to which one of the left and right side travel motors and the boom cylinder belong;
ii. a second circuit to which the other travel motor and arm cylinder belong;
iii. It is known to adopt a three-circuit / three-pump system in which the three circuits are divided into a third circuit to which the swing motor belongs, and these three circuits are driven by separate pumps (first to third pumps).

  Further, in this known technique, in order to ensure straight traveling performance, both the first and second circuits are configured as a travel priority circuit in which travel motors are arranged on the most upstream side of the flow of pump oil, respectively. When both traveling operations in which the motors are driven to each other are performed, the first and second pump oils are preferentially supplied to the traveling motor, while the third pump is discharged toward the third circuit. 3 pump oil is joined to both the first and second circuits (actuators other than traveling) via a junction valve.

  As a result, the operation of the other actuator can be ensured while maintaining the straight traveling performance.

  In this case, when the arm cylinder of the second circuit is not operated, the control valve for the cylinder is in the neutral position and the bleed-off passage communicates with the tank. The pump pressure does not rise sufficiently.

  For this reason, other actuator operations, such as boom raising and turning operations, are delayed, but this is not a problem because it is an operation while traveling, and is rather preferable for safety.

  On the other hand, regardless of whether or not both traveling operations are performed, when the boom is operated, both the first and second circuits are connected to the third pump oil via the merging valve in the same manner as when both the traveling / other actuators are operated. To join.

Japanese Patent No. 4137431

  According to the known technology, the third pump oil for turning is supplied to the first circuit (boom cylinder) and both during the travel / operation of other actuators and the boom raising operation unrelated to the travel operations as described above. Since it is configured to join the second circuit (arm cylinder), if the arm cylinder of the second circuit is not operated during boom raising operation, the control valve for the cylinder is in the neutral position and the bleed-off Since the passage communicates with the tank, the third pump oil flows into the tank through the second circuit, and the pump pressure does not rise sufficiently.

  As a countermeasure, the pump pressure is raised by providing a throttle in the junction path to the second circuit, but there is a limit.

  Therefore, the boom raising pressure is lowered and the boom raising performance is deteriorated.

  Further, when the boom is raised / turned, in addition to the boom raising performance, the turning acceleration pressure does not increase, and the turning acceleration performance is extremely deteriorated.

  For this reason, when dumping earth and sand in a bucket, the cycle time becomes long, and the problem that work efficiency falls remarkably has arisen.

  It is possible to construct a circuit so that the third pump oil is joined to the first circuit through a path different from the joining valve during the boom raising operation.

  However, this makes the connection between the circuits complicated, and a dedicated valve is required, so that the circuit configuration becomes complicated and the cost is increased.

  Therefore, the present invention is based on the above-described three-circuit / 3-pump method, and on the premise that the third pump oil is merged into both the first and second circuits when traveling by the merge valve. When the boom raising operation (including the combined boom raising / turning operation) is performed while the circuit configuration is only performed, the pump pressure of the third pump is secured and the boom raising performance (plus turning acceleration performance during combined operation) ) Can provide a hydraulic circuit for construction machinery.

  The invention of claim 1 has all the following requirements (A) to (G).

  (A) A lower traveling body that is driven and driven by left and right traveling motors, an upper revolving body that is rotatably mounted on the lower traveling body and is driven to rotate by a turning motor, and an operation that is attached to the upper revolving body Have an attachment.

  (B) This work attachment has a boom operated by a boom cylinder as a hydraulic actuator and an arm operated by an arm cylinder.

  (C) As a hydraulic actuator circuit, a first circuit to which one of the left and right side traveling motors and the boom cylinder belong, a second circuit to which the other traveling motor and the arm cylinder belong, and the swing motor And each circuit has a control valve for controlling the operation of each hydraulic actuator.

  (D) It has a first pump for the first circuit, a second pump for the second circuit, and a third pump for the third circuit as a hydraulic pressure source.

  (E) Each of the first and second circuits is configured as a travel priority circuit in which the travel motor is disposed on the most upstream side.

  (F) having a merging valve for merging the third pump oil discharged from the third pump toward the third circuit into both the first and second circuits.

  (G) The merging valve includes a first position where the third pump oil is unloaded through the second circuit, a double traveling operation in which the left and right traveling motors are simultaneously driven, and another hydraulic actuator operation. A second position where the third pump oil is merged with both the first and second circuits, and when a boom raising operation is performed, the third pump oil is merged with the first circuit. And a third position for blocking the second circuit.

  According to a second aspect of the present invention, in the configuration of the first aspect, the third pump oil is supplied so that the pump pressure of the third pump is higher than the pressure of the first circuit at the third position of the merging valve. A throttle is provided in the passage that joins the first circuit.

  According to the present invention, when another actuator operation is performed during both travelings, the third pump oil is merged into both the first and second circuits by the merge valve, while the boom raising operation ( When a boom raising / turning combined operation is performed), the third pump oil is joined to the first circuit but is shut off from the second circuit. It is possible to secure the pump pressure of the third pump at the time of boom raising / turning operation) and improve the boom raising performance (plus turning acceleration performance at the time of boom raising / turning operation) to improve the work efficiency.

  In addition, since the third position is added to the merging valve for merging the third pump oil to both the first and second circuits during both travels, the merging / blocking action is performed, so a new valve and Complicated circuit configuration and cost increase as in the case of adding a circuit can be avoided.

  In this case, according to the invention of claim 2, the third pump oil is supplied to the first pump oil so that the pump pressure of the third pump is higher than the pressure of the first circuit (boom pressure) at the third position of the junction valve. Since the throttle is provided in the passage to be supplied to the circuit, the turning acceleration performance can be further improved by raising the turning pressure during boom raising / turning.

1 is a hydraulic circuit diagram showing an embodiment of the present invention. It is an enlarged view of the junction valve provided in the circuit. 1 is a schematic side view of a hydraulic excavator to which the present invention is applied.

  In the embodiment, a hydraulic excavator is applied.

  In the hydraulic circuit according to the first embodiment, as shown in FIG. 1, as the hydraulic actuator circuit, the first circuit A to which the left traveling motor 10, the boom cylinder 6 and the bucket cylinder 8 belong, the right traveling motor 11 and the arm cylinder. 7 and the third circuit C to which only the swing motor 12 belongs, and the first pump 13 for the first circuit A and the second pump for the second circuit B as hydraulic pressure sources. 14 and a third pump 15 for the third circuit C are provided.

  Each circuit A, B, C is provided with a control valve (direction switching valve) which is a hydraulic pilot type spool valve for controlling the operation of each hydraulic actuator.

  That is, the first circuit A includes control valves 16, 17, 18 for the boom cylinder, bucket cylinder, and left travel motor, and the second circuit B includes both control valves 19 for the arm cylinder and right travel motor. , 20 and the third circuit C are respectively provided with control valves 21 for the turning motor.

  Here, both the first and second circuits A and B are configured as a travel priority circuit in which the travel control valves 18 and 20 are located on the most upstream side of the flow of the pump oil as shown in the drawing, The first pump oil discharged from the pump 13 is preferentially supplied to the left travel motor 10 and the second pump oil discharged from the second pump 14 is preferentially supplied to the right travel motor 11.

  Therefore, when both the travel motors 10 and 11 are driven simultaneously, and an operation for supplying the entire pump flow rate to the travel motors 10 and 11 is performed, the travel motors in the first and second circuits A and B are used. No pump flow rate is supplied to other hydraulic actuators.

  Therefore, a merging valve 22 is provided as means for securing other actuator operations during both travelings, and the third pump oil discharged from the third pump 15 toward the third circuit C (swing motor 12) during both travelings. The first and second circuits A and B are configured to merge with the third circuit C in a tandem or parallel flow.

  The joint valve 22 will be described in detail with reference to FIG.

  The merging valve 22 has first and second pilot ports 22a, 22b on one side, and is switched to a first, second, third position a, b, c by the introduced pilot pressure. It is configured as a pilot switching valve.

  The input port of the junction valve 22 is connected to the third pump 15 by an unload passage 23 that passes through the bleed-off passage of the turning control valve 21 and a parallel passage 24 that bypasses the control valve 21.

  On the other hand, the output port is connected to both the first and second circuits A and B via merge lines (hereinafter referred to as first merge line and second merge line) 25 and 26.

  The first pilot port 22 a of the junction valve 22 is connected to the pilot hydraulic power source 28 via the first pilot line 27, and the second pilot port 22 b is connected to the boom raising pilot line 30 of the boom cylinder control valve 16 via the second pilot line 29. Are connected to each.

  Further, the control valves 16 to 20 other than the swing motor control valve 21 are configured as switching valves with side bypass provided with side bypass portions 16a, 17a, 18a, 19a, and 20a, and the side bypass portions are connected to each other. Thus, a side bypass line 31 is configured.

  One end of the side bypass line 31 is connected to the first pilot line 27 of the junction valve 22, and the other end is connected to the tank line 32 leading to the tank T. The side bypass line 31 depends on the operation status of the control valves 16 to 20. Is opened / closed, the pilot pressure (primary pressure) is cut off / introduced to the first pilot port 22a of the merging valve 22.

  The relationship between this operating situation, the opening / closing of the side bypass line 31 and the position of the merging valve 22 is as follows.

i. When only both traveling operations are performed Since the side bypass line 31 is connected to the tank line 32 and the pilot pressure from the hydraulic pressure source 28 falls into the tank T, the pilot pressure is applied to the first pilot port 22a of the merging valve 22. Does not act, and the merging valve 22 is in the neutral first position a.

ii. When both traveling operations and other actuator operations are performed Since the side bypass line 31 is cut off from the tank line 32 by the side bypass portion of the operated control valve, the pilot pressure from the hydraulic source 28 is merged. 22 is introduced into the first pilot port 22a, and the merging valve 22 is switched to the second position B.

iii. When the boom raising operation is performed regardless of the both traveling operations Since the boom raising operation is performed, the boom raising pilot pressure is applied to the second pilot port 22b of the merging valve 22; Switch to position c.

  The situation of the flow of the third pump oil at the first to third positions (a), (b) and (c) of the merging valve 22 is as follows.

(I) First position (a) In this position (i), the parallel passage 24 is blocked, and only the unload passage 23 is enabled, and the third pump oil passes through the first and second merging lines 25 and 26 to the first position. The second circuits A and B can be merged.

  However, if the arm is not operated at this time, the second merging line 26 is connected to the tank T through the bleed-off passage of the arm cylinder control valve 19, so that the pump pressure of the third pump 15 does not increase and the first circuit A The actuator (boom and bucket cylinders 6 and 8) does not move even when the actuator is operated.

(II) Second position B In this second position B, the third pump oil passes through the unload passage 23 and the parallel passage 24, and passes through the first and second merge lines 25, 26 to the first, The current flows through both the second circuits A and B.

  Thereby, the actuator operation other than traveling can be ensured during both traveling.

  At this time, a throttle 33 (see FIG. 2) is provided in the junction passage of the junction valve 22 to the second circuit C so that the pump pressure of the third pump 15 is raised even when the arm is not operated.

(III) Third position C In this third position c, the third pump oil passes through the unload passage 23 and the parallel passage 24, joins only the first circuit A through the first joining line 25, and the second Circuit B is shut off.

  In this circuit state, the pump pressure of the third pump 15 is not reduced, and sufficient boom raising pressure and turning acceleration pressure during boom raising / turning are ensured.

  Here, a throttle 34 (see FIG. 2) is provided in a passage for joining the third pump oil to the first circuit A so that the pump pressure of the third pump 15 becomes higher than the pressure of the first circuit A (boom pressure). It is provided to adjust the balance between turning acceleration performance and boom raising performance.

  As described above, this hydraulic circuit is premised on a configuration in which the third pump oil is merged into both the first and second circuits A and B by the merging valve 22 when another actuator operation is performed during both travels. When a boom raising operation (including a combined boom raising / turning operation) is performed regardless of both traveling operations, the third pump oil is merged into the first circuit A, but to the second circuit B. For the former, the pump pressure (boom raising pressure, turning acceleration pressure) of the third pump 15 is secured during the boom raising operation or the combined boom raising / turning operation. In the former case, the boom is raised. In the latter case, both boom raising performance and turning acceleration performance can be improved.

  For this reason, for example, when carrying out a boom raising operation or a combined boom raising / turning operation after loading earth and sand in a bucket, the boom is raised and turned quickly to shorten the cycle time and improve the work efficiency. Can do.

  In addition, since the third position C is added to the merging valve 22 for merging the third pump oil into the first and second circuits A and B during both travels, the merging / blocking action is performed. Therefore, it is possible to avoid a complicated circuit configuration and an increase in cost as in the case of adding a new valve and circuit.

  In this case, at the third position C of the merging valve 22, a throttle 34 is provided in a passage for supplying the third pump oil to the first circuit A, thereby reducing the pump pressure of the third pump 15 to the pressure of the first circuit A (boom Therefore, the turning acceleration performance can be further improved by increasing the turning pressure during boom raising / turning.

  Incidentally, another actuator (for example, a spare service actuator) may be added to the second circuit B in parallel.

  Further, the present invention is not limited to a hydraulic excavator, and can be applied to a crusher, a dismantling machine, or the like that includes a hydraulic excavator as a base and a breaker or an open / close type crusher attached in place of a bucket.

DESCRIPTION OF SYMBOLS 1 Lower traveling body 2 Upper turning body 3 Boom 4 Arm 5 Bucket 6 Boom cylinder 7 Arm cylinder 8 Bucket cylinder 9 Work attachment 10 Left traveling motor 11 Right traveling motor 12 Turning motor A 1st circuit B 2nd circuit C 3rd circuit 13 1st pump 14 2nd pump 15 3rd pump 16-21 Control valve 22 Merge valve 23 Unload passage for joining 3rd pump oil to 1st circuit or 2nd circuit 24 3rd pump oil to 1st circuit or Parallel passage for joining the second circuit 25 First joining line for joining the third pump oil to the first circuit 26 Second joining line for joining the third pump oil to the second circuit T tank

Claims (2)

A hydraulic circuit for a construction machine characterized by satisfying all the following requirements (A) to (G):
(A) A lower traveling body that is driven and driven by left and right traveling motors, an upper revolving body that is rotatably mounted on the lower traveling body and is driven to rotate by a turning motor, and an operation that is attached to the upper revolving body Have an attachment.
(B) This work attachment has a boom operated by a boom cylinder as a hydraulic actuator and an arm operated by an arm cylinder.
(C) As a hydraulic actuator circuit, a first circuit to which one of the left and right side traveling motors and the boom cylinder belong, a second circuit to which the other traveling motor and the arm cylinder belong, and the swing motor And each circuit has a control valve for controlling the operation of each hydraulic actuator.
(D) It has a first pump for the first circuit, a second pump for the second circuit, and a third pump for the third circuit as a hydraulic pressure source.
(E) Each of the first and second circuits is configured as a travel priority circuit in which the travel motor is disposed on the most upstream side.
(F) having a merging valve for merging the third pump oil discharged from the third pump toward the third circuit into both the first and second circuits.
(G) The merging valve includes a first position where the third pump oil is unloaded through the second circuit, a double traveling operation in which the left and right traveling motors are simultaneously driven, and another hydraulic actuator operation. A second position where the third pump oil is merged with both the first and second circuits, and when a boom raising operation is performed, the third pump oil is merged with the first circuit. And a third position for blocking the second circuit.   In the third position of the merging valve, a throttle is provided in the passage for merging the third pump oil into the first circuit so that the pump pressure of the third pump is higher than the pressure of the first circuit. The hydraulic circuit for a construction machine according to claim 1.

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