JP7227176B2 - construction machinery - Google Patents

Description

The present invention relates to a construction machine such as a hydraulic excavator equipped with a hydraulic drive system for driving a hydraulic actuator.

In recent years, energy saving has become an important development item for construction machinery such as hydraulic excavators and wheel loaders. In order to save energy in construction machinery, it is important to save energy in the hydraulic system itself. Application of a hydraulic closed circuit system, in which a hydraulic actuator is connected in a closed circuit with a hydraulic pump and directly controlled, is being studied. This system has no pressure loss due to the control valve, and the pump discharges only the required flow rate, so the flow rate loss is small. It is also possible to regenerate the potential energy of the actuator and the energy during deceleration. Therefore, energy saving is possible.

There is Patent Document 1 as a background art of a construction machine combined with a hydraulic closed circuit. In Patent Document 1, by branching and connecting a plurality of variable displacement hydraulic pumps to a plurality of hydraulic actuators via electromagnetic switching valves (hereinafter referred to as switching valves) to form a closed hydraulic circuit, the combined operation and high speed operation of the actuators are achieved. An operable configuration is described.

JP 2015-048899 A

In the closed hydraulic circuit disclosed in Patent Document 1, a variable-displacement double-tilt pump that can switch the discharge direction of hydraulic oil is used. A switching valve is controlled to open and close by a controller so that any one of the actuators is connected to one double-tilting pump by a flow path and driven according to the lever operation by the driver. When the lever is not operated, the actuator is stopped and held by closing the switching valve. At this time, the double tilting pump is controlled so that the discharge flow rate becomes zero.

In order to control the discharge flow rate, the double tilting pump has a regulator as a mechanism for controlling the displacement volume, which is the discharge flow rate per rotation. The regulator consists of a servo piston connected to the swash plate of the double tilting pump and an electromagnetic valve that generates operating pressure for the servo piston. The solenoid valve generates the operating pressure for the servo piston according to the control signal from the controller, and the servo piston adjusts the angle (tilt angle) of the swash plate of the double tilt pump, thereby increasing the displacement volume of the double tilt pump. changes. However, even if the controller outputs a control signal to the solenoid valve to set the tilting angle of both tilting pumps to zero, the tilting angle does not become zero due to the friction of the servo piston and the swash plate, resulting in a very small discharge flow rate. Occur. At this time, since the switching valve is closed and there is no place for the hydraulic oil discharged from the double tilting pump to go, there is a problem that the discharge pressure of the double tilting pump increases and noise and fuel consumption deteriorate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to improve the control accuracy of the tilting angle of a double tilting pump, and to increase the discharge flow rate of the double tilting pump when the operating lever is in the neutral position. An object of the present invention is to provide a construction machine capable of suppressing noise and a decrease in fuel consumption caused by an increase in the discharge pressure of a dual tilting pump by bringing it closer to zero.

In order to achieve the above object, the present invention provides a double tilting pump capable of adjusting the discharge direction and discharge flow rate of hydraulic oil in accordance with a tilting angle, which is the angle of a swash plate, and a double tilting pump capable of adjusting the tilting angle. a regulator, a hydraulic actuator, a first flow path connecting one input/output port of the double tilting pump and one oil chamber of the hydraulic actuator, the other input/output port of the double tilting pump, and the a second flow path connecting the other oil chamber of the hydraulic actuator; a switching valve capable of switching between communication and blockage of the first flow path and the second flow path; and for instructing the operation of the hydraulic actuator. and a controller for controlling the switching valve and the regulator according to the operation of the operation lever, the regulator controlling the servo piston connected to the swash plate and the control signal from the controller. and a solenoid valve for generating an operating pressure for the servo piston, the construction machine includes a first pressure sensor for detecting the operating pressure for the servo piston, and the controller controls the tilt based on the operation amount of the operating lever. A tilt angle target value, which is a tilt angle target value, is calculated, and an estimated value of the tilt angle is calculated based on the operating pressure of the servo piston detected by the first pressure sensor and the frictional force acting on the servo piston. is calculated, and the control signal to the electromagnetic valve is controlled so that the difference between the estimated tilt angle and the target tilt angle is reduced.

According to the present invention configured as described above, the tilt angle estimated value is calculated based on the operating pressure of the servo piston and the frictional force acting on the servo piston, and the tilt angle is calculated based on the operation amount of the operating lever. The operating pressure of the servo piston is adjusted so that the difference between the tilt angle target value and the tilt angle estimated value becomes small. This reduces the difference (residual error) between the stop position of the servo piston and the target position regardless of the friction of the servo piston and the swash plate of the double tilting pump. As a result, when the control lever is in the neutral position, the discharge flow rate of the double-tilt pump can be brought closer to zero, which suppresses the pressure rise in the closed circuit, thereby suppressing noise and reducing fuel consumption. Become.

According to the construction machine of the present invention, the control accuracy of the tilting angle of the double tilting pump is improved, and the discharge flow rate of the double tilting pump is brought close to zero when the operation lever is in the neutral position. It is possible to suppress the noise and decrease in fuel consumption caused by the increase in the discharge pressure of the pump.

1 is a side view showing a hydraulic excavator according to a first embodiment of the present invention; FIG. 1 is a schematic diagram of a hydraulic drive in a first embodiment of the invention; FIG. 3 is a functional block diagram of a controller in the first embodiment of the invention; FIG. 1 is a configuration diagram of a regulator in a first embodiment of the invention; FIG. 9 is a flow chart showing processing of a controller in the second embodiment of the present invention; FIG. 4 is a schematic diagram of a hydraulic drive in a second embodiment of the invention; FIG. 5 is a functional block diagram of a controller in a second embodiment of the invention; 9 is a flow chart showing processing of a controller in the second embodiment of the present invention; FIG. 11 is a functional block diagram of a controller in a third embodiment of the invention; FIG. 11 is a flow chart showing processing of a controller in the third embodiment of the present invention; FIG. FIG. 10 is a diagram showing the operation of the hydraulic drive system in the third embodiment of the invention in comparison with the first embodiment;

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

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

(hydraulic excavator)
In FIG. 1, a hydraulic excavator 100 includes a lower traveling body 102 equipped with a crawler-type traveling device driven by a traveling motor 101, and an upper traveling body 102 mounted rotatably on the lower traveling body 102 and driven by a slewing motor 103. It has a revolving body 104 and a working device 105 attached to the front part of the upper revolving body 104 so as to be vertically rotatable. A cab 106 on which an operator rides is provided on the upper revolving body 104 .

The work device 105 includes a boom 107 attached to the front portion of the upper revolving body 104 so as to be rotatable in the vertical direction, and an arm as a work member connected to the tip portion of the boom 107 so as to be rotatable in the vertical or longitudinal direction. 108, a bucket 109 as a working member connected to the tip of the arm 108 so as to be rotatable in the vertical or longitudinal direction, a boom cylinder 4 as a hydraulic actuator for driving the boom 107, and a hydraulic actuator for driving the arm 108. and a bucket cylinder 111 that is a hydraulic actuator that drives the bucket 109 .

(hydraulic drive)
FIG. 2 is a schematic diagram showing an example of a hydraulic drive system mounted on the hydraulic excavator 100. As shown in FIG. In FIG. 2, the hydraulic drive system 200 drives the boom cylinder 4, which is a hydraulic actuator, in a closed circuit. 2, portions related to the driving of the hydraulic actuators other than the boom cylinder 4 are omitted.

(bi-tilting pump)
The double tilting pump 2 is driven by receiving power from the engine 1 . Both tilting pumps 2 have a tilting swash plate mechanism having a pair of input/output ports 2a and 2b, and a regulator that adjusts the angle (tilt angle) of the swash plate 2c to adjust the discharge flow rate (displacement volume) per rotation. 3. The regulator 3 controls the discharge direction and the discharge flow rate of the double tilting pump 2 according to the control signal received from the controller 6 via the control signal line.

(Switching valve)
Two input/output ports of the tilting pump 2 are connected to the switching valve 5 via flow paths 14 and 15 . The switching valve 5 is connected to the boom cylinder 4 via passages 16 and 17 . The switching valve 5 is controlled to open/close by a control signal received from the controller 6, and switches the flow paths 14, 16 and the flow paths 16, 17 to a flowing state or a blocked state. When the switching valve 5 is open, one input/output port 2a of the tilting pump 2 communicates with the bottom side oil chamber 4a of the boom cylinder 4 through the flow paths 14 and 16, and the other input/output port 2b communicates with the bottom side oil chamber 4a of the boom cylinder 4. communicates with the rod-side oil chamber 4 b of the boom cylinder 4 via flow paths 15 and 17 . As a result, the tilting pump 2 and the boom cylinder 4 are connected in a closed circuit.

(controller)
The controller 6 is composed of an input/output interface for inputting and outputting signals between each device, a central processing unit (CPU) and its peripheral circuits, etc., and has an arithmetic unit that performs various calculations according to a predetermined program. It is connected by a signal line to an operation lever 7 that gives an instruction to drive the boom cylinder 4, and is connected to the regulator 3 and the switching valve 5 by a control signal line. The controller 6 performs each function of a manipulated variable calculation unit 6a, a tilt angle estimation unit 6b, a tilt angle control unit 6c, a pump control unit 6d, and a switching valve control unit 6e by executing a predetermined program by an arithmetic unit. Realize

FIG. 3 shows a functional block diagram of the controller 6. As shown in FIG.

The operation amount calculator 6a receives the signal of the operation lever 7 and converts it into a lever operation amount. The operation amount calculation unit 6a determines whether or not to connect the both tilting pump 2 and the boom cylinder 4 (whether to close the switching valve 5) based on the lever operation amount. For example, when the operation lever 7 is operated from the neutral position (when the lever operation amount is no longer zero), the control command value of the switching valve 5 is set to "open" in order to connect the double tilting pump 2 to the boom cylinder 4. set to The operation amount calculation unit 6a sets the tilt angle target value Do of the both tilting pumps 2 based on the lever operation amount. The discharge direction of the tilting pump 2 is determined according to the operating direction of the operating lever 7 (the sign of the lever operating amount). The tilt angle estimator 6b and the tilt angle controller 6c will be described later.

The pump control unit 6d outputs a control signal to the regulator 3 (solenoid valves 3a and 3b, which will be described later) based on the control command value for the regulator 3 set by the tilt angle control unit 6c. and control the discharge flow rate. The switching valve control section 6e outputs a control signal to the switching valve 5 based on the control command value for the switching valve 5 set by the operation amount calculating section 6a, and controls the switching valve 5 to open or close.

(others)
Returning to FIG. 2 , the flow paths 16 and 17 connected to the boom cylinder 4 are connected to the tank 9 via the flushing valve 8 . The flushing valve 8 communicates the low-pressure sides of the flow paths 16 and 17 with the tank 9 to eliminate excess or deficiency of hydraulic oil in the closed circuit. Flow paths 14 and 15 connected to both tilting pumps 2 are connected to tank 9 via relief valves 10a and 10b. The relief valves 10a and 10b are opened when the discharge pressure of the both tilting pumps 2 reaches a predetermined high pressure or higher, and discharges the high pressure hydraulic oil discharged from the both tilting pumps 2 to the tank 9. In other words, the relief valves 10a and 10b function as safety valves.

(regulator)
A configuration of the regulator 3 is shown in FIG. The regulator 3 includes a servo piston 3c connected to the swash plate 2c of the tilting pump 2, solenoid valves 3a and 3b, and a hydraulic pressure source 3d. The solenoid valves 3a, 3b reduce the pressure from the hydraulic source 3d according to the control signal from the controller 6, and apply it to the oil chambers 3e, 3f of the servo piston 3c. The solenoid valves 3a and 3b are driven in accordance with the operating direction of the operating lever 7, respectively. The servo piston 3c is driven by pressure output from the solenoid valves 3a and 3b, and stops at a balance position with springs 3g and 3h installed in the oil chambers 3e and 3f. As the angle (tilt angle) of the swash plate 2c changes in conjunction with the movement of the servo piston 3c, the discharge direction and the discharge flow rate of the both tilting pump 2 change.

(Configuration related to the present invention)
Next, the configuration related to the present invention in this embodiment will be described.

(Pressure sensor inside the regulator)
Pressure sensors 12a and 12b are provided on flow paths in the regulator 3 that connect the solenoid valves 3a and 3b and the oil chambers 3e and 3f of the servo piston 3c, respectively. Detection signals from the pressure sensors 12a and 12b are input to the controller 6 via signal lines.

(Controller 6)
The tilt angle estimator 6b shown in FIG. 3 converts the signals from the pressure sensors 12a and 12b into pressure values, and calculates the tilt angle estimated value De of both tilt pumps 2 based on these pressure values. Here, since the tilting angle of both tilting pumps 2 is determined by the position of the servo piston 3c (movement distance from the neutral position), in this embodiment, the estimated value of the position of the servo piston 3c is the tilting angle estimated value De. Calculate as An example of a method for calculating the tilt angle estimated value De will be described below.

In FIG. 4, the driving force ΔP·A of the servo piston 3c obtained by multiplying the differential pressure ΔP between the oil chambers 3e and 3f detected by the pressure sensors 12a and 12b by the pressure receiving area A of the servo piston 3c is the position of the servo piston 3c. is balanced with the resultant force of the spring force obtained by multiplying by the spring coefficient K and the frictional force Fc acting on the servo piston 3c, the tilt angle estimated value De can be calculated using the following equation.

Here, the frictional force Fc is a force acting in the direction opposite to the driving direction of the servo piston 3c due to the friction of the servo piston 3c and the swash plate 2c of the double tilting pump 2, and is identified based on experimental data, for example. value is used.

Returning to FIG. 3, the tilt angle control unit 6c adjusts the difference ΔD between the tilt angle estimated value De and the tilt angle target value Do calculated by the manipulated variable calculation unit 6a to zero (that is, A control command value for the regulator 3 (solenoid valves 3a, 3b) is calculated so that the tilt angle estimated value De of the shift pump 2 coincides with the tilt angle target value Do.

FIG. 5 is a flow chart showing the processing of the controller 6. As shown in FIG. Each step will be described in order below.

The controller 6 first calculates the tilt angle target value Do of the double tilt pump 2 based on the operation amount (lever operation amount) of the operation lever 7 (step S101). Specifically, the operation amount calculation unit 6a converts an input signal from the operation lever 7 into a lever operation amount, and the tilt angle control unit 6c converts the lever operation amount into a tilt angle target value Do.

Subsequent to step S101, the tilt angle estimator 6b of the controller 6 calculates the tilt angle estimated value De of the both tilt pumps 2 based on the differential pressure ΔP detected by the pressure sensors 12a and 12b (step S102). .

Following step S102, the tilt angle control unit 6c of the controller 6 calculates a difference ΔD by subtracting the tilt angle estimated value De from the tilt angle target value Do (step S103), and performs PID calculation on the difference ΔD. By doing so, the control command value Dc for the regulator 3 is calculated (step S104).

Following step S104, the pump control section 6d of the controller 6 outputs a control signal corresponding to the control command value Dc to the regulator 3 (solenoid valves 3a, 3b) (step S105), and returns the process to step S101.

(motion)
When the operation lever 7 is operated to the neutral position to hold the boom cylinder 4 stopped, the operation amount calculation unit 6a of the controller 6 sets the tilt angle target value Do of the both tilt pumps 2 to zero, The control command value for the valve 5 is set to "close". The tilt angle estimator 6b calculates the tilt angle estimated value De based on the pressure difference ΔP detected by the pressure sensors 12a and 12b and the frictional force Fc acting on the servo piston 3c. The tilt angle control unit 6c controls the regulator so that the difference ΔD between the tilt angle target value Do and the tilt angle estimated value De becomes zero (in this case, the tilt angle estimated value De becomes zero). 3 is calculated. Pump control unit 6d outputs a control signal corresponding to control command value Dc to regulator 3 (solenoid valves 3a and 3b). The switching valve control section 6e outputs a control signal to the switching valve 5 to close the switching valve 5 .

(effect)
In this embodiment, a dual tilting pump 2 capable of adjusting the discharge direction and flow rate of hydraulic oil according to the tilting angle, which is the angle of the swash plate 2c, a regulator 3 capable of adjusting the tilting angle, actuator 4; first flow paths 14, 16 connecting one input/output port 2a of both tilting pump 2 and one oil chamber 4a of hydraulic actuator 4; second flow paths 15, 17 connecting 2b and the other oil chamber 4b of the hydraulic actuator; , an operation lever 7 for instructing the operation of the hydraulic actuator 4, and a controller 6 for controlling the switching valve 5 and the regulator 3 according to the operation amount of the operation lever 7, the regulator 3 being connected to the swash plate 2c. and solenoid valves 3a and 3b for generating the operating pressure of the servo piston 3c according to the control signal from the controller 6, the first pressure detecting the operating pressure of the servo piston 3c Equipped with sensors 12a and 12b, the controller 6 calculates a tilt angle target value Do, which is the target value of the tilt angle, based on the operation amount of the control lever 7, and detects the servo pressure detected by the first pressure sensors 12a and 12b. Based on the operating pressure of the piston 3c and the frictional force Pc acting on the servo piston 3c, an estimated tilt angle De is calculated, and the target tilt angle Do and the estimated tilt angle are calculated. Control signals to the solenoid valves 3a and 3b are controlled so that the difference ΔD from De becomes small.

According to the present embodiment configured as described above, the tilt angle estimated value De is calculated based on the operating pressure of the servo piston 3c and the frictional force Fc acting on the servo piston 3c, and the operation amount of the operating lever 7 is calculated. The operating pressure of the servo piston 3c is adjusted such that the difference ΔD between the tilt angle target value Do and the tilt angle estimated value De calculated based on the above is reduced. As a result, the difference (residual error) between the stop position of the servo piston 3c and the target position is reduced regardless of the friction between the servo piston 3c and the swash plate 2c of the dual tilting pump 2. FIG. As a result, when the operating lever 7 is in the neutral position, the discharge flow rate of the double-tilt pump 2 can be brought close to zero, so an increase in the discharge pressure of the double-tilt pump 2 can be prevented, and noise and fuel consumption can be suppressed. It becomes possible to

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

In a swash plate type variable displacement pump such as the dual tilt pump 2, when high pressure is applied to one of the input/output ports, the swash plate is pushed by high pressure oil. The error in the value De increases. If a large error occurs in the tilt angle estimated value De, even if the pump control section 6d outputs a control signal to the regulator 3 according to the control command value calculated by the tilt angle control section 6c, the tilting of the tilting pump 2 on both sides will not occur. The turning angle will not be zero, and the discharge flow rate will occur. As a result, when the operating lever 7 is in the neutral position, the switching valve 5 is closed, which increases the discharge pressure of the double-tilt pump 2, resulting in noise and fuel consumption.

In this embodiment, regardless of the load acting on the swash plate 2c of the double-tilt pump 2, when the operating lever is in the neutral position, the discharge flow rate of the double-tilt pump is brought close to zero. 2. Suppresses the noise and the decrease in fuel consumption caused by the increase in discharge pressure.

FIG. 6 is a schematic diagram of the hydraulic drive system 200 in this embodiment.

In FIG. 6, flow paths 15 and 16 connected to both tilting pumps 2 are provided with pressure sensors 13a and 13b, respectively. The pressure sensors 13a, 13b are connected to the controller 6 via signal lines. The tilt angle estimator 6b of the controller 6 calculates the tilt angle estimated value De based on the pressure values of the pressure sensors 12a and 12b and the pressure values of the pressure sensors 13a and 13b.

FIG. 7 is a functional block diagram of the controller 6 in this embodiment.

The tilt angle estimator 6b in this embodiment calculates the pressure difference ΔP between the oil chambers 3e and 3f detected by the pressure sensors 12a and 12b and the pressure difference ΔPd between the input/output ports 2a and 2b detected by the pressure sensors 13a and 13b. Based on this, the tilt angle estimated value De is calculated.

FIG. 8 is a flow chart showing the processing of the controller 6 in this embodiment.

In step S102 in this embodiment, the tilt angle estimator 6b of the controller 6 calculates the pressure difference ΔP between the oil chambers 3e and 3f detected by the pressure sensors 12a and 12b and the input/output ports 2a and 2a detected by the pressure sensors 13a and 13b. Based on the pressure difference ΔPd of 2b, the tilt angle estimated value De is calculated using, for example, the following equation.

Here, C is a coefficient, and for example, a value calculated from simulations or experiments based on design values is used.

(effect)
The hydraulic excavator 100 according to this embodiment includes second pressure sensors 13a and 13b that detect the discharge pressure of the both tilting pumps 2, and the controller 6 detects the operation of the servo piston 3c detected by the first pressure sensors 12a and 12b. A tilt angle estimated value De is calculated based on the pressure, the frictional force Fc acting on the servo piston 3c, and the discharge pressure of both tilting pumps 2 detected by the second pressure sensors 13a and 13b.

According to this embodiment configured as described above, the tilt angle estimated value De is calculated based on the operating pressure of the servo piston 3c, the frictional force Fc acting on the servo piston 3c, and the discharge pressure of the double tilt pump 2. Then, the operating pressure of the servo piston 3c is adjusted so that the difference ΔD between the tilt angle target value Do calculated based on the operation amount of the control lever 7 and the tilt angle estimated value De becomes smaller. As a result, the difference between the stop position of the servo piston 3c and the target position ( residual) becomes smaller. As a result, when the operating lever 7 is in the neutral position, the discharge flow rate of the double-tilt pump 2 can be brought close to zero, so that it is possible to suppress noise and fuel consumption associated with an increase in the discharge pressure of the double-tilt pump. .

A third embodiment of the present invention will be described with a focus on differences from the first embodiment.

FIG. 9 is a functional block diagram of the controller 6 in this embodiment.

The switching valve control section 6e in this embodiment calculates the control command value Dc for the switching valve 5 based on the lever operation amount from the operation amount calculation section 6a and the tilt angle estimated value De from the tilt angle estimation section 6b. Then, a control signal corresponding to this control command value Dc is output to the switching valve 5 .

FIG. 10 is a flow chart showing the processing of the controller 6 in this embodiment.

In this embodiment, subsequent to step S105, the switching valve control section 6e of the controller 6 determines whether or not the tilt angle estimated value De is smaller than a predetermined threshold value (step S106). The threshold here is the tilting angle at which the discharge flow rate of the both tilting pump 2 becomes sufficiently small (specifically, when the switching valve 5 is closed, the discharge pressure of the both tilting pump 2 reaches the relief valve 10a, 10b) is set to a value smaller than the tilt angle that does not exceed the set pressure of 10b.

If it is determined as Yes in step S106, a close signal is output to the switching valve 5 (step S107), and the process returns to step S101. On the other hand, if it is determined No in step S106, an open signal is output to the switching valve 5 (step S108), and the process returns to step S101. As a result, the switching valve 5 is maintained in the open state from when the operating lever 7 is in the non-operating state until the tilt angle estimated value De becomes equal to or less than the threshold value.

(motion)
FIG. 11 is a diagram showing the operation of the hydraulic drive system in this embodiment in comparison with the first embodiment.

In the first embodiment, when the operation amount of the operating lever 7 becomes zero, the discharge flow rate of the double tilting pump 2 becomes zero after the lever operation amount. On the other hand, the switching valve 5 is closed when the lever operation amount becomes zero. Therefore, immediately after the switching valve 5 is closed, there is nowhere for the hydraulic oil discharged from the both tilting pump 2 to go, and the discharge pressure of the both tilting pump 2 rises to the set pressure of the relief valves 10a and 10b, causing noise and noise. fuel consumption worsens.

On the other hand, in the present embodiment, from when the lever operation amount becomes zero until the tilt angle estimated value De of the both tilting pump 2 falls below the threshold value (until the discharge flow rate of the both tilting pump 2 becomes sufficiently small), The switching valve 5 is kept open. As a result, a destination for the hydraulic oil discharged from the double tilt pump 2 is secured from when the lever operation amount becomes zero until the tilt angle of the double tilt pump 2 becomes sufficiently small. An increase in the discharge pressure of the tilting pump 2 is suppressed.

(effect)
The controller 6 in this embodiment keeps the switching valve 5 open from when the operation lever 7 is operated to the neutral position until the tilt angle estimated value De of the both tilting pumps 2 becomes equal to or less than a predetermined threshold value. Output a control signal.

According to the present embodiment constructed as described above, the switching valve 5 is kept open from when the operating lever 7 is operated to the neutral position until the discharge flow rate of the double tilting pump 2 becomes sufficiently small. Therefore, it is possible to prevent an increase in the discharge pressure of the both tilting pump 2, and to suppress noise and deterioration of fuel consumption.

(Other matters in general)
Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, although the above-described embodiment applies the present invention to a hydraulic excavator, the present invention is applicable not only to hydraulic excavators, but also to construction machines that drive hydraulic actuators with closed-circuit pumps. Moreover, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Furthermore, it is also possible to add part of the configuration of another embodiment to the configuration of one embodiment, to delete part of the configuration of one embodiment, or to replace it with part of another embodiment. It is possible.

DESCRIPTION OF SYMBOLS 1... Engine, 2... Double tilting pump, 2a, 2b... Input/output port, 2c... Swash plate, 3... Regulator, 3a, 3b... Solenoid valve, 3c... Servo piston, 3d... Oil pressure source, 3e, 3f... Oil chamber 3g, 3h spring 4 boom cylinder (hydraulic actuator) 4a bottom side oil chamber 4b rod side oil chamber 5 switching valve 6 controller 6a operation amount calculation unit 6b tilt Rotation angle estimation unit 6c Tilt angle control unit 6d Pump control unit 6e Switching valve control unit 7 Operation lever 8 Flushing valve 9 Tank 10a, 10b Relief valve 12a, 12b ... pressure sensor (first pressure sensor), 13a, 13b ... pressure sensor (second pressure sensor), 14, 16 ... flow path (first flow path), 15, 17 ... flow path (second flow path), 100 Hydraulic excavator (construction machine) 101 Traveling motor (hydraulic actuator) 102 Lower travel body 103 Swing motor (hydraulic actuator) 104 Upper swing body 105 Work device 106 Cab 107 Boom , 108 -- Arm, 109 -- Bucket, 110 -- Arm cylinder (hydraulic actuator), 111 -- Bucket cylinder (hydraulic actuator).

Claims (3)

a double-tilt pump that can adjust the discharge direction and discharge flow rate of hydraulic oil according to the tilt angle, which is the angle of the swash plate;
a regulator capable of adjusting the tilt angle;
a hydraulic actuator;
a first flow path connecting one input/output port of the double tilting pump and one oil chamber of the hydraulic actuator;
a second flow path connecting the other input/output port of the double tilting pump and the other oil chamber of the hydraulic actuator;
a switching valve capable of switching between communication and blocking of the first flow path and the second flow path;
an operation lever for instructing the operation of the hydraulic actuator;
a controller that controls the switching valve and the regulator according to the amount of operation of the control lever;
A construction machine in which the regulator includes a servo piston connected to the swash plate and an electromagnetic valve that generates an operating pressure for the servo piston according to a control signal from the controller,
A first pressure sensor that detects the operating pressure of the servo piston,
The controller calculates a tilt angle target value, which is a target value of the tilt angle, based on the operation amount of the control lever, and the operating pressure of the servo piston detected by the first pressure sensor and the servo piston An estimated tilt angle value, which is an estimated value of the tilt angle, is calculated based on the acting frictional force, and the electromagnetic valve is adjusted so that the difference between the estimated tilt angle value and the target tilt angle value becomes small. A construction machine characterized by controlling a control signal to In the construction machine according to claim 1,
comprising a second pressure sensor that detects the discharge pressure of the double tilting pump;
The controller controls the tilting pressure based on the operating pressure of the servo piston detected by the first pressure sensor, the frictional force acting on the servo piston, and the discharge pressure of the double tilting pump detected by the second pressure sensor. A construction machine characterized by calculating a turning angle estimated value. In the construction machine according to claim 1,
The controller outputs a control signal to open the switching valve from when the operation lever is operated to a neutral position until the tilt angle estimated value becomes equal to or less than a predetermined threshold value. construction machinery.

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