JP2000266007A - Flow controlling device for hydraulic excavator and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow controlling device and method for handling operations with work of different conditions and conducting reliefcut control as required. SOLUTION: This device and method comprises an operating condition detecting means 28 detecting an operating condition of a hydraulic actuator 11, a pump pressure detecting means 29 detecting discharge pressure of pressure oil discharged from a hydraulic pump 3, a controlling means 27 inputting detection signals from the operation condition detecting means 28 and the pump pressure detecting means 29, and a flow adjusting means 26 adjusting a pressure oil discharge flow of the hydraulic pump 3. When detecting a particular operating condition of the hydraulic actuator 11 and keeping the discharge pressure more than the predetermined reliefcut pressure for given time, the controlling means 27 decreases the pressure oil discharge flow of the hydraulic pump 3 to a reliefcut flow by the adjusting means 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control device and method used for relief cut control of a hydraulic shovel.

[0002]

2. Description of the Related Art Some conventional hydraulic excavators perform a control called relief cut control to reduce a pump discharge flow rate when a pump pressure reaches a relief cut pressure. When this relief cut control is performed, for example,
When rocks or the like hit the bucket during excavation work of the hydraulic excavator and an overload is applied, energy loss of hydraulic oil due to relief operation can be prevented and relief noise can be reduced. Further, since no shock is generated at the time of the relief operation, smooth operation can be performed, and the heat balance of the hydraulic oil and the devices can be improved.

An example of the prior art employing such a relief cut control will be described below. FIG. 7 shows Patent Publication No. 2
It is a relief circuit diagram described in No. 613459. In this relief circuit, the secondary port d of the relief valve 38 for regulating the discharge pressure of the hydraulic pump 13 is connected to the throttle valve 3.
7 and the throttle valve 3
The pressure on the upstream side is used as a pilot pressure for controlling the flow rate of the pump, and is guided to the regulator 34 of the hydraulic pump 13 through the pilot line 40. Note 3
Reference numeral 6 denotes a switching valve that controls the hydraulic actuator 35.

When an overload acts on the hydraulic actuator 35 during the operation of the hydraulic excavator having the relief circuit shown in FIG. 7, the pressure in the pump discharge side pipe line 39 increases, so that the relief valve 38 operates the relief valve. I do. At the same time, in this case, since the throttle valve 37 is interposed in the pipe connecting the secondary port d of the relief valve 38 and the oil tank 33, a slight low pressure is generated upstream of the throttle valve 37. . The hydraulic pressure on the upstream side of the throttle valve 37 acts on the regulator 34 of the hydraulic pump 13 through the pilot line 40 as pilot pressure. Thereby, the hydraulic pump 13
Is adjusted, and the pump discharge flow rate decreases.

FIG. 8 shows a hydraulic circuit described in Japanese Patent Application Laid-Open No. Hei 6-81773. A hydraulic pump 54 that is rotationally driven by the engine 53 includes a controller 52
Is controlled by The controller 52 receives a request flow signal from the operation lever 51 and a pump discharge pressure signal from the pressure sensor 55. The calculation result of the controller 52 is output to the swash plate angle actuator 56 of the hydraulic pump 54 as a pump flow control signal. Reference numeral 57 denotes a switching valve for controlling a hydraulic actuator (not shown).

In the hydraulic circuit shown in FIG. 8, if the pump discharge pressure detected by the pressure sensor is equal to or higher than a set value, the controller 52 starts a timer. The required flow rate is minimized and relief cut control is performed.
Further, if the pump discharge pressure becomes equal to or less than the set pressure, the controller 52 starts a timer. If the pressure equal to or less than the set pressure continues for more than the set time, the required flow rate for the hydraulic pump 54 is returned to the maximum and the relief cut state is released. By performing such control, the relief cut state is not switched for a moment even if the pump discharge pressure changes for a moment, and the pump can be operated stably.

[0007]

However, in each of the prior arts shown in FIGS. 7 and 8, the relief cut control is performed only on the basis of the relief set pressure of the relief valve. That is, the relief cut control is performed irrespective of what kind of work the hydraulic excavator is performing and under what conditions.

In general, it is known that, when the relief cut control is performed, the operator who operates the hydraulic excavator feels an uncomfortable feeling or an impression that the power has disappeared as a natural result of a decrease in the pump discharge flow rate.

According to the prior art hydraulic excavator, the relief cut control is always performed every time the load acting on the hydraulic actuator is increased to a certain extent, so that each time the operator feels uncomfortable and feels that the force is gone. It will be. In some cases, work may not be able to be continued due to insufficient pump discharge flow rate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has been developed in consideration of various kinds of complicated operations under various conditions such as excavation work, crushing work, leveling work, and the like performed by a hydraulic shovel. An object of the present invention is to provide a flow rate control device and a flow rate control method capable of performing relief cut control only in a vehicle.

[0011]

According to a first aspect of the present invention, there is provided a hydraulic pump driven by an engine, a hydraulic actuator driven by pressure oil discharged from the hydraulic pump, and A control valve for controlling the supply of pressurized oil, operating means for switching the control valve, and a relief valve interposed in a discharge oil passage from the hydraulic pump to limit a maximum pressure in the discharge oil passage. An operating state detecting means for detecting an operating state of the hydraulic actuator, a pump pressure detecting means for detecting a discharge pressure of hydraulic oil discharged from the hydraulic pump, and the operating state detecting means And a control signal to which a detection signal from the pump pressure detecting means is input, and the hydraulic pump based on an output signal from the control means. Flow rate adjusting means for adjusting a pressure oil discharge flow rate of the hydraulic pump, a specific operation state of the hydraulic actuator is detected, and the discharge pressure is maintained at a state of not less than a predetermined relief cut pressure for a predetermined time. To
The control means reduces the pressure oil discharge flow rate of the hydraulic pump to a relief cut flow rate by the adjusting means.

According to a second aspect of the present invention, in the hydraulic shovel flow control device according to the first aspect, the specific operation state of the hydraulic actuator is such that an attachment of the hydraulic shovel driven by the hydraulic actuator is a predetermined one. And that the operation means is operated to a predetermined amount or more.

According to a third aspect of the present invention, in the hydraulic shovel flow control device according to the first aspect, an engine rotation state detecting means for detecting a rotation state of the engine and inputting a detection signal to the control means. A specific operation state of the hydraulic actuator is detected, and in addition to maintaining the state in which the discharge pressure is equal to or higher than a predetermined relief cut pressure for a predetermined time, the number of revolutions of the engine is in a predetermined high rotation state When the engine rotation state detecting means detects that the pressure is in the range, the control means reduces the pressure oil discharge flow rate of the hydraulic pump to the relief cut flow rate by the adjusting means.

According to a fourth aspect of the present invention, in the flow rate control device for a hydraulic shovel according to the third aspect, the predetermined high rotation state is a state in which the rotation of the engine is equal to or higher than a predetermined rotation number for a predetermined time. And the operation position of the throttle lever for setting the rotation of the engine is set to a high speed side.

According to a fifth aspect of the present invention, there is provided a hydraulic excavator flow control device according to the first aspect, wherein
A hydraulic pump and other drive characteristics are set as a work mode and a work mode setting means for inputting a setting signal to the control means, a specific operation state of the hydraulic actuator is detected, and the discharge pressure is reduced to a predetermined relief cut. In addition to holding the state equal to or higher than the pressure for a predetermined time, when the predetermined operation mode is set by the operation mode setting unit, the control unit controls the hydraulic oil discharge flow rate of the hydraulic pump by the adjustment unit. It is characterized in that it is reduced to the relief cut flow rate.

According to a sixth aspect of the present invention, in the flow rate control device for a hydraulic shovel according to any one of the first to fifth aspects, when the discharge flow rate of the hydraulic pump is reduced to the relief cut flow rate, the flow rate gradually decreases. The discharge flow rate is reduced, and the discharge flow rate is gradually increased even when the relief cut state is released.

According to a seventh aspect of the present invention, there is provided a hydraulic shovel for limiting the maximum pressure in a discharge oil passage by a relief valve interposed in a discharge oil passage for pressurized oil from a hydraulic pump to a hydraulic actuator. In the control method, an operation state of the hydraulic actuator is detected, a discharge pressure of pressure oil discharged from the hydraulic pump is detected, a specific operation state of the hydraulic actuator is detected, and the discharge pressure is a predetermined pressure. When a state at or above the relief cut pressure is maintained for a predetermined time, the pressure oil discharge flow rate of the hydraulic pump is reduced to the relief cut flow rate.

According to an eighth aspect of the present invention, in the method of controlling a flow rate of a hydraulic shovel according to the seventh aspect, a state of rotation of the engine is detected, a specific operation state of the hydraulic actuator is detected, and the discharge of the discharge is performed. In addition to maintaining the state where the pressure is equal to or higher than the predetermined relief cut pressure for a predetermined time, when detecting that the engine speed is in a predetermined high rotation state, the hydraulic oil discharge flow rate of the hydraulic pump is determined. It is characterized in that it is reduced to the relief cut flow rate.

According to a ninth aspect of the present invention, there is provided a hydraulic shovel flow control method according to the seventh aspect, further comprising:
The hydraulic pump and other drive characteristics are set as a work mode, a specific operation state of the hydraulic actuator is detected, and the discharge pressure is maintained at a state equal to or higher than a predetermined relief cut pressure for a predetermined time. , When the work mode is set to a predetermined work mode,
The hydraulic oil discharge flow rate of the hydraulic pump is reduced to a relief cut flow rate.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit diagram illustrating a flow control device for a hydraulic shovel according to the present invention. In the figure, reference numeral 2 denotes an engine mounted on a hydraulic shovel, 3 denotes a hydraulic pump which is driven by the engine 2 to discharge pressure oil, 10 denotes a pilot pump which discharges a pilot primary pressure, and 11 denotes a hydraulic pump 3 discharges from the hydraulic pump 3. A hydraulic cylinder 14, which is a hydraulic actuator driven by pressure oil, is a control valve for controlling the supply of pressure oil to the hydraulic cylinder 11. Reference numeral 15 denotes a hydraulic remote control valve as an operating means for switching the control valve 14, 16 denotes an operation lever of the hydraulic remote control valve 15, 17L and 17R denote pilot valves, respectively, and 18 denotes a pilot secondary pressure derived from the pilot valve 17L or 17R. Shuttle valve to select. Reference numeral 19 denotes a relief valve which is provided in a pipeline 22-22 ′ leading from the discharge pipe 20 of the hydraulic pump 3 to the oil tank 21 and limits the maximum pressure of the pressure oil in the discharge pipe 20. 23 is a low pressure relief valve for negative control, 24 is a throttle portion connected in parallel with the low pressure relief valve 23, 25
Is an electromagnetic proportional pressure reducing valve as an electro-oil converter. Symbols XX and YY indicate the connections of the pilot pipeline.

In FIG. 1, reference numeral 26 denotes a regulator for tilting the pump swash plate, which is flow rate adjusting means for adjusting the pressure oil discharge flow rate of the hydraulic pump 3 based on an output signal from a controller 27 as control means. Reference numeral 28 denotes a pilot pressure sensor that detects an operation state of the hydraulic remote control valve 15. This pilot pressure sensor 28 operates as one of the operation state detecting means. Reference numeral 29 denotes a pump pressure sensor as pump pressure detecting means for detecting the discharge pressure of the pressure oil discharged from the hydraulic pump 3 in the discharge pipe line 20.
Reference numeral 31 denotes a rotation sensor for detecting the rotation speed of the engine 2;
Is a throttle lever device for setting the engine 2 to a low speed side (L side) and a high speed side (F side); 41 is a throttle lever of a throttle lever device 32;
1 is a potentiometer for detecting an operation position. Reference numeral 43 denotes a work mode changeover switch. The work mode changeover switch 43 changes the drive characteristics of the engine 2, the hydraulic pump 3, and the like to H ( For heavy load), S
One of the required operation modes is selected from a plurality of types of operation modes (for normal load operation) and FC (for light load fine operation). Pilot pressure sensor 28, pump pressure sensor 29, rotation sensor 31, potentiometer 4
2. A part of the detection signal or the set value of the work mode changeover switch 43 is input to the controller 27 for the control of the present invention.

In the present invention, unlike the prior art in which the relief cut control is always performed when the discharge pressure of the hydraulic pump reaches a predetermined relief cut pressure, even if the discharge pressure of the hydraulic pump 3 becomes the relief cut pressure, Unless a predetermined condition is satisfied, the relief cut control is not performed.

There are several examples of the predetermined condition, which will be described below. First, an example is conceivable in which the following two conditions are provided, and the relief cut control is performed only when both of these conditions are satisfied (Embodiment 1). Condition: The state in which the discharge pressure of the hydraulic pump 3 is equal to or higher than a predetermined relief cut pressure is maintained for a predetermined time. Condition: The hydraulic actuator is in a specific operating state.

The “specific operation state” of this condition means that the attachment of the hydraulic excavator driven by the hydraulic actuator is of a specific type (for example, a crusher) and that the operating means is operated by a predetermined amount or more. Or at least one of the following.

Next, an example is conceivable in which the following conditions are provided in addition to the above-mentioned conditions, and the relief cut control is performed only when all three conditions are satisfied (Embodiment 2). Condition: The rotation speed of the engine 2 is in a predetermined high rotation state. The “high rotation state” of this condition means that the state where the rotation speed of the engine 2 is equal to or higher than a predetermined rotation speed is maintained for a predetermined time or the throttle lever is set to a high speed side.

Next, an example is conceivable in which the following conditions are provided in addition to the above-mentioned conditions and the relief cut control is performed only when all three conditions are satisfied (Embodiment 3). Condition: The work mode changeover switch 43 is in a state of selecting a predetermined mode (for example, a heavy load mode H).

Next, an example is conceivable in which relief cut control is performed only when all four of the above conditions are satisfied (Embodiment 4).

Hereinafter, with respect to these embodiments 1 to 4,
Returning to FIG. However, FIG. 1 is drawn as if all of the conditions were considered from the above conditions (that is, a flow control device corresponding to the fourth embodiment).
This is for the convenience of explaining all of the first to fourth embodiments with reference to FIG. 1. As will be apparent from the following description, only the detection values and set values necessary in each embodiment are input to the controller 27. That is enough.

First, the first embodiment will be described. During the operation of the hydraulic excavator, the pump pressure sensor 29 detects the discharge pressure of the hydraulic oil discharged from the hydraulic pump 3 in the discharge line 20, and inputs a detection signal to the controller 27 every moment. Further, a pilot pressure sensor 28 detects a pilot pressure of the hydraulic remote control valve 15 and inputs a detection signal to the controller 27 every moment. Controller 27
Determines the operation amount of the hydraulic remote control valve 15 based on the detection signal from the pilot pressure sensor 28. When the hydraulic shovel is provided with a predetermined attachment other than a digging bucket as an attachment, for example, a crusher for crushing work, an operation lever, an operation pedal, an operation switch, or the like for operating the predetermined attachment ( (Not shown) is input to the controller 27 so that the controller 27 can determine what attachment the hydraulic actuator 11 is driving. An operation lever, an operation pedal, an operation switch, or the like for operating the predetermined attachment and the pilot pressure sensor 28 constitute an operation state detection unit.

Then, the operation state detecting means detects that the hydraulic actuator 11 is in a specific operation state, and the discharge pressure is higher than a predetermined relief cut pressure (for example, 29.4 MPa) for a predetermined time (for example, 29.4 MPa). 1
When the pressure is held for (seconds), the controller 27 outputs a command value signal for adjusting the pressure oil discharge flow rate of the hydraulic pump 3 to the regulator 26 via the electromagnetic proportional pressure reducing valve 25. With this command value signal, the pressure oil discharge flow rate of the hydraulic pump 3 can be reduced to a predetermined relief cut flow rate. The specific operation state of the hydraulic actuator 11 is
As described above, it is detected that the attachment of the hydraulic excavator driven by the hydraulic actuator 11 is of a specific type (for example, a crusher), and / or the hydraulic remote control valve is located on the basis of the detection signal of the pilot pressure sensor 28. This is the state where it is determined that the operation is performed more than the fixed amount.

Next, a second embodiment will be described. Embodiment 1
In addition to the case, the rotation speed of the engine 2 is detected by the rotation sensor 31 and input to the controller 27,
Alternatively, an output signal of the potentiometer 42 for detecting the operation position of the throttle lever 41 is input to the controller 27. The rotation sensor 31 or the potentiometer 42 constitutes an engine rotation state detecting means.

Then, it is detected that the hydraulic actuator 11 is in a specific operation state, the state in which the discharge pressure is equal to or higher than a predetermined relief cut pressure is maintained for a predetermined time, and the rotational speed of the engine 2 is maintained at a predetermined rotational speed. When the above state is maintained for a predetermined time, or when the throttle lever 41
Is set to the high speed side (F side), the controller 27 outputs a command value signal for adjusting the pressure oil discharge flow rate of the hydraulic pump 3 to the regulator 26 via the electromagnetic proportional pressure reducing valve 25. With this command value signal, the pressure oil discharge flow rate of the hydraulic pump 3 can be reduced to a predetermined relief cut flow rate.

Next, a third embodiment will be described. Embodiment 1
In addition to the above case, the third embodiment has a work mode switching switch 43 for setting the drive characteristics of the engine 2, the hydraulic pump 3 and the like as a work mode according to a plurality of work types. Input to the controller 27. The work modes include, for example, a mode H for heavy load, a mode S for normal load, and a mode FC for light load fine operation.
Any of the required operation modes can be selected.

Then, when it is detected that the hydraulic actuator 11 is in a specific operation state and the state in which the discharge pressure is equal to or higher than a predetermined relief cut pressure is maintained for a predetermined time, the operation mode switch 43 is used. When a predetermined work mode, for example, a heavy load mode H, is set, the controller 27
A command value signal for adjusting the pressure oil discharge flow rate of the hydraulic pump 3 is output to the regulator 26 via the control signal 5. With this command value signal, the pressure oil discharge flow rate of the hydraulic pump 3 can be reduced to a predetermined relief cut flow rate.

The fourth embodiment is an example in which the conditions for engine rotation as in the second embodiment are added in addition to the third embodiment.

In the first to fourth embodiments, it goes without saying that, after the conditions of the relief cut control are all the same and the pressure oil discharge flow rate of the hydraulic pump 3 is reduced to the relief cut flow rate, the controller 27 continues to perform the respective operations. When receiving a detection signal or the like and continuing for a predetermined time outside the condition of the relief cut control, the relief cut control is released.

Accordingly, when the condition is not satisfied and the predetermined time is maintained, the relief cut flow rate adjustment is not performed, so that a problem that an unnecessary relief cut flow state occurs during the operation of the hydraulic shovel is reliably prevented. be able to.

Next, the setting of the relief cut pressure will be described with reference to FIG. FIG. 2 is a diagram showing a pressure waveform of the discharge pressure of the hydraulic pump 3. Controller 27
When the detection signal of the pump pressure sensor 29 indicates a predetermined pressure waveform, the pressure waveform state lasts for a predetermined time, and the detection signal indicates a predetermined pressure or more, it is determined that this is a relief cut state. An average value Pa of the discharge pressure at this time within a predetermined time is calculated, and the relief cut pressure is determined based on the average value Pa. The reason for calculating the average value is that it is more accurate to take the average within a predetermined time because the discharge pressure fluctuates finely.

Accordingly, when the hydraulic shovel performs work by mounting work machines having different working pressures, for example, a normal digging bucket (not shown) is mounted as the work machine,
The relief set pressure at that time is used at 34.3 MPa,
Alternatively, a rock crusher (not shown) is installed as a working machine, and the relief pressure at that time is set to 24.5M.
Even when using at Pa, the relief cut pressure can be set freely according to the operation of each work machine, which is very convenient.

Further, the controller 27 counts a second predetermined time (for example, 10 hours) longer than the predetermined time, calculates the average value a plurality of times within the second predetermined time, and calculates the plurality of average values. The relief cut pressure is determined based on the highest one.

Thus, the average value Pα can be calculated a plurality of times within the second predetermined time (for example, 10 hours), and the relief cut pressure can be newly set based on the highest one of the plurality of average values Pα. It is possible to eliminate the problem that the relief cut pressure of the relief valve 19 is reduced due to a change with time, and to manage the relief valve 19 so that the relief valve 19 operates normally.

Further, the controller 27 is provided with the second
After the elapse of a predetermined time (for example, 10 hours), the determined relief cut pressure is set as the predetermined relief cut pressure, and the relief cut pressure determined after the setting is cleared (pressure = 0). The second predetermined time is newly counted.

Accordingly, the average value Pα of the pump pressure (discharge pressure of the hydraulic pump 3) is constantly inspected, and the relief cut pressure is updated and set based on the maximum relief pressure when the condition for establishing the relief state is satisfied. After the update setting, the maximum relief pressure is cleared (= 0). Therefore, it can be maintained that the relief valve 19 always operates at the normal relief cutoff pressure.

FIG. 3 is a flowchart showing a function of the controller 27 for controlling the setting of the relief cut-off pressure relating to the update of the relief cut-off pressure. When the relief pressure decreases due to the temporal change of the relief valve 19, a pressure (relief cut pressure) equal to or higher than the pump pressure for performing the relief cut is reached, and the pressure may not be held for a certain time, for example, one second. . In order to prevent this problem, the controller 27 constantly monitors the pump pressure of the hydraulic pump 3 (average value Pα of several times of the pump discharge pressure), and sets the maximum value when the condition for establishing the relief state is satisfied. It is stored as a relief pressure. And
The relief cutoff pressure is updated every predetermined time (for example, an operation time of 10 hours) (the relief cutoff pressure is created based on the maximum relief pressure) and stored. After updating, the maximum relief pressure is cleared (= 0).

FIG. 4 is a flowchart showing a function of the controller 27 relating to the relief cut control ON. Here, the description will be made under the conditions of the second embodiment. After updating the relief cutoff pressure of the relief valve 19 (S1), whether the engine 2 rotation speed is equal to or higher than a predetermined rotation speed (S2), whether it is in a specific operation state (S3), or whether the pump pressure is equal to or higher than the relief cutoff pressure (S4). If the condition is satisfied, if this condition continues for a predetermined time (S5, S6), the relief cut-off flag = ON (S7), and the command value signal is sent from the controller 27 to the electromagnetic proportional pressure reducing valve 25. Is output (S8). FIG. 5 is a flowchart showing a command value of a signal output from the controller 27 for performing the relief cut control to the electromagnetic proportional pressure reducing valve 25.

When the discharge flow rate of the hydraulic pump 3 is reduced to the relief cut flow rate, the discharge flow rate may be gradually reduced, and when the relief cut state is released, the discharge flow rate may be gradually increased. FIG.
FIG. 9 is a rate limiter diagram of a relief cutoff command value output from the controller 27 to the electromagnetic proportional pressure reducing valve 25 when the relief valve 19 is operated for relief cutoff. As shown in FIG. 6, when the pump discharge flow rate is the maximum discharge amount, the point A when the relief valve 19 starts the relief cutoff operation (relief cutoff flag = ON).
Becomes smaller as the time t elapses, and reaches the time point B of the minimum discharge amount command value. Then, a time point C at which the relief cutoff operation is completed after a predetermined time t has elapsed (relief cutoff flag = OFF)
Becomes a large value in proportion to the elapse of the time t, and reaches the time point D of the maximum discharge amount command value. That is, the change in the pump discharge flow rate suddenly decreases in a step-like manner,
Since the above command value is output so as not to be increased (so as to gradually reduce and increase the pump discharge flow rate), when the relief valve 19 operates the relief cutoff during the operation of the hydraulic excavator, the operator performing the driving operation is operated. "Discomfort" and "impression of lack of power" can be eliminated.

Although the negative control hydraulic circuit is used as the hydraulic circuit of the excavator in the flow control device of the present embodiment, the present invention is not limited to the negative control hydraulic circuit, but may be applied to other flow control devices such as a positive control hydraulic circuit. It is also possible to apply.

[0048]

According to the present invention according to claims 1 to 9,
Relief cut control can be performed only when necessary in response to complicated and various types of work under various conditions such as excavation work, crushing work, leveling work, and the like performed by a hydraulic shovel.

According to the first, second and seventh aspects of the present invention, even when the state in which the discharge pressure is equal to or higher than the predetermined relief cut pressure is maintained for a predetermined time, only when the hydraulic actuator is in a specific operation state. Thus, relief cut control is performed. Therefore, for example, the relief cut control can be performed only when a special attachment such as a crusher is used, or the relief cut control can be performed only when a full lever operation or a lever operation similar thereto is performed.

According to the third, fourth and eighth aspects of the present invention, the condition of the high-speed engine rotation can be added as a condition for the relief cut control.

According to the fifth and eighth aspects of the present invention, a case where the operation mode is a predetermined operation mode, for example, a heavy excavation mode, can be added as a condition for the relief cut control.

As described above, the relief cut control can be performed by appropriately combining necessary conditions.

Furthermore, when the hydraulic oil discharge flow rate of the hydraulic pump is reduced to the relief cut flow rate, the discharge flow rate is gradually reduced, and when the relief cut state is released, the discharge flow rate is gradually increased. In addition, when the relief valve operates the relief cutoff during the operation of the hydraulic excavator, it is possible to eliminate the "uncomfortable feeling" and the "impression that the force is gone" felt by the operator performing the driving operation.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a flow rate control device for a hydraulic shovel according to the present invention.

FIG. 2 is a diagram showing a pressure waveform of a discharge pressure of a hydraulic pump.

FIG. 3 is a flowchart illustrating a function of a controller related to updating a relief cutoff pressure.

FIG. 4 is a flowchart showing a function related to relief cut control ON of a controller.

FIG. 5 is a flowchart showing a command value of a signal output from a controller.

FIG. 6 is a rate limiter diagram of a relief cutoff command value output from a controller.

FIG. 7 is a prior art relief circuit diagram.

FIG. 8 is another prior art circuit diagram.

[Explanation of symbols]

 2 Engine 3 Hydraulic pump 11 Hydraulic actuator (hydraulic cylinder) 14 Control valve 15 Hydraulic remote control valve (operating means) 19 Relief valve 26 Regulator (flow rate adjusting means) 27 Controller (control means) 28 Pilot pressure sensor (operating state detecting means) 29 Pump pressure sensor (pump pressure detection means) 31 Rotation sensor (engine rotation state detection means) 41 Throttle lever 42 Potentiometer (engine rotation state detection means) 43 Work mode switching switch

Claims (9)

[Claims] A hydraulic pump driven by an engine; a hydraulic actuator driven by hydraulic oil discharged from the hydraulic pump; a control valve for controlling supply of hydraulic oil to the hydraulic actuator; A flow control device for a hydraulic shovel, comprising: an operation unit for switching a valve; and a relief valve interposed in a discharge oil passage from the hydraulic pump to limit a maximum pressure in the discharge oil passage. Operation state detection means for detecting an operation state, pump pressure detection means for detecting a discharge pressure of pressure oil discharged from the hydraulic pump,
Control means to which detection signals from the operation state detection means and the pump pressure detection means are inputted, and flow rate adjustment means for adjusting a pressure oil discharge flow rate of the hydraulic pump by an output signal from the control means. When a specific operation state of the hydraulic actuator is detected and the state in which the discharge pressure is equal to or higher than a predetermined relief cut pressure is maintained for a predetermined time, the control unit controls the hydraulic oil of the hydraulic pump by the adjustment unit. A flow control device for a hydraulic shovel, wherein a discharge flow rate is reduced to a relief cut flow rate. 2. The specific operation state of the hydraulic actuator is that an attachment of a hydraulic shovel driven by the hydraulic actuator is of a predetermined type.
2. The flow control device for a hydraulic shovel according to claim 1, wherein the operation means is operated at a predetermined amount or more. 3. An engine rotation state detection means for detecting a rotation state of the engine and inputting a detection signal to the control means, wherein a specific operation state of the hydraulic actuator is detected and the discharge pressure is set to a predetermined value. In addition to holding the state equal to or higher than the relief cut pressure for a predetermined time, when the engine rotation state detection unit detects that the engine speed is in a predetermined high rotation state, the control unit performs the adjustment. 2. The flow control device for a hydraulic shovel according to claim 1, wherein the hydraulic oil discharge flow rate of the hydraulic pump is reduced to a relief cut flow rate by means. 4. The predetermined high rotation state means that the rotation of the engine is maintained at a predetermined rotation speed or higher for a predetermined time, and the operation position of a throttle lever for setting the rotation of the engine is set to a high speed side. The flow control device for a hydraulic shovel according to claim 3, wherein the flow control device is one of: 5. An operation mode setting means for setting an engine, a hydraulic pump and other driving characteristics as a work mode and inputting a setting signal to the control means, wherein a specific operation state of the hydraulic actuator is detected. In addition to holding the state where the discharge pressure is equal to or higher than the predetermined relief cut pressure for a predetermined time, when the predetermined operation mode is set by the operation mode setting unit, the control unit controls the hydraulic pressure by the adjustment unit. 2. The hydraulic excavator flow control device according to claim 1, wherein the pressure oil discharge flow rate of the pump is reduced to a relief cut flow rate. 6. When the discharge flow rate of the hydraulic pump is reduced to the relief cut flow rate, the discharge flow rate is gradually reduced, and also when the relief cut state is released, the discharge flow rate is gradually increased. The flow control device for a hydraulic shovel according to any one of claims 1 to 5, wherein: 7. A flow control method for a hydraulic shovel, wherein a maximum pressure in a discharge oil passage is limited by a relief valve interposed in a discharge oil passage for hydraulic oil from a hydraulic pump to a hydraulic actuator. Detect the condition,
Detecting a discharge pressure of hydraulic oil discharged from the hydraulic pump, detecting a specific operation state of the hydraulic actuator, and holding the discharge pressure at or above a predetermined relief cut pressure for a predetermined time; A flow rate control method for a hydraulic shovel, wherein the hydraulic oil discharge flow rate of the hydraulic pump is reduced to a relief cut flow rate. 8. In addition to detecting a state of rotation of the engine, detecting a specific operation state of the hydraulic actuator, and maintaining the state in which the discharge pressure is equal to or higher than a predetermined relief cut pressure for a predetermined time, The hydraulic shovel according to claim 7, wherein when detecting that the engine speed is in a predetermined high rotation state, the hydraulic oil discharge flow rate of the hydraulic pump is reduced to a relief cut flow rate. Flow control method. 9. The operating mode of the engine, the hydraulic pump, and other driving characteristics is set as a working mode, a specific operating state of the hydraulic actuator is detected, and a state in which the discharge pressure is equal to or higher than a predetermined relief cut pressure is determined. 8. The method according to claim 7, wherein, in addition to holding the time, when the operation mode is set to a predetermined operation mode, the hydraulic oil discharge flow rate of the hydraulic pump is reduced to a relief cut flow rate. Hydraulic excavator flow control method.