JP7314404B2 - working machine - Google Patents

Description

The present invention relates to work machines.

For example, a hydraulic excavator, which is one type of working machine, includes a working device including a boom, an arm, and a working tool (for example, an attachment such as a bucket). The operation of the work device is controlled by controlling the direction and flow rate of pressure oil supplied from a hydraulic pump to a plurality of hydraulic actuators, such as a boom cylinder that drives a boom, an arm cylinder that drives an arm, and a work implement cylinder that drives a work implement, using a plurality of control valves. The control valve controls the direction and flow rate of pressure oil supplied from the hydraulic pump to each hydraulic actuator, and has a meter-in throttle for controlling the flow rate of pressure oil supplied to the hydraulic actuator and a meter-out throttle for controlling the flow rate of pressure oil discharged from the hydraulic actuator to the tank.

In such a working machine, there is known a technique for reducing pressure loss by increasing the total opening area on the meter-out side by providing a bypass oil passage that directly guides the pressure oil discharged from the hydraulic actuator to the pressure oil tank without passing through a meter-out throttle in the meter-out passage that guides the pressure oil discharged from the hydraulic actuator to the tank. However, for example, when the working device operates in a direction in which it falls under its own weight, a load in the same direction as the operating direction acts on the hydraulic actuator, increasing the operating speed of the hydraulic actuator. At this time, if the amount of pressurized oil supplied to the meter-in side of the hydraulic actuator is insufficient, a breathing phenomenon (cavitation) may occur, and operability may deteriorate.

Regarding such a problem, for example, Patent Document 1 discloses a hydraulic actuator driven by pressure oil discharged from a hydraulic pump, a control valve that controls the supply and discharge of pressure oil to and from the hydraulic actuator according to the spool position, an operating device that controls the spool position of the control valve according to the operation amount and the operation direction, one or more meter-out flow paths through which the pressure oil discharged from the hydraulic actuator flows, and at least one variable throttle provided in the one meter-out flow path, or at least one provided in each of the plurality of meter-out flow paths. a load detector that detects a load applied to the hydraulic actuator by an external force and that is in the same direction as the operating direction of the hydraulic actuator; and a control device that reduces the opening area of the single variable throttle when there is one variable throttle, or the total value of the opening areas of the plurality of variable throttles when there are a plurality of variable throttles, in accordance with an increase in the magnitude of the load detected by the load detector.

JP 2016-075358 A

By the way, in the hydraulic system of the working machine, the speed of the hydraulic actuator may fluctuate due to the sudden change in the pressure of the pressurized oil in the circuit. For example, it is conceivable that the pressure of pressure oil in the circuit fluctuates due to torque control of a pump device including a hydraulic pump.

2. Description of the Related Art In a pump device, torque control is generally performed so that the torque of the hydraulic pump does not exceed the engine torque in order to prevent the engine, which is the prime mover for driving the hydraulic pump, from stalling. Since the torque of the hydraulic pump is expressed as the product of the pump pressure and the pump volume, the pump pressure is fed back to control the pump volume, thereby controlling the torque of the hydraulic pump to be below a certain value. Specifically, control is performed so that the higher the pump pressure, the smaller the pump volume.

In the prior art described above, for example, when the opening area of the variable throttle connected to the meter-out flow path is increased, the load pressure of the hydraulic actuator and the pump pressure are rapidly decreased, so control is performed such that the pump volume is rapidly increased. That is, since the flow rate of the pressurized oil supplied from the hydraulic pump to the hydraulic actuator increases sharply, operability may deteriorate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a working machine capable of suppressing deterioration of operability when the load pressure of a hydraulic actuator suddenly drops.

The present application includes a plurality of means for solving the above problems. To give an example, the present invention includes a variable displacement hydraulic pump driven by a prime mover, a hydraulic actuator driven by pressure oil discharged from the hydraulic pump, an operation lever for outputting an operation signal for operating the hydraulic actuator, a control valve for controlling the supply and discharge of pressure oil to the hydraulic actuator, a bypass oil passage for discharging pressure oil from a meter-out flow path through which the pressure oil discharged from the hydraulic actuator flows to a hydraulic oil tank without passing through the control valve, and pressure in the bypass oil passage. a bypass flow control valve that controls the flow of oil;and a control device that increases the tilt angle of the hydraulic pump as the pump pressure of the hydraulic pump decreases, the control device comprising:The opening area of the bypass flow control valve is controlled according to the load pressure of the hydraulic actuator, and even if the estimated value of the pump pressure after changing the opening area of the bypass flow control valve becomes a low value.By reducing the torque limit value that determines the upper limit of the torque of the hydraulic pump according to the decrease in the estimated value of the pump pressureHold the tilt angle before changing the opening areato controlshall be

ADVANTAGE OF THE INVENTION According to this invention, the deterioration of operability when the load pressure of a hydraulic actuator falls rapidly can be suppressed.

1 is a side view schematically showing the appearance of a hydraulic excavator that is an example of a working machine according to a first embodiment; FIG. FIG. 2 is a diagram showing a portion related to control of an arm cylinder extracted from the hydraulic circuit system according to the first embodiment, together with its peripheral configuration; 3 is a functional block diagram showing functions related to processing contents of the control device according to the first embodiment; FIG. It is a figure which shows the detail of the processing content of a bypass flow control valve opening area calculating part. It is a figure which shows the detail of the processing content of a pump pressure estimated value calculating part. It is a figure which shows the detail of the processing content of a pump volume correction calculating part. FIG. 5 is a diagram showing details of processing contents of a correction calculation unit; It is a figure which shows the detail of the processing content of a drive control part. FIG. 10 is a diagram showing a part related to control of an arm cylinder extracted from a hydraulic circuit system according to a second embodiment, together with its peripheral configuration; FIG. 9 is a functional block diagram showing functions related to processing contents of a control device according to a second embodiment; FIG. 5 is a diagram showing details of processing contents of a center bypass flow control valve opening area correction calculation unit; Formula 6 is shown as a table. FIG. 10 is a diagram showing details of processing contents of a drive control unit according to the second embodiment; FIG. 11 is a diagram showing a portion related to control of an arm cylinder extracted from a hydraulic circuit system according to a third embodiment, together with its peripheral configuration; FIG. 11 is a functional block diagram showing functions related to processing contents of a control device according to a third embodiment; FIG. 10 is a diagram showing details of processing contents of a second control valve correction calculation unit; Formula 7 is shown as a table. FIG. 10 is a diagram showing details of processing contents of a drive control unit according to the second embodiment;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, a hydraulic excavator will be described as an example of a working machine, but the present invention can also be applied to other working machines having working devices driven by hydraulic actuators.

<First Embodiment>
A first embodiment of the present invention will be described with reference to FIGS. 1 to 8. FIG.

FIG. 1 is a side view schematically showing the appearance of a hydraulic excavator, which is an example of a working machine according to the present embodiment.

In FIG. 1, a hydraulic excavator 100 is composed of a vehicle body 1B composed of a traveling body 3 having a pair of left and right crawler belts 1 and 2, a revolving body 4 mounted on the traveling body 3, and a multi-joint type work device 1A provided at the front central portion of the revolving body 4.

The work device 1A includes a boom 5 whose one end is rotatably pin-connected to the revolving body 4, an arm 6 whose one end is rotatably pin-connected to the other end of the boom 5, and a bucket 7 which is a work tool (attachment) rotatably pin-connected to the other end of the arm 6. The work device 1A is also provided with a pair of left and right boom cylinders 13 and 14, which are hydraulic cylinders for vertically rocking the boom 5, an arm cylinder 15 for vertically rocking the arm 6 with respect to the boom (forward and backward), and an attachment cylinder 16 for vertically rocking the attachment (here, the bucket 7) with respect to the arm 6. That is, the working device 1A is driven by the expansion and contraction operations of the hydraulic cylinders 13, 14, 15, and 16. As shown in FIG. 1, only the boom cylinder 13 on the left side is illustrated, and the symbols of the boom cylinder 14 on the right side are shown in parentheses and the illustration thereof is omitted. The working tool provided at the tip of the working device 1A is not limited to the bucket 7, and can be replaced with, for example, a grapple, a cutter, a breaker, or any other attachment depending on the content of the work.

The traveling body 3 is provided with traveling hydraulic motors 11 and 12 that drive the pair of left and right crawler belts 1 and 2, respectively. In FIG. 1, only the left crawler belt 1 and the traveling hydraulic motor 11 are illustrated, and the right crawler belt 2 and the traveling hydraulic motor 12 are shown in parentheses and omitted from the illustration.

The revolving structure 4 is provided with an operator's cab 8 in which an operator rides, a machine room 9 that houses a prime mover (for example, an engine 17 (described later)) and a hydraulic pump 18 (described later), a counterweight 10 provided behind the revolving structure 4, and a swing hydraulic motor (not shown) that drives the revolving structure 4 to swing with respect to the traveling structure 3. In the operator's cab 8, each hydraulic actuator of the hydraulic excavator 100, that is, the hydraulic actuators of the working device 1A such as the boom cylinders 13 and 14, the arm cylinder 15, and the bucket cylinder 16, the traveling hydraulic motors 11 and 12, and the turning hydraulic motor (not shown) are provided with operation levers for outputting operation signals for operating the hydraulic motors.

FIG. 2 is a diagram showing a portion related to control of an arm cylinder extracted from a hydraulic circuit system provided in a hydraulic excavator, together with its peripheral configuration.

2, the hydraulic circuit system according to the present embodiment includes a prime mover (here, an engine 17) such as an engine or an electric motor; a variable displacement hydraulic pump 18 driven by the engine 17, which is the prime mover; a control valve 27 (flow rate control valve) connected to a discharge line (supply oil passage) of the hydraulic pump 18 for controlling the supply and discharge (flow rate and direction) of pressurized oil supplied from the hydraulic pump 18 to the hydraulic actuator (here, arm cylinder 15); A bypass flow control valve 32 for controlling the flow rate of the pressure oil in the bypass oil passage 33, a pilot pump 28 for generating pilot pressure, and a control device 19 for controlling the operation of the entire hydraulic excavator 100 including the hydraulic circuit system.

The pilot pump 28 is a fixed displacement hydraulic pump that generates pilot pressure used for controlling hydraulic equipment. The pressure oil discharged from the pilot pump 28 to the pilot circuit is returned to the hydraulic oil tank 30 via the pilot relief valve 29, and the pressure of the pilot circuit is maintained at the set pressure of the pilot relief valve 29.

The hydraulic pump 18 is of a variable displacement type, and is configured to perform control to change the displacement of the hydraulic pump 18 by controlling an electronic pump regulator 20 according to a control signal from the control device 19, that is, control to change the tilting angle of the hydraulic pump 18. The pump regulator 20 controls the pump capacity (pump capacity) of the hydraulic pump 18 so that the discharge flow rate of the hydraulic pump 18 becomes a target value (regulator command current value 41 to be described later) transmitted as a control signal from the control device 19 . A pressure sensor 34 for detecting the discharge pressure from the hydraulic pump 18 is provided in the supply oil passage of the hydraulic pump 18 . A detection result of the pressure sensor 34 (hereinafter referred to as pump pressure 34 ) is transmitted to the control device 19 .

The control valve 27 is connected to the supply oil passage of the hydraulic pump 18, and is driven by a control signal (pilot pressure) guided to the pressure receiving portion via the electromagnetic proportional valves 31a and 31b controlled by the control device 19, thereby controlling the direction and flow rate of the pressure oil supplied to the arm cylinder 15.

For example, when the control valve 27 is driven to one side (for example, the right side in FIG. 1) by the pilot pressure from the electromagnetic proportional valve 31a, the pressure oil discharged from the hydraulic pump 18 is supplied to the bottom side oil chamber of the arm cylinder 15 via the control valve 27, and the pressure oil discharged from the rod side oil chamber is guided to the hydraulic oil tank 30 via the control valve 27. That is, the oil passage connecting the control valve 27 and the bottom-side oil chamber of the arm cylinder 15 is the meter-in passage, and the oil passage connecting the rod-side oil chamber of the arm cylinder 15 and the control valve 27 is the meter-out oil passage. At this time, the arm cylinder 15 is driven to extend, and an arm cloud operation is performed.

When the control valve 27 is driven to the other side (for example, the left side in FIG. 1) by the pilot pressure from the electromagnetic proportional valve 31b, the pressure oil discharged from the hydraulic pump 18 is supplied to the rod side oil chamber of the arm cylinder 15 via the control valve 27, and the pressure oil discharged from the bottom side oil chamber is guided to the hydraulic oil tank 30 via the control valve 27. That is, the oil passage connecting the control valve 27 and the rod-side oil chamber of the arm cylinder 15 is the meter-in passage, and the oil passage connecting the bottom-side oil chamber of the arm cylinder 15 and the control valve 27 is the meter-out oil passage. At this time, the arm cylinder 15 is retracted, and an arm dump operation is performed.

Pressure sensors 35a and 35b are provided in the oil passages connected to the bottom side and rod side oil chambers of the arm cylinder 15, respectively. The pressure sensor 35a detects the pressure on the bottom side of the arm cylinder 15 (hereinafter referred to as bottom pressure 35a), and the pressure sensor 35b detects the pressure on the rod side (hereinafter referred to as rod pressure 35b).

The operation lever 26 outputs operation signals 26a and 26b to the control device 19 according to the direction and amount of operation input by the operator. The operation signal 26a instructs extension of the hydraulic actuator (arm cylinder 15), and the operation signal 26b instructs retraction of the hydraulic actuator (arm cylinder 15). The control device 19 generates a control signal (pilot pressure) for driving the control valve 27 by generating control signals for controlling the electromagnetic proportional valves 31a and 31b according to the operation signals 26a and 26b from the control lever 26 . That is, the operating lever 26 outputs an operating signal for operating the hydraulic actuator (arm cylinder 15) to the control device 19, and the control device 19 drives the hydraulic actuator (arm cylinder 15) based on the operating signal from the operating lever 26.

The bypass flow control valve 32 provided in the bypass oil passage 33 is driven by a control signal (bypass flow control valve command command pressure) guided to the pressure receiving portion via the electromagnetic proportional valve 31c controlled by the control device 19, thereby controlling the flow rate of the pressure oil in the bypass oil passage 33. A bypass flow control valve command pressure is detected by a pressure sensor 200 provided in a bypass control pilot pipe 201 and transmitted to the control device 19 .

FIG. 3 is a functional block diagram showing functions related to processing contents of the control device.

As shown in FIG. 3, the control device 19 has, as functional units, a load calculation unit 21, a bypass flow control valve opening area calculation unit 22, a pump pressure estimation value calculation unit 23, a pump volume correction calculation unit 24, and a drive control unit 25.

The load calculation unit 21 calculates an arm cylinder load 36, which is the load (load pressure) of the arm cylinder 15, based on the bottom pressure (detection value of the pressure sensor 35a) and the rod pressure (detection value of the pressure sensor 35b) of the arm cylinder 15. That is, in the load calculation unit 21, the arm cylinder load F (arm cylinder load 36) is obtained by the following (Equation 1) using the previously stored arm cylinder bottom area A_Btm and rod area A_Rod, arm cylinder bottom pressure P_Btm (arm cylinder bottom pressure 35a), and rod pressure P_Rod (arm cylinder rod pressure 35b).

The bypass flow control valve opening area calculation unit 22 calculates a bypass flow control valve opening area target value 37 based on the operation signal (lever operation amount 26b) related to the arm dump operation from the operation lever 26 and the arm cylinder load 36 from the load calculation unit 21.

FIG. 4 is a diagram showing the details of the processing contents of the bypass flow control valve opening area calculator.

As shown in FIG. 4, the bypass flow control valve opening area calculation unit 22 calculates the bypass flow control valve opening area target value 37 based on a table that predetermines the relationship between the actuator load 36 and the bypass flow control valve opening area target value 37. The table used in the bypass flow control valve opening area calculator 22 is set such that the bypass flow control valve opening area target value 37 is fully closed when the arm cylinder load 36 is f2 (positive value) or more. When the arm cylinder load 36 is f2 or less, the bypass flow control valve opening area target value 37 is set to increase toward a predetermined maximum value for each lever operation amount 26b as the arm cylinder load 36 decreases. Here, the maximum value of the bypass flow control valve opening area target value 37 is determined to increase as the lever operation amount increases. Furthermore, when the arm cylinder load 36 is f1 (negative value) or less, the bypass flow control valve opening area target value 37 is set to maintain the maximum value.

The pump pressure estimated value calculation unit 23 calculates the bypass flow control valve opening area target value 37 from the bypass flow control valve opening area calculation unit 22, the operation signal (lever operation amount 26b) from the operation lever 26, the detection result from the pressure sensor 35a (bottom pressure 35a of the arm cylinder 15), the detection result from the pressure sensor 35b (rod pressure 35b of the arm cylinder 15), the detection result of the pressure sensor 34 (pump pressure 34 of the hydraulic pump 18), and the pressure sensor 20. Based on the detection result of 0 (bypass flow control valve command pressure), an estimated value of the discharge pressure of the hydraulic pump 18 after the bypass flow control valve 32 is opened (pump pressure estimated value 38) is calculated.

FIG. 5 is a diagram showing the details of the processing contents of the pump pressure estimated value calculator.

As shown in FIG. 5 , the pump pressure estimated value calculator 23 includes a flow control valve opening area calculator 42, an arm cylinder bottom pressure estimated value calculator 44, an arm cylinder rod pressure estimated value calculator 46, and a pump pressure estimated value calculator 50.

The flow control valve opening area calculation unit 42 calculates the flow control valve opening area 43 based on a table that predetermines the relationship between the lever operation amount 26b and the flow control valve opening area 43, which is the opening area of the meter-out flow path of the control valve 27. The table used in the pump pressure estimated value calculator 23 is determined so that the flow control valve opening area 43 increases as the lever operation amount 26b increases.

The bypass flow control valve opening calculation unit 210 calculates the current bypass flow control valve opening area 220 based on a table that predetermines the relationship between the bypass flow control valve command pressure (detected by the pressure sensor 200) and the opening area.

Arm cylinder bottom pressure estimated value calculation unit 44 calculates arm cylinder bottom pressure estimated value 45 based on bypass flow control valve opening area target value 37, flow control valve opening area 43, and arm cylinder bottom pressure 35a. That is, the arm cylinder bottom pressure estimated value P'_Btm (arm cylinder bottom pressure estimated value 45) in the arm cylinder bottom pressure estimated value calculation unit 44 is calculated from the bypass flow control valve opening area target value A'_BP (bypass flow control valve opening area target value 37), the meter-out opening area A_MO of the flow control valve 27 (flow control valve opening area 43), the arm cylinder bottom pressure P_Btm (arm cylinder bottom pressure 35a), and the current bypass flow control valve opening area A_BP (220). ) using the following (Equation 2).

Arm cylinder rod pressure estimated value calculation unit 46 calculates arm cylinder rod pressure estimated value 49 based on previously stored arm cylinder bottom area 47 and arm cylinder rod area 48, arm cylinder bottom pressure 35a, arm cylinder rod pressure 35b, and arm cylinder bottom pressure estimated value 45. That is, in the arm cylinder rod pressure estimated value calculation unit 46, the arm cylinder rod pressure estimated value P'_Rod (arm cylinder rod pressure estimated value 49) is calculated using the arm cylinder bottom area A_Btm (arm cylinder bottom area 47) and the arm cylinder rod area A_Rod (arm cylinder rod area 48), the arm cylinder bottom pressure P_Btm (arm cylinder bottom pressure 35a), and the arm cylinder rod pressure P_Rod (arm cylinder rod pressure 35b) stored in advance. 3).

Pump pressure estimated value calculation unit 50 calculates pump pressure estimated value P′_Pmp (pump pressure estimated value 38 ) based on pump pressure 34 , arm cylinder rod pressure 35 b and arm cylinder rod pressure estimated value 49 . That is, in the estimated pump pressure value calculation unit 50, the estimated pump pressure value P'_Pmp (estimated pump pressure value 38) is obtained by the following (Equation 4) using the pump pressure P_Pmp (pump pressure 34), the arm cylinder rod pressure P_Rod (arm cylinder rod pressure 35b), and the estimated arm cylinder rod pressure P'_Rod (estimated arm cylinder rod pressure value 49).

The pump volume correction calculator 24 calculates a corrected pump volume target value 39 based on the lever operation amount 26b, the pump pressure 34, and the pump pressure estimated value 38. FIG.

FIG. 6 is a diagram showing the details of the processing contents of the pump volume correction calculator.

As shown in FIG. 6 , the pump volume correction calculator 24 has a pump volume calculator 51 and a correction calculator 53 .

The pump volume calculation unit 51 calculates a pump volume target value 52 based on a table that predetermines the relationship between the lever operation amount 26b and the pump volume target value q (pump volume target value 52). The table used in the pump volume calculator 51 is determined so that the pump volume q increases as the lever operation amount 26b increases.

The correction calculator 53 calculates a corrected pump volume target value 39 based on the pump volume target value 52 , the pump pressure 34 , and the pump pressure estimated value 38 .

FIG. 7 is a diagram showing the details of the processing contents of the correction calculation unit.

As shown in FIG. 7 , the correction calculator 53 has a pump capacity limit value calculator 54 and a minimum value selector 56 .

The pump capacity limit value calculation unit 54 first uses the pump pressure P_Pmp (pump pressure 34), the pump pressure estimated value P′_Pmp (pump pressure estimated value 38), and the preset torque limit value T of the hydraulic pump 18 to obtain the torque limit value T′ after the bypass flow control valve is opened by the following (Equation 5).

After the bypass flow control valve is opened, the torque limit value T is replaced with the torque limit value T', and the pump volume limit value q (pump volume limit value 55) at this time is output. As a result, it is possible to suppress the change in the pump volume q that depends on the change in the pump pressure P_Pmp before and after the bypass is opened.

The minimum value selection unit 56 selects the minimum value between the pump volume limit value 55 calculated by the pump volume limit value calculation unit 54, that is, the pump volume q when the torque limit value is T′ and the pump volume target value 52 according to the operator's lever operation, and outputs it as the corrected pump volume target value 39. In other words, even when the estimated value of the pump pressure after changing the opening area of the bypass flow control valve 32 becomes a low value, the minimum value selection unit 56 outputs the corrected pump volume target value to maintain the tilt angle of the hydraulic pump 18 before the pump pressure of the hydraulic pump 18 (discharge pressure of the hydraulic pump 18) decreases.

The drive control unit 25 calculates and outputs a command current value 40 for the proportional solenoid valve 31c and a command current value 41 for the pump regulator 20 based on the bypass flow control valve opening area target value 37 and the corrected pump volume target value 39.

FIG. 8 is a diagram showing the details of the processing contents of the drive control unit.

As shown in FIG. 8 , the drive control section 25 has an electromagnetic proportional valve command current computing section 58 and a regulator command current computing section 59 .

The proportional solenoid valve command current calculation unit 58 calculates the proportional solenoid valve command current value 40 for the proportional solenoid valve 31c based on a table that defines the relationship between the bypass flow control valve opening area target value 37 and the proportional solenoid valve command current value 40 in advance. In the table used in the electromagnetic proportional valve command current calculator 58, the electromagnetic proportional valve command current value 40 is 0 (zero) when the bypass flow control valve opening area target value 37 is 0 (zero), and the electromagnetic proportional valve command current value 40 is set to increase as the bypass flow control valve opening area target value 37 increases.

The regulator command current calculation unit 59 calculates a control signal (regulator command current value 41) for the pump regulator 20 based on a table that defines the relationship between the pump displacement target value 39 and the regulator command current value 41 in advance. In the table used by the regulator command current calculator 59, the regulator command current value 41 is 0 (zero) when the pump volume target value 39 is 0 (zero), and the regulator command current value 41 is set to increase as the pump volume target value 39 increases.

The operation of the present embodiment described above will be described in association with the operation of the arm.

When the arm 6 is dumped from the cloud state and the arm 6 is moved in the direction of its own weight (direction in which its own weight falls), the load acting on the arm cylinder 15 acts in the same direction as the arm cylinder 15 operates, so the speed at which the arm cylinder 15 contracts increases. At this time, the opening area of the bypass flow control valve 32 is controlled to be small, and the bypass oil passage 33 leading to the hydraulic oil tank 30 is narrowed, thereby suppressing the contraction speed of the arm cylinder 15 . On the other hand, when the arm 6 is dumped and the arm 6 is moved in a direction opposite to its own weight, the load acting on the arm cylinder 15 acts in the direction opposite to the direction in which the arm cylinder 15 moves. At this time, the opening area of the bypass flow control valve 32 is controlled to be large, and in an attempt to reduce pressure loss, the pressure of the hydraulic pump 18 decreases as the opening area of the bypass flow control valve 32 increases (see pump pressure P' in FIG. 7). When the pump pressure decreases, in normal control, the tilt angle of the hydraulic pump 18 is increased to increase the discharge flow rate. In the present invention, instead of being controlled to increase the tilt angle of the hydraulic pump 18 in normal control, the tilt angle of the hydraulic pump 18 is controlled to be held. As a result, an increase in the speed of the arm cylinder 15 not intended by the operator is suppressed.

The effect of this embodiment configured as above will be described.

In the prior art, for example, when the opening area of the variable throttle connected to the meter-out flow path is increased, the load pressure of the hydraulic actuator and the pump pressure are rapidly decreased, so control is performed to rapidly increase the pump displacement. That is, since the flow rate of the pressurized oil supplied from the hydraulic pump to the hydraulic actuator increases sharply, operability may deteriorate.

In contrast, in the present embodiment, a variable displacement hydraulic pump driven by a prime mover, a hydraulic actuator driven by pressure oil discharged from the hydraulic pump, a control lever for outputting an operation signal for operating the hydraulic actuator, a control valve for controlling the supply and discharge of pressure oil to and from the hydraulic actuator, a bypass oil passage for discharging pressure oil from the meter-out passage through which the pressure oil discharged from the hydraulic actuator flows to the hydraulic oil tank without passing through the control valve, a bypass flow control valve for controlling the flow rate of the pressure oil in the bypass oil passage, and a load pressure on the hydraulic actuator. Accordingly, the opening area of the bypass flow control valve is controlled, and even when the estimated value of the pump pressure after changing the opening area of the bypass flow control valve becomes a low value, the tilt angle before changing the opening area is maintained.

That is, in the present embodiment, a change in the pump volume with respect to a change in the opening of the bypass flow control valve is predicted, and the pump volume target value 39 (a value based on the regulator command current value 41, which is the command value for the pump regulator 20 of the hydraulic pump 18) is calculated according to the change, so deterioration of operability can be suppressed.

In particular, when the opening change of the bypass flow control valve is large, the load pressure of the hydraulic actuator to be operated decreases rapidly, and the amount of change is also large. Therefore, in the conventional art, the discharge flow rate (discharge pressure) of the hydraulic pump controlled by the pump regulator is controlled to increase rapidly, and it is considered that the operability is further deteriorated. , a higher effect can be obtained.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to FIGS. 9 to 13. FIG. In this embodiment, only differences from the first embodiment will be explained, and the same reference numerals will be given to the same members as in the first embodiment, and the explanation will be omitted.

This embodiment shows a case where the present invention is applied to a center bypass type hydraulic circuit system.

FIG. 9 is a diagram showing a portion related to control of the arm cylinder extracted from the hydraulic circuit system according to the present embodiment, along with the peripheral configuration.

9, the hydraulic circuit system according to the present embodiment includes a prime mover such as an engine or an electric motor (here, an engine 17), a variable displacement hydraulic pump 18 driven by the engine 17, which is the prime mover, a center bypass type control valve 27A (flow rate control valve) connected to a discharge line (supply oil passage) of the hydraulic pump 18 and controlling the supply and discharge (flow rate and direction) of pressure oil supplied from the hydraulic pump 18 to the hydraulic actuator (here, the arm cylinder 15); A bypass flow control valve 32 that controls the flow rate of the pressure oil in the bypass oil passage 33; a center bypass oil passage 60 that connects the hydraulic oil tank 30 and a supply oil passage that supplies the pressure oil discharged from the hydraulic pump 18 to the control valve 27A; A center bypass flow control valve 61 that controls the flow rate of pressure oil led to the hydraulic oil tank 30 via the center bypass oil passage 60 by changing the area, a pilot pump 28 that generates pilot pressure, and a control device 19A that controls the operation of the entire hydraulic excavator 100 including the hydraulic circuit system.

A center bypass flow control valve 61 provided in the center bypass oil passage 60 is driven by a control signal (pilot pressure) guided to a pressure receiving portion via an electromagnetic proportional valve 62 controlled by the control device 19A, thereby controlling the flow rate of pressure oil in the center bypass oil passage 60.

FIG. 10 is a functional block diagram showing functions related to processing contents of the control device according to the present embodiment.

As shown in FIG. 10, the control device 19A has, as functional units, a load calculation unit 21, a bypass flow control valve opening area calculation unit 22, a pump pressure estimation value calculation unit 23, a pump volume correction calculation unit 24, a drive control unit 25A, and a center bypass flow control valve opening area correction calculation unit 63.

A center bypass flow control valve opening area correction calculator 63 calculates a post-correction center bypass flow control valve opening area target value 64 based on the lever operation amount 26 b , the pump pressure 34 , and the pump pressure estimated value 38 .

FIG. 11 is a diagram showing the details of the processing contents of the center bypass flow control valve opening area correction calculator.

As shown in FIG. 11 , the center bypass flow control valve opening area correction calculator 63 has a center bypass flow control valve opening area calculator 66 and a correction calculator 68 .

A center bypass flow control valve opening area calculation unit 66 calculates a center bypass flow control valve opening area target value 67 based on a table that predetermines the relationship between the lever operation amount 26b and the center bypass flow control valve opening area target value A_CB (center bypass flow control valve opening area target value 67). The table used in the center bypass flow control valve opening area calculator 66 is determined such that as the lever operation amount 26b increases from 0 (zero), the center bypass flow control valve opening area target value 67 sharply decreases, and then gradually decreases as the lever operation amount 26b increases.

The correction calculator 68 calculates the corrected center bypass flow control valve opening area target value 64 based on the center bypass flow control valve opening area target value 67 , the pump pressure 34 , and the pump pressure estimated value 38 . Specifically, the correction calculation unit 68 sets the tank pressure to 0 (zero) MPa, and uses the center bypass flow control valve opening area target value A_CB (center bypass flow control valve opening area target value 67), the pump pressure P_Pmp (pump pressure 34), and the pump pressure estimated value P'_Pmp (pump pressure estimated value 38) to calculate the corrected center bypass flow control valve opening area target value A'_CB (center bypass flow control valve opening area target value 64) by the following formula: 6).

FIG. 12 shows the above (formula 6) as a table.

The corrected center bypass flow control valve opening area target value A'_CB (center bypass flow control valve opening area target value 64) can also be obtained from the table shown in FIG.

Based on the bypass flow control valve opening area target value 37, the corrected pump volume target value 39, and the corrected center bypass flow control valve opening area target value 64, the drive control unit 25A calculates and outputs a command current value 40 for the electromagnetic proportional valve 31c, a command current value 41 for the pump regulator 20, and a command current value 65 for the electromagnetic proportional valve 62.

FIG. 13 is a diagram showing details of the processing contents of the drive control unit according to the present embodiment.

As shown in FIG. 13, the drive control unit 25A has a proportional solenoid valve command current calculator 58 (for the proportional solenoid valve 31c), a regulator command current calculator 59, and a proportional solenoid valve command current calculator 69 (for the proportional solenoid valve 62).

A proportional solenoid valve command current calculation unit 64 calculates a proportional solenoid valve command current value 65 for the proportional solenoid valve 62 based on a table that predetermines the relationship between the center bypass flow control valve opening area target value 64 and the proportional solenoid valve command current value 40. In the table used in the proportional solenoid valve command current calculator 69, the proportional solenoid valve command current value 65 is 0 (zero) when the center bypass flow control valve opening area target value 64 is 0 (zero), and the proportional solenoid valve command current value 65 is set to increase as the center bypass flow control valve opening area target value 64 increases.

Other configurations are the same as those of the first embodiment.

The same effects as those of the first embodiment can be obtained in the present embodiment configured as described above.

In addition, in the present embodiment, in the center bypass type hydraulic circuit system, not only the pump volume of the hydraulic pump 18 but also the control of the center bypass flow control valve 61 is corrected, thereby suppressing a change in the branch flow balance of the pressure oil between the arm cylinder 15 and the center bypass oil passage 60, thereby suppressing deterioration of operability.

<Third Embodiment>
A third embodiment of the present invention will be described with reference to FIGS. 14 to 18. FIG. In this embodiment, only differences from the first embodiment will be explained, and the same reference numerals will be given to the same members as in the first embodiment, and the explanation will be omitted.

This embodiment shows a case where the present invention is applied to a hydraulic circuit system in which a plurality of hydraulic actuators are driven by a hydraulic pump.

14, the hydraulic circuit system according to the present embodiment includes a prime mover (here, an engine 17) such as an engine or an electric motor; a variable displacement hydraulic pump 18 driven by the engine 17, which is the prime mover; a control valve 27 (flow rate control valve) connected to a discharge line (supply oil passage) of the hydraulic pump 18 and controlling supply and discharge (flow rate and direction) of pressure oil supplied from the hydraulic pump 18 to the hydraulic actuator (here, the arm cylinder 15); Here, a control valve 71 (flow rate control valve: second control valve) that controls the supply and discharge (flow rate and direction) of pressure oil supplied to the cylinder 70 (second hydraulic actuator), a bypass oil passage 33 that discharges pressure oil to the hydraulic oil tank 30 from the meter-out flow path through which the pressure oil discharged from the arm cylinder 15 to the hydraulic oil tank 30 flows without passing through the control valve 27, a bypass flow control valve 32 that controls the flow rate of the pressure oil in the bypass oil passage 33, and a pilot pump 28 that generates the pilot pressure. and a control device 19B that controls the operation of the entire hydraulic excavator 100 including the hydraulic circuit system.

The control valve 71 is connected to the supply oil passage of the hydraulic pump 18, and is driven by a control signal (pilot pressure) guided to the pressure receiving portion via the electromagnetic proportional valves 72a and 72b controlled by the control device 19B, thereby controlling the direction and flow rate of the pressure oil supplied to the cylinder 70.

For example, when the control valve 71 is driven to one side (for example, the right side in FIG. 1) by the pilot pressure from the electromagnetic proportional valve 72a, the pressure oil discharged from the hydraulic pump 18 is supplied to the bottom side oil chamber of the cylinder 70 via the control valve 71, and the pressure oil discharged from the rod side oil chamber is guided to the hydraulic oil tank 30 via the control valve 71. That is, the oil passage connecting the control valve 71 and the bottom-side oil chamber of the cylinder 70 is the meter-in passage, and the oil passage connecting the rod-side oil chamber of the cylinder 70 and the control valve 71 is the meter-out oil passage. At this time, the cylinder 70 is driven to extend.

When the control valve 71 is driven to the other side (for example, the left side in FIG. 1) by the pilot pressure from the electromagnetic proportional valve 72b, the pressure oil discharged from the hydraulic pump 18 is supplied to the rod-side oil chamber of the cylinder 70 via the control valve 71, and the pressure oil discharged from the bottom-side oil chamber is guided to the hydraulic oil tank 30 via the control valve 71. That is, the oil passage connecting the control valve 71 and the rod-side oil chamber of the cylinder 70 is the meter-in passage, and the oil passage connecting the bottom-side oil chamber of the cylinder 70 and the control valve 71 is the meter-out oil passage. At this time, the cylinder 70 is retracted.

Pressure sensors 74a and 74b are provided in the oil passages connected to the bottom side and rod side oil chambers of the cylinder 70, respectively. The pressure sensor 74a detects the pressure on the bottom side of the cylinder 70, and the pressure sensor 74b detects the pressure on the rod side, and transmits them to the control device 19B.

The operation lever 73 (second operation lever) outputs operation signals 73a and 73b to the control device 19B according to the direction and amount of operation input by the operator. The operation signal 73a instructs extension of the hydraulic actuator (cylinder 70), and the operation signal 73b instructs retraction of the hydraulic actuator (cylinder 70). The control device 19B generates control signals (pilot pressure) for driving the control valve 71 by generating control signals for controlling the electromagnetic proportional valves 72a and 72b according to the operation signals 73a and 73b from the control lever 73. FIG. That is, the operation lever 73 outputs an operation signal for operating the hydraulic actuator (cylinder 70) to the control device 19B, and the control device 19B drives the hydraulic actuator (cylinder 70) based on the operation signal from the operation lever 73.

FIG. 15 is a functional block diagram showing functions related to processing contents of the control device according to the present embodiment.

As shown in FIG. 15, the control device 19B has, as functional units, a load calculation unit 21, a bypass flow control valve opening area calculation unit 22, a pump pressure estimation value calculation unit 23, a pump volume correction calculation unit 24, a drive control unit 25B, and a second control valve correction calculation unit 75.

A second control valve correction calculation unit 75 calculates a meter-in opening area target value 76 of the control valve 71 (second control valve) based on the pump pressure estimated value 38, the pump pressure 34, the lever operation amount 73b of the operation lever 73 (second operation lever), and the rod pressure 74b of the cylinder 70 (second hydraulic actuator).

FIG. 16 is a diagram showing the details of the processing contents of the second control valve correction calculator.

As shown in FIG. 16 , the second control valve correction calculation section 75 has a second control valve meter-in opening area calculation section 78 and a correction calculation section 80 .

A second control valve meter-in opening area calculation unit 78 calculates a second control valve meter-in opening area target value 79 based on a table that predetermines the relationship between the lever operation amount 73b of the second control lever and the second control valve meter-in opening area target value A_MI2 (second control valve meter-in opening area target value 79). The table used in the second control valve meter-in opening area calculator 78 is determined so that the second control valve meter-in opening area target value 79 increases as the lever operation amount 73b increases from 0 (zero).

The correction calculation unit 80 calculates the corrected second control valve meter-in opening area target value 76 based on the second control valve meter-in opening area target value 79, the pump pressure 34, the pump pressure estimated value 38, and the rod pressure 74b of the second cylinder. Specifically, the correction calculation unit 80 uses the second control valve meter-in opening area target value A_MI2 (second control valve meter-in opening area target value 79), pump pressure P_Pmp (pump pressure 34), pump pressure estimated value P'_Pmp (pump pressure estimated value 38), and second cylinder rod pressure P_Rod2 (second cylinder rod pressure 74b) to obtain the second control valve meter-in opening area target value A'_MI2. (Second control valve meter-in opening area target value 76) is obtained by the following (Equation 7).

FIG. 17 shows the above (Formula 7) as a table.

The corrected second control valve meter-in opening area target value A'_MI2 (second control valve meter-in opening area target value 76) can also be obtained from the table shown in FIG.

The drive control unit 25B calculates and outputs a command current value 40 for the electromagnetic proportional valve 31c, a command current value 41 for the pump regulator 20, and a command current value 77 for the electromagnetic proportional valve 72b based on the bypass flow control valve opening area target value 37, the corrected pump volume target value 39, and the corrected second control valve meter-in opening area target value 76.

FIG. 18 is a diagram showing details of processing contents of the drive control unit according to the present embodiment.

As shown in FIG. 18, the drive control unit 25B has a proportional solenoid valve command current calculator 58 (for the proportional solenoid valve 31c), a regulator command current calculator 59, and a proportional solenoid valve command current calculator 81 (for the proportional solenoid valve 72b).

The proportional solenoid valve command current calculation unit 81 calculates the proportional solenoid valve command current value 77 for the proportional solenoid valve 72b based on a table that predetermines the relationship between the second control valve meter-in opening area target value 76 and the proportional solenoid valve command current value 77. In the table used in the solenoid proportional valve command current calculation section 81, the solenoid proportional valve command current value 77 is 0 (zero) when the second control valve meter-in opening area target value 76 is 0 (zero), and the solenoid proportional valve command current value 77 is set to increase as the second control valve meter-in opening area target value 76 increases.

Other configurations are the same as those of the first embodiment.

The same effects as those of the first embodiment can be obtained in the present embodiment configured as described above.

In addition, it is possible to suppress fluctuations in the pump capacity when the pressure of the arm cylinder 15 is reduced due to a change in the opening of the bypass flow control valve 32, and a change in the branch flow balance between the arm cylinder 15 and the second hydraulic actuator (cylinder 70).

In the present embodiment, the operation lever 73 is operated in the retraction direction of the cylinder 70, but the present invention can also be applied when the operation lever 73 is operated in the extension direction of the cylinder 70.

In addition, although the cylinder 70 has been exemplified as the second hydraulic actuator, the present invention is not limited to this, and the present invention can be applied even when another hydraulic actuator such as a hydraulic motor is used as the second hydraulic actuator.

In addition, although the case where the branch flow balance of pressure oil to a plurality of hydraulic actuators is maintained by correcting the meter-in opening of the control valve 71 has been described as an example, the meter-in opening of the control valve 27 may be corrected to maintain the branch flow balance.

Next, features of each of the above embodiments will be described.

(1) In the above embodiment, a variable displacement hydraulic pump 18 driven by a prime mover (for example, an engine 17), a hydraulic actuator (for example, an arm cylinder 15) driven by pressure oil discharged from the hydraulic pump, an operation lever 26 for outputting an operation signal for operating the hydraulic actuator, a control valve 27 for controlling supply and discharge of pressure oil to the hydraulic actuator, and a bypass oil for discharging pressure oil from a meter-out flow path through which pressure oil discharged from the hydraulic actuator flows to a hydraulic oil tank without passing through the control valve. a bypass flow control valve 32 for controlling the flow rate of pressure oil in the bypass oil passage; and a control device 19 for controlling the opening area of the bypass flow control valve in accordance with the load pressure of the hydraulic actuator and maintaining the tilt angle before changing the opening area even when the estimated value of the pump pressure after changing the opening area of the bypass flow control valve becomes a low value.

As a result, deterioration of operability when the load pressure of the hydraulic actuator suddenly drops can be suppressed.

(2) In the above-described embodiment, the working machine of (1) includes a center bypass oil passage 60 that connects the hydraulic oil tank 30 and the supply oil passage that supplies the pressure oil discharged from the hydraulic pump 18 to the control valve 27, and a center bypass flow control valve 61 that is provided in the center bypass oil passage and controls the flow rate of the pressure oil in the center bypass oil passage by changing the opening area. The opening area shall be controlled.

(3) In the above embodiment, the work machine of (1) includes a second hydraulic actuator (e.g., cylinder 70) which is different from the hydraulic actuator (e.g., arm cylinder 15) and is driven by pressure oil discharged from the hydraulic pump 18, a second control lever 73 for outputting an operation signal for operating the second hydraulic actuator, a second control valve 71 for controlling supply and discharge of pressure oil to the second hydraulic actuator, and the control device 19B. controls the hydraulic actuator or the control valve of the second hydraulic actuator according to the load pressure of the second hydraulic actuator.

<Appendix>
It should be noted that the present invention is not limited to the above-described embodiments, and includes various modifications and combinations within the scope of the invention. Moreover, the present invention is not limited to those having all the configurations described in the above embodiments, and includes those having some of the configurations omitted.

For example, in each of the above-described embodiments, the case where an electric control lever is used has been described as an example, but the present invention is not limited to this. For example, a hydraulic control lever and an operating pressure detector may be provided, and the pressure detected by the detector may be transmitted to the controller.

Further, in each of the above-described embodiments, the case of suppressing the deterioration of operability when the arm cylinder 15 is driven has been described, but the present invention is not limited to this, and can be applied to the case of driving a hydraulic actuator whose load changes depending on the weight or posture of the object to be supported, for example.

Further, each of the above configurations, functions, etc. may be realized by designing a part or all of them, for example, with an integrated circuit. Moreover, each of the above configurations, functions, etc. may be realized by software by a processor interpreting and executing a program for realizing each function.

DESCRIPTION OF SYMBOLS 1, 2... Track 1A... Working device 1B... Vehicle body 3... Traveling body 4... Revolving body 5... Boom 6... Arm 7... Bucket 8... Driver's cab 9... Machine room 10... Counterweight 11, 12... Travel hydraulic motor 13, 14... Boom cylinder 15... Arm cylinder 16... Bucket cylinder 17... Engine 18... Hydraulic pump 19, 19A, 19B... Control device 20... Pump regulator 21... Load calculation unit 22 Bypass flow control valve opening area calculation unit 23 Pump pressure estimated value calculation unit 24 Pump volume correction calculation unit 25, 25A, 25B Drive control unit 26 Operation lever 26a, 26b Operation signal 27, 27A Control valve 28 Pilot pump 29 Pilot relief valve 30 Hydraulic oil tank 31a, 31b, 31c Electromagnetic proportional valve 32 Bypass flow control valve 3 3... Bypass oil passage 34... Pressure sensor 35a, 35b... Pressure sensor 36... Arm cylinder load 37... Bypass flow control valve opening area target value 38... Pump pressure estimate value 39... Pump volume target value 40... Electromagnetic proportional valve command current value 41... Regulator command current value 42... Flow control valve opening area calculation unit 43... Flow control valve opening area 44... Arm cylinder bottom pressure estimate calculation unit 45... Arm cylinder bottom pressure estimate value 46... Arm cylinder bottom pressure estimate Rod pressure estimated value calculator 47 Arm cylinder bottom area 48 Arm cylinder rod area 49 Arm cylinder rod pressure estimated value 50 Pump pressure estimated value calculator 51 Pump capacity calculator 52 Pump capacity target value 53 Correction calculator 54 Pump capacity limit value calculator 55 Pump capacity limit value 56 Minimum value selector 58 Solenoid proportional valve command current calculator 59 Regulator command current calculator 60 Center bypass oil passage 61 Center bypass flow control valve 62 Proportional solenoid valve 63 Center bypass flow control valve opening area correction calculator 64 Electromagnetic proportional valve command current calculator 64 Center bypass flow control valve opening area target value 65 Electromagnetic proportional valve command current value 66 Center bypass flow control valve opening area calculator 67 Center bypass flow control valve opening area target value 68 Correction calculator 69 Electromagnetic proportional valve command current calculator 70 Cylinder 71 Second control valve 72a, 72b... Electromagnetic proportional valve 73... Second control lever 73a, 73b... Operation signal 74a, 74b... Pressure sensor 75... Second control valve correction calculation unit 76... Second control valve meter-in opening area target value 77... Electromagnetic proportional valve command current value 78... Second control valve meter-in opening area calculation unit 79... Second control valve meter-in opening area target value 80... Correction calculation unit 81... Electromagnetic proportional valve command current calculation unit , 100 Hydraulic excavator 200 Bypass flow control valve command pressure sensor

Claims (3)

a variable displacement hydraulic pump driven by a prime mover;
a hydraulic actuator driven by pressure oil discharged from the hydraulic pump;
an operation lever that outputs an operation signal for operating the hydraulic actuator;
a control valve that controls supply and discharge of pressure oil to and from the hydraulic actuator;
a bypass oil passage for discharging pressure oil from a meter-out passage through which pressure oil discharged from the hydraulic actuator flows to a hydraulic oil tank without passing through the control valve;
a bypass flow control valve that controls the flow rate of pressure oil in the bypass oil passage;
and a control device that increases the tilt angle of the hydraulic pump as the pump pressure of the hydraulic pump decreases,
The control device controls the opening area of the bypass flow control valve in accordance with the load pressure of the hydraulic actuator, and even when the estimated value of the pump pressure after changing the opening area of the bypass flow control valve becomes a low value, the control device controls to maintain the tilt angle before changing the opening area by reducing the torque limit value that determines the upper limit of the torque of the hydraulic pump according to the decrease in the estimated value of the pump pressure. The work machine according to claim 1,
a center bypass oil passage that connects a supply oil passage that supplies pressure oil discharged from the hydraulic pump to the control valve and a hydraulic oil tank;
a center bypass flow control valve provided in the center bypass oil passage for controlling the flow rate of pressure oil in the center bypass oil passage by changing an opening area;
The working machine, wherein the control device controls an opening area of the center bypass flow control valve according to the estimated value of the pump pressure. The working machine according to claim 1 or 2,
a second hydraulic actuator, which is different from the hydraulic actuator and is driven by pressure oil discharged from the hydraulic pump;
a second operating lever that outputs an operating signal for operating the second hydraulic actuator;
a second control valve that controls supply and discharge of pressure oil to and from the second hydraulic actuator;
The working machine, wherein the control device controls the control valve or the second control valve according to the load pressure of the second hydraulic actuator.

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