JP2023184576A - Construction machine - Google Patents

Abstract

To provide a construction machine which can suppress the lag-down of an engine irrespective of an operation content of an operator and load states of fluid-pressure actuators.SOLUTION: A controller 50 calculates requirement torque being torque which is required for an engine 9 by closed circuit pumps 12, 13 and open circuit pumps 14, 15 on the basis of requirement flow rates of fluid-pressure actuators 1, 3, 5 and 7, the outlet/inlet pressure of the fluid-pressure actuators 1, 3, 5 and 7, requirement discharge flow rates of the open circuit pumps 14, 15, and the outlet pressure of the open circuit pumps 14, 15. When a requirement torque change rate being a change rate of the requirement torque exceeds a prescribed change rate, the controller limits at least one discharge flow rate out of those of the closed circuit pumps 12, 13, and the open circuit pumps 14, 15.SELECTED DRAWING: Figure 3

Description

The present invention relates to a construction machine equipped with a hydraulic circuit that directly drives a hydraulic actuator with a hydraulic pump.

In recent years, in construction machinery such as hydraulic excavators, hydraulic fluid is sent from the hydraulic pump to the hydraulic actuator in order to reduce the throttling elements in the hydraulic circuit that drives the hydraulic actuator such as the hydraulic cylinder and reduce the fuel consumption rate. The development of a hydraulic circuit (hereinafter referred to as a hydraulic closed circuit) that connects the hydraulic fluid that has done its work to the hydraulic pump instead of returning it to the tank is underway.

When driving a hydraulic pump using an engine as the driving force, it is necessary to use the engine's output effectively while controlling the horsepower load applied to the engine so that the engine does not stop due to overload. For example, Patent Document 1 discloses a prior art related to horsepower control of a hydraulic pump.

Patent Document 1 discloses a control device installed in a working machine having a variable displacement hydraulic pump driven by an engine and a plurality of actuators to which hydraulic oil is supplied from the hydraulic pump, the control device being provided to a working machine that has a variable displacement hydraulic pump driven by an engine, and a plurality of actuators to which hydraulic oil is supplied from the hydraulic pump, The amount of operation for each operation specified by the input part (operation lever) that is operated to input an operation command, the actuator to be operated among the actuators, and the direction of the operation for this actuator. and an upper limit value of absorption horsepower of the hydraulic pump; and a storage unit that stores horsepower information in association with an upper limit value of absorption horsepower of the hydraulic pump; and horsepower information stored in the storage unit when an actuation command for at least one actuator is input by the input unit. an operating horsepower determination unit that determines the upper limit value of the absorption horsepower for each actuator using the operation horsepower determination unit; and a high-level selection that selects the largest upper limit value of the absorption horsepower from among the upper limit values of the absorption horsepower determined by the operation horsepower determination unit. and a capacity adjustment unit that adjusts the capacity of the hydraulic pump so that the horsepower is less than or equal to the absorption horsepower selected by the high-level selection unit, and at least one of the horsepower information stored in the storage unit. A control device for a working machine is described in which the horsepower information related to the operation content has a characteristic that the upper limit value of the absorbed horsepower changes according to a change in the operation amount of the input section.

Japanese Patent Application Publication No. 2010-276126

According to the control device for a work machine described in Patent Document 1, the upper limit value of the absorption horsepower of the hydraulic pump is set according to the operation amount and operation direction of the operation lever, thereby suppressing the load on the engine and preventing problems such as engine stalling. Problems can be suppressed. However, since the operating speed of the operating lever and the load condition of the actuator are not taken into account, the following problems arise, for example.

When the operator operates the control lever at high speed, the discharge flow rate of the hydraulic pump connected to the actuator to be operated increases rapidly, and the torque (( (required torque) increases rapidly. At this time, even if the engine output torque does not increase in time for the increase in the required torque and the absolute value of the required torque is less than the maximum rated torque of the engine, the engine speed may stop or temporarily decrease. There is a risk that a phenomenon (lagdown) may occur. This tendency is particularly noticeable in a hydraulic closed circuit in which an actuator is directly driven by a hydraulic pump, since there is no throttling element interposed between the actuator and the hydraulic pump, and the load of the actuator is directly transmitted to the hydraulic pump.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a construction machine that can suppress engine lag-down regardless of the operator's operation or the load condition of the actuator.

In order to achieve the above object, the present invention includes an undercarriage body, an upper revolving body rotatably mounted on the undercarriage body, a working device attached to the upper revolving body, and a pair of entrances and exits. A plurality of closed circuit pumps that are double tilting hydraulic pumps having ports, a plurality of open circuit pumps that are single tilting hydraulic pumps having an inlet port and an outlet port, and the plurality of closed circuit pumps. and an engine that drives the plurality of open circuit pumps, a plurality of hydraulic actuators connected in a closed circuit to the plurality of closed circuit pumps, and a plurality of hydraulic actuators connected in an open circuit to the plurality of open circuit pumps. A hydraulic motor, a flow path connecting the plurality of open circuit pumps and the plurality of hydraulic motors, and a direction and direction of pressure oil supplied from the plurality of open circuit pumps to the plurality of hydraulic motors. a plurality of flow control valves for controlling the flow rate; an operating device for instructing each operating direction and each required flow rate of the plurality of hydraulic actuators and the plurality of hydraulic motors; a controller that controls each tilting of the plurality of closed-circuit pumps and the plurality of open-circuit pumps and each opening of the plurality of flow control valves; and a plurality of first controllers that detect the inlet and outlet pressures of the plurality of hydraulic actuators. In a construction machine including a pressure sensor and a plurality of second pressure sensors that detect outlet pressures of each of the plurality of open circuit pumps, the plurality of hydraulic actuators include a single rod cylinder that drives the working device; a swing motor that drives the upper rotating structure, the plurality of hydraulic motors include a travel motor that drives the lower rotating structure, and the controller controls the plurality of hydraulic pressure motors according to input from the operating device. each required flow rate of the pressure actuator, each inlet/outlet pressure of the plurality of hydraulic actuators detected by the plurality of first pressure sensors, and each required discharge of the plurality of open circuit pumps according to the input from the operating device. Based on the flow rate and each outlet pressure of the plurality of open-circuit pumps detected by the plurality of second pressure sensors, the plurality of closed-circuit pumps and the plurality of open-circuit pumps are configured to generate torques that are required of the engine. When a certain required torque is calculated and the required torque change rate, which is the change rate of the required torque, exceeds a predetermined change rate while the traveling motor, the single rod cylinder, and the swing motor are being driven simultaneously. , limiting the required flow rate of the traveling motor so that the torque required by the plurality of open circuit pumps connected to the traveling motor from the engine is equal to or less than a predetermined first percentage of the allowable output torque of the engine; A value obtained by subtracting the required torque of the open circuit pump limited by the restriction of the required flow rate of the travel motor and the required torque of the plurality of closed circuit pumps connected to the single rod cylinder and the swing motor from the allowable output torque. is positive, the required flow rate of the single rod cylinder and the swing motor is calculated based on the input from the operating device, and from the allowable output torque, the required flow rate of the traveling motor is limited by the limit of the required flow rate of the traveling motor. If the value obtained by subtracting the required torque of the open circuit pump from the required torque of the plurality of closed circuit pumps connected to the single rod cylinder and the swing motor is not positive, the required flow rate of the traveling motor is limited. requesting the swing motor such that the ratio of the required torque of the swing motor to the allowable output torque after allocating the required torque of the open circuit pump is equal to or less than a predetermined second ratio that is smaller than the first ratio; The demand for the swing motor is calculated from the allowable output torque after limiting the flow rate to limit the required torque of the swing motor and allocating the required torque of the open circuit pump limited by the restriction of the required flow rate of the travel motor. If the value obtained by subtracting the required torque of the swing motor limited by the flow rate restriction and the required torque of the closed circuit pump connected to the single-rod cylinder is positive, the From the allowable output torque after calculating the required flow rate of the single rod cylinder and assigning the required torque of the open circuit pump, which is limited by the restriction of the required flow rate of the travel motor, the required flow rate of the swing motor is calculated. If the value obtained by subtracting the required torque of the swing motor and the required torque of the closed circuit pump connected to the single-rod cylinder is not positive, the required speed of the travel motor, the single-rod cylinder, and the swing motor is The discharge flow rate of the closed circuit pump connected to the single rod cylinder is limited by limiting the required flow rate of the single rod cylinder so that the ratio is maintained and the output torque is equal to or less than the allowable output torque.

According to the present invention configured as described above, when the required torque change rate, which is the rate of change in the torque that the closed circuit pump and the open circuit pump request from the engine, exceeds a predetermined rate of change, the closed circuit pump and the open circuit pump The output flow rate of at least one of the circuit pumps is limited. This makes it possible to suppress engine lag down regardless of the operator's operation or the load condition of the hydraulic actuator.

According to the construction machine according to the present invention, engine lag down can be suppressed regardless of the operator's operation details or the load condition of the actuator.

1 is a side view of a hydraulic excavator according to an embodiment of the present invention. 2 is a schematic configuration diagram of a hydraulic drive device mounted on the hydraulic excavator shown in FIG. 1. FIG. 3 is a functional block diagram of the controller shown in FIG. 2. FIG. FIG. 3 is a diagram showing the behavior of the hydraulic drive device shown in FIG. 2 during single running operation. 3 is a flowchart showing processing performed by the controller shown in FIG. 2 during independent running operation. FIG. 2 is a diagram showing the relationship between load torque and engine rotation speed of a typical turbo engine. FIG. 3 is a diagram showing the behavior of the hydraulic drive device shown in FIG. 2 during a combined operation of traveling and boom raising. 3 is a flowchart (1/3) illustrating a process of the controller shown in FIG. 2 during a combined travel operation. FIG. 3 is a flowchart (2/3) illustrating processing of the controller shown in FIG. 2 during a combined travel operation; FIG. 3 is a flowchart (3/3) illustrating a process of the controller illustrated in FIG. 2 during a combined travel operation. FIG. 3 is a functional block diagram of a controller according to a modification of the embodiment of the present invention. FIG. 3 is a diagram showing the behavior of the hydraulic drive device shown in FIG. 2 during a combined operation of traveling + boom raising + turning;

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

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

In FIG. 1, a hydraulic excavator 100 includes an undercarriage body 101 equipped with a crawler-type traveling device driven by travel motors 8a and 8b, and an undercarriage body 101 that is rotatably mounted on the undercarriage body 101 and is driven by a swing motor 7. The rotating upper body 102 includes a rotating upper body 102, and a working device 103 attached to the front part of the rotating upper body 102 so as to be rotatable in the vertical direction. A cab 104 on which an operator rides is provided on the upper revolving body 102.

The working device 103 includes a boom 2 attached to the front part of the upper revolving body 102 so as to be rotatable in the vertical direction, and an arm serving as a working member connected to the tip of the boom 2 so as to be rotatable in the vertical or front-back direction. 4, a bucket 6 as a working member connected to the tip of the arm 4 so as to be rotatable in the vertical or longitudinal direction, a boom cylinder 1 which is a hydraulic cylinder that drives the boom 2, and a hydraulic cylinder that drives the arm 4. It includes an arm cylinder 3 that is a pressure cylinder, and a bucket cylinder 5 that is a hydraulic cylinder that drives a bucket 6.

FIG. 2 is a schematic configuration diagram of a hydraulic drive device mounted on the hydraulic excavator 100 shown in FIG. 1. In order to simplify the explanation, FIG. 2 shows only the parts related to the driving of the boom cylinder 1, the swing motor 7, and the travel motors 8a and 8b, and the parts related to the driving of other actuators are omitted.

An engine 9 that is a power source is connected to a power transmission device 10 that distributes power. A charge pump 11 and first to fourth hydraulic pumps 12 to 15 are connected to the power transmission device 10.

The first and second hydraulic pumps 12 and 13 include a tilting swash plate mechanism having a pair of input and output ports, and regulators 12a and 13a that adjust the inclination angle of the tilting swash plate.

The third and fourth hydraulic pumps 14 and 15 include a tilting swash plate mechanism having a discharge port and a suction port, and regulators 14a and 15a that adjust the inclination angle of the tilting swash plate.

The regulators 12a, 13a, 14a, and 15a adjust the tilting angles of the tilting swash plates of the first to fourth hydraulic pumps 12 to 15 based on signals from the controller 50.

The first and second hydraulic pumps 12 and 13 can control the discharge direction and discharge flow rate of hydraulic fluid by adjusting the tilt angle of the tilting swash plate. The first and second hydraulic pumps 12 and 13 also function as hydraulic motors by being supplied with pressure oil.

The third and fourth hydraulic pumps 14 and 15 can control the discharge flow rate of hydraulic oil by adjusting the tilting angle of the tilting swash plate.

Flow paths 200, 201 are connected to a pair of input/output ports of the first hydraulic pump 12, and switching valves 40, 41 are connected to the flow paths 200, 201. The switching valves 40 and 41 switch between communicating and blocking the flow path in response to a signal from the controller 50. The switching valves 40 and 41 are in a cutoff state when there is no signal from the controller 50.

The switching valve 40 is connected to the boom cylinder 1 via flow paths 210 and 211. When the switching valve 40 is brought into communication by a signal from the controller 50, the first hydraulic pump 12 is connected to the boom cylinder 1 via the channels 200, 201, the switching valve 40, and the channels 210, 211, Configure a closed circuit.

The switching valve 41 is connected to the swing motor 7 via channels 215 and 216. When the switching valve 41 is brought into communication by a signal from the controller 50, the first hydraulic pump 12 is connected to the swing motor 7 via the channels 200, 201, the switching valve 41, and the channels 215, 216, Configure a closed circuit.

Flow paths 202 and 203 are connected to a pair of input and output ports of the second hydraulic pump 13, and switching valves 42 and 43 are connected to the flow paths 202 and 203. The switching valves 42 and 43 switch between communicating and blocking the flow path in response to a signal from the controller 50. The switching valves 42 and 43 are in a cutoff state when there is no signal from the controller 50.

The switching valve 42 is connected to the boom cylinder 1 via flow paths 210 and 211. When the switching valve 42 is brought into communication by a signal from the controller 50, the second hydraulic pump 13 is connected to the boom cylinder 1 via the channels 202, 203, the switching valve 42, and the channels 210, 211, Configure a closed circuit.

The switching valve 43 is connected to the swing motor 7 via channels 215 and 216. When the switching valve 43 is brought into communication by a signal from the controller 50, the second hydraulic pump 13 is connected to the swing motor 7 via the channels 202, 203, the switching valve 43, and the channels 215, 216, Configure a closed circuit.

A discharge port of the third hydraulic pump 14 is connected to the relief valve 21, the switching valves 44, 45, and the proportional valve 48 via the flow path 204. A suction port of the third hydraulic pump 14 is connected to the tank 25 .

The relief valve 21 protects the circuit by releasing the hydraulic oil to the tank 25 when the flow path pressure exceeds a predetermined pressure.

The switching valves 44 and 45 switch between communicating and blocking the flow path in response to a signal from the controller 50. When there is no signal from the controller 50, the switching valves 44 and 45 are in a cutoff state. The switching valve 44 is connected to the head chamber 1a of the boom cylinder 1 via a flow path 210. The switching valve 45 is connected to flow control valves 71a and 71b via a flow path 213.

The proportional valve 48 changes its opening area in response to a signal from the controller 50 to control the flow rate. In the absence of a signal from controller 50, proportional valve 48 is held at its maximum opening area. Further, when the switching valves 44 and 45 are in the cutoff state, the controller 50 outputs a signal to the proportional valve 48 so that the opening area becomes a predetermined opening area according to the discharge flow rate of the third hydraulic pump 14.

A discharge port of the fourth hydraulic pump 15 is connected to the relief valve 22, the switching valves 46, 47, and the proportional valve 49 via the flow path 205. A suction port of the fourth hydraulic pump 15 is connected to the tank 25 .

The relief valve 22 protects the circuit by releasing the hydraulic oil to the tank 25 when the flow path pressure exceeds a predetermined pressure.

The switching valves 46 and 47 switch between communicating and blocking the flow path in response to a signal from the controller 50. When there is no signal from the controller 50, the switching valves 46 and 47 are in a closed state. The switching valve 46 is connected to the head chamber 1a of the boom cylinder 1 via a flow path 210. The switching valve 47 is connected to flow control valves 71a and 71b via a flow path 213.

The proportional valve 49 changes its opening area in response to a signal from the controller 50 to control the flow rate. In the absence of a signal from controller 50, proportional valve 49 is held at its maximum opening area. Further, when the switching valves 46 and 47 are in the cutoff state, the controller 50 outputs a signal to the proportional valve 49 so that the opening area becomes a predetermined opening area according to the discharge flow rate of the fourth hydraulic pump 15.

A discharge port of the charge pump 11 is connected to a charging relief valve 20 and charging check valves 26, 27, 28a, 28b, 36a, and 36b via a flow path 212 as a charging line. A suction port of charge pump 11 is connected to tank 25 . Charge pump 11 supplies pressure oil to flow path 212 .

The charging relief valve 20 adjusts the charging pressure of the charging check valves 26, 27, 28a, 28b, 36a, and 36b.

The charge check valve 26 replenishes the pressure oil in the charge line 212 to the flow paths 200, 201 when the pressure in the flow paths 200, 201 falls below the pressure set by the charge relief valve 20.

The charge check valve 27 replenishes the pressure oil in the charge line 212 to the flow paths 202 and 203 when the pressure in the flow paths 202 and 203 falls below the pressure set by the charge relief valve 20 .

The charge check valves 28a and 28b replenish the pressure oil in the charge line 212 to the flow paths 210 and 211 when the pressure in the flow paths 210 and 211 falls below the pressure set by the charge relief valve 20.

The charging check valves 36a and 36b replenish the pressure oil in the charge line 212 to the flow paths 215 and 216 when the pressure in the flow paths 215 and 216 falls below the pressure set by the charge relief valve 20.

The relief valves 30a and 30b provided in the flow paths 200 and 201 release hydraulic oil to the charge line 212 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

The relief valves 31a and 31b provided in the flow paths 202 and 203 release hydraulic oil to the charge line 212 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

The boom cylinder 1 is a hydraulic single rod cylinder that expands and contracts when supplied with hydraulic oil. The direction in which the boom cylinder 1 expands and contracts depends on the direction in which hydraulic oil is supplied.

The relief valves 32a and 32b provided in the flow paths 210 and 211 release hydraulic oil to the charge line 212 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

Flushing valves 34 provided in the flow paths 210 and 211 discharge excess oil in the flow paths to the charge line 212.

The swing motor 7 is a hydraulic motor that rotates when supplied with hydraulic oil. The rotation direction of the swing motor 7 depends on the supply direction of hydraulic oil.

Relief valves 37a and 37b provided in flow paths 215 and 216 release hydraulic oil to charge line 212 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

Flushing valves 38 provided in the flow paths 215 and 216 discharge excess oil in the flow paths to the charge line 212.

The travel motors 8a and 8b are hydraulic motors that rotate when supplied with hydraulic oil. The rotation direction of the travel motors 8a, 8b depends on the supply direction of hydraulic oil. One input/output port of the travel motors 8a, 8b is connected to flow control valves 71a, 71b via a flow path 217. The other input/output ports of the travel motors 8a, 8b are connected to flow control valves 71a, 71b via a flow path 218.

The relief valve 70a provided in the flow path 217 releases hydraulic oil to the flow path 218 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

The relief valve 70b provided in the flow path 218 releases hydraulic oil to the flow path 217 to protect the circuit when the flow path pressure exceeds a predetermined pressure.

The flow control valves 71a and 71b include three ports on the pump side and three ports on the travel motor side. A first port and a second port on the pump side are connected to the flow path 213, and a third port is connected to the tank 25. A first port on the traveling motor side is connected to a flow path 217, a second port is connected to a tank 25, and a third port is connected to a flow path 218.

The flow control valves 71a, 71b have three opening states. In the first open state, the first port on the pump side is closed, the second port on the pump side and the second port on the travel motor side are connected, and the third port on the pump side and the third port on the travel motor side are connected. Connect the first port and the third port. In the second open state, the first port on the pump side and the first port on the travel motor side are connected, the second port on the pump side is closed, the second port on the travel motor side is closed, and the pump side Connect the third port on the drive motor side to the third port on the travel motor side. In the third open state, the first port on the pump side and the third port on the drive motor side are connected, the second port on the pump side is closed, the second port on the drive motor side is closed, and the pump side Connect the third port of the drive motor to the first port of the travel motor.

The flow rate control valves 71a and 71b are changed to one of three open states in response to a signal from the controller 50, and control the passing flow rate. When there is no signal from the controller 50, the flow control valves 71a, 71b are maintained in the first open state. When a positive signal is input from the controller 50, the flow control valves 71a, 71b transition from the first open state to the second open state. When a negative signal is input from the controller 50, the flow control valves 71a, 71b transition from the first open state to the third open state.

A pressure sensor 60 a connected to the flow path 210 measures the pressure of the flow path 210 and inputs it to the controller 50 . The pressure sensor 60a measures the pressure in the head chamber of the boom cylinder 1 by measuring the pressure in the flow path 210.

A pressure sensor 60 b connected to the flow path 211 measures the pressure of the flow path 211 and inputs it to the controller 50 . The pressure sensor 60b measures the pressure in the rod chamber of the boom cylinder 1 by measuring the pressure in the flow path 211.

A pressure sensor 62 a connected to the flow path 215 measures the pressure of the flow path 215 and inputs it to the controller 50 . The pressure sensor 62a measures the pressure of one input/output port of the swing motor 7 by measuring the pressure of the flow path 215.

The pressure sensor 62b connected to the flow path 216 measures the pressure of the flow path 216 and inputs it to the controller 50. The pressure sensor 62b measures the pressure of the other input/output port of the swing motor 7 by measuring the pressure of the flow path 216.

A pressure sensor 72 connected to the flow path 204 measures the pressure in the flow path 204 and inputs it to the controller 50 . The pressure sensor 72 measures the discharge pressure of the third hydraulic pump 14 by measuring the pressure in the flow path 204 .

A pressure sensor 73 connected to the flow path 205 measures the pressure in the flow path 205 and inputs it to the controller 50 . The pressure sensor 73 measures the discharge pressure of the fourth hydraulic pump 15 by measuring the pressure in the flow path 205 .

The lever 51 is operated by an operator, and the amount of the operation is input to the controller 50.

FIG. 3 is a functional block diagram of the controller 50 shown in FIG. 2. In addition, in FIG. 3, like FIG. 2, only the parts related to the drive of the boom cylinder 1, the swing motor 7, and the travel motors 8a and 8b are shown, and the parts related to the drive of other actuators are omitted.

In FIG. 3, the controller 50 includes a required flow rate calculation section 50a, an actuator pressure calculation section 50b, a pump pressure calculation section 50c, a required torque calculation section 50d, a required flow rate restriction section 50e, and a command calculation section 50f. ing.

The required flow rate calculating section 50a calculates the operating direction and required flow rate of each actuator in response to the operator's lever input, and outputs the calculated directions to the required torque calculating section 50d and the required flow rate limiting section 50e.

The actuator pressure calculation section 50b calculates the pressure of the actuators 1 and 7 (hereinafter referred to as actuator pressure) from the values of the pressure sensors 60a, 60b, 62a, and 62b, and outputs it to the required torque calculation section 50d and the command calculation section 50f.

The pump pressure calculation unit 50c calculates the pressures of the third and fourth hydraulic pumps 14 and 15 (hereinafter referred to as pump pressure) from the values of the pressure sensors 72 and 73, and calculates the pressures of the third and fourth hydraulic pumps 14 and 15 (hereinafter referred to as pump pressure), and calculates the pressures of the third and fourth hydraulic pumps 14 and 15 (hereinafter referred to as pump pressure), and calculates the pressures of the third and fourth hydraulic pumps 14 and 15 (hereinafter referred to as pump pressure), and calculates the pressures of the third and fourth hydraulic pumps 14 and 15 (hereinafter referred to as pump pressure) Output to.

The required torque calculation unit 50d calculates the operator's lever input based on the required flow rate input from the required flow rate calculation unit 50a, the actuator pressure input from the actuator pressure calculation unit 50b, and the pump pressure input from the pump pressure calculation unit 50c. The torque applied to the engine 9 when the actuators 1, 7, 8a, and 8b are driven according to the torque (hereinafter referred to as required torque) is calculated.

The required flow rate restriction unit 50e calculates a rate of change in the required torque (hereinafter referred to as a required torque rate of change) based on the required torque input from the required torque calculation unit 50d. Then, the required flow rate input from the required flow rate calculation unit 50a is limited so that the required torque change rate does not exceed an allowable output torque change rate (described later) that is preset based on the characteristics of the engine 9, and the command calculation unit Output to 50f.

The command calculation unit 50f adjusts the switching valves 40 to 47 based on the required flow rate input from the required flow rate restriction unit 50e, the actuator pressure input from the actuator pressure calculation unit 50b, and the pump pressure input from the pump pressure calculation unit 50c. , proportional valves 48, 49, flow rate control valves 71a, 71b, and regulators 12a, 13a, 14a, 15a, and output them to each of them.

Next, the operation of the hydraulic drive device shown in FIG. 2 will be explained.

(1) When not operated In FIG. 2, when the lever 51 is not operated, the first to fourth hydraulic pumps 12 to 15 are controlled to the minimum tilt angle, the switching valves 40 to 47 are all closed, and the boom The cylinder 1, the swing motor 7, and the travel motors 8a, 8b are held in a stopped state.

(2) During independent travel operation Figure 4 shows the input of the lever 51 during independent travel operation, and the opening areas of the flow control valves 71a and 71b (opening 1 is the first port on the pump side and the first port on the travel motor side). Opening 2 is the opening area between the second port on the pump side and the second port on the traveling motor side, Opening 3 is the opening area between the third port on the pump side and the third port on the traveling motor side. (opening area between the ports of 3 shows changes in discharge pressure, engine load torque (required torque), and discharge flow rates of the third and fourth hydraulic pumps 14 and 15.

From time t0 to time t1, among the inputs from the lever 51, a command value (hereinafter referred to as a travel command value) that instructs forward rotation of the travel motors 8a and 8b is 0, and the travel motors 8a and 8b are stationary.

From time t1 to time t2, among the inputs to the lever 51, the travel command value is increased from 0 to the maximum value.

FIG. 5 is a flowchart showing the processing of the controller 50 during the traveling operation.

First, in step S1, the controller 50 calculates the required discharge flow rate Qop_d of the pump that supplies hydraulic oil to the travel motors 8a, 8b based on the input Lin from the lever 51. In addition, in this embodiment, since the third hydraulic pump 14 and the fourth hydraulic pump 15 supply hydraulic oil to the travel motors 8a and 8b, the required discharge flow rate Qop_d is different from that of the third hydraulic pump 14. is equal to the sum of the required discharge flow rate Qop14_d of the fourth hydraulic pump 15 and the required discharge flow rate Qop15_d of the fourth hydraulic pump 15. The required discharge flow rate Qop_d is defined as a function of the input Lin of the lever 51 as follows.

The flow rate actually passing through the travel motors 8a, 8b is controlled by the opening area of the flow rate control valves 71a, 71b. In order to improve the responsiveness of the flow rate control by opening the flow rate control valves 71a and 71b, the required discharge flow rate Qop_d of the pump is set to the maximum value when the travel command value of the input Lin of the lever 51 is not 0. You can.

Next, in step S2, the controller 50 considers the characteristics of the engine 9 and limits the rate of change in the required discharge flow rate Qop_d determined in step S1.

Next, in step S3, the controller 50 controls the discharge pressure Pop14 of the third hydraulic pump 14 measured by the pressure sensor 72, the discharge pressure Pop15 of the fourth hydraulic pump 15 measured by the pressure sensor 73, and the discharge pressure Pop15 of the fourth hydraulic pump 15 measured by the pressure sensor 73. Based on the required discharge flow rate Qop14_d of the hydraulic pump 14 and the required discharge flow rate Qop15_d of the fourth hydraulic pump 15, the flow rate is supplied from the third hydraulic pump 14 and the fourth hydraulic pump 15 as requested by the lever 51. In this case, the required torque Tp_d generated by the pumps 14 and 15 is calculated based on, for example, the following equation (2). The total Top_d of the required torque of the third hydraulic pump 14 and the required torque of the third hydraulic pump 15 is

becomes. Here, Neng is the engine rotational speed, and ηop is the pump efficiency of the third hydraulic pump 14 and the fourth hydraulic pump 15.

The required torque Tp_d generated by all pumps is as follows.

Next, in step S4, the rate of change in the required torque Tp_d (required torque rate of change) is calculated. The required torque change rate is obtained, for example, by dividing the value obtained by subtracting the torque currently output by the engine 9 from the required torque Tp_d by the control period of the controller 50.

Next, in step S5, the controller 50 determines whether the required torque change rate calculated in step S4 is less than or equal to the change rate of allowable output torque Tp_lim (hereinafter referred to as allowable output torque change rate). If the required torque change rate is less than or equal to the allowable output torque change rate, the process proceeds to step S7; otherwise, the process proceeds to step S6. The allowable output torque Tp_lim is the torque that the engine 9 can currently output, and can be calculated from information such as the fuel injection amount and turbo pressure of the engine 9. Here, the allowable output torque Tp_lim and the allowable output torque change rate may be determined as follows.

In the case of a turbocharged engine, when a load is applied to the engine from a no-load state, the design maximum torque cannot be output until the turbo pressure increases. For example, as shown in Fig. 6, when the engine load torque (required torque Tp_d) is increased from the minimum value to the maximum value from time t1 to time t2, the engine output torque does not increase in time for the increase in engine load torque. , the engine speed falls below the minimum allowable speed. Here, the minimum allowable rotation speed is the rotation speed obtained by subtracting the maximum allowable decrease from the target rotation speed. On the other hand, if the engine load torque is increased from the minimum value to the maximum value from time t1 to time t3, the engine output torque will increase in time for the increase in engine load torque, so the engine speed will never fall below the allowable minimum rotation speed. do not have. Therefore, the maximum torque change rate at which the decrease in engine speed can be suppressed to the allowable minimum rotation speed is set as the allowable output torque change rate, and the maximum output torque that satisfies the allowable output torque change rate is set as the allowable output torque Tp_lim. For example, it is determined by adding the product of the allowable output torque change rate and the control cycle of the controller 50 to the current engine output torque. That is, the allowable output torque Tp_lim in the present invention changes from moment to moment according to the current engine output torque. Note that in step S5, it is determined whether the required torque change rate is less than or equal to the allowable output torque change rate, but this determination is not the same as determining whether or not the required torque Tp_d is less than or equal to the allowable output torque Tp_lim. It's the same.

Here, when a general construction machine performs running operation on flat ground, as shown in FIG. 4, the discharge pressures Pop14 and Pop15 of the pumps 14 and 15 are low while running is stopped (time t0 to time t1), and when running is accelerating. It has a characteristic that the speed rises from time t1 to time t3 and becomes constant at a steady speed (from time t3). Particularly when traveling at maximum acceleration, the pump discharge pressures Pop14 and Pop15 rise to the set pressures of the relief valves 21 and 22. In order to improve the responsiveness when controlling the flow rate control valves 71a, 71b and driving the travel motors 8a, 8b, the total required discharge flow rate (Qop14_d+Qop15_d) of the pumps 14, 15 is set when the travel command value of the lever input is not 0. If it is set to the maximum value (2Qopmax), the engine load torque (required torque Tp_d) will rapidly increase due to the above-mentioned rapid pressure rise and increase in the discharge flow rate. Therefore, as shown in FIG. 4, when the travel command value of the lever input is not 0, the rate of change when the total required discharge flow rate (Qop14_d+Qop15_d) of the pumps 14 and 15 changes from the minimum value to the maximum value (2Qopmax) is limited. Thereby, a sudden increase in engine load torque (required torque Tp_d) can be suppressed, and lag down of the engine 9 can be suppressed. This rate of change is the pump discharge pressure when the total required discharge flow rate (Qop14_d + Qop15_d) of the pumps 14 and 15 is set to the maximum value (2Qopmax) when the travel command value of the lever input is not 0 (before restriction). Based on the rising characteristics of Pop14 and Pop15, the increase rate of the required torque Tp_d generated by the pumps 14 and 15 may be set to be equal to or less than the allowable output torque change rate of the engine 9.

Next, in step S6, the controller 50 controls the required discharge flow rate Qop_d (= Qop14_d+Qop15_d). The required discharge flow rate Qop_d' (=Qop14_d'+Qop15_d') after restriction can be obtained, for example, as follows.

With respect to the required torque Tp_d obtained in step S3, the engine 9 can only output up to the allowable output torque Tp_lim, so the total Top_d of the required torque of the third hydraulic pump 14 and the required torque of the fourth hydraulic pump 15 is ,

It is necessary to suppress it so that From formula (2),

becomes. Here, the discharge pressure Pop14 of the third hydraulic pump 14 and the discharge pressure Pop15 of the fourth hydraulic pump 15 are almost equal, and if the required discharge flow rate Qop_d' after restriction is equally allocated to the two pumps 14 and 15. , the required discharge flow rate after restriction of each pump Qop14_d', Qop15_d',

can be asked.

Next, in step S7, the controller 50 controls the discharge flow rate Qop14 of the third hydraulic pump 14 and the fourth The discharge flow rate Qop15 of the hydraulic pump 15 is controlled, and the process ends.

According to the process flow shown in FIG. 5, when the travel command value among the inputs of the lever 51 is increased to the maximum value from time t1 to time t2 shown in FIG. Calculate flow rates Qop14_d and Qop15_d. Next, the controller 50 calculates the equation ( Calculate the required torque Tp_d using 2) and (3).

As shown in FIG. 4, the required torque Tp_d reaches the maximum value from time t1 to time t2, while the allowable output torque Tp_lim of the engine 9 reaches the rated maximum torque of the engine 9 from time t1 to time t3. Assuming this, from time t1 to time t3, the controller 50 uses equation (6) to limit the required discharge flow rates Qop14_d', Qop15_d' so that the required torque Tp_d is equal to or less than the allowable output torque Tp_lim of the engine 9. Calculate.

The controller 50 controls the discharge flow rate Qop14 of the third hydraulic pump 14 and the discharge flow rate Qop15 of the fourth hydraulic pump 15, as shown in FIG. 4, based on the restricted required discharge flow rates Qop14_d' and Qop15_d'. .

By controlling as described above, it becomes possible to operate the excavator without causing the engine 9 to lag down.

In this embodiment, the pumps are started at the same time, but they may be started one by one.

(3) During traveling + boom raising operation Figure 7 shows the lever 51 input during traveling + boom raising combined operation, the opening area of the flow control valves 71a and 71b based on the lever 51 input, and the boom cylinder based on the lever 51 input. 1 required flow rate, each required discharge flow rate of the first and second hydraulic pumps 12 and 13, the total required discharge flow rate of the third and fourth hydraulic pumps 14 and 15, and the boom measured by the pressure sensors 60a and 60b. Head chamber pressure and rod chamber pressure of the cylinder 1, each discharge pressure of the third and fourth hydraulic pumps 14, 15 measured by pressure sensors 72, 73, engine load torque (required torque), first and second fluid 3 shows changes in the discharge flow rates of the pressure pumps 12 and 13 and the discharge flow rates of the third and fourth hydraulic pumps 14 and 15.

From time t0 to time t1, among the inputs of the lever 51, the command value for instructing the extension of the boom cylinder 1 (hereinafter referred to as the boom-up command value) and the travel command value are 0, and the boom cylinder 1 and the travel motor 8a, 8b is stationary.

From time t1 to time t2, among the inputs of the lever 51, the boom raising command value and the travel command value are increased to their maximum values.

FIGS. 8A to 8C are flowcharts showing processing performed by the controller 50 during combined travel operation. Hereinafter, a description will be given focusing on the differences from the processing during the single running operation shown in FIG. 5.

In step S3, the controller 50 calculates the head chamber pressure Pcyl_h and rod chamber pressure Pcyl_r of the boom cylinder 1 measured by the pressure sensors 60a and 60b, and the required discharge flow rate of the first hydraulic pump 12 and the second hydraulic pump 13. From the total required discharge flow rate Qcp_d, the required torque Tp_d that the pump generates when driving the boom cylinder 1 as requested by the lever 51 is calculated.

If it is determined in step S5 that the required torque change rate is not less than the allowable output torque change rate, the process advances to step S6a.

In step S6a, it is determined whether or not the operation is a run-only operation. If it is a run-only operation, the process advances to step S6; otherwise, the process advances to step S8a.

In step S8a, it is determined whether it is a combined operation of traveling, boom, and turning. If it is a combined operation of traveling, boom, and turning, the process advances to step S8b; otherwise, the process advances to step S10a.

In step S8b, the required traveling flow rate is limited so that the required torque of the traveling open circuit pump is equal to or less than a predetermined ratio (first ratio), and the process proceeds to step S8c.

In step S8c, it is determined whether the value obtained by subtracting the required torque of the open-circuit pump for driving after restriction and the required torque for purposes other than driving from the allowable output torque is positive. If it is positive, the process proceeds to step S8d; otherwise, the process proceeds to step S9a.

In step S8d, the required flow rate of actuators other than the travel motors 8a and 8b is calculated from the lever input, and the process proceeds to step S7.

In step S9a, it is determined whether the operation is a combination of boom and turning. If it is a combined boom and turning operation, the process advances to step S9b; otherwise, the process advances to step S9f.

In step S9b, the required turning flow rate is limited so that the required torque of the turning motor 7 is equal to or less than a predetermined ratio (second ratio) to the allowable output torque after travel assignment, and the process proceeds to step S9c.

In step S9c, it is determined whether the value obtained by subtracting the required turning torque after restriction and the required torque other than turning from the allowable output torque after travel assignment is positive. If it is positive, the process proceeds to step S9d; otherwise, the process proceeds to step S9e.

In step S9d, the required flow rate of actuators other than the swing motor 7 is calculated from the lever input, and the process proceeds to step S7.

In step S9e, the required flow rate of the actuators other than the swing motor 7 is limited so that the required speed ratio of each actuator is maintained and the output torque is below the allowable output torque, and the process proceeds to step S7.

In step S9f, each required flow rate is limited so as to be equal to or less than the allowable output torque after travel assignment while maintaining the required speed ratio of each actuator, and the process proceeds to step S7.

In step S10a, it is determined whether or not it is a combined boom and turning operation. If the operation is a combination of boom and turning, the process proceeds to step S10b; otherwise, the process proceeds to step S10f.

In step S10b, the required swing flow rate is limited so that the required torque of the swing motor 7 is equal to or less than a predetermined ratio, and the process proceeds to step S10c.

In step S10c, it is determined whether the value obtained by subtracting the required turning torque after the limit and the required torque other than turning from the allowable output torque is positive. If it is positive, the process proceeds to step S10d; otherwise, the process proceeds to step S10e.

In step S10d, the required flow rate of actuators other than the swing motor 7 is calculated from the lever input, and the process proceeds to step S7.

In step S10e, the required flow rate of the actuators other than the swing motor 7 is limited so that the required speed ratio of each actuator is maintained and the output torque is below the allowable output torque, and the process proceeds to step S7.

In step S10f, each required flow rate is limited so as to be equal to or less than the allowable output torque while maintaining the required speed ratio of each actuator, and the process proceeds to step S7.

According to the processing flow shown in FIGS. 8A to 8C, from time t1 to time t2 shown in FIG. , calculates the required flow rate Qcyl_boom_d of the boom cylinder 1 and the required discharge flow rate Qop_d of the pump that drives the traveling motors 8a and 8b from the input of the lever 51.

Here, the controller 50 allocates the first hydraulic pump 12 and the second hydraulic pump 13 for driving the boom cylinder 1, and allocates the third hydraulic pump 14 and the second hydraulic pump 13 for driving the travel motors 8a and 8b. 4 hydraulic pumps 15 are assigned.

The controller 50 determines the required discharge flow rate Qcp_d of the pump that drives the boom cylinder 1 based on the input Lin from the lever 51 .

In step S3 shown in FIG. 8A, the controller 50 sets the head chamber pressure Pcyl_h and rod chamber pressure Pcyl_r of the boom cylinder 1 measured by the pressure sensors 60a and 60b, and the required discharge flow rate of the first hydraulic pump 12 and the second From the total required discharge flow rate Qcp_d of the hydraulic pump 13, the required torque Tp_d that the pump generates when driving the boom cylinder 1 as requested by the lever 51 is calculated. First, the required torque Tcp_d generated by the closed circuit pump is

becomes. Here, Neng is the engine rotation speed, Ploss is the pressure loss generated in the pipeline from the cylinder to the pump, and ηcp is the pump efficiency of the first hydraulic pump 12 and the second hydraulic pump 13.

The controller 50 calculates the required torque of the first hydraulic pump 12, the second hydraulic pump 13, the third hydraulic pump 14, and the fourth hydraulic pump 15 using equations (2) and (8). Calculate the required torque Tp_d, which is the sum of At this time, the required torque Tp_d is

becomes.

As shown in FIG. 7, the required torque Tp_d increases to the maximum value from time t1 to time t2, while the allowable output torque Tp_lim of the engine 9 reaches the rated maximum torque of the engine 9 from time t1 to time t3. If this is the case, from time t1 to time t3, the controller 50:

The restricted required discharge flow rate Qcp_d' of the pumps 12 and 13 that drive the boom cylinder 1 and the restricted required discharge flow rate Qop_d' of the pumps 14 and 15 that drive the travel motors 8a and 8b are calculated so that

Here, when a general construction machine performs running operation on flat ground, as shown in FIG. 7, the discharge pressures Pop14 and Pop15 of the pumps 14 and 15 are low while running is stopped (time t0 to time t1), and when running is accelerating. It has a characteristic that the speed rises from time t1 to time t3 and becomes constant at a steady speed (from time t3). Particularly when traveling at maximum acceleration, the pump discharge pressures Pop14 and Pop15 rise to the set pressures of the relief valves 21 and 22.

For example, when starting the boom raising operation and traveling at the same time, the required torque of the pumps 14 and 15 that supplies flow to the traveling motors 8a and 8b increases due to a sudden pressure increase during traveling acceleration, and the torque is allocated to the boom cylinder 1. The available torque is reduced and the speed of the boom cylinder 1 may also be reduced.

In order to suppress this, when the boom cylinder 1, the travel motors 8a, 8b, and the swing motor 7 are operated in combination, a certain ratio of torque to be allocated to the travel motors 8a, 8b is ensured. For example, 50% of the torque that the engine can output (allowable output torque Tp_lim) is allocated to the travel motors 8a and 8b. From formula (10),

Then,

becomes.
From equations (8) and (11), the limited required discharge flow rate Qcp_d' of the pump that drives boom cylinder 1 is:

becomes. Here, the discharge pressure of the first hydraulic pump 12 and the discharge pressure of the second hydraulic pump 13 are approximately equal, and if the required discharge flow rate Qcp_d' after restriction is equally allocated to the two pumps 12 and 13, The required discharge flow rate Qcp12_d', Qcp13_d' after restriction of each pump is

becomes. As shown in equation (13), the limited required discharge flow rate Qcp_d' of the pump that drives boom cylinder 1 uses actuator pressure rather than direct pump pressure, so the required discharge flow rate Qcp_d' is the maximum discharge flow rate of each pump. Before connecting the pump to the boom cylinder 1, it can be determined whether or not the above is exceeded. Therefore, the number of pumps may be determined according to the required discharge flow rate Qcp_d'. Thereby, depending on the required discharge flow rate Qcp_d, only one pump can be connected to the boom cylinder 1, so that an empty pump can be secured for driving other actuators. As a result, the number of times the connection destination is switched is reduced, and the delay in starting the operation caused by switching and the pressure shock caused by changing the pump connection destination can be reduced.

Here, the discharge pressure Pop14 of the third hydraulic pump 14 and the discharge pressure Pop15 of the fourth hydraulic pump 15 are almost equal, and the required discharge flow rate Qop_d' after restriction is equally allocated to the two pumps 14 and 15. From equations (2) and (12), the required discharge flow rate Qop14_d' and Qop15_d' after restriction of each pump are as follows.

becomes. If each required discharge flow rate after restriction calculated using equations (13) and (15) exceeds the required discharge flow rate calculated using equations (1) and (7), the surplus torque generated by the difference in flow rate is reallocated. It's okay. Thereby, the torque of the engine 9 can be used efficiently while ensuring a flow rate close to the required flow rate for each actuator.

In step S7, the controller 50 sets the required discharge flow rates Qcp12_d', Qcp13_d' of the pumps 12, 13 that drive the boom cylinder 1 and the required discharge flow rates Qop14_d', Qop15_d' of the pumps 14, 15 that drive the travel motors 8a, 8b. Based on the discharge flow rate Qcp12 of the first hydraulic pump 12, the discharge flow rate Qcp13 of the second hydraulic pump 13, the discharge flow rate Qop14 of the third hydraulic pump 14, and the discharge flow rate Qop15 of the fourth hydraulic pump 15. control.

According to the processing flow shown in FIGS. 8A to 8C, from time t1 to time t2 shown in FIG. , calculates the required discharge flow rate Qcp_d of the pump that drives the boom cylinder 1 and the required discharge flow rate Qop_d of the pump that drives the traveling motors 8a and 8b from the input of the lever 51. Next, the controller 50 calculates each required discharge flow rate, the head chamber pressure of the boom cylinder 1, the rod chamber pressure, the discharge pressure Pop14 of the third hydraulic pump, and the third hydraulic pump. From the discharge pressure Pop15 of the hydraulic pump No. 4, the required torque Tp_d is calculated using equation (9).

As shown in FIG. 7, while the required torque Tp_d reaches its maximum value from time t1 to time t2, it takes from time t1 to time t3 for the allowable output torque Tp_lim of the engine 9 to reach the rated maximum torque of the engine 9. Then, from time t1 to time t3, the controller 50 uses equations (14) and (15) to limit the required discharge flow rate Qcp12_d' so that the required torque Tp_d is equal to or less than the allowable output torque Tp_lim of the engine 9. , Qcp13_d', Qop14_d', Qop15_d' are calculated.

The controller 50 controls the discharge flow rate Qcp12 of the first hydraulic pump 12 and the discharge flow rate Qcp12 of the second hydraulic pump 13, as shown in FIG. The discharge flow rate Qcp13, the discharge flow rate Qop14 of the third hydraulic pump 14, and the discharge flow rate Qop15 of the fourth hydraulic pump 15 are controlled.

The allocation ratio of engine torque to the traveling motors 8a, 8b may be determined from the engine torque usage rate at a steady speed when traveling on flat ground. In addition, since the torque usage rate increases when traveling uphill, as shown in FIG. The required flow rate limiting section 50e may have a function of changing the torque allocation ratio. Thereby, the other actuators can be driven while ensuring the traveling speed even when traveling uphill.

By controlling as described above, it becomes possible to operate the excavator without causing the engine 9 to lag down.

(4) During traveling + boom raising + swinging operation Figure 10 shows the input of the lever 51 during the combined traveling + boom raising + swinging operation, the opening area of the flow control valves 71a and 71b based on the input of the lever 51, and the input of the lever 51. each required flow rate of the boom cylinder 1 and swing motor 7 based on, each required discharge flow rate of the first and second hydraulic pumps 12, 13, the total required discharge flow rate of the third and fourth hydraulic pumps 14, 15, The head chamber pressure and rod chamber pressure of the boom cylinder 1 measured by the pressure sensors 60a and 60b, the respective discharge pressures of the third and fourth hydraulic pumps 14 and 15 measured by the pressure sensors 72 and 73, and the pressure sensors 62a and 62b. The measured port pressure of the swing motor 7, engine load torque (required torque), each discharge flow rate of the first and second hydraulic pumps 12, 13, and each discharge of the third and fourth hydraulic pumps 14, 15 Shows changes in flow rate.

From time t0 to time t1, among the inputs of the lever 51, the boom raising command value, the command value instructing the rotation of the swing motor 7 (hereinafter referred to as the swing command value), and the traveling command value are 0, and the boom cylinder 1, The swing motor 7 and the travel motors 8a, 8b are stationary.

From time t1 to time t2, among the inputs of the lever 51, the boom raising command value, the turning command value, and the traveling command value are increased to their maximum values.

According to the processing flow shown in FIGS. 8A to 8C, from the time t1 to the time t2 shown in FIG. 10, among the inputs of the lever 51, the boom raising command value, the turning command value, and the travel command value are raised to their maximum values. Then, the controller 50 calculates the required flow rate Qcyl_boom_d of the boom cylinder 1, the required flow rate Qsw_d of the swing motor 7, and the required discharge flow rate Qop_d of the pump that drives the traveling motors 8a and 8b from the input of the lever 51.

Here, the controller 50 assigns the first hydraulic pump 12 to drive the boom cylinder 1, assigns the second hydraulic pump 13 to drive the swing motor 7, and assigns the second hydraulic pump 13 to drive the travel motors 8a and 8b. A third hydraulic pump 14 and a fourth hydraulic pump 15 are assigned.

The controller 50 determines the required discharge flow rate Qcp13_d of the pump 13 that drives the boom cylinder 1 based on the input Lin of the lever 51.

In step S3 shown in FIG. 8A, the controller 50 uses the lever a-port pressure Psw_a and b-port pressure Psw_b of the swing motor 7 measured by the pressure sensors 62a and 62b and the required discharge flow rate Qc13p_d of the second hydraulic pump 13. Calculate the required torque Tcp13_d that the pump generates when the swing motor 7 is driven in accordance with the request of 51. The required torque Tcp13_d is

becomes. Here, Neng is the engine rotation speed, Ploss is the pressure loss generated in the pipeline from the cylinder to the pump, and ηcp is the pump efficiency of the second hydraulic pump 13.

The controller 50 uses equations (2), (8), and (17) to control the first hydraulic pump 12, the second hydraulic pump 13, the third hydraulic pump 14, and the fourth hydraulic pump. The total required torque Tp_d of the pump 15 is calculated. At this time, the required torque Tp_d is

becomes.

As shown in FIG. 10, while the required torque Tp_d increases to the maximum value from time t1 to time t2, the allowable output torque Tp_lim of the engine 9 reaches the rated maximum torque of the engine 9 from time t1 to time t3. If this is the case, from time t1 to time t3, the controller 50:

The required discharge flow rate Qcp12_d' that is restricted by the pump 12 that drives the boom cylinder 1, the required discharge flow rate Qcp13_d' that is restricted by the pump 13 that drives the swing motor 7, and the restriction of the pump that drives the traveling motors 8a and 8b. The required discharge flow rate Qop_d' is calculated.

Here, when a general construction machine performs a swing operation on a flat ground, as shown in FIG. 10, while the swing is stopped (time t0 to time t1), the a port pressure and the b port pressure of the swing motor 7 are low, and the swing is accelerated. There is a characteristic that the pressure at one port increases during the period (from time t1 to time t2). Particularly when turning at maximum acceleration, the pressure at one port increases to the set pressure of the relief valves 37a, 37b. Therefore, when a requested speed that exceeds the maximum acceleration is input, if the requested flow rate is supplied from the pump, a part of the flow rate will be exhausted from the relief valve 37a or 37b to the tank 25 and wasted.

For example, when performing control to match the required speed ratio between boom raising and swinging, in the swing motor 7, a part of the flow is discharged from the relief valve 37a or relief valve 37b, and not only does the swinging speed not occur, but the acceleration As the torque required by the swing motor 7 increases at the time, the torque that can be assigned to the boom cylinder 1 may decrease, and the speed of the boom cylinder 1 may also become low.

In order to suppress this, when moving the boom cylinder 1, travel motors 8a, 8b, and swing motor 7 in combination, after securing a certain ratio of torque to be allocated to the travel motors 8a, 8b, the remaining torque is allocated to the swing motor 7. The ratio of torque assigned to the motor 7 is set low. For example, 50% of the torque that the engine 9 can output (allowable output torque Tp_lim) is allocated to the travel motors 8a, 8b, and 20% of the remaining torque is allocated to the swing motor 7. From formula (19),

Then,

becomes. From equations (8) and (21), the restricted required discharge flow rate Qcp12_d' of the pump 12 that drives the boom cylinder 1 is:

becomes. From equations (17) and (22), the restricted required discharge flow rate Qcp13_d' of the pump 13 that drives the swing motor 7 is:

becomes. The restricted required discharge flow rates Qop14_d' and Qop15_d' of the pumps 14 and 15 that drive the travel motors 8a and 8b are obtained from equation (15). If the required discharge flow rate of each pump after restriction calculated using formulas (23), (24), and (15) exceeds the required discharge flow rate determined using formulas (1), (7), and (16), the difference The surplus torque generated by the flow rate may be reallocated to the actuator for which the assigned torque is insufficient. Thereby, the torque of the engine 9 can be used efficiently while ensuring a flow rate close to the required flow rate for each actuator.

In step S7, the controller 50 sets the limited required discharge flow rate Qcp12_d' of the pump 12 that drives the boom cylinder 1, the required discharge flow rate Qcp13_d' of the pump 13 that drives the swing motor 7, and the pump that drives the travel motors 8a and 8b. 14 and 15, the discharge flow rate Qcp12 of the first hydraulic pump 12, the discharge flow rate Qcp13 of the second hydraulic pump 13, and the discharge flow rate of the third hydraulic pump 14. The flow rate Qop14 and the discharge flow rate Qop15 of the fourth hydraulic pump 15 are controlled.

According to the processing flow shown in FIGS. 8A to 8C, from time t1 to time t2 shown in FIG. , from the input of the lever 51, calculate the required discharge flow rate Qcp12_d of the pump that drives the boom cylinder 1, the required discharge flow rate Qcp13_d of the pump that drives the swing motor 7, and the required discharge flow rate Qop_d of the pump that drives the travel motors 8a and 8b. . Next, the controller 50 calculates each required discharge flow rate, the head chamber pressure of the boom cylinder 1 measured by the pressure sensors 60a, 60b, 62a, 62b, 72, 73, the rod chamber pressure, the a port pressure of the swing motor 7, the The required torque Tp_d is calculated from the port pressure, the discharge pressure Pop14 of the third hydraulic pump 14, and the discharge pressure Pop15 of the fourth hydraulic pump 15 using equation (18).

As shown in FIG. 10, while the required torque Tp_d increases to the maximum value from time t1 to time t2, the allowable output torque Tp_lim of the engine 9 reaches the rated maximum torque of the engine 9 from time t1 to time t3. If this is the case, from time t1 to time t3, the controller 50 uses equations (23), (24), and (15) to limit the required torque Tp_d to be less than or equal to the allowable output torque Tp_lim of the engine 9. Calculate the required discharge flow rates Qcp12_d', Qcp13_d', Qop14_d', and Qop15_d'.

The controller 50 adjusts the discharge flow rate Qcp12 of the first hydraulic pump 12 and the discharge flow rate Qcp12 of the second hydraulic pump 13, as shown in FIG. The discharge flow rate Qcp13, the discharge flow rate Qop14 of the third hydraulic pump 14, and the discharge flow rate Qop15 of the fourth hydraulic pump 15 are controlled.

By controlling as described above, it is possible to suppress a significant decrease in the speed of the boom cylinder 1 due to an increase in the pressure of the swing motor 7 at the start of a swing, and to operate the excavator without causing a lag down of the engine 9. become.

In this embodiment, closed-circuit pumps 12 and 13 are double-tilting hydraulic pumps having a pair of inlet and outlet ports, and open-circuit pumps 12 and 13 are single-tilt hydraulic pumps having an inlet port and an outlet port. pumps 14, 15, an engine 9 that drives the closed circuit pumps 12, 13 and open circuit pumps 14, 15, and hydraulic actuators 1, 3, 5, 7 connected to the closed circuit pumps 12, 13 in a closed circuit configuration. , hydraulic motors 8a, 8b connected to the open circuit pumps 14, 15 in an open circuit configuration, and hydraulic motors 8a, 8b provided on flow paths connecting the open circuit pumps 14, 15 and the hydraulic motors 8a, 8b. Flow control valves 71a, 71b that control the direction and flow rate of the pressure oil supplied from 14, 15 to the hydraulic motors 8a, 8b, and each of the hydraulic actuators 1, 3, 5, 7 and the hydraulic motors 8a, 8b. An operating device 51 for instructing the operating direction and each required flow rate, and tilting of the closed circuit pumps 12, 13 and open circuit pumps 14, 15 and flow rate control valves 71a, 71b according to input from the operating device 51. A controller 50 that controls the opening, a first pressure sensor 60a, 60b, 62a, 62b that detects the inlet/outlet pressure of the hydraulic actuators 1, 3, 5, 7, and a first pressure sensor that detects the outlet pressure of the open circuit pumps 14, 15. In the construction machine 100 equipped with two pressure sensors 72 and 73, the controller 50 adjusts the required flow rates of the hydraulic actuators 1, 3, 5, and 7 according to the input from the operating device 51, and the first pressure sensors 60a and 60b. , 62a, 62b, the required discharge flow rate of the open circuit pumps 14, 15 according to the input from the operating device 51, the second pressure sensor 72, Based on the outlet pressures of the open circuit pumps 14 and 15 detected by the 73, the required torque that is the torque required by the closed circuit pumps 12 and 13 and the open circuit pumps 14 and 15 from the engine 9 is calculated, and the required torque is calculated. When the required torque change rate, which is the change rate of limiting at least one discharge flow rate;

According to the present embodiment configured as described above, the required torque change rate, which is the change rate of the torque that the closed circuit pumps 12, 13 and the open circuit pumps 14, 15 request from the engine 9, has a predetermined change rate. If the required torque change rate exceeds the predetermined change rate, the discharge flow rate of at least one of the closed circuit pumps 12, 13 and the open circuit pumps 14, 15 is restricted so that the required torque change rate becomes equal to or less than the predetermined change rate. This makes it possible to suppress lag down of the engine 9, regardless of the operator's operation or the load conditions of the hydraulic actuators 1, 3, 5, and 7.

Further, the closed circuit pumps 12 and 13 are composed of a plurality of closed circuit pumps, the open circuit pumps 14 and 15 are composed of a plurality of open circuit pumps, and the hydraulic actuators 1, 3, 5, and 7 are composed of a plurality of hydraulic actuators. , the hydraulic motors 8a, 8b are composed of a plurality of hydraulic motors, the flow rate control valves 71a, 71b are composed of a plurality of flow rate control valves, and the first pressure sensors 60a, 60b, 62a, 62b are composed of a plurality of first pressure sensors. The second pressure sensors 72 and 73 are composed of a plurality of second pressure sensors, and the controller 50 adjusts each required flow rate of the plurality of hydraulic actuators 1, 3, 5, and 7 according to the input from the operating device 51, A plurality of open circuit pumps 14 according to each inlet/outlet pressure of a plurality of hydraulic actuators 1, 3, 5, 7 detected by a plurality of first pressure sensors 60a, 60b, 62a, 62b and an input from an operating device 51. , 15 and the respective outlet pressures of the plurality of open circuit pumps 14, 15 detected by the plurality of second pressure sensors 72, 72, the plurality of closed circuit pumps 12, 13 and the plurality of A required torque that is the torque that the open circuit pumps 14 and 15 requests from the engine 9 is calculated, and when the required torque change rate that is the change rate of the required torque exceeds a predetermined change rate, the required torque change rate is The discharge flow rate of at least one of the plurality of closed circuit pumps 12, 13 and the plurality of open circuit pumps 14, 15 is restricted so that the rate of change is equal to or less than the predetermined rate of change. As a result, a hydraulic drive device that drives a plurality of hydraulic actuators 1, 3, 5, 7 and a plurality of hydraulic motors 8a, 8b with a plurality of closed circuit pumps 12, 13 and a plurality of open circuit pumps 14, 15 is configured. In the installed construction machine, it is possible to suppress lagdown of the engine 9 regardless of the operator's operation or the load condition of the hydraulic actuator.

Furthermore, the construction machine 100 according to the present embodiment includes a lower traveling body 101, an upper rotating body 102 rotatably attached to the lower traveling body 101, and a working device 103 attached to the upper rotating body 102. The hydraulic actuators 1, 3, 5, and 7 include single-rod cylinders 1, 3, and 5 that drive the working device 103, and a swing motor 7 that drives the upper rotating body 102, and hydraulic motors 8a and 8b. are the traveling motors 8a, 8b that drive the lower traveling body 101, and the controller 50 is in a state where the single rod cylinders 1, 3, 5, the swing motor 7, and the traveling motors 8a, 8b are simultaneously driven. When the required torque change rate exceeds the predetermined change rate, the torque that the open circuit pumps 14 and 15 request from the engine 9 is set to be equal to or less than a predetermined ratio (first ratio) of the allowable output torque of the engine 9. The discharge flow rate of open circuit pumps 14 and 15 is limited. Thereby, when driving the traveling motors 8a, 8b, the single rod cylinders 1, 3, 5 or the swing motor 7 can be driven while preventing the engine 9 from lagging down.

Further, the predetermined ratio (first ratio) is set to 50% or less. Thereby, when driving the travel motors 8a, 8b, it is possible to drive the single rod cylinders 1, 3, 5 or the swing motor 7 with 50% or more of the allowable output torque of the engine 9 while preventing lag down of the engine 9.

Further, the controller 50 controls the controller 50 when the required torque change rate exceeds the predetermined change rate while simultaneously driving the single rod cylinders 1, 3, 5, the swing motor 7, and the travel motors 8a, 8b. , the torque required from the engine 9 by the closed circuit pump connected to the swing motor 7 is 25% (second ratio) or less of the allowable output torque of the engine 9 after the discharge flow rate of the open circuit pumps 14 and 15 is restricted. The discharge flow rate of the closed circuit pumps 12 and 13 is limited so that As a result, when the single rod cylinders 1, 3, 5, the traveling motors 8a, 8b, and the swing motor 7 are being driven simultaneously, 25% or more of the allowable output torque of the engine 9 can be prevented from lagging down in the engine 9. The rod cylinders 1, 3, 5 and the swing motor 7 can be driven.

Furthermore, the construction machine 100 includes an angle sensor 91 that detects the inclination angle of the ground on which the construction machine 100 runs, and the controller 50 adjusts the predetermined ratio (first ratio) according to the inclination angle detected by the angle sensor 91. ) change. Thereby, it is possible to prevent the engine 9 from lagging down, secure the traveling speed when traveling uphill, and drive the other hydraulic actuators 1, 3, 5, and 7.

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 embodiments described above have been described in detail to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described.

1... Boom cylinder (hydraulic actuator), 1a... Head chamber, 1b... Rod chamber, 2... Boom, 3... Arm cylinder (hydraulic actuator), 3a... Head chamber, 3b... Rod chamber, 4... Arm, 5... Bucket cylinder (hydraulic actuator), 5a...head chamber, 5b...rod chamber, 6...bucket, 7...swivel motor (hydraulic actuator), 8a, 8b...travel motor (hydraulic motor), 9...engine, 10... Power transmission device, 11... Charge pump, 12... First hydraulic pump, 12a... Regulator, 13... Second hydraulic pump, 13a... Regulator, 14... Third hydraulic pump, 14a... Regulator, 15... Fourth hydraulic pump, 15a...Regulator, 20...Charging relief valve, 21, 22...Relief valve, 25...Tank, 26, 27, 28a, 28b, 29a, 29b...Charging check valve, 30a, 30b, 31a, 31b, 32a, 32b, 33a, 33b... Relief valve, 34, 35... Flushing valve, 36a, 36b... Charging check valve, 37a, 37b... Relief valve, 38... Flushing valve, 40-47... Switching valve ( control valve), 48, 49...proportional valve, 50...controller, 50a...required flow rate calculation section, 50b...actuator pressure calculation section, 50c...pump pressure calculation section, 50d...required torque calculation section, 50e...required flow rate restriction section, 50f...Command calculation unit, 51...Lever (operating device), 60a, 60b, 62a, 62b...Pressure sensor (first pressure sensor), 71a, 71b...Flow rate control valve, 72, 73...Pressure sensor (second pressure sensor) ), 100... Hydraulic excavator (construction machine), 101... Lower traveling body, 102... Upper revolving body, 103... Working device, 104... Cab, 200-205, 210-213, 215-218... Channel.

Claims (4)

a lower running body;
an upper rotating body rotatably mounted on the lower traveling body;
a working device attached to the upper revolving body;
a plurality of closed circuit pumps that are double tilting hydraulic pumps having a pair of inlet and outlet ports;
a plurality of open circuit pumps that are single tilt hydraulic pumps having inlet ports and outlet ports;
an engine that drives the plurality of closed circuit pumps and the plurality of open circuit pumps;
a plurality of hydraulic actuators connected in a closed circuit to the plurality of closed circuit pumps;
a plurality of hydraulic motors connected in an open circuit to the plurality of open circuit pumps;
A plurality of pumps are provided on flow paths connecting the plurality of open circuit pumps and the plurality of hydraulic motors, and control the direction and flow rate of pressure oil supplied from the plurality of open circuit pumps to the plurality of hydraulic motors. a flow control valve;
an operating device for instructing each operating direction and each required flow rate of the plurality of hydraulic actuators and the plurality of hydraulic motors;
a controller that controls each tilting of the plurality of closed circuit pumps and the plurality of open circuit pumps and each opening of the plurality of flow control valves in accordance with input from the operating device;
a plurality of first pressure sensors that detect respective inlet and outlet pressures of the plurality of hydraulic actuators;
A construction machine comprising a plurality of second pressure sensors that detect outlet pressures of each of the plurality of open circuit pumps,
The plurality of hydraulic actuators include a single rod cylinder that drives the working device, and a swing motor that drives the upper rotating body,
The plurality of hydraulic motors include a travel motor that drives the lower traveling body,
The controller includes:
Each required flow rate of the plurality of hydraulic actuators according to an input from the operating device, each inlet/outlet pressure of the plurality of hydraulic actuators detected by the plurality of first pressure sensors, and the input from the operating device Based on each required discharge flow rate of the plurality of open-circuit pumps according to the plurality of open-circuit pumps and each outlet pressure of the plurality of open-circuit pumps detected by the plurality of second pressure sensors, the plurality of closed-circuit pumps and the Calculating a required torque that is the torque that a plurality of open circuit pumps requests from the engine;
When the required torque change rate, which is the rate of change of the required torque, exceeds a predetermined rate of change while the travel motor, the single rod cylinder, and the swing motor are being driven simultaneously, the motor is connected to the travel motor. limiting the required flow rate of the travel motor such that the torque required by the plurality of open circuit pumps from the engine is equal to or less than a predetermined first percentage of the allowable output torque of the engine;
The required torque of the open circuit pump limited by the restriction of the required flow rate of the travel motor and the required torque of the plurality of closed circuit pumps connected to the single rod cylinder and the swing motor are subtracted from the allowable output torque. If the value is positive, calculate the required flow rate of the single rod cylinder and the swing motor based on the input from the operating device,
The required torque of the open circuit pump limited by the restriction of the required flow rate of the travel motor and the required torque of the plurality of closed circuit pumps connected to the single rod cylinder and the swing motor are subtracted from the allowable output torque. If the value is not positive, the ratio of the required torque of the swing motor to the allowable output torque after allocating the required torque of the open circuit pump limited by the restriction of the required flow rate of the traveling motor is limiting the required flow rate of the swing motor to a predetermined second ratio that is smaller than the ratio, and limiting the required torque of the swing motor;
From the allowable output torque after allocating the required torque of the open circuit pump, which is limited by the restriction of the required flow rate of the travel motor, the required torque of the swing motor, which is limited by the restriction of the required flow rate of the swing motor, and the If the value obtained by subtracting the required torque of the closed circuit pump connected to the single rod cylinder is positive, calculate the required flow rate of the single rod cylinder based on the input from the operating device,
From the allowable output torque after allocating the required torque of the open circuit pump, which is limited by the restriction of the required flow rate of the travel motor, the required torque of the swing motor, which is limited by the restriction of the required flow rate of the swing motor, and the If the value obtained by subtracting the required torque of the closed circuit pump connected to the single rod cylinder is not positive, the allowable output torque is A construction machine characterized in that the discharge flow rate of the closed circuit pump connected to the single rod cylinder is restricted by limiting the required flow rate of the single rod cylinder so that the required flow rate of the single rod cylinder is as follows. The construction machine according to claim 1,
A construction machine, wherein the first ratio is set to 50% or less of the allowable output torque. The construction machine according to claim 2,
The construction machine is characterized in that the second ratio is set to 25% or less of the allowable output torque after allocating the required torque of the open circuit pump limited by the restriction of the required flow rate of the travel motor. . The construction machine according to claim 1,
comprising an angle sensor that detects the inclination angle of the ground on which the construction machine runs;
The construction machine is characterized in that the controller changes the first ratio according to the inclination angle detected by the angle sensor.

Images