JP2006071105A - Hydraulic circuit of construction machinery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rational, effective, and economical hydraulic circuit of construction machinery by a simple configuration. <P>SOLUTION: This hydraulic circuit of the construction machinery provided with an oil pressure driving type actuator (a cylinder 4 and a turning motor 6 of a work machine) is provided with an oil cooler circuit 20 for absorbing oil in an oil tank 2 by a fixed flow rate pump 21 and returning oil into a suction pipe passage 15 of a main pump 1 through an oil cooler 9 separately from a return circuit from the actuator into the oil tank 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydraulic circuit of a construction machine that controls the driving of an actuator having a large load used in a hydraulic excavator or the like.

  Conventionally, in a construction machine having a turning mechanism such as a hydraulic excavator, the actuator is driven by a hydraulic drive, and in a hydraulic circuit that controls the drive, an oil cooler is generally arranged in the return circuit to return oil. Cooling process is done.

  FIG. 11 shows an example of the implementation of the hydraulic circuit to the actuator in the construction machine described above. The main pump 1 that supplies the operating pressure oil from the oil tank 2 to the work machine cylinder 4 or the swing motor 6 is shown. A direction switching valve 5 or a direction switching valve 5 ′ is provided in the oil supply pipe 3, and an oil cooler 9 and a filter 11 are provided in a return circuit 7 from these actuators (working machine cylinder 4, swing motor 6) to the oil tank 2. It has been. A lift check valve 8 is provided in the return circuit 7 as a means for preventing the occurrence of cavitation during a sudden stop by a turning operation by the turning motor 6, and the return circuit 7 returns to the oil supply line of the turning motor 6. An oil suction conduit 7a is connected. In the figure, reference numeral 10 is a check valve for the oil cooler 9, and 13 is a strainer.

  Further, in a hydraulic circuit that controls the driving of a hydraulically driven actuator, in particular, an actuator having a large inertia load such as a turning device, as a prior art for preventing cavitation that occurs when the actuator suddenly stops, for example, Patent Literature 1 or Patent Document 2 and the like.

  The one disclosed in Patent Document 1 is configured to prevent a sudden fluctuating pressure by disposing a make-up valve on the negative pressure side of the swing motor and sucking the return oil. Yes. Further, in the one disclosed in Patent Document 2, in order to prevent the occurrence of cavitation due to overrun, a throttle valve is provided in the return circuit so as to increase the back pressure in the motor unit and return to the tank through the oil cooler. It is configured.

JP-A-2-212603 JP-A-2-217529

However, the above prior art has the following problems.
a) In the prior art shown in FIG. 11, all the return oil from the actuator is returned to the oil tank via the lift check valve, and an oil cooler and a filter are installed in this return circuit. Pressure loss increases. In particular, the back pressure is required to prevent cavitation caused by the turning motion, and it is not necessary to configure the return side of other devices (actuators) so that the back pressure acts. Therefore, wasteful energy is consumed, which is not economical.
b) Further, since the return oil from the actuator passes through the entire return circuit, the flow rate change is too large (the fluctuation is large), so the heat exchange efficiency is poor. For this reason, a large-capacity oil cooler is required, and there is a problem in terms of equipment configuration such as a large pipe diameter.
c) Although disclosed in Patent Document 1 and Patent Document 2 show prevention of cavitation incidental to a turning motion by an actuator, nothing is pursued for more economical demand. It has not been done.

  The present invention has been made in view of such problems, and an object thereof is to provide a hydraulic circuit for a construction machine that has a simpler configuration, is rational, effective, and has high economic efficiency. It is.

In order to achieve the above object, the hydraulic circuit of the construction machine according to the first invention comprises:
In the hydraulic circuit of the construction machine, the oil in the oil tank is supplied to the hydraulically driven actuator by the main pump, and the oil discharged from this actuator is returned to the oil tank.
Separately from the return circuit from the actuator to the oil tank, an oil cooler circuit is provided which sucks oil in the oil tank by a constant flow pump and returns it to the suction line of the main pump through the oil cooler. is there.

The hydraulic circuit of the construction machine according to the second invention is
In the hydraulic circuit of the construction machine, the oil in the oil tank is supplied to the hydraulically driven actuator by the main pump, and the oil discharged from this actuator is returned to the oil tank.
Separately from the return circuit from the actuator to the oil tank, an oil cooler circuit that sucks oil in the oil tank by a constant flow pump and returns it to the vicinity of the strainer provided in the suction pipe portion of the main pump through the oil cooler is provided. It is characterized by.

  In the second aspect of the invention, it is preferable that a baffle plate is provided in the oil tank so that the return oil from the return circuit and the return oil from the oil cooler circuit are not mixed in the oil tank ( Third invention).

Next, the hydraulic circuit of the construction machine according to the fourth invention is
In the hydraulic circuit of the construction machine, the oil in the oil tank is supplied to the hydraulically driven actuator by the main pump, and the oil discharged from this actuator is returned to the oil tank.
Separately from the return circuit from the actuator to the oil tank, an oil cooler circuit for sucking oil in the oil tank by a constant flow pump and passing through an oil cooler and joining the suction pipe portion of the main pump in the oil tank is provided. It is a feature.

  In any one of the first to fourth inventions, it is preferable that a swirl suction circuit branched from the discharge side of the constant flow pump and connected to the negative pressure side of the actuator via a check valve is provided (fifth). invention).

  According to the first aspect of the present invention, as a hydraulic circuit that controls driving of an actuator having a large inertia load accompanying a turning motion, a response to a portion where the inertia load is large and a response to a portion that performs normal motion are performed separately. Since the oil cooler circuit is provided separately from the return circuit, it is possible to minimize the equipment that constitutes the hydraulic circuit, and it is possible to reduce the consumption of excess energy and achieve economic effects. Can be significantly improved. Further, since the oil cooled by the oil cooler in the oil cooler circuit is directly returned to the suction pipe of the main pump, only a deficient amount needs to be sucked from the oil tank, so that the cooling effect of the oil supply can be enhanced.

  Further, according to the second invention, in addition to the same effects as the first invention, the oil cooled by the oil cooler in the oil cooler circuit is returned to the vicinity of the strainer provided in the suction conduit of the main pump. Thus, it is possible to supply oil that has been cooled and cleaned as much as possible.

  Here, when the baffle plate as in the third invention is provided, the hot return oil from the actuator and the cooled return oil from the oil cooler circuit are not immediately mixed, so that the temperature increase of the oil supply can be prevented. An effect can be obtained.

  Further, according to the fourth aspect, the same effect as in the first aspect can be obtained.

  If the configuration of the fifth invention is adopted, normally, when a constant amount of oil is circulated and cooled through the oil cooler and a high load acts and pressure fluctuation occurs, the oil cooler circuit is immediately connected to the actuator side. The oil in the pipe line connected to the pipe is sucked, so that the pressure fluctuation can be suppressed and the occurrence of cavitation and the like can be prevented. In addition, since the cooling process is always performed without flowing excess oil, the heat exchange efficiency is increased and the size can be reduced.

  Next, a specific embodiment of a hydraulic circuit for a construction machine according to the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a hydraulic circuit diagram of the construction machine according to the first embodiment of the present invention.

  The hydraulic circuit of the construction machine according to the present embodiment is a hydraulic pressure in the case where at least one work machine cylinder 4 used in a drive unit that performs linear motion and a swing motor 6 of a swing mechanism that performs a swing motion are controlled. The circuit is shown. About oil supply (oil supply pipelines 3 and 3) from the oil pump 2 to the direction switching valve 5 and the direction switching valve 5 ′ for controlling the operation of the work machine cylinder 4 and the swing motor 6 in this hydraulic circuit by the main pump 1. Although it is the same as the conventional one, an oil cooler circuit 20 is separately provided for the return circuit 7 from these actuators (worker cylinder 4 and swing motor 6) to cool the oil circulated by the constant flow pump 21. Thus, the swing suction pipe 23 is branched from the oil cooler circuit 20 so as to be able to cope with fluctuations in the back pressure when the swing motor 6 is stopped.

  The oil cooler circuit 20 is a hydraulic circuit that returns from the oil tank 2 through the oil cooler 9 and directly returns to the suction pipe 15 of the main pump 1, and is fixed in the pipe line from the oil tank 2 to the oil cooler 9 in the oil cooler circuit 20. A flow rate pump 21 is arranged to circulate a constant amount of oil at all times. A return circuit 7 from the actuator is provided with a filter 11, and the return oil is filtered by the filter 11 and returned to the oil tank 2.

  The swirl suction pipe 23 for the swivel motor 6 is branched from the discharge side of the constant flow pump 21, and oil that always flows at a constant flow rate to the back side of the swivel motor 6 at the time of stop is provided with one of the check valves 12. Connected to be inhaled through. In addition, about the code | symbol shown in the figure, the same code | symbol is attached | subjected about the same apparatus as what is used in the conventional hydraulic circuit, The detailed description is abbreviate | omitted (the following is same).

  In the hydraulic circuit of the present embodiment configured as described above, for the hydraulic oil supply control to the work machine cylinder 4 that is mounted on the machine body (not shown) and operates, the directional switching valve 5 is switched as in the conventional case, The work machine cylinder 4 can be moved back and forth to perform the work. In order to perform the turning drive according to the situation of work, the direction switching valve 5 ′ is switched and the turning mechanism mounted on the body is turned in a required direction. At this time, when the turning operation is stopped, a phenomenon of further turning in the turning direction occurs due to inertia. In this state, the oil supply conduit is closed in the turning direction. On the other hand, the hydraulic pressure is increased, but since the pipe line is already closed on the rear side, a negative pressure is generated. As a result, pressure fluctuation occurs in the rotation motor 6 portion, and thus the cavitation is generated as described above. In this case, the oil circulating at a constant flow rate by the constant flow pump 21 is immediately sucked into the negative pressure side of the swing motor 6 through the swing suction pipe 23 to prevent the occurrence of pressure fluctuation.

  In the hydraulic circuit of the present embodiment, as described above, the return oil that passes through the return circuit 7 of the actuator (work machine cylinder 4 or turning motor 6) is always returned to the oil tank 2 through the filter 11 as it is. Further, the oil cooled by the oil cooler 9 is directly sent to the suction pipe 15 of the main pump 1. In this way, the oil cooled by the oil cooler 9 is not mixed in the oil tank having a high temperature, and the high-temperature oil is prevented from being supplied to the suction pipe 15 to the main pump 1. Further, since it is only necessary to suck from the oil tank 2 a shortage of the oil cooled by the oil cooler 9 and sent to the suction pipe 15, the cooling effect of the oil supply can be increased reasonably. Moreover, the oil temperature in the oil tank 2 can be operated without excessively rising. Therefore, all can be covered with a small oil cooler corresponding to the set flow rate, the heat exchange efficiency of the oil cooler 9 can be improved, and the entire hydraulic control unit can be downsized.

(Second Embodiment)
FIG. 2 shows a hydraulic circuit diagram of the construction machine according to the second embodiment of the present invention.

  In the hydraulic circuit of this embodiment, the difference from the first embodiment is that the return circuit 7 of the actuator (work machine cylinder 4 and swing motor 6) is directly connected to the oil tank 2, and the filter 11 is removed from the return circuit 7. ing. The oil cooler circuit 20A is provided with a filter 22 on the suction side or discharge side of the constant flow pump 21 so as to filter cooling oil flowing at a constant flow rate. Note that the tip of the return pipe 20b returned from the oil cooler 9 into the oil tank 2 is arranged so as to be close to the strainer 13 provided in the suction pipe 15 of the main pump 1, so that the oil can be cooled and cleaned as much as possible. Be considered to be. Note that the swirl suction conduit 23 for the swivel motor 6 is branched from the discharge side of the constant flow pump 21 as in the above-described embodiment, and the oil that constantly flows at a constant flow rate to the back side of the swivel motor 6 when stopped is anyway. One of the check valves 12 is connected so as to be sucked.

  In the hydraulic circuit having such a configuration, a constant flow rate in the oil cooler circuit 20A that is constantly circulated is filtered by the filter 22 so that the fluid state of the oil passing through the filter surface is kept constant. As a result, the effect of removing even fine dust can be obtained. Moreover, as described above, the use of the back pressure with respect to the turning motor 6 can be similarly operated to enable smooth operation.

(Third embodiment)
FIG. 3 shows a hydraulic circuit diagram of the construction machine according to the third embodiment of the present invention.

  The present embodiment is different from the above embodiment in that the filter 22 provided in the oil cooler circuit 20 </ b> A is disposed in the return pipe 20 b from the oil cooler 9. Thus, even if the filter 22 provided in the oil cooler circuit 20A is located on the discharge side of the constant flow pump 21, the same effect as that of the second embodiment can be obtained.

(Fourth embodiment)
FIG. 4 shows a hydraulic circuit diagram of the construction machine according to the fourth embodiment of the present invention.

  The present embodiment is different from the third embodiment in that the return pipe 20b of the oil cooler circuit 20A is directly connected to the suction pipe 15 of the main pump 1. In this way, the oil cooled by the oil cooler 9 is sent directly to the suction pipe 15 of the main pump 1 and the cooling oil cleaned by the filter 22 is supplied, as in the first embodiment shown in FIG. This can reasonably enhance the cooling effect of refueling.

(Fifth embodiment)
FIG. 5 shows a hydraulic circuit diagram of the construction machine according to the fifth embodiment of the present invention.

  In the present embodiment, the difference from the fourth embodiment is that the return pipe 20b of the oil cooler circuit 20A is connected so as to join the suction pipe 15 of the main pump 1 in the oil tank 2. If it carries out like this, the cooled oil and the oil in the oil tank 2 will be drawn in effectively according to the oil supply state of the main pump 1, and the effect which reduces the temperature rise of oil supply will be exhibited.

(Sixth embodiment)
FIG. 6 shows a hydraulic circuit diagram of the construction machine according to the sixth embodiment of the present invention.

  In this embodiment, the difference from the second embodiment is that a baffle plate 2a is provided in the oil tank 2 to partition the tank, and hot return oil and an oil cooler from the actuator (the work machine cylinder 4 and the swing motor 6). The point is that the cooled return oil from the circuit 20A is not immediately mixed. In this way, hot return oil is not directly drawn into the suction side of the main pump, and an effect of preventing the temperature rise of the oil supply can be obtained.

(Seventh embodiment)
FIG. 7 shows a hydraulic circuit diagram of the construction machine according to the seventh embodiment of the present invention.

  In the hydraulic circuit of this embodiment, the return circuit 7 of the actuator (work machine cylinder 4 or swing motor 6) is directly connected to the oil tank 2, and the filter is removed from the return circuit 7 in the second embodiment. Although it is the same as that of a form, it has the structure different from the hydraulic circuit of previous embodiment in the oil cooler circuit 20B.

  In the hydraulic circuit of the seventh embodiment, a lift check valve 8 is provided in a return line 20a from the oil cooler 9 to the oil tank 2 in the oil cooler circuit 20B, and the swivel motor 6 swivels upstream of the lift check valve 8. The suction line 24 is branched. The end of the return pipe 20c from the oil cooler 9 to the oil tank 2 is extended to the vicinity of the strainer 13 of the suction part of the main pump 1 connected to the oil supply pipe as in the second embodiment. It is possible to supply.

  In the hydraulic circuit configured as described above, the oil that is cooled is filtered (filtered) so that a constant flow rate in the oil cooler circuit 20B that is constantly circulated is filtered by the filter 22. In addition, when the operation of the swing motor 6 is stopped, as in the second embodiment, the pressure fluctuation cannot be reduced only by the back pressure application operation from the swing suction pipe 24 branched from the oil cooler circuit 20B. By interposing the lift check valve 8 in the return pipe 20a, the internal pressure of the return pipe 20a of the oil cooler circuit can be increased and cavitation can be prevented from occurring in the swing motor 6.

  According to such a configuration, the return oil is returned to the oil tank 2 as it is in the return circuit 7 of the actuator (work machine cylinder 4) as described above during the operation in which the swing motor 6 is not driven, and is returned to the oil cooler circuit 20B. In this way, the steady oil amount is cooled, so that it can be treated rationally as a whole. Therefore, similarly to the above, it is possible to provide an economical apparatus that can reduce the size of the cooler, improve the heat exchange efficiency, and improve the filtration.

(Eighth embodiment)
FIG. 8 shows a hydraulic circuit diagram of the construction machine according to the eighth embodiment of the present invention.

  The present embodiment is different from the seventh embodiment in that the filter 22 is provided on the discharge side of the constant flow pump 21 in the oil cooler circuit 20B. By doing this also, the filtration can be improved as in the seventh embodiment.

(Ninth embodiment)
FIG. 9 shows a hydraulic circuit diagram of the construction machine according to the ninth embodiment of the present invention.

  In this embodiment, the difference from the eighth embodiment is that the return pipe 20c of the oil cooler circuit 20B is connected to the suction pipe 15 of the main pump 1 so that the cooled oil can be directly supplied to the oil supply side. It is configured. If it carries out like this, since what is necessary is just to inhale from the oil tank 2 only in short quantity, the cooling effect of oil supply can be raised reasonably.

(Tenth embodiment)
FIG. 10 shows a hydraulic circuit diagram of the construction machine according to the tenth embodiment of the present invention.

  In the present embodiment, a cooling control mechanism 30 that controls the cooling fan of the oil cooler 9 is added to the oil cooler circuit described in the eighth embodiment. The cooling control mechanism 30 in this hydraulic circuit is provided with a hydraulic motor 32 via a fan regulator 31 between the constant flow pump 21 and the oil cooler 9 in the oil cooler circuit 20C, and the hydraulic motor 32 serves as a radiator 26 of the engine. The cooling fan 33 of the oil cooler 9 provided is driven. In addition, for driving the hydraulic motor 32, a water temperature sensor 26 a for detecting the water temperature in the radiator 26 and an oil temperature sensor 9 a for detecting the oil temperature in the oil cooler 9 are connected to the controller 34, and this controller 34 Thus, the fan regulator 31 is controlled to control the rotation of the cooling fan 33 by the hydraulic motor 32 according to the water temperature of the radiator 26 and the oil temperature in the oil cooler 9, thereby correcting overcooling or insufficient cooling. .

  If the hydraulic circuit having such a configuration is provided, the optimum oil temperature and water temperature are set in advance in the controller 34, so that the most suitable cooling process can be performed and energy loss can be reduced. become.

  As described above, by incorporating the hydraulic circuit of each of the above embodiments into a hydraulically driven construction machine, in particular, a construction machine with a swivel drive, the hydraulic drive unit can be compactly integrated to reduce energy loss. It becomes possible to make it highly economical.

Hydraulic circuit diagram of the construction machine according to the first embodiment of the present invention Hydraulic circuit diagram of the construction machine according to the second embodiment of the present invention Hydraulic circuit diagram of the construction machine according to the third embodiment of the present invention Hydraulic circuit diagram of the construction machine according to the fourth embodiment of the present invention Hydraulic circuit diagram of the construction machine according to the fifth embodiment of the present invention Hydraulic circuit diagram of the construction machine according to the sixth embodiment of the present invention Hydraulic circuit diagram of the construction machine according to the seventh embodiment of the present invention Hydraulic circuit diagram of the construction machine according to the eighth embodiment of the present invention Hydraulic circuit diagram of the construction machine according to the ninth embodiment of the present invention Hydraulic circuit diagram of the construction machine according to the tenth embodiment of the present invention Hydraulic circuit diagram for controlling actuators in conventional construction machinery

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main pump 2 Oil tank 3 Oil supply line 4 Work machine cylinder 5, 5 'Direction switching valve 6 Turning motor 7 Return circuit 8 Lift check valve 9 Oil cooler 10 Check valve 11 Filter 12 Check valve 13 Strainers 20, 20A, 20B, 20C Oil cooler circuit 20a, 20b, 20c Return line 21 Constant flow pump 22 Filter 23, 24 Swirling suction line 26 Radiator 30 Cooling control mechanism 31 Fan regulator 32 Hydraulic motor 33 Cooling fan 34 Controller

Claims (5)

In the hydraulic circuit of the construction machine, the oil in the oil tank is supplied to the hydraulically driven actuator by the main pump, and the oil discharged from this actuator is returned to the oil tank.
Separately from the return circuit from the actuator to the oil tank, there is provided an oil cooler circuit that sucks oil in the oil tank by a constant flow pump and returns it to the suction line of the main pump through the oil cooler. Hydraulic circuit. In the hydraulic circuit of the construction machine, the oil in the oil tank is supplied to the hydraulically driven actuator by the main pump, and the oil discharged from this actuator is returned to the oil tank.
Separately from the return circuit from the actuator to the oil tank, an oil cooler circuit that sucks oil in the oil tank by a constant flow pump and returns it to the vicinity of the strainer provided in the suction pipe portion of the main pump through the oil cooler is provided. A hydraulic circuit for construction machinery.   The hydraulic circuit for a construction machine according to claim 2, wherein a baffle plate is provided in the oil tank so that return oil from the return circuit and return oil from the oil cooler circuit are not mixed in the oil tank. . In the hydraulic circuit of the construction machine, the oil in the oil tank is supplied to the hydraulically driven actuator by the main pump, and the oil discharged from this actuator is returned to the oil tank.
Separately from the return circuit from the actuator to the oil tank, an oil cooler circuit for sucking oil in the oil tank by a constant flow pump and passing through an oil cooler and joining the suction pipe portion of the main pump in the oil tank is provided. A hydraulic circuit for construction machinery.   The hydraulic circuit for a construction machine according to any one of claims 1 to 4, further comprising a turning suction circuit that branches from the discharge side of the constant flow pump and is connected to the negative pressure side of the actuator via a check valve.

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