JPH09195323A - Operating position detector of selector valve in hydraulic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to detect whether at least a desired selector valve has been changed over or not so as to detect switching state of the selector valve changing over the flow of pressure oil of a main hydraulic circuit by detecting pilot pressure on the upper stream side or the lower stream side of a pilot hydraulic circuit connecting switch valves in series provided to a plurality of selector valves in succession. SOLUTION: A pressure sensor 40 for detecting pilot pressure on the direct lower stream of a throttle valve 25 provided to the upper stream of a right traveling directional selector valve 11 in a pilot hydraulic circuit connecting pilot oil switch valves provided to both right and left traveling directional selector valves 10 and 11 in series is provided. An opening is used as a throttle opening when the main body of the left traveling directional selector valve 10 of the pilot oil switch valve provided to the left traveling directional selector valve 10 has been switched to both right and left operating positions, and when the left traveling directional selector valve 10 has been switch alone, the pressure sensor 40 detects pilot pressure with approximately half of discharge pressure of a pilot pump 56.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of an operating position detecting device for detecting an operating position of a switching valve which is preferably applicable to an actuator driving hydraulic circuit of a hydraulic excavator.

[0002]

2. Description of the Related Art A hydraulic excavator has left and right traveling trucks,
It is equipped with a working machine composed of multiple working elements such as a swivel, a boom, an arm, and a bucket.The actuators that drive these are operated by a directional switching valve provided in each pressure oil supply / discharge circuit. The direction and flow rate can be switched. Usually, the traveling directional control valve and the working machine directional control valve are often configured with two hydraulic circuits, each receiving pressure oil from two hydraulic pressure sources. If the hydraulic circuit of each system is configured with a parallel circuit, the circuit configuration will be simple, and more than one actuator can be driven simultaneously, but the operating pressure of each actuator will differ, and the valve opening / closing of other directional control valves will In some cases, the desired control could not be performed due to the influence, and the driving could not be performed.

Therefore, it has been proposed to ensure the independence of the operation of each actuator by using the above hydraulic circuit as a tandem connection circuit. However, even in this circuit configuration, there are few kinds of compound operations that can operate, and it is not always sufficient. It had no practical utility. In order to make up for such incompleteness of the prior art, as disclosed in Japanese Examined Patent Publication No. 16416/1990, the applicant of the present invention has found that the directional control valve for booms, etc., located upstream of the directional control valve for left travel. A bypass circuit for supplying pressure oil from the second hydraulic pump to the inflow chamber of the left traveling directional switching valve when at least one directional switching valve belonging to the first valve group of the above is operated, and is connected in tandem. The pressure oil from the first hydraulic pump is discharged to the left via a bypass circuit that is connected to the first hydraulic circuit at an upstream position of the boom direction switching valve and the arm direction switching valve, and a throttle valve is interposed in the middle. An invention of a hydraulic drive system that supplies the inflow chamber of a traveling direction switching valve has been proposed.

Thus, it is possible to prevent the excessive pressure of the hydraulic pressure due to the inertia of the swivel base from being released by the pressure release valve during the combined operation of the swing and the boom, the arm or the travel, and further, the boom-arm-bucket and the travel-boom-arm. , Turning-running-
It is possible to perform three combined operations of the boom and four combined operations of swing-boom-arm-bucket. As described above, since the traveling operation and the boom operation or the arm operation can be independently performed at the same time by the above-described improved technology, for example, the boom is raised to the dumping position while traveling, or the arm is retracted to escape the wetland. You can

[0005]

In the above-described two-system hydraulic circuit configuration, the boom directional control valve and the arm directional control valve are normally connected to both systems, so that when either of these is switched. The outflow of pressure oil to the central bypass circuit reaching the direction switching valve downstream of the direction switching valve is blocked. The opening amounts of the spools of the direction switching valves are set so that the operation of shutting off the pressure oil to the central bypass circuit can be performed by a fine operation of the operating lever that switches the boom and arm direction switching valves. Therefore, when the boom or arm operation lever is finely operated, the corresponding directional switching valves of both systems that are switched by the operation of the operation lever are interlocked and switched, and the outflow of pressure oil to the downstream side. Be cut off. In such a case, the first and second
The pressure oil discharged from the hydraulic pump flows into the traveling motor when the traveling direction switching valve is switched, and flows into the pressure relief valve when not.

[0006] By the way, although it is a rare operation in a hydraulic excavator, there is a case where a mud-removing work is performed in which the mud adhered to the running crawler is shaken off. For example, if you want to shake off mud that has adhered to the left track, turn the implement to the left to position the bucket on the side of the left track, then lower the boom to ground the bucket and then By lowering it, the running track on the left can be floated in the air. Then, by rotating the left traveling motor at high speed, the mud adhered to the left traveling crawler is shaken off.

When such mud shunting work is performed, the boom operation is performed as a fine operation, the left traveling operation is almost the maximum operation, and the right traveling operation is a non-operation. When the operation lever is operated in this manner, the discharge oil that has flowed out of the first hydraulic pump into the first hydraulic circuit is closed at the boom directional control valve position in the central bypass circuit. Flow into the left traveling directional control valve via the bypass bypass circuit. On the other hand, the discharge oil that has flowed from the second hydraulic pump to the second hydraulic circuit is restricted from flowing out to the downstream at the position of the boom direction switching valve in the central bypass circuit, but is merged with the boom direction switching valve. Since the communication valve provided in the bypass circuit opens, a large amount of pressure oil flows into the left travel direction switching valve via the merge bypass circuit.

In this way, the pressure oil discharged from the first and second hydraulic pumps intensively flows into the left travel direction switching valve, while the left travel motor is almost in a no-load state. The running motor causes unexpected over-rotation, causing the mud adhered to the running track to scatter violently,
It accelerates the deterioration of the left drive motor. Since such a problem occurs only when the left traveling lever and the boom or arm operation lever are operated, at least these operation levers are provided with a rotation sensor or can be switched by operating these operation levers. A pressure sensor that detects the pressure of the pilot oil flowing into the pilot chamber of the directional control valve is provided.When these sensors detect that the above situation has been reached, the flow rate of the pilot oil flowing into the left travel directional control valve is adjusted. Although it should be limited, at least three rotation sensors or three pressure sensors and a high-pressure selection valve must be newly provided, which complicates the drive mechanism and increases the manufacturing cost.

[0009]

[Problems to be Solved by the Invention]
No. 17387 discloses an on / off valve for pilot oil that flows in series when the boom and arm directional control valves and the left and right directional control valves are in their neutral positions. By detecting the pilot pressure on the pilot hydraulic pressure source side through the throttle valve connected in series, the switching state of the working machine direction switching valve and the traveling direction switching valve is recognized, and the maximum rotation speed of the prime mover is recognized according to this recognition. An invention of a construction machine in which the maximum tilt angle of a variable displacement hydraulic pump is controlled is disclosed.

Therefore, even if this technique is applied to the above-mentioned conventional technique to determine whether or not the left traveling direction switching valve is switched, for example, the upstream side of the left and right traveling direction switching valves connected in series is determined. Since the pilot pressure immediately downstream of the throttle valve provided in the pilot hydraulic circuit is detected, it is possible to determine whether the directional switching valve for traveling has been switched or not, but whichever directional switching valve for traveling is switched. It cannot be determined whether or not it has been done. In this way, the present invention switches the flow of pressure oil in the main hydraulic circuit by detecting the pilot pressure upstream or downstream of the pilot hydraulic circuit that connects the on-off valves that are connected to the plurality of switching valves in series. An object of the present invention is to provide an operating position detection device for a switching valve of a hydraulic circuit, which is capable of detecting at least whether or not a desired switching valve has been switched, in which the switching state of the switching valve is detected.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a throttle opening for an on-off valve attached when at least one valve of a switching valve body is switched to an operating position, Preferably, the throttle valve is connected upstream of the switching valve connected to the most upstream of the pilot hydraulic circuit, and the operation of the switching valve is detected by detecting the pilot pressure between the switching valve and the throttle valve. The throttle valve is connected to the downstream side of the switching valve connected to the most downstream of the pilot hydraulic circuit, and the throttle valve is detected by detecting the pilot pressure between the switching valve and the throttle valve. The operation position of the switching valve is detected. When the valve of the switching valve body is switched to the operating position, there are a plurality of switching valves in the hydraulic circuit that have the opening / closing valves attached to them, and the opening amounts of the opening / closing valves are different from each other. It may be one.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The switching valve of the hydraulic circuit according to the present invention may be any plurality of switching valves including a directional switching valve.
In the following description, in order to simplify the description, a description will be given of a hydraulic excavator in which the switching states of two directional switching valves are detected. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a hydraulic circuit diagram of a main part of a hydraulic excavator capable of detecting that one directional switching valve has been switched to an operating position. In the figure,
Reference numerals 1 and 2 are variable displacement first and second hydraulic pumps, 3 is a swing motor, 4 and 5 are left and right traveling motors, 6 is a boom cylinder, 7 is an arm cylinder, and 9 is a swing direction switching valve. , 11 left and right traveling direction switching valves, 12 boom direction switching valves, 13a and 13b first and second arm direction switching valves, 17 oil tank, 20 first and second hydraulic pumps 1, a prime mover connected to 1, 2, a throttle valve provided in a pilot line t ₁₃ on the upstream side of the right traveling direction switching valve 11, 35 a controller (CNT) for controlling a hydraulic system, 40 a right A pressure sensor for detecting the pilot pressure P in the pilot line t ₁₃ between the traveling direction switching valve 11 and the throttle valve 25, and 56 is a pilot pump.

As shown in the figure, this hydraulic circuit is
A first hydraulic system and a right traveling system in which the turning direction switching valve 9, the first arm direction switching valve 13a, and the left traveling direction switching valve 10 are connected to the second hydraulic pumps 1 and 2 from the upstream side, respectively. Direction switching valve 11, boom direction switching valve 12, second
The second hydraulic system to which the arm direction switching valve 13b is connected, and although not shown in the first and second hydraulic systems, they are respectively connected in a tandem circuit. In addition, the hydraulic pressure display symbol of each direction switching valve of the main hydraulic circuit,
The pilot hydraulic circuit for detecting the switching operation of the directional control valve for the working machine, the actuator outside the hydraulic excavator, and the drive circuit thereof are not shown.

In this hydraulic circuit, the pilot pump 56
Is discharged to the right traveling direction switching valve 11 via the throttle valve 25 through the pilot pipe line t ₁₃ . The pilot oil on-off valve provided in the right traveling direction switching valve 11 is fully opened when the spool is in the neutral position and fully closed when the spool is in another switching position. The pilot oil flowing out of the right traveling direction switching valve 11 is guided to the left traveling direction switching valve 10 through the pilot pipe line t ₁₂ . The on-off valve for pilot oil provided in the left traveling direction switching valve 10 is fully opened when the spool is in the neutral position and is half-opened when the spool is in another switching position. The pilot oil flowing out from the left traveling direction switching valve 10 is guided to the oil tank 17 through the pilot pipe line t ₁₁ .

Under such a pilot hydraulic circuit configuration, the pressure detected by the pressure sensor 40 is as follows by the switching operation of the left and right traveling direction switching valves 10 and 11. First, because when the spool of the left and right of the travel direction switch valves 10, 11 are in their neutral position their off valve are both fully opened, the low pressure P _l is approximately equal to the tank pressure. Next, when the spool position of the right traveling direction switching valve 11 is in the neutral position and the spool of the left traveling direction switching valve 10 is in the left and right operating positions, the opening / closing valve of the right traveling direction switching valve 11 is fully opened and left. Since the spool opening of the traveling direction switching valve 10 is half open, the pressure detected by the pressure sensor 40 is medium pressure.
When the throttle amounts of the throttle valve 25 and the opening / closing valves of the left traveling direction switching valve 10 are equal, the discharge pressure P _P of the pilot pump 56 is half, that is, P _P / 2. Further, when the spool position of the right traveling direction switching valve 11 is at the left and right operating positions, the spool opening of the right traveling direction switching valve 11 is fully closed regardless of the spool position of the left traveling direction switching valve 10. Therefore, the pressure detected by the pressure sensor 40 is approximately the discharge pressure P _P of the pilot pump 56.

As described above, in the hydraulic circuit shown in FIG. 1, by observing the pressure detected by the pressure sensor 40, the spool position of the right traveling direction switching valve 11 is at the neutral position,
Moreover, it is possible to surely recognize whether the spool position of the left traveling directional control valve 10 is in the neutral position or in the left and right operating positions, and moreover, it can be realized by a simple and inexpensive hydraulic circuit. Further, if the throttle valves 25 and the opening / closing valves of the left traveling directional switching valve 10 are equal in throttle amount, the left and right traveling directional switching valves 10, 11 which are not affected by the temperature change of the pilot oil or the flow rate change of the pilot hydraulic circuit. The spool position can be detected. In such a case, instead of the pressure sensor 40 capable of continuously detecting the pressure value, two pressure switches are used to detect that only the left traveling direction switching valve 10 is in the left and right operating positions. You can

FIG. 2 is a hydraulic circuit diagram in which two pressure switches are used so that it is possible to recognize that the spool position of only the left traveling direction switching valve 10 is in the left and right operating positions.
In the figure, 41 is a first pressure switch that opens and closes at an operating pressure P _{1 in} which the pilot pressure P in the pilot line t ₁₃ downstream of the throttle valve 25 is smaller than P _P / 2, and 42 is the pilot pressure P P _P / 2 is a second pressure switch which opens and closes at a greater operating pressure P _2, the same reference numerals as those in the hydraulic circuit shown in FIG. 1 indicates that the same circuit components. The same applies to the following description. When both the first and second pressure switches 41 and 42 are open, the pilot pressure P in the pilot line t ₁₃ downstream of the throttle valve 25 is low pressure P _l , the first pressure switch 41 is closed, and the second pressure switch 41 is closed. When the pressure switch 42 is open, the pilot pressure P is the intermediate pressure P _P / 2, and when both the first and second pressure switches 41 and 42 are closed, the pilot pressure P is the discharge pressure P _P of the pilot pump 56. I understand.

In the above hydraulic circuit, the pressure sensor and the pressure switch are provided in the pilot pipe line t ₁₃ on the upstream side of the right traveling directional control valve 11, but they are not necessarily provided in this position. In FIG. 3, the positions of the pilot pump 56 and the oil tank 17 of the pilot hydraulic circuit are reversed, and the throttle valve 2
5 is provided in the pilot line t ₁₁ on the downstream side of the right travel direction switching valve 11, and the pressure sensor 40 is provided on the upstream side of the throttle valve 25.
It shows a hydraulic circuit provided with. In this case, the pressure detected by the pressure sensor 40 provided on the upstream side of the throttle valve 25 is substantially the discharge pressure P of the pilot pump 56 when the spools of the left and right traveling direction switching valves 10 and 11 are both in the neutral position.
_P , when the spool of the right traveling direction switching valve 11 is in the neutral position, and the spool of the left traveling direction switching valve 10 is in the left and right operating positions, the intermediate pressure P _P / 2, the spool of the right traveling direction switching valve 11 is When in the left and right operating positions, the low pressure P ₁ is applied.

In the hydraulic circuits shown in FIGS. 1 to 3, when the spool of the right traveling directional switching valve 11 is in the left and right operating positions, the opening / closing valve is fully closed, and the left traveling directional switching valve 10 is opened / closed. Since the pressure sensor and the pressure switch detect the pressure regardless of the operating state, the switching state of the right traveling direction switching valve 11 alone to the left and right operating positions cannot be detected. Therefore,
Open the opening of the pilot oil opening / closing valve at the left and right operating positions of the spool of the right traveling direction switching valve 11 to the left traveling direction switching valve 1.
By setting the throttle opening different from the opening amount of the opening / closing valve of 0, it becomes possible to detect the switching state of the right traveling direction switching valve 11 alone to the left and right operating positions.

FIG. 4 shows the left and right direction switching valves 10, 11 for traveling.
FIG. 3 is a hydraulic circuit diagram of a hydraulic excavator in which the openings at the left and right operating positions of the on-off valves that are connected to each other are both throttle openings. In this case, the throttle opening amount of the opening / closing valve provided in the left traveling direction switching valve 10 is set larger than the throttle opening amount of the opening / closing valve provided in the right traveling direction switching valve 11. In this hydraulic circuit, when the spools of the left and right traveling direction switching valves 10 and 11 are both in the neutral position, the pressure detected by the pressure sensor 40 is a low pressure P _l that is substantially equal to the tank pressure, and the left traveling direction switching valve 10 has the same pressure. When the spool is in the left and right operating positions and the spool of the right traveling directional control valve 11 is in the neutral position, the semi-low pressure P is a little low.
_hl , when the spool of the left traveling direction switching valve 10 is in the neutral position and the spool of the right traveling direction switching valve 11 is in the left and right operating positions, the semi-high pressure P _{hh with} a slightly higher pressure, the left and right traveling direction switching When both spools of the valves 10 and 11 are in the left and right operating positions, the high pressure P _h is close to the discharge pressure P _P of the pilot pump 56.

Thus, the left and right traveling direction switching valves 1
By changing the opening amounts of the throttle openings of the on-off valves that are connected to 0 and 11, the left and right traveling direction switching valves 10 and 11 can be changed.
It is possible to detect the switching position of each spool. If a highly accurate pressure sensor is provided, and preferably a pressure compensating valve and a temperature compensating circuit are further provided, it is possible to detect the respective switching positions of the spools of many switching valves connected in series. Next, referring to the drawings, FIG.
An embodiment of the present invention in which the hydraulic circuit shown in FIG.

[0022]

FIG. 5 is a hydraulic circuit diagram of a hydraulic excavator including first and second hydraulic systems for driving an actuator according to an embodiment of the present invention. In the figure, 8 is a bucket cylinder, 12a and 12b are first and second boom direction switching valves, 14 is a bucket direction switching valve, 16 is a preliminary direction switching valve, 18 is a swiveling operation portion, and 43 is a pressure. sensor,
51, 52, 53, 54 and 55 are operation units for arm, left traveling, right traveling, boom and bucket, respectively.
Reference numeral 58 is a throttle valve. As shown in the figure, the discharged oil flowing out from the first hydraulic pump 1 flows through the central bypass conduit T ₁₁ and the bypass bypass conduit T ₁₂ and is formed by a first direction switching valve group described below. It flows into the hydraulic circuit I. From the upstream side, the first hydraulic circuit I includes a turning direction switching valve 9, a first arm direction switching valve 13a, a first boom direction switching valve 12a,
The preliminary direction switching valve 16 and the left traveling direction switching valve 10 are connected in tandem, and the turning motor 3, the arm cylinder 7, the boom cylinder 6 and the left traveling motor 4 are placed in each of the outflow-side supply / discharge chambers. Each is connected.

On the other hand, the discharged oil flowing out from the second hydraulic pump 2 flows through the central bypass pipe line T ₂₁ and the bypass bypass pipe line T ₂₂ and is constituted by a second hydraulic circuit composed of each directional switching valve group described below. Inflow into II. From the upstream side, the second hydraulic circuit II includes a right traveling direction switching valve 11, a bucket direction switching valve 14, and a second hydraulic circuit II.
The boom direction switching valve 12b and the second arm direction switching valve 13b are connected to each other, and the right traveling motor 5, the bucket cylinder 8, the boom cylinder 6, and the arm cylinder 7 are respectively provided in the outflow-side supply / discharge chambers. It is connected. Further, a confluence conduit T ₃ reaching the inflow chamber of the left traveling directional control valve 10 connected to the end of the first hydraulic circuit I is connected to the inflow conduit to the second hydraulic circuit II. A communication valve 26 is provided on the way through a check valve. The communication valve 26 is composed of an electromagnetic valve, which is normally closed and is opened when the drive signal γ is input.

The oil discharged from the pilot pump 56 flows out into the _two pilot lines t ₁ and t ₂ .
The pilot oil that has flowed out to the pilot line t ₁ has a turning operation portion 18, an arm operation portion 51, a left traveling operation portion 52,
It flows into the right traveling operation unit 53, the boom operation unit 54, and the bucket operation unit 55. Each of these operation units 18, 5
When the operation levers 1 to 55 are operated, the pilot oil flows out into the outflow chamber of the pilot switching valve, and a to l are shown in FIG.
As shown by the connection relationship in FIG. 1, the corresponding turning direction switching valve 9, the first and second arm direction switching valves 13a, 1
3b, left traveling direction switching valve 10, right traveling direction switching valve 1
The spools flow into the pilot receiving portions of the first, second, and second boom direction switching valves 12a and 12b and the bucket direction switching valve 14 to move the respective spools to the operating positions.

The pilot oil flowing out to the pilot pipe line t ₂ flows out to the pilot pipe lines t ₁₃ and t ₂₃ via the throttle valves 25 and 58, respectively. Pressure sensors 40 and 43 are connected to the pilot conduits t ₁₃ and t ₂₃ , respectively, and detect pilot pressures downstream of the throttle valves 25 and 58, respectively. The detection outputs α and β of the pressure sensors 40 and 43 are CNT.
35 is output. The pilot pipeline t ₁₃ is connected to the pilot pipeline t ₁₂ via the pilot oil opening / closing valve of the right traveling directional switching valve 11, and the pilot pipeline t ₁₂ is the pilot oil of the left traveling directional switching valve 10. Is connected to the pilot line t ₁₁ via an opening / closing valve for That is, the open / close valves for pilot oil of the left and right traveling direction switching valves 10, 11 are connected in series. As described above, the operating modes of the pilot oil opening / closing valves of the left and right traveling direction switching valves 10 and 11 are the same as those shown in FIG.

The pilot pipe line t ₂₃ passes through the bucket directional switching valve 14, the second boom directional switching valve 12b and the second arm directional switching valve 13b through the pilot oil opening / closing valve for pilot oil line t _22. Are linked to. The pilot pipe line t ₂₂ is provided with the pilot pipe through the turning direction switching valve 9, the first arm direction switching valve 13a, the first boom direction switching valve 12a, and the pilot direction switching valve 16 for the pilot oil. It is connected to the road t ₂₁ . That is, all the opening / closing valves for pilot oil of the direction switching valve for controlling the flow of pressure oil to the actuator of the working machine are connected in series.

Next, the operation of this embodiment will be described. When the hydraulic excavator travels, the left and right traveling direction switching valves 10 and 11 are respectively moved to the right or left by the pilot oil flowing out from the pilot switching valve as the driver operates the left and right traveling operation units 52 and 53. Of the first hydraulic pump 1 is discharged to the left traveling motor 4 through the oil chamber of the left traveling direction switching valve 10 via the central bypass pipe line T ₁₁ . The oil discharged from the hydraulic pump 2 of No. 2 directly flows into the right traveling motor 5 through the oil chamber of the right traveling direction switching valve 11 to rotate them. At this time, the on / off valves for pilot oil of the left and right traveling direction switching valves 10, 11 are also switched to the operating position, and the left traveling direction switching valve 10 is half-opened.
Since the right travel direction switching valve 11 is fully closed, the pilot pressure in the pilot conduit t ₁₃ becomes high pressure P _h , and the pressure sensor 40 outputs the detection output α of H.

On the other hand, since the actuator for driving the working machine is not driven, the direction switching valves 9 and 12 of these actuators are not driven.
Since the spools a, 12b, 13a, 13b, 14 and 16 are in the neutral position, and the opening / closing valves for these pilot oils are all fully opened, the detection output β of the pressure sensor 43 becomes L. When the detection output β is L, the CNT 35 does not output the drive signal γ = H, so the communication valve 26 is closed, and therefore the left and right traveling motors 4 and 5 are independent of each other in the first and second hydraulic pumps 1. , 2 are driven by the discharged oil.

Next, the operation of the hydraulic excavator when performing a combined operation of the traveling operation and the working operation of the working machine will be described. In this case, any one of the turning direction switching valve 9, the first arm direction switching valve 13a, and the first boom direction switching valve 12a of the first hydraulic circuit I is switched to the operating position. The discharged oil flowing out from the first hydraulic pump 1 does not flow into the left traveling motor 4. However, when the actuator for driving the working machine is driven, as described above, the opening / closing valve for pilot oil of the directional switching valve closes, so the detection output β of the pressure sensor 43 becomes H, and the drive signal γ = from the CNT 35. H is output and the communication valve 26 opens. Therefore,
The discharged oil flowing out from the second hydraulic pump 2 flows into the left traveling motor 4 together with the right traveling motor 5 and drives them.

By the way, the openings for flowing the pressure oil to the downstream side through the central bypass pipelines T ₁₁ and T ₂₁ of the first and second boom direction switching valves 12a and 12b are designed to be closed even with a slight spool movement. ing. Although it is a special operation mode, there is a case where a mud-repelling work is performed in which one traveling crawler belt is lifted in the air and rotated at high speed to repel mud adhered to the traveling crawler belt. At this time, the bucket is grounded on one lateral side and the boom cylinder 6 is extended to float the traveling crawler belt on the same side in the air and rotate the traveling crawler belt at a high speed.

For example, when performing a mud-removing work to repel mud adhered to the left running crawler, rotate the turning motor 3 to the left to position the bucket about 90 ° from the front, and then operate the boom. The portion 54 is slightly operated to slightly move the spools of the first and second boom direction switching valves 12a and 12b to the operating position, and a small amount of pressure oil is added to the boom cylinder 6.
Send to the bottom side of. Then, after the bucket comes into contact with the ground, when the left traveling crawler belt is lifted from the ground, the left traveling direction switching valve 10 is operated by largely operating the left traveling operation portion 52.
The spool is fully moved to the operating position, and a large amount of pressure oil is made to flow into the left traveling motor 4.

At this time, if a fine operation of lowering the boom is performed, a considerable amount of the discharged oil from the first hydraulic pump 1 through the bypass bypass line T ₁₂ is supplied to the left traveling motor 4. While flowing in, the detection output β of the pressure sensor 43
Therefore, when the CNT 35 outputs the drive signal γ = H as in the conventional example, the communication valve 26 opens and, for example, the total flow rate of the discharge oil of the first and second hydraulic pumps 1 and 9 is 9 The pressure oil of the breaker flows intensively, the left running motor 4 rotates at an unexpectedly high speed, and the mud attached to the left running track is splashed off too violently to surprise the surrounding workers, The driving motor 4 may be rapidly deteriorated.

Therefore, in this embodiment, when the right traveling motor 5 is stopped and the left traveling motor 4 is rotating and the actuator for driving the working machine is driven, that is, the hydraulic pressure shown in FIG. As described in the explanation of the circuit, the detection output α of the pressure sensor 40 is P _P / 2, the pressure sensor 4
When the detection output β of 3 is H, the CNT 35 is set not to output the drive signal γ = H. As a result, it is possible to avoid the occurrence of defects that may occur in the above-mentioned conventional example. In the case of the present embodiment, since it is sufficient to simply improve the opening of the spool of the left traveling directional control valve 10,
Not only can the cost required for improvement be kept to a fixed amount, but since a common production line can be used, the production unit price can be kept at the same price as conventional products.

[0034]

As described above, according to the first aspect of the present invention, since the on-off valve attached when the valve of at least one switching valve body is switched to the operating position is the throttle opening, the predetermined position is established. At least the switching of the switching valve to the operating position can be detected depending on whether or not the pilot pressure of the switching valve fluctuates corresponding to the opening amount of the opening / closing valve, and the operating position of the switching valve can be detected easily and inexpensively. It can be realized with a hydraulic circuit. According to the invention of claim 2 or 3, the throttle valve is connected upstream of the switching valve connected to the most upstream of the pilot hydraulic circuit, and the pilot pressure between the switching valve and the throttle valve is detected. By detecting the operating position of the switching valve, the throttle valve is connected to the downstream side of the switching valve connected to the most downstream of the pilot hydraulic circuit, and between the switching valve and the throttle valve. Since the operating position of the switching valve is detected by detecting the pilot pressure, at least one of all switching valves connected in series is selected.
It is possible to detect the switching of the two switching valves to a single operating position.

According to the invention as set forth in claim 4, when the valve of the switching valve body is switched to the operating position, there are a plurality of switching valves in the hydraulic circuit, the switching valves attached to the switching valves being throttle openings.
Since the opening amounts of the throttle openings of the respective on-off valves are different from each other, it is possible to detect the switching of at least the plurality of switching valves to the independent operating positions, respectively. It is possible to control various operations. According to the invention described in claim 5, the applied hydraulic circuit is an actuator driving hydraulic circuit of a hydraulic excavator, and the pilot hydraulic circuit is configured by a circuit in which open / close valves attached to the left and right traveling direction switching valves are connected in series. However, when the valve of the switching valve body was switched to the operating position, the switching valve with the attached on-off valve as the throttle opening was the left traveling direction switching valve, so the left traveling crawler belt was rotated at high speed, It is possible to prevent the left traveling motor from excessively rotating and causing a sudden deterioration when performing a mud-removing work to repel mud attached to it. According to the invention of claim 6, the opening amount of the throttle opening of the opening / closing valve attached to the left traveling direction switching valve is made equal to the opening amount of the throttle valve, so that the temperature change of the pilot oil and the pilot hydraulic circuit It is possible to detect the switching to the operating position of the left traveling directional control valve that is not affected by the flow rate change.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of essential parts of a hydraulic excavator according to an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of a main part of a hydraulic excavator according to another embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram of essential parts of a hydraulic excavator according to still another embodiment of the present invention.

FIG. 4 is a hydraulic circuit diagram of essential parts of a hydraulic excavator according to still another embodiment of the present invention.

FIG. 5 is a hydraulic circuit diagram of essential parts of a hydraulic excavator according to an embodiment of the present invention.

[Explanation of symbols]

 1, 2 First and second hydraulic pumps 3 Swing motors 4, 5 Left and right traveling motors 6 Boom cylinders 7 Arm cylinders 8 Bucket cylinders 9 Swiveling direction switching valves 10, 11 Left and right traveling direction switching valves 12 (a, b) (First and second) boom direction switching valves 13a, 13b First and second arm direction switching valves 14 Bucket direction switching valve 17 Oil tank 20 Motor 25, 58 Throttle valve 26 Communication valve 35 Controller (CNT) 40,43 Pressure sensor 41,42 Pressure switch 56 Pilot pump

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koji Ishikawa, 650 Jinrachicho, Tsuchiura, Ibaraki Prefecture Tsuchiura Plant, Hitachi Construction Machinery Co., Ltd. Stock company Tsuchiura factory

Claims (6)

[Claims] 1. The on-off valves of the switching valve of a hydraulic circuit including a plurality of switching valves provided with on-off valves which are opened when the valve of the main body is in a neutral position, are connected in series, and a throttle valve is provided. In the operating position detecting device for the switching valve of the hydraulic circuit, which detects the operating position of the switching valve by detecting the pilot pressure at a predetermined position of the pilot hydraulic circuit including
An operating position detecting device for a switching valve of a hydraulic circuit, wherein the opening / closing valve is a throttle opening when at least one valve of the switching valve body is switched to an operating position. 2. The throttle valve is connected upstream of a switching valve connected to the uppermost stream of a pilot hydraulic circuit, and the switching valve is detected by detecting a pilot pressure between the switching valve and the throttle valve. The operating position detecting device for the switching valve of the hydraulic circuit according to claim 1, wherein the operating position is detected. 3. A throttle valve is connected to a downstream side of a switching valve connected to the most downstream of a pilot hydraulic circuit, and the switching valve is detected by detecting a pilot pressure between the switching valve and the throttle valve. The operating position detecting device for the switching valve of the hydraulic circuit according to claim 1, wherein the operating position is detected. 4. The opening amount of the throttle opening of each on-off valve is such that there are a plurality of switching valves in the hydraulic circuit, each of which is provided with an on-off valve as a throttle opening when the valve of the switch valve body is switched to the operating position. 4. The operating position detecting device for the switching valve of the hydraulic circuit according to claim 1, wherein the positions are different from each other. 5. A main hydraulic circuit is an actuator driving hydraulic circuit of a hydraulic excavator, a switching valve whose on-off valve is connected in series to a pilot hydraulic circuit is a left / right traveling direction switching valve, and a valve of a switching valve body operates. When switching to the position,
5. An operating position detecting device for a switching valve of a hydraulic circuit according to claim 1, wherein the switching valve provided with an on-off valve provided as a throttle opening is a left traveling direction switching valve. 6. The operation of a switching valve of a hydraulic circuit according to claim 5, wherein the opening amount of the throttle opening of the opening / closing valve attached to the left traveling direction switching valve is equal to the opening amount of the throttle valve. Position detection device.