JP4222995B2 - Hydraulic cylinder drive device for construction machinery - Google Patents

Description

The present invention relates to dynamic device driving hydraulic cylinder of a construction machine, particularly to a hydraulic cylinder drive kinematic system for a construction machine equipped with a two-way pump motor driven by an electric motor-generator.

  2. Description of the Related Art Conventionally, a hydraulic circuit for a construction machine including a hydraulic cylinder that drives a working machine, a hydraulic pump that supplies pressure oil to the hydraulic cylinder, and a switching valve that switches a direction of the pressure oil from the hydraulic pump is widely known. . Also, a hydraulic motor connected to a regenerative generator (generator) is provided in an oil discharge circuit from the hydraulic cylinder, the turning drive source is a turning motor generator (electric motor generator), and the traveling drive source is a running motor. (Electric motor). Also known is a construction machine (hybrid excavator) configured to supply and charge power between a regenerative generator, a turning motor generator, a traveling motor, a generator motor connected to an engine, and a battery by an electric power controller. (For example, refer to Patent Document 1).

The hydraulic oil that drives the work implement collects the return oil from the meter-out side, and switches between opening and closing the hydraulic regeneration circuit that includes a pump motor that is driven to rotate by the collected return oil. There is also known a construction machine provided with a switching unit and a generator that generates electric power by a rotational force from a pump motor (see, for example, Patent Document 2).
JP 2001-207482 A JP 2003-329012 A

  The invention described in Patent Document 1 performs regenerative power generation by rotating a hydraulic motor with oil discharged from a hydraulic cylinder. In addition to a switching valve for supplying and discharging pressure oil to and from the hydraulic cylinder, the oil is discharged to the hydraulic motor. A valve for bypassing the oil is required, which complicates the configuration and increases the cost.

  The invention described in Patent Document 2 collects the return oil from the meter-out side of the hydraulic actuator, and performs regenerative power generation by rotating the pump motor with the recovered return oil. Similar to the invention described in Patent Document 1 In addition to the switching valve for supplying and discharging the pressure oil to and from the hydraulic cylinder, a valve for switching the discharged oil to the pump motor is required, which complicates the configuration and increases the cost.

  Therefore, there arises a technical problem to be solved in order to enable electric power regeneration without adding a special valve in addition to a switching valve for supplying and discharging pressure oil to and from the hydraulic cylinder. Aims to solve this problem.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 includes a hydraulic cylinder that drives the work machine, a hydraulic pump that supplies pressure oil to the hydraulic cylinder, and a hydraulic pump. In a hydraulic circuit of a construction machine having a switching valve for switching the direction of pressure oil of
The switching valve is connected to a bidirectional pump motor driven by an electric motor generator at an input port different from the hydraulic pump,
When the switching valve is operated, the bottom side of the hydraulic cylinder is always connected to the bidirectional pump motor, and the top side of the hydraulic cylinder is communicated to the tank port by an extension operation signal of the hydraulic cylinder, while the contraction operation signal of the hydraulic cylinder is connected to the hydraulic pump, furthermore, the hydraulic cylinder with the switching valve neutral position is a hydraulic cylinder drive operated device configuration the construction machine to be blocked. Furthermore, the invention according to claim 2
When the operation amount of the switching valve is small, the opening area of the switching valve is made minute, and the maximum opening area is rapidly increased as the operation amount of the switching valve increases.
When the hydraulic cylinder extending operation amount of the switching valve is very small, a control unit is provided that makes the discharge pressure of the bidirectional pump motor equal to or higher than the holding pressure of the hydraulic cylinder,
And a control unit for controlling the flow rate so that the discharge pressure of the bidirectional pump motor becomes a constant differential pressure based on the input pressure based on the holding pressure of the hydraulic cylinder or the differential pressure before and after the opening of the switching valve. Give it.
According to a third aspect of the present invention, a holding valve may be provided between the switching valve and the bottom side of the hydraulic cylinder. In this case, before the switching valve is opened by the contraction operation signal of the hydraulic cylinder. The holding valve is configured to open.
In the neutral position of the switching valve, the hydraulic cylinder driving device of the construction machine communicates the bidirectional pump motor and the tank.

  According to this configuration, when the switching valve is operated in the extending direction of the hydraulic cylinder, the top side of the hydraulic cylinder is connected to the tank port, and the bottom side of the hydraulic cylinder is connected to the bidirectional pump motor. If the electric motor generator connected to the drive shaft of the bi-directional pump motor is operated as an electric motor to drive the bi-directional pump motor, pressure oil is supplied to the bottom side of the hydraulic cylinder via the switching valve, and the hydraulic cylinder extends. . Since the extension of the hydraulic cylinder is performed by the single drive of the bidirectional pump motor, even in the combined operation with other hydraulic actuators, the independence of the actuators increases and energy is saved.

  On the other hand, when the switching valve is operated in the contraction direction of the hydraulic cylinder, the top side of the hydraulic cylinder is connected to the hydraulic pump, and the bottom side of the hydraulic cylinder is connected to the bidirectional pump motor. Pressure oil from the hydraulic pump is supplied to the top side of the hydraulic cylinder via the switching valve, and the hydraulic cylinder contracts. At this time, the bidirectional pump motor is driven using the holding pressure on the bottom side of the hydraulic cylinder as a hydraulic pressure source. The product of the pushing volume, the holding pressure, and the rotational speed of the bidirectional pump motor becomes power, and the electric motor generator connected to the drive shaft of the bidirectional pump motor is driven as a generator to regenerate electric power. The rotational speed is controlled so that the operating speed of the hydraulic cylinder changes smoothly according to the operation amount.

  According to this configuration, when the operation amount of the switching valve is small, the two-way pump motor is not controlled to rotate by the minute opening, and the hydraulic cylinder is controlled without being affected by the internal leak of the two-way pump motor. When the operation amount of the switching valve exceeds a certain value, the opening area is rapidly maximized, and the bidirectional pump motor is rotationally controlled according to the operation amount.

  According to this configuration, when the rotation of the bi-directional pump motor is small, the flow rate flows out to the tank as an internal drain, and therefore, the discharge pressure of the bi-directional pump motor may decrease and the holding pressure of the hydraulic cylinder may not be maintained. Therefore, when the operation amount of the switching valve is very small, by making the discharge pressure of the bidirectional pump motor equal to or higher than the holding pressure of the hydraulic cylinder, meter-in control can be performed and the hydraulic cylinder can be operated minutely.

  According to this configuration, the holding pressure of the hydraulic cylinder or the differential pressure before and after the opening of the switching valve is input to the pressure sensor or the differential pressure sensor, and the discharge pressure of the bidirectional pump motor is controlled based on this input pressure.

  According to this configuration, the pressure oil leaking from the switching valve is suppressed to the minimum by the holding valve. When a hydraulic cylinder contraction operation signal is received, the holding valve opens before the switching valve opens, and pressure oil discharged from the bottom side of the hydraulic cylinder is supplied to the bidirectional pump motor through the switching valve. Power regeneration is performed.

  According to this configuration, when the switching valve is in the neutral position, the bidirectional pump motor and the tank communicate with each other. Therefore, when the switching valve is returned to the neutral position due to an emergency stop or the like, the bidirectional pump motor is rotating. To prevent abnormal pressure rise.

According to a fourth aspect of the present invention, the switching valve is connected via a check valve that prevents a flow from the top side and the bottom side of the hydraulic cylinder by a contraction operation signal of the hydraulic cylinder, The construction machine according to claim 1, 2 or 3, wherein the tank port is connected via a throttle, and the bottom side of the hydraulic cylinder is connected to the hydraulic pump and the bidirectional pump motor by an extension operation signal of the hydraulic cylinder. providing driving of the hydraulic cylinder operated device.

  According to this configuration, when the switching valve is operated in the contraction direction of the hydraulic cylinder, the flow from the top side to the bottom side of the hydraulic cylinder is blocked by the check valve, and the pressure oil discharged from the bottom side is discharged from the bidirectional pump motor. In addition, power regeneration is performed and back pressure is applied by the throttle to perform meter-out control. On the other hand, when the switching valve is operated in the extending direction of the hydraulic cylinder, the pressure oil discharged from the hydraulic pump and the pressure oil discharged from the bi-directional pump motor merge and are supplied to the bottom side of the hydraulic cylinder. The operating speed can be increased.

According to a fifth aspect of the invention, to provide a hydraulic cylinder drive kinematic system for a construction machine according to claim 1, 2, 3 or 4 wherein the interposed transmission between said bidirectional pump motor and the electric motor-generator.

  According to this configuration, the electric motor generator can be reduced in size by driving the electric motor generator at high speed, and the two-way pump motor can be driven at an appropriate rotation by reducing the rotation of the electric motor generator with the transmission. .

According to a sixth aspect of the invention, the two-way pump motor to provide a hydraulic cylinder drive kinematic system for a construction machine according to claim 1, 2, 3, 4 or 5, wherein the variable capacity type.

  According to this configuration, when the hydraulic cylinder is contracted, the torque of the bidirectional pump motor is decreased to increase the rotational speed, so that the bidirectional pump motor is rotated at a high speed and efficient electric power regeneration is performed in the electric motor generator. Is called. Further, when the hydraulic cylinder is extended, the operating speed of the hydraulic cylinder is increased by increasing the discharge amount of the bidirectional pump motor.

The invention according to claim 7 is provided with a control unit for controlling the flow rate so that the flow rate control characteristic of the bidirectional pump motor is delayed with respect to the operation amount of the switching valve. or to provide a hydraulic cylinder drive kinematic system for a construction machine according 6.

  According to this configuration, when the switching valve is operated rapidly, the flow rate of the bidirectional pump motor increases rapidly following the operation at the start of operation, so there is no delay in the operating speed of the hydraulic cylinder, and thereafter the bidirectional pump Since a delay occurs in the increase in the flow rate of the motor, the operating speed of the hydraulic cylinder is smoothly accelerated and acceleration / deceleration with less shock is performed.

  According to the first aspect of the present invention, when the switching valve is operated in the extending direction of the hydraulic cylinder, it is possible to drive with less power loss and to save energy even in the combined operation with other hydraulic actuators. On the other hand, when the switching valve is operated in the contraction direction of the hydraulic cylinder, the potential energy can be converted into electric energy to regenerate electric power. Thus, power regeneration can be performed with a simple configuration without adding a special valve in addition to the switching valve as in the prior art.

This invention, when the operation amount of the directional control valve is small since both pump motor by the very small aperture is not controlled rotation, it is possible to control the hydraulic cylinder without the influence of internal leakage in both directions Ponpumo data. If the operation amount of the switching valve increases, the opening rapidly becomes maximum, so that the bidirectional pump motor is rotationally controlled according to the operation amount, and the response of the hydraulic cylinder to the operation amount can be improved.

This invention, when the hydraulic cylinder extension operation of the switching valve is minute, and the meter-in control by the discharge pressure of the two-way pump motor on the holding pressure of the hydraulic cylinder, and can be very small hydraulic cylinder extension operation Become.

This invention, and controls the discharge pressure of the two-way pump motor at the difference pressure input before and after the opening of the holding pressure or the switching換便hydraulic cylinder, so that the pressure differential across the opening of the switching valve is always constant It is possible to control, and accurate control with a minute flow rate is possible.

This invention is provided with the holding valve between the bottom side of the switching valve and the hydraulic cylinder, can pressure oil leaking from the switching valve to suppress such minimized. In addition, it acts as a load check valve when the hydraulic cylinder is extended, and it is possible to prevent the hydraulic cylinder from being pushed back in the contraction direction by a load.

This invention, since switching valve communicates the bidirectional pump motor and the tank when the neutral position, even when the delayed switching valve response bidirectional pump motor in an operation sudden stop is returned to the neutral position, two-way pump The flow rate when the motor is rotating can be secured to prevent the occurrence of abnormal high pressure. Further, at the time of hydraulic cylinder extension operation, the standby flow rate can be increased to improve the response.

  In the invention according to claim 4, pressure oil can be supplied to the bidirectional pump motor to perform power regeneration during the hydraulic cylinder contraction operation, and meter-out control is performed. It can be stabilized.

  According to the fifth aspect of the present invention, a transmission is interposed between the bidirectional pump motor and the electric motor generator, and the electric motor generator is operated at a high speed and decelerated by the transmission. And high efficiency can be achieved. Since the bidirectional pump motor, which is difficult to increase in speed, is driven with appropriate rotation by the transmission, the life of the bidirectional pump motor can be extended.

  According to the sixth aspect of the present invention, since the bidirectional pump motor is of a variable capacity type, the operating speed of the hydraulic cylinder can be increased during the hydraulic cylinder extension operation by increasing the capacity and increasing the rotational speed. Further, during the hydraulic cylinder contraction operation, efficient electric power regeneration can be performed by the electric motor generator.

The invention according to claim 7 controls the flow rate braking characteristics of the bidirectional pump motor so that there is a delay with respect to the operation amount. Therefore, when a sudden operation is performed, the responsiveness is agile at the beginning of movement, and thereafter acceleration is performed. By smoothing, acceleration / deceleration with less shock is possible, which can contribute to improvement in operability.

Hereinafter, the hydraulic cylinder drive braking system for a construction machine according to the present invention, will be described by way of preferred embodiments. The purpose of the switch valve is to use a separate input port from the hydraulic pump in order to enable power regeneration without adding a special valve in addition to the switch valve for supplying and discharging pressure oil to and from the hydraulic cylinder. A bidirectional pump motor driven by an electric motor generator is connected. When the switching valve is operated, the bottom side of the hydraulic cylinder is always connected to the bidirectional pump motor. On the other hand, this is realized by connecting to the hydraulic pump by a contraction operation signal of the hydraulic cylinder and further blocking the hydraulic cylinder at the neutral position of the switching valve.

  FIG. 1 shows a hybrid hydraulic excavator 10 as an example of a construction machine, and an upper swing body 13 is mounted on a lower traveling body 11 via a swing mechanism 12 so as to be rotatable. The upper swing body 13 is provided with a cab 14 on one front side thereof, and a boom 15 is attached to the front center portion so as to be able to be raised and lowered. Further, an arm 16 is attached to the tip of the boom 15 so as to be rotatable up and down, and a bucket 17 is attached to the tip of the arm 16.

  A boom cylinder 18, an arm cylinder 19, and a bucket cylinder 20 are provided as hydraulic actuators for driving attachments such as the boom 15, the arm 16, and the bucket 17, and a hydraulic pump 22 is provided by an engine 21 mounted on the upper swing body. To supply / discharge pressure oil to / from each hydraulic actuator.

  Furthermore, an electric motor generator 23 is connected to the drive shaft of the bidirectional pump motor 24, and the electric motor generator 23 is connected to a battery 26 via a control unit 25 having an inverter.

  FIG. 2 shows a drive circuit of a boom cylinder 18 as an example of a hydraulic cylinder electric device, and a hydraulic pump 22 that supplies pressure oil to the boom cylinder 18 and a three-position five-port for switching the direction of pressure oil from the hydraulic pump 22. The pilot type switching valve 27 is provided.

  The port on the inlet side (lower port in the figure) of the switching valve 27 is connected to the hydraulic pump 22 at the P1 port, the bidirectional pump motor 24 to the P2 port, and the Tn port communicates with the tank 28. is doing. A relief valve 29 is provided in the discharge oil passage of the hydraulic pump 22. On the other hand, the outlet side port (upper port in the figure) of the switching valve 27 connects the bottom side 18a of the boom cylinder 18 to the B port and connects the top side 18b of the boom cylinder 18 to the T port.

  As described above, the electric motor generator 23 is connected to the drive shaft of the bidirectional pump motor 24, and the electric motor generator 23 is connected to the battery 26 via the control unit 25 having an inverter.

  As shown in the figure, at the neutral position (A) of the switching valve 27, the B port on the bottom side 18a and the T port on the top side 18b of the boom cylinder 18 are blocked, and each of the P1, P2, and Tn ports is blocked. The port is also blocked.

  Here, when an extension operation signal is input to the extension side port 27a of the switching valve 27 by an operating means (not shown) such as an operation lever, the switching valve 27 is switched to the extension position (B), and P1 The port is blocked, and the P2 port and B port and the Tn port and T port communicate with each other. That is, the bottom side 18 a of the boom cylinder 18 is connected to the bidirectional pump motor 24, and the top side 18 b of the boom cylinder 18 is connected to the tank 28.

  In this case, the electric power stored in the battery 26 is supplied to the electric motor generator 23 under the control of the control unit 25, and the electric motor generator 23 is operated as an electric motor to drive the bidirectional pump motor 24 in one direction. For example, the pressure oil discharged from the bi-directional pump motor 24 is supplied to the bottom side 18a of the boom cylinder 18 through the extension position (b) of the switching valve 27, and the pressure oil on the top side 18b of the boom cylinder 18 is supplied to the tank. Returning to 28, the boom cylinder 18 extends. Since the extension of the boom cylinder 18 is performed by the single drive of the bidirectional pump motor 24, the boom cylinder 18 can be driven with little power loss, and even in combined operation with other hydraulic actuators, the independence of the actuators increases and energy saving is achieved.

  On the other hand, when a contraction operation signal is input to the contraction side port 27b of the switching valve 27 by the operating means, the switching valve 27 is switched to the contracted position (c), the Tn port is blocked, the P1 port and the T port, P2 port and B port communicate with each other. That is, the bottom side 18 a of the boom cylinder 18 is connected to the bidirectional pump motor 24, and the top side 18 b of the boom cylinder 18 is connected to the hydraulic pump 22.

  In that case, the pressure oil discharged from the hydraulic pump 22 is supplied to the top side 18b of the boom cylinder 18 via the contracted position (c) of the switching valve 27 and the holding pressure on the bottom side 18a of the boom cylinder 18 is maintained. As a hydraulic power source, the bidirectional pump motor 24 rotates in the other direction opposite to the above. The product of the pushing volume, the holding pressure, and the rotational speed of the bidirectional pump motor 24 becomes power, and the electric motor generator 23 connected to the drive shaft of the bidirectional pump motor 24 is driven as a generator and regenerated to electric power. And stored in the battery 26. The rotation speed of the boom cylinder 18 is controlled so as to change smoothly according to the operation amount of the operation means.

  As described above, the bottom side 18a of the boom cylinder 18 is always connected to the bidirectional pump motor 24 regardless of whether the switching valve 27 is extended or contracted. On the other hand, the top side 18b of the boom cylinder 18 communicates with the tank 28 by an extension operation signal and is connected to the hydraulic pump 22 by a contraction operation signal.

  As shown in FIG. 3A, the switching valve 27 has a small opening area in a region where the operation amount is very small, and is formed so that the opening area gradually increases as the operation amount increases. Accordingly, the rotation of the bidirectional pump motor 24 is not controlled, and the boom cylinder 18 can be controlled without being affected by the internal leakage of the bidirectional pump motor 24. When the operation amount of the switching valve 27 exceeds a certain value, the opening area is rapidly expanded to the maximum opening area, so that the bidirectional pump motor 24 is rotationally controlled according to the operation amount. Therefore, the response of the boom cylinder 18 to the operation amount can be improved.

  Further, as shown in FIG. 3B, since the switching valve 27 has a small flow rate in a region where the operation amount is small, the operation speed of the boom cylinder 18 is slowly increased. When the operation amount of the switching valve 27 exceeds a certain value, the opening area is rapidly expanded, and the flow rate is rapidly increased, so that the operating speed of the boom cylinder 18 is rapidly increased.

  Here, when the operation amount is small when the switching valve 27 is extended, the control unit 25 controls the discharge pressure of the bidirectional pump motor 24 to be equal to or higher than the holding pressure of the boom cylinder 18. This is because when the rotation of the bi-directional pump motor 24 is small, the flow rate flows out into the tank 28 as internal drain, and therefore, the discharge pressure of the bi-directional pump motor 24 decreases and the holding pressure of the boom cylinder 18 cannot be maintained. is there. In order to prevent this, when the extension operation amount of the switching valve 18 is very small, the discharge pressure of the two-way pump motor 24 is set to be equal to or higher than the holding pressure of the boom cylinder 18 so that meter-in control is performed. The minute operation is possible.

  FIG. 4 shows a modified example. The difference from FIG. 2 is that a pressure sensor 30 is provided between the bottom side 18a of the boom cylinder 18 and the switching valve 27, and a holding valve 31 is interposed. The holding valve 31 is configured to prevent the flow from the bottom side 18 a of the boom cylinder 18 to the switching valve 27. Further, at the neutral position (A) of the switching valve 27, the P2 port and the Tn port are communicated, and the bidirectional pump motor and the tank are communicated.

  The pressure sensor 30 detects the holding pressure of the boom cylinder 18, and the detected holding pressure is input to the control unit 25. The control unit 25 controls the discharge pressure of the bidirectional pump motor 24 based on this input pressure. Therefore, it is possible to control so that the pressure difference before and after opening of the switching valve 27 is always constant, and it is possible to perform accurate control particularly at a minute flow rate.

  Alternatively, a differential pressure sensor (not shown) for detecting the differential pressure before and after opening of the switching valve 27 is provided, and the differential pressure detected by the differential pressure sensor is input to the control unit 25, and the control unit 25 uses this input pressure as the input pressure. The discharge pressure of the bidirectional pump motor 24 may be controlled based on the above. In such a configuration, similarly to the above, it is possible to control so that the pressure difference before and after opening of the switching valve 27 is always constant, and it is possible to perform accurate control particularly at a minute flow rate.

  Here, when an extension operation signal is input to the extension side port 27a of the switching valve 27 by the operating means, the switching valve 27 is switched to the extension position (B), and the bottom side 18a of the boom cylinder 18 is connected to the bidirectional pump motor. 24, the top side 18 b of the boom cylinder 18 is connected to the tank 28. At that time, as described above, the bidirectional pump motor 24 is driven by the electric motor generator 23, and the pressure oil is led out from the P2 port to the B port via the extension position (b) of the switching valve 27. The oil opens the holding valve 31 and is supplied to the bottom side 18a of the boom cylinder 18, and the pressure oil on the top side 18b of the boom cylinder 18 is led out from the T port to the Tn port and returns to the tank 28. Expands.

  On the other hand, when the contracting operation signal is input to the contraction side port 27b of the switching valve 27 by the operating means, the switching valve 27 is switched to the contracted position (C), and the bottom side 18a of the boom cylinder 18 is connected to the bidirectional pump motor 24. The top side 18 b of the boom cylinder 18 is connected to the hydraulic pump 22. At that time, as described above, the pressure oil of the hydraulic pump 22 is supplied to the top side 18b of the boom cylinder 18 via the contracted position (c) of the switching valve 27, and the holding valve 31 is received by a contraction operation signal. Is opened, and the flow from the bottom side 18a of the boom cylinder 18 to the switching valve 27 is allowed. Then, the bidirectional pump motor 24 is rotated by the pressure oil from the bottom side 18 a, the electric motor generator 23 is driven as a generator, regenerated into electric power, and stored in the battery 26.

  As described above, since the holding valve 31 is provided between the switching valve 27 and the bottom side 18a of the boom cylinder 18, the pressure oil leaking from the switching valve 27 can be suppressed to a minimum. When the boom cylinder 18 is extended, it also functions as a load check valve, and the boom cylinder 18 can be prevented from being pushed back in the contracting direction by a load. When the boom cylinder 18 is retracted, the holding valve 31 is opened before the switching valve 27 is opened, and the pressure oil discharged from the bottom side 18a of the boom cylinder 18 passes through the holding valve 31 and is supplied to the bidirectional pump motor 24. Then, power regeneration is performed.

  Further, when the switching valve 27 is in the neutral position (A), the bidirectional pump motor 24 and the tank 28 are communicated with each other, so that the response of the bidirectional pump motor 24 is delayed due to an emergency stop or the like, and the switching valve 27 returns to the neutral position. Even in this case, the flow rate when the bidirectional pump motor 24 is rotating can be secured to prevent the occurrence of abnormal high pressure. Further, at the time of the extension operation of the boom cylinder 18, the standby flow rate can be increased to improve the responsiveness.

  FIG. 5 shows another modification. The difference from FIG. 2 is that the P1 port and the P2 port communicate with each other and are connected to the B port at the extended position (B) of the switching valve. In the contracted position (c) of the switching valve, the B port and the T port are connected via a check valve 32 that blocks the flow from the T port, and the B port and the Tn port are connected via a throttle 33. Yes. A transmission 34 is interposed between the electric motor generator 23 and the bidirectional pump motor 24.

  Here, when an extension operation signal is input to the extension side port 27a of the switching valve 27 by the operating means, the switching valve 27 is switched to the extension position (B), and the bottom side 18a of the boom cylinder 18 is connected to the hydraulic pump 22. The top side 18b of the boom cylinder 18 is connected to the tank 28.

  In that case, the pressure oil discharged from the hydraulic pump 22 and the pressure oil discharged from the bidirectional pump motor 24 merge and are supplied to the bottom side 18a of the boom cylinder 18, and the pressure oil on the top side 18b of the boom cylinder 18 is also supplied. The pressure oil is returned to the tank 28 and the boom cylinder 18 is extended. Since pressure oil is supplied to both the bottom side 18a of the boom cylinder 18 from both the hydraulic pump 22 and the bidirectional pump motor 24, the flow rate can be increased and the operating speed of the boom cylinder 18 can be increased.

  On the other hand, when the contracting operation signal is input to the contraction side port 27b of the switching valve 27 by the operating means, the switching valve 27 is switched to the contracted position (C), and the bottom side 18a of the boom cylinder 18 is connected to the bidirectional pump motor 24. And the bottom side 18 a of the boom cylinder 18 communicates with the tank 28 through the throttle 33. The top side 18 b of the boom cylinder 18 is connected to the hydraulic pump 22.

  At that time, the pressure oil of the hydraulic pump 22 is supplied to the top side 18 b of the boom cylinder 18 through the contracted position (c) of the switching valve 27. At this time, the check valve 32 prevents the boom cylinder 18 from flowing from the top side 18b to the bottom side 18a. The pressure oil on the bottom side 18 a of the boom cylinder 18 is supplied to the bidirectional pump motor 24 and is returned to the tank 28 through the throttle 33. Accordingly, the bidirectional pump motor 24 rotates and the electric motor generator 23 is driven as a generator, and is regenerated into electric power and stored in the battery 26. Further, since the back pressure is applied by the throttle 33 and meter-out control is performed, the operation of the boom cylinder 18 can be stabilized against load fluctuations.

  Here, since the transmission 34 is interposed between the electric motor generator 23 and the bidirectional pump motor 24, the electric motor generator 23 is operated at a high speed and decelerated by the transmission 34. The motor generator 23 can be reduced in size and efficiency. In addition, since the bidirectional pump motor 24, which is difficult to increase in speed, is driven at an appropriate rotation by the transmission 34, the life of the bidirectional pump motor 24 can be extended.

  Since the bidirectional pump motor is a variable displacement type, the discharge amount and torque can be changed, and when the holding pressure of the boom cylinder 18 is high, the discharge amount is decreased to prevent overtorque of the electric motor generator. When the holding pressure of the boom cylinder 18 is low, the discharge amount increases and the cylinder speed can be increased. On the other hand, in the fixed capacity type, it is necessary to set the discharge amount so that the electric motor generator does not become overtorque when the holding pressure of the boom cylinder 18 is maximum, and the speed of the cylinder is increased by increasing the rotational speed of the bidirectional pump motor. There are restrictions.

  FIG. 6 shows the relationship between the operation amount of the switching valve 27 and the cylinder operating speed of the boom cylinder 18, and the flow rate control dynamic characteristic of the bidirectional pump motor 24 is delayed with respect to the operation amount of the switching valve 27 indicated by the solid line. Therefore, the increase in the operating speed of the boom cylinder 18 indicated by a dotted line is delayed.

  Therefore, when the switching valve 27 is operated rapidly, the flow rate of the bidirectional pump motor 24 increases rapidly following the operation at the start of the operation, so that there is no delay in the operating speed of the boom cylinder 18, and thereafter Since a delay occurs in the increase in the flow rate of the pump motor 24, the operating speed of the boom cylinder 18 is smoothly accelerated and acceleration / deceleration with less shock is performed. In this way, control is performed so that there is a delay with respect to the operation amount. It becomes possible and can contribute to improvement in operability.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

1 is a side view of a hydraulic excavator to which the present invention is applied. The drive circuit diagram of the boom cylinder as an example which concerns on this invention. (A) The graph which shows the relationship between the operation amount of the switching valve of FIG. 2, and opening area, (b) The graph which shows the relationship between the operation amount of the switching valve of FIG. 2, and the operating speed of a boom cylinder. The drive circuit figure of the boom cylinder as a modification concerning the present invention. The drive circuit diagram of the boom cylinder as another modification concerning the present invention. The figure which shows the temporal relationship of the operation amount of the switching valve which concerns on this invention, and cylinder operating speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hydraulic excavator 18 Boom cylinder 22 Hydraulic pump 23 Electric motor generator 24 Two-way pump motor 25 Control part 26 Battery 27 Switching valve 28 Tank 30 Pressure sensor 31 Holding valve 32 Check valve 33 Restriction 34 Transmission

Claims (7)

In a hydraulic circuit of a construction machine including a hydraulic cylinder that drives a work machine, a hydraulic pump that supplies pressure oil to the hydraulic cylinder, and a switching valve that switches a direction of the pressure oil from the hydraulic pump,
The switching valve is connected to a bidirectional pump motor driven by an electric motor generator at an input port different from the hydraulic pump,
When the switching valve is operated, the bottom side of the hydraulic cylinder is always connected to the bidirectional pump motor, and the top side of the hydraulic cylinder is communicated to the tank port by an extension operation signal of the hydraulic cylinder, while the contraction operation signal of the hydraulic cylinder A hydraulic cylinder drive device for a construction machine, which is connected to a hydraulic pump and further configured to block the hydraulic cylinder at the neutral position of the switching valve. When the operation amount of the switching valve is small, the opening area of the switching valve is made minute, and the maximum opening area is rapidly increased as the operation amount of the switching valve increases .
When the hydraulic cylinder extending operation amount of the switching valve is very small, a control unit is provided that makes the discharge pressure of the bidirectional pump motor equal to or higher than the holding pressure of the hydraulic cylinder,
And a control unit for controlling the flow rate so that the discharge pressure of the bidirectional pump motor becomes a constant differential pressure based on the input pressure based on the holding pressure of the hydraulic cylinder or the differential pressure before and after the opening of the switching valve. The hydraulic cylinder drive device of Claim 1 provided. A holding valve is provided between the switching valve and the bottom side of the hydraulic cylinder, and the holding valve is opened before the switching valve is opened by a contraction operation signal of the hydraulic cylinder.
3. The hydraulic cylinder driving device for a construction machine according to claim 1, wherein the bidirectional pump motor and the tank are communicated with each other at a neutral position of the switching valve. The switching valve is connected via a check valve that blocks the flow from the top side and bottom side of the hydraulic cylinder with a contraction operation signal of the hydraulic cylinder, and the bottom side of the hydraulic cylinder and tank port are connected via a throttle. is, on the other hand, the hydraulic cylinders of the extension operation signal by the hydraulic cylinder bottom side and the hydraulic pump as well as a construction machine of the hydraulic cylinder drive braking system according to claim 1, wherein the configuration so that connecting a bidirectional pump motor. Construction machine hydraulic cylinder drive braking system according to claim 1, 2, 3 or 4 wherein the interposed transmission between said bidirectional pump motor and the electric motor-generator. Said bidirectional pump motor construction machine hydraulic cylinder drive braking system according to claim 1, 2, 3, 4 or 5, wherein the variable capacity type. The hydraulic pressure of the construction machine according to claim 1, 2, 3, 4, 5 or 6, further comprising a control unit for controlling a flow rate so that a flow rate control characteristic of the bidirectional pump motor is delayed with respect to an operation amount of the switching valve. cylinder drive operated device.

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