JP7175141B2 - HYDRAULIC CIRCUIT AND CONTROL VALVE MANUFACTURING METHOD - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention provides a hydraulic circuit including a control valve that controls a hydraulic device such as a hydraulic actuator with hydraulic fluid, and an electromagnetic proportional valve that supplies hydraulic fluid for pilot pressure to the control valve, and is used in such a hydraulic circuit. The present invention relates to a method for manufacturing a control valve with a

Patent Document 1 discloses a hydraulic circuit in which a switching valve is connected to a control valve connected to a hydraulic actuator such as a boom cylinder, and an operating valve and an electromagnetic proportional valve are connected to the switching valve via different pipes. do. The operating valve mechanically adjusts the degree of opening in conjunction with the operating lever, and the electromagnetic proportional valve electrically adjusts the degree of opening in conjunction with the operating lever. The operating valve and the electromagnetic proportional valve are connected to a common pilot pump, and each can adjust the pressure of hydraulic oil from the pilot pump and output it to the control valve.

In the hydraulic circuit disclosed in Patent Literature 1, the switching valve can selectively switch between hydraulic oil directed from the operation valve to the control valve and hydraulic fluid directed from the electromagnetic proportional valve to the control valve, and supply the control valve with the hydraulic fluid. , which ensures a fail-safe function. That is, for example, when the electromagnetic proportional valve fails, the control valve can be controlled by supplying hydraulic oil from the pilot pump to the control valve through the operation valve.

JP 2014-142032 A

The hydraulic circuit of Patent Document 1 requires a switching valve and a plurality of types of piping connected to the switching valve in order to ensure a fail-safe function, resulting in a complicated configuration. On the other hand, in the case of a hydraulic circuit in which hydraulic fluid from the operation valve is supplied to the control valve from a negative type electromagnetic proportional valve that is fully open in the de-energized state, the hydraulic fluid pressure can be adjusted by the electromagnetic proportional valve. In addition, a fail-safe function can be ensured with a simple configuration.

In a hydraulic circuit using such a negative type proportional solenoid valve, the opening of the control valve increases as the amount of operation of the control lever increases, and the pressure of hydraulic oil supplied from the control valve to the proportional solenoid valve increases. . On the other hand, the electromagnetic proportional valve is fully closed by being supplied with a predetermined excitation current when the operation lever is not operated, and the excitation current decreases as the amount of operation of the operation lever increases. , the pressure of the hydraulic fluid supplied to the control valve increases. Then, when the operation amount of the operating lever reaches the maximum, the pilot pressure is output so that the control valve is fully opened. At this time, generally speaking, the operation valve reaches its maximum opening degree, and the electromagnetic proportional valve also reaches its maximum opening degree.

However, in this configuration, the pressure of hydraulic oil output by the operation valve can be reduced by throttling the electromagnetic proportional valve when the operation amount of the operation lever reaches a certain operation amount. Since the pressure of the hydraulic oil to be applied is mechanically determined according to the amount of operation of the control lever, even if the opening of the electromagnetic proportional valve is increased, the pressure of the hydraulic oil cannot be increased. Therefore, for example, even if it is desired to rapidly accelerate the operation of the hydraulic actuator after a certain amount of operation of the operating lever, it is difficult to supply the pilot pressure from the electromagnetic proportional valve to the control valve so as to obtain such operation. is. This is the same for positive type electromagnetic proportional valves.

The present invention has been devised in view of the above circumstances. To provide a method for manufacturing a hydraulic circuit and a control valve, capable of flexibly adjusting the output pressure in a wide adjustment range and thereby flexibly setting the operation pattern of an actuator controlled by the control valve. With the goal.

A hydraulic circuit according to the present invention includes an operation valve that outputs hydraulic oil pressure from a pilot pump according to an operation amount of an operation means, and adjusts the hydraulic oil output pressure from the operation valve according to an excitation current. an electromagnetic proportional valve, which adjusts and outputs the output pressure of the hydraulic fluid from the actuator pump according to the output pressure of the hydraulic fluid from the electromagnetic proportional valve, and the operation amount of the operation means is a predetermined value smaller than the maximum operation amount a control valve that can be brought into a substantially fully open state by the output pressure of the hydraulic oil from the pilot pump that is output by the operation valve when the operation amount is equal to or greater than the operation amount.

The electromagnetic proportional valve is of a type that allows hydraulic fluid to pass through the operating valve in a non-excited state in which the exciting current is not supplied, and cuts off hydraulic fluid from the operating valve when the exciting current is supplied. It may be a proportional valve.
In this case, the hydraulic circuit supplies hydraulic fluid to the control valve in a normal mode or a fail-safe mode, and the normal mode adjusts the excitation current to the solenoid proportional valve. By doing so, the output pressure of the hydraulic oil from the operation valve is adjusted through the electromagnetic proportional valve and output to the control valve. and a mode in which the output pressure of the hydraulic oil from the pilot pump is adjusted only by the operation valve and output to the control valve, and in the normal mode, the electromagnetic proportional valve is not operated with respect to the operation means. When a predetermined excitation current is supplied, the valve is fully closed to cut off hydraulic oil from the operation valve, and is supplied in inverse proportion to the predetermined excitation current as the amount of operation of the operation means increases. The output pressure of hydraulic oil from the operation valve may be adjusted according to the excitation current applied.

Further, a method for manufacturing a control valve according to the present invention includes an operation valve that outputs an output pressure of hydraulic fluid from a pilot pump according to an operation amount of an operation means, and an output pressure of hydraulic fluid from the operation valve according to an exciting current. an electromagnetic proportional valve that adjusts and outputs the output pressure; a control valve that adjusts and outputs the output pressure of the hydraulic oil from the actuator pump according to the pilot pressure as the output pressure of the hydraulic oil from the electromagnetic proportional valve; wherein the step of specifying the output pressure of the hydraulic oil from the pilot pump; The pressure receiving characteristic of the control valve, which allows the control valve to be in a substantially fully open state due to the output pressure of the hydraulic oil from the pilot pump output by the operation valve, is set to the specified output pressure of the hydraulic oil from the pilot pump. and setting based on.

According to the present invention, when hydraulic oil for pilot operation is supplied to the control valve from the electromagnetic proportional valve provided between the control valve and the operation valve, the output pressure of the hydraulic oil is flexibly adjusted within a wide adjustment range. This makes it possible to flexibly set the operation pattern of the actuator controlled by the control valve.

1 is a schematic diagram of a hydraulic circuit according to an embodiment of the invention; FIG. The relationship between the operation amount of the operation lever provided in the hydraulic circuit according to the embodiment of the present invention and the output pressure of the hydraulic oil from the actuator pump that is adjusted by the control valve according to the operation amount and is output to the actuator. It is a figure which shows the represented graph. (A) is a diagram showing a range of output pressure of hydraulic oil from an adjustable actuator pump in a hydraulic circuit according to an embodiment of the present invention; (B) is another aspect of an electromagnetic proportional valve FIG. 3 shows a range of hydraulic fluid output pressures from an adjustable actuator pump in a hydraulic circuit comprising:

A hydraulic circuit 1 according to an embodiment of the present invention will be described below with reference to the drawings.

A hydraulic circuit 1 shown in FIG. 1 includes a pilot pump 10 which is a hydraulic source, an operation valve 11 supplied with hydraulic fluid from the pilot pump 10, and a hydraulic fluid supplied from the pilot pump 10 via the operation valve 11. a control valve 13 that receives hydraulic fluid from the electromagnetic proportional valve 12 and uses the pressure of the hydraulic fluid (hereinafter sometimes referred to as output pressure) as a pilot pressure; and a hydraulic actuator 15. and an actuator pump 14 that supplies hydraulic oil to the control valve 13 , and a control device 16 that controls the exciting current supplied to the electromagnetic proportional valve 12 .

The pilot pump 10 is, for example, a pump that discharges hydraulic oil by being driven by an engine, and is a fixed displacement hydraulic pump in this embodiment. The operation valve 11 allows the hydraulic fluid from the pilot pump 10 to pass through, and adjusts and outputs the output pressure of the hydraulic fluid from the pilot pump 10 according to the amount of operation of the user with respect to the operation lever 11A (operating means). . The operation valve 11 increases the output pressure of hydraulic fluid as the amount of operation of the operation lever 11A increases, and decreases the output pressure of the hydraulic fluid as the amount of operation decreases.

The electromagnetic proportional valve 12 is a spool type electromagnetic proportional valve, and by moving the pilot operation spool 20 according to the excitation current supplied from the control device 16, the opening is adjusted, and the operation from the operation valve 11 is controlled. It is a valve that adjusts the output pressure of oil and supplies it to the control valve 13 . The electromagnetic proportional valve 12 in the present embodiment is of a negative type, and hydraulic oil from the operation valve 11 passes through it in a non-excited state in which no excitation current is supplied, and when an excitation current is supplied, operation from the operation valve 11 is performed. The electromagnetic proportional valve 12 of this embodiment is configured to restrict or block the flow of oil, and in particular, the electromagnetic proportional valve 12 of this embodiment is fully closed by being supplied with a predetermined exciting current, and blocks the working oil from the operation valve 11 .

That is, when the electromagnetic proportional valve 12 adjusts the output pressure of the hydraulic oil from the operation valve 11 and outputs it to the control valve 13, the predetermined excitation current is supplied when the operation lever 11A is not operated. It will be in a fully closed state. On the other hand, the solenoid proportional valve 12 is driven from the fully closed state to which the predetermined exciting current is supplied, according to the exciting current supplied in inverse proportion to the predetermined exciting current as the operation amount of the operation lever 11A increases. By moving the operation spool 20 , the output pressure of the hydraulic oil from the operation valve 11 is adjusted and output to the control valve 13 . The amount of operation at this time is detected by the hydraulic sensor 18 in this embodiment.

In the present embodiment, the state in which the output pressure of hydraulic oil from the operation valve 11 is adjusted via the electromagnetic proportional valve 12 and output to the control valve 13 as described above is called a normal mode. In the normal mode, the electromagnetic proportional valve 12 narrows the opening by adjusting the exciting current, so that the hydraulic oil output pressure from the operation valve 11 can be reduced and output to the control valve 13 . Further, by increasing the opening degree from the narrowed state, the output pressure (pilot pressure) of the hydraulic oil from the operation valve 11 can be increased and output to the control valve 13 . This makes it possible to arbitrarily adjust the output pressure of the hydraulic oil to the control valve 13 .

On the other hand, in the present embodiment, the electromagnetic proportional valve 12 is of the negative type, so that the electromagnetic proportional valve 12 is always in a non-excited state, and the output pressure of the hydraulic oil from the pilot pump 10 is adjusted only by the operation valve 11. can be output to the control valve. This state is called a fail-safe mode in the present embodiment. In the fail-safe mode, for example, when the electromagnetic proportional valve 12 fails, even if the electromagnetic proportional valve 12 is not operated, the hydraulic oil from the pilot pump 10 is adjusted and controlled by the operation valve 11 according to the operation amount of the operation lever 11A. It can be supplied to valve 13 . This makes it possible to operate the hydraulic actuator 15 without using the electromagnetic proportional valve 12 .

As shown in FIG. 1, the electromagnetic proportional valve 12 includes a pilot operation spool 20 which is the above-described shaft-shaped member, a valve body 22 having a spool hole 21 for slidably accommodating the pilot operation spool 20, and a pilot. It has a driving portion 23 that moves the operation spool 20 in the axial direction of the spool hole 21 by an electromagnetic force corresponding to the exciting current, and an elastic member 24 that applies a biasing force to the pilot operation spool 20 .

In addition to the spool hole 21 , the valve body 22 is further provided with an input port 31 , a discharge port 32 and an output port 33 that open to the spool hole 21 . The input port 31 and the discharge port 32 open into the spool hole 21 along the radial direction of the spool hole 21 and open to the outside from the outer peripheral surface of the valve body 22 . The output port 33 is formed at one end of the valve body 22 in the axial direction of the spool hole 21 and opens to the spool hole 21 and to the outside of the valve body 22 in the axial direction. The driving portion 23 is arranged on the axial side of the spool hole 21 opposite to the one side where the output port 33 opens.

The input port 31 is connected to the operation valve 11 via a pipe, and the discharge port 32 is connected via a pipe to a drain portion T from which hydraulic oil is discharged. Also, the output port 33 is connected to the control valve 13 via a pipe. Note that the hydraulic sensor 18 described above detects the pressure in the pipe between the input port 31 and the operation valve 11 .

The pilot operation spool 20 is provided with a hollow hole 40 extending in the axial direction of the spool hole 21 and open at both ends in the axial direction, and an inlet hole 41 and an outlet hole 42 opening into the hollow hole 40 . ing. A first opening 40A at one end of the hollow hole 40 in the axial direction of the spool hole 21 opens in the same direction as the output port 33, and a second opening 40B at the other end is on the drive unit 23 side. open to The inlet hole 41 and the outlet hole 42 open into the hollow hole 40 along the radial direction of the spool hole 21 and open to the outside from the outer peripheral surface of the pilot operation spool 20 .

The inlet hole 41 is connected to the input port 31, faces the inner peripheral surface of the valve main body 22, or connects to the input port 31 and the valve main body 22, depending on the axial movement position of the pilot operation spool 20. facing the inner peripheral surface of When the inlet hole 41 is connected to the input port 31 , hydraulic fluid that has flowed into the input port 31 can flow out of the output port 33 via the inlet hole 41 , the hollow hole 40 and the spool hole 21 . On the other hand, the outlet hole 42 is connected to the discharge port 32, faces the inner peripheral surface of the valve main body 22, or is connected to the discharge port 32 and the valve, depending on the position of the pilot operation spool 20 in the axial direction. It faces the inner peripheral surface of the main body 22 . When the outlet hole 42 is connected to the discharge port 32, the working oil in the spool hole 21 and the hollow hole 40 can flow out to the drain portion T. As shown in FIG.

In the present embodiment, when the inlet hole 41 is connected to the input port 31, the outlet hole 42 faces the inner peripheral surface of the valve body 22, and when the outlet hole 42 is connected to the discharge port 32, the inlet The hole 41 faces the inner peripheral surface of the valve body 22 . Therefore, the pilot operation spool 20 connects the inlet hole 41 to the input port 31 and disconnects the outlet hole 42 from the discharge port 32 according to the position (movement position) in the axial direction to which the driving portion 23 moves. , and a state in which the outlet hole 42 is connected to the discharge port 32 and the inlet hole 41 is blocked from the input port 31 .

FIG. 1 shows a non-excited state in which an exciting current is not applied to the drive section 23 constituted by a solenoid actuator, and shows a state in which the pilot operation spool 20 is not moved by the drive section 23 . At this time, the pilot operation spool 20 connects the inlet hole 41 to the input port 31 in a fully open state. From this fully open state, the above-mentioned predetermined excitation current is supplied to the driving portion 23, whereby the pilot operation spool 20 moves away from the driving portion 23, thereby blocking the entrance hole 41 and the input port 31. At the same time, a fully closed state in which the outlet hole 42 is connected to the discharge port 32 is reached. In the negative type, the output pressure of the hydraulic oil from the pilot pump 10 supplied to the control valve 13 increases as the exciting current becomes smaller from this fully closed state.

When the predetermined excitation current is supplied to the driving portion 23 and the pilot operation spool 20 moves away from the driving portion 23, the elastic member 24 made of a coil spring is compressed, and the elastic member 24 moves toward the pilot. An urging force is stored to push the operation spool 20 back toward the driving portion 23 . Therefore, when the driving portion 23 is de-excited, the pilot operation spool 20 returns to the driving portion 23 side.

Next, the control valve 13 will be explained. The control valve 13 adjusts the degree of opening by moving the actuator operation spool 131 according to the pilot pressure of the hydraulic fluid from the pilot pump 10 output from the electromagnetic proportional valve 12, thereby adjusting the opening of the hydraulic fluid from the actuator pump 14. Output by adjusting the output pressure. The control valve 13 is a normally closed type valve that increases its opening as the pilot pressure from the hydraulic oil from the pilot pump 10 increases, and is fully closed when the pilot pressure does not act.

The actuator pump 14 is, for example, a pump that discharges hydraulic oil by being driven by an engine, and is a variable displacement hydraulic pump in this embodiment. The hydraulic actuator 15 is a hydraulic cylinder in the illustrated example, and the greater the hydraulic oil output from the actuator pump 14 adjusted by the control valve 13, the greater the amount of movement of the rod.

Next, FIG. 2 shows the relationship between the amount of operation of the operating lever 11A and the output pressure of hydraulic oil from the actuator pump 14 that is adjusted by the control valve 13 according to the amount of operation and is output to the hydraulic actuator 15. It shows a graph with The horizontal axis indicates the amount of operation of the operating lever 11A, and the vertical axis indicates the output pressure of hydraulic oil from the actuator pump 14. As shown in FIG. Smax on the horizontal axis indicates the maximum amount of operation for the operating lever 11A, and Sde indicates the predetermined amount of operation for the operating lever 11A that is smaller than the maximum amount of operation Smax. A line Lco in FIG. 2 is assumed as another mode in a hydraulic circuit that supplies hydraulic oil pressure-regulated by an operation valve to a control valve from a negative type electromagnetic proportional valve that is fully opened in a non-excited state. It shows the relationship between the operation amount of the lever and the output pressure of the hydraulic oil output to the hydraulic actuator.

With the setting indicated by the line Lco, the output pressure of the hydraulic oil output to the hydraulic actuator becomes maximum when the operation amount of the control lever reaches the maximum operation amount Smax. That is, in this setting, as the operation amount of the operation lever increases, the output pressure of the hydraulic oil supplied from the operation valve to the electromagnetic proportional valve increases, and when the operation amount of the operation lever reaches the maximum operation amount Smax, the electromagnetic The pilot pressure of hydraulic oil output from the proportional valve to the control valve is maximized. This maximum pilot pressure means that the control valve is fully opened.

On the other hand, line Lin indicates the relationship between the amount of operation of the control lever and the output pressure of hydraulic oil output to the hydraulic actuator, which is set in the hydraulic circuit 1 according to the present embodiment. In the setting indicated by this line Lin, when the operation amount of the control lever 11A is operated to a predetermined operation amount Sde smaller than the maximum operation amount Smax in a state where the electromagnetic proportional valve 12 is de-excited (that is, fail-safe mode). indicates that the control valve 13 is in a substantially fully open state.

That is, in the setting according to this embodiment, as the operation amount of the operation lever increases, the output pressure of the hydraulic oil supplied from the operation valve to the electromagnetic proportional valve increases, and the operation amount of the operation lever 11A increases. When the operation amount is equal to or greater than a predetermined operation amount Sde which is smaller than the maximum operation amount Smax, the hydraulic oil output from the non-excited electromagnetic proportional valve 12 to the control valve 13 causes the control valve 13 to be substantially fully opened. At this time, the hydraulic oil output pressure (pilot pressure) output from the electromagnetic proportional valve 12 to the control valve 13 is output from the electromagnetic proportional valve to the control valve when the maximum operation amount Smax is reached in the setting according to the line Lco. It is a value smaller than the pilot pressure of hydraulic oil.
The substantially fully open state of the control valve 13 is the state of opening when the control valve 13 causes the maximum amount of hydraulic oil to flow out from the actuator pump 14, and the opening portion through which the hydraulic oil flows out is predetermined. It means a state in which it is opened to the maximum degree of opening or a state that can be regarded as the maximum degree of opening.

The setting indicated by line Lin is realized by making the pressure receiving characteristic of the control valve 13 different from the pressure receiving characteristic of the normally closed type control valve used in the hydraulic circuit having the setting indicated by line Lco. can be done. Specifically, the normally closed type control valve 13 is always biased by a spring so that the fully closed state is maintained when not receiving pilot pressure, and approaches the fully open state as the pilot pressure increases. If the elastic force (spring constant) of this spring is made smaller than the spring of the control valve of the hydraulic circuit having the setting indicated by line Lco, the setting indicated by line Lin is obtained.

More specifically, the setting indicated by the line Lin is obtained by performing the following procedure, for example. First, the output pressure of hydraulic oil discharged from the pilot pump 10 before it flows into the operation valve 11 is specified. Based on the specified output pressure, when the operation amount of the operation lever 11A becomes a predetermined operation amount Sde smaller than the maximum operation amount Smax, the pressure is supplied to the control valve 13 via the operation valve 11 and the electromagnetic proportional valve 12 in the fully open state. Calculate the hydraulic fluid output pressure to be applied. Next, the pressure-receiving characteristics of the control valve 13, which is in the fully open state, that is, the characteristics of the spring are set according to the calculated output pressure.

As described above, in both the hydraulic circuit 1 according to the present embodiment and the hydraulic circuit having the setting indicated by the line Lco, the electromagnetic proportional valve restricts the opening degree of the output pressure of the hydraulic oil passing through it. to adjust. At this time, in these hydraulic circuits, the output pressure of the hydraulic oil output by the operation valve when the operation lever reaches a certain operation amount is mechanically determined according to the operation amount of the operation lever. Therefore, the output pressure of this hydraulic oil cannot be increased even if the opening of the electromagnetic proportional valve is increased. Therefore, in the hydraulic circuit 1 according to the present embodiment, the range of the output pressure to the actuator that can be adjusted by the control valve by the pilot pressure adjusted by the electromagnetic proportional valve is the range below the line Lin, and the line Lco , the range is below the line Lco.

That is, in the hydraulic circuit 1 according to the present embodiment, by adjusting the electromagnetic proportional valve 12, the output pressure to the actuator can be adjusted within the hatched range shown in FIG. , the output pressure to the actuator can be adjusted in the hatched range shown in FIG. 3(B).

Here, as is clear from comparing (A) and (B) in FIG. 3, in the present embodiment, the output pressure to the actuator is controlled in a wider range than the hydraulic circuit having the setting indicated by line Lco. can be adjusted. Specifically, in the hydraulic circuit 1 according to the present embodiment, by adjusting the excitation current for the solenoid proportional valve 12, the line Lco is set above the line Lco, which cannot be set in the hydraulic circuit having the setting indicated by the line Lco. The output pressure to the actuator can be obtained as shown in the following line Lad. Therefore, it is possible to flexibly set the operation pattern of the actuator.

In addition, in the hydraulic circuit 1 according to the present embodiment, the smaller the predetermined operation amount Sde is, the wider the adjustment range of the output pressure to the actuator can be. Although the value of the predetermined operation amount Sde is not particularly limited, if the predetermined operation amount Sde is set to 95% or less of the maximum operation amount Smax, it becomes possible to relatively flexibly adjust the output pressure to the actuator. . The predetermined operation amount Sde is preferably 90% or less of the maximum operation amount Smax, more preferably 80% or less, even more preferably 70% or less, and even more preferably 50% or less. preferable.

As described above, in the hydraulic circuit 1 according to the present embodiment, when the operation amount of the operation lever 11A reaches the predetermined operation amount Sde which is smaller than the maximum operation amount Smax, the proportional electromagnetic valve 12 outputs to the control valve 13 The degree of opening of the control valve 13 is fully opened by the hydraulic oil. With such a setting, when hydraulic oil for pilot operation is supplied to the control valve 13 from the negative type electromagnetic proportional valve 12 provided between the control valve 13 and the operation valve 11, the output pressure of the hydraulic oil can be flexibly adjusted in a wide adjustment range, which makes it possible to flexibly set the operation pattern of the actuator controlled by the control valve 13.

Further, in the present embodiment, since the proportional solenoid valve 12 is of the negative type, the output pressure of the hydraulic oil from the pilot pump 10 is adjusted only by the operation valve 11 when the proportional solenoid valve 12 is in a non-excited state. A fail-safe function is ensured by being able to output to the control valve 13 as a result. It is also useful in that such a fail-safe function can be ensured without complicating the configuration.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications may be made in each of the above-described embodiments. For example, in the above-described embodiment, the proportional solenoid valve 12 is of the negative type in order to ensure the fail-safe function without complicating the configuration, but the proportional solenoid valve 12 is of the positive type. good too.

Reference Signs List 1 Hydraulic circuit 10 Pilot pump 11 Operation valve 11A Operation lever 12 Electromagnetic proportional valve 13 Control valve 14 Actuator pump 15 Hydraulic actuator 16 Control device 20 Pilot operation spool 131 Actuator operation spool

Claims (4)

an operation valve that outputs the output pressure of the hydraulic oil from the pilot pump according to the operation amount of the operation means;
an electromagnetic proportional valve that adjusts and outputs the output pressure of hydraulic oil from the operation valve according to the excitation current;
When the output pressure of the hydraulic fluid from the actuator pump is adjusted according to the output pressure of the hydraulic fluid from the electromagnetic proportional valve and output, and the operation amount of the operation means is equal to or greater than a predetermined operation amount that is smaller than the maximum operation amount and a control valve that can be brought into a substantially fully open state by the output pressure of the hydraulic oil from the pilot pump that the operating valve outputs via the fully open electromagnetic proportional valve . Hydraulic fluid from the operating valve passes through the electromagnetic proportional valve in a non-excited state in which the exciting current is not supplied, and cuts off hydraulic fluid from the operating valve when the exciting current is supplied. 1. The hydraulic circuit according to 1. The hydraulic circuit supplies hydraulic oil to the control valve in normal mode or fail-safe mode,
The normal mode is a mode in which the output pressure of hydraulic oil from the operation valve is adjusted via the proportional solenoid valve and output to the control valve by adjusting the excitation current for the proportional solenoid valve,
The fail-safe mode is a mode in which the proportional solenoid valve is always in a non-excited state, and the output pressure of hydraulic oil from the pilot pump is adjusted only by the operation valve and output to the control valve,
In the normal mode, the electromagnetic proportional valve is fully closed by being supplied with a predetermined exciting current when the operation means is not operated, and cuts off hydraulic oil from the operation valve. According to claim 2, the output pressure of hydraulic oil from the operation valve is adjusted according to the excitation current supplied in inverse proportion to the predetermined excitation current as the operation amount of the operation means increases. Hydraulic circuit as described. an operation valve that outputs the output pressure of hydraulic fluid from a pilot pump in accordance with an operation amount of an operation means; an electromagnetic proportional valve that adjusts and outputs the output pressure of hydraulic fluid from the operation valve in accordance with an excitation current; A method for manufacturing a control valve in a hydraulic circuit comprising a control valve that adjusts and outputs the output pressure of hydraulic fluid from an actuator pump according to the output pressure of hydraulic fluid from the electromagnetic proportional valve,
identifying the output pressure of hydraulic fluid from the pilot pump;
The control valve is controlled by the output pressure of hydraulic oil from the pilot pump that is output via the electromagnetic proportional valve in which the operation valve is fully open when the operation amount of the operation means is equal to or greater than a predetermined operation amount that is smaller than the maximum operation amount. and setting a pressure receiving characteristic of the control valve that can be in a substantially fully open state based on the identified output pressure of hydraulic oil from the pilot pump.

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