JP2009097579A - Hydraulic circuit of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To save energy by reducing a delivery quantity of a hydraulic pump when an actuator is not continuously operated for a specific time by an inexpensive constitution. <P>SOLUTION: This hydraulic circuit controls the delivery quantity of the hydraulic pump by selecting either of negative control pressure and external command pressure as high pressure, and is provided with a pressure sensor S detecting the operation state of an operation lever 41 for controlling the actuator and a controller 50 generating the external command pressure higher than the negative control pressure generated by a negative control orifice 37 by a solenoid proportional pressure reducing valve 52 when the non-operated state of the operation lever 41 is continued for a specific time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydraulic circuit for a construction machine, and more particularly to a hydraulic circuit for controlling a discharge amount of a hydraulic pump by selecting either a negative control pressure or an external command pressure in a construction machine having a negative control circuit. is there.

  FIG. 6 is a general hydraulic circuit diagram of a conventional construction machine having a negative control circuit. A variable displacement main pump 31 is driven by the power of the engine 30, and a discharge circuit 32 of the main pump 31 includes A relief valve 33 for controlling the hydraulic oil discharged from the main pump 31 to a constant pressure is provided and connected to the tank 34. A control valve 35 is provided in the middle of the discharge circuit 32, and hydraulic oil is supplied and discharged through the control valve 35 to an actuator 36 such as a hydraulic cylinder or a hydraulic motor.

  The discharge circuit 32 passes through the center bypass of the control valve 35 and communicates with the tank 34 via a negative control throttle 37. The negative control throttle 37 is connected to the tank 34 in parallel with the negative control relief valve 38, and a negative control circuit 39 is branched from the front of the negative control throttle 37. The negative control circuit 39 controls the tilt angle of the main pump 31. It is connected to the regulator 40 to be adjusted.

  Further, as a means for switching the control valve 35 to control the actuator 36, a remote control valve 42 having an operation lever 41 is provided, and a primary port of the remote control valve 42 is connected to the hydraulic power source 43 and the tank 34. The secondary port of the remote control valve 42 is connected to one pilot port 45 of the control valve 35 via one pilot circuit 44 and the other port of the control valve 35 via the other pilot circuit 46. The pilot port 47 is connected.

  FIG. 7 is a graph showing the negative control characteristics. FIG. 7A shows the relationship between the flow rate of the negative control throttle 37 and the negative control relief valve 38 and the negative control pressure, and FIG. 7B shows the negative control pressure and the discharge amount of the main pump. Showing the relationship.

  Although illustration is omitted, when the operation lever 41 is operated and the control valve 35 is switched to any position, the hydraulic oil discharged from the main pump 31 is supplied to the actuator 36 to operate the negative control circuit 39. Since the oil is not derived, the negative control pressure becomes the lowest pressure Pn0 as shown in FIG. As shown in FIG. 7B, when the negative control pressure is the lowest pressure Pn0, the tilt angle of the main pump 31 becomes large, the discharge amount becomes the maximum flow rate Qh, and a large amount of hydraulic oil is supplied to the actuator 36. .

  When the operation lever 41 is returned and the control valve 35 is in the neutral position, the hydraulic oil discharged from the main pump 31 flows to the negative control circuit 39 through the center bypass of the control valve 35, as shown in FIG. In addition, the negative control pressure gradually increases as the negative control throttle flow rate increases. Then, the negative control pressure reaches the maximum Pn1 in the vicinity of Q1 where the negative control relief valve 38 opens. Since the negative control valve 38 opens and communicates with the tank 34 after the Q1 point, the negative control pressure cannot be greater than Pn1.

  As shown in FIG. 7B, as the negative control pressure increases, the tilt angle of the main pump 31 decreases and the discharge amount decreases. When the negative control pressure reaches the maximum Pn1, the discharge amount of the main pump 31 becomes The control valve 35 decreases to the standby flow rate Qs, which is the lowest flow rate with responsiveness. As described above, when the operation lever 41 is in a non-operation state, energy is saved by reducing the discharge amount of the main pump 31 to the standby flow rate Qs.

In addition, by generating an oil pressure that is higher than the negative control maximum pressure Pn1 by an external command, and selecting either the negative control pressure or the external command pressure to act on the regulator, the discharge amount of the main pump is reduced. A hydraulic circuit that can be changed to a flow rate is also known (for example, Patent Document 1 and Patent Document 2).
JP 2002-021808 A JP-A-2005-060970

  In the configuration of FIG. 6, when the control valve 35 reaches the neutral position, the negative control pressure increases and the discharge amount of the main pump 31 decreases to the standby flow rate. However, the standby flow rate Qs has a response at the time of starting the control valve 35. It is about 20cc / rev to secure, and energy loss is large.

  In the invention described in Patent Document 1, when the negative control pressure changes suddenly when the control valve is switched, the pressure reducing valve pressure corresponding to the operation amount of the remote control valve is selected and preferentially supplied to the regulator, thereby hunting the operating lever. This is to prevent the pump discharge amount during non-operation.

  In the invention described in Patent Document 2, in the state where the excavator specification is switched to the crane specification, the pump discharge amount is set to a small flow rate only during the turning operation, and a safe turning speed is ensured. It does not reduce.

  Therefore, when the actuator is not operated continuously for a certain time with an inexpensive configuration, a technical problem to be solved in order to save energy by reducing the discharge amount of the hydraulic pump arises. Aims to solve this problem.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 is a hydraulic circuit for controlling a discharge amount of a hydraulic pump by selecting either a negative control pressure or an external command pressure. A means for detecting an operating state of the operating lever for controlling the actuator, and an external command pressure generating means for generating an external command pressure higher than the negative control pressure when the operating lever is not operated for a predetermined time. A hydraulic circuit for a construction machine is provided.

  According to this configuration, when the operating state of the operating lever for the actuator control is detected by means for detecting the operating state of the operating lever for controlling the actuator, the non-operating state of the operating lever is continued for a certain period of time. An external command pressure higher than the negative control pressure is generated. Therefore, the external command pressure is selected to be high, and the discharge amount of the hydraulic pump becomes a smaller flow rate than the discharge amount set by the negative control pressure.

  According to a second aspect of the present invention, the external command pressure generating means includes: an electromagnetic valve for deriving pressure oil higher than the negative control pressure from the hydraulic power source; and the electromagnetic valve when the non-operating state of the operation lever continues for a predetermined time. 2. A hydraulic circuit for a construction machine according to claim 1, further comprising a controller that opens and extracts pressure oil from a hydraulic source to a negative control circuit.

  According to this configuration, when the controller receives a detection signal indicating that the operation lever is in a non-operation state and the non-operation state continues for a certain period of time, the controller outputs a command signal to the solenoid valve, which is higher than the negative control maximum pressure. The pressure oil is led to the negative control circuit. Therefore, when the external command pressure is selected as a high pressure, the discharge amount of the hydraulic pump becomes smaller than the discharge amount set by the negative control pressure.

  According to the first aspect of the present invention, when the non-operating state of the operation lever continues for a certain time, the external command pressure higher than the negative control pressure is selected, and the discharge amount of the hydraulic pump is set at the negative control pressure. Therefore, the discharge amount of the hydraulic pump when the actuator is not operated can be further reduced from the standby flow rate, thereby further saving energy.

  According to the second aspect of the present invention, when the non-operating state of the operation lever continues for a certain period of time, a command signal is output from the controller to the solenoid valve, and pressure oil higher than the negative control pressure is led to the negative control circuit. In addition to the effect of the invention described in Item 1, further energy saving can be achieved with a simple and inexpensive configuration.

  Hereinafter, the hydraulic circuit of the construction machine according to the present invention will be described with reference to preferred embodiments. In order to achieve the purpose of saving energy by reducing the discharge amount of the hydraulic pump when the actuator is not operated with an inexpensive configuration, the present invention selects either a negative control pressure or an external command pressure as a high pressure Then, in the hydraulic circuit for controlling the discharge amount of the hydraulic pump, the means for detecting the operating state of the operating lever for controlling the actuator and the non-operating state of the operating lever continue for a certain period of time, the pressure is higher than the negative control pressure. Realized by providing external command pressure generating means to generate external command pressure.

  FIG. 1 shows a 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 the main pump is provided by the engine 30 provided on the upper swing body. 31 is driven, and hydraulic oil is supplied to and discharged from each hydraulic cylinder and hydraulic motor.

  2 is a hydraulic circuit diagram. For convenience of explanation, the same components as those of the conventional hydraulic circuit shown in FIG. 6 first includes a shuttle valve 51 in the middle of the negative control circuit 39, connects the circuit on the negative control throttle 37 side to one inlet port of the shuttle valve 51, and connects the other inlet port to the other inlet port. An electromagnetic proportional pressure reducing valve 52 is connected, and the outlet port of the shuttle valve 51 is connected to the regulator 40 of the main pump 31.

  The primary port of the electromagnetic proportional pressure reducing valve 52 is connected to the tank 34 and a hydraulic pressure source 43. When a command signal from the controller 50 is input to the electromagnetic proportional pressure reducing valve 52, the magnitude of the command signal is increased. In response, the pressure oil from the hydraulic source 43 is led to the negative control circuit 39. The negative control pressure generated by the negative control throttle 37 and the external command pressure generated by the electromagnetic proportional pressure reducing valve 52 are selected by the shuttle valve 51 as high pressure, and either high pressure oil acts on the regulator 40 of the main pump 31. In the present invention, the external command pressure is set to be higher than the negative control pressure.

  Further, as means for detecting the operating state of the operating lever 41, a shuttle valve 48 is interposed between the pilot circuits 44 and 46 of the remote control valve 42, and a pressure sensor S is provided at the secondary port of the shuttle valve 48. To the controller 50. Therefore, when the operation lever 41 is operated in any direction, the pilot pressure of the pilot circuit 44 or 46 is selected by the shuttle valve 48 and detected by the pressure sensor S. The controller 50 causes the controller 50 to detect the operation lever 41. It is possible to detect whether is in an operating state or a non-operating state.

  Although not shown, as a means for detecting the operation state of the operation lever 41, in addition to the pressure sensor S, a pressure switch is provided at the secondary port of the shuttle valve 48, and the controller 50 detects the switch-on. May be. Alternatively, a limit switch can be installed in the vicinity of the operation lever 41, and the tilting operation of the operation lever 41 can be detected by the limit switch.

  Next, the operation of the hydraulic circuit of the present invention will be described. As shown in FIG. 2, when the operation lever 41 is not operated, that is, when the control valve 36 is not switched, the hydraulic oil discharged from the main pump 31 passes through the center bypass of the control valve 35 to the tank 34. Returning, the flow rate of the negative control throttle 37 increases and the negative control pressure gradually increases.

  Therefore, as described in FIG. 7, as the negative control pressure acting on the regulator 40 increases, the discharge amount of the main pump 31 decreases, and when the negative control pressure reaches the maximum Pn1, the discharge amount of the main pump 31 is controlled. The valve 35 drops to the standby flow rate Qs, which is the lowest flow rate with responsiveness.

  As described above, the controller 50 detects the non-operation state of the operation lever 41 based on the detection signal of the pressure sensor S. However, when the non-operation state of the operation lever 41 continues for a certain period of time, the controller 50 sends an electromagnetic proportional pressure reducing valve. A command signal is sent to 52.

  As shown in FIG. 3, the electromagnetic proportional pressure reducing valve 52 communicates with the hydraulic pressure source 43 by the command signal from the controller 50, and the pressure oil from the hydraulic pressure source 43 is led to the negative control circuit 39. As described above, since the external command pressure Pn2 generated by the electromagnetic proportional pressure reducing valve 52 is higher than the negative control pressure Pn1 generated by the negative control throttle 37, the external command pressure Pn2 is selected to be high by the shuttle valve 51, and the regulator 40 Act on. Therefore, the discharge amount of the main pump 31 becomes the minimum flow rate Qm with a smaller flow rate than the discharge amount Qs set by the negative control pressure Pn1.

  FIG. 4 is a graph showing the characteristics of the negative control pressure and the external command pressure. In FIG. 4 (a), the two-dot chain line indicates the relationship between the flow rate of the conventional negative control throttle 37 and negative control relief valve 38 and the negative control pressure, and the solid line indicates The graph which shows an external command pressure, the figure (b) is a graph which shows the negative control pressure and the external command pressure, and the relationship of the discharge amount of a main pump. As in the prior art, when the operating lever 41 is in the operating state (negative negative pressure minimum pressure Pn0), the discharge amount of the main pump 31 is the maximum flow rate Qh, and when the operating lever is in the non-operating state, the negative control pressure increases. The discharge amount of the main pump 31 decreases, and the discharge amount of the main pump 31 decreases to the standby flow rate Qs at the negative control pressure maximum pressure Pn1.

  In the present invention, when the non-operating state of the operation lever 41 continues for a certain period of time, an external command pressure Pn2 higher than the negative control pressure Pn1 is generated by a command from the controller 50. Therefore, the high external command pressure Pn2 is Acting on the regulator 40, the tilt angle of the main pump 31 is further reduced to a minimum flow rate Qm.

  Conventionally, the standby flow rate Qs of the main pump 31 has been about 20 cc / rev in order to ensure the responsiveness when starting the control valve 35, but in the present invention, the non-operating state of the operating lever 41 continues for a certain period of time. Then, the discharge amount of the main pump 31 is further reduced to a minimum flow rate Qm of about 5 cc / rev, so that energy loss is reduced. The smaller the minimum flow rate Qm, the more energy is saved, but it is determined in consideration of the cooling performance of the equipment.

  As shown in FIG. 5, when the operation lever 41 is operated again, the controller 50 can detect that the operation lever 41 is in the operation state by the detection signal of the pressure sensor S. At that time, the command signal from the controller 50 to the electromagnetic proportional pressure reducing valve 52 is stopped, and the electromagnetic proportional pressure reducing valve 52 communicates with the tank 34. Therefore, the pressure oil from the hydraulic source 43 is not led to the negative control circuit 39, and the external command Pressure Pn2 is eliminated.

  Further, since the control valve 47 is switched by the operation of the operation lever 41, the hydraulic oil does not flow to the negative control circuit 39, and the negative control pressure becomes the lowest pressure Pn0. Accordingly, the tilt angle of the main pump 31 is increased, the discharge amount is increased to the maximum flow rate Qh, and a large amount of hydraulic oil is supplied from the main pump 31 to the actuator 36 via the control valve 35.

  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. Explanatory drawing of an operation lever non-operation state in the hydraulic circuit which concerns on this invention. Explanatory drawing when the non-operation state of FIG. 2 continues for a fixed time. The graph which shows the characteristic of the negative control pressure and external command pressure in this invention. Explanatory drawing when an operation lever will be in an operation state from the state of FIG. Explanatory drawing of the operation lever in the non-operation state in the conventional hydraulic circuit. Graph showing negative control characteristics in conventional hydraulic circuits

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hydraulic excavator 31 Main pump 35 Control valve 37 Negative control throttling 39 Negative control circuit 40 Regulator 41 Operation lever 42 Remote control valve 43 Hydraulic source 48 Shuttle valve 50 Controller 51 Shuttle valve 52 Electromagnetic proportional valve S Pressure sensor
Qh Maximum flow rate
Qs Standby flow
Qm Minimum flow rate
Pn0 Negative control minimum pressure
Pn1 Maximum negative pressure
Pn2 External command pressure

Claims (2)

In the hydraulic circuit that controls the discharge amount of the hydraulic pump by selecting either negative control pressure or external command pressure high pressure,
Means for detecting the operating state of the operating lever for controlling the actuator and external command pressure generating means for generating an external command pressure higher than the negative control pressure when the non-operating state of the operating lever continues for a certain period of time are provided. A hydraulic circuit of a construction machine characterized by the above.   The external command pressure generating means includes an electromagnetic valve for deriving pressure oil higher than the negative control pressure from the hydraulic pressure source, and opens the electromagnetic valve when the non-operating state of the operation lever continues for a certain period of time to supply pressure oil from the hydraulic pressure source. 2. The hydraulic circuit for a construction machine according to claim 1, further comprising a controller that is led to a negative control circuit.

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