JP4114609B2 - Construction machinery - Google Patents

Description

  The present invention relates to a construction machine such as a hydraulic excavator.

  In a hydraulic excavator equipped with a swivel of an upper swinging body on a lower traveling body, the inertia of the upper swinging body is large if the turning lever is suddenly returned to the neutral position and stopped. In some cases, the flow rate of the pressure oil supplied from the control valve meter-in is insufficient for the required flow rate required by the actuator, and cavitation occurs in the meter-in piping.

  Therefore, a back pressure check valve is provided in the return pipe that returns the pressure oil discharged from the control valve to the tank to generate back pressure in the return pipe, and the return pipe and the swivel meter-in pipe are connected with the make-up pipe. Conventionally, at the time of turning deceleration, pressure oil is supplied to the turning meter-in pipe by using the back pressure generated in the return pipe as a pressure source, thereby preventing cavitation.

  The cavitation occurs not only when the turning is stopped, but also when the engine is set to low idle and the arm is pulled while a load is applied, and the arm is pulled while the bucket is in contact with the ground. In the case of performing, cavitation may occur on the head side of the boom cylinder by applying a tensile load to the boom cylinder when the arm moves to the near side from the vertical posture.

  However, in the conventional cavitation prevention circuit described above, back pressure is always generated in the return pipe by the back pressure check valve even when make-up is not required. Therefore, back pressure is raised by operations other than turning stop and arm pulling. Even if it is not necessary, there is a problem that the pressure loss due to the back pressure check valve always occurs and the energy efficiency deteriorates.

Therefore, as a means for preventing cavitation and reducing energy loss in the back pressure circuit, a rotation speed sensor for detecting the turning speed and a variable throttle valve for the return pipe are provided, and the rotation detected by the rotation speed sensor is provided. There is known a hydraulic control circuit in which a controller controls the opening of the variable throttle valve according to the number (see, for example, Patent Document 1).
Japanese Patent No. 3113500 (Page (4), Fig. 1)

  However, in the hydraulic control circuit described above, the opening of the variable throttle valve is adjusted based on the rotational speed measured by a rotational speed sensor, specifically, a potentiometer, so that a malfunction may occur if the turning speed varies. There is. In addition, there is also a problem that the accuracy of deceleration determination is low due to the influence of noise in the calculation process for obtaining the turning speed by differentiating the rotation speed measured by the rotation speed sensor.

  Further, as described above, cavitation occurs not only in the turning operation by the turning motor but also in the arm pulling operation by the hydraulic cylinder, but the conventional cavitation prevention circuit cannot prevent the cavitation generated at the time of arm pulling.

The present invention has been made in consideration of the problems in the conventional cavitation prevention circuit as described above, and can prevent cavitation with respect to the operation of a specific hydraulic actuator that requires make-up with a simple circuit configuration. Therefore, the present invention provides a construction machine that eliminates the pressure loss caused by the back pressure check valve in an operation other than a specific hydraulic actuator and that can effectively generate the back pressure.

The present invention includes a plurality of hydraulic actuators, operating means for operating each hydraulic actuator, a return oil path for returning return oil from each hydraulic actuator to a tank, and part of the return oil provided in the return oil path A flow rate control valve for adjusting the back pressure in the return oil path to control the regenerative flow rate re-supplied to the hydraulic actuator by the regeneration line, Control means for controlling the control valve, a back pressure valve is provided in the return oil passage, and a bypass line that bypasses the back pressure valve is provided, and the flow rate control valve is provided in the bypass line, and the flow rate The control valve is switched between a communication position that bypasses the back pressure valve and communicates with the tank, and a shut-off position that generates back pressure by the back pressure valve. Configured ability, the control means, while the switching to the blocking position during the flow control valve operating means for operating the particular hydraulic actuator is operated, even after cessation of the operation is the specific actuator The construction machine is configured to switch the flow control valve to the communication position after stopping .

The present invention also provides a plurality of hydraulic actuators, operating means for operating each hydraulic actuator, a return oil path for returning the return oil from each hydraulic actuator to the tank, and a return oil path provided in the return oil path. A regeneration line for resupplying a part to a specific hydraulic actuator, and a flow rate control valve for adjusting the back pressure in the return oil path in order to control the regeneration flow rate re-supplied to the hydraulic actuator by the regeneration line; Control means for controlling the flow rate control valve, a back pressure valve is provided in the return oil passage, and a bypass line that bypasses the back pressure valve is provided, and the flow rate control valve is provided in the bypass line, The flow rate control valve is configured to decrease the regeneration flow rate by increasing the opening thereof, and the control means includes the specific hydraulic actuator. During the period when the operating means for operating the eta is operated, the greater the operation amount of the operating means, the more the operation is performed in the direction of decreasing the opening degree of the flow control valve, and after the operation is stopped, The construction machine is configured to operate in a direction to increase the opening degree of the flow control valve after the actuator is stopped.

According to the present invention, when a specific hydraulic actuator is operated, back pressure is generated in the return oil path from the hydraulic actuator, and pressure oil is supplied to the drive side of the specific hydraulic actuator through the regeneration line to prevent cavitation. Is done. Further, since the pressure oil is supplied through the regeneration line until the specific hydraulic actuator is stopped, cavitation can be effectively prevented. Further, when a specific hydraulic actuator is not operated, control for increasing the regeneration flow rate is not performed in a state where the opening degree of the flow rate control valve is increased, and occurrence of pressure loss in the return oil passage is eliminated.

In the present invention , the flow rate control valve is provided in the return oil passage , and the control means is configured to decrease the regeneration flow rate by increasing the opening degree of the flow rate control valve.

In the present invention , a back pressure valve and a bypass line that bypasses the back pressure valve are provided in the return oil passage , and a flow rate control valve is provided in the bypass line.

  In the present invention, a pressure sensor for detecting a pilot pressure derived from the remote control valve as the operation means is provided, and the control means is configured to control the flow rate control valve in response to the pilot pressure detected by the pressure sensor. be able to.

  In the present invention, a hydraulic pilot valve is provided as the flow rate control valve, and a hydraulic pilot type control valve that controls the operation of a specific hydraulic actuator by operating a remote control valve as an operation means is provided. A control means can be configured by branching a flow control pilot line from the line and providing a slow return valve in the flow control pilot line.

  In this configuration, a controller is not required, and the regeneration flow rate can be controlled using a pilot signal for controlling the control valve, so that the circuit can be simplified.

  A construction machine according to the present invention includes a lower traveling body, an upper swing body mounted on the lower traveling body, and a front attachment with a boom provided on the upper swing body, as the specific hydraulic actuator. A construction machine having at least one of a turning motor for turning the upper turning body and a boom cylinder for raising and lowering the boom of the front attachment is provided with the above-described configuration.

  As is apparent from the above description, according to the present invention, when a specific hydraulic actuator is operated, back pressure is generated in the return oil path from the hydraulic actuator, and the specific hydraulic actuator is driven through the regeneration line. Pressure oil is supplied to the side to prevent cavitation. At this time, since the pressure oil is supplied through the regeneration line until the specific hydraulic actuator stops, cavitation can be effectively prevented.

Further, when a specific hydraulic actuator is not operated, control for reducing the opening of the flow control valve to increase the regeneration flow rate is not performed, and the occurrence of pressure loss in the return oil passage is eliminated.

  Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 shows a hydraulic control circuit of a hydraulic excavator as an example of the construction machine of the present invention.

  In the figure, 1 is an arm cylinder for driving an arm constituting a front attachment of a hydraulic excavator, 2 is a boom cylinder as a specific hydraulic actuator for raising and lowering the boom, and 3 is for driving a bucket. It is a bucket cylinder for.

  Reference numeral 4 denotes a turning hydraulic motor (hereinafter referred to as a turning motor) as a specific hydraulic actuator for turning the upper turning body. The cylinders 1 to 3 and the swing motor 4 are collectively referred to as a hydraulic actuator.

  Reference numerals 5 and 6 denote a first hydraulic pump and a second hydraulic pump that supply pressure oil to the hydraulic actuator.

  Pressure oil discharged from the first hydraulic pump 5 is controlled in direction and flow rate by control valves 7 and 8 and supplied to the arm driving cylinder 1 and the swing motor 4, respectively.

  The pressure oil discharged from the second hydraulic pump 6 is supplied to the boom cylinder 2 and the bucket cylinder 3 with the direction and flow rate controlled by the control valves 9 and 10, respectively.

  Reference numerals 11 to 15 denote return lines (return oil passages) that return the hydraulic oil discharged from the hydraulic actuators to the tank 16.

  Reference numeral 17 denotes an oil cooler for cooling the hydraulic oil flowing through the return line 15. Reference numeral 18 denotes a first make-up line (regeneration line) that prevents cavitation by supplying a part of the return oil of the return line 15 when the pressure of the piping 19 for the turning motor 4 is reduced. It has become.

  A second make-up line (regeneration line) 20 prevents cavitation by supplying a part of the return oil from the return line 15 when the pressure of the piping 21 for the boom cylinder 2 drops. ing.

  22 is a back pressure check valve provided downstream of the makeup line joining point 15a in the return line 15, and generates back pressure in the return line 15 to supply return oil through the makeup lines 18 and 20. It is supposed to let you.

  Reference numeral 23 denotes a bypass check valve provided in parallel with the back pressure check valve 22, and when the flow rate of the back pressure check valve 22 increases, the return oil is bypassed.

  An electromagnetic switching valve 24 has a communication position a and a blocking position b that bypass the back pressure check valve 22 and communicate with the tank 16, and the switching operation is controlled by a controller (control means) 25 described later. It is like that. The electromagnetic switching valve 24 functions as a flow control valve.

  Reference numeral 26 denotes a turning operation lever, and 27 denotes an arm operation lever.

  The turning operation lever 26 is connected to a turning operation remote control valve 28, and the arm operation lever 27 is connected to an arm operation remote control valve 29 so as to generate a pilot pressure according to the amount of operation of the operation lever. It has become. The operation levers 26 and 27 and the remote control valves 28 and 29 function as operation means.

  The pilot line 30 derived from the turning operation remote control valve 28 is connected to the pilot port of the control valve 8, and the pilot line 31 derived from the arm operation remote control valve 29 is connected to the pilot port of the control valve 7.

  32 is a pressure sensor for detecting a pilot pressure (operation pressure) for turning operation, and 33 is a pressure sensor for detecting a pilot pressure (operation pressure) for arm operation. Each pressure sensor 32, 33 functions as an operation detection means.

  The pilot pressure signals S1 and S2 detected and output by the pressure sensors 32 and 33 are given to the controller 25.

  Next, the control operation of the controller 25 will be described.

(a) Turning operation When turning operation lever 26 is inserted, pilot pressure P1 is generated by turning operation remote control valve 28, and control valve 8 is controlled by this pilot pressure P1, and hydraulic fluid whose flow rate and direction are controlled is supplied. As a result, the turning motor 4 is driven.

  At this time, the pilot pressure is detected by the pressure sensor 32, and the detected pilot pressure signal S 1 is given to the controller 25.

  Upon receiving the pilot pressure signal S1, the controller 25 switches the electromagnetic switching valve 24 to the closed position b.

  The hydraulic oil discharged from the swing motor 4 also flows through the back pressure check valve 22 and through the bypass check valve 23 when the flow rate is large. As a result, the back oil is returned to the return line 15 by the resistance of the back pressure check valves 22 and 23. Pressure (return back pressure) is generated.

  In this state, when the pressure in the meter-in piping of the swing motor 4 becomes equal to or lower than the return back pressure, a makeup flow is generated in the swing makeup line 18 and is supplied to the meter-in side of the swing motor 4. Prevent cavitation from occurring.

  FIG. 2 shows a case where sudden deceleration is performed in the turning operation.

  The vertical axis of FIG. 6A shows the operation amount (pilot pressure signal S 1) of the turning operation lever 26, (b) shows the turning speed of the turning motor 4, and (c) shows the switching commanded to the electromagnetic switching valve 24. A valve signal is shown, (d) shows the makeup flow rate which flows through the makeup line 18, and the horizontal axis of (a)-(d) shows time, respectively.

  In FIG. 2A, when the turning lever 26 being operated is rapidly returned to neutral from time T2 to T3, the rotation of the turning motor 4 does not stop immediately because the inertia of the upper turning body is large. As shown in (b), the turning operation is performed until time T4.

  In such a case, in this embodiment, even when the pilot pressure signal S1 from the turning operation remote control valve 28 is reduced to zero, as shown in FIG. The valve signal is still output as a close signal, and the electromagnetic switching valve 24 opens at the timing T5 after the turning speed becomes zero. That is, the electromagnetic switching valve 24 switched to the shut-off position b is not immediately opened but switched to the communication position a with a delay.

  As a result, while the swing motor 4 is rotating, even if the swing operation lever 26 is returned to the neutral position, the electromagnetic switching valve 24 is closed for a certain period, and the swing motor 4 is rotating by inertia T4. During this period, make-up is always performed and cavitation can be prevented.

(b) Arm pulling operation Even when the arm operation lever 27 is inserted, the pilot pressure P2 generated by the arm operation remote control valve 29 is detected by the pilot pressure sensor 33 and is supplied to the controller 25 as a pilot pressure signal S2.

  Also in this case, the controller 25 switches the electromagnetic switching valve 24 to the b position to be in the closed state, and generates a back pressure in the return line 15. In this state, when the pressure of the head side piping 21 of the boom cylinder 2 decreases and becomes equal to or less than the return back pressure, a makeup flow rate is generated in the boom makeup line 20, thereby causing cavitation in the head side piping of the boom cylinder 2. Occurrence is prevented.

  When performing an arm pulling operation in excavation work, for example, when pulling the arm while contacting the bucket with the ground, if the arm moves to the near side from the vertical position, a load in the lifting direction acts on the boom, and the boom cylinder 2 is applied. A tensile load will act.

  In the conventional hydraulic control circuit, cavitation occurs on the head side of the boom cylinder 2 in this state, but in this embodiment, when the pilot pressure sensor 33 detects that the arm pulling operation has been performed, the electromagnetic switching valve Since the oil passage (communication position a) communicating with the tank 16 is closed by switching 24 to the b position, the occurrence of cavitation can be prevented.

  Also in this arm pulling operation, similarly to the turning operation described above, when the arm pulling operation is suddenly stopped, the controller 25 does not immediately open the electromagnetic switching valve 24 switched to the shut-off position b, and the communication position is delayed. Since switching to a, cavitation occurring on the head side of the boom cylinder 2 can be reliably prevented.

(c) Operations other than turning and arm pulling operations Further, when the turning operation lever 26 or the arm operation lever 27 is not engaged, neither the pilot pressure P1 nor P2 is generated, and the controller 25 brings the switching valve 24 into the communication position. Let it be in the open state as a.

  As a result, most of the return oil discharged from the hydraulic actuator flows through the communication position a of the switching valve 24 having a lower resistance than the back pressure check valve 22. This eliminates the pressure loss caused by the back pressure check valve 22 when make-up is not required, and solves the problem that the energy efficiency deteriorates as in the conventional circuit in which the back pressure is always generated by the back pressure check valve. be able to.

  In the first embodiment, the example in which the normal position of the electromagnetic switching valve 24 is in the communication position a and the switching control is performed to the cutoff position b in response to a signal from the controller 25 has been described. The normal position may be the blocking position b. In this case, the position control of the electromagnetic switching valve 24 by the controller 25 can perform the same control as in the first embodiment described above, for example, a signal connecting the controller 25 and the electromagnetic switching valve 24. Even if control of the electromagnetic switching valve 24 becomes impossible due to wire breakage or the like, the electromagnetic switching valve 24 is fixed at the cutoff position b, so that the back pressure check valve 22 and the bypass check valve 23 can function. Until the repair, it is possible to continue the work while preventing at least the occurrence of cavitation, and it is not necessary to stop the machine.

  FIG. 3 shows a second embodiment of the present invention.

  In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 3, 40 is a flow control pilot line branched from the turning pilot line 30, 41 is a flow control pilot line branched from the arm operation pilot line 31, and 42 is a shuttle for selecting the high pressure side of the flow control pilot lines 40 and 41. It is a valve.

  A hydraulic signal line 43 communicates the shuttle valve 42 and the hydraulic pilot type switching valve 44, and 45 is a slow return valve provided in the hydraulic signal line 43.

  Next, the operation of the hydraulic control device of the second embodiment will be described.

  When the turning operation lever 26 or the arm operation lever 27 is inserted, a pilot pressure is generated by the turning remote control valve 28 or the arm remote control valve 29, and the high pressure side of the pilot pressure is selected by the shuttle valve 42, and one flow rate is selected. Guided to the control pilot line 43. As a result, the switching valve 44 is switched to the shut-off position b, and the return oil discharged from the hydraulic actuator flows through the back pressure check valve 22 or both the back pressure check valve 22 and the bypass check valve 23, thereby Back pressure is generated in the return line 15 by the resistance of the back pressure check valves 22 and 23.

  In this state, when the pressure in the meter-in piping of the swing motor 4 becomes equal to or lower than the return back pressure, a make-up flow rate is generated in the swing make-up line 18 and supplied to the meter-in side of the swing motor 4, and cavitation occurs in the meter-in piping. To prevent it.

  Even when the arm operating lever 27 is inserted to perform the arm pulling operation, back pressure is generated in the return line 15 by the same operation as described above. As a result, when the pressure of the head side piping 21 of the boom cylinder 2 is reduced to be equal to or lower than the return back pressure, a makeup flow rate is generated in the boom makeup line 20 and cavitation occurs in the boom cylinder head side piping. Prevent it from occurring.

On the other hand, when the turning operation lever 26 or the arm operation lever 27 is returned to the neutral position, the pilot pressure generated by the turning remote control valve 28 and the arm remote control valve 29 is released, and the switching valve 44 is switched to the communication position a. Change.

  When the switching valve 44 switches to the communication position a and communicates with the tank 16, most of the return oil discharged from the hydraulic actuator flows into the tank 16 through the communication position a, which has less resistance than the back pressure check valve 22. As a result, when the makeup is not required, the pressure loss due to the back pressure check valve 22 is eliminated.

  When the vehicle is suddenly decelerated during the turning operation, the rotation of the turning motor 4 does not stop immediately because the inertia of the upper turning body is large even if the turning operation lever 26 is returned to the neutral position. Even in such a case, in the second embodiment, even if the pilot pressure becomes zero, that is, even if the signal pressure does not reach the flow control pilot line 43, the slow return valve 45 is operated by the slow return valve 45. The pressure in the downstream side piping 46 gradually decreases.

  As a result, even if the turning operation lever 26 is suddenly returned to the neutral position, the switching valve 44 does not open immediately but opens with a delay, so that the closed state of the switching valve 44 is maintained while the turning motor 4 is rotating. During the rotation of the turning motor 4, make-up is always performed and cavitation can be prevented. Similarly, when the arm operating lever 27 is suddenly returned to the neutral position, cavitation is prevented.

  In the above-described embodiment, a hydraulic excavator has been described as an example. However, the construction machine of the present invention is applied to any construction machine having a plurality of hydraulic actuators and having a makeup line in a specific hydraulic actuator. Can do.

  In the above-described embodiment, the swing motor and the boom cylinder are described as examples of the specific hydraulic actuator. However, the specific hydraulic actuator may be an arm cylinder and a bucket cylinder.

  For example, when cavitation occurs on the arm cylinder head side during arm pulling operation, a makeup line is connected to the arm cylinder head side. When cavitation occurs on the bucket cylinder head side during bucket excavation, the bucket cylinder head is connected. Connect the makeup line to the side. Further, when cavitation occurs on the boom rod side due to the drop of the boom's own weight, a makeup line is connected to the rod side of the boom cylinder.

1 is a hydraulic circuit showing a first embodiment of a construction machine according to the present invention. FIG. 2 is a diagram for explaining the operation of the hydraulic circuit in FIG. 1, (a) is an operation lever operation amount, (b) is a turning speed, (c) is a switching valve signal, (d) is a makeup flow rate, It is the shown graph. It is the hydraulic circuit which showed 2nd embodiment of the construction machine which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Arm cylinder 2 Boom cylinder 3 Bucket cylinder 4 Rotating motor 5 1st hydraulic pump 6 2nd hydraulic pump 7-10 Control valve 11-15 Return line 16 Tank 18 Makeup line 20 Second makeup line 22 Back pressure check valve 23 Bypass check valve 24 Electromagnetic switching valve 25 Controller 26 Turning operation lever 27 Arm operation lever 28 Turning operation remote control valve 29 Arm operation remote control valve 30, 31 Pilot line 32, 33 Pressure sensor 44 Switching valve

Claims (5)

A plurality of hydraulic actuators, operating means for operating each hydraulic actuator, a return oil path for returning the return oil from each hydraulic actuator to the tank, and a part of the return oil provided in the return oil path for a specific hydraulic pressure A regeneration line for re-supplying the actuator, a flow control valve for adjusting the back pressure in the return oil path to control the regeneration flow re-supplied to the hydraulic actuator by the regeneration line, and controlling the flow control valve Control means for
A back pressure valve and a bypass line that bypasses the back pressure valve are provided in the return oil passage, and the flow rate control valve is provided in the bypass line,
The flow control valve is configured to be switchable between a communication position that bypasses the back pressure valve and communicates with the tank, and a blocking position for generating back pressure by the back pressure valve,
The control means switches the flow rate control valve to the shut-off position when an operation means for operating the specific hydraulic actuator is operated, and after the operation is stopped and the specific actuator is stopped, A construction machine configured to switch a flow control valve to the communication position . A plurality of hydraulic actuators, operating means for operating each hydraulic actuator, a return oil path for returning the return oil from each hydraulic actuator to the tank, and a part of the return oil provided in the return oil path for a specific hydraulic pressure A regeneration line for re-supplying the actuator, a flow control valve for adjusting the back pressure in the return oil path to control the regeneration flow re-supplied to the hydraulic actuator by the regeneration line, and controlling the flow control valve Control means for
  A back pressure valve and a bypass line that bypasses the back pressure valve are provided in the return oil passage, and the flow rate control valve is provided in the bypass line,
  The flow rate control valve is configured to decrease the regeneration flow rate by increasing its opening degree,
  The control means operates in a direction to decrease the opening degree of the flow rate control valve as the operation amount of the operation means increases during a period in which the operation means for operating the specific hydraulic actuator is operated. A construction machine configured to operate in a direction to increase the opening degree of the flow control valve after the specific actuator is stopped after the stop. A pressure sensor for detecting a pilot pressure derived from a remote control valve as the operation means is provided, and the control means is configured to control the flow rate control valve in response to the pilot pressure detected by the pressure sensor. The construction machine according to claim 1. While the hydraulic pilot valve is provided as the flow control valve, it has a hydraulic pilot type control valve that controls the operation of the specific hydraulic actuator by operating a remote control valve as the operation means. From the pilot line of this control valve The construction machine according to claim 2, wherein the flow control pilot line is branched and the control means is configured by providing a slow return valve in the flow control pilot line. A lower traveling body, an upper revolving body mounted on the lower traveling body, and a front attachment with a boom provided on the upper revolving body are provided, and the upper revolving body is swung as the specific hydraulic actuator. The construction machine according to any one of claims 1 to 4, further comprising at least one of a swing motor and a boom cylinder for raising and lowering the boom of the front attachment.

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