JP7208054B2 - construction machinery - Google Patents

Description

The present invention relates to construction machines such as hydraulic excavators.

In the field of construction machinery such as hydraulic excavators, working machines using hydraulic circuits (hereinafter referred to as "open circuits") that return oil from hydraulic actuators such as hydraulic cylinders to hydraulic oil tanks are the mainstream. , In order to reduce fuel consumption, the number of hydraulic cylinders (hereinafter referred to as "cylinders") or throttle elements in the hydraulic circuit between the pump and the hydraulic motor is reduced, and the return oil from the cylinders or hydraulic motors is transferred to the double tilting pump (hereinafter referred to as the "cylinder"). , called "pump"), and the development of a circuit (hereinafter called "closed circuit") in which a pump and a cylinder or a pump and a hydraulic motor are connected in a closed circuit state is being developed. A hydraulic circuit having an open circuit and a closed circuit has also been proposed. As a prior art document of a hydraulic excavator equipped with a hydraulic closed circuit, there is Patent Document 1.

Patent Document 1 discloses at least one closed-circuit hydraulic fluid inflow/outflow control unit having two inflow/outflow ports that allow hydraulic fluid to flow in and out in both directions, and at least a first hydraulic fluid chamber and a second hydraulic fluid chamber. a single-rod hydraulic cylinder, and two inflow/outflow ports of the hydraulic fluid inflow/outflow control unit for closed circuit are connected to the first hydraulic fluid chamber and the second hydraulic fluid chamber in a closed circuit fashion. At least one open circuit hydraulic fluid inflow/outflow control unit having a closed circuit, an inflow port for inflowing hydraulic fluid from a hydraulic fluid tank and an outflow port for outflowing hydraulic fluid, and outflow from the open circuit hydraulic fluid inflow/outflow control unit a plurality of open circuits including an open circuit switching unit for switching the supply destination of the hydraulic oil to be supplied, the closed circuit hydraulic oil inflow/outflow control unit, the open circuit hydraulic oil inflow/outflow control unit, and the open circuit switching unit and a controller for controlling a hydraulic oil outflow side of at least one of the open circuit switching units of the plurality of open circuits; A drive for a working machine is disclosed, characterized in that it comprises a connecting line connected to either.

JP 2015-48899 A

In Patent Document 1, a closed circuit pump and an open circuit pump are arranged in pairs. When the closed-circuit pump supplies hydraulic fluid to the cap side of the hydraulic cylinder, the open-circuit pump compensates for the shortage of hydraulic fluid due to the pressure receiving area difference of the hydraulic cylinder. When hydraulic oil is supplied to the rod side of the hydraulic cylinder, the hydraulic oil discharged from the cap side of the hydraulic cylinder is discharged from the bleed-off valve arranged in the open circuit line, thereby balancing the hydraulic oil in the circuit. are balancing. Further, by arranging a plurality of closed circuit pumps and open circuit pumps and switching each switching valve in the circuit, hydraulic oil can be supplied to a plurality of actuators. On the other hand, when operating in a low-temperature environment, the responsiveness of the switching valve and the bleed-off valve deteriorates, and if the opening/closing timing of each valve deviates, hydraulic fluid flows out from the hydraulic cylinder, causing unintended operation. It may get lost.

The present invention has been made in view of the above-mentioned problems, and its object is to install a hydraulic system in which a closed circuit pump and an open circuit pump are arranged in pairs, and when the responsiveness of the switching valve deteriorates in a low temperature environment. However, it is to provide a construction machine that operates stably.

In order to achieve the above object, the present invention provides a tank for storing hydraulic oil, a single-rod hydraulic cylinder having a cap chamber and a rod chamber, and a dual tilting pump connected to the hydraulic cylinder in a closed circuit. an open-circuit pump consisting of a uni-tilting pump; a cap-side switching valve for switching between flow and shut-off of a flow path connecting the discharge port of the open-circuit pump and the cap chamber; A proportional valve provided in the flow path connecting the discharge port of the circuit pump and the tank and capable of adjusting the opening area from zero to a predetermined maximum opening area, and instructing the driving direction and driving speed of the hydraulic cylinder. and an operating device for operating the operating device with the cap-side switching valve open and the proportional valve closed when the driving direction of the hydraulic cylinder instructed via the operating device is the extension direction. and controls the discharge flow rate of the closed circuit pump and the open circuit pump according to the operation amount of the cap side switching valve when the driving direction of the hydraulic cylinder instructed via the operating device is the contraction direction A construction machine comprising a controller for controlling the discharge flow rate of the closed circuit pump and the opening area of the proportional valve according to the operation amount of the operating device in an open state, the temperature detecting the temperature of the hydraulic oil. A sensor is provided, and when the temperature of the hydraulic oil detected by the temperature sensor is lower than a predetermined temperature, the controller closes the cap-side switching valve according to the operating direction of the operating device. The discharge direction of the closed circuit pump is controlled, and the discharge flow rate of the closed circuit pump is controlled according to the operation amount of the operating device.

According to the present invention configured as described above, in a hydraulic closed circuit system in which a hydraulic cylinder is driven by a closed circuit pump and an open circuit pump, the cap-side switching valve is closed when the oil temperature is lower than the threshold value. Since the hydraulic cylinder is driven only by the closed circuit pump, it is possible to prevent unintended operation of the hydraulic cylinder due to the response delay of the cap-side switching valve in a low temperature environment.

According to the present invention, it is possible to stably operate a construction machine equipped with a hydraulic system in which a closed-circuit pump and an open-circuit pump are arranged in a pair, even when the responsiveness of the switching valve deteriorates in a low-temperature environment. Become.

1 is a side view of a hydraulic excavator according to a first embodiment of the present invention; FIG. 2 is a schematic configuration diagram of a hydraulic system mounted on the hydraulic excavator shown in FIG. 1; FIG. 3 is a diagram showing functional blocks of the controller shown in FIG. 2; FIG. 3 is a diagram showing a control flow of the controller shown in FIG. 2; FIG. FIG. 2 is a viscosity-temperature characteristic diagram of hydraulic oil; FIG. 5 is a diagram showing an operation result when the control of FIG. 4 is executed (normal mode) while the oil temperature is higher than the threshold; FIG. 5 is a diagram showing an operation result when the control of FIG. 4 is not executed while the oil temperature is lower than the threshold; FIG. 5 is a diagram showing an operation result when the control of FIG. 4 is executed in a state where the oil temperature is equal to or lower than the threshold (warm-up mode); FIG. 5 is a schematic configuration diagram of a hydraulic system according to a second embodiment of the present invention; FIG. 8 is a diagram (1/3) showing a control flow of the controller shown in FIG. 7; FIG. 8 is a diagram (2/3) showing a control flow of the controller shown in FIG. 7; FIG. 8 is a diagram (3/3) showing a control flow of the controller shown in FIG. 7; FIG. 8C is a diagram showing an operation result when the control of FIGS. 8A to 8C is executed (normal mode) while the oil temperature is higher than the threshold; FIG. 8B is a diagram showing an operation result when the control of FIGS. 8A to 8C is not executed while the oil temperature is lower than the threshold; FIG. 8C is a diagram showing the operation result when the control of FIGS. 8A to 8C is executed in a state where the oil temperature is equal to or lower than the threshold (warm-up mode);

Hereinafter, a hydraulic excavator will be described as an example of a construction machine according to an embodiment of the present invention with reference to the drawings. In addition, in each figure, the same code|symbol is attached|subjected to the same member, and the overlapping description is abbreviate|omitted suitably.

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

In FIG. 1, a hydraulic excavator 100 includes a lower running body 103 having crawler-type traveling devices 8 on both sides in the left-right direction, and an upper revolving body 102 rotatably mounted on the lower running body 103. . The upper swing body 102 is driven by a swing motor 7 which is a hydraulic motor.

A front work machine 104 for performing excavation work, for example, is attached to the front side of the upper revolving body 102 . The front working machine 104 includes a boom 2 that is connected to the front side of an upper revolving body 102 that constitutes the vehicle body so as to be able to turn vertically, and an arm that is connected to the tip of the boom 2 so that it can turn vertically and back and forth. 4 and a bucket 6 connected to the tip of the arm 4 so as to be rotatable in the vertical and longitudinal directions. The boom 2, arm 4, and bucket 6 are driven by boom cylinder 1, arm cylinder 3, and bucket cylinder 5, which are single-rod hydraulic cylinders, respectively.

A cab 101 on which an operator rides is provided on the upper revolving body 102 . A lever 41 (shown in FIG. 2) for operating the boom 2, the arm 4, the bucket 6 and the upper rotating body 102 is arranged in the cab 101. As shown in FIG.

FIG. 2 is a schematic configuration diagram of a hydraulic system mounted on the hydraulic excavator 100. As shown in FIG. Note that FIG. 2 shows only the parts related to the driving of the boom cylinder 1 and the arm cylinder 3, and omits the parts related to the driving of the other actuators.

An engine 9 as a power source is connected to a power transmission device 10 that distributes power. A charge pump 11 , a closed circuit pump 12 and an open circuit pump 14 are connected to the power transmission device 10 .

The closed circuit pump 12 includes a dual tilt swash plate mechanism having a pair of input/output ports, and a regulator 13 for adjusting the tilt angles of the dual tilt swash plates. The regulator 13 adjusts the tilting angles of both tilting swash plates of the closed circuit pump 12 based on a signal from the controller 40 . The closed circuit pump 12 can control the discharge direction and flow rate of hydraulic oil from the pair of input/output ports by adjusting the tilt angle of the tilt swash plate. The closed circuit pump 12 also functions as a hydraulic motor when supplied with pressure oil.

The open circuit pump 14 includes a unilateral swash plate mechanism having a discharge port and a suction port, and a regulator 15 for adjusting the inclination angle of the unilateral swash plate. The regulator 15 adjusts the tilting angle of the single tilting swash plate of the open circuit pump 14 according to a signal from the controller 40 . The open circuit pump 14 can control the discharge flow rate of the hydraulic oil from the discharge port by adjusting the tilt angle of the uni-tilt swash plate.

The charge pump 11 supplies pressure oil to a flow path 212 as a charge line.

Flow paths 200 and 201 are connected to a pair of input/output ports of the closed circuit pump 12 , and a switching valve 20 is connected to the flow paths 200 and 201 . The switching valve 20 switches between communication and blocking of the flow path according to a signal from the controller 40 . When there is no signal from the controller 40, the switching valve 20 is closed.

The switching valve 20 is connected to the cap chamber 1 a of the boom cylinder 1 via a flow path 210 and connected to the rod chamber 1 b of the boom cylinder 1 via a flow path 211 . When the switching valve 20 is brought into communication by a signal from the controller 40, the closed circuit pump 12 is connected to the boom cylinder 1 via the flow paths 200 and 201, the switching valve 20, and the flow paths 210 and 211, thereby opening the closed circuit. Constitute.

A suction port of the open circuit pump 14 is connected to the tank 33 . A discharge port of the open circuit pump 14 is connected to the switching valve 21 and the relief valve 25 via the flow path 202 . A proportional valve 22 is provided in the flow path 203 that connects the discharge port of the open circuit pump 14 to the tank 33 .

The relief valve 25 releases hydraulic oil to the tank 33 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

The switching valve 21 switches between communication and blocking of the flow path according to a signal from the controller 40 . When there is no signal from the controller 40, the switching valve 21 is closed.

The switching valve 21 is connected to the cap chamber 1 a of the boom cylinder 1 via flow paths 204 and 210 .

The proportional valve 22 changes its opening area according to a signal from the controller 40 to control the flow rate. In the absence of a signal from controller 40, proportional valve 22 is held at its maximum open area. When the switching valve 21 is in the closed state, the controller 40 controls the discharge flow rate of the open circuit pump 14 to the minimum discharge flow rate, and operates the proportional valve 22 so that this minimum discharge flow rate of hydraulic fluid is discharged to the tank 33. Open slightly.

A suction port of the charge pump 11 is connected to the tank 33 . A discharge port of the charge pump 11 is connected to a charge relief valve 28 and charge check valves 30 and 31 via a charge line 212 .

The charge relief valve 28 sets the charge pressure of the charge check valves 30 and 31 .

The charge check valves 30 and 31 open when the pressure in the flow paths 210 and 211 falls below the charge pressure, and replenish the flow paths 210 and 211 with pressure oil from the charge line 212 .

The charge check valve 32 opens when the pressure in the flow paths 200 and 201 falls below the tank pressure, and replenishes the flow paths 200 and 201 with hydraulic oil from the charge line 212 .

Relief valves 23 and 24 provided in flow paths 200 and 201 release hydraulic oil to tank 33 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

The boom cylinder 1 is a single-rod hydraulic cylinder that expands and contracts when supplied with hydraulic oil. The expansion and contraction direction of the boom cylinder 1 depends on the supply direction of hydraulic oil.

Relief valves 26 and 27 provided in flow paths 210 and 211 release hydraulic fluid to charge line 212 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

Flushing valves 29 provided in flow paths 210 and 211 discharge surplus oil in the flow paths to charge line 212 .

The lever 41 inputs the amount of lever operation by the operator to the controller 40 .

The temperature sensor 42 measures the temperature of hydraulic oil in the hydraulic circuit (hereinafter referred to as oil temperature) and inputs it to the controller 40 . Although the installation position of the temperature sensor 42 is not particularly limited, in this embodiment, it is installed in the tank 33 where the oil temperature is considered to be the lowest.

FIG. 3 shows functional blocks of the controller 40. As shown in FIG. The controller 40 includes an operation mode determination section 40a, a pump allocation calculation section 40b, a pump signal output section 40c, a switching valve signal output section 40d, and a proportional valve signal output section 40e.

The operation mode determination unit 40a determines the operation mode (normal mode or warm-up mode) based on information from the temperature sensor 42, and inputs a control signal according to the determination result to the pump allocation calculation unit 40b.

The pump allocation calculation unit 40b allocates the closed circuit pump 12 and the open circuit pump 14 to the actuators to be driven based on the input of the lever 41 and the information from the operation mode determination unit 40a, and outputs a control signal according to the allocation result. is input to the pump signal output section 40c. At the same time, a control signal for forming a flow path for driving each actuator is input to the switching valve signal output section 40d and the proportional valve signal output section 40e.

The pump signal output section 40c outputs signals to the regulators 13 and 15 based on the control signal from the pump allocation calculation section 40b.

The switching valve signal output unit 40d outputs signals to the switching valves 20 and 21 based on the control signal from the pump allocation calculation unit 40b.

The proportional valve signal output section 40e outputs a control signal to the proportional valve 22 based on the control signal from the pump allocation calculation section 40b.

FIG. 4 shows the control flow of the controller 40. As shown in FIG.

The controller 40 first detects the oil temperature T of the tank 33 with the temperature sensor 42 in step S101. In subsequent step S102, it is determined whether or not the oil temperature T is lower than a predetermined threshold value T1. The threshold T1 will be described later.

If it is determined in step S102 that the oil temperature T is lower than the threshold value T1 (YES), the operation mode of the hydraulic excavator 100 is set to warm-up mode in step S103, and the process proceeds to step S104.

In step S104, the tilting angle of the closed circuit pump 12 is controlled according to the lever operation amount, and the switching valve 20 is opened. In subsequent step S105, the tilting angle of the open circuit pump 14 is controlled to the minimum tilting angle, the proportional valve 22 is slightly opened, the switching valve 21 is closed, and the flow ends. As a result, when the oil temperature T is lower than the threshold value T1, the boom cylinder 1 is driven only by the closed circuit pump 12 . As a result, the hydraulic oil of the boom cylinder 1 does not flow out to the tank 33 via the proportional valve 22 due to the response delay of the switching valve 21, so that the unintended operation of the boom cylinder 1 can be prevented.

If it is determined in step S102 that the oil temperature T is equal to or higher than the threshold value T1 (NO), it is determined in step S106 whether or not there is an instruction from the operator to shift to the normal mode. Here, the mode shift instruction is made through input means such as the switch 43 (shown in FIG. 2) arranged in the cab 101 .

If it is determined in step S106 that there is an instruction to shift to the normal mode (YES), the operation mode is set to the normal mode in step S107. On the other hand, if it is determined that there is no instruction to shift to the normal mode (NO), the process proceeds to step S104. As a result, switching from the warm-up mode to the normal mode is not executed without the operator's permission, so that the operation feeling of the boom cylinder 1 can be prevented from changing unintentionally.

Following step S107, it is determined in step S108 whether or not the lever operation is the cylinder extension operation.

If it is determined that the lever operation is the cylinder extension operation (YES) in step S108, the tilting angle of the closed circuit pump 12 is controlled according to the lever operation amount to open the switching valve 20 in step S109. In subsequent step S110, the tilting angle of the open circuit pump 14 is controlled according to the lever operation amount, the proportional valve 22 is closed, the switching valve 21 is opened, and the flow ends. As a result, the oil discharged from the closed circuit pump 12 and the open circuit pump 14 is supplied to the cap chamber 1a of the boom cylinder 1, and the closed circuit pump 12 absorbs the oil discharged from the rod chamber 1b.

If it is determined in step S108 that the lever operation is not the cylinder extension operation (NO), in step S111, the tilting angle of the closed circuit pump 12 is controlled according to the lever operation amount, and the switching valve 20 is opened. In subsequent step S112, the tilting angle of the open circuit pump 14 is controlled to the minimum tilting angle, the proportional valve 22 is closed according to the lever operation amount, the switching valve 21 is opened, and the flow ends. As a result, the oil discharged from the closed circuit pump 12 is supplied to the rod chamber of the boom cylinder 1, part of the oil discharged from the cap chamber 1a is absorbed by the closed circuit pump 12, and the remaining part is is discharged into the tank 33.

FIG. 5 is a viscosity-temperature characteristic diagram of hydraulic oil, showing the relationship between viscosity and temperature of a general hydraulic oil. Hydraulic oil becomes more viscous as the temperature drops. As the viscosity increases, the responsiveness of hydraulic equipment decreases. In this embodiment, the temperature threshold is temperature T1 (for example, 10° C. to 30° C.) at which the viscosity of the hydraulic oil becomes sufficiently small. The temperature threshold value T1 is a value that can be arbitrarily set, and is set according to the responsiveness of the valve so that the influence on the operation of the hydraulic actuator such as the boom cylinder 1 is reduced.

Next, the operation when the control of FIG. 4 is executed and the operation when it is not executed will be described.

FIG. 6A shows the operation results when the control in FIG. 4 is executed (normal mode) with the oil temperature higher than the threshold T1. 20, the discharge flow rate of the open circuit pump 14, the opening of the switching valve 21, and the opening of the proportional valve 22.

At time t1, lever operation for raising the boom is started. Accordingly, the discharge flow rate of the closed circuit pump 12 increases. In order to form a flow path between the closed circuit pump 12 and the boom cylinder 1, the switching valve 20 is opened. Further, since the hydraulic cylinder is extended, the discharge flow rate of the open circuit pump 14 also increases. In order to form a flow path between the open circuit pump 14 and the boom cylinder 1, the switching valve 21 is opened. Proportional valve 22 is closed to prevent hydraulic fluid from flowing out of the circuit.

At time t2, the lever operation for raising the boom ends. Accordingly, the discharge flow rate of the closed circuit pump 12 becomes zero. The discharge flow rate of the open circuit pump 14 becomes the minimum discharge flow rate, and the switching valves 20 and 21 provided between each pump and the boom cylinder 1 are closed. Proportional valve 22 opens to expel hydraulic fluid for the minimum displacement of open circuit pump 14 .

At time t3, the boom lowering lever operation is started. Accordingly, the discharge flow rate of the closed circuit pump 12 increases. In order to form a flow path between the closed circuit pump 12 and the boom cylinder 1, the switching valve 20 is opened. Further, since this is a cylinder retraction operation, the proportional valve 22 is opened, and the switching valve 21 is opened to form a flow path between the proportional valve 22 and the boom cylinder 1 . As a result, hydraulic oil from the cap chamber 1 a of the boom cylinder 1 is discharged to the tank 33 .

At time t4, the lever operation for lowering the boom ends. Accordingly, the discharge flow rate of the closed circuit pump 12 becomes zero. The discharge flow rate of the open circuit pump 14 becomes the minimum discharge flow rate, and the switching valves 20 and 21 provided between each pump and the boom cylinder 1 are closed. The proportional valve 22 remains open to expel the minimum displacement of the open circuit pump 14 .

FIG. 6B shows the operation result when the control of FIG. 4 is not executed while the oil temperature is lower than the threshold value T1.

At time t1, lever operation for raising the boom is started. Accordingly, the discharge flow rate of the closed circuit pump 12 increases. In order to form a flow path between the closed circuit pump 12 and the boom cylinder 1, the switching valve 20 is opened. In addition, the discharge flow rate of the open circuit pump 14 also increases because of the cylinder extension operation. In order to form a flow path between the open circuit pump 14 and the boom cylinder 1, the switching valve 21 is opened. At this time, the hydraulic oil in the hydraulic circuit has a low temperature and a high viscosity. Therefore, the responsiveness of the switching valves 20 and 21 is poor, and the behavior becomes slower than after the end of warm-up. Proportional valve 22 is closed to prevent hydraulic fluid from flowing out of the circuit.

At time t2, the lever operation for raising the boom ends. Accordingly, the discharge flow rate of the closed circuit pump 12 becomes zero. The discharge flow rate of the open circuit pump 14 becomes the minimum discharge flow rate, and the switching valves 20 and 21 provided between each pump and the boom cylinder 1 are closed. Proportional valve 22 opens to expel hydraulic fluid for the minimum displacement of open circuit pump 14 . Since the oil temperature is low, the responsiveness of the switching valves 20 and 21 is poor, and the behavior becomes slow with respect to the required degree of opening. At time t2, the proportional valve 22 is also opened. That is, a phenomenon occurs in which the proportional valve 22 is opened while the switching valve 21 is not closed. At this time, since the cap chamber 1a of the boom cylinder 1 and the tank 33 are in communication with each other, hydraulic oil flows out from the cap chamber 1a of the boom cylinder 1, the stroke of the boom cylinder 1 decreases, and the boom 2 moves unintended. will do.

At time t3, the boom lowering lever operation is started. Accordingly, the discharge flow rate of the closed circuit pump 12 increases. In order to form a flow path between the closed circuit pump 12 and the boom cylinder 1, the switching valve 20 is opened. Further, since this is a cylinder retraction operation, the proportional valve 22 is opened, and the switching valve 21 is opened to form a flow path between the proportional valve 22 and the boom cylinder 1 . As a result, hydraulic oil from the cap chamber 1 a of the boom cylinder 1 is discharged to the tank 33 . Since the oil temperature is still low at time t3, the responsiveness of the switching valves 20 and 21 is lowered, and the behavior becomes slower than after the end of warming up.

At time t4, the operation of the lever 41 ends. Accordingly, the discharge flow rate of the closed circuit pump 12 becomes zero. The discharge flow rate of the open circuit pump 14 becomes the minimum discharge flow rate, and the switching valves 20 and 21 provided between each pump and the boom cylinder 1 are closed. The proportional valve 22 remains open to expel the minimum displacement of the open circuit pump 14 . Since the oil temperature is still low at time t4, the responsiveness of the switching valves 20 and 21 is reduced, and the behavior of the switching valves 20 and 21 becomes slower than after the end of warming up.

FIG. 6C shows the operation result when the control of FIG. 4 is executed while the oil temperature is lower than the threshold (warm-up mode).

At time t1, lever operation for raising the boom is started. The oil temperature at this time is lower than the threshold value T1. The discharge flow rate of the closed circuit pump 12 increases according to the amount of operation of the lever 41 . In the normal extension operation of the hydraulic cylinder, the switching valve 21 is opened in order to consider the flow rate of the pressure receiving area difference, and the hydraulic oil is also discharged from the open circuit pump 14, but since the oil temperature is lower than the threshold value T1, The tilting angle of the circuit pump 14 is maintained at the minimum tilting angle, and the switching valve 21 is closed. The proportional valve 22 is open and discharges the minimum discharge flow rate of the open circuit pump 14 to the tank 33 .

At time t2, the lever operation for raising the boom ends. With the end of the operation of the lever 41, the discharge flow rate of the closed circuit pump 12 also becomes zero. Although the oil temperature rises between times t1 and t2, it does not reach the threshold value T1.

At time t3, the lever operation for raising the boom is started again, and the discharge flow rate of the closed circuit pump 12 increases.

In the normal contraction operation of the hydraulic cylinder 1, the switching valve 21 is opened and the hydraulic oil is discharged from the proportional valve 22 to the tank 33 in order to consider the flow rate of the pressure receiving area difference. , the switching valve 21 is closed and the proportional valve 22 is open to discharge the minimum discharge flow of the open circuit pump 14 to the tank 33 .

At time t4, the lever operation for lowering the boom ends. As the operation of the lever 41 ends, the discharge flow rate of the closed circuit pump 12 decreases. Between times t3 and t4, the oil temperature rises and exceeds the threshold value T1.

At time t5, the lever operation for raising the boom is started again, and the discharge flow rate of the closed circuit pump 12 increases. Unlike at time t1, the oil temperature has risen to threshold T1. Therefore, at the same time as the closed circuit pump 12 discharges hydraulic oil, the open circuit pump 14 also discharges hydraulic oil. Accordingly, the switching valve 21 is opened and the proportional valve 22 is closed.

At time t6, the lever operation for raising the boom ends. The discharge flow rate of the closed circuit pump 12 becomes 0, and the discharge flow rate of the open circuit pump 14 becomes the minimum discharge flow rate. The switching valves 20 and 21 are closed to block the flow path. Proportional valve 22 opens to discharge the minimum discharge flow of open circuit pump 14 to tank 33 .

In this embodiment, a closed hydraulic cylinder 1 comprising a tank 33 for storing hydraulic oil, a single-rod hydraulic cylinder 1 having a cap chamber 1a and a rod chamber 1b, and a double tilting pump connected to the hydraulic cylinder 1 in a closed circuit. a circuit pump 12, an open circuit pump 14 consisting of a uni-tilting pump, a cap-side switching valve 21 for switching between flow and shutoff of a flow path 204 connecting the discharge port of the open circuit pump 14 and the cap chamber 1a, A proportional valve 22 provided in a flow path 203 connecting the discharge port of the circuit pump 14 and the tank 33 and capable of adjusting the opening area from zero to a predetermined maximum opening area; When the operation device 41 for instructing the speed and the driving direction of the hydraulic cylinder 1 instructed via the operation device 41 is the extension direction, the cap side switching valve 21 is opened and the proportional valve 22 is closed. , the discharge flow rate of the closed circuit pump 12 and the open circuit pump 14 is controlled according to the operation amount of the operation device 41, and when the driving direction of the hydraulic cylinder 1 instructed via the operation device 41 is the contraction direction, the cap In the construction machine 100 including a controller 40 for controlling the discharge flow rate of the closed circuit pump 12 and the opening area of the proportional valve 22 according to the operation amount of the operation device 41 with the side switching valve 21 opened, the hydraulic oil The controller 40 closes the cap-side switching valve 21 when the temperature T of the hydraulic oil detected by the temperature sensor 42 is lower than a predetermined temperature T1. , the discharge direction of the closed circuit pump 12 is controlled according to the operating direction of the operating device 41 , and the discharge flow rate of the closed circuit pump 12 is controlled according to the operation amount of the operating device 41 .

According to this embodiment configured as described above, in the hydraulic closed circuit system in which the hydraulic cylinder 1 is driven by the closed circuit pump 12 and the open circuit pump 14, when the oil temperature is lower than the threshold value T1, the cap side switching valve 21 is maintained in the closed state and the hydraulic cylinder 1 is driven only by the closed circuit pump 12, it is possible to prevent unintended operation of the hydraulic cylinder 1 due to a response delay of the cap-side switching valve 21 in a low temperature environment. It becomes possible.

Also, in this embodiment, the temperature sensor 42 is provided in the tank 33 where the oil temperature is considered to be the lowest. This makes it possible to reliably determine the end of warm-up.

A hydraulic excavator according to a second embodiment of the present invention will be described with a focus on differences from the first embodiment.

FIG. 7 is a schematic configuration diagram of the hydraulic system in this embodiment. Note that FIG. 7 shows only the parts related to the driving of the boom cylinder 1 and the arm cylinder 3, and omits the parts related to the driving of the other actuators.

An engine 9 as 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 12a and 12b, and open circuit pumps 14a and 14b.

The closed circuit pumps 12a and 12b are provided with a dual tilt swash plate mechanism having a pair of input/output ports, and regulators 13a and 13b for adjusting the tilt angles of the dual tilt swash plates. The regulators 13a, 13b adjust the tilting angles of both tilting swash plates of the closed circuit pumps 12a, 12b according to signals from the controller 40A. The closed circuit pumps 12a and 12b can control the discharge direction and discharge flow rate of the hydraulic oil from the pair of input/output ports by adjusting the tilt angles of the tilt swash plates. The closed circuit pumps 12a and 12b also function as hydraulic motors when supplied with pressure oil.

The open circuit pumps 14a and 14b are provided with a single tilt swash plate mechanism having a discharge port and a suction port, and regulators 15a and 15b for adjusting the tilt angle of the single tilt swash plate. The regulators 15a, 15b adjust the tilt angles of the unilateral tilting swash plates of the open circuit pumps 14a, 14b according to signals from the controller 40A. The open circuit pumps 14a and 14b can control the discharge flow rate of the hydraulic oil from the discharge port by adjusting the tilting angle of the single tilting swash plate.

The charge pump 11 supplies pressure oil to a flow path 340 as a charge line.

Flow paths 300 and 301 are connected to a pair of input/output ports of the closed circuit pump 12a, and switching valves 20a and 20b are connected to the flow paths 300 and 301, respectively. The switching valves 20a and 20b switch between communication and blocking of the flow path according to a signal from the controller 40A. When there is no signal from the controller 40A, the switching valves 20a and 20b are closed.

The switching valve 20 a is connected to the cap chamber 1 a of the boom cylinder 1 via flow paths 310 and 336 and connected to the rod chamber 1 b of the boom cylinder 1 via flow paths 311 and 337 . When the switching valve 20a is brought into communication by a signal from the controller 40A, the closed circuit pump 12a communicates with the boom cylinder 1 through the flow paths 300, 301, the switching valve 20a, the flow paths 310, 311, and the flow paths 336, 337. connected to form a closed circuit.

The switching valve 20b is connected to the cap chamber 3a of the arm cylinder 3 via flow paths 312 and 338, and is connected to the rod chamber 3b of the arm cylinder 3 via flow paths 313 and 339. When the switching valve 20b is brought into communication by a signal from the controller 40A, the closed circuit pump 12a communicates with the arm cylinder 3 via the flow paths 300, 301, the switching valve 20b, the flow paths 312, 313, and the flow paths 338, 339. connected to form a closed circuit.

Flow paths 302 and 303 are connected to a pair of input/output ports of the closed circuit pump 12b, and switching valves 20c and 20d are connected to the flow paths 302 and 303, respectively. The switching valves 20c and 20d switch between communication and blocking of the flow path according to a signal from the controller 40A. When there is no signal from the controller 40A, the switching valves 20c and 20d are closed.

The switching valve 20 c is connected to the cap chamber 1 a of the boom cylinder 1 via flow paths 314 and 336 and connected to the rod chamber 1 b of the boom cylinder 1 via flow paths 315 and 337 . When the switching valve 20c is brought into communication by a signal from the controller 40A, the closed circuit pump 12b communicates with the boom cylinder 1 via the flow paths 302, 303, the switching valve 20c, the flow paths 314, 315, and the flow paths 336, 337. connected to form a closed circuit.

The switching valve 20 d is connected to the cap chamber 3 a of the arm cylinder 3 via flow paths 316 and 338 and connected to the rod chamber 3 b of the arm cylinder 3 via flow paths 317 and 339 . When the switching valve 20d is brought into communication by a signal from the controller 40A, the closed circuit pump 12b communicates with the arm cylinder 3 via the flow paths 302, 303, the switching valve 20d, the flow paths 316, 317, and the flow paths 338, 339. connected to form a closed circuit.

A suction port of the open circuit pump 14 a is connected to the tank 33 . A discharge port of the open circuit pump 14a is connected to the switching valves 21a and 21b and the relief valve 25a via a flow path 330. As shown in FIG. A flow path 341 connecting the discharge port of the open circuit pump 14a to the tank 33 is provided with a proportional valve 22a.

The relief valve 25a releases hydraulic oil to the tank 33 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

The switching valves 21a and 21b switch between communication and blocking of the flow path according to a signal from the controller 40A. When there is no signal from the controller 40A, the switching valves 21a and 21b are closed.

The switching valve 21 a is connected to the cap chamber 1 a of the boom cylinder 1 via flow paths 332 and 336 .

The switching valve 21b is connected to the cap chamber 3a of the arm cylinder 3 via flow paths 333,338.

The proportional valve 22a changes its opening area according to a signal from the controller 40A to control the flow rate. In the absence of a signal from controller 40A, proportional valve 22a is held at its maximum open area. Further, when the switching valves 21a and 21b are closed, the controller 40A controls the discharge flow rate of the open circuit pump 14a to the minimum discharge flow rate, and the proportional valve is operated so that the hydraulic oil at this minimum discharge flow rate is discharged to the tank 33. 22a is slightly opened.

A suction port of the open circuit pump 14 b is connected to the tank 33 . A discharge port of the open circuit pump 14b is connected via a flow path 330 to the switching valves 21c and 21d and the relief valve 25b. A flow path 342 connecting the discharge port of the open circuit pump 14b to the tank 33 is provided with a proportional valve 22b.

The relief valve 25b releases hydraulic oil to the tank 33 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

The switching valves 21c and 21d switch between communication and blocking of the flow path according to a signal from the controller 40A. When there is no signal from the controller 40A, the switching valves 21c and 21d are closed.

The switching valve 21 c is connected to the cap chamber 1 a of the boom cylinder 1 via flow paths 334 and 336 .

The switching valve 21 d is connected to the cap chamber 3 a of the arm cylinder 3 via flow paths 335 and 338 .

The proportional valve 22b changes its opening area according to a signal from the controller 40A to control the flow rate. In the absence of a signal from controller 40A, proportional valve 22b is held at its maximum open area. Further, when the switching valves 21c and 21d are closed, the controller 40A controls the discharge flow rate of the open circuit pump 14b to the minimum discharge flow rate, and the proportional valve is operated so that the hydraulic oil at this minimum discharge flow rate is discharged to the tank 33. 22b is slightly opened.

A suction port of the charge pump 11 is connected to the tank 33 . A discharge port of the charge pump 11 is connected via a charge line 340 to the charge relief valve 28 and the charge check valves 30a, 31a, 30b, 31b, 32a, 32b.

The charge relief valve 28 sets the charge pressure of the charge check valves 30a, 31a, 30b, 31b, 32a, 32b.

The charge check valves 30 a and 31 a open when the pressure in the flow paths 336 and 337 falls below the charge pressure, and replenish the flow paths 336 and 337 with pressure oil from the charge line 340 .

The charge check valves 30b and 31b open when the pressure in the flow paths 338 and 339 falls below the charge pressure, and refill the flow paths 338 and 339 from the charge line 340 with pressure oil.

The charge check valve 32 a opens when the pressure in the flow paths 300 and 301 falls below the charge pressure, and replenishes the flow paths 300 and 301 with pressure oil from the charge line 340 .

The charge check valve 32b opens when the pressure in the flow paths 302 and 303 falls below the charge pressure, and replenishes the flow paths 302 and 303 with pressure oil from the charge line 340 .

Relief valves 23a and 24a provided in flow paths 300 and 301 release hydraulic fluid to charge line 340 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

The relief valves 23b, 24b provided in the flow paths 302, 303 release hydraulic oil to the charge line 340 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

The boom cylinder 1 is a single-rod hydraulic cylinder that expands and contracts when supplied with hydraulic oil. The expansion and contraction direction of the boom cylinder 1 depends on the supply direction of hydraulic oil.

Relief valves 26a and 27a provided in flow paths 336 and 337 release hydraulic fluid to charge line 340 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

Flushing valves 29 a provided in flow paths 336 and 337 discharge surplus oil in the flow paths to charge line 340 .

The arm cylinder 3 is a single-rod hydraulic cylinder that expands and contracts when supplied with hydraulic oil. The expansion and contraction direction of the arm cylinder 3 depends on the supply direction of hydraulic oil.

Relief valves 26b and 27b provided in flow paths 338 and 339 release hydraulic fluid to charge line 340 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

Flushing valves 29 b provided in flow paths 338 and 339 discharge surplus oil in the flow paths to charge line 340 .

8A to 8C show the control flow of the controller 40A.

The controller 40A first detects the oil temperature T of the tank 33 with the temperature sensor 42 in step S201. In subsequent step S202, it is determined whether or not the oil temperature T is lower than a predetermined threshold value T1.

If it is determined in step S202 that the oil temperature T is lower than the threshold value T1 (YES), the operation mode of the excavator 100 is set to the warm-up mode in step S203, and the lever operation includes boom operation in step S204. Determine whether or not

If it is determined in step S204 that the lever operation includes boom operation (YES), in step S205, the tilting angle of the closed circuit pump 12a is controlled according to the lever operation amount to open the switching valve 20a. In subsequent step S206, the tilting angle of the open circuit pump 14a is controlled to the minimum tilting angle, the proportional valve 22a is slightly opened, the switching valve 21a is closed, and the flow ends. As a result, the boom cylinder 1 is driven only by the closed circuit pump 12a.

If it is determined in step S204 that the lever operation does not include boom operation (NO), it is determined in step S207 whether or not the lever operation includes arm operation.

If it is determined in step S207 that the lever operation includes arm operation (YES), in step S208, the tilting angle of the closed circuit pump 12b is controlled according to the lever operation amount to open the switching valve 20d. In subsequent step S209, the tilting angle of the open circuit pump 14b is controlled to the minimum tilting angle, the proportional valve 22b is slightly opened, the switching valve 21d is closed, and the flow ends. As a result, the arm cylinder 1 is driven only by the closed circuit pump 12b.

If it is determined in step S207 that the lever operation does not include the arm operation (NO), the flow ends.

If it is determined in step S202 that the oil temperature T is equal to or higher than the threshold value T1 (NO), the operation mode is set to the normal mode in step S210, and in the following step S211, it is determined whether or not the lever operation is single boom operation. judge.

If it is determined in step S211 that the lever operation is the boom single operation (YES), it is determined in step S212 whether or not the lever operation is the cylinder extension operation.

If it is determined in step S212 that the lever operation is the cylinder extension operation (YES), in step S213, the tilt angles of the closed circuit pumps 12a and 12b are controlled according to the lever operation amount, and the switching valves 20a and 20c are controlled. open the In subsequent step S214, the tilting angles of the open circuit pumps 14a and 14b are controlled according to the lever operation amount, the proportional valves 22a and 22b are closed, the switching valves 21a and 21c are opened, and the flow ends. As a result, the oil discharged from the closed circuit pumps 12a, 12b and the open circuit pumps 14a, 14b is supplied to the cap chamber 1a of the boom cylinder 1, and the oil discharged from the rod chamber 1b is absorbed by the closed circuit pumps 12a, 12b.

If it is determined in step S212 that the lever operation is not the cylinder extension operation (NO), in step S215, the tilt angles of the closed circuit pumps 12a and 12b are controlled according to the lever operation amount, and the switching valves 20a and 20c are controlled. open the In subsequent step S216, the tilting angles of the open circuit pumps 14a and 14b are controlled to the minimum tilting angle, the proportional valves 22a and 22b are opened according to the lever operation amount, the switching valves 21a and 21c are opened, and the flow exit. As a result, the oil discharged from the closed circuit pumps 12a and 12b is supplied to the rod chamber 1b of the boom cylinder 1, part of the oil discharged from the cap chamber 1a is absorbed by the closed circuit pumps 12a and 12b, and the remaining part is It is discharged to the tank 33 via the proportional valves 22a, 22b.

If it is determined in step S211 that the lever operation is not the boom single operation (NO), it is determined in step S217 whether the lever operation is the arm single operation.

If it is determined in step S217 that the lever operation is the arm single operation (YES), it is determined in step S218 whether or not the lever operation is the arm extension operation.

If it is determined in step S218 that the lever operation is the arm extension operation (YES), in step S219, the tilt angles of the closed circuit pumps 12a and 12b are controlled according to the lever operation amount, and the switching valves 20b and 20d are controlled. open the In subsequent step S220, the tilting angles of the open circuit pumps 14a and 14b are controlled to the minimum tilting angle, the proportional valves 22a and 22b are closed, the switching valves 21b and 21d are opened, and the flow ends. As a result, the oil discharged from the closed circuit pumps 12a, 12b and the open circuit pumps 14a, 14b is supplied to the cap chamber 3a of the arm cylinder 3, and the oil discharged from the rod chamber 3b is absorbed by the closed circuit pumps 12a, 12b.

If it is determined in step S218 that the lever operation is not the arm extension operation (NO), in step S221, the tilt angles of the closed circuit pumps 12a and 12b are controlled according to the lever operation amount, and the switching valves 20b and 20d are controlled. open the In subsequent step S222, the tilting angles of the open circuit pumps 14a and 14b are controlled to the minimum tilting angle, the proportional valves 22a and 22b are opened according to the lever operation amount, the switching valves 21b and 21d are opened, and the flow exit. As a result, the oil discharged from the closed circuit pumps 12a and 12b is supplied to the rod chamber 3b of the arm cylinder 3, part of the oil discharged from the cap chamber 3a is absorbed by the closed circuit pumps 12a and 12b, and the remaining part is It is discharged to the tank 33 via the proportional valves 22a, 22b.

If it is determined in step S217 that the arm is not operated alone (NO), it is determined in step S223 whether or not the lever operation is an operation for driving a plurality of actuators (composite operation).

If it is determined in step S223 that the lever operation is a compound operation (YES), it is determined in step S224 whether or not the lever operation is a boom extension operation and an arm extension operation.

If it is determined in step S224 that the lever operation is both the boom extension operation and the arm extension operation (YES), then in step S225, the tilt angles of the closed circuit pumps 12a and 12b are controlled according to the lever operation amount, and switching is performed. The valves 20a, 20d are opened. In subsequent step S226, the tilting angle of the open circuit pump 14a is controlled according to the lever operation amount, the proportional valves 22a and 22b are closed, the switching valves 21a and 21d are opened, and the flow ends. As a result, the oil discharged from the closed circuit pump 12a and the open circuit pump 14a is supplied to the cap chamber 1a of the boom cylinder 1, and the oil discharged from the rod chamber 1b is absorbed by the closed circuit pump 12a. Also, the oil discharged from the closed circuit pump 12b and the open circuit pump 14b is supplied to the cap chamber 3a of the arm cylinder 3, and the oil discharged from the rod chamber 3b is absorbed by the closed circuit pump 12b.

If it is determined in step S224 that the lever operation is neither the boom extension operation nor the arm extension operation (NO), it is determined in step S227 whether or not the lever operation is the boom extension operation and the arm retraction operation.

If it is determined in step S227 that the lever operation is the boom extension operation and the arm retraction operation (YES), in step S228, the tilt angles of the closed circuit pumps 12a and 12b are controlled according to the lever operation amount, and switching is performed. The valves 20a, 20d are opened. In subsequent step S229, the tilting angle of the open circuit pump 14a is controlled according to the lever operation amount, the proportional valve 22a is closed, the switching valve 21a is opened, and the tilting angle of the open circuit pump 14b is set to the minimum tilting angle. , the proportional valve 22b is opened according to the lever operation amount, the switching valve 21d is opened, and the flow ends. As a result, the oil discharged from the closed circuit pump 12a and the open circuit pump 14a is supplied to the cap chamber 1a of the boom cylinder 1, and the oil discharged from the rod chamber 1b is absorbed by the closed circuit pump 12a. Also, the oil discharged from the closed circuit pump 12b is supplied to the rod chamber 3b of the arm cylinder 3, part of the oil discharged from the cap chamber 3a is absorbed by the closed circuit pump 12b, and the remaining part is absorbed through the proportional valve 22b. is discharged into the tank 33.

If it is determined in step S227 that the lever operation is not the boom extension operation and the arm retraction operation (NO), it is determined in step S230 whether the lever operation is the boom retraction operation and the arm extension operation.

If it is determined in step S230 that the lever operation is the boom retraction operation and the arm extension operation (YES), in step S231, the tilt angles of the closed circuit pumps 12a and 12b are controlled according to the lever operation amount, and switching is performed. The valves 20a, 20d are opened. In subsequent step S232, the tilting angle of the open circuit pump 14a is controlled to the minimum tilting angle, the proportional valve 22a is opened according to the lever operation amount, the switching valve 21a is opened, and the tilting angle of the open circuit pump 14b is reduced. is controlled according to the lever operation amount, the proportional valve 22b is closed, the switching valve 21d is opened, and the flow ends. As a result, the oil discharged from the closed circuit pump 12a is supplied to the rod chamber 1b of the boom cylinder 1, part of the oil discharged from the cap chamber 1a is absorbed by the closed circuit pump 12a, and the remaining part moves through the proportional valve 22a. It is discharged to the tank 33 through the Also, the oil discharged from the closed circuit pump 12b and the open circuit pump 14b is supplied to the cap chamber 3a of the arm cylinder 3, and the oil discharged from the rod chamber 3b is absorbed by the closed circuit pump 12b.

If it is determined in step S230 that the lever operation is not the boom retraction operation and the arm extension operation (NO), it is determined in step S233 whether the lever operation is the boom retraction operation and the arm retraction operation.

If it is determined in step S233 that the lever operation is both the boom retraction operation and the arm retraction operation (YES), in step S234, the tilt angles of the closed circuit pumps 12a and 12b are controlled according to the lever operation amount, and switching is performed. The valves 20a, 20d are opened. In subsequent step S235, the tilting angles of the open circuit pumps 14a and 14b are controlled to the minimum tilting angle, the proportional valves 22a and 22b are opened according to the lever operation amount, the switching valves 21a and 21d are opened, and the flow exit. As a result, the oil discharged from the closed circuit pump 12a is supplied to the rod chamber 1b of the boom cylinder 1, part of the oil discharged from the cap chamber 1a is absorbed by the closed circuit pump 12a, and the remaining part moves through the proportional valve 22a. It is discharged to the tank 33 through the Also, the oil discharged from the closed circuit pump 12b is supplied to the rod chamber 3b of the arm cylinder 3, part of the oil discharged from the cap chamber 3a is absorbed by the closed circuit pump 12b, and the remaining part is absorbed through the proportional valve 22b. is discharged into the tank 33.

If it is determined in step S233 that the lever operation is neither boom retraction nor arm retraction (NO), or if it is determined in step S223 that the lever operation is not a combined operation (NO), the flow ends. do.

Next, the operation when the control shown in FIGS. 8A to 8C is executed and the operation when it is not executed will be described.

FIG. 9A shows the operation result when the control of FIGS. 8A to 8C is executed while the oil temperature is higher than the threshold value T1.

At time t1, lever operation for raising the boom is started. Accordingly, the discharge flow rate of the closed circuit pumps 12a and 12b increases. In order to form a flow path between the closed circuit pumps 12a, 12b and the boom cylinder 1, the switching valves 20a, 20c are opened. In addition, because of the cylinder extension operation, the discharge flow rate of the open circuit pumps 14a and 14b also increases. In order to form a flow path between the open circuit pumps 14a, 14b and the boom cylinder 1, the switching valves 21a, 21c are opened. Proportional valves 22a, 22b are closed to prevent hydraulic fluid from flowing out of the circuit.

At time t2, arm cloud lever operation is started. At this time, since the closed circuit pump and the open circuit pump are all connected to the boom cylinder 1, in order to connect the closed circuit pump 12b and the open circuit pump 14b to the arm cylinder 3, the discharge flow rate of the closed circuit pump 12b is reduced to 0. Then, the discharge flow rate of the open circuit pump 14b is set to the minimum discharge flow rate, and the switching valves 20c and 21c are closed.

At time t3, the proportional valve 22b opens to discharge the minimum discharge flow rate of the open circuit pump 14b to the tank 33. After that, in order to drive the arm cylinder 3, the discharge flow rate of the closed circuit pump 12b is increased, and in order to form a flow path between the closed circuit pump 12b and the arm cylinder 3, the switching valve 20d is opened. Since it is a cylinder extension operation, the discharge flow rate of the open circuit pump 14b is increased, and in order to form a flow path between the open circuit pump 14b and the arm cylinder 3, the switching valve 21d is opened and the proportional valve 22b is closed.

At time t4, the lever operation for raising the boom ends. Along with this, the discharge flow rate of the closed circuit pump 12a is set to 0, and the switching valve 20a is closed. Also, the discharge flow rate of the open circuit pump 14a is set to the minimum discharge flow rate, the switching valve 21a is closed, and the proportional valve 22a is opened. Since the lever operation of the arm cloud continues, the discharge flow rate of the closed circuit pump 12a is increased and the switching valve 20b is opened. Since it is a cylinder extension operation, the discharge flow rate of the open circuit pump 14a is increased, the switching valve 21b is opened, and the proportional valve 22a is closed.

At time t5, the arm cloud lever operation ends. Along with this, the discharge flow rates of the closed circuit pumps 12a and 12b are set to 0, and the switching valves 20b and 20d are closed. The discharge flow rates of the open circuit pumps 14a and 14b are set to the minimum discharge flow rates, and the switching valves 21b and 21d are closed. Proportional valves 22a, 22b open to discharge to tank 33 the minimum discharge flow of open circuit pumps 14a, 14b.

With the above control, it is possible to operate the hydraulic excavator 100 by maximally using the closed circuit pump and the open circuit pump during single operation and combined operation.

FIG. 9B shows the operation result when the control of FIGS. 8A to 8C is not executed while the oil temperature is lower than the threshold value T1.

At time t1, lever operation for raising the boom is started. Accordingly, the discharge flow rate of the closed circuit pumps 12a and 12b increases. In order to form a flow path between the closed circuit pumps 12a, 12b and the boom cylinder 1, the switching valves 20a, 20c are opened. At this time, the hydraulic oil in the hydraulic circuit has a low temperature and a high viscosity. Therefore, the responsiveness of the switching valves 20a and 20c is lowered, and the behavior of the switching valves 20a and 20c becomes slower than after the end of warming up. In addition, because of the cylinder extension operation, the discharge flow rate of the open circuit pumps 14a and 14b also increases. In order to form a flow path between the open circuit pumps 14a, 14b and the boom cylinder 1, the switching valves 21a, 21c are opened. The switching valves 21a and 21c have low responsiveness due to the low temperature and high viscosity of the hydraulic oil, and their behavior becomes slower than after the end of warming up. The proportional valves 22a, 22b are closed to prevent hydraulic fluid in the circuit from flowing out of the proportional valves 22a, 22b.

At time t2, arm cloud lever operation is started. At this time, since the closed circuit pump and the open circuit pump are all connected to the boom cylinder 1, in order to connect the closed circuit pump 12b and the open circuit pump 14b to the arm cylinder 3, the discharge flow rate of the closed circuit pump 12b is set to 0. Then, the discharge flow rate of the open circuit pump 14b is set to the minimum discharge flow rate, and the switching valves 20c and 21c are closed. At this time, since the hydraulic oil has a low temperature and a high viscosity, the behavior of the switching valves 20c and 21c becomes slower than after the end of warming up.

At time t3, the proportional valve 22b opens to discharge the minimum discharge flow rate of the open circuit pump 14b to the tank 33. However, since the switching valve 21c is not completely closed, hydraulic oil flows out from the cap chamber 1a of the boom cylinder 1 to the tank 33 via the proportional valve 22b, and the boom cylinder 1 performs an unintended operation.

At time t3, in order to drive the arm cylinder 3, the discharge flow rate of the closed circuit pump 12b is increased, and in order to form a flow path between the closed circuit pump 12b and the arm cylinder 3, the switching valve 20d is opened. Since this is a cylinder extension operation, the discharge flow rate of the open circuit pump 14b is increased and the switching valve 21d is opened in order to form a flow path between the open circuit pump 14b and the arm cylinder 3. At this time, the responsiveness of the switching valves 20c, 20d, 21c, and 21d is poor, and the boom cylinder 1 and the arm cylinder 3 communicate with each other. As a result, when the pressure of the boom cylinder 1 is higher than the pressure of the arm cylinder 3 , hydraulic fluid flows from the boom cylinder 1 to the arm cylinder 3 . The stroke amount of the boom cylinder 1 decreases and the stroke amount of the arm cylinder 3 increases, resulting in unintended operation.

At time t4, the proportional valve 22b is closed in order to prevent hydraulic oil from flowing out from the proportional valve 22b to the tank 33. By closing the switching valves 20c and 21c, communication between the boom cylinder 1 and the arm cylinder 3 is interrupted, and unintended increase/decrease in cylinder stroke is eliminated.

At time t5, the lever operation for raising the boom ends. Along with this, the discharge flow rate of the closed circuit pump 12a is set to 0, and the switching valve 20a is closed. Also, the discharge flow rate of the open circuit pump 14a is set to the minimum discharge flow rate, the switching valve 21a is closed, and the proportional valve 22a is opened. Since the hydraulic oil has a low temperature and a high viscosity, the behavior of the switching valves 20a and 21a becomes slower than after warming up, and the switching valves 20a and 21a close at time t5'. By opening the proportional valve 22a before the switching valves 20a and 21a are closed, hydraulic oil flows out from the cap chamber 1a of the boom cylinder 1 to the tank 33 via the proportional valve 22a, and the boom cylinder 1 operates unintended. I'm going to go.

At time t5, the arm crowding operation continues, so the closed circuit pump 12a is controlled to be connected to the arm cylinder 3. The switching valve 21b is opened, and the closed circuit pump 12a and the arm cylinder 3 are connected.

At time t6, the operation of the arm cloud lever ends, the discharge flow rate of the closed circuit pumps 12a and 12b decreases, and the switching valves 20b and 20d close. The discharge flow rate of the open circuit pumps 14a, 14b becomes the minimum discharge flow rate, and the switching valves 21c, 21d are closed. Proportional valves 22a, 22b open to discharge to tank 33 the minimum discharge flow of open circuit pumps 14a, 14b. Since the hydraulic oil has a low temperature and a high viscosity, the behavior of the switching valves 20b and 21d becomes slower than after warming up, and before the switching valves 20b and 21d close at time t6', I open up. As a result, hydraulic oil flows out from the cap chamber 3a of the arm cylinder 3 to the tank 33 via the proportional valves 22a and 22b, and the boom cylinder 3 performs an unintended operation.

FIG. 9C shows the operation result when the control of FIGS. 8A to 8C is executed while the oil temperature is lower than the threshold value T1.

At time t1, lever operation for raising the boom is started. Accordingly, the discharge flow rate of the closed circuit pump 12a increases. In order to connect the closed circuit pump 12a and the boom cylinder 1, the switching valve 20a is opened. Since the oil temperature is equal to or lower than the threshold value T1, the open circuit pump 14a is at the minimum discharge flow rate, the switching valves 21a and 21b are closed, and the proportional valve 22a is open.

At time t2, arm cloud lever operation is started. Accordingly, the discharge flow rate of the closed circuit pump 12b increases. In order to connect the closed circuit pump 12b and the arm cylinder 3, the switching valve 20d is opened. Since the oil temperature is equal to or lower than the threshold value T1, the discharge flow rate of the open circuit pump 14b is the minimum discharge flow rate, the switching valves 21c and 21d are closed, and the proportional valve 22b is open.

At time t3, the lever operation for raising the boom ends. As a result, the discharge flow rate of the closed circuit pump decreases, closing the switching valve 20a.

At time t4, the lever operation of the arm cloud is completed, the discharge flow rate of the closed circuit pump 12b is reduced, and the switching valve 20d is closed.

A construction machine 100 according to the present embodiment connects a plurality of closed circuit pumps 12a and 12b, a plurality of actuators 1 and 3, and a plurality of closed circuit pumps 12a and 12b to the plurality of actuators 1 and 3 in a closed circuit. Equipped with a plurality of closed circuit switching valves 20a to 20d, the controller 40A controls the operation of each of the plurality of closed circuit pumps 12a and 12b when the temperature of the hydraulic oil detected by the temperature sensor 42 is lower than a predetermined temperature T1. A plurality of closed circuit switching valves 20a to 20d are controlled to open and close so as to be connected to only one of the plurality of actuators 1 and 3.

Specifically, by opening only one of the two or more closed circuit switching valves 20a and 20b (closed circuit switching valve 20a) connected to the closed circuit pump 12a, the closed circuit pump 12a is switched to the boom cylinder. 1, and by opening only one of the two or more closed circuit switching valves 20c and 20d connected to the closed circuit pump 12b (closed circuit switching valve 20d), the closed circuit pump 12b is limited to the arm cylinder 3 and connected.

According to this embodiment configured as described above, in the hydraulic closed circuit system in which the plurality of actuators 1 and 3 are driven by the plurality of closed circuit pumps 12a and 12b and the plurality of open circuit pumps 14a and 14b, When the oil temperature T is lower than the threshold value T1, the plurality of hydraulic cylinders 1 and 3 are driven only by the closed circuit pumps 12a and 12b, and the closed circuit pumps 12a and 12b are not reconnected to the plurality of actuators 1 and 3. Since this does not occur, it is possible to prevent unintended operation of the hydraulic cylinders 1 and 3 due to response delays of the cap side switching valves 21a-21d and the closed circuit switching valves 20a-20d.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations. Furthermore, it is also possible to add part of the configuration of another embodiment to the configuration of one embodiment, to delete part of the configuration of one embodiment, or to replace it with part of another embodiment. It is possible.

Reference Signs List 1 Boom cylinder (hydraulic cylinder) 1a Cap chamber 1b Rod chamber 2 Boom 3 Arm cylinder (hydraulic cylinder) 3a Cap chamber 3b Rod chamber 4 Arm 5 Bucket cylinder , 6... Bucket 7... Slewing motor 8... Traveling device 10... Power transmission device 11... Charge pump 12, 12a, 12b... Closed circuit pump, 13, 13a, 13b... Regulator, 14, 14a, 14b... Open circuit pumps 15, 15a, 15b... regulators 20, 20a to 20d... closed circuit switching valves 21, 21a to 21d... cap side switching valves 22, 22a, 22b... proportional valves 23, 23a, 23b, 24 , 24a, 24b, 25, 25a, 25b, 26, 26a, 26b, 27, 27a, 27b... relief valves 29, 29a, 29b... flushing valves 30, 30a, 30b, 31, 31a, 31b, 32, 32a , 32b... check valve for charge, 33... tank, 40... controller, 40a... operation mode determination unit, 40b... pump allocation calculation unit, 40c... pump signal output unit, 40d... switching valve signal output unit, 40e... proportional valve signal Output unit 41 Lever (operating device) 42 Temperature sensor 43 Switch 100 Hydraulic excavator (construction machine) 101 Cab 102 Upper revolving body (body) 103 Lower running body 104 Front work machine, 200 to 203, 210 to 212, 300 to 303, 310, 311 to 317, 330 to 342... flow path.

Claims (5)

a tank that stores hydraulic oil;
a single-rod hydraulic cylinder having a cap chamber and a rod chamber;
a closed circuit pump comprising a double tilting pump connected to the hydraulic cylinder in a closed circuit;
an open circuit pump consisting of a uni-tilting pump;
a cap-side switching valve that switches between flow and blockage of a flow path that connects the discharge port of the open circuit pump and the cap chamber;
a proportional valve provided in a flow path connecting the discharge port of the open circuit pump and the tank, the proportional valve having an adjustable opening area between zero and a predetermined maximum opening area;
an operating device for instructing the driving direction and driving speed of the hydraulic cylinder;
When the driving direction of the hydraulic cylinder instructed via the operating device is the extension direction, the cap-side switching valve is opened and the proportional valve is closed, and according to the operation amount of the operating device, the The discharge flow rates of the closed-circuit pump and the open-circuit pump are controlled, and when the driving direction of the hydraulic cylinder instructed via the operating device is the contraction direction, the cap-side switching valve is opened and the A construction machine comprising a controller that controls the discharge flow rate of the closed circuit pump and the opening area of the proportional valve according to the operation amount of the operating device,
A temperature sensor that detects the temperature of the hydraulic oil,
The controller closes the cap-side switching valve when the temperature of the hydraulic oil detected by the temperature sensor is lower than a predetermined temperature, and the discharge direction of the closed circuit pump is controlled according to the operating direction of the operating device. and controls the discharge flow rate of the closed circuit pump in accordance with the amount of operation of the operating device. In the construction machine according to claim 1,
a plurality of closed circuit pumps including the closed circuit pump;
a plurality of actuators including the hydraulic cylinder;
a plurality of closed-circuit switching valves for connecting the plurality of closed-circuit pumps to the plurality of actuators in a closed-circuit manner;
The controller connects each of the plurality of closed circuit pumps to only one of the plurality of actuators when the temperature of the hydraulic oil detected by the temperature sensor is lower than a predetermined temperature. A construction machine characterized by controlling the opening and closing of the plurality of closed circuit switching valves in such a manner. In the construction machine according to claim 2,
By opening only one closed circuit switching valve among two or more closed circuit switching valves connected to one closed circuit pump among the plurality of closed circuit pumps, the one closed circuit pump is switched to the A construction machine characterized in that connection is limited to any one of a plurality of actuators. In the construction machine according to claim 2,
a vehicle body;
a boom vertically rotatably connected to the vehicle body;
an arm connected to the tip of the boom so as to be rotatable in vertical and longitudinal directions;
The construction machine, wherein the plurality of actuators include a boom cylinder that drives the boom and an arm cylinder that drives the arm. In the construction machine according to claim 1,
The construction machine, wherein the temperature sensor is provided in the tank.

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