JP2009097536A - Hydraulic circuit of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply the pressure oil of higher pressure than main relief pressure, when the load pressure of an actuator exceeds the main relief pressure by a simple circuit constitution. <P>SOLUTION: This hydraulic circuit has a capacity variable main pump 31, a main relief valve 33 setting the delivery pressure of the main pump 31, and a control valve 35 switching and supplying/discharging the delivery pressure of the main pump 31 to the actuator 36, and is provided with a pressure sensor 65 detecting the load pressure of the actuator 36, a hydraulic pressure source 61 of higher pressure than the main relief pressure, a solenoid valve 63 and a controller 60 for supplying the pressure oil to the actuator 36 via the control valve 35 from the higher pressure hydraulic pressure source 61 when the load pressure of the actuator 36 exceeds the main relief pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydraulic circuit of a construction machine, and particularly to a hydraulic circuit that can supply pressure oil higher than the main relief pressure when the load pressure of an actuator exceeds the main relief pressure. .

  FIG. 5 is a general hydraulic circuit diagram of a conventional construction machine of this type, in which 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 is connected to the main pump 31. A main relief valve 33 for controlling the discharged pressure oil 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 pressure oil is supplied to and discharged from an actuator 36 such as a hydraulic cylinder or a hydraulic motor via the control valve 35.

  The discharge circuit 32 passes through the center bypass of the control valve 35 and communicates with the tank 34. 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.

  Load relief valves (port relief valves) 50 and 51 for setting the maximum load pressure of the actuator are provided in the supply / discharge circuits 48 and 49 that connect the control valve 35 and the actuator 36. The load relief pressure set by the load relief valves 50 and 51 is set to be slightly higher than the main relief pressure set by the main relief valve 33 described above. For example, when the main relief pressure is set to 35 MPa, the load relief pressure is set to about 37 MPa.

  Although illustration is omitted, when the operation lever 41 is operated, the control valve 35 is switched to any position, and the pressure oil discharged from the main pump 31 to the discharge circuit 32 passes through the control valve 35 and the supply circuit 48, It is discharged to the actuator 36 through 49. The discharge pressure of the main pump 31 is set at the maximum pressure by the main relief valve 33.

  Here, when the load applied to the actuator 36 during work increases and the load pressure becomes higher than the main relief pressure, it is necessary to supply higher pressure oil to the actuator 36. The oil does not become higher than the main relief pressure set by the main relief valve 33.

In such a case, the set pressure of the main relief valve is changed to a high pressure by operating the changeover switch, and when a high load pressure is applied, the main relief valve does not operate and the higher pressure oil is supplied to the actuator. A hydraulic circuit that can be supplied is known (for example, see Patent Document 1).
JP-A-5-272505

  In the configuration of FIG. 5, when the load pressure of the actuator 36 increases, pressure oil higher than the main relief pressure cannot be supplied, and the supply / discharge circuits 48 and 49 of the actuator have the load relief valves 50 and 51. Relief was performed at the set load relief pressure, resulting in a large energy loss.

  In the invention described in Patent Document 1, the relief pressure of the main relief valve can be switched between a high pressure and a low pressure by operating the changeover switch. Therefore, when the load pressure is high, the discharge amount of the main pump is increased to reduce the relief loss. it can. However, in order to switch the set pressure of the main relief valve, a plurality of solenoid valves, unload valves, and the like are necessary, which complicates the circuit configuration and increases costs.

  Therefore, with a simple circuit configuration, when the load pressure of the actuator exceeds the main relief pressure, there arises a technical problem to be solved in order to be able to supply pressure oil higher than the main relief pressure. The present invention 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 directed to a variable capacity main pump, a main relief valve for setting a discharge pressure of the main pump, and a discharge of the main pump. In a hydraulic circuit having a control valve for switching oil to supply and discharge to the actuator, load pressure detecting means for detecting the load pressure of the actuator, a hydraulic pressure source higher than the main relief pressure, and the load pressure of the actuator being the main relief There is provided a hydraulic circuit for a construction machine, characterized in that high pressure oil supply means for supplying pressure oil to the actuator from the high pressure hydraulic source via the control valve when a pressure is exceeded is provided.

  According to this configuration, the load pressure detecting means detects the load pressure of the actuator, and when the load pressure exceeds the main relief pressure, the high pressure oil supply means controls the pressure oil higher than the main relief pressure from the hydraulic source. The actuator is supplied through a valve.

  According to a second aspect of the present invention, the connection point between the supply circuit of the high-pressure oil supply means and the discharge circuit of the main pump is a location closer to the control valve than the connection point of the main relief valve, and the connection between the two 2. The hydraulic circuit for a construction machine according to claim 1, further comprising a check valve for preventing a flow in a main pump direction from a supply circuit of the high-pressure oil supply means between points.

  According to this configuration, the supply circuit of the high pressure oil supply means is located closer to the control valve than the connection point of the main relief valve, and the check valve is interposed between the connection point of the main relief valve. The high pressure oil led out from the oil pressure source to the supply circuit of the high pressure oil supply means does not flow to the main relief valve side but is supplied to the actuator via the control valve.

  The invention according to claim 3 is characterized in that the load pressure detecting means is a pressure sensor or a pressure switch provided in a supply circuit of the high-pressure oil supply means. I will provide a.

  According to this configuration, since the load pressure detecting means is constituted by a pressure sensor or a pressure switch, when the load pressure of the actuator exceeds the main relief pressure, an increase in the load pressure can be reliably detected.

  According to a fourth aspect of the present invention, when the high pressure oil supply means detects that the load pressure of the actuator has exceeded the main relief pressure by the solenoid valve interposed in the hydraulic pressure supply circuit and the load pressure detection means. A hydraulic circuit for a construction machine according to claim 1, 2 or 3, further comprising a controller for opening the electromagnetic valve.

  According to this configuration, the high pressure oil supply means is constituted by the electromagnetic valve and the controller, and the detection signal of the load pressure detection means is input to the controller. When a detection signal indicating that the load pressure of the actuator exceeds the main relief pressure is input to the controller, the controller outputs a command signal for opening the solenoid valve. Therefore, pressure oil higher than the main relief pressure is led from the hydraulic pressure source to the supply circuit, and high pressure oil is supplied to the actuator via the control valve.

  According to the first aspect of the present invention, when the load pressure of the actuator exceeds the main relief pressure, pressure oil higher than the main relief pressure is supplied to the actuator, so that the actuator can be driven at a high load. By increasing the driving pressure of the actuator, the pressure receiving area of the cylinder can be reduced, the flow rate of pressure oil can be reduced, and the pressure loss can be reduced.

  When the load applied to the actuator is the same, the operating pressure increases due to the decrease in the pressure receiving area due to the increase in pressure, and the working efficiency can be improved. In the case of a low-load actuator, the load pressure difference can be reduced to reduce the amount of throttle on the low-pressure side, thereby further saving energy.

  The main relief pressure is the same as before, and it is possible to increase only a specific actuator. It is only necessary to consider the durability when the actuator is at a high pressure, not the entire hydraulic circuit. It is possible to suppress the influence on the life reduction.

  Moreover, by applying to the hydraulic circuit for bucket cylinders, the work speed can be increased and energy saving can also be achieved.

  According to the second aspect of the present invention, the supply circuit of the high pressure oil supply means is located closer to the control valve than the connection point of the main relief valve, and a check valve is interposed between the connection point of the main relief valve. Therefore, in addition to the effect of the first aspect of the invention, the high pressure oil supplied from the high pressure oil supply means can be efficiently supplied to the actuator without affecting the main relief valve.

  In the invention described in claim 3, since the load pressure detecting means is constituted by a pressure sensor or a pressure switch, in addition to the effect of the invention described in claim 1 or 2, the actuator is at a high load pressure. It can be detected reliably.

  In the invention described in claim 4, since the high-pressure oil supply means is constituted by a solenoid valve and a controller, in addition to the effect of the invention described in claim 1, 2, or 3, the load pressure of the actuator reduces the main relief pressure. Based on the detection signal of exceeding, the controller can open the solenoid valve and reliably supply high pressure oil from the high pressure hydraulic source to the actuator.

  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 object of enabling supply of pressure oil higher than the main relief pressure when the load pressure of the actuator exceeds the main relief pressure with a simple circuit configuration, the present invention is a variable capacity type. Load pressure for detecting the load pressure of the actuator in a hydraulic circuit comprising a main pump, a main relief valve for setting the discharge pressure of the main pump, and a control valve for switching the supply oil of the main pump to supply and discharge to the actuator High pressure oil that supplies pressure oil to the actuator from the high pressure hydraulic source via the control valve when the load pressure of the actuator exceeds the main relief pressure when detecting means, a hydraulic pressure source that is higher than the main relief pressure Realized by providing supply means.

  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 pressure oil is supplied to and discharged from each hydraulic cylinder and hydraulic motor.

  FIG. 2 is a hydraulic circuit diagram. For convenience of explanation, the same components as those of the conventional hydraulic circuit shown in FIG. A component different from FIG. 5 is provided with a hydraulic pressure source 61 having a pressure higher than the main relief pressure set by the main relief valve 33. An electromagnetic valve 63 is interposed in the supply circuit 62 of the hydraulic power source 61, and a check valve 64 for preventing a back flow in the direction of the hydraulic power source 61 is provided on the secondary side of the electromagnetic valve 63. A pressure sensor 65 is provided at the downstream position.

  As will be described later, when the control valve 35 is switched and the pressure oil discharged from the main pump 31 is supplied to the actuator 36, the load pressure of the actuator 36 is detected by the pressure sensor 65, and the detection signal is sent to the controller 60. Enter. The pressure sensor 65 constitutes a load pressure detecting means for the actuator 36. In addition, although illustration is abbreviate | omitted, it can replace with the pressure sensor 65 and can comprise a load pressure detection means with a pressure switch.

  When the load pressure detected by the pressure sensor 65 exceeds the main relief pressure, the electromagnetic valve 63 is opened by a command signal from the controller 60, and pressure oil higher than the main relief pressure is supplied to the hydraulic pressure source 61. To the actuator 36 through the supply circuit 62 and the control valve 35. The electromagnetic valve 63 and the controller 60 constitute high pressure oil supply means for supplying pressure oil from a high pressure hydraulic source 61 to the actuator.

  A connection point 66 between the supply circuit 62 and the discharge circuit 32 of the main pump 31 is located closer to the control valve 35 than a connection point 67 between the main relief valve 33 and the discharge circuit 32, and both connection points 66 and 67. In the meantime, a check valve 68 for preventing the flow of pressure oil from the supply circuit 62 toward the main pump 31 is interposed.

  The main relief pressure set by the main relief valve 33 is set to 35 MPa as in the conventional hydraulic circuit, but the load relief pressure set by the load relief valves (port relief valves) 50 and 51 is conventionally set. Is set to about 42 MPa of high pressure. This is because the actuator 36 can be sufficiently driven even at a high load pressure, as will be described later.

  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 35 is not switched, the pressure oil discharged from the main pump 31 passes through the center bypass of the control valve 35 to the tank 34. Return.

  In this state, since the pressure sensor 65 provided in the supply circuit 62 detects a pressure equal to or lower than the main relief pressure, the controller 60 holds the electromagnetic valve 63 in a closed state, and the pressure oil from the hydraulic source 61 is unloaded. Return to tank 34. Therefore, the energy loss of the hydraulic source 61 is also low.

  On the other hand, as shown in FIG. 3, when the operation lever 41 is operated, that is, when the control valve is switched, the remote control valve 42 is opened and a pilot pressure is generated in the pilot circuit 44 or 46. For example, as shown in the figure, this pilot pressure is led to the pilot port 45 of the control valve 35, the switching operation of the control valve 35 is performed, and the actuator 36 is driven in the direction of the arrow. The load pressure of the actuator 36 is detected by the pressure sensor 65.

  As shown in FIG. 4, the detection signal of the pressure sensor 65 is input to the controller 60, and when it is detected that the load pressure of the actuator 36 exceeds the main relief pressure, a command signal is sent from the controller 60 to the electromagnetic valve 63. , The electromagnetic valve 63 is opened, and the pressure oil from the hydraulic source 61 is led to the supply circuit 62.

  Since the hydraulic pressure source 61 is higher than the main relief pressure, the high pressure oil is supplied to the actuator 36 via the control valve 35, and the actuator 36 is driven by the load relief valves 50 and 51 set to high pressure. Even when a high load is applied to the load relief valve 50, 51, the drive relief force can be fully exerted without relief.

  The connection point 66 of the supply circuit 62 is closer to the control valve 35 than the connection point 67 of the main relief valve 33, and the flow in the direction of the main pump 31 is blocked between the connection points 66 and 67. Since the check valve 68 is interposed, the high pressure oil led out to the supply circuit 62 does not flow to the main relief valve 33 side but is supplied to the actuator 36 via the control valve 35. Therefore, the high pressure oil supplied from the hydraulic source 61 can be efficiently supplied to the actuator 36 without affecting the main relief valve 33.

  Thus, by increasing the driving pressure of the actuator 36, the pressure receiving area of the cylinder can be reduced, the flow rate of the pressure oil can be reduced, and the pressure loss can be reduced. On the other hand, when the load applied to the actuator 36 is the same, the operating pressure increases due to the decrease in the pressure receiving area due to the increase in pressure, and the working efficiency can be improved. In the case of the low-load actuator 36, the load pressure difference can be reduced to reduce the amount of restriction on the low-pressure side, thereby further saving energy.

  The main relief pressure is the same as in the prior art, and it is possible to increase only a specific actuator 36. It is sufficient to consider the durability only when the actuator 36 is at a high pressure, not the entire hydraulic circuit. It is possible to suppress the effect on the lifespan reduction due to the high pressure. In addition, by applying it to the bucket cylinder hydraulic circuit, it is possible to speed up the work and contribute to energy saving.

  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 an operation lever will be in an operation state from the state of FIG. Explanatory drawing when a load pressure becomes high pressure from the state of FIG. Explanatory drawing of the operation lever in the non-operation state in the conventional hydraulic circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hydraulic excavator 31 Main pump 32 Discharge circuit 33 Main relief valve 35 Control valve 36 Actuator 41 Operation lever 42 Remote control valve 50 Load relief valve 51 Load relief valve 60 Controller (high pressure oil supply means)
61 Hydraulic source 62 Supply circuit 63 Solenoid valve (high pressure oil supply means)
65 Pressure sensor (load pressure detection means)
66 Connection point 67 Connection point 68 Check valve

Claims (4)

In a hydraulic circuit having a variable capacity main pump, a main relief valve that sets the discharge pressure of the main pump, and a control valve that switches the discharge oil of the main pump to supply and discharge the actuator,
A load pressure detecting means for detecting the load pressure of the actuator, a hydraulic pressure source higher than the main relief pressure, and when the load pressure of the actuator exceeds the main relief pressure, from the high pressure hydraulic source via the control valve A hydraulic circuit for a construction machine, comprising high pressure oil supply means for supplying pressure oil to an actuator.   The connection point between the supply circuit of the high-pressure oil supply means and the discharge circuit of the main pump is a location closer to the control valve than the connection point of the main relief valve, and the high-pressure oil supply means between both connection points 2. The hydraulic circuit for a construction machine according to claim 1, further comprising a check valve for preventing a flow from the supply circuit toward the main pump.   3. The hydraulic circuit for a construction machine according to claim 1, wherein the load pressure detecting means is a pressure sensor or a pressure switch provided in a supply circuit of the high pressure oil supply means.   The high-pressure oil supply means includes a solenoid valve interposed in the hydraulic power supply circuit, and a controller that opens the solenoid valve when the load pressure detection means detects that the load pressure of the actuator exceeds the main relief pressure. The hydraulic circuit for a construction machine according to claim 1, 2 or 3, characterized by comprising:

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