JPH0941427A - Hydraulic working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid situation of causing unexpected operation of a hydraulic actuator when detecting means for detecting an operating quantity of an operating lever or a working quantity of a directional control valve according to the operating quantity fails in a hydraulic actuator such as boom cylinder. SOLUTION: When a boom is raised, a pilot pressure to a directional control valve 14 according to an operating quantity of an operation lever 6 is detected by a pressure sensor 26. When the detected value is less than a prescribed combined switching pressure, pressure oil is supplied to a boom cylinder 1 only from a first hydraulic pump 2. When the detected value is the combined switching pressure or more, the pressure oil of a second hydraulic pump 3 is combined with the pressure oil of the first hydraulic pump 2 through a combining directional control valve 19, and supplied to the boom cylinder 1. The pressure of the discharge pressure oil of the first hydraulic pump 2 is detected by a pressure sensor 21, and when the detected value is less than a prescribed value, and the detected value of the pressure sensor 26 is the combined switching pressure or more, the combining directional control valve 19 is held in a neutral position D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic working machine for civil engineering and construction such as a hydraulic excavator.

[0002]

2. Description of the Related Art For example, a hydraulic excavator is provided with a plurality of hydraulic actuators such as a boom cylinder, an arm cylinder, a bucket cylinder, a turning hydraulic motor, a traveling hydraulic motor, etc., and is used for operating the operating lever of each hydraulic actuator. Accordingly, pressure oil is supplied from the hydraulic pump to each hydraulic actuator through a directional valve provided corresponding to each hydraulic actuator, thereby operating each hydraulic actuator to perform various works. . In this case, generally, the plurality of hydraulic actuators are classified into, for example, two groups, a hydraulic pump is provided for each group, and hydraulic oil is supplied from the hydraulic pumps of each group to the hydraulic actuators of each group. I have to.

Of the hydraulic actuators, the boom cylinder and the arm cylinder, in particular, have a large load when the boom and the arm are lifted. Therefore, the boom cylinder and the arm cylinder are generally used. At the same time as supplying pressure oil from the hydraulic pump of the group to which pressure oil is supplied via the directional switching valve (first directional switching valve) in response to the operation of the operating lever, the merging direction separately provided from the hydraulic pumps of the other groups. It is supplied to the boom cylinder or the arm cylinder via the switching valve (second directional switching valve), in other words, the pressure oils of the two hydraulic pumps are combined and supplied to the boom cylinder or the arm cylinder. There is. By doing so, the boom cylinder and the arm cylinder can be quickly operated according to the operation of the operation lever even when the load is large.

By the way, when the hydraulic fluids of the two hydraulic pumps are merged and supplied to the hydraulic actuators such as the boom cylinder and the arm cylinder as described above, the merging is always performed according to the operation of the operation lever. Then, even if the operator operates the operation speed of the hydraulic actuator at a small speed, even if the operation amount of the operation lever is small, pressure oil is supplied from the two hydraulic pumps to the hydraulic actuator, and the operating speed of the hydraulic actuator is higher than necessary. Therefore, it becomes difficult to perform a desired slow speed operation.

Therefore, the inventors of the present application detect the operation amount of the operation lever or the operation amount of the first directional control valve corresponding to the operation amount, and the detected value is a relatively large lever. As for the operation amount, as described above, the pressure oils of the two hydraulic pumps are merged and supplied to the hydraulic actuator, and at the relatively small lever operation amount where the detection value is equal to or less than a predetermined amount, the second direction switching for the merging is performed. Attempting to supply the pressure oil to the hydraulic actuator only from the hydraulic pump corresponding to the first direction switching valve without holding the valve in the neutral state and supplying the pressure oil from the corresponding hydraulic pump to the hydraulic actuator. ing. By doing so, when the operation amount of the operation lever is small and a slight speed operation of the hydraulic actuator is required, the pressure oil is supplied to the hydraulic actuator from only one hydraulic pump, and the desired small speed operation is achieved. The operation can be performed.

However, it has been found by the study of the inventors of the present application that such a device causes the following problems.

That is, the means for detecting the operation amount of the operation lever or the operation amount of the first directional control valve corresponding to the operation amount (for example, a pressure sensor for detecting the pilot pressure of the first directional control valve) is provided. When a failure occurs, the detection value of the detection means may be equal to or more than the predetermined amount even when the operation lever is at the neutral position or the operation amount is sufficiently small. Then, in this case, the pressure oil is not supplied from the hydraulic pump corresponding to the first directional control valve to the hydraulic actuator, or the supply amount thereof is small, but the second oil for merging is used. The directional control valve operates, pressure oil is supplied to the hydraulic actuator from another hydraulic pump corresponding thereto, and the hydraulic actuator causes an operation contrary to the operator's intention.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned inconvenience, and detects a hydraulic actuator such as a boom cylinder or an arm cylinder for detecting an operation amount of an operation lever or an operation amount of a directional control valve corresponding to the operation amount. It is an object of the present invention to provide a hydraulic working machine capable of avoiding a situation where pressure oil is supplied to a hydraulic actuator against the intention of an operator and an unexpected operation of the hydraulic actuator is caused when a failure occurs in the means. And

[0009]

In order to achieve such an object, the present invention provides a first line for supplying pressure oil to a hydraulic actuator, which operates in response to an operation of an operating lever of the hydraulic actuator. A first hydraulic pump connected via a direction switching valve, a second hydraulic pump confluently connected to the conduit via a second direction switching valve, an operation amount of the operation lever or the operation amount And a first detection means for detecting the operation amount of the first directional control valve according to
When the detection value of the detection means of is less than a predetermined amount, the second
When the first hydraulic pump supplies pressure oil to the hydraulic actuator via the first directional control valve with the directional control valve in the neutral state, the detected value of the first detection means is equal to or greater than the predetermined amount. A hydraulic working machine that actuates the second directional switching valve, merges the pressure oils of both the first and second hydraulic pumps via the first and second directional switching valves, and supplies the hydraulic oil to the hydraulic actuator. In the second detection means for detecting the pressure of the discharge pressure oil of the first hydraulic pump, and the second detection means in a state where the detection value of the first detection means is equal to or more than the predetermined amount. And a merging prohibition means for holding the second directional control valve in a neutral state and prohibiting its operation when the detected value is less than a predetermined amount.

According to the present invention, when the operating lever is operated from the neutral position, at least the first hydraulic pump supplies pressure oil to the hydraulic actuator to operate the hydraulic actuator. , First
The pressure of the hydraulic oil discharged from the hydraulic pump is equal to or higher than a predetermined value. Therefore, when the detected value of the pressure of the discharge pressure oil of the first hydraulic pump detected by the second detection means is less than or equal to a predetermined amount, it is determined that the operation lever is operated at or near the neutral position. At that time, if the detection value of the first detection means is equal to or more than the predetermined amount, it can be determined that the first detection means is out of order. Therefore, when the detection value of the second detection unit is equal to or smaller than the predetermined amount in the state where the detection value of the first detection unit is equal to or larger than the predetermined amount,
The operation of the second directional control valve is prohibited, assuming that the failure of the first detection means has occurred. As a result, when the failure of the first detection means occurs, the second directional control valve does not operate, so that the pressure oil of the second hydraulic pump is not supplied to the hydraulic actuator. It is possible to avoid a situation in which the hydraulic oil is supplied to the hydraulic actuator against the intention of a person and an unexpected operation of the hydraulic actuator is caused.

In the hydraulic working machine according to the present invention, the hydraulic actuator is, for example, a boom cylinder or an arm cylinder, and in this case, the second directional control valve according to the detection value of the first detection means. It is preferable that the operation of is performed at least when the boom is raised by the boom cylinder or when the arm is raised by the arm cylinder.
Thereby, when the first detecting means is normal,
When the boom is lifted or the arm is lifted when the load of the boom cylinder or arm cylinder is large with a relatively large operation amount of the operation lever, the detection value of the first detection means being a predetermined amount or more, Pressure oil is supplied to the boom cylinder and the arm cylinder from both of the two hydraulic pumps, so that the boom cylinder and the arm cylinder can be quickly operated. It should be noted that, when the operation lever has a relatively small operation amount such that the detection value of the first detection means is equal to or less than a predetermined amount, pressure oil is supplied to the boom cylinder and the arm cylinder only from the first hydraulic pump, and the operation lever is operated. It is possible to perform fine speed operation according to the operation amount.

Further, the merging prohibition means is provided with a solenoid valve which is interposed in a pilot line connected to a pilot port of the second directional control valve so that pilot pressure in the line can be conducted or blocked. When the detected value of the first detecting means is equal to or more than the predetermined amount and the detected value of the second detecting means is equal to or less than the predetermined amount, the solenoid valve shuts off the pilot pressure in the pilot line. By holding it, the operation of the second directional control valve is prohibited.

With this, it is possible to easily inhibit the operation of the second directional control valve when the first detecting means has a failure with a simple structure.

[0014]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIGS. 1 is a hydraulic circuit diagram of essential parts of the hydraulic working machine according to the present embodiment, FIG. 2 is a diagram for explaining the operation of the hydraulic working machine of FIG. 1, and FIG. 3 is a diagram illustrating the operation of the hydraulic working machine of FIG. It is a flowchart for doing.

Referring to FIG. 1, the hydraulic working machine of this embodiment is, for example, a hydraulic excavator, in which 1,1 are a pair of boom cylinders (hydraulic actuators), and 2 and 3 are variable displacement type first hydraulic pressures. A pump and a second hydraulic pump, 4 is a pilot pump, 5 is a boom operation valve having a boom operation lever 6, and 7 is a controller configured by using a microcomputer or the like. Each pump 2, 3, 4
The engine is driven by an engine (not shown), and when the engine is driven, the pressure oil is sucked and discharged from the hydraulic oil tank 8. Also, the pair of boom cylinders 1, 1
The respective rod-side oil chambers 1a, 1a and the bottom-side oil chambers 1b, 1b are connected to each other, and the conduits 9, 10 are led from the rod-side oil chamber 1a and the bottom-side oil chamber 1b, respectively.

Although not shown, this hydraulic excavator includes an arm cylinder, a boom cylinder 1, and an arm cylinder.
Hydraulic actuators such as a bucket cylinder, a turning hydraulic motor, and left and right traveling hydraulic motors are provided, and an operating lever is provided corresponding to each hydraulic actuator (not shown).

Of the plurality of hydraulic actuators described above, the first hydraulic pump 2 is basically the boom cylinder 1,
1, for driving the bucket cylinder and the hydraulic motor for traveling on the right side, in the pipe line 11 led out from the discharge port of the first hydraulic pump 2, from the upstream side thereof,
A right-side traveling directional control valve 12, a bucket directional control valve 13, and a boom directional control valve 14 (first directional control valve) for controlling the operation of the hydraulic actuators are interposed. Similarly, the second hydraulic pump 3 is basically for driving the left traveling hydraulic motor, the turning hydraulic motor, and the arm cylinder.
A left side traveling directional control valve 16, a turning directional control valve 17, and an arm directional control valve 18 are provided in this order from the upstream side of the pipe line 15 led out of the discharge port.
Further, in the pipe line 15 on the second hydraulic pump 3 side, at a position between the turning direction switching valve 17 and the arm direction switching valve 18,
A boom merging direction switching valve 19 for appropriately merging the discharge pressure oil of the second hydraulic pump 3 with the discharge pressure oil of the first hydraulic pump 2 and supplying it to the boom cylinders 1, 1 as described later.
The (second directional control valve) is provided. Furthermore, the first
The boom direction switching valve 1 is provided in the pipeline 11 on the hydraulic pump 2 side.
An arm merging direction switching valve 20 for appropriately merging the discharge pressure oil of the first hydraulic pump 2 with the discharge pressure oil of the second hydraulic pump 3 and supplying the same to the arm cylinder at a position on the downstream side of 4. Has been done.

In the pipe line 11 on the first hydraulic pump 2 side, the first
Pressure sensor 2 for detecting the pressure of the discharge pressure oil of the hydraulic pump 2.
1 (second detecting means) is connected, and this pressure sensor converts the detected pressure of the pressure oil discharged from the first hydraulic pump 2 into an electronic signal and outputs it to the controller 7.

The boom direction switching valve 14 can be switched to three positions A, B and C, and its neutral position A is used.
Then, the pipe lines 9 and 10 led out from the boom cylinders 1 and 1 are shut off from the first hydraulic pump 2. Also,
At the switching position B, the bottom side oil chamber 1b of the boom cylinders 1, 1 is provided in the bypass pipe line 22 led from the pipe line 11 of the first hydraulic pump 2 between the traveling direction change valve 12 and the bucket direction change valve 13. The hydraulic fluid tank 8 is communicated with the hydraulic fluid tank 8 while the hydraulic fluid tank 8 is communicated with the hydraulic fluid tank 8. Further, at the switching position C, the conduit 10 communicating with the bottom side oil chamber 1b of the boom cylinders 1, 1 is communicated with the hydraulic oil tank 8 and the conduit 9 communicating with the rod side oil chamber 1a is communicated with the bypass conduit 22. Let

Therefore, when the boom directional control valve 14 is operated to the switching position B, the pressure oil discharged from the first hydraulic pump 2 flows through the pipeline 11, the bypass pipeline 21, the boom directional control valve 14 and the pipeline 10. It is supplied to the bottom side oil chamber 1b of the boom cylinders 1, 1 and the boom cylinders 1, 1 extend (at this time, a boom (not shown) rises). Further, when the boom direction switching valve 14 is operated to the switching position C, the pressure oil discharged from the first hydraulic pump 2 is transferred to the pipeline 11 and the bypass pipeline 2.
2 is supplied to the rod-side oil chamber 1a of the boom cylinders 1, 1 via the pipe 9 and the boom cylinders 1, 1 are shortened (at this time, a boom (not shown) descends).

The boom operation valve 5 for performing the switching operation of the boom directional control valve 14 is connected to the pipe line 23 led out from the discharge port of the pilot pump 4, and the boom directional control valve 14 is also connected. Are connected to the pilot port 14b on the switching position B side and the pilot port 14c on the switching position C side via pilot conduits 24 and 25, respectively.

The boom operation valve 5 is operated from the pressure oil discharged from the pilot pump 4 when the boom operation lever 6 is swung in the direction of arrow X in FIG. 1, for example.
The pilot pressure according to the operation amount of is generated in the pilot pipe line 24, and the pilot pressure is applied to the pilot port 14b of the boom directional control valve 14. At this time, the boom direction switching valve 14 operates toward the switching position B with an operation amount (a moving amount of a spool (not shown)) proportional to the pilot pressure applied to the pilot port 14b. Therefore, when the boom operation lever 6 is swung in the direction of the arrow X, the boom cylinders 1 and 1 extend and the boom (not shown) rises. Further, the boom operation valve 5 pilots a pilot pressure corresponding to the operation amount of the operation lever 6 from the discharge pressure oil of the pilot pump 4 when the boom operation lever 6 is rocked in the direction of the arrow Y in FIG. It is generated in the pipe line 25 and its pilot pressure is applied to the pilot port 14c of the boom directional control valve 14. At this time, the boom direction switching valve 14 operates toward the switching position C with an operation amount proportional to the pilot pressure applied to the pilot port 14c. Therefore, when the boom operation lever 6 is swung in the direction of the arrow Y, the boom cylinders 1 and 1 are shortened and the boom is lowered.

In the pilot conduit 24 on the side of the switching position B of the boom directional control valve 14, a pressure sensor 26 for detecting the pilot pressure applied to the pilot port 14b (first
The pressure sensor 26 converts the detected value of the pilot pressure into an electric signal and outputs the electric signal to the controller 7.
Output to In this case, the pilot pressure in the pilot conduit 24 depends on the operation amount of the boom operation lever 6 and the operation amount of the boom directional switching valve 14 toward the switching position B, and therefore the pilot pressure by the pressure sensor 26 is used. The detected value of indicates the operation amount of the boom operation lever 6 or the operation amount of the boom direction switching valve 14.

Although not described in detail or shown in the drawings, the right traveling directional control valve 12 and the bucket directional control valve 1 are provided.
3, left traveling direction switching valve 16, turning direction switching valve 17
The arm directional control valve 18 is the boom directional control valve 1.
As in the case of No. 4, it operates in response to the operation of an operation lever (not shown) corresponding to each of the switching valves 12, 13, 16, 17, and 18, and a right-side traveling hydraulic motor, a bucket cylinder, and a left-side traveling hydraulic pressure (not shown) are operated. A motor, a turning hydraulic motor, and an arm cylinder are operated.

Like the boom direction switching valve 14, the boom merging direction switching valve 19 can be switched to three positions D, E, F. At the neutral position D, the boom cylinder 1, The conduits 9 and 10 of 1 are shut off from the second hydraulic pump 2. Then, at the switching position E, the bypass pipe line 27 led out from the pipe line 15 of the second hydraulic pump 3 between the left traveling direction switching valve 16 and the turning direction switching valve 17.
Boom cylinder 1, 1 bottom side oil chamber 1b side pipeline 1
The hydraulic fluid tank 8 is communicated with the hydraulic fluid tank 8 while the hydraulic fluid tank 8 is communicated with the hydraulic fluid tank 28 and the hydraulic fluid tank 8 is fluidized with the hydraulic fluid tank 29. Further, at the switching position F, the merging conduit 28 on the bottom oil chamber 1b side of the boom cylinders 1, 1 is communicated with the hydraulic oil tank 8, and the merging conduit 29 on the rod side oil chamber 1a side is connected to the bypass conduit 22. Communicate with.

Therefore, as described above, in order to extend the boom cylinders 1, 1 (raise the boom), the first
With the hydraulic fluid being supplied from the hydraulic pump 2 to the bottom side oil chamber 1b of the boom cylinders 1 and 1 via the boom directional control valve 14, the boom merging directional control valve 19 is set to the switching position E.
When it is operated to, the pressure oil discharged from the second hydraulic pump 3 is discharged to the conduit 1
5, the pipeline 1 through the bypass pipeline 27 and the merging pipeline 18.
At 0, it joins the discharge pressure oil of the first hydraulic pump 2 and is supplied to the bottom side oil chamber 1b of the boom cylinders 1, 1 together with the discharge pressure oil of the first hydraulic pump 2.

In this way, the pilot port 19 of the boom merging direction switching valve 19 which applies a pilot pressure when the boom merging direction switching valve 19 is operated to the switching position E side.
A pilot pipe line 30 branched from the pipe line 23 of the pilot pump 4 is connected to e, and an electromagnetic proportional pressure reducing valve 31 (electromagnetic valve) whose energization is controlled by the controller 7 is interposed in the pilot pipe line 30. It is equipped. The electromagnetic proportional pressure reducing valve 31 is configured to allow conduction and interruption of pilot pressure for operating the boom merging direction switching valve 19 to the switching position E side by energization control by the controller 7, and in the conductive state, A pilot pressure obtained by reducing the pressure oil discharged from the pilot pump 4 in accordance with the amount of electricity supplied from the controller 7 is generated in the pilot conduit 30 and is applied to the pilot port 19e of the boom merging direction switching valve 19. Further, when the electromagnetic proportional pressure reducing valve 31 is shut off, the pilot line 30 is opened to the hydraulic oil tank 8 side to shut off the pilot pressure to the pilot port 19e of the boom merging direction switching valve 19.

In this case, the controller 7 controls the energization of the electromagnetic proportional pressure reducing valve 31 according to the detection values of the pressure sensors 21 and 26, as will be described later. The controller 7 constitutes a merging prohibition means 32 together with the electromagnetic proportional pressure reducing valve 31.

In this embodiment, the boom cylinder 1,
Only when the extension operation of 1 is performed (when the boom not shown is operated), the discharge pressure oils of the first and second hydraulic pumps 2 and 3 are combined and supplied to the bottom side oil chamber 1b of the boom cylinders 1 and 1. Therefore, no pilot pressure is applied to the pilot port 19f of the boom merging direction switching valve 19 on the switching position F side, and the boom merging direction switching valve 19 does not operate on the switching position F side. .

Although detailed description and illustration are omitted,
In the present embodiment, when the arm (not shown) is lifted, the arm direction switching valve 18 is operated in response to the operation of the arm so that the pressure oil is supplied to the arm cylinder from the second hydraulic pump 3 and the boom merging direction. Similarly to the switching valve 19, the arm merging direction switching valve 20 operates to supply pressure oil from the first hydraulic pump 2 to the arm cylinder.

Next, the operation of this embodiment will be described.

The operator of the hydraulic excavator of this embodiment operates the boom operating lever 6 to raise a boom (not shown).
1 is swung in the direction of the arrow X in FIG. 1, the boom operation valve 5 generates pilot pressure from the discharge pressure oil of the pilot pump 4 in the pilot conduit 24 according to the operation amount of the boom operation lever 6, and Pilot pressure is applied to the pilot port 14b of the boom direction switching valve 14. As a result, the boom direction switching valve 14 is operated toward the switching position B with an operation amount corresponding to the operation amount of the boom operation lever 6,
The discharge pressure oil of the first hydraulic pump 2 is the direction switching valve 14 for the boom.
Is supplied to the bottom side oil chamber 1b of the boom cylinders 1, 1 and the boom cylinders 1, 1 extend to raise the boom. At this time, the pilot pressure applied to the pilot port 14b of the boom directional control valve 14 is detected by the pressure sensor 25 and applied to the controller 7. In this case, the detection value of the pressure sensor 25 changes according to the operation amount of the boom operation lever 6 as shown by the solid line a in FIG.

Thus, when the boom is raised, the pressure sensor 2
The controller 7 to which the detection value of 5 is given determines whether or not the detection value exceeds a predetermined boom merging switching pressure Pk as shown in FIG. 2, in other words, the operation amount of the boom operation lever 6 is It is successively monitored whether or not the operation amount Sk corresponding to the boom merging switching pressure Pk is exceeded and a large operation is performed (STEP 1 in FIG. 3). Then, the controller 7 determines that the detection value of the pressure sensor 25 is the boom merging switching pressure P.
In a state where k is not exceeded, in other words, in a state where the operation amount of the boom operation lever 6 is a relatively small operation amount equal to or less than the operation amount Sk, the boom merging direction switching valve 19
The electromagnetic proportional pressure-reducing valve 31 is controlled so that is held at the neutral position D (STEP 2 in FIG. 3). Specifically, the controller 7 does not energize the electromagnetic proportional pressure reducing valve 31 and turns off the electromagnetic proportional pressure reducing valve 31, so that the pilot pressure is not applied to the pilot port 19e of the boom merging direction switching valve 19. Then, the boom merging direction switching valve 19
Is held in the neutral position D.

Therefore, when the operation amount of the boom operation lever 6 is a relatively small operation amount equal to or less than the operation amount Sk, the bottom side oil chamber 1b of the boom cylinders 1, 1 receives pressure oil only from the first hydraulic pump 2. Is supplied to the boom cylinder 1, 1
The decompression operation is performed. As a result, when the operation amount of the boom operation lever 6 is a relatively small operation amount equal to or less than the operation amount Sk, the operator can raise the boom (not shown) at a very low speed.

On the other hand, the controller 7 uses the STEP of FIG.
1, the detected value of the pressure sensor 25 is the boom merging switching pressure Pk.
In other words, in other words, when the operation amount of the boom operation lever 6 exceeds the operation amount Sk and becomes a relatively large operation amount, the pressure of the discharge pressure oil of the first hydraulic pump 2 is indicated. It is determined whether or not the detection value of the pressure sensor 21 is equal to or higher than a predetermined value (for example, the minimum pressure required to raise the boom) (STEP 3 in FIG. 3).
In this case, when the boom (not shown) is being raised by operating the boom operation lever 6, the detection value of the pressure sensor 21 is equal to or higher than the predetermined value. In this case, the controller 7 The boom merging direction switching valve 19 is operated toward the switching position E by an operation amount corresponding to the detection value of the pressure sensor 25, in other words, an operation amount corresponding to the operation amount of the operation lever 6 for the boom. The electromagnetic proportional pressure reducing valve 31 is controlled so as to be operated to the switching position E side with (Fig. 3
STEP 4). Specifically, the controller 7 energizes the electromagnetic proportional pressure reducing valve 31 with an energizing amount according to the detection value of the pressure sensor 25, and the electromagnetic proportional pressure reducing valve 31 causes the pressure sensor 2 to operate.
The pilot pressure according to the detected value of 5
The pilot pressure is applied to the pilot port 19e of the boom merging direction switching valve 19.

As a result, the discharge pressure oil of the second hydraulic pump 3 merges with the discharge pressure oil of the first hydraulic pump 2 via the boom merging direction switching valve 19, and the bottom side oil chamber 1b of the boom cylinders 1, 1 is merged. Is supplied to. Therefore, when the operation amount of the boom operation lever 6 becomes a relatively large operation amount, the two hydraulic pumps 2, 2 are provided in the bottom side oil chamber 1b of the boom cylinder 1, 1.
The pressure oil is supplied from 3 and the boom can be quickly raised in accordance with the operation of the boom operation lever 6 so that the load on the boom cylinders 1 and 1 becomes large. in this case,
The flow rate of the pressure oil supplied from the second hydraulic pump 3 to the boom cylinders 1, 1 increases as the operation amount of the boom operation lever 6 increases as indicated by the solid line b in FIG.

The operation described above is an operation when the pressure sensor 26 is normal, but when the pressure sensor 26 fails, the pressure is not applied even though the boom operation lever 6 is not operated. The detection value of the sensor 26 may exceed the boom merging switching pressure Pk.

In this case, in STEP 3 of FIG. 3, if the boom operation lever 6 is not operated, the boom direction switching valve 14 is held at the neutral position A, and therefore,
Pressure sensor 2 indicating the pressure of the discharge pressure oil of the first hydraulic pump 2.
The detected value of 1 does not reach the predetermined value. That is, in STEP 1 of FIG. 3, the detection value of the pressure sensor 26 exceeds the boom merging switching pressure Pk, and in STEP 3, the pressure sensor 21
If the detected value of the pressure sensor 2 does not reach the predetermined value, the pressure sensor 2
6 can be determined to be out of order, and in this case, the controller 7 electromagnetically proportionally holds the boom merging direction switching valve 19 at the neutral position D regardless of the detection value of the pressure sensor 26. The pressure reducing valve 31 is controlled (S in FIG. 3).
TEP2). Specifically, the controller 7 does not energize the electromagnetic proportional pressure reducing valve 31 and turns off the electromagnetic proportional pressure reducing valve 31, so that the pilot pressure is not applied to the pilot port 19e of the boom merging direction switching valve 19. Then, the boom merging direction switching valve 19 is held at the neutral position D, and the operation of the boom merging direction switching valve 19 to the switching position E side is prohibited.

Therefore, when the pressure sensor 26 fails as described above, the boom merging direction switching valve 19 does not operate to the switching position E side, and the boom operating lever 6 is held at the neutral position. However, it is possible to prevent the operator from unexpectedly operating such that the hydraulic oil is supplied from the second hydraulic pump 3 to the bottom side oil chamber 1b of the boom cylinders 1 and 1 and the boom (not shown) rises. be able to.

When the pressure sensor 26 fails and the detected value is always lower than the boom merging switching pressure Pk, the boom merging direction switching valve 19 is held at the neutral position D as described above. Therefore, the hydraulic oil is not supplied from the second hydraulic pump 3 to the boom cylinders 1 and 1, and accordingly, the boom raising operation contrary to the operator's intention does not occur.

As described above, in the hydraulic excavator according to the present embodiment, the boom cylinders 1 and 1 receive the first force when the boom is raised.
A pilot for switching between an operation of supplying pressure oil from both the hydraulic pump 2 and the second hydraulic pump 3 and an operation of supplying pressure oil only from the first hydraulic pump 2 in accordance with the operation amount of the boom operation lever 6. Even if the pressure sensor 26 that detects the pressure in the pipeline 24 is out of order, it is possible to avoid a situation in which the boom rises against the operator's intention.

The above-described operation is similarly performed when the arm (not shown) is operated.

In this embodiment, pressure oil is supplied to the boom cylinders 1, 1 from both the first and second hydraulic pumps 2 and 3 according to the operation amount of the boom operation lever 6 when the boom is raised. However, it is of course possible to perform such an operation even when the boom is lowered. In this case, for example, a pressure sensor is also provided on the side of the pilot pipe 25 of the boom direction switching valve 14,
The pilot pressure in the pilot line 25 is detected according to the operation amount of the boom operation lever 6 toward the arrow Y side.
According to the detected value, the boom merging direction switching valve 19 may be operated to the switching position F side, as in the case of raising the boom.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a main part of a hydraulic working machine according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the hydraulic working machine in FIG.

FIG. 3 is a flowchart for explaining the operation of the hydraulic working machine in FIG.

[Explanation of symbols]

1 ... Boom cylinder (hydraulic actuator), 2 ... 1st
Hydraulic pump, 3 ... 2nd hydraulic pump, 14 ... Boom directional control valve (1st directional control valve), 19 ... Boom merging directional control valve (2nd directional control valve), 21 ... Pressure sensor (2nd)
Detection means), 26 ... Pressure sensor (first detection means),
32 ... Merging prohibition means, 31 ... Electromagnetic proportional pressure reducing valve (solenoid valve).

Claims (3)

[Claims] 1. A first hydraulic pump connected to a pipeline for supplying pressure oil to a hydraulic actuator via a first directional switching valve that operates in response to an operation of an operating lever of the hydraulic actuator. , A second hydraulic pump confluently connected to the conduit via a second directional control valve, and an operation amount of the operation lever or an operation amount of the first directional control valve according to the operation amount is detected. And a first detecting means for performing a first direction switching by the first hydraulic pump when the second direction switching valve is in a neutral state when the detection value of the first detecting means is less than or equal to a predetermined amount. Pressure oil is supplied to the hydraulic actuator via a valve, and when the detection value of the first detecting means is equal to or more than a predetermined amount, the second directional control valve is operated to operate the first directional control valve.
In the hydraulic working machine that supplies the pressure oils of both the first and second hydraulic pumps to the hydraulic actuator by merging them via the first and second direction switching valves, respectively, the pressure of the discharge pressure oil of the first hydraulic pump And a second detection means for detecting the second detection means and a detection value of the second detection means is equal to or more than the predetermined amount when the detection value of the first detection means is equal to or more than the predetermined amount. And a merging prohibition means for prohibiting the operation of the directional control valve in a neutral state. 2. The hydraulic actuator is a boom cylinder or an arm cylinder, and the operation of the second directional control valve according to the detection value of the first detection means is performed at least when the boom is raised by the boom cylinder. Alternatively, the hydraulic working machine according to claim 1, which is performed when the arm is raised by the arm cylinder. 3. The merging prohibition means comprises a solenoid valve which is interposed in a pilot line connected to a pilot port of the second directional control valve so that pilot pressure in the line can be conducted and blocked. When the detected value of the first detecting means is equal to or more than the predetermined amount and the detected value of the second detecting means is equal to or less than the predetermined amount, the solenoid valve shuts off the pilot pressure in the pilot line. The second by holding
3. The hydraulic working machine according to claim 1 or 2, wherein the operation of the directional control valve is prohibited.