WO2014084213A1 - Hydraulic drive device of electric hydraulic machinery - Google Patents

Abstract

In addition to performing load-sensing control of a main pump (2) by rotational frequency control of an electric motor (1) using a controller (50), cutoff control for controlling the rotational frequency of the main pump (2) is performed so as to reduce the discharge flow rate of the main pump (2) when the discharge pressure of the main pump (2) rises above a first specified pressure (P_pso) near the set pressure (P_max) of a main relief valve (14). As a result, in the electric hydraulic machinery, which drives the hydraulic pump using the electric motor to drive an actuator and performs load-sensing control by rotational frequency control of the electric motor, wasted power consumption by the operation of the relief value is limited, sudden elevations in electric motor rotational frequency are limited, and higher efficiency and comfort can be secured.

Description

Hydraulic drive device for electric hydraulic work machine

The present invention relates to a hydraulic drive device of an electric hydraulic work machine such as a hydraulic excavator that drives a hydraulic pump by an electric motor to drive an actuator, and in particular, a discharge pressure of the hydraulic pump is more constant than a maximum load pressure. The present invention relates to a so-called load-sensing hydraulic drive device that controls the discharge flow rate of a hydraulic pump so as to increase only the pressure.

Patent Documents 1 and 2 describe an electric hydraulic working machine such as a hydraulic excavator that performs various operations by driving a hydraulic pump by an electric motor to drive an actuator. The electric hydraulic work machine of Patent Document 1 includes a fixed displacement hydraulic pump driven by an electric motor, and the electric motor is configured so that the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure of a plurality of hydraulic actuators is constant. The load sensing control is performed by controlling the number of rotations.

The electric hydraulic working machine described in Patent Document 2 includes a variable displacement hydraulic pump driven by an electric motor (variable speed motor), and controls the rotational speed of the electric motor and the cutoff control of the regulator of the hydraulic pump (hydraulic pump). When the discharge pressure exceeds a certain pressure, wasteful power consumption is lost when controlling the discharge pressure and discharge flow rate by driving the hydraulic pump with an electric motor by the combination of control that cuts the capacity of the hydraulic pump to almost zero. It can be reduced.

JP 2008-256037 A Japanese Patent Laid-Open No. 2003-172302

In the hydraulic drive device described in Patent Document 1, load sensing control can be performed by controlling the number of revolutions of the motor without using a variable displacement pump that performs complicated flow rate control. Load sensing system can be installed.

However, the hydraulic drive device described in Patent Document 1 has the following problems.

In the hydraulic drive device described in Patent Document 1, for example, when an actuator such as a boom cylinder reaches the stroke end, a relief valve connected to the pressure oil supply oil path from the hydraulic pump functions to cause the pressure oil supply oil path to Pressure oil is discharged into the tank, and the discharge pressure of the hydraulic pump is maintained at the set pressure (relief pressure) of the relief valve.

However, since the pressure oil discharged from the relief valve does not work, if the pressure of the pressure oil supply oil passage maintained by the relief valve is P and the flow rate flowing out of the pressure oil supply oil passage to the tank is Q, P [ The power represented by [MPa] × Q [L / min] / 60 has been unnecessarily converted into heat and sound and consumed. At this time, since the power consumption for cooling the motor increases, the amount of discharge of the battery (power storage device) that is the power source of the motor increases, the battery is quickly depleted, and the operation time of the work machine is shortened. was there. In addition, there is a problem that the power consumed in vain changes to heat, and the capacity of the hydraulic oil cooling system cannot be reduced.

Further, since the hydraulic drive device of Patent Document 1 is configured to perform only load sensing control by controlling the rotational speed of the electric motor, for example, when an actuator such as a boom cylinder reaches the stroke end as described above, the hydraulic pump The pressure difference between the discharge pressure and the maximum load pressure becomes almost zero, and the rotational speed of the motor is controlled so that the differential pressure becomes equal to the target differential pressure. As a result, the discharge flow rate of the hydraulic pump increases to the maximum, and the flow rate that flows out from the relief valve to the tank also increases to the maximum. Therefore, the above-mentioned problem (operation of the work machine due to an increase in the battery discharge amount due to the occurrence of unnecessary power consumption) The reduction in time and the increase in hydraulic oil cooling system capacity) are particularly significant.

Moreover, every time an actuator such as a boom cylinder reaches the stroke end, the motor speed rapidly increases up to the maximum speed, and uncomfortable noise and vibration accompanying the sudden increase in motor speed impairs operator comfort. There was a problem.

On the other hand, in the hydraulic unit described in Patent Document 2, since the discharge flow rate of the hydraulic pump is finally reduced to a flow rate that compensates for the leakage amount from the hydraulic unit, an extremely efficient system can be constructed. . However, load sensing control for controlling the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure of each actuator to be constant is not assumed as the flow rate control. Similar to the first embodiment, for example, every time the hydraulic cylinder reaches the stroke end, the motor rotation speed rapidly increases to the maximum rotation speed, and the operator's comfort due to unpleasant noise and vibration accompanying the rapid increase in the motor rotation speed. There was a problem that was damaged.

An object of the present invention is to reduce wasteful power consumption due to relief valve operation in an electric hydraulic working machine that drives a hydraulic pump by an electric motor to drive an actuator and performs load sensing control by controlling the rotational speed of the electric motor, and An object of the present invention is to provide a hydraulic drive device for an electric hydraulic working machine that can suppress a sudden increase in the number of revolutions of the electric motor and can ensure comfort with higher efficiency.

(1) In order to achieve the above object, the present invention includes an electric motor, a hydraulic pump driven by the electric motor, a plurality of actuators driven by pressure oil discharged from the hydraulic pump, and the hydraulic pump. A plurality of flow rate control valves for controlling the flow rate of pressure oil supplied to the plurality of actuators, and a pressure oil supply oil passage for supplying discharge oil of the hydraulic pump to the plurality of flow rate control valves; Hydraulic drive of an electric hydraulic work machine having a relief valve that opens when the discharge pressure exceeds a set pressure and returns the pressure oil in the pressure oil supply oil passage to the tank, and a power storage device that supplies electric power to the electric motor Load sensing control for controlling the rotational speed of the hydraulic pump so that a discharge pressure of the hydraulic pump is higher than a maximum load pressure of the plurality of actuators by a target differential pressure in the apparatus Cut-off control for controlling the number of revolutions of the hydraulic pump so as to reduce the discharge flow rate of the hydraulic pump when the discharge pressure of the hydraulic pump rises to a first predetermined pressure or more near a set pressure of the relief valve; And an electric motor rotation speed control device for performing the above.

In this way, not only the load sensing control but also the hydraulic speed control device is configured to reduce the hydraulic pump discharge flow rate when the discharge pressure of the hydraulic pump rises above the first predetermined pressure near the set pressure of the relief valve. By performing cut-off control for controlling the number of revolutions of the pump, a plurality of actuators include a hydraulic cylinder, and when this hydraulic cylinder reaches the stroke end, the flow rate discharged from the hydraulic pump can be suppressed. Therefore, it is possible to suppress the power that is wasted from the relief valve. As a result, since the power consumption of the electric motor is reduced, the power storage device that is the electric power source of the electric motor can be prolonged, and the operating time of the electric hydraulic working machine can be extended. Furthermore, since the heat generation during the operation of the relief valve is reduced, the hydraulic oil cooling system can be downsized.

In addition, when the hydraulic cylinder reaches the stroke end, it is possible to suppress an increase in the rotation speed of the motor, thereby suppressing an increase in noise and vibration accompanying an increase in the rotation speed of the motor and impairing operator comfort. Can be prevented.

(2) In the above (1), preferably, the motor rotation speed control device includes a first pressure sensor that detects a discharge pressure of the hydraulic pump, a second pressure sensor that detects the maximum load pressure, and the electric motor. An inverter for controlling the rotation speed of the hydraulic pump, and a controller, the controller based on the discharge pressure of the hydraulic pump detected by the first and second pressure sensors, the maximum load pressure, and the target LS differential pressure, A load sensing control calculation unit that calculates a virtual capacity of the hydraulic pump that increases or decreases according to the positive or negative of the differential pressure difference between the pressure difference between the discharge pressure of the hydraulic pump and the maximum load pressure and the target LS differential pressure; Based on the discharge pressure of the hydraulic pump detected by the first pressure sensor, when the discharge pressure of the hydraulic pump rises above the first predetermined pressure, the virtual capacity of the cut-off control suddenly decreases. A capacity limit control calculation unit that calculates a limit value, and selects a virtual capacity calculated by the load sensing control calculation unit and a smaller limit value of the virtual capacity to obtain a new virtual capacity, and the controller Calculates a target flow rate of the hydraulic pump by multiplying the new virtual capacity by the reference rotational speed, and a control command for controlling the rotational speed of the electric motor so that the discharge flow rate of the hydraulic pump becomes the target flow rate Is output to the inverter.

In this way, the concept of the virtual capacity of the hydraulic pump is introduced into the load sensing control calculation unit, the target flow rate of the load sensing control is obtained, and the rotation speed of the motor is controlled to perform load sensing control by controlling the rotation speed of the motor. be able to. In addition, the virtual capacity limit value of the cutoff control is calculated in the capacity limit control calculation unit, and the virtual capacity calculated in the load sensing control calculation unit and the smaller one of the virtual capacity limit values are selected to obtain a new virtual capacity. In other words, by controlling the rotation speed of the electric motor, it is possible to easily realize cut-off control by controlling the rotation speed of the electric motor.

(3) In the above (1), preferably, when the discharge pressure of the hydraulic pump is in a pressure range not less than a second predetermined pressure and not more than the first predetermined pressure, the discharge pressure of the hydraulic pump increases as the discharge pressure increases. A torque control device is further provided for controlling the absorption torque of the hydraulic pump so as not to exceed a preset maximum torque by reducing the discharge flow rate of the hydraulic pump.

Thus, in addition to performing load sensing control and cut-off control by the motor rotation speed control device, a torque control device is provided, and the discharge pressure of the hydraulic pump is in the pressure range from the second predetermined pressure to the first predetermined pressure. When the discharge pressure of the hydraulic pump rises by performing torque control to reduce the discharge flow rate of the hydraulic pump and limit the absorption torque of the hydraulic pump as the discharge pressure of the hydraulic pump rises, Even before the cut-off control by is started, the horsepower consumed by the hydraulic pump can be suppressed by the torque control that limits the absorption torque of the hydraulic pump. As a result, the power consumption of the electric motor is reduced, so that the power storage device that is the electric power source of the electric motor can be further extended, and the operating time of the electric hydraulic working machine can be further extended. In addition, since the power consumption of the electric motor is reduced, the electric motor can be reduced in size.

(4) In the above (2), preferably, the hydraulic pump is a variable displacement hydraulic pump, and is provided in the hydraulic pump. When the discharge pressure of the hydraulic pump rises, the discharge flow rate of the hydraulic pump is increased. A torque control device is further provided for controlling the absorption torque of the hydraulic pump so that the absorption torque does not exceed a preset maximum torque.

This makes it possible to easily realize load sensing control, cut-off control, and torque control by controlling the rotational speed of the motor using a normal hydraulic pump having a torque control function.

(5) In the above (2), preferably, the hydraulic pump is a fixed displacement hydraulic pump, and is incorporated as a function of the controller, and when the discharge pressure of the hydraulic pump rises, the discharge of the hydraulic pump A torque control device is further provided for controlling the absorption torque of the hydraulic pump so as not to exceed a preset maximum torque by reducing the flow rate.

This enables load sensing control, cut-off control, and torque control, and the hydraulic pump is a fixed displacement type, so the size of the hydraulic pump can be kept small and space can be saved.

(6) In the above (2), preferably, the hydraulic pump is a fixed displacement hydraulic pump, and the capacity restriction control calculation unit is based on a discharge pressure of the hydraulic pump detected by the first pressure sensor. When the discharge pressure of the hydraulic pump is in a pressure range that is greater than or equal to a second predetermined pressure and less than or equal to the first predetermined pressure, the limit value of the virtual capacity of torque limit control that decreases as the discharge pressure of the hydraulic pump increases When the discharge pressure of the hydraulic pump rises above the first predetermined pressure, the virtual capacity limit value of the cutoff control that suddenly decreases from the virtual capacity limit value of the torque limit control is calculated, and the load sensing control The virtual capacity calculated by the calculation unit and the smaller one of the limit values of the virtual capacity are selected to obtain a new virtual capacity.

As a result, load sensing control, cut-off control, and torque control by motor rotation speed control can be realized, and the hydraulic pump is a fixed displacement type, so the size of the hydraulic pump can be kept small and space can be saved. Can do.

(7) In the above (2), preferably, an operation device for instructing the reference rotation speed is further provided, and the controller sets the reference rotation speed based on an instruction signal of the operation device, and the reference rotation Based on the number, the target LS differential pressure and the target flow rate corresponding to the magnitude of the reference rotational speed are calculated.

As a result, when the operator operates the operating device to reduce the reference rotational speed, the target LS differential pressure and the target flow rate are reduced, so that the change in the rotational speed of the motor and the rotational speed are reduced, and good fine operability is obtained. be able to.

In an electric hydraulic work machine that drives a hydraulic pump by an electric motor to drive an actuator and performs load sensing control by controlling the rotational speed of the electric motor, wasteful power consumption due to the relief valve operation is suppressed, and the electric motor rotational speed is rapidly increased. The rise can be suppressed, and comfort can be ensured with higher efficiency. In addition, since the electric power consumption of the electric motor is reduced, the power storage device that is the electric power source of the electric motor can be prolonged, and the operating time of the electric hydraulic working machine can be extended. Furthermore, since the heat generation during the operation of the relief valve is reduced, the hydraulic oil cooling system can be downsized.

It is a figure which shows the structure of the hydraulic drive device of the electrically driven hydraulic working machine in the 1st Embodiment of this invention. It is a functional block diagram which shows the processing content of a controller. It is a figure which shows the characteristic (cut-off control characteristic) which simulated the cut-off control set to a calculating part. 2 is a pump torque characteristic (Pq characteristic: pump discharge pressure-pump capacity characteristic) of the torque control device). It is a figure which shows the external appearance of the hydraulic excavator by which the hydraulic drive device in this Embodiment is mounted. It is a figure which shows the horsepower characteristic of the hydraulic drive device which performs load sensing control by the conventional motor rotation speed control. It is a figure which shows the horsepower characteristic of the hydraulic drive device of this Embodiment. It is a figure which shows the structure of the hydraulic drive device of the electrically driven hydraulic working machine in the 2nd Embodiment of this invention. It is a functional block diagram which shows the processing content of a controller. It is a figure which shows the characteristic which combined the characteristic (torque control characteristic) which simulates the torque control set to a calculating part, and the characteristic (cutoff control characteristic) which simulated cutoff control. It is a figure which shows the torque characteristic of a main pump.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

~ Configuration ~
FIG. 1 is a diagram showing a configuration of a hydraulic drive device for an electric hydraulic work machine according to a first embodiment of the present invention. In the present embodiment, the present invention is applied to a hydraulic drive device of a front swing type hydraulic excavator.

In FIG. 1, a hydraulic drive apparatus according to the present embodiment includes an electric motor 1, a variable displacement hydraulic pump (hereinafter referred to as a main pump) 2 as a main pump driven by the electric motor 1, and a fixed displacement pilot pump. 30, a plurality of actuators 3 a, 3 b, 3 c... Driven by pressure oil discharged from the main pump 2, and a control valve 4 positioned between the main pump 2 and the plurality of actuators 3 a, 3 b, 3 c. A pilot hydraulic power source 38 that is connected to the pilot pump 30 via a pilot oil passage 31 and generates a pilot primary pressure based on the oil discharged from the pilot pump 30; and a downstream side of the pilot hydraulic power source 38, and a gate lock lever And a gate lock valve 100 as a safety valve operated by the control unit 24.

The control valve 4 includes a second pressure oil supply oil passage 4a (internal passage) connected to a first pressure oil supply oil passage 2a (piping) to which discharge oil of the main pump 2 is supplied, and a second pressure oil supply oil. A plurality of closed center type flow rate controls connected to the oil passages 8a, 8b, 8c... Branching from the passage 4a and controlling the flow rate and direction of the pressure oil supplied from the main pump 2 to the actuators 3a, 3b, 3c. Are connected to the oil passages 25a, 25b, 25c,... That connect the valves 6a, 6b, 6c,... And the meter-in throttle portions of the flow control valves 6a, 6b, 6c,. The pressure compensation valves 7a, 7b, 7c,... For controlling the downstream pressure of the meter-in throttle section to be equal to the maximum load pressure (described later), and the maximum pressure (maximum) among the load pressures of the actuators 3a, 3b, 3c,. load ) Are selected and output to the signal oil passage 27, and connected to the second pressure oil supply oil passage 4a and the pressure of the second pressure oil supply oil passage 4a (discharge of the main pump 2) When the pressure (pressure) exceeds a set pressure, the pressure oil in the pressure oil supply oil passage is opened and the pressure oil in the second pressure oil supply oil passage 4a (discharge pressure of the main pump 2) exceeds the set pressure. It is connected to a main relief valve 14 that restricts so that it does not become, and a second pressure oil supply oil passage 4a that is an oil passage through which the discharge oil of the main pump 2 is guided, and the discharge pressure of the main pump 2 is increased to the maximum load pressure and the cracking pressure ( An unloading valve 15 that opens when the pressure higher than the set pressure of the spring 15a) returns to the tank T and restricts the increase in the discharge pressure of the main pump 2. ing.

The flow control valves 6a, 6b, 6c... Have load ports 26a, 26b, 26c..., Respectively, and these load ports 26a, 26b, 26c... Are when the flow control valves 6a, 6b, 6c. Communicates with the tank T and outputs a tank pressure as a load pressure. When the flow control valves 6a, 6b, 6c... Are switched from the neutral position to the left and right operation positions in the figure, the respective actuators 3a, 3b, 3c. To output the load pressure of the actuators 3a, 3b, 3c.

The shuttle valves 9a, 9b, 9c... Are connected in a tournament form, and constitute the maximum load pressure detection circuit together with the load ports 26a, 26b, 26c. That is, the shuttle valve 9a selects and outputs the high pressure side of the pressure of the load port 26a of the flow control valve 6a and the pressure of the load port 26b of the flow control valve 6b, and the shuttle valve 9b outputs the output pressure of the shuttle valve 9b. And the pressure of the load port 26c of the flow control valve 6c are selected and output, and the shuttle valve 9c outputs the high pressure side of the output pressure of the shuttle valve 9b and the output pressure of another similar shuttle valve (not shown). Select and output. The shuttle valve 9c is the last stage shuttle valve, and its output pressure is output to the signal oil passage 27 as the maximum load pressure, and the maximum load pressure output to the signal oil passage 27 passes through the signal oil passages 27a, 27b, 27c. Through the pressure compensation valves 7a, 7b, 7c... And the unload valve 15.

The pressure compensating valves 7a, 7b, 7c,... Are pressure-receiving portions 21a, 21b, 21c, etc., which are operated in the closing direction, in which the highest load pressure is guided from the shuttle valve 9c via the signal oil passages 27, 27a, 27b, 27c,. It has pressure-receiving parts 22a, 22b, 22c ... of the opening direction operation to which the downstream pressure of the meter-in throttle part of the control valves 6a, 6b, 6c ... is guided, and the downstream pressure of the meter-in throttle part of the flow control valves 6a, 6b, 6c ... Is controlled to be equal to the maximum load pressure. As a result, the differential pressure across the meter-in throttle portion of the flow control valves 6a, 6b, 6c... Is controlled to be equal to the differential pressure between the discharge pressure of the main pump 2 and the maximum load pressure.

The unload valve 15 is operated in the open direction in which the closing direction spring 15a that sets the cracking pressure Pun0 of the unload valve 15 and the pressure in the second pressure oil supply oil passage 4a (the discharge pressure of the main pump 2) is guided. A pressure receiving portion 15b and a pressure receiving portion 15c that operates in the closing direction in which the maximum load pressure is guided through the signal oil passage 27. The pressure of the pressure oil supply oil passage 4a is set to the maximum load pressure and the set pressure Pun0 ( When the pressure becomes higher than the cracking pressure, the pressure oil in the pressure oil supply oil passage 4a is returned to the tank T and the pressure in the pressure oil supply oil passage 4a (the discharge pressure of the main pump 2) is set to the maximum load pressure. The pressure is controlled by adding the set pressure of the spring 15a and the pressure generated by the override characteristic of the unload valve 15. The override characteristic of the unload valve is a characteristic in which the inlet pressure of the unload valve, that is, the pressure of the pressure oil supply oil passage 4a increases as the flow rate of the pressure oil that returns to the tank via the unload valve increases. . In the present specification, a pressure obtained by adding the set pressure of the spring 15a and the pressure generated by the override characteristic of the unload valve 15 to the maximum load pressure is referred to as an unload pressure.

Actuators 3a, 3b, and 3c are, for example, boom cylinders, arm cylinders, and swing motors of hydraulic excavators, and flow control valves 6a, 6b, and 6c are, for example, flow control valves for booms, arms, and swings. For the convenience of illustration, illustration of other actuators such as bucket cylinders, swing cylinders, travel motors, and flow control valves related to these actuators is omitted.

The pilot hydraulic power source 38 is connected to the pilot oil passage 31 and has a pilot relief valve 32 that keeps the pressure of the pilot oil passage 31 constant. The gate lock valve 100 can be switched between a position where the pilot oil passage 31 a is connected to the pilot oil passage 31 and a position where the pilot oil passage 31 a is connected to the tank T by operating the gate lock lever 24.

In the pilot oil passage 31a, operating lever devices 122 and 123 for generating command pilot pressures (command signals) for operating the corresponding actuators 3a, 3b, 3c... By operating the flow control valves 6a, 6b, 6c. , 124 (see FIG. 5) are connected. When the gate lock lever 24 is switched to a position where the pilot oil passage 31 a is connected to the pilot oil passage 31, the operation lever devices 122, 123, and 124 are operated according to the operation amount of each operation lever. The command pilot pressure (command signal) is generated using the hydraulic pressure of the engine as the primary pressure. On the other hand, when the gate lock valve 100 is switched to a position where the pilot oil passage 31a is connected to the tank T, the operating lever devices 122, 123, and 124 are incapable of generating command pilot pressure even if the operating lever is operated. .

In addition to the above-described configuration, the hydraulic drive device according to the present embodiment includes a battery 70 (power storage device) serving as a power source for the electric motor 1, a chopper 61 that boosts DC power of the battery 70, and DC power boosted by the chopper 61. An inverter 60 that converts AC power and supplies it to the electric motor 1, a reference rotational speed instruction dial 51 (operating device) that is operated by an operator and indicates the reference rotational speed of the electric motor 1, and a pressure oil supply oil passage 4 a of the control valve 4. , A pressure sensor 40 that detects the discharge pressure of the main pump 2, a pressure sensor 41 that is connected to the signal oil passage 27 and detects the maximum load pressure, an indication signal of the reference rotation speed indication dial 51, and the pressure sensor 40. , 41, and a controller 50 for controlling the inverter 60.

FIG. 2 is a functional block diagram showing the processing contents of the controller 50.

The controller 50 has the functions of the calculation units 50a to 50m.

The calculation units 50a and 50b _receive the detection signals V _PS and V _PLmax of the pressure sensors 40 and 41, respectively, and _convert these values into the discharge pressure P _PS and the maximum load pressure P _PLmax of the main pump 2, respectively. Next, the computing unit 50c calculates the actual load sensing differential pressure P _LS (= P _PS −P _PLmax ) by taking the difference between the pressure P _PS and the pressure P _PLmax . Subsequently, the calculation unit 50d has an instruction signal V _EC reference rotation speed instruction dial 51 is converted to the reference rotation speed N _0, the arithmetic unit 50e converts the reference rotational speed N ₀ in the target LS differential pressure P _GR.

Calculation unit 50f calculates the difference pressure deviation ΔP of the target LS differential pressure P _GR and the actual load sensing differential pressure P _LS. The calculation unit 50g calculates an increase / decrease value Δq of the virtual capacity q * of the main pump 2 from the differential pressure deviation ΔP. The calculation unit 50g is configured such that the virtual capacity change amount Δq increases as ΔP increases. The increase / decrease value Δq is calculated so as to be a positive value when ΔP is positive and to be a negative value when ΔP is negative. The calculation unit 50h calculates the current virtual capacity q * by adding the increase / decrease value Δq to the virtual capacity q * one calculation cycle before.

Here, the virtual capacity q * of the main pump 2 is the capacity of the main pump 2 for controlling the actual load sensing differential pressure P _LS to match the target LS differential pressure P _GR by controlling the rotational speed of the electric motor 1. Calculated value.

The calculation unit 50r has a table in which characteristics (hereinafter simply referred to as cut-off control characteristics) for simulating cut-off control of the discharge pressure of the main pump 2 are set, and the main pump 2 converted by the calculation unit 50a is included in the calculation unit 50r. The discharge pressure P _PS is input, and the calculation unit 50r calculates the limit value (maximum virtual capacity) q * limit of the virtual capacity q * of the cutoff control with reference to the discharge pressure P _PS of the main pump 2 in the table. .

FIG. 3 is a diagram illustrating characteristics (cut-off control characteristics) simulating cut-off control set in the calculation unit 50r.

The cut-off control characteristic set in the calculation unit 50r is a characteristic corresponding to the maximum capacity characteristic line TP0 (see FIG. 4) of the main pump 2 when the discharge pressure of the main pump 2 is lower than the preset set value P _pso . It consists of TP0r1 and a cutoff control characteristic TP3 when the discharge pressure of the main pump 2 exceeds the set value P _pso . The limit value q * limit in the characteristic TP0r1 is constant at the maximum capacity q _max of the main pump 2. The cut-off control characteristic TP3 is set so that the limit value q * limit is steeply and linearly reduced from q _max to the minimum value q * limit 0 from the set value P _pso to the maximum discharge pressure P _max . The maximum discharge pressure P _max of the main pump 2 is a set pressure (relief pressure) of the main relief valve 14. The set value P _pso is higher than the start pressure P ₀ (described later) of the constant absorption torque control and is a pressure close to the maximum discharge pressure P _max . The minimum value q * limit0 is a small volume close to the minimum capacity q _min of the main pump 2. The minimum value q * limit0 may be the same as the minimum capacity q _min of the main pump 2.

The calculation unit 50s selects a smaller one of the load sensing control virtual capacity q * calculated by the calculation unit 50h and the limit value q * limit of the virtual capacity q * obtained by the calculation unit 50r, and creates a new virtual capacity q *. Output as *. Here, when the virtual capacity q * of the load sensing control and the limit value q * limit of the virtual capacity are the same value, one of them, for example, the virtual capacity q * of the load sensing control is selected in advance as a rule. Is established.

The calculation unit 50i allows the obtained new virtual capacity q ** to fall within the range of the minimum capacity q _min and the maximum capacity q _max of the main pump 2 (not less than the minimum capacity q _min and more than the maximum capacity q _max Process to limit so that it does not become.

Calculation unit 50j multiplies the reference rotational speed N ₀ in the virtual capacity q ** obtained, to calculate a target flow rate Q _d of the main pump 2. Calculating unit 50k is divided by the target flow rate Q _d at maximum capacity q _max of the main pump 2, to calculate a target rotational speed N _d of the main pump 2. The calculation unit 50m converts the target rotational speed _Nd into a command signal (voltage command) V _INV that is a control command for the inverter 60, and outputs the command signal V _INV to the inverter 60.

The above-described function of the controller 50, the inverter 60, and the pressure sensors 40 and 41 rotate the main pump 2 so that the discharge pressure of the main pump 2 is higher by the target differential pressure than the maximum load pressure of the plurality of actuators 3a, 3b, 3c. When the discharge pressure of the main pump 2 and the discharge pressure of the main pump 2 rise above the first predetermined pressure P _pso near the set pressure P _max of the main relief valve 14, the discharge flow rate of the main pump 2 is decreased. An electric motor rotation speed control device 200 that performs cut-off control for controlling the rotation speed of the main pump 2 is configured.

The calculation units 50a to 50c and 50f to 50h of the controller 50 are based on the discharge pressure P _PS and the maximum load pressure P _{PLmax of} the main pump 2 and the target LS differential pressure P _GR detected by the pressure sensors 40 and 41, respectively. Load sensing control for calculating the virtual capacity q * of the main pump 2 that increases or decreases according to the positive or negative of the differential pressure deviation ΔP between the differential pressure P _LS between the discharge pressure of the main pump 2 and the maximum load pressure and the target LS differential pressure P _GR The calculation unit 201 is configured.

Based on the discharge pressure of the main pump 2 detected by the pressure sensor 40, the calculation units 50r and 50s of the controller 50 have a first predetermined pressure P _{pso that} the discharge pressure of the main pump 2 is close to the set pressure P _max of the main relief valve 14. Calculate the virtual capacity limit value q * limit of the cutoff control that suddenly decreases when it rises above, and select the smaller one of the virtual capacity q * and virtual capacity limit value q * limit calculated by the load sensing control calculation unit A capacity limit control calculation unit 202 for obtaining the virtual capacity q ** is configured.

Returning to FIG. 1, the hydraulic drive device of the present embodiment is provided in the main pump 2, and the capacity of the main pump 2 is reduced as the discharge pressure of the main pump 2 increases, and the absorption torque of the main pump 2 is set in advance. The torque control device 17 for controlling the maximum torque so as not to exceed the maximum torque is provided. The torque control device 17 is a regulator provided in the main pump 2, and has a torque control tilt piston 17a and springs 17b1 and 17b2 to which the discharge pressure of the main pump 2 is guided through an oil passage 17c.

FIG. 4 shows pump torque characteristics (Pq characteristics: pump discharge pressure-pump capacity characteristics) of the torque control device 17). The horizontal axis indicates the discharge pressure of the main pump 2, and the vertical axis indicates the capacity of the main pump 2. Further, TP0 the maximum capacity characteristic line of the main pump 2, TP1 and TP2 are characteristic of the torque control that is set by the spring 17b1,17b2, _{P 0} is the second predetermined pressure (absorption torque determined by the spring 17B1,17b2 Constant control starting pressure).

Torque control tilting piston 17a of the torque control device 17 is not operated when the discharge pressure of the main pump 2 is below a second predetermined pressure P _0, the maximum capacity q _max on the capacity of the main pump 2 is characteristic lines TP0 It is in. When the discharge pressure of the main pump 2 rises and exceeds the second predetermined pressure P ₀ , the torque control tilt piston 17a of the torque control device 17 operates, and the discharge pressure of the main pump 2 changes from the second predetermined pressure P ₀ to the main pressure. While the pump 2 reaches the maximum discharge pressure P _max (set pressure of the main relief valve 14), the capacity of the main pump 2 decreases from q _max to qlimit-min along the characteristic lines TP1 and TP2. As a result, the absorption torque (product of pump discharge pressure and capacity) of the main pump 2 is controlled to a substantially constant value so as not to exceed the maximum torque (limit torque) TM in contact with the characteristic lines TP1 and TP2. This control is referred to as torque limit control in this specification, and control in terms of characteristics in which the displacement of the hydraulic pump is replaced with discharge flow rate is referred to as horsepower control. The magnitude of the maximum torque TM can be freely set in advance by selecting the strength of the springs 17b1 and 17b2.

That is, when the discharge pressure of the main pump 2 is within the pressure range (within the range P ₀ to P _pso ) of the second predetermined pressure P ₀ or more and the first predetermined pressure P _pso or less shown in FIG. In addition, the main pump 2 is controlled so that the absorption torque of the main pump 2 does not exceed a preset maximum torque by decreasing the discharge flow rate of the main pump 2 as the discharge pressure of the main pump 2 increases.

FIG. 5 is a diagram showing an external appearance of a hydraulic excavator on which the hydraulic drive device according to the present embodiment is mounted.

In FIG. 5, a hydraulic excavator well known as a work machine includes an upper swing body 300, a lower traveling body 301, and a swing-type front work machine 302. The front work machine 302 includes a boom 306, an arm 307, The bucket 308 is configured. The upper turning body 300 can turn the lower traveling body 301 by the rotation of the turning motor 3c shown in FIG. A swing post 303 is attached to the front portion of the upper swing body 300, and a front work machine 302 is attached to the swing post 303 so as to move up and down. The swing post 303 can be rotated in the horizontal direction with respect to the upper swing body 300 by expansion and contraction of a swing cylinder (not shown). The boom 306, the arm 307, and the bucket 308 of the front work machine 302 are the boom cylinder 3a, the arm cylinder 3b, and the bucket. The cylinder 12 can be turned up and down by expansion and contraction. A blade 305 that moves up and down by the expansion and contraction of a blade cylinder 304 is attached to the lower frame 301 in the center frame. The lower traveling body 301 travels by driving the left and right crawler belts 310 and 311 by the rotation of the traveling motors 6 and 8. In FIG. 1, only the boom cylinder 3a, the arm cylinder 3b, and the turning motor 3c are shown, and the bucket cylinder 3d, the left and right traveling motors 3f and 3g, the blade cylinder 3h, and their circuit elements are omitted.

A cabin (driver's cab) 313 is installed in the upper swing body 300, and in the cabin 313, there is a driver seat 121, front / turning operation lever devices 122 and 123 (only the right side is shown in FIG. 5), and driving operation. A lever device 124 and a gate lock lever 24 are provided.

~ Operation ~
Next, the operation of the present embodiment will be described.

<When the control lever is neutral>
When all the operation devices including the operation levers of the operation lever devices 122, 123, and 124 are in the neutral position, the flow control valves 6a, 6b, 6c,... Are all in the neutral position. Therefore, the load ports 26a, 26b, 26c... Of the actuators 3a, 3b, 3c... Are connected to the tanks, respectively, and the maximum load pressure of the actuators 3a, 3b, 3c. It becomes equal to the tank pressure. The pressure sensor 41 detects this tank pressure.

On the other hand, the main pump 2 is driven by the electric motor 1, and the pressure oil is supplied to the pressure oil supply oil passages 2a and 4a. The flow rate control valves 6a, 6b, 6c,..., The main relief valve 14, and the unload valve 15 are connected to the pressure oil supply oil passage 4a. When all the control levers are neutral, the flow rate control valves 6a, 6b, 6c,... Are closed, so that the discharge pressure of the main pump 2 is a pressure obtained by adding the override characteristic pressure to the set pressure of the spring 15a of the unload valve 15. To rise.

Here, the set pressure of the unload valve 15 is set to be constant by the spring 15a, and the set pressure is the target LS differential pressure P _GR calculated by the calculation unit 50e when the reference rotational speed N ₀ is maximum. It is set higher than. For example, if the target LS differential pressure _PGR is 2 MPa, the set pressure of the spring 15a is about 2.5 MPa, and the discharge pressure (unload pressure) of the main pump 2 is also approximately 2.5 MPa. The pressure sensor 40 connected to the pressure oil supply oil passage 4a detects the discharge pressure of the main pump 2. The discharge pressure of the main pump 2 at this time is represented by _Pmin .

As described above, the detection signal of the pressure sensor 40 is V _PS and the detection signal of the pressure sensor 41 is V _PLmax . The controller 50 calculates the virtual capacity q * of the main pump 2 based on the detection signals V _PS and V _PLmax of the pressure sensors 40 and 41 and the instruction signal V _EC of the reference rotation speed instruction dial 51 in the arithmetic units 50a to 50h. .

The controller 50, the arithmetic unit 50r, the virtual capacity q * limit value q * limit the discharge pressure P _PS of the main pump 2 obtained in the calculating portion 50a by a table which sets the characteristic to simulate the cut-off control characteristics calculate. Here, since the discharge pressure P _PS of the main pump 2 at this time is P _{min as} described above, and in the calculation unit 50r, P _PS <P _pso , the virtual capacity of the cutoff control characteristic shown in FIG. Q _max is calculated as the limit value q * limit. In FIG. 3, the calculation point at this time is indicated by point A.

Since q * ≦ q * limit, the calculation unit 50s selects the virtual capacity q * of the load sensing control calculated by the calculation unit 50h, and outputs this as a new virtual capacity q **. The calculating unit 50j, and calculates a target flow rate Q _d is multiplied by the reference rotational speed N ₀ in the virtual capacity q **. Further, the calculating unit 50k, by dividing the target flow rate Q _d at maximum capacity q _max of the main pump 2, and calculates the target rotational speed N _d of the main pump 2, the calculating unit 50m, an inverter 60 the target speed N _d The command signal V _INV is converted to the command signal V _INV and the command signal V _INV is output to the inverter 60.

Here, as described above, when all the operation levers are neutral, the maximum load pressure is equal to the tank pressure, and the discharge pressure of the main pump 2 is larger than the target LS differential pressure _PGR . Therefore, since P _LS = P _PS −P _PLmax = P _PS > P _GR , the differential pressure deviation ΔP (= P _GR −P _LS ) calculated in the controller 50 becomes a negative value, and the main pump 2 The virtual capacity q * decreases. For this virtual volume q *, the minimum capacity q _min and maximum capacity q _max the calculation unit 50i is set, the virtual capacity q * decreases to a minimum capacity q _min, held at its minimum capacity q _min . For this reason, the target flow rate Q _d is decreased to a minimum value, and the target rotation speed N _d of the main pump 2 and the command signal V _{INV of the} inverter 60 are respectively decreased to a minimum value. As a result, the rotation speed of the electric motor 1 is held at the minimum value.

On the other hand, the discharge pressure of the main pump 2 at this time is P _{min as} described above, and since P _min <P ₀ , the torque control tilt piston 17a of the torque control device 17 does not operate, and the capacity of the main pump 2 is It is at the maximum q _max . In FIG. 4, the operating point at this time is indicated by point A.

As described above, the capacity of the main pump 2 is maintained at the maximum capacity q _max , but the virtual capacity q ** is reduced to the minimum capacity q _min by the limiting process of the arithmetic unit 50i by the load sensing control by the rotation speed control of the electric motor 1. Thus, since the rotation speed of the electric motor 1 is held at the minimum value, the flow rate discharged by the main pump 2 is also held at the minimum value.

Here, when the minimum rotation speed of the electric motor 1 is N _min ,
Q _d = q _min × N ₀ = q _max × N _min
N _min = N ₀ × (q _min / q _max )
It is.

That is, assuming that the actual capacity of the main pump 2 at this time is q and the rotation speed after the control of the electric motor 1 is N (hereinafter simply referred to as the rotation speed N), the actual capacity q, the virtual capacity q **, and the rotation speed N are q = q _max
q ** = q _min
N = N _min = N ₀ × (q _min / q _max )
become that way.

<Boom raising single operation (light load)>
When the boom raising operation is performed by operating the operation lever of the operation lever device 122 or 123 corresponding to the boom in the boom raising direction, the pilot pressure supplied from the pilot pressure supply path 31 is used as the original pressure. A pilot pressure is applied to an end pressure receiving portion of the flow control valve 6a from a remote control valve (not shown) for boom raising operation of the boom operating lever device, and the flow control valve 6a is switched to the left side in the drawing. Pressure oil in the pressure oil supply path 5 from the main pump 2 passes through the flow rate control valve 6a via the pressure compensation valve 7a and is supplied to the bottom side of the boom cylinder 3a.

At this time, the load pressure of the boom cylinder 3a is guided from the signal oil passage 27 to the pressure receiving portion 15c of the unload valve 15 via the load port 26a of the flow control valve 6a and the shuttle valves 9a, 9b, 9c. When the load pressure of the boom cylinder 3a is guided to the pressure receiving portion 15c of the unload valve 15, the cracking pressure of the unload valve 15 is set to the load pressure + the set pressure of the spring 15a, and the discharge pressure of the main pump 2 is the load pressure. The pressure rises to the pressure + the set pressure of the spring 15a + the pressure of the override characteristic. The pressure sensors 40 and 41 detect the discharge pressure and the maximum load pressure of the main pump 2 at this time.

The controller 50 calculates the virtual capacity q * of the main pump 2 based on the detection signals V _PS and V _PLmax of the pressure sensors 40 and 41 and the instruction signal V _EC of the reference rotation speed instruction dial 51 in the arithmetic units 50a to 50h. .

Here, the boom-up when starting, the discharge pressure of the main pump 2, by the action of the unloading valve 15 described above, is set slightly higher than the target LS differential pressure P _GR.

On the other hand, if the load pressure of the boom cylinder 3a is higher than the discharge pressure of the main pump 2 when the boom is raised, the load sensing differential pressure P _LS (= P _PS −P _PLmax ) is P _PS <P _PLmax . So it becomes a negative value. As a result, the differential pressure deviation ΔP calculated by the calculation unit 50f is ΔP = P _PS −P _LS > P _GR > 0, and the virtual capacity change amount Δq is calculated by the calculation unit 50g. As described above, the calculation unit 50g is configured such that the virtual capacity change amount Δq increases as ΔP increases. In addition, since ΔP> 0 when the boom is raised, Δq is also> 0. The computing unit 50h calculates the load sensing control virtual capacity q * by adding Δq to the virtual capacity q * one cycle before. Since Δq> 0, the virtual capacity q * increases.

Further, the discharge pressure P _PS of the main pump 2 is also led to the calculation unit 50r. When the discharge pressure of the main pump 2 is equal to or less than the set value P _pso , the calculation unit 50r holds the virtual capacity limit value q * limit for cut-off control at qmax. In FIG. 3, an example of the calculation point at this time is indicated by B point. Discharge pressure of the main pump 2 is P _b.

The arithmetic unit 50s, and outputs a smaller virtual volume q * and q _max as a new virtual volume q **. Virtual capacity q * is smaller than q _max outputs the virtual capacity q * as it is, the virtual capacity q * is greater than q _max, and outputs the q _max. Subsequently, in the calculation unit 50i, the new virtual capacity q ** is restricted so as not to be less than the minimum capacity q _min and not more than the maximum capacity qmax.

Therefore, when the boom is raised, the virtual capacity q ** increases from the minimum capacity q _min when the control lever is neutral to the maximum capacity q _max .

Controller 50, the virtual capacity q ** obtained in this manner, to calculate a target flow rate Q _d is multiplied by the reference rotational speed N ₀ in the calculating unit 50j. Further, the calculating unit 50k, by dividing the target flow rate Q _d at maximum capacity q _max of the main pump 2, and calculates the target rotational speed N _d of the main pump 2, the calculating unit 50m, an inverter 60 the target speed N _d The command signal V _INV is converted to the command signal V _INV and the command signal V _INV is output to the inverter 60.

Thus, since the virtual capacity q ** increases when the boom is activated, the target rotational speed N _d of the electric motor 1, that is, the command signal V _{INV of the} inverter 60 increases.

The rotation speed of the electric motor 1 continues to increase until the load sensing differential pressure P _LS becomes equal to the target LS differential pressure P _GR, and when P _LS = P _GR , ΔP = 0, so Δq = 0, and the virtual capacity q ** is kept at a certain value.

Thus the pressure in the second hydraulic fluid supply passage 4a, i.e. as discharge pressure of the main pump 2 is increased by the target LS differential pressure P _GR than the maximum load pressure, to increase or decrease the command signal V _INV of the inverter, the motor 1 is controlled so as to perform load sensing control using the electric motor 1.

On the other hand, since the discharge pressure P _b of the main pump 2 at this time is P _b <P ₀ at a light load, the torque control tilting piston 17a of the torque control device 17 does not operate, and the capacity of the main pump 2 is maximum. It is in. In FIG. 4, an example of the operating point at this time is indicated by point B.

Here, the maximum rotation speed of the electric motor 1 is the rotation speed when the virtual capacity q ** is at q _max , and the maximum rotation speed is N _max .
Q _d = q _max × N ₀ = q _max × N _max
N _max = N ₀
It is.

That is, the real capacity q, the virtual capacity q **, and the rotational speed N of the main pump 2 at this time are q = q _max
q _min <q ** ≦ q _max
N _min <N ≦ N _max
(N _min <N ≦ N ₀ )
become that way.

<Boom raising single operation (heavy load)>
Load pressure of the boom cylinder 3a is high, when it becomes the second predetermined pressure _{P 0} or the discharge pressure of the main pump 2 (the pressure of hydraulic fluid supply passage 4a) is determined by the spring 17b1,17b2 the torque control device 17, In the controller 50, the virtual capacity q * of the load sensing control is calculated in the calculation units 50a to 50c and 50f to 50h as in the case of the “boom raising single operation (light load)”. Further, when the discharge pressure of the main pump 2 is not less than P _{0 and not} more than the set value P _pso , the cut-off control limit value q * limit calculated by the calculation unit 50r is held at q _max . In FIG. 3, an example of the calculation point at this time is indicated by C point. The discharge pressure of the main pump 2 is _Pc . Then, the calculation units 50s and 50i perform the same processing as in the case of the “boom raising single operation (light load)”, and in the calculation units 50j to 50m, the command signal V _{INV of the} inverter 60 is obtained from the virtual capacity q **. Calculated and output to the inverter 60. Therefore, the virtual capacity q * of load sensing control increases or decreases according to the operation amount (required flow rate) of the operation lever and changes from the minimum to the maximum, as in the case of “Boom raising single operation (light load)”. Similarly, the rotational speed of the electric motor 1 (the rotational speed of the main pump 2) also changes from the minimum to the maximum according to the operation amount (required flow rate) of the operation lever.

On the other hand, at this time, since the discharge pressure of the main pump 2 is equal to or higher than the second predetermined pressure P ₀ , the torque control tilting piston 17a of the torque control device 17 is operated to reduce the capacity of the main pump 2. For this reason, so-called torque limit control is performed to reduce the capacity of the main pump 2 as the discharge pressure of the main pump 2 increases. In FIG. 4, an example of the operating point at this time is indicated by a point C1. The capacity (actual capacity) of the main pump 2 is qc.

Here, as described above, the characteristic lines of TP1 and TP2 in FIG. 4 are set by the springs 17b1 and 17b2, and the absorption torque of the main pump 2 (product of pump discharge pressure and capacity) —therefore, the drive torque of the electric motor 1 -Is controlled so as not to exceed the maximum torque (limit torque) TM in contact with the characteristic lines TP1 and TP2.

That is, the real capacity q, the virtual capacity q **, and the rotational speed N of the main pump 2 are q = qc.
q _min <q ** ≦ q _max
N _min <N ≦ N _max
(N _min <N ≦ N ₀ )
become that way.

Load pressure of the boom cylinder 3a is further increased, if the discharge pressure of the main pump 2 becomes a pressure set value P _pso more example P _e, the controller 50, the arithmetic unit 50r, from the cut-off control characteristics TP3, calculating a cut-off control of the limit value q * limit the value of for example the point E between the point M and point N in FIG. 3 q * limite (values between q _max and q * limit0). Subsequently, the computing unit 50s outputs the smaller of the virtual capacity q * and q * limit as a new virtual capacity q **. Subsequently, the calculation unit 50i limits the new virtual capacity q **, and the calculation units 50j to 50m calculate the command signal V _{INV of the} inverter 60 from the virtual capacity q **. Is output.

As described above, when the load pressure of the boom cylinder 3a is further increased and the discharge pressure of the main pump 2 becomes equal to or higher than the set value P _pso , the virtual capacity q ** is limited, so that the rotational speed of the electric motor 1 is low. It can be suppressed. At this time, the main pump 2A operates at point E1 in FIG. 4, and the pump capacity (actual capacity) is qe.

<Boom raising single operation (at the time of relief)>
For example, when the boom cylinder 3a extends and reaches the stroke end, the discharge pressure of the main pump 2 (pressure of the second pressure oil supply oil passage 4a) further increases and rises to the set pressure of the relief valve 14. When the relief valve 14 is actuated, the pressure in the second pressure oil supply oil passage 4a is maintained at a preset pressure (so-called relief pressure -P _max ) by the spring of the relief valve 14. Further, the load pressure of the boom cylinder 3a is led to the signal oil passage 27 via the load port 26a of the flow control valve 6a, and this pressure becomes equal to the relief pressure. That is, in this state, the pressure of the second pressure oil supply oil passage 4a is equal to the pressure of the signal oil passage 27, and is the same as the relief pressure set by the relief valve 14.

The controller 50 is supplied with a pressure detection signal V _PS for the pressure of the second pressure oil supply oil passage 4a by the pressure sensor 40 and a pressure detection signal V _{PLmax for} the pressure of the signal oil passage 27 by the pressure sensor 41. The pressures are equal and are the same as the relief pressure set by the relief valve 14.

At this time, the controller 50 increases or decreases the virtual capacity q * of the main pump 2 so that the pressure in the second pressure oil supply oil passage 4a is higher than the pressure in the signal oil passage 27 by the target LS differential pressure _PGR. In this case, since P _LS = P _PS −Plmax = 0 <P _GR , ΔP (= P _GR −P _LS ) becomes a positive value, and the virtual capacity q * of the main pump 2 increases.

However, since the discharge pressure of the main pump 2, that is, the pressure of the pressure oil supply oil passage 4a, becomes P _max at the time of relief when the relief valve 14 operates, the calculation unit 50r determines the cutoff control from the cutoff control characteristic TP3. As the virtual capacity limit value q * limit, the value at the N point in FIG. 3, that is, the minimum value q * limit0 is calculated. Subsequently, the computing unit 50s outputs the smaller of the virtual capacity q * and q * limit as a new virtual capacity q **. At this time, since the virtual capacity q *> q * limit0, the virtual capacity q ** is held at q * limit0. Subsequently, the calculation unit 50i limits the new virtual capacity q **, and the calculation units 50j to 50m calculate the command signal V _{INV of the} inverter 60 from the virtual capacity q **. Is output. Since the virtual volume q ** is q * limit0, target flow rate Q _d calculated in the calculation unit 50j is also Qsmall close to Q _min, the target rotational speed of the main pump 2 calculated in the calculation unit 50k N _d is also Nsmall close to the N _min. Thereby, the rotation speed of the electric motor 1 is suppressed to an extremely small value corresponding to Nsmall.

On the other hand, since the discharge pressure (P _max ) of the main pump 2 is equal to or higher than the second predetermined pressure P ₀ at this time as well, the torque control tilting piston 17a of the torque control device 17 is activated to reduce the capacity of the main pump 2. Torque limit control is performed. In FIG. 4, the operating point at this time is indicated by a point D. The capacity of the main pump 2 decreases to the minimum capacity qlimit-min for torque limit control.

That is, the real capacity q, virtual capacity q **, and rotation speed N of the main pump 2 at this time are q = qlimit-min
q ** = q * limit0
N = Nsmall
become that way.

The above is the operation when the boom operation is performed, but the same applies when the operation lever of the operation lever device corresponding to other work elements such as the arm 307 is operated.

~ Effect ~
<Effect 1>
In the present embodiment, not only the load sensing control but also when the discharge pressure of the main pump 2 rises above the set value P _pso near the set pressure P _max of the main relief valve 14 to the controller 50, Cut-off control for controlling the rotation speed of the main pump 2 is performed so as to reduce the discharge flow rate. Thereby, when the hydraulic cylinders such as the boom cylinder 3a and the arm cylinder 3b reach the stroke end, the flow rate discharged from the main pump 2 can be suppressed, so that the power consumed in vain from the main relief valve 14 is suppressed. be able to. As a result, since the power consumption of the electric motor 1 is reduced, the battery 70 that is the electric power source of the electric motor 1 can be extended, and the operating time of the electric hydraulic working machine (hydraulic excavator) can be extended. Further, since the heat generation during the operation of the main relief valve 14 is reduced, the hydraulic oil cooling system can be downsized.

Similarly, when the hydraulic cylinders such as the boom cylinder 3a and the arm cylinder 3b reach the stroke end, it is possible to suppress an increase in the rotational speed of the electric motor 1. The increase in vibration can be suppressed and the operator's comfort can be prevented from being impaired.

<Effect 2>
Further, in the present embodiment, in addition to performing load sensing control and cut-off control by the motor speed control of the controller 50, the main pump 2 is provided with a torque control device 17, and the discharge pressure of the main pump 2 is maintained at the main pressure. When the pressure of the relief valve 14 is within the pressure range below the set value P _pso near the set pressure P _max (within the range of P ₀ to P _pso ), the discharge flow rate of the main pump 2 decreases as the discharge pressure of the main pump 2 increases. Thus, the torque control for limiting the absorption torque of the main pump 2 is performed. As a result, when the discharge pressure of the main pump 2 rises, the horsepower consumed by the main pump 2 is suppressed by the torque control that limits the absorption torque of the main pump 2 even before the cutoff control by the motor rotation speed control starts. Since the power consumption of the electric motor 1 is reduced, the battery 70 that is the electric power source of the electric motor 1 can be further extended, and the operating time of the electric hydraulic working machine can be further extended. Moreover, since the power consumption of the electric motor 1 decreases, the electric motor 1 can be reduced in size.

This effect will be further described with reference to FIGS. 6A and 6B.

FIG. 6A is a diagram showing the horsepower characteristics of a conventional hydraulic drive device that performs load sensing control by controlling the rotation speed of a fixed displacement hydraulic pump that does not include a torque control device, and FIG. It is a figure which shows the horsepower characteristic of a hydraulic drive device. It is assumed that the capacity (constant) of the fixed displacement hydraulic pump in the conventional hydraulic drive device is the same q _max as the maximum capacity of the main pump 2 in the present embodiment shown in FIG.

In the conventional hydraulic drive device, since the hydraulic pump is a fixed displacement hydraulic pump, the displacement of the hydraulic pump remains constant at the maximum q _max when the discharge pressure of the hydraulic pump reaches the maximum P _max . For this reason, when the rotation speed of the electric motor is controlled to the maximum by load sensing control, the discharge flow rate of the hydraulic pump becomes the maximum Q _max , and the consumed horsepower of the hydraulic pump is expressed by the product of the maximum discharge pressure P _max and the maximum discharge flow rate Q _max. It increases to the value (the area of the shaded area in FIG. 6A). As a result, the output horsepower of the electric motor is increased to HM * corresponding to the consumed horsepower of the hydraulic pump. The power consumption of the electric motor increases. In addition, at this time, power consumption for cooling the motor also increases. Therefore, there is a problem in that the amount of discharge of a battery (power storage device) that is a power source of the electric motor increases, the battery is rapidly depleted, and the operation time of the work machine is shortened.

Also, it is necessary to determine the output of the electric motor in consideration of the maximum power consumption of the hydraulic pump, and there is a problem that a motor with a large output is required.

On the other hand, in the present embodiment, not only load sensing control is performed by controlling the number of revolutions of the motor, but the torque control device 17 is provided with the main pump 2 as a variable displacement type, and “boom raising single operation (heavy load)” and As described in the operation example of “Boom raising single operation (at the time of relief)”, the absorption torque of the main pump is controlled so as not to exceed the maximum torque TM when the discharge pressure of the main pump 2 rises. By performing the torque limit control of the main pump 2 in this way, when the discharge pressure of the main pump 2 increases, the absorption torque of the main pump 2 is controlled to be equal to or less than the maximum torque TM, and the consumed horsepower of the main pump 2 is maximum. Control is performed so as not to exceed the maximum horsepower HM obtained by multiplying the torque TM by the number of rotations of the main pump 2 at that time. As a result, the horsepower consumed by the main pump 2 is suppressed, the output horsepower of the motor 1 is reduced to HM, and the power consumption of the motor 1 is reduced as compared with the case where load sensing control is performed by conventional motor speed control. As a result, the battery 70 can last longer and the operating time of the electric hydraulic working machine can be extended. Moreover, the electric motor 1 can be reduced in size because the output horsepower of the electric motor 1 decreases.

<Effect 3>
Further, in this embodiment, obtains a target flow rate Q _d of the load sensing control by introducing the concept of virtual capacity q * of the hydraulic pump load sensing control arithmetic unit 50a ~ 50c of the controller 50, to 50f ~ 50h, the motor 1 Since the load sensing control is performed by controlling the rotational speed of the electric motor 1 by controlling the rotational speed of the motor 1, it is easy to incorporate other functions into the load sensing control.

For example, as described above, the virtual capacity limit value q * limit of the cutoff control is calculated by the calculation unit 50r, and the virtual capacity calculated by the load sensing control calculation units 50a to 50c and 50f to 50h is calculated by the calculation unit 50s. By selecting the smaller virtual capacity limit value to obtain a new virtual capacity and controlling the rotational speed of the electric motor 1, it is possible to easily realize cut-off control by controlling the rotational speed of the electric motor 1.

The controller 50 sets the reference rotation speed N ₀ on the basis of an instruction signal V _EC reference rotation speed instruction dial 51, and in accordance with the magnitude of the reference rotation speed N ₀ on the basis of the reference rotational speed N ₀ A target LS differential pressure _PGR and a target flow rate _Qd are calculated.

As a result, when the operator operates the reference rotation speed instruction dial 51 to reduce the reference rotation speed N ₀ , the target LS differential pressure P _GR and the target flow rate Q _d are reduced. Becomes small and good fine operability can be obtained.

Furthermore, as will be described later as the second embodiment, it is possible to incorporate a control algorithm that operates in the same manner as the torque control device 17 into the controller 50.

<Effect 4>
In the present embodiment, since the main pump 2 is a variable displacement type and the torque control device 17 is provided in the main pump 2, the rotation speed of the motor is controlled using a normal hydraulic pump having a torque control function. Thus, load sensing control, cutoff control, and torque control can be easily realized.

FIG. 7 is a diagram showing a configuration of a hydraulic drive device for an electric hydraulic work machine according to the second embodiment of the present invention. This embodiment is also a case where the present invention is applied to a hydraulic drive device of a front swing type hydraulic excavator.

~ Configuration ~
In FIG. 7, the hydraulic drive apparatus according to the present embodiment is different from the first embodiment shown in FIG. 1 in that the main pump 2A is a fixed displacement type, and the main pump 2A is a torque control device 17 for controlling horsepower. Not equipped. On the other hand, the controller 50A has a control function (function of a torque control device) for simulating horsepower control of the main pump 2A in addition to a control function for simulating cut-off control of the main pump 2A.

FIG. 8 is a functional block diagram showing the processing contents of the controller 50A.

The controller 50A includes a calculation unit 50Ar instead of the calculation unit 50r in the functional block diagram shown in FIG.

The calculation unit 50Ar has a table in which characteristics are set in which characteristics (torque control characteristics) that simulate torque control and characteristics (cutoff control characteristics) that simulate cutoff control are combined. The discharge pressure P _PS of the main pump 2A converted by the calculation unit 50a is input to the calculation unit 50Ar, and the calculation unit 50Ar refers to the discharge pressure P _PS of the main pump 2A in the table and the corresponding virtual capacity limit value ( Maximum virtual capacity) q * limit is calculated.

FIG. 9 is a diagram showing characteristics obtained by combining characteristics (torque control characteristics) simulating torque control set in the arithmetic unit 50Ar and characteristics (cut-off control characteristics) simulating cut-off control. FIG. 10 is a diagram showing the torque characteristics of the main pump 2A.

As shown in FIG. 10, since the main pump 2A is a fixed capacity type, the capacity of the main pump 2A is constant over the entire range of the discharge pressure of the main pump 2A and is at the maximum capacity q _max on the characteristic line TP0. Further, when the discharge pressure of the main pump 2A increases, the consumption torque of the main pump 2A increases linearly over the entire range of the discharge pressure.

Torque control characteristics set to the arithmetic unit 50Ar is a characteristic TP0r2 the discharge pressure of the main pump 2A corresponds to the characteristic line TP0 maximum capacity of the main pump 2A when less than P _0, the discharge pressure of the main pump 2A P This is composed of a constant torque curve TP4 when it becomes ₀ or more and a cutoff control characteristic TP5 when the discharge pressure of the main pump 2A exceeds the set value P _pso . The cutoff control characteristic TP5 indicates that the limit value q * limit is steep and linear from q * limit1 to the minimum value q * limit2 when the discharge pressure of the main pump 2A increases from the set value P _pso to the maximum discharge pressure P _max. It is set to be smaller. As described above, the set value P _pso is higher than the starting pressure P ₀ (described later) of the constant absorption torque control, and is close to the maximum discharge pressure P _max . The limit value q * limit1 is a value on the constant torque curve TP4 when the discharge pressure of the main pump 2A is at the set value P _pso . The minimum value q * limit2 is a small volume close to the minimum capacity q _min of the main pump 2A, for example, a minimum capacity q _min.

As a result of the combination of the torque control characteristic and the cutoff control characteristic set in the arithmetic unit 50Ar as described above, the arithmetic unit 50Ar has a low discharge pressure P _PS of the main pump 2A, and a characteristic line when P _PS <P _0. q * limit = q _max based on TP0r2 is calculated, the discharge pressure P _PS of the main pump 2A rises and becomes _{P PS ≧ P 0, q *} limit = qlimit is calculated based on the torque constant curve TP4 . Further, when the discharge pressure P _PS of the main pump 2A further increases and P _PS ≧ P _pso , q * limit = qlimit is calculated based on the cutoff control characteristic TP5, the boom cylinder 3a reaches the stroke end, and the main When the discharge pressure of the pump 2A reaches the maximum P _max, the minimum capacity q * limit2 (= q _min) is calculated.

The calculation unit 50s selects a smaller one of the virtual capacity q * of the load sensing control calculated by the calculation unit 50h and the limit value q * limit of the virtual capacity obtained by the calculation unit 50r as a new virtual capacity q **. Output.

Other processing (processing of the calculation units 50a to 50h and calculation units 50i to 50m) is the same as that shown in FIG.

The above-described function of the controller 50A, the inverter 60, and the pressure sensors 40 and 41 are similar to the first embodiment in that the discharge pressure of the main pump 2A is higher than the maximum load pressure of the actuators 3a, 3b, 3c. Load sensing control for controlling the rotational speed of the main pump 2A so as to increase only when the discharge pressure of the main pump 2A rises above the first predetermined pressure P _pso near the set pressure P _max of the main relief valve 14 An electric motor rotation speed control device 200A that performs cut-off control for controlling the rotation speed of the main pump 2A so as to reduce the discharge flow rate of the pump 2A is configured.

The calculation units 50a to 50c and 50f to 50h of the controller 50A are based on the discharge pressure P _PS and the maximum load pressure P _{PLmax of} the main pump 2A detected by the pressure sensors 40 and 41, and the target LS differential pressure P _GR . Load sensing control for calculating the virtual capacity q * of the main pump 2A that increases or decreases according to the positive or negative of the differential pressure deviation ΔP between the differential pressure P _LS between the discharge pressure of the main pump 2A and the maximum load pressure and the target LS differential pressure P _GR The calculation unit 201 is configured.

Based on the discharge pressure of the main pump 2A detected by the pressure sensor 40, the calculation units 50Ar and 50s of the controller 50A are configured to have a first predetermined pressure P _{pso that} the discharge pressure of the main pump 2A is close to the set pressure P _max of the main relief valve 14. Calculate the virtual capacity limit value q * limit of the cutoff control that suddenly decreases when it rises above, and select the smaller one of the virtual capacity q * and virtual capacity limit value q * limit calculated by the load sensing control calculation unit A capacity limit control calculation unit 202A for obtaining the virtual capacity q ** is configured.

In addition, the calculation units 50Ar and 50s of the controller 50A are incorporated in the controller 50A as a function of the controller 50A, and when the discharge pressure of the main pump 2A increases, the discharge flow rate of the main pump 2A is decreased to reduce the main pump 2A. A torque control device is configured to control the absorption torque so as not to exceed a preset maximum torque.

Further, the arithmetic unit 50aR, 50s, based on the discharge pressure of the main pump 2A, the pressure sensor 40 detects the discharge pressure of the main pump 2A is at a second predetermined pressure _{P 0} or more, the set pressure P of the main relief valve 14 A virtual capacity limit value q * for torque limit control that decreases as the discharge pressure of the main pump 2A increases when the pressure is in a pressure range (in the range of P ₀ to P _pso ) that is less than the first predetermined pressure P _pso near _max . When the limi is calculated and the discharge pressure of the main pump 2A rises above the first predetermined pressure P _pso near the set pressure P _max of the main relief valve 14, the virtual of the cutoff control that suddenly decreases from the limit value of the virtual capacity of the torque limit control Capacity for calculating a new virtual capacity q ** by calculating the capacity limit value q * limi and selecting the smaller one of the virtual capacity q * and the virtual capacity limit value q * limi calculated by the load sensing control calculation unit Constituting the limit control calculation unit 202A.

Based on the discharge pressure of the main pump 2A detected by the pressure sensor 40, the calculation units 50Ar, 50s calculate a virtual capacity limit value q * limit that decreases as the discharge pressure of the main pump 2A increases, and the load Torque limit control for selecting a smaller virtual capacity q * and virtual capacity limit value q * limit calculated by the sensing control calculation units (calculation units 50a to 50c, 50f to 50h) to obtain a new virtual capacity q ** It can also be said that it is a calculation part.

~ Operation ~
Next, the operation of the present embodiment will be described.

<When the control lever is neutral>
When all the operation devices including the operation levers of the operation lever devices 122, 123, and 124 are neutral, as described in the operation example of “operation lever neutral” in the first embodiment, the main pump 2A The discharge pressure is P _min corresponding to the set pressure of the spring 15 a of the unload valve 15. In this case, as described above, the differential pressure deviation ΔP (= P _GR −P _LS ) calculated by the calculation unit 50f of the controller 50A is a negative value, and the virtual capacity q * of the load sensing control decreases.

On the other hand, since the discharge pressure P _PS of the main pump 2A obtained by the calculation unit 50a of the controller 50A is P _min and P _PS <P ₀ in the calculation unit 50Ar, the virtual capacity is limited from the characteristics that simulate torque control. Q _max is calculated as the value q * limit. In FIG. 9, the calculation point at this time is indicated by point A1.

Here, since q * ≦ q * limit, the calculation unit 50s selects the virtual capacity q * of the load sensing control calculated by the calculation unit 50h, and outputs this as a new virtual capacity q **.

The subsequent processing is the same as in the case of “when the control lever is neutral” in the first embodiment.

Here, the virtual capacity q ** is reduced to the minimum capacity q _min by the limiting process of the calculation unit 50i, and the target flow rate Q _d , the target rotation speed N _d of the main pump 2A, and the command signal V _INV of the inverter 60 are minimum. Value. Thereby, the rotation speed of the electric motor 1 is held at the minimum value, and the discharge flow rate of the main pump 2A is also held at the minimum value.

On the other hand, the main pump 2A operates at point A1 in FIG. 10, and the pump capacity (actual capacity) is q _max (fixed).

That is, the real capacity q, virtual capacity q *, and rotation speed N of the main pump 2A are q = q _max (fixed)
q ** = q _min
N = N _min = N ₀ × (q _min / q _max )
become that way.

<Boom raising single operation (light load)>
When the boom raising operation is performed by operating the operation lever of the operation lever device 122, 123 corresponding to the boom in the boom raising direction, the load sensing control virtual capacity q * calculated by the controller 50A is operated. Increase or decrease according to the lever operation amount (required flow rate). At this time, when the discharge pressure of the main pump 2A is equal to or less than the set value P ₀ , the calculation unit 50Ar sets q _max as a virtual capacity limit value q * limit from a characteristic that simulates torque control (characteristic line TP0r2 in FIG. 9). calculate. In FIG. 9, the calculation point at this time is indicated by point B1. Discharge pressure of the main pump 2A is a _{P b.}

Also in this case, since q * ≦ q * limit, the calculation unit 50s selects the virtual capacity q * of the load sensing control calculated by the calculation unit 50h, and outputs this as a new virtual capacity q **. .

The subsequent processing is the same as that in the case of the “boom raising single operation (light load)” in the first embodiment.

Here, the virtual capacity q ** increases or decreases in accordance with the operation amount (required flow rate) of the operation lever, and changes from the minimum to the maximum by the restriction process of the calculation unit 50i. As a result, the rotational speed of the electric motor 1 (the rotational speed of the main pump 2A) similarly changes from the minimum to the maximum according to the operation amount (required flow rate) of the operation lever.

On the other hand, the main pump 2A operates at point B1 in FIG. 10, and the pump capacity (actual capacity) is q _max (fixed).

That is, the real capacity q, the virtual capacity q *, and the rotation speed N of the main pump 2A at this time are q = q _max (fixed)
q _min <q ** ≦ q _max
N _min <N ≦ N _max
(N _min <N ≦ N ₀ )
become that way.

<Boom raising single operation (heavy load)>
Even during a heavy load in which the load pressure of the boom cylinder 3a increases, the virtual capacity q * of the load sensing control calculated by the controller 50A increases or decreases according to the operation amount (required flow rate) of the operation lever. At this time, when the discharge pressure of the main pump 2A is not less than P _{0 and not} more than the set value P _pso at the time of heavy load, the calculation unit 50Ar makes a hypothesis from the characteristic of torque control (torque constant curve TP4 in FIG. 9). calculating the qlimit (<q _max) as the limit value q * limit of capacity. In FIG. 9, the calculation point at this time is indicated by point C2. The discharge pressure of the main pump 2A is _Pc . At the point C2, q * limit = q * limitc.

In the calculation unit 50s, the smaller one of the virtual capacity q * and the virtual capacity limit value q * limit is selected and output as a new virtual capacity q **. That is, when q * ≦ q * limit, q * is selected, and when q *> q * limit, q * limit is selected, and these are output as new virtual capacity q **.

The subsequent processing is the same as in the case of the “boom raising single operation (heavy load)” in the first embodiment.

Here, since the virtual capacity q ** is limited to q * limit, the target flow rate Q _d , the target rotational speed N _d of the main pump 2A, and the command signal V _INV of the inverter 60 are similarly limited, and the electric motor 1 The rotation speed is limited.

Thus, the controller 50 has a control function having the same function as the torque control device 17 in the first embodiment, and is controlled so that the absorption torque of the main pump 2A does not exceed the maximum torque (limit torque) TM. The

On the other hand, the main pump 2A operates at a point C3 in FIG. 10, and the pump capacity (actual capacity) is q _max (fixed).

Assuming that the rotation speed corresponding to the virtual capacity limit value q * limit1 at point P is Nlimit1, the real capacity q, virtual capacity q **, and rotation speed N of the main pump 2A are q = q _max (fixed).
q * limit1 <q *** ≦ q _max
Nlimit1 <N ≦ N _max
become that way.

Load pressure of the boom cylinder 3a is further increased, if the discharge pressure of the main pump 2A becomes the pressure set value P _pso more example P _f, the controller 50, the computing section 50aR, from the cut-off control characteristic TP5, The value q * limitf at the point F between the points P and Q in FIG. 9 is calculated as the limit value q * limit for the cutoff control. Subsequently, the computing unit 50s outputs the smaller of the virtual capacity q * and q * limit as a new virtual capacity q **. Subsequently, the calculation unit 50i limits the new virtual capacity q **, and the calculation units 50j to 50m calculate the command signal V _{INV of the} inverter 60 from the virtual capacity q **. Is output.

In this way, when the load pressure of the boom cylinder 3a further increases and the discharge pressure of the main pump 2A becomes equal to or higher than the set value P _pso , the virtual capacity q ** is limited, so the rotational speed of the electric motor 1 is low. It can be suppressed. At this time, the main pump 2A operates at point F1 in FIG. 10, and the pump capacity (actual capacity) is q _max (fixed).

<Boom raising single operation (at the time of relief)>
For example, when the boom cylinder 3a extends to reach the stroke end, as described above, the discharge pressure of the main pump 2A is maintained at the relief pressure _Pmax , and the maximum load pressure is the same as the relief pressure. In FIG. 10, at this time, the main pump 2A is operating at the point D1. In this case, as described above, the differential pressure deviation ΔP (= P _GR −P _LS ) calculated by the calculation unit 50f of the controller 50A becomes a positive value, and the virtual capacity q * of the load sensing control increases.

On the other hand, since the discharge pressure P _PS of the main pump 2A obtained by the calculation unit 50a of the controller 50A is P _max , the calculation unit 50Ar uses the cutoff control characteristic TP5 as the cutoff control limit value q * limit as shown in FIG. Q point value, that is, the minimum capacity q * limit2 (= q _min ) is calculated. Subsequently, since q *> q * limit, the calculation unit 50s selects the virtual capacity limit value q * limit calculated by the calculation unit 50r, and outputs this as a new virtual capacity q **.

The subsequent processing is the same as in the case of “Boom raising single operation (at the time of relief)”.

Here, since the virtual capacity q ** is limited to qlimit2 (= q _min ), the target flow rate Q _d , the target rotational speed N _d of the main pump 2A, and the command signal V _INV of the inverter 60 are similarly minimum values. The number of rotations of the electric motor 1 is limited to the minimum N _min .

That is, the real capacity q, virtual capacity q **, and rotation speed N of the main pump 2A at this time are q = q _max (fixed)
q ** = qlimit2 (= q _min )
N = N _min
become that way.

The above is the operation when the boom operation is performed, but the same applies when the operation lever of the operation lever device corresponding to other work elements such as the arm 307 is operated.

~ Effect ~
<Effect 1>
Also in this embodiment, when the hydraulic cylinders such as the boom cylinder 3a and the arm cylinder 3b reach the stroke end, the flow rate discharged from the main pump 2A can be suppressed, so that the main relief valve 14 consumes wastefully. Can be suppressed. As a result, since the power consumption of the electric motor 1 is reduced, the battery 70 that is the electric power source of the electric motor 1 can be extended, and the operating time of the electric hydraulic working machine (hydraulic excavator) can be extended. Further, since the heat generation during the operation of the main relief valve 14 is reduced, the hydraulic oil cooling system can be downsized.

Similarly, when the hydraulic cylinders such as the boom cylinder 3a and the arm cylinder 3b reach the stroke end, it is possible to suppress an increase in the rotational speed of the electric motor 1. The increase in vibration can be suppressed and the operator's comfort can be prevented from being impaired.

In addition, when the discharge pressure of the main pump 2A increases, the consumed horsepower of the main pump 2A is suppressed by the torque control based on the motor rotational speed control even before the cutoff control based on the motor rotational speed control is started. Since power consumption is reduced, the battery 70 that is the power source of the electric motor 1 can be further extended, and the operating time of the electric hydraulic work machine can be further extended. Moreover, since the power consumption of the electric motor 1 decreases, the electric motor 1 can be reduced in size.

<Effect 2>
In addition, according to the present embodiment, since the main pump 2A is a fixed capacity type, the size of the main pump 2A can be kept small, and space saving can be realized.

<Others>
Various modifications can be made to the above embodiment within the spirit of the present invention. For example, in the above-described embodiment, the pressure compensating valves 7a, 7b, 7c,... Are arranged on the downstream side of the meter-in restricting portions of the flow control valves 6a, 6b, 6c, and all the flow control valves 6a, 6b, 6c,. The downstream pressure of the flow control valves 6a, 6b, 6c... Is controlled to the same differential pressure by controlling the downstream pressure to the same maximum load pressure, but the flow control valves 6a, 6b, 6c. It may be a front-end type that is arranged upstream of the meter-in throttle and controls the differential pressure across the meter-in throttle to a set value.

Moreover, although the case where the work machine is a hydraulic excavator has been described in the above embodiment, a construction machine other than a hydraulic excavator (for example, a hydraulic crane) may be used as long as it is a work machine that drives a plurality of actuators based on oil discharged from the main pump. A similar effect can be obtained by applying the present invention to a wheel excavator or the like.

1 Electric motor 2, 2A Hydraulic pump (main pump)
2a First pressure oil supply oil passages 3a, 3b, 3c, ... Actuator 4 Control valve 4a Second pressure oil supply oil passages 6a, 6b, 6c, ... Flow rate control valves 7a, 7b, 7c, ... Pressure compensation valves 8a, 8b , 8c, ... Oil passages 9a, 9b, 9c, ... Shuttle valve 14 Main relief valve 15 Unload valve 15a Spring 15b Pressure receiving part 15c for opening direction operation Pressure receiving part 17 for closing direction operation Torque control device 17a Torque control tilt piston 17b1 , 17b2 Springs 21a, 21b, 21c,... Pressure-receiving portions 22a, 22b, 22c, operating in the closing direction ... Pressure-receiving portions 24 operating in the opening direction Gate lock levers 25a, 25b, 25c, ... Oil paths 26a, 26b, 26c, ... Port 27, 27a, 27b, 27c, ... Signal oil passage 30 Pilot pump 31, 31a Pilot oil passage 32 Pilot relay Valve 38 Pilot hydraulic power source 40, 41 Pressure sensor 50, 50A Controllers 50a to 50m Calculation units 50r, 50Ar, 50s Calculation unit 51 Reference rotation speed instruction dial 51
60 Inverter 61 Chopper 70 Battery 100 Gate lock valve 122, 123 Operation lever device 200, 200A Motor rotation speed control device 201 Load sensing control calculation unit 202, 202A Capacity limit control calculation unit q * Virtual capacity q * limit Limit value of virtual capacity q ** New virtual capacity TP1, TP2 Torque control characteristic line TP3 Cut-off control characteristic TP4 Constant torque curve TP5 Cut-off control characteristic

Claims (7)

1. An electric motor,
   A hydraulic pump driven by this electric motor;
   A plurality of actuators driven by pressure oil discharged from the hydraulic pump;
   A plurality of flow rate control valves for controlling the flow rate of pressure oil supplied from the hydraulic pump to a plurality of actuators;
   It is connected to a pressure oil supply oil passage that supplies the discharge oil of the hydraulic pump to the plurality of flow control valves, and is opened when the discharge pressure of the hydraulic pump exceeds a set pressure. A relief valve that returns oil to the tank;
   In a hydraulic drive device of an electric hydraulic working machine comprising a power storage device for supplying electric power to the electric motor,
   Load sensing control for controlling the rotational speed of the hydraulic pump so that the discharge pressure of the hydraulic pump is higher than the maximum load pressure of the plurality of actuators by a target differential pressure, and the discharge pressure of the hydraulic pump is a set pressure of the relief valve An electric motor rotation speed control device for performing a cutoff control for controlling the rotation speed of the hydraulic pump so as to decrease the discharge flow rate of the hydraulic pump when the pressure rises to a nearby first predetermined pressure or more. Hydraulic drive device for electric hydraulic work machine.
2. The hydraulic drive device for an electric hydraulic work machine according to claim 1,
   The motor rotation speed control device is:
   A first pressure sensor for detecting a discharge pressure of the hydraulic pump;
   A second pressure sensor for detecting the maximum load pressure;
   An inverter for controlling the rotational speed of the electric motor;
   With a controller,
   The controller is
   Based on the discharge pressure of the hydraulic pump, the maximum load pressure, and the target LS differential pressure detected by the first and second pressure sensors, the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure and the target A load sensing control calculation unit for calculating a virtual capacity of the hydraulic pump that increases or decreases according to the positive or negative of the differential pressure deviation from the LS differential pressure;
   Based on the discharge pressure of the hydraulic pump detected by the first pressure sensor, the limit value of the virtual capacity of the cutoff control that suddenly decreases when the discharge pressure of the hydraulic pump rises above the first predetermined pressure is calculated, A capacity limit control calculation unit that calculates a new virtual capacity by selecting a smaller one of the virtual capacity calculated by the load sensing control calculation unit and the limit value of the virtual capacity;
   The controller calculates the target flow rate of the hydraulic pump by multiplying the new virtual capacity by the reference rotational speed, and controls the rotational speed of the electric motor so that the discharge flow rate of the hydraulic pump becomes the target flow rate. A hydraulic drive device for an electric hydraulic working machine, wherein a control command is output to the inverter.
3. The hydraulic drive device for an electric hydraulic work machine according to claim 1,
   When the discharge pressure of the hydraulic pump is in a pressure range that is greater than or equal to a second predetermined pressure and less than or equal to the first predetermined pressure, the discharge flow rate of the hydraulic pump is decreased as the discharge pressure of the hydraulic pump increases, thereby reducing the hydraulic pressure. A hydraulic drive device for an electric hydraulic working machine, further comprising a torque control device for controlling the absorption torque of the pump so as not to exceed a preset maximum torque.
4. The hydraulic drive device for an electric hydraulic work machine according to claim 2,
   The hydraulic pump is a variable displacement hydraulic pump,
   A regulator provided in the hydraulic pump for controlling the absorption torque of the hydraulic pump so as not to exceed a preset maximum torque by decreasing a discharge flow rate of the hydraulic pump when a discharge pressure of the hydraulic pump increases; A hydraulic drive device for an electric hydraulic work machine, further comprising:
5. The hydraulic drive device for an electric hydraulic work machine according to claim 2,
   The hydraulic pump is a fixed displacement hydraulic pump,
   It is incorporated as a function of the controller, and controls so that the absorption torque of the hydraulic pump does not exceed a preset maximum torque by reducing the discharge flow rate of the hydraulic pump when the discharge pressure of the hydraulic pump increases. A hydraulic drive device for an electric hydraulic work machine, further comprising a torque control device.
6. The hydraulic drive device for an electric hydraulic work machine according to claim 2,
   The hydraulic pump is a fixed displacement hydraulic pump,
   The capacity restriction control calculation unit is
   Based on the discharge pressure of the hydraulic pump detected by the first pressure sensor, when the discharge pressure of the hydraulic pump is in a pressure range not less than a second predetermined pressure and not more than the first predetermined pressure, the discharge of the hydraulic pump The limit value of the virtual capacity of torque limit control that decreases as the pressure increases is calculated, and when the discharge pressure of the hydraulic pump rises above the first predetermined pressure, the virtual capacity limit value of the torque limit control rapidly decreases. A virtual capacity limit value for cut-off control is calculated, and a new virtual capacity is obtained by selecting a smaller one of the virtual capacity calculated by the load sensing control calculation unit and the limit value of the virtual capacity. Hydraulic drive device for electric hydraulic work machine.
7. The hydraulic drive device for an electric hydraulic work machine according to claim 2,
   An operation device for instructing the reference rotational speed;
   The controller sets the reference rotational speed based on an instruction signal from the operating device, and calculates the target LS differential pressure and the target flow rate according to the reference rotational speed based on the reference rotational speed. A hydraulic drive device for an electric hydraulic work machine.

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