JP5429099B2 - 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 travel priority circuits in which travel motors are arranged on the most upstream side of the flow of pump oil, When both traveling operations in which the traveling motors are simultaneously driven are performed, the first and second pump oils are preferentially supplied to the traveling motor, while being discharged from the third pump toward the third circuit. A configuration is adopted in which the third 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.

Japanese Patent No. 4137431

  However, according to the known technology, even when the boom raising operation is performed regardless of the two traveling operations, the merging valve is switched to the same position as when both the traveling / other actuators are operated. Since the 3 pump oil is joined to the first circuit (boom cylinder) and the second circuit (arm cylinder), the pump pressure of the third pump does not increase if the arm cylinder is not operated at this time.

  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 performance at the time of boom raising / turning operation that requires high pressure deteriorates, and when dumping by loading earth and sand into the bucket, one or both of turning and boom raising are not in time, and the cycle time becomes longer and the work efficiency is increased. There has been a problem in that the remarkably decreases.

  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 when the boom is raised / turned.

  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. A hydraulic circuit for a construction machine capable of improving the boom raising / turning performance while taking a circuit configuration to be performed only.

  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 Having attachments.

  (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 has first to third positions, and unloads the third pump oil through the second circuit at the first position, and the left and right traveling motors are driven simultaneously. When both traveling operations are performed and another actuator operation is performed, the second pump position is switched to join the third pump oil to both the first and second circuits, and the boom raising / turning operation is performed. Only when it is switched to the third position, the third pump oil is merged with the first circuit and shut off with respect to the second circuit.

  According to a second aspect of the present invention, in the configuration of the first aspect, the input port of the merging valve bypasses the control valve with an unload passage that passes through the bleed-off passage of the turning control valve with respect to the third pump. While connected to the parallel passage, the output port of the junction valve is connected to the first circuit via the first junction line and to the second circuit via the second junction line, respectively. The first joining line is connected to the parallel passage and the second joining line is connected to the unloading passage at the position.

  According to a third aspect of the present invention, in the configuration of the first or second aspect, the third pump is configured such 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 a passage for joining oil to 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 / turning operation is performed. Only the merging valve is switched to the third position so that the third pump oil is merged into the first circuit but is shut off from the second circuit. The work efficiency can be improved by securing the pressure, improving the boom and turning acceleration.

  Further, the merging action of the third pump oil to the first circuit (boom cylinder) is performed only during the combined operation of raising the boom / turning, and the merging action of the third pump oil to the boom cylinder is caused only by the boom raising operation. Since this is not performed, there is no inconvenience that the operability deteriorates due to the balance of the third pump flow rate during the combined operation of raising the boom and other actuators.

  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 second aspect of the present invention, the bleed-off passage of the turning valve is shut off by operating the turning control valve at the third position of the merging valve, whereby the third pump and the second circuit are disconnected. Since the communication is cut off, pilot pressures for both boom raising and turning are introduced into the merging valve and switched to the third position. At this position, the merging valve itself communicates with the third pump and the second circuit. Compared to the case of a shut-off configuration, the pilot system configuration is simple.

  According to the invention of claim 3, the third pump oil is supplied to the first circuit 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 turned, the turning pressure at the time of boom raising / turning can be increased to further improve the turning acceleration performance.

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 merges with the first circuit A through the first merge line 25 through the parallel passage 24, while the turning control valve 21 is not operated. Only when it is in a state (neutral state), it passes through the unload passage 23 and merges with the second circuit B through the second merge line 26.

  However, if the arm is not operated at this time, the second merging line 26 communicates with the tank T through the arm cylinder control valve 19, so that all the third pump oil is unloaded and does not flow into the first circuit A.

  When the turning operation is performed at the third position c, that is, when the boom raising / turning operation is performed, the turning control valve 21 is activated and the bleed-off passage is blocked. The third pump 15 is cut off from the unload passage 23 (tank T).

  As a result, the third pump oil is sent to the third circuit C (the turning motor 12) and the first circuit A in parallel.

  In this circuit state, the pump pressure of the third pump 15 is not reduced, and sufficient boom raising pressure and turning pressure 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, in this hydraulic circuit, on the assumption that the third pump oil is merged with both the first and second circuits A and B when another actuator operation is performed during both travels, The third pump oil is joined to the first circuit A but shut off from the second circuit B only when the boom raising / turning operation is performed. The pump pressure (boom raising pressure, turning acceleration pressure) of the third pump 15 can be secured, and both the boom raising performance and the turning acceleration performance can be enhanced.

  For this reason, when dumping earth and sand in the bucket, the boom can be raised / turned quickly to shorten the cycle time and improve the work efficiency.

  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.

  The merging action of the third pump oil to the first circuit (boom cylinder) is performed only when the boom is raised / turned, and the merging action of the third pump oil to the boom cylinder is not performed only by the boom raising operation. Therefore, there is no inconvenience that the operability deteriorates due to the third flow rate of the pump during the combined operation of raising the boom and other actuators.

  In this case, according to the embodiment, when the turning control valve 21 is operated at the third position C of the merging valve 22, the bleed-off passage of the valve 21 is shut off, thereby the third pump 15 and the second circuit. Since the communication with B is cut off, pilot pressures for both boom raising and turning are introduced into the merging valve 22 and switched to the third position C. At this position, the third pump 15 is switched by the merging valve 15 itself. The configuration of the pilot system is simpler than the configuration in which the communication between the first circuit B and the second circuit B is cut off.

  Further, the third pump oil is supplied to the first circuit A so that the pump pressure of the third pump 15 is higher than the pressure of the first circuit A (boom pressure) at the third position C of the junction valve 22. Since the throttle 34 is provided in the passage, the turning acceleration performance can be further improved by increasing the turning pressure when the boom is raised / turned.

  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 (3)

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 Having attachments.
(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 has first to third positions, and unloads the third pump oil through the second circuit at the first position, and the left and right traveling motors are driven simultaneously. When both traveling operations are performed and another actuator operation is performed, the second pump position is switched to join the third pump oil to both the first and second circuits, and the boom raising / turning operation is performed. Only when it is switched to the third position, the third pump oil is merged with the first circuit and shut off with respect to the second circuit.   An input port of the merging valve is connected to an unload passage that passes through the bleed-off passage of the turning control valve and a parallel passage that bypasses the control valve with respect to the third pump, while an output port of the merging valve Are connected to the first circuit via a first merge line and to the second circuit via a second merge line, and the first merge line is connected to the parallel path at a third position of the merge valve. 2. The hydraulic circuit for a construction machine according to claim 1, wherein the second merging line is connected to the unload passage.   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 or 2.

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