JP2021148213A - Construction machine - Google Patents

Abstract

To provide a construction machine capable of installing a hydraulic closed circuit system for directly driving a hydraulic actuator with a hydraulic pump, to perform warming up efficiently in a cold district or the like.SOLUTION: A hydraulic closed circuit system 200 comprises a third branch flow path 97a (97b) that connects a first input/output port 12a (14a) and a charge line 90, and a control valve 70 (71) that opens and closes the third branch flow path 97a (97b) according to a control signal from a controller 57. In a warm-up mode that is an operation mode of circulating hydraulic oil between a closed circuit pump 12 (14) and a tank 25, the controller 57 opens the control valve 70 (71) while an operating lever 56a (56d) is not operated, and controls the tilt of the closed circuit pump 12 (14) so that the hydraulic oil is discharged from the first input/output port 12a (14a).SELECTED DRAWING: Figure 2

Description

The present invention relates to a construction machine such as a hydraulic excavator, and more particularly to a construction machine using a hydraulic closing circuit for directly driving a hydraulic actuator with a hydraulic pump.

In recent years, energy saving has become an important development item in construction machinery such as hydraulic excavators and wheel loaders. It is important to save energy in the hydraulic system itself in order to save energy in construction machinery, and the application of a hydraulic closed circuit system that directly controls a hydraulic actuator by connecting it to a closed circuit with a hydraulic pump is being studied. In this system, there is no pressure loss due to the control valve, and there is no flow loss because the pump discharges only the required flow rate. It is also possible to regenerate the potential energy of the actuator and the energy during deceleration. Therefore, energy saving is possible.

As a background technology of a construction machine combining a hydraulic closing circuit, Patent Document 1 describes a configuration in which a hydraulic closing circuit system is mounted and good operability can be ensured even if a plurality of actuators are operated at the same time. ..

Japanese Patent No. 6134614

The hydraulic oil used in flood control excavators becomes more viscous as the temperature decreases. Therefore, if the hydraulic excavator is started while the hydraulic oil temperature is low, the operability is impaired due to the response delay of the hydraulic equipment. Therefore, when starting the hydraulic excavator in a cold region, the hydraulic pump is operated without moving the actuator to perform the initial warm-up operation to warm the hydraulic oil, and after the hydraulic oil has warmed up to some extent, the actuator is moved to release the hydraulic oil. We are taking steps to warm it up further.

Here, in the hydraulic circuit described in Patent Document 1, when the actuator is not operated, the switching valve connecting the closed circuit pump and the actuator is closed, and the discharge flow rate of the closed circuit hydraulic pump (hereinafter, closed circuit pump) is controlled. Set to zero. This is because unless the discharge flow rate of the closed circuit pump is set to zero, the discharge pressure of the closed circuit pump reaches the relief pressure, a high load acts on the closed circuit pump, the load on the engine increases, and the energy saving performance decreases. Because. However, if the closed circuit pump does not discharge the flow rate, the hydraulic oil in the closed circuit does not circulate and the hydraulic oil in the closed circuit cannot be heated. In this way, in a hydraulic excavator equipped with a hydraulic closed circuit system, the hydraulic oil cannot be circulated by the closed circuit pump without moving the actuator, so that the time required for the initial warm-up operation is extended and the work efficiency is deteriorated. There is a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to mount a hydraulic closed circuit system in which a hydraulic actuator is directly driven by a hydraulic pump, and it is possible to efficiently warm up in a cold region or the like. It is to provide various construction machinery.

In order to achieve the above object, the present invention comprises a hydraulic actuator, an operation lever for instructing the operation of the hydraulic actuator, a closed circuit pump including a bi-tilt variable capacitance pump, and oil of one of the hydraulic actuators. A first flow path connecting the chamber and one input / output port of the closed circuit pump, and the other oil chamber of the hydraulic actuator and the other input / output port of the closed circuit pump. A second flow path connecting the second input / output port, a switching valve capable of opening and closing the first flow path and the second flow path, a tank for storing hydraulic oil, and the hydraulic oil of the tank are sucked in. A charge relief that is provided in the first branch flow path that connects the charge pump to be discharged, the charge line connected to the discharge port of the charge pump, and the charge line and the tank, and regulates the discharge pressure of the charge pump. A valve is provided in a second branch flow path connecting the charge line, the first input / output port, and the second input / output port, and the first input / output port and the second input / output port are provided from the charge line. The first check valve that allows the flow of hydraulic oil to the port and the switching valve are opened and closed according to the presence or absence of operation of the operation lever, and the tilt of the closed circuit pump is controlled according to the operation amount of the operation lever. In a construction machine equipped with a controller, the opening degree of the third branch flow path connecting the first input / output port and the charge line and the opening degree of the third branch flow path according to a control signal from the controller. The controller includes an adjustable control valve, and the controller opens the control valve and opens the first input / output port when the operation lever is not operated in the warm-up mode, which is an operation mode for warming the hydraulic oil of the tank. The tilt of the closed circuit pump shall be controlled so as to discharge the hydraulic oil from the port.

According to the present invention configured as described above, when the operating lever is not operated, the hydraulic oil is circulated between the closed circuit pump and the tank via the charge line, so that the tank and the tank are closed immediately after the engine is started. The hydraulic oil in the circuit can be warmed. This makes it possible to efficiently warm up a construction machine equipped with a hydraulic closed circuit system in which a hydraulic actuator is driven by a closed circuit pump in a cold region or the like.

According to the present invention, it is possible to efficiently warm up a construction machine equipped with a hydraulic closing circuit system in which a hydraulic actuator is directly driven by a hydraulic pump in a cold region or the like.

It is a side view of the hydraulic excavator which concerns on embodiment of this invention. It is a circuit diagram of the hydraulic circuit system in the 1st Example of this invention. It is a flowchart which shows the process of the warm-up mode control part of the controller in 1st Embodiment of this invention. It is a figure (the 1) which shows the state at the time of warm-up of the hydraulic closed circuit system in 1st Example of this invention. It is a figure (the 2) which shows the state at the time of warm-up of the hydraulic closed circuit system in 1st Example of this invention. It is a figure which shows the relationship between the passing flow rate of a check valve, and a pressure loss. It is a circuit diagram of the hydraulic circuit system in the 1st Example of this invention. It is a flowchart which shows the process of the warm-up mode control part of the controller in 2nd Embodiment of this invention.

Hereinafter, a large-sized hydraulic excavator will be taken as an example of the construction machine according to the embodiment of the present invention, and will be described with reference to the drawings. In each figure, the same members are designated by the same reference numerals, and duplicate description will be omitted as appropriate.

FIG. 1 is a side view of the hydraulic excavator according to the present embodiment.

In FIG. 1, the hydraulic excavator 100 is rotatably attached to the lower traveling body 101, the upper slewing body 102 rotatably mounted on the lower traveling body 101, and the front side of the upper slewing body 102 in the vertical direction. It is provided with a front device 103. The lower traveling body 101 is driven by a traveling motor (not shown), and the upper rotating body 102 is driven by a turning motor (not shown).

The front device 103 is attached to the boom 1 rotatably attached to the front side of the upper swing body 102 in the vertical direction, the arm 2 rotatably attached to the tip of the boom 1 in the vertical direction, and the tip of the arm 2. Includes a bucket 3 rotatably mounted in the vertical direction. The boom 1 is driven by the boom cylinder 4, the arm 2 is driven by the arm cylinder 5, and the bucket 3 is driven by the bucket cylinder 6.

The hydraulic excavator 100 according to the present embodiment is equipped with a hydraulic closing circuit system described in each of the following embodiments.

FIG. 2 is a circuit diagram of a hydraulically closed circuit system according to a first embodiment of the present invention. Note that, in FIG. 2, only the parts related to the driving of the boom cylinder 4 and the arm cylinder 5 are shown, and the parts related to the driving of the other actuators are omitted.

In FIG. 2, the engine 9, which is a power source, is connected to a power transmission device 10 that distributes power. The power transmission device 10 is connected to a charge pump 11, closed circuit pumps 12 and 14 including double tilt variable capacitance pumps, and open circuit pumps 13 and 15 composed of single tilt variable capacitance pumps.

The closed circuit pump 12 sucks hydraulic oil at one of the input / output ports 12a and 12b and discharges it from the other input / output port. The discharge direction of the closed circuit pump 12 changes according to the tilt direction, and the discharge flow rate changes according to the engine speed and the pump tilt amount. One input / output port 12a of the closed circuit pump 12 is connected to the rod side oil chamber 4a of the boom cylinder 4 via the switching valve 43a and the flow path 91a, and is connected to the arm cylinder via the switching valve 43b and the flow path 91b. It is connected to the rod-side oil chamber 5a of No. 5. The other input / output port 12b of the closed circuit pump 12 is connected to the bottom side oil chamber 4b of the boom cylinder 4 via the switching valve 43a and the flow path 92a, and is connected to the arm cylinder via the switching valve 43b and the flow path 92b. It is connected to the bottom side oil chamber 5b of 5. When the switching valve 43a is in the communicating position and the switching valve 43b is in the shutoff position, a closed circuit is formed between the closed circuit pump 12 and the boom cylinder 4, and the switching valve 43a is in the shutoff position and the switching valve 43b. Is in a communicating position, a closed circuit is formed between the closed circuit pump 12 and the arm cylinder 5.

The closed circuit pump 14 sucks hydraulic oil at one of the input / output ports 14a and 14b and discharges it from the other input / output port. The discharge direction of the closed circuit pump 14 changes according to the tilt direction, and the discharge flow rate changes according to the engine speed and the pump tilt amount. One input / output port 14a of the closed circuit pump 14 is connected to the rod side oil chamber 4a of the boom cylinder 4 via the switching valve 45a and the flow path 91a, and is connected to the arm cylinder via the switching valve 45b and the flow path 92a. It is connected to the rod-side oil chamber 5a of No. 5. The other input / output port 14b of the closed circuit pump 14 is connected to the bottom side oil chamber 4b of the boom cylinder 4 via the switching valve 45a and the flow path 91b, and is connected to the arm cylinder via the switching valve 45b and the flow path 91b. It is connected to the bottom side oil chamber 5b of 5. When the switching valve 45a is in the communicating position and the switching valve 45b is in the shutoff position, a closed circuit is formed between the closed circuit pump 14 and the boom cylinder 4, and the switching valve 45a is in the shutoff position and the switching valve 45b. Is in a communicating position, a closed circuit is formed between the closed circuit pump 14 and the arm cylinder 5.

The open circuit pump 13 sucks the hydraulic oil of the tank 25 at the suction port and discharges it from the discharge port. The discharge flow rate of the open-circuit pump 13 changes according to the engine speed and the pump tilt amount. The discharge port of the open circuit pump 13 is connected to the bottom side oil chamber 4b of the boom cylinder 4 via the switching valve 44a and the flow path 91a, and is connected to the bottom side of the arm cylinder 5 via the switching valve 44b and the flow path 92b. It is connected to the oil chamber 5b and is connected to the tank 25 via the flow control valve 64.

The open circuit pump 15 sucks the hydraulic oil of the tank 25 at the suction port and discharges it from the discharge port. The discharge flow rate of the open-circuit pump 15 changes according to the engine speed and the amount of tilting of the pump. The discharge port of the open circuit pump 15 is connected to the bottom side oil chamber 4b of the boom cylinder 4 via the switching valve 46a, and is connected to the bottom side oil chamber 5b of the arm cylinder 5 via the switching valve 46b. , It is connected to the tank 25 via the flow control valve 65.

The charge pump 11 sucks the hydraulic oil of the tank 25 at the suction port and discharges it from the discharge port. The discharge flow rate of the open circuit pump 15 changes according to the engine speed. The discharge port of the charge pump 11 is connected to the charge line 90. The charge line 90 is connected to the tank 25 via a branch flow path 93, and a charge relief valve 20 is arranged in the branch flow path 93. The charge relief valve 20 keeps the pressure of the charge line 90 (the discharge pressure of the charge pump 11) at a substantially constant pressure. The set pressure of the charge relief valve 20 can be adjusted by a control signal from the controller 57.

The check valves 30a and 30b are built in the closed circuit pump 12, and the downstream side is connected to the input / output ports 12a and 12b, respectively, and the upstream side is connected to the charge line 90 via the branch flow path 94a. When the pressure of the closed circuit including the closed circuit pump 12 falls below the pressure of the charge line 90, the check valves 30a and 30b replenish the closed circuit with hydraulic oil from the charge line 90 to prevent cavitation.

The check valves 31a and 31b are built in the closed circuit pump 14, and the downstream side is connected to the input / output ports 14a and 14b, respectively, and the upstream side is connected to the charge line 90 via the branch flow path 94b. When the pressure of the closed circuit including the closed circuit pump 14 falls below the pressure of the charge line 90, the check valves 31a and 31b replenish the closed circuit with hydraulic oil from the charge line 90 to prevent cavitation.

The check valves 37a and 37b are connected to the flow paths 91a and 91b on the downstream side, respectively, and to the charge line 90 via the branch flow path 95a on the upstream side. When the pressure of the closed circuit including the boom cylinder 4 falls below the pressure of the charge line 90, the check valves 37a and 37b replenish the closed circuit with hydraulic oil from the charge line 90 to prevent cavitation.

The check valves 38a and 38b are connected to the flow paths 92a and 92b on the downstream side, respectively, and to the charge line 90 via the branch flow path 95b on the upstream side. When the pressure of the closed circuit including the arm cylinder 5 falls below the pressure of the charge line 90, the check valves 38a and 38b replenish the closed circuit with hydraulic oil from the charge line 90 to prevent cavitation.

The flushing valve 34 composed of a low-pressure selection valve communicates the low-pressure side of the flow paths 91a and 91b with the charge line 90 via the branch flow path 96a. When the amount of oil in the closed circuit including the boom cylinder 4 becomes surplus, the flushing valve 34 discharges the surplus to the charge line 90, and when the amount of oil is insufficient, the shortage is replenished from the charge line 90 to the closed circuit. By doing so, the balance of the amount of oil in the closed circuit is maintained.

The flushing valve 35 composed of a low-pressure selection valve communicates the low-pressure side of the flow paths 92a and 92b with the charge line 90 via the branch flow path 96b. When the amount of oil in the closed circuit including the arm cylinder 5 becomes surplus, the flushing valve 35 discharges the surplus to the charge line 90, and when the amount of oil is insufficient, the shortage is discharged from the charge line 90 to the closed circuit. By replenishing, the balance of the amount of oil in the closed circuit is maintained.

One input / output port 12a of the closed circuit pump 12 is connected to the charge line 90 via the branch flow path 97a, and the branch flow path 97a is provided with a control valve 70. One input / output port 14a of the closed circuit pump 14 is connected to the charge line 90 via the branch flow path 97b, and the branch flow path 97b is provided with a control valve 71. The opening degrees of the control valves 70 and 71 can be adjusted by a control signal from the controller 57.

An oil temperature sensor 80 is provided at the input / output port 12a of the closed circuit pump 12. The oil temperature sensor 80 converts the temperature of the hydraulic oil in the input / output port 12a into a temperature signal and outputs it to the controller 57. An oil temperature sensor 81 is provided at the input / output port 14a of the closed circuit pump 14. The oil temperature sensor 81 converts the temperature of the hydraulic oil in the input / output port 14a into a temperature signal and outputs it to the controller 57.

The tilt amount of the closed circuit pumps 12 and 14, the tilt amount of the open circuit pumps 13 and 15, and the opening degree of the flow rate control valves 64 and 65 are adjusted by the control signal from the controller 57. The switching valves 43a to 46b are at positions that shut off the flow path when no control signal is input from the controller 57 (communication position), and communicate with the flow path when a control signal is input from the controller 57 (communication position). Switch to position).

The boom operation lever 56a is an operation device for instructing the operation of the boom 1, is operated by an operator, and outputs an operation signal according to the operation direction and the operation amount to the controller 57. The arm operation lever 56d is an operation device for instructing the operation of the arm 2, is operated by an operator, and outputs an operation signal according to the operation direction and the operation amount to the controller 57.

The controller 57 has a normal mode control unit 57a that controls during normal operation and a warm-up mode control unit 57b that controls during initial warm-up operation. The controller 57 includes an arithmetic unit such as a CPU and a storage device such as a ROM and RAM, and by executing a program stored in the storage device, the functions of the normal mode control unit 57a and the warm-up mode control unit 57b can be performed. Realize.

The normal mode control unit 57a responds to operation signals input from the boom operation lever 56a and arm operation lever 56d, pressure signals input from pressure sensors (not shown) arranged in each unit, engine rotation speed signals, and the like. Various calculations are performed, and control signals are output to the closed circuit pumps 12, 14, the open circuit pumps 13, 15, the switching valves 43a to 46b, and the flow control valves 64, 65.

The warm-up mode control unit 57b performs various calculations according to the operation signals input from the boom operation lever 56a and the arm operation lever 56d, the temperature signals input from the oil temperature sensors 80 and 81, the engine rotation speed signal, and the like. A control signal is output to the closed circuit pumps 12, 14, the control valves 70, 71, and the charge relief valve 20.

Hereinafter, the processing of the normal mode control unit 57a will be specifically described.

First, processing when the boom operating lever 56a and the arm operating lever 56d are not operated will be described. The normal mode control unit 57a holds the switching valves 43a to 46b at the shutoff position. As a result, the boom cylinder 4 and the arm cylinder 5 are kept stationary. At the same time, the normal mode control unit 57a sets the tilt amount of the closed circuit pumps 12 and 14 to zero so that the discharge flow rate of the closed circuit pumps 12 and 14 becomes zero, and at the same time, the tilt amount of the open circuit pumps 13 and 15. Is minimized, the flow rate control valves 64 and 65 are opened, and the minimum discharge flow rate of the open circuit pumps 13 and 15 is returned to the tank 25. Thereby, the load of the closed circuit pumps 12 and 14 and the open circuit pumps 13 and 15 can be suppressed. At this time, since the hydraulic oil circulates between the open circuit pumps 13 and 15 and the tank 25, it is possible to warm the hydraulic oil by adjusting the opening degree of the flow control valves 64 and 65 to generate a pressure loss. However, since the discharge flow rates of the closed circuit pumps 12 and 14 are zero, the hydraulic oil does not circulate in the closed circuit. Therefore, the normal mode control unit 57a has a problem that when the hydraulic excavator 100 is started in a cold region or the like, the hydraulic oil in the closed circuit cannot be heated without moving the actuators 4 and 5. This problem is solved by the processing of the warm-up mode control unit 57b, which will be described later.

Next, processing when the boom operating lever 56a is operated in the boom raising direction will be described. The normal mode control unit 57a switches the switching valves 43a and 44a to communication positions, closes the flow rate control valve 64, and adjusts the tilt amounts of the closed circuit pump 12 and the open circuit pump 13 according to the lever operation amount. As a result, the discharged oil of the closed circuit pump 12 and the open circuit pump 13 flows into the bottom side oil chamber 4b of the boom cylinder 4, and the hydraulic oil discharged from the rod side oil chamber 4a is absorbed by the closed circuit pump 12. The boom cylinder 4 extends.

Next, processing when the boom operating lever 56a is operated in the boom lowering direction will be described. The normal mode control unit 57a switches the switching valves 43a and 44a to the communication position, minimizes the tilt amount of the open circuit pump 13, and adjusts the tilt amount of the closed circuit pump 12 and the flow rate control valve 64 according to the lever operation amount. Adjust the opening. As a result, the discharged oil of the closed circuit pump 12 flows into the rod side oil chamber 4a of the boom cylinder 4, and a part of the hydraulic oil discharged from the bottom side oil chamber 4b is absorbed by the closed circuit pump 12, and the rest. A part of the boom cylinder 4 is returned to the tank 25 via the flow control valve 64, and the boom cylinder 4 is retracted.

Next, the process when the arm operation lever 56d is operated in the arm cloud direction will be described. The normal mode control unit 57a switches the switching valves 45b and 46b to the communication position, closes the flow control valve 65, and adjusts the tilt amount of the closed circuit pump 14 and the open circuit pump 15 according to the lever operation amount. As a result, the discharged oil of the closed circuit pump 14 and the open circuit pump 15 flows into the bottom side oil chamber 5b of the arm cylinder 5, and the hydraulic oil discharged from the rod side oil chamber 5a is absorbed by the closed circuit pump 14. The arm cylinder 5 extends.

Next, processing when the arm operating lever 56d is operated in the arm dump direction will be described. The normal mode control unit 57a switches the switching valves 45b and 46b to the communication position, minimizes the tilt amount of the open circuit pump 15, and adjusts the tilt amount of the closed circuit pump 14 and the flow rate control valve 65 according to the lever operation amount. Adjust the opening. As a result, the discharged oil of the closed circuit pump 14 flows into the rod side oil chamber 5a of the arm cylinder 5, and a part of the hydraulic oil discharged from the bottom side oil chamber 5b is absorbed by the closed circuit pump 14, and the rest. A part is returned to the tank 25 via the flow control valve 65, and the arm cylinder 5 is retracted.

In the above operation example, the boom cylinder 4 is driven by the closed circuit pump 12 and the open circuit pump 13, and the arm cylinder 5 is driven by the closed circuit pump 14 and the open circuit pump 15. However, the actuator 4 The pump for driving, 5 can be appropriately changed by the switching valves 43a to 46b.

FIG. 3 is a flowchart showing the processing of the warm-up mode control unit 57b. The processing of the warm-up mode control unit 57b is executed in parallel with the processing of the normal mode control unit 57a described above. Hereinafter, each step will be described on the premise that the boom cylinder 4 is driven by the closed circuit pump 12.

The warm-up mode control unit 57b first determines whether or not the hydraulic oil temperature of the input / output port 12a of the closed circuit pump 12 is lower than a predetermined temperature (step S1). The predetermined temperature referred to here is set to, for example, the hydraulic oil temperature after idling the engine 9 for several minutes when starting a conventional hydraulic excavator in a cold region. If NO (the hydraulic oil temperature is equal to or higher than the predetermined temperature) is determined in step S1, the initial warm-up operation is completed, and the flow is terminated.

If YES (the hydraulic oil temperature is lower than the predetermined temperature) is determined in step S1, it is determined whether or not the boom operating lever 56a is neutral (step S2). If it is determined in step S2 that NO (the boom operating lever 56a is not neutral), the flow is terminated.

If it is determined in step S2 that YES (the boom operation lever 56a is neutral), the mode shifts to the operation mode (warm-up mode) in which the initial warm-up operation is performed, and the control valve 70 is opened (step S3).
Following step S3, the tilt of the closed circuit pump 12 is controlled so as to discharge hydraulic oil from the input / output port 12a of the closed circuit pump 12 (step S4). As a result, as shown in FIG. 4, the hydraulic oil discharged from the input / output port 12a of the closed circuit pump 12 is discharged to the tank 25 via the branch flow path 97a, the charge line 90, and the charge relief valve 20. The hydraulic oil discharged from the charge pump 11 to the charge line 90 is replenished to the other input / output port 12b of the closed circuit pump 12 via the check valve 30b. By circulating the hydraulic oil between the closed circuit pump 12 and the tank 25 via the charge line 90 in this way, the hydraulic oil in the tank 25 and in the vicinity of the closed circuit pump 12 can be warmed. At this time, the warm-up efficiency can be improved by reducing the opening degree of the control valve 70 to generate a pressure loss or increasing the discharge flow rate of the closed circuit pump 12 to increase the flow rate circulating in the closed circuit. It is possible.

Here, when the discharge flow rate of the closed circuit pump 12 is made larger than the discharge flow rate of the charge pump 11 in order to increase the flow rate circulating in the closed circuit, one of the discharge flow rates of the closed circuit pump 12 as shown in FIG. The portion is replenished in the closed circuit via the check valve 30b without being discharged to the tank 25. Here, as the flow rate passing through the check valve 30b increases, the pressure loss also increases due to the pressure override characteristic as shown in FIG. In other words, in order to increase the passing flow rate of the check valve 30b, it is necessary to increase the pressure loss generated by the check valve 30b. However, the pressure on the upstream side of the check valve 30b is maintained at a substantially constant pressure (charge pressure) by the charge relief valve 20, and the check valve 30 cannot generate a pressure loss higher than the charge pressure. As a result, the passing flow rate of the check valve 30b is limited to a constant flow rate according to the charge pressure, and the discharge flow rate of the closed circuit pump 12 cannot be increased beyond the constant flow rate. In order to solve this problem, the warm-up mode control unit 57b performs the following processing.

Following step S4, it is determined whether or not the discharge flow rate of the closed circuit pump 14 is larger than the predetermined flow rate (step S5). The predetermined flow rate referred to here is set to a value equal to or less than the flow rate that can pass through the check valve 30b. If NO (the discharge flow rate of the closed circuit pump 14 is equal to or less than a predetermined flow rate) is determined in step S5, the flow is terminated. If YES (the discharge flow rate of the closed circuit pump 14 is larger than the predetermined flow rate) is determined in step S1, a control signal is output to the charge relief valve 20 so that the relief setting is increased (step S2), and the flow is concerned. To finish. As a result, the pressure loss generated by the check valve 30b increases, and the flow rate that can pass through the check valve 30b increases.
(effect)
In this embodiment, the hydraulic actuator 4 (5), the operation lever 56a (56d) for instructing the operation of the hydraulic actuator 4 (5), and the closed circuit pump 12 (14) including the bi-tilt variable capacitance pump , The first flow path 91a connecting one oil chamber 4a (5a) of the hydraulic actuator 4 (5) and the first input / output port 12a (14a) which is one input / output port of the closed circuit pump 12 (14). (92a) is connected to the other oil chamber 4b (5b) of the hydraulic actuator 4 (5) and the second input / output port 12b (14b) which is the other input / output port of the closed circuit pump 12 (14). Two flow paths 91b (92b), a switching valve 43a (45b) capable of opening and closing the first flow path 91a (92a) and the second flow path 91b (92b), a tank 25 for storing hydraulic oil, and a tank 25. A charge pump 11 that sucks in and discharges hydraulic oil, a charge line 90 that is connected to the discharge port of the charge pump 11, and a first branch flow path 93 that connects the charge line 90 and the tank 25. The charge relief valve 20 that regulates the discharge pressure of the above is provided in the second branch flow path 94a (94b) that connects the charge line 90 with the first input / output port 12a (14a) and the second input / output port 12b (14b). The first check valves 30a, 30b (31a, 31b) that allow the flow of hydraulic oil from the charge line 90 to the first input / output ports 12a (14a) and the second input / output ports 12b (14b), and the operation lever. A controller 57 that opens and closes the switching valve 43a (45b) according to the presence or absence of operation of the 56a (56d) and controls the tilt of the closed circuit pump 12 (14) according to the operation amount of the operation lever 56a (56d). In the construction machine 100 provided, the third branch flow path 97a (97b) connecting the first input / output port 12a (14a) and the charge line 90, and the third branch flow path 97a according to the control signal from the controller 57. A control valve 70 (71) for opening and closing (97b) is provided, and the controller 57 is provided with a control valve 70 (71) when the operation lever 56a (56d) is not operated in the warm-up mode, which is an operation mode for warming the hydraulic oil of the tank 25. The tilt of the closed circuit pump 12 (14) is controlled so as to open (71) and discharge hydraulic oil from the first input / output port 12a (14a).

According to the present embodiment configured as described above, when the operating levers 56a and 56d are not operated, the hydraulic oil is circulated between the closed circuit pumps 12 and 14 and the tank 25 via the charge line 90. The hydraulic oil in the tank 25 and the closed circuit can be heated immediately after the engine is started. As a result, the construction machine 100 equipped with the hydraulic closing circuit system 200 in which the hydraulic actuators 4 and 5 are driven by the closing circuit pumps 12 and 14 can be efficiently warmed up in a cold region or the like.

It is desirable that the connection point on the closed circuit side of the branch flow path 97a (97b) be arranged as close as possible to the switching valves 43a, 43b (45a, 45b). As a result, the flow path through which the hydraulic oil circulates in the closed circuit becomes long, so that the warm-up efficiency of the closed circuit can be improved and the hydraulic oil temperature in the vicinity of the switching valves 43a, 43b (45a, 45b) rises. The warm-up effect of the switching valves 43a, 43b (45a, 45b) can be expected.

Further, the construction machine 100 according to the present embodiment is provided in the fourth branch flow path 95a (95b) connecting the charge line 90 with the first flow path 91a (92a) and the second flow path 91b (92b). Second check valves 37a, 37b (38a, 38b) that allow the flow of hydraulic oil from the charge line 90 to the first flow path 91a (92a) and the second flow path 91b (92b), and the charge line 90 and the first. The charge line 90, the first flow path 91a (92a), and the second flow path are provided in the fifth branch flow path 96a (96b) connecting the first flow path 91a (92a) and the second flow path 91b (92b). A flushing valve 34 (35) communicating with the low pressure side of the 91b (92b) is provided, and the connection points P2 (P5) and the fifth branch flow path 96a of the fourth branch flow path 95a (95b) are provided in the charge line 90. The connection point P3 (P6) of 96b) is arranged between the connection point P4 of the third branch flow path 97a (97b) and the connection point P1 of the first branch flow path 93.

With this configuration, the hydraulic oil discharged to the charge line 90 via the third branch flow path 97a (97b) in the warm-up mode is before being discharged to the tank 25 via the charge relief valve 20. , With the connection point P2 (P5) with the fourth branch flow path 95a (95b) leading to the check valves 37a, 37b (38a, 38b) and the fifth branch flow path 96a (96b) leading to the flushing valve 34 (35). Since it passes through the connection point P3 (P6), the hydraulic oil temperature near the connection points P2 and P3 (P5 and P6) of the charge line 90 rises. As a result, when driving the boom cylinder 4 (arm cylinder 5), warm hydraulic oil can flow into the closed circuit via the check valves 37a, 37b (38a, 38b) and the flushing valve 34 (35). Therefore, it is possible to quickly warm up the entire closed circuit.

Further, in the present embodiment, the charge relief valve 20 can adjust the relief set pressure according to the control signal from the controller 57, and the controller 57 is the discharge flow rate of the closed circuit pump 12 (14) in the warm-up mode. Increases the relief set pressure when the flow rate exceeds a predetermined value.

With this configuration, the pressure loss generated by the check valve 30b can be increased to increase the passing flow rate of the check valve. Therefore, the discharge flow rate of the closed circuit pump 12 (14) can be increased in the warm-up mode. By increasing the circulation flow rate of the hydraulic oil in the closed circuit, it is possible to improve the warm-up efficiency of the closed circuit.

Further, the construction machine 100 according to the present embodiment includes an oil temperature sensor 80 (81) that detects the temperature of the hydraulic oil of the first input / output port 12a (14a), and the controller 57 is an oil temperature sensor 80 (81). When the oil temperature detected in step 2 is lower than the predetermined temperature, the mode shifts to the warm-up mode.

With this configuration, when the hydraulic oil temperature is low, it is possible to shift to the warm-up mode without the intervention of an operator.

A second embodiment of the present invention will be described with reference to FIGS. 7 and 8.

FIG. 7 is a circuit diagram of the hydraulic closed circuit system 200 in this embodiment. In FIG. 7, the difference from the hydraulic closed circuit system 200 (shown in FIG. 2) in the first embodiment will be described.

The hydraulic closing circuit system 200 in this embodiment further includes a warm-up mode permission switch 58 and a monitor 59. The warm-up mode permission switch 58 is turned on / off by the operator to instruct the controller 57 whether or not to shift to the warm-up mode. The monitor 59 includes a touch panel and a speaker, outputs various information output from the controller 57 by image output or audio output, and inputs an instruction from the operator to the controller 57.

FIG. 8 is a flowchart showing the processing of the warm-up mode control unit 57b of the controller 57 in this embodiment. In FIG. 8, the difference from the process (shown in FIG. 3) of the warm-up mode control unit 57b in the first embodiment will be described.

The warm-up mode control unit 57b first determines whether or not an ON signal is input from the warm-up mode permission switch 58 (step S0). If it is determined in step S0 that YES (the ON signal is input from the warm-up mode permission switch 58), the process proceeds to step S1 and NO in step S0 (the ON signal is not input from the warm-up mode permission switch 58). If it is determined, the flow is terminated.

If NO (the hydraulic oil temperature is equal to or higher than the predetermined temperature) is determined in step S1, the operator is notified via the monitor 59 that the initial warm-up operation is completed (step S7), and the flow is terminated. do. As a result, the operator knows that the initial warm-up has been completed, returns the warm-up mode permission switch 58 to the OFF position, and then drives the boom cylinder 4 with the closed circuit pump 12 to warm up the entire closed circuit. I do.

If NO (the boom operating lever 56a is not neutral) is determined in step S2, a notification that the hydraulic oil in the closed circuit is low is notified via the monitor 59 (step S7), and the flow is terminated. As a result, the operator can carefully operate the lever after knowing that the hydraulic oil temperature in the closed circuit is low.
(effect)
The construction machine 100 according to the present embodiment includes a warm-up mode permission switch 58 capable of outputting a warm-up mode permission signal to the controller 57, and the controller 57 has a warm-up mode when the warm-up mode permission signal is not input. The transition to the warm-up mode is disabled, and the transition to the warm-up mode is possible when the warm-up mode permission signal is input.

In the present embodiment configured as described above, the same effect as that of the first embodiment can be achieved. Further, since the warm-up mode permission switch 58 can instruct the controller 57 whether or not to shift to the warm-up mode, it is possible to prevent the initial warm-up operation from being performed contrary to the operator's intention. Become.

Although the examples of the present invention have been described in detail above, the present invention is not limited to the above-mentioned examples, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations. It is also possible to add a part of the configuration of another embodiment to the configuration of one embodiment, delete a part of the configuration of one embodiment, or replace it with a part of another embodiment. It is possible.

1 ... Boom, 2 ... Arm, 3 ... Bucket, 4 ... Boom cylinder (hydraulic actuator), 4a ... Rod side oil chamber, 4b ... Bottom side oil chamber, 5 ... Arm cylinder (hydraulic actuator), 5a ... Rod side oil chamber 5, 5b ... Bottom side oil chamber, 6 ... Bucket cylinder (flood actuator), 9 ... Engine, 10 ... Power transmission device, 11 ... Charge pump, 12, 14 ... Closed circuit pump, 12a, 14a ... Input / output port (1st) Input / output port), 12b, 14b ... Input / output port (second input / output port), 13, 15 ... Open circuit pump, 20 ... Charge relief valve, 25 ... Tank, 30a, 30b, 31a, 31b ... Check valve (No. 1) 1 check valve), 37a, 37b, 38a, 38b ... Check valve (second check valve), 34, 35 ... Flushing valve, 43a, 43b, 44a, 44b, 45a, 45b, 46a, 46b ... Switching valve, 56a ... Boom operation lever, 56d ... Arm operation lever, 57 ... Controller, 58 ... Warm-up mode permission switch, 59 ... Monitor, 64, 65 ... Flow control valve, 70, 71 ... Control valve, 80, 81 ... Oil temperature sensor, 90 ... Charge line, 91a, 92a ... Flow path (first flow path), 91b, 92b ... Flow path (second flow path), 93 ... Branch flow path (first branch flow path), 94a, 94b ... Branch flow Road (second branch flow path), 95a, 95b ... branch flow path (fourth branch flow path), 96a, 96b ... branch flow path (fifth branch flow path), 97a, 97b ... branch flow path (third branch flow path) Flow path), 100 ... Hydraulic excavator (construction machine), 101 ... Lower traveling body, 102 ... Upper swivel body, 103 ... Front device, 200 ... Hydraulic closed circuit system, P1 to P7 ... Connection points.

Claims (5)

With hydraulic actuator,
An operation lever for instructing the operation of the hydraulic actuator and
A closed circuit pump consisting of a double tilt variable displacement pump,
A first flow path connecting one oil chamber of the hydraulic actuator and a first input / output port which is one input / output port of the closed circuit pump,
A second flow path connecting the other oil chamber of the hydraulic actuator and the second input / output port which is the other input / output port of the closed circuit pump.
A switching valve capable of opening and closing the first flow path and the second flow path,
A tank for storing hydraulic oil and
A charge pump that sucks in and discharges the hydraulic oil from the tank,
The charge line connected to the discharge port of the charge pump and
A charge relief valve provided in the first branch flow path connecting the charge line and the tank to regulate the discharge pressure of the charge pump, and a charge relief valve.
It is provided in the second branch flow path connecting the charge line, the first input / output port, and the second input / output port, and operates from the charge line to the first input / output port and the second input / output port. The first check valve that allows the flow of oil and
In a construction machine provided with a controller that opens and closes the switching valve according to the presence or absence of operation of the operation lever and controls the tilt of the closed circuit pump according to the operation amount of the operation lever.
A third branch flow path connecting the first input / output port and the charge line,
A control valve capable of adjusting the opening of the third branch flow path according to a control signal from the controller is provided.
In the warm-up mode, which is an operation mode for warming the hydraulic oil of the tank, the controller opens the control valve and discharges the hydraulic oil from the first input / output port when the operation lever is not operated. A construction machine characterized by controlling the tilt of a closed circuit pump. In the construction machine according to claim 1,
A fourth branch flow path that connects the charge line to the first flow path and the second flow path is provided to allow the flow of hydraulic oil from the charge line to the first flow path and the second flow path. Allowable second check valve and
It is provided in a fifth branch flow path connecting the charge line with the first flow path and the second flow path, and communicates the charge line with the low pressure side of the first flow path and the second flow path. Equipped with a flushing valve
In the charge line, the connection point of the fourth branch flow path and the connection point of the fifth branch flow path are arranged between the connection point of the third branch flow path and the connection point of the first branch flow path. Construction machinery characterized by being. In the construction machine according to claim 1,
The charge relief valve can adjust the relief set pressure according to the control signal from the controller.
The controller is a construction machine characterized in that, in the warm-up mode, the relief set pressure is increased when the discharge flow rate of the closed circuit pump exceeds a predetermined flow rate. In the construction machine according to claim 1,
An oil temperature sensor for detecting the temperature of the hydraulic oil of the first input / output port is provided.
The controller is a construction machine characterized in that when the oil temperature detected by the oil temperature sensor is lower than a predetermined temperature, the controller shifts to the warm-up mode. In the construction machine according to claim 1,
The controller is provided with a warm-up mode permission switch capable of outputting a warm-up mode permission signal.
The controller cannot shift to the warm-up mode when the warm-up mode permission signal is not input, and can shift to the warm-up mode when the warm-up mode permit signal is input. A construction machine characterized by being.

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