JP7746083B2 - Electromagnetic proportional valves and construction machinery - Google Patents

Description

The present invention relates to an electromagnetic proportional valve and construction machinery.

An increasing number of fluid systems that control hydraulic circuits in construction machinery are equipped with electrically controlled electromagnetic proportional valves. An electromagnetic proportional valve, for example, comprises an electromagnetic coil (hereafter referred to as a solenoid coil), a rod driven by the solenoid coil, a spool that moves when pressed by the rod, and a return spring that returns the spool to its original position. Such electromagnetic proportional valves are used, for example, as pilot valves for control valves (i.e., main control valves, directional control valves).

Specifically, the electromagnetic proportional valve has a pilot port to which hydraulic oil is supplied from the hydraulic pump, a control port that adjusts the opening of the hydraulic oil to the control valve to be driven, and a drain port connected to a tank that stores return oil.The electromagnetic proportional valve also has a spool that cuts off and connects the pilot port, control port, and drain port.
With an electromagnetic proportional valve, for example, the control pressure of the hydraulic oil is transmitted from the control port to the control valve, thereby controlling the main spool of the control valve and switching the spool position of the main spool. Control pressure is transmitted to the hydraulic equipment of the construction machine according to the switched position of the main spool.

Here, for example, a valve structure that monitors control pressure has been disclosed in order to calibrate the control pressure transmitted from a solenoid proportional valve (see, for example, Patent Document 1). In this structure, a gauge port is provided in the connection block between the solenoid proportional valve and the control valve to be controlled, for extracting the control pressure output from the solenoid proportional valve. A pressure sensor is attached to this gauge port via a fitting. This makes it possible to monitor the control pressure by detecting the control pressure output from the solenoid proportional valve with the pressure sensor.

Japanese Patent Application Laid-Open No. 2001-289202

To detect the control pressure output from the solenoid proportional valve, a pressure sensor must be attached to the gauge port of the connection block via a fitting. This means that the fitting and pressure sensor are located outside the connection block, which hinders efforts to make the valve structure more compact.

One possible solution to this problem is to equip the solenoid proportional valve with a pressure sensor. However, equipping the solenoid proportional valve with a pressure sensor would likely result in the solenoid proportional valve becoming larger. This would require a relatively large space to install the solenoid proportional valve. This poses the problem of having to significantly change the installation layout of the solenoid proportional valve.

The present invention provides a solenoid proportional valve and construction machinery that can reduce the size of a solenoid proportional valve equipped with a pressure sensor and save space required for installing the solenoid proportional valve.

As a means for solving the above problems, the present invention has the following configuration.
An electromagnetic proportional valve according to one aspect of the present invention comprises a solenoid coil, a plunger that is operated by supplying an excitation current to the solenoid coil and changes the pressure of the working fluid supplied to a controlled object, a housing that contains the solenoid coil and the plunger and through which the working fluid is guided, an end cap that is fixed to the axial end of the housing and has a communication hole through which the pressure of the working fluid is transmitted, a pressure sensor that is contained in the end cap and detects the pressure of the working fluid transmitted from the communication hole, and a substrate that is contained in the end cap and on which the pressure sensor is mounted.

In this way, the end cap is fixed to the housing, and the pressure sensor and circuit board are housed together inside the end cap. That is, by embedding the pressure sensor and circuit board together inside the end cap, it is possible to reduce the overall length (i.e., the axial length) of the solenoid proportional valve in particular. Therefore, the pressure sensor and circuit board can be packaged compactly. This allows the solenoid proportional valve equipped with a pressure sensor to be made smaller, and the space required for installing the solenoid proportional valve can be saved. Therefore, high functionality of the solenoid proportional valve can be ensured without significantly changing the installation layout of the solenoid proportional valve.
In particular, by miniaturizing the electromagnetic proportional valve, it becomes possible to easily convert the current proportional valve control system into an IOT (Internet of Things) system, which will enable applications such as abnormality detection and failure prediction.

Furthermore, by storing the pressure sensor and circuit board together inside the end cap, the pressure sensor and circuit board can be placed close to each other. This allows, for example, the wiring connecting the pressure sensor and circuit board to be shortened. This makes it less susceptible to noise from the wiring, further ensuring the high functionality of the solenoid proportional valve.

In the above configuration, the board may amplify the result detected by the pressure sensor and output the result as a signal to a control unit that controls the supply of excitation current to the solenoid coil.

This configuration increases the resolution of the signal from the board, allowing the control unit to control the proportional solenoid valve with high precision.

In the above configuration, the end cap includes a base fixed to the axial end of the housing, and an end cap body that protrudes from the base toward the opposite side of the housing and houses the pressure sensor and the circuit board. The base may have the communication hole and a through-hole through which the drive wiring extending from the solenoid coil is pulled out.

In the above configuration, the housing may be cylindrical, and the end cap body may be positioned eccentrically relative to the central axis of the housing.

In the above configuration, the pressure sensor and the substrate may be arranged in this order inside the end cap body facing away from the housing, and a cap space may be formed between the communication hole and the pressure sensor, which communicates with the communication hole and into which the working fluid flows.

The above configuration may also include a pressing member attached to the end of the end cap opposite the housing, which presses the substrate toward the inside of the end cap.

An electromagnetic proportional valve according to another aspect of the invention comprises a solenoid coil, a plunger that is operated by supplying an excitation current to the solenoid coil and changes the pressure of the working fluid supplied to a controlled object, a cylindrical housing that accommodates the solenoid coil and the plunger and through which the working fluid is guided, an end cap fixed to the axial end of the housing, a pressure sensor that is housed in the end cap and detects the pressure of the working fluid, a circuit board that is housed in the end cap and amplifies the result detected by the pressure sensor and outputs it as a signal to a control unit that controls the supply of excitation current to the solenoid coil, and a pressing member attached to the end of the end cap opposite the housing, and the end cap is configured to press the pressure sensor of the housing against the pressure sensor. The housing includes a base fixed to the end in the axial direction, and an end cap body that protrudes from the base toward the opposite side of the housing and is positioned eccentrically with respect to the central axis of the housing, and houses the pressure sensor and the circuit board. The base has a communication hole that connects the housing to the end cap body, and a through hole through which the drive wiring extending from the solenoid coil is pulled out. Inside the end cap body, the pressure sensor and the circuit board are arranged side by side in this order, facing away from the housing. A cap space is formed between the communication hole and the pressure sensor, which communicates with the communication hole and into which the working fluid flows, and the pressing member presses the circuit board toward the inside of the end cap.

In this way, the end cap is fixed to the housing, and the pressure sensor and circuit board are housed together inside the end cap. That is, by embedding the pressure sensor and circuit board together inside the end cap, it is possible to reduce the overall length (i.e., the axial length) of the solenoid proportional valve in particular. Therefore, the pressure sensor and circuit board can be packaged compactly. This allows the solenoid proportional valve equipped with a pressure sensor to be made smaller, and the space required for installing the solenoid proportional valve can be saved. Therefore, high functionality of the solenoid proportional valve can be ensured without significantly changing the installation layout of the solenoid proportional valve.
In particular, by miniaturizing the electromagnetic proportional valve, it will be possible to easily convert the current proportional valve control system into an IoT system, which will enable applications such as abnormality detection and failure prediction.

Furthermore, by storing the pressure sensor and the board together inside the end cap, the pressure sensor and the board can be placed close to each other. This allows, for example, the wiring connecting the pressure sensor and the board to be shortened. This makes it less susceptible to noise from the wiring, further ensuring high functionality.

Furthermore, the end cap body is offset from the central axis of the housing, which makes it easy to ensure an area for forming the through hole in the base.
The pressure sensor and the circuit board are housed in the end cap body that protrudes from the base. This allows the drive wiring to be drawn out through the through-hole in the base when the pressure sensor and the circuit board are compactly packed together.

In addition, the pressure sensor is positioned away from the housing relative to the cap space into which the working fluid flows, and the substrate is positioned away from the housing relative to the pressure sensor. This allows the cap space into which the working fluid flows, the pressure sensor, and the substrate to be arranged in order facing away from the housing. This allows the pressure sensor to be positioned close to the cap space, allowing the pressure sensor to accurately detect the control pressure of the working fluid that has flowed into the cap space.
Furthermore, the pressure sensor can be placed closer to the substrate, which allows, for example, the wiring connecting the pressure sensor to the substrate to be shorter, making it less susceptible to noise from the wiring and enabling the control pressure detected by the pressure sensor to be amplified with high precision.

In addition, the board is held (retained) inside the end cap by a retaining member. This ensures that the board and pressure sensor are securely held inside the end cap, ensuring the quality of the solenoid proportional valve.

A construction machine according to another aspect of the present invention comprises a vehicle body, an actuator mounted on the vehicle body for driving the vehicle body with actuator working fluid, a control valve for adjusting the amount of actuator working fluid supplied to the actuator, and an electromagnetic proportional valve for adjusting the drive of the control valve by supplying working fluid to the control valve. The electromagnetic proportional valve comprises a solenoid coil, a plunger that is operated by supplying an excitation current to the solenoid coil and changes the pressure of the working fluid supplied to the control valve, a housing that accommodates the solenoid coil and plunger and through which the working fluid is guided, an end cap fixed to the axial end of the housing and having a communication hole through which the pressure of the working fluid is transmitted, a pressure sensor housed in the end cap and detecting the pressure of the working fluid transmitted from the communication hole, and a circuit board housed in the end cap that amplifies the result detected by the pressure sensor and outputs it as a signal to a control unit that controls the supply of excitation current to the solenoid coil.

In this way, the end cap is fixed to the housing, and the pressure sensor and circuit board are housed together inside the end cap. In other words, by embedding the pressure sensor and circuit board together inside the end cap, the overall length (i.e., the axial length) of the solenoid proportional valve can be particularly kept short. This allows the pressure sensor and circuit board to be compact and small. This allows the solenoid proportional valve equipped with a pressure sensor to be made smaller, thereby saving space for installing the solenoid proportional valve. Therefore, it is possible to obtain construction machinery that ensures high functionality of the solenoid proportional valve without significantly changing the installation layout of the solenoid proportional valve.

Furthermore, by storing the pressure sensor and circuit board together inside the end cap, the pressure sensor and circuit board can be placed close to each other. This allows, for example, the wiring connecting the pressure sensor and circuit board to be shortened. This makes it less susceptible to noise from the wiring, resulting in a construction machine with an even more highly functional solenoid proportional valve.

This invention makes it possible to miniaturize a solenoid proportional valve equipped with a pressure sensor, thereby saving space required for installing the solenoid proportional valve.

1 is a schematic configuration diagram of a construction machine according to an embodiment of the present invention. 1 is a block diagram of a hydraulic system including an electromagnetic proportional valve according to an embodiment of the present invention. FIG. 1 is a side view of an electromagnetic proportional valve according to an embodiment of the present invention. 4 is a cross-sectional view of the proportional solenoid valve of FIG. 3 taken along line IV-IV.

Next, a solenoid proportional valve and construction machinery according to an embodiment of the present invention will be described with reference to the drawings.

<Construction machinery>
Fig. 1 is a schematic diagram of a construction machine 100. Fig. 2 is a block diagram of a hydraulic system 1 equipped with a control valve 3 and an electromagnetic proportional valve 5.
1, the construction machine 100 is, for example, a hydraulic excavator. The construction machine 100 includes a revolving unit (an example of a vehicle body in the claims) 101, a running unit (an example of a vehicle body in the claims) 102 provided below the revolving unit 101, and a hydraulic system 1 that drives the revolving unit 101 and the running unit 102 using hydraulic oil supplied from a hydraulic pump (not shown).

The rotating unit 101 rotates above the running unit 102. The rotating unit 101 includes a cab (an example of a vehicle body in the claims) 103 on which an operator can ride, a boom (an example of a vehicle body in the claims) 104 whose one end is swingably connected to the rotating unit 101, an arm (an example of a vehicle body in the claims) 105 whose one end is swingably connected to the other end (tip) of the boom 104, a bucket (an example of a vehicle body in the claims) 106 whose other end (tip) is swingably connected to the other end (tip) of the arm 105, and an operating unit 108 operated by the operator. The rotating unit 101, boom 104, arm 105, and bucket 106 are driven by a hydraulic system 1.

<Hydraulic system>
As shown in Figures 1 and 2, the hydraulic system 1 includes a plurality of actuators 2 that operate a rotating body 101, a boom 104, an arm 105, and a bucket 106, a control valve (an example of a controlled object in the claims) 3 that controls the drive of the plurality of actuators 2, an electromagnetic proportional valve 5 that applies pressure (hereinafter referred to as pilot pressure) of hydraulic oil (an example of a working fluid in the claims) to the control valve 3 based on operation of an operation unit 108 by an operator, and a control unit (controller) 80 that outputs a control signal to the electromagnetic proportional valve 5.

<Control valve>
The control valve 3 is, for example, a main control valve provided with a plurality of valve bodies each having a main spool, each of which is provided in correspondence with a plurality of actuators 2. The position of the main spool of the control valve 3 is switched by the pilot pressure transmitted from the electromagnetic proportional valve 5. In this way, the control valve 3 adjusts the flow rate of hydraulic oil (an example of an actuator working fluid in the claims) to the actuators 2 (e.g., hydraulic cylinders, hydraulic motors) that is supplied via a system separate from the hydraulic oil that acts on the pilot pressure.

<Control unit>
The control unit 80 outputs a control signal (control pulse) to the electromagnetic proportional valve 5 based on the signal output from the operation unit 108 and the signal output from the electromagnetic proportional valve 5. This switches the position of a spool 72 (described later) of the electromagnetic proportional valve 5.

<Solenoid proportional valve>
Figure 3 is a side view showing the electromagnetic proportional valve 5. Figure 4 is a cross-sectional view of the electromagnetic proportional valve 5 taken along line IV-IV in Figure 3. Figures 3 and 4 show a state in which a spool 72 (described later) of the electromagnetic proportional valve 5 is maintained in a discharge position where the hydraulic oil is discharged.
The electromagnetic proportional valve 5 is incorporated into the control valve 3. The electromagnetic proportional valve 5 controls the valve opening based on a control signal output from the control unit 80, thereby moving a main spool (not shown) of the control valve 3 and adjusting the flow rate of hydraulic oil supplied to the actuator 2.

As shown in Figures 3 and 4, the solenoid proportional valve 5 comprises a drive unit 10 and a valve unit 12 connected to the drive unit 10. The drive unit 10 and valve unit 12 are arranged along a central axis 14. Hereinafter, the direction along the central axis 14 may simply be referred to as the "axial direction." The direction perpendicular to the central axis 14 may also be referred to as the "radial direction." Furthermore, the side of the valve unit 12 in the axial direction may also be referred to as the "front," and the side of the drive unit 10 may also be referred to as the "rear."

<Drive unit>
The drive device 10 drives a spool 72 (described later) of the valve unit 12 in the axial direction in response to a drive current to control the axial position of the spool 72. The drive device 10 includes a housing 21, a solenoid coil 22, a guide member 23, a plunger 24, and a drive rod 25 housed in the housing 21, an end cap 26 fixed to seal an opening 21 a at the rear of the housing 21 (hereinafter also referred to as a rear end 21 a; an example of an axial end in the claims), a sensor unit 27 housed in the end cap 26, and a pressing member 28 attached to the end cap 26.

<Housing>
The housing 21 extends in the direction of the central axis 14 (i.e., the axial direction) and is formed in a hollow cylindrical shape. The interior space of the housing 21 is open to the front and rear of the housing 21. The front opening of the housing 21 (i.e., the front end) is sealed by a flange 32.

<Solenoid coil>
A solenoid coil 22 is housed along the inner peripheral surface of the housing 21. The solenoid coil 22 is formed by winding a copper wire in a cylindrical shape so as to correspond to the shape of the housing 21. The solenoid coil 22 is excited based on a control signal input from the control unit 80.

<Guide member>
A guide member 23 is housed radially inside the solenoid coil 22. The guide member 23 is hollow and fits along the inner circumferential surface of the solenoid coil 22. The guide member 23 extends axially and is disposed concentrically with the housing 21. The guide member 23 has an open front end and is fixed to an opening in the flange 32. A guide lid portion 34 is formed at the rear end 23a of the guide member 23. A guide hole 35 passes through the guide lid portion 34 in the axial direction.

<Plunger, drive rod>
A plunger 24 and a drive rod 25 are housed radially inside the guide member 23. The plunger 24 is provided coaxially and integrally with the drive rod 25. The drive rod 25 is a rod-shaped member extending axially forward from the plunger 24. The plunger 24 and the drive rod 25 are arranged coaxially with the central axis 14 in a cylindrical space defined by the guide wall 23b of the guide member 23. The plunger 24 and the drive rod 25 are provided axially movable. The plunger 24 and the drive rod 25 may have an integrated, one-piece structure.

At least a portion of the plunger 24 is made of a magnetic material. At least a portion of the plunger 24 is disposed radially inward of the solenoid coil 22. In other words, the plunger 24 is disposed in a position where at least a portion of the plunger 24 overlaps with the solenoid coil 22 in the axial direction. The plunger 24 also has a through-hole 37 formed in a position radially outward from the central axis 14 and extending in the axial direction.

The internal space of the guide member 23 is divided in the front-rear direction by the plunger 24. Specifically, the internal section of the guide member 23 is divided into a first guide chamber 41 located rearward of the plunger 24 in the axial direction, and a second guide chamber 42 located forward of the plunger 24 in the axial direction.
The first guide chamber 41 and the second guide chamber 42 communicate with each other in the front-rear direction via a through hole 37 in the plunger 24. Hydraulic oil is guided to the first guide chamber 41 and the second guide chamber 42 via a spool through hole 77, which will be described later.

The plunger 24 and the drive rod 25 configured in this manner are moved forward when the solenoid coil 22 is excited.
4 shows a state in which the solenoid coil 22 is not excited. In this state, the spring force of a compression spring 73 (described later) of the valve unit 12 moves a spool 72 (described later), drive rod 25, and plunger 24 rearward, and the rear end of the plunger 24 is positioned in contact with the guide lid portion 34. For this reason, although the first guide chamber 41 is not formed in FIG. 4, for convenience, the reference numeral 41 of the first guide chamber is attached to the boundary between the rear end of the plunger 24 and the guide lid portion 34.

<End cap>
The end cap 26 has a base 45 fixed to the rear end 21a of the housing 21 and an end cap main body 46 protruding from the base 45 toward the opposite side of the housing 21 (i.e., rearward). The base 45 is disposed coaxially with the housing 21, and its outer periphery is formed in a circular shape along the rear end 21a of the housing 21. The base 45 is fixed to the rear end 21a of the housing 21 by crimping the rear end 21a radially inward. Therefore, the opening of the rear end 21a of the housing 21 is sealed by the base 45.

The opening of the front end of the housing 21 is sealed by the flange 32, the valve unit 12, etc., so that the internal space (i.e., the pressure receiving chamber) of the housing 21 is kept airtight. This allows the housing 21 to maintain the pressure receiving chamber at the pilot pressure when the pilot pressure is transmitted to the pressure receiving chamber.
In the embodiment, an example will be described in which the internal space of the housing 21 is kept airtight and serves as the pressure-receiving chamber, but the internal space of the guide member 23 may also be kept airtight and serve as the pressure-receiving chamber.

The base 45 has a recess 51 formed in most of the base 45, a communicating hole 52 formed in the recess 51, and a wiring through hole (an example of a through hole in the claims) 53 formed at a position radially offset from the recess 51 of the base 45.
The recess 51 is formed on the inner surface of the base 45 that faces the inside of the housing 21 and on the side of the end cap body 46 (i.e., rearward). The rear end 23a and guide lid 34 of the guide member 23 are fitted into the recess 51. The recess 51 holds the rear end 23a and guide lid 34 coaxially with respect to the central axis 14.

A communication hole 52 is formed at the bottom of the recess 51 (i.e., the center of the base 45) and penetrates the base 45 in the thickness direction. The communication hole 52 communicates with the second guide chamber 42 via the guide hole 35 of the guide member 23, the first guide chamber 41, and the through-hole 37. The second guide chamber 42 communicates with the control port P3 (described later) via the spool through-hole 77 of the spool 72 (described later). The control port P3 is connected to the control valve 3 (see Figure 2).

The end cap body 46 protruding from the base 45 is hollow and open at the front end 46a and rear end 46b. The end cap body 46 is positioned eccentrically (offset) by an eccentricity amount L with respect to the central axis 14 of the housing 21. In other words, the end cap body 46 is positioned eccentrically by the eccentricity amount L with respect to the base 45. By shifting the position of the end cap body 46 by the eccentricity amount L, an area in the base 45 for forming a pair of wiring through holes 53 is secured.

The wiring through-hole 53 is a hole for pulling out the drive wiring 55 from the solenoid coil 22. With the drive wiring 55 pulled out of this wiring through-hole 53 to the outside of the housing 21, the gap between the wiring through-hole 53 and the drive wiring 55 is sealed with a sealant 56.

<Sensor unit>
The sensor unit 27 is housed inside the end cap body 46. The sensor unit 27 includes a pressure sensor 61 and a substrate 62 on which the pressure sensor 61 is mounted.
The pressure sensor 61 is disposed inside the end cap body 46 and spaced rearward from the base 45. Therefore, a cap space 47 is formed between the base 45 and the pressure sensor 61.

The cap space 47 is formed inside the end cap 26. The cap space 47 is connected to the communication hole 52. Therefore, hydraulic oil flows into the cap space 47 through the communication hole 52. As a result, the pressure sensor 61 detects the pilot pressure flowing into the cap space 47 from the communication hole 52.

The pressure sensor 61 outputs a detection signal indicating the detected pressure to the substrate 62. The pressure sensor 61 is provided so that at least a portion thereof is exposed to the cap space 47. The pressure sensor 61 may have a portion of its front surface 61a exposed to the cap space 47, or the entire front surface 61a may be exposed to the cap space 47.

The front surface 61a of the pressure sensor 61 may have a stainless steel diaphragm, a silicon diaphragm, or other diaphragm. The pressure sensor 61 may also include a strain gauge that converts changes in electrical resistance caused by deformation of the diaphragm into an electrical signal. Pressure sensors applicable to the present invention are not limited to those explicitly described in this specification.

The substrate 62 is housed inside the end cap body 46 and behind the pressure sensor 61. The substrate 62 amplifies the pressure detected by the pressure sensor 61 and outputs the result as a signal to the control unit 80.
Here, inside the end cap body 46, the pressure sensor 61 and the substrate 62 are arranged side by side in this order facing away from the housing 21. Since the cap space 47 is formed between the base 45 and the pressure sensor 61, inside the end cap body 46, the cap space 47, the pressure sensor 61, and the substrate 62 are arranged side by side in this order facing away from the housing 21.

<Pressing member>
The retaining member 28 is attached to a rear end 46b of the end cap body 46 (an example of the end opposite the housing 21 in the claims). The retaining member 28 is formed in a cylindrical shape so as to fit within the inner circumferential surface of the end cap body 46. One method for attaching the retaining member 28 to the end cap body 46 is to form a female thread on the inner circumferential surface of the end cap body 46 and a male thread on the outer circumferential surface of the retaining member 28. This fastens and fixes the retaining member 28 to the end cap body 46. Alternatively, the outer circumferential surface of the retaining member 28 may be press-fitted into the inner circumferential surface of the end cap body 46.

The front portion (on the substrate 62 side) of the retaining member 28 is formed with an expanded diameter portion 28b whose inner diameter increases via a step portion 28a on its inner circumferential surface. The substrate 62 is fitted into this expanded diameter portion 28b. The step portion 28a of the retaining member 28 presses the outer periphery of the substrate 62 toward the interior (front side) of the end cap 26. Therefore, the retaining member 28 holds the substrate 62 inside the end cap 26.
The substrate 62 and the pressure sensor 61 are integrated together. As a result, the substrate 62 and the pressure sensor 61 are securely held inside the end cap 26 by the pressing member 28.

<Valve unit>
The valve unit 12 transmits pilot pressure to the control valve 3 (see FIG. 2 ) to control the main spool of the control valve 3. In this way, the valve unit 12 switches the spool position of the main spool. The valve unit 12 includes a valve body 71, and a spool 72 and a compression spring 73 housed in the valve body 71.

The valve body 71 is formed in a hollow cylindrical shape, extending axially forward from the flange 32, and has a through-hole 75. The pilot port P1 of the valve body 71 is connected to a pressure source (e.g., a hydraulic pump) P. The drain port P2 of the valve body 71 is connected to a tank T. The control port P3 of the valve body 71 is connected to the control valve 3 (see Figure 2).

Spool 72 has an axial shape extending in the axial direction. Spool 72 is provided inside through-hole 75 so as to be movable in the axial direction. The rear end of spool 72 contacts the front end of drive rod 25. Spool 72 has a spool through-hole (through-hole) 77 extending along central axis 14.
A compression spring 73 is provided inside the through-hole 75 and on the front end side of the spool 72. The compression spring 73 presses the rear end of the spool 72 against the drive rod 25 with its spring force.

<Hydraulic system operation>
Next, the operation of the hydraulic system 1 will be described.
The control unit 80 outputs a control signal (control pulse) to the solenoid coil 22 of the electromagnetic proportional valve 5, thereby driving the plunger 24 and the drive rod 25. This switches the position of the spool 72. Switching the position of the spool 72 changes the pilot pressure acting on the control valve 3, which in turn switches the position of the main spool (not shown) of the control valve 3.

In other words, when the solenoid coil 22 is not energized, the spring force of the compression spring 73 of the valve unit 12 maintains the spool 72 in the discharge position. At this time, the flow path from the control port P3 to the tank port T2 via the spool through-hole 77 of the spool 72 is opened. As a result, hydraulic oil is collected from the control valve 3 (see Figure 2) connected to the control port P3 to the tank T connected to the drain port P2.

On the other hand, when a large excitation current is supplied to the solenoid coil 22, the plunger 24 and drive rod 25 of the valve unit 12 move axially forward as indicated by arrow A against the spring force of the compression spring 73. The thrust from the drive rod 25 causes the spool 72 to move as indicated by arrow B and reach the supply position. When the spool 72 is in the supply position, the flow path from the control port P3 to the pilot port P1 via the spool through-hole 77 of the spool 72 is opened. Therefore, hydraulic oil is supplied from the pressure source P connected to the pilot port P1 to the control valve 3 (see Figure 2) connected to the control port P3 as indicated by arrow C. In other words, pilot pressure is applied to the control valve 3.

Here, the control port P3 is connected to the cap space 47 via the spool through-hole 77, the second guide chamber 42, the through-hole 37, the first guide chamber 41, the guide hole 35, and the communication hole 52. Therefore, while the spool 72 is in the supply position, the cap space 47 is maintained at the pilot pressure transmitted from the control port P3. The pressure in the cap space 47 is detected by the pressure sensor 61, and the detected pilot pressure is transmitted from the pressure sensor 61 to the circuit board 62 and amplified. The amplified pilot pressure is output as a signal from the circuit board 62 to the control unit 80. The control unit 80 outputs a control signal to the solenoid coil 22 based on the signal input from the circuit board 62.

When pilot pressure is applied to the control valve 3 from pressure source P via the solenoid proportional valve 5, the position of a main spool (not shown) provided in the control valve 3 is switched. This allows the control valve 3 to adjust the flow rate of hydraulic oil to the actuator 2 (e.g., hydraulic cylinder, hydraulic motor), which is supplied via a system separate from the hydraulic oil that applies the pilot pressure. This hydraulic oil may be supplied from a pressure source separate from pressure source P, or it may be distributed from the same pressure source P and a portion may be supplied to a separate system and used to drive the actuator 2.

In this way, the control unit 80 changes the pilot pressure transmitted to the control port P3 based on the detection signal from the sensor unit 27. The solenoid coil 22 has the role of changing the pilot pressure transmitted to the control port P3 using an excitation current.

As described above, the electromagnetic proportional valve 5 of this embodiment can detect the pilot pressure output from the electromagnetic proportional valve 5 without installing a gauge port or external pressure sensor between the electromagnetic proportional valve 5 and the control valve 3. The electromagnetic proportional valve 5 has an end cap 26 fixed to the housing 21, and the pressure sensor 61 and circuit board 62 are housed together inside the end cap 26. By embedding the pressure sensor 61 and circuit board 62 together inside the end cap 26 in this way, the overall length (i.e., the axial length) of the electromagnetic proportional valve 5 can be particularly reduced. As a result, the pressure sensor 61 and circuit board 62 can be made compact and small. This allows the electromagnetic proportional valve 5 equipped with the pressure sensor 61 to be miniaturized, thereby reducing the space required for installing the electromagnetic proportional valve 5. Therefore, the electromagnetic proportional valve 5 can be highly functional without significantly changing its installation layout.

In particular, by miniaturizing the electromagnetic proportional valve 5, it becomes possible to easily convert the current proportional valve control system into an IOT (Internet of Things) system, which can be used for abnormality detection, failure prediction, and the like.
Furthermore, by storing the pressure sensor 61 and the substrate 62 together inside the end cap 26, the pressure sensor 61 and the substrate 62 can be arranged close to each other. This allows, for example, the wiring connecting the pressure sensor 61 and the substrate 62 to be shortened. This makes it possible to reduce the influence of noise from the wiring, and further ensures high functionality of the solenoid proportional valve 5.

The board 62 amplifies the result (pilot pressure value) detected by the pressure sensor 61 and outputs this result as a signal to the control unit 80. This increases the resolution of the signal from the board 62, allowing the control unit 80 to control the proportional solenoid valve 5 with high precision.
Furthermore, the drive wiring 55 is drawn out from the wiring through-hole 53 of the base 45. The pressure sensor 61 and the substrate 62 are housed in the end cap main body 46 that protrudes from the base 45. This allows the drive wiring 55 to be drawn out from the drive wiring 55 of the base 45 when the pressure sensor 61 and the substrate 62 are kept compact and small.

In addition, the end cap body 46 is offset by an amount L relative to the central axis 14 of the housing 21. This makes it easy to ensure an area on the base 45 for forming the drive wiring 55. As a result, when the pressure sensor 61 and substrate 62 are compactly arranged, the drive wiring 55 can be pulled out from the drive wiring 55 of the base 45.

Furthermore, inside the end cap body 46, the pressure sensor 61 and the substrate 62 are arranged side by side in this order facing away from the housing 21. A cap space 47 into which the hydraulic oil flows is formed between the base 45 and the pressure sensor 61, so inside the end cap body 46, the cap space 47, the pressure sensors 6, 1, and the substrate 62 are arranged side by side in this order facing away from the housing 21. This allows the pressure sensor 61 to be arranged close to the cap space 47. This allows the pressure sensor 61 to accurately detect the control pressure of the hydraulic oil that has flowed into the cap space 47.
Furthermore, the pressure sensor 61 can be disposed close to the substrate 62. This allows, for example, the wiring connecting the pressure sensor 61 and the substrate 62 to be shortened. Therefore, the influence of noise from the wiring can be reduced, and the control pressure detected by the pressure sensor 61 can be amplified with high precision.

In addition, the substrate 62 is held down inside the end cap 26 by the retaining member 28. The substrate 62 is also integrated with the pressure sensor 61. As a result, the substrate 62 and pressure sensor 61 are securely held down inside the end cap 26 by the retaining member 28. This ensures the quality of the solenoid proportional valve 5.

Furthermore, as shown in Figures 1 and 4, in the construction machine 100 of this embodiment, the end cap 26 is fixed to the housing 21, and the pressure sensor 61 and the circuit board 62 are housed together inside the end cap 26. By embedding the pressure sensor 61 and the circuit board 62 together inside the end cap 26 in this way, the overall length (i.e., the axial length) of the solenoid proportional valve 5 can be particularly kept short.

As a result, the pressure sensor 61 and circuit board 62 can be made compact and small. This allows the electromagnetic proportional valve 5 equipped with the pressure sensor 61 to be made smaller, thereby saving space for installing the electromagnetic proportional valve 5. As a result, a construction machine 100 can be obtained that ensures high functionality of the electromagnetic proportional valve 5 without requiring major changes to the installation layout of the electromagnetic proportional valve 5.

Furthermore, by storing the pressure sensor 61 and the substrate 62 together inside the end cap 26, the pressure sensor 61 and the substrate 62 can be arranged close to each other. Therefore, for example, the wiring connecting the pressure sensor 61 and the substrate 62 can be shortened.
This makes it possible to obtain a construction machine 100 that is less susceptible to the effects of noise from the wiring and that further ensures high functionality of the electromagnetic proportional valve 5.

The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the electromagnetic proportional valve 5 is incorporated into the control valve 3. However, the present invention is not limited to this, and the main configuration of the electromagnetic proportional valve 5 described above can be adopted for electromagnetic proportional valves incorporated into various control valves.
In the above embodiment, the solenoid proportional valve 5 is described as being in a forward operation mode in which the control pressure is increased by increasing the excitation current. However, this is not limited to this, and the solenoid proportional valve 5 can also be controlled by a reverse operation mode in which the control pressure is decreased by increasing the excitation current.

In the above embodiment, a hydraulic system 1 using hydraulic oil as the working fluid has been described. The electromagnetic proportional valve 5 used in this hydraulic system 1 has also been described. However, this is not limited to this, and the main configuration of the electromagnetic proportional valve 5 described above can be used in electromagnetic proportional valves used with a variety of fluids. Fluids include both liquids and gases.

In the above embodiment, the holding member 28 is described as being cylindrically formed to fit within the inner circumferential surface of the end cap main body 46. The stepped portion 28a of the holding member 28 is described as pressing the outer periphery of the substrate 62 toward the interior (front side) of the end cap 26. However, this is not limited to this, and the holding member 28 may be attached to the rear end portion 46b of the end cap main body 46 and may be configured to press the substrate 62 toward the interior (front side) of the end cap 26 from the rear end portion 46b side.

In addition, the components of the above-described embodiment may be replaced with well-known components without departing from the spirit of the present invention. Furthermore, the above-described variations may be combined.

Among the embodiments disclosed in this specification, those that are composed of multiple objects may be integrated, and conversely, those that are composed of a single object may be separated into multiple objects. Regardless of whether they are integrated or not, it is sufficient that they are configured in a way that allows the purpose of the invention to be achieved.

1...Hydraulic system, 2...Actuator, 3...Control valve (controlled object), 5...Electromagnetic proportional valve, 14...Center shaft, 21...Housing, 21a...Rear end of housing (axial end of housing), 22...Solenoid coil, 24...Plunger, 26...End cap, 27...Sensor unit, 27, 28...Retaining member, 45...Base, 46...End cap body, 46b...Rear end of end cap body (opposite end of housing), 47...Cap space, 52...Communication hole, 53...Wiring through-hole (through-hole), 55...Drive wiring, 61...Pressure sensor, 62...Platform, 80...Control unit, 100...Construction machine, 101...Rotating body (vehicle body), 102...Traveling body (vehicle body), 103...Cab (vehicle body), 104...Boom (vehicle body), 105...Arm (vehicle body), 106...Bucket (vehicle body)

Claims (7)

A solenoid coil,
a plunger that is operated by supplying an excitation current to the solenoid coil and changes the pressure of the working fluid to be supplied to a controlled object;
a housing that houses the solenoid coil and the plunger and through which the working fluid is guided;
an end cap fixed to an axial end of the housing and having a communication hole through which the pressure of the working fluid is transmitted;
a pressure sensor housed in the end cap for detecting the pressure of the working fluid transmitted through the communication hole;
a substrate housed in the end cap and on which the pressure sensor is mounted ,
The end cap is
a base fixed to the end of the housing in the axial direction;
an end cap body that protrudes from the base toward the opposite side of the housing and accommodates the pressure sensor and the substrate;
Equipped with
The base is
The communication hole;
a through hole through which a driving wire extending from the solenoid coil is drawn out;
have
Solenoid proportional valve. The electromagnetic proportional valve described in claim 1, wherein the board amplifies the result detected by the pressure sensor and outputs the result as a signal to a control unit that controls the supply of excitation current to the solenoid coil. The housing is formed in a cylindrical shape,
3. The proportional solenoid valve according to claim 1 , wherein the end cap body is disposed at a position eccentric to the central axis of the housing. 4. The electromagnetic proportional valve according to claim 1, wherein the pressure sensor and the substrate are arranged side by side in this order inside the end cap body facing away from the housing, and a cap space is formed between the communication hole and the pressure sensor, the cap space communicating with the communication hole and into which the working fluid flows. 5. The proportional solenoid valve according to claim 1 , further comprising a pressing member attached to an end of the end cap opposite to the housing, the pressing member pressing the substrate toward an inside of the end cap. A solenoid coil,
a plunger that is operated by supplying an excitation current to the solenoid coil and changes the pressure of the working fluid to be supplied to a controlled object;
a cylindrical housing that houses the solenoid coil and the plunger and through which the working fluid is guided;
an end cap fixed to an axial end of the housing;
a pressure sensor housed in the end cap for detecting the pressure of the working fluid;
a circuit board housed in the end cap that amplifies the result detected by the pressure sensor and outputs the result as a signal to a control unit that controls the supply of an excitation current to the solenoid coil;
a pressing member attached to an end of the end cap opposite to the housing;
Equipped with
The end cap is
a base fixed to the end of the housing in the axial direction;
an end cap body that protrudes from the base toward the opposite side of the housing and is disposed at a position eccentric to the central axis of the housing, and that houses the pressure sensor and the substrate;
Equipped with
The base is
a communication hole that connects the housing and the end cap body;
a through hole through which a driving wire extending from the solenoid coil is drawn out;
and
the pressure sensor and the substrate are arranged in this order inside the end cap body facing away from the housing, and a cap space is formed between the communication hole and the pressure sensor, which space communicates with the communication hole and into which the working fluid flows;
The pressure member presses the substrate toward the inside of the end cap. The car body and
an actuator provided on the vehicle body and configured to drive the vehicle body with an actuator working fluid;
a control valve for adjusting the amount of the actuator working fluid supplied to the actuator;
an electromagnetic proportional valve that adjusts the drive of the control valve by supplying a working fluid to the control valve;
Equipped with
The electromagnetic proportional valve is
A solenoid coil,
a plunger that is operated by supplying an excitation current to the solenoid coil and that changes the pressure of the working fluid supplied to the control valve;
a housing that houses the solenoid coil and the plunger and through which the working fluid is guided;
an end cap fixed to an axial end of the housing and having a communication hole through which the pressure of the working fluid is transmitted;
a pressure sensor housed in the end cap for detecting the pressure of the working fluid transmitted through the communication hole;
a circuit board housed in the end cap that amplifies the result detected by the pressure sensor and outputs the result as a signal to a control unit that controls the supply of an excitation current to the solenoid coil;
Equipped with
The end cap is
a base fixed to the end of the housing in the axial direction;
an end cap body that protrudes from the base toward the opposite side of the housing and accommodates the pressure sensor and the substrate;
Equipped with
The base is
The communication hole;
a through hole through which a driving wire extending from the solenoid coil is drawn out;
have
Construction machinery.