WO2011090256A1

WO2011090256A1 - Solenoid valve for transmission

Info

Publication number: WO2011090256A1
Application number: PCT/KR2010/007280
Authority: WO
Inventors: Chang Hoon Lee; Eui Dong Roh; Young Keun Kim; Tae Hyeon Kim; Sang Don Eom
Original assignee: Unick Corporation
Priority date: 2010-01-22
Filing date: 2010-10-22
Publication date: 2011-07-28
Also published as: CN102301167B; CN102301167A; KR101016189B1

Abstract

A solenoid valve for a transmission is provided which can directly control a clutch of an automatic transmission. That is, it is possible to provide a solenoid valve for a transmission which includes a plunger, a core, and a yoke separated from the core by 1.5 mm to 2.5 mm and having three widths and which can guarantee a magnetic force sufficient to control a high pressure and a high flow rate. It is also possible to provide a solenoid valve for a transmission in which a feedback flow channel has a diameter of 0.5 mm to 1.5 mm and a thickness of 1.5 mm to 2.5 mm to enhance an overlap. It is possible to provide a solenoid valve for a transmission which can prevent the deformation of the solenoid valve to improve the durability even with an application of an external force by including a guide allowing the core and the yoke to form a body. It is also possible to provide a solenoid valve for a transmission which is resistant to foreign particles by mounting the filter on at least one of the supply port and the control port of the holder.

Description

SOLENOID VALVE FOR TRANSMISSION

The present invention relates to a solenoid valve for a transmission, and more particularly, to a solenoid valve for a transmission which can directly control a clutch of an automatic transmission.

In general, an internal combustion engine of a vehicle requires a high torque and a low revolution speed at the time of start driving the vehicle and requires more high revolution speed than torque to enhance the traveling speed. Accordingly, a transmission serves to reduce the revolution speed and to enhance the torque at the time of start using a gear to keep the revolution of the engine constant, and to enhance the revolution speed so as to enhance the traveling speed. Such transmissions are classified into manual transmissions causing a driver to directly operate the clutch and automatic transmissions directly changing the speed using a hydraulic pressure.

In the past, solenoid valves of an indirect control type which indirectly controls a clutch using a reduced control pressure were often used in the automatic transmissions. Such solenoid valves of an indirect control type require a complicated hydraulic circuit for controlling a high flow rate and a high clutch pressure. However, in the solenoid valves employing the indirect control type, the hydraulic circuit becomes more complicated with an increase in transmission degree of a transmission and the size of the valves thus increases, thereby raising the manufacturing cost. Accordingly, a solenoid valve in which the hydraulic circuit can be simplified to reduce the total size of the solenoid valve and to lower the manufacturing cost has been studied.

A goal of the invention is to provide a solenoid valve for a transmission which can guarantee a magnetic force sufficient to control a high hydraulic pressure and a high flow rate.

Another goal of the invention is to provide a solenoid valve for a transmission which can enlarge an overlap.

According to an aspect of the invention, there is provided a solenoid valve for a transmission having a solenoid section and a valve section made to work by the solenoid section, wherein the solenoid section includes: a core; a yoke separated from the core by a predetermined gap and having a first width, a second width, and a third width, which are different from each other, sequentially in a direction getting close to the core in a plane parallel to a longitudinal direction; and a plunger made to reciprocate by the core and the yoke so as to cause the valve section to operate. The first width may be greater than the second width and the second width may be greater than the third width. The yoke may include a first surface and a ninth surface forming the first width, a fourth surface and the ninth surface forming the second width, and a sixth surface and the ninth surface forming the third width in the sectional plane in the longitudinal direction. Here, a second surface which is an oblique plane and a third surface which is a vertical plane may be formed between the first surface and the fourth surface, a fifth surface which is an oblique plane may be formed between the fourth surface and the sixth surface, and a seventh surface which is an oblique plane and an eighth surface which is connected to an end of the ninth surface and which is a vertical plane may be formed at an end of the sixth surface.

The predetermined gap between the yoke and the core may be in the range of 1.5 mm to 2.5 mm. The valve section may include: a hollow holder having one or more chambers and ports formed therein; and a spool having one or more annular grooves and vertically reciprocating in the holder by the solenoid section. The holder may have a discharge chamber, a control chamber, a supply chamber, and a feedback chamber which are sequentially formed toward the solenoid section, and the spool may have a first annular groove and a second annular groove having a width smaller than that of the first annular groove, which are sequentially formed toward the solenoid section. On the contrary, the holder may have a feedback chamber, a supply chamber, a control chamber, and a discharge chamber which are sequentially formed toward the solenoid section, and the spool may have a first annular groove and a second annular groove having a width greater than that of the first annular groove, which are sequentially formed toward the solenoid section.

The solenoid valve may further include: a feedback flow channel formed in the feedback chamber of the holder; a supply port formed at one end of the supply chamber of the holder; a control flow channel formed in the control chamber of the holder; a control port formed at one end of the control chamber of the holder; and a discharge port formed at one end of the discharge chamber of the holder. Here, the feedback flow channel may be connected to the control flow channel, and the feedback flow channel may have a diameter of 0.5 mm to 1.5 mm and a thickness of 1.5 mm to 2.5 mm.

The solenoid valve may further include a filter mounted on at least one of the supply port and the control port. Here, a filter mounting groove may be formed in at least one of the supply port and the control port, and mounting jaws to be mounted on the filter mounting groove may be formed at ends of the filter.

The solenoid valve may further include a guide disposed to surround the outer circumferences of the core and the yoke and to allow the core and the yoke to form a body. In this case, end jaws may be formed in the outer circumferences of the core and the yoke, and the guide may be disposed in the end jaws.

According to the above-mentioned configurations, it is possible to provide a solenoid valve for a transmission which includes a plunger, a core, and a yoke separated from the core by 1.5 mm to 2.5 mm and having three widths and which can guarantee a magnetic force sufficient to control a high pressure and a high flow rate.

It is also possible to provide a solenoid valve for a transmission in which a feedback flow channel has a diameter of 0.5 mm to 1.5 mm and a thickness of 1.5 mm to 2.5 mm to enhance an overlap.

According to the above-mentioned configurations, it is possible to provide a solenoid valve for a transmission which can prevent the deformation of the solenoid valve to improve the durability, by including a guide allowing the core and the yoke to form a body.

It is also possible to provide a solenoid valve for a transmission which is resistant to foreign particles by mounting the filter on at least one of the supply port and the control port of the holder.

FIG. 1 is a sectional view of a solenoid valve for a transmission according to a first embodiment of the invention.

FIG. 2 is an enlarged sectional view of Area A of FIG. 1.

FIG. 3 is a sectional view of a solenoid valve for a transmission according to a modified example of the first embodiment of the invention.

FIG. 4 is a side view of a holder of the solenoid valve for a transmission according to the modified example of the first embodiment of the invention.

FIG. 5 is a sectional view of a yoke of the solenoid valve for a transmission according to the first embodiment of the invention.

FIG. 6 is a sectional view of a core and a yoke of the solenoid valve for a transmission according to the modified example for the first embodiment of the invention.

FIG. 7 is a sectional view illustrating a pressure flow when the solenoid valve for a transmission according to the first embodiment of the invention operates.

FIG. 8 is a sectional view of a solenoid valve for a transmission according to a second embodiment of the invention.

FIG. 9 is an enlarged sectional view of Area B of FIG. 8.

FIG. 10 is a diagram illustrating output waveforms of the solenoid valve of a transmission according to the second embodiment of the invention and a solenoid valve for a transmission according to the related art.

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings.

However, the invention is not limited to the following embodiments, but can be modified in various forms. The embodiments are provided to complete the disclosure of the invention and to completely notify the scope of the invention to those skilled in the art. Like reference numerals in the drawings reference like elements.

FIG. 1 is a sectional view of a solenoid valve for a transmission according to a first embodiment of the invention. FIG. 2 is an enlarged sectional view of Area A of FIG. 1. FIG. 3 is a sectional view of a solenoid valve for a transmission according to a modified example of the first embodiment of the invention. FIG. 4 is a side view of a holder of the solenoid valve for a transmission according to the modified example of the first embodiment of the invention. FIG. 5 is a sectional view of a yoke of the solenoid valve for a transmission according to the first embodiment of the invention. FIG. 6 is a sectional view of a core and a yoke of the solenoid valve for a transmission according to the modified example for the first embodiment of the invention. FIG. 7 is a sectional view illustrating a pressure flow when the solenoid valve for a transmission according to the first embodiment of the invention operates.

The solenoid valve for a transmission according to the first embodiment of the invention includes a valve section 110 and a solenoid section 200 driving the valve section 100.

The valve section 100 is disposed on a valve body (not shown) side having plural flow channels, serves to supply a fluid to a clutch (not shown) while applying a predetermined control pressure to the fluid supplied from a hydraulic pressure supply source, and includes a hollow holder 110, a spool 120 movably disposed in the holder 110, and a spring 130 and a pressure adjusting screw 140 disposed on the top of the spool 120.

The holder 110 has a hollow shape in which the spool 120 is guided. A discharge chamber 117a, a control chamber 113a, a supply chamber 115a, and a feedback chamber 112 are sequentially formed from up to down in the spool 120. Here, a discharge port 117b is formed at one end of the discharge chamber 117a and a residual pressure is partially discharged from the discharge port 117b. A control port 113b connected to the clutch (not shown) of the transmission and serving to control the clutch pressure is formed at one end of the control chamber 113a. A supply port 115b connected to an external hydraulic pressure supply source is formed at one end of the supply chamber 115a. An opening 118 which is closed by a mounting surface of the valve body when it is mounted on the valve body (the left dotted portion in FIG. 4) is formed at one end of the feedback chamber 112. A first auxiliary discharge chamber 111a as a space in which oil attached to the outer peripheral surface of the spool 120 temporarily remains is formed at the top of the holder 110, and a first auxiliary discharge port 114a discharging the oil remaining in the first auxiliary discharge chamber 111a to make the movement of the spool 120 free is formed at one end of the first auxiliary discharge chamber 111a. A second auxiliary discharge chamber 111b is formed at the bottom of the holder 110, and a second auxiliary discharge port 114b discharging the oil attached to the outer peripheral surface of the spool 120 and other foreign materials to the outside and removing the residual pressure is formed at one end of the second auxiliary discharge chamber 111b. On the other hand, as shown in FIG. 4, a flow channel causing the feedback chamber 112 and the control chamber 113a to communicate with each other is formed on one outer peripheral surface of the holder 110. This flow channel includes a feedback flow channel 119 formed in the feedback chamber 112 and a control flow channel 116 formed in the control chamber 113a, and is closed by the mounting surface of the valve body when the solenoid valve according to the first embodiment of the invention is mounted on the valve body (the right dotted portion in FIG. 4).

On the other hand, the solenoid valve according to the invention may further include a filter 150 in at least one of the control port 113b and the supply port 115b of the holder 110, as shown in FIG. 3.

The filter 150 serves to filter foreign particles introduced into the control port 113b and the supply port 115b of the holder 110 and has plural holes in an annular belt shape. In this embodiment, a first filter 150a is disposed in the control port 113b and a second filter 150b is disposed in the supply port 115b. As shown in FIG. 4, filter mounting grooves R1 and R2 are formed in the control port 113b and the supply port 115b, respectively, so as to mount and fix the first and

second filters

150a and 150b. Mounting jaws bent at a predetermined angle are formed at ends of the first filter 150a and the second filter 150b, respectively, so that the mounting jaws are mounted on the filter mounting grooves R1 and R2 to mount and fix the first and

second filters

150a and 150b on and to the control port 113b and the supply port 115b.

The opened region at the top of the holder 110 is provided with a pressure adjusting screw 140 adjusting the control pressure applied to the clutch via the control port 113b and capable of being adjusted up and down. A spring 130 supplying an elastic force toward the bottom of the spool 120 and buffering the spooling 120 at the time of the up and down movement of the spool 120 is disposed between the pressure adjusting screw 140 and the spool 120.

The spool 120 is movable in the hollow holder 110 and one or more annular grooves are formed on the outer peripheral surface thereof. In this embodiment, a first annular groove 121a and a second annular groove 121b having a width smaller than that of the first annular groove 121a are sequentially formed toward the solenoid section 200. The first and second annular grooves switch the flow of fluid or open and close the supply port 115b, the control port 113b, and the discharge port 117b.

The solenoid section 200 serves to drive the valve section 100 and includes a bobbin 210 wound with a coil 220, a case 230 surrounding the outer peripheral surface of the bobbin 210, a plunger 240 being movable up and down in the bobbin 210, a rod 250 fixed to the center of the plunger 240 and contacting the bottom of the spool 120, a core 260 disposed at one end of the plunger 240, a yoke 270 disposed at the other end of the plunger 240, and a terminal portion 280 connected to the yoke 270. A terminal 294 and a poke terminal 296 are disposed below the terminal portion 280.

The bobbin 210 has a hollow cylindrical shape and the coil 220 is wound on the outer peripheral surface thereof. The core 260 and the yoke 270 are partially housed in the hollow portion of the bobbin 210 so as to be separated from each other by a predetermined gap.

The plunger 240 is disposed between the core 260 and the yoke 270 and moves toward the core 260 by a magnetic field generated with the application of current to the coil 220. At this time, a first core 260 hollow portion in which a magnetic force is concentrated on the part adjacent to the plunger 240 is formed in the core 260, and one end of the plunger 240 is partially housed in the first core hollow portion. A second core hollow portion having a diameter smaller than that of the first core hollow portion is formed on the top of the first core hollow portion, and the top end of the rod 250 is movably housed in the second core hollow portion.

In the yoke 270, a first yoke hollow portion is formed in a part adjacent to the plunger 240, and the other end of the plunger 240 is partially housed in the first yoke hollow portion. A second yoke hollow portion having a diameter smaller than that of the first yoke hollow portion and the bottom end of the rod 250 is movably housed in the second yoke hollow portion.

As shown in FIG. 2, the yoke 270 is separated from the core 260 by a predetermined gap. At this time, the core 260 and the yoke 270 are separated from each other by a gap of 1.5 mm to 2.5 mm. When the gap between the core 260 and the yoke 270 is greater than the above-mentioned range, the magnetic force is reduced. When the gap is smaller than the above-mentioned range, the return of the plunger 240 is affected at the time of power off.

In the yoke 270, as shown in FIG. 5, an area adjacent to the core 260 has first to ninth surfaces S₁ to S₉, and a first angle θ₁ is formed at the boundary between the first surface S₁ and the second surface S₂. A second angle θ₂ is formed at the boundary between the second surface S₂ and the third surface S₃ and a third angle θ₃ is formed at the boundary between the third surface S₃ and the fourth surface S₄. A fourth angle θ₄ is formed at the boundary between the fourth surface S₄ and the fifth surface S₅ and a fifth angle θ₅ is formed at the boundary between the fifth surface S₅ and the sixth surface S₆. Sixth to eighth angles θ₆, θ₇, and θ₈ are formed at the boundary between the sixth surface S₆ and the seventh surface S₇, the boundary between the seventh surface S₇ and the eighth surface S₈, and the boundary between the eighth surface S₈ and the ninth surface S₉, respectively. Here, the first surface S₁, the fourth surface S₄, the sixth surface S₆, and the ninth surface S₉ are parallel to each other, and the third surface S₃ and the eighth surface S₈ are parallel to each other. The first angle θ₁, the second angle θ₂, the fourth angle θ₄, the sixth angle θ₆, the seventh angle θ₇, and the eighth angle θ₈ are bent in the direction different from that of the third angle θ₃ and the fifth angle θ₅. The first angle θ₁, the second angle θ₂, and the fourth to seventh angles θ₄ to θ₇ are obtuse, and the third angle θ₃ and the eighth angle θ₈ are right. Accordingly, the yoke 270 includes the first surface S₁, the second surface S₂ extending from the first surface S₁ and being obliquely bent to one side, the third surface S₃ extending from the second surface S₂ and being vertically bent to one side, the fourth surface S₄ extending from the third surface S₃ and being bent to the other side, the fifth surface S₅ extending from the fourth surface S₄ and being bent to one side, the sixth surface S₆ extending from the fifth surface S₅ and being bent to the other side, the seventh surface S₇ extending from the sixth surface S₆ and being obliquely bent to one side, the eighth surface S₈ extending from the seventh surface S₇ and being vertically bent to one side, and the ninth surface S₉ extending from the eighth surface S₈ and being bent to one side so as to partially overlap with the first surface S₉. According to this structure, a first width P₁ between the first surface S₁ and the ninth surface S₉, a second width P₂ between the fourth surface S₄ and the ninth surface S₉, and a third width P₃ between the sixth surface S₆ and the ninth surface S₉ are different from each other. At this time, the first width P₁, the second width P₂, and the third width P₃ have a relation of the first width P₁> the second width P₂>the third width P₃.

In this embodiment, since the yoke 270 has the above-mentioned shape, it is possible to guarantee a magnetic force sufficient to control a high hydraulic pressure and a high flow rate and to guarantee a long stroke, thereby enhancing the overlap (an amount of closed inflow port/discharge port).

On the other hand, first and second bushings 292b are separated from each other and are individually pressed into the second core hollow portion of the core 260 and the second yoke hollow portion of the yoke 270. The first and second bushings 292b smooth the vertical reciprocation of the plunger 240 and minimize the lateral movement and the inclination of the plunger 240 by excluding the interference corresponding to the degree of processing of the yoke 270, the core 260, and the plunger 240. A positioning member 290 is disposed in the second core hollow portion of the core 260.

The solenoid valve according to the invention may further include a guide 215 causing the core 260 and the yoke 270 to form a body.

The guide 215 is formed of a hollow cylindrical shape so as to surround parts of the core 260 and the yoke 270. To mount the guide 215, end jaws for mounting the guide 215 are formed in the outer circumferences of the core 260 and the yoke 270, as shown in FIG. 6.

In this way, when the solenoid valve according to the invention includes the guide 215, the core 260 and the yoke 270 can be caused to form a body, thereby preventing the deformation of the solenoid valve for a transmission with an application of an external force and improving the durability thereof.

The rod 250 is fixed to the center of the plunger 240 and the top end thereof comes in continuous contact with the bottom end of the spool 120. The rod 250 moves through the second core hollow portion of the core 260 and the second yoke hollow portion of the yoke 270.

In the solenoid valve for a transmission according to the first embodiment of the invention having the above-mentioned structure, as shown in FIG. 7, first, when power is applied to the coil 220, the core 260, the yoke 270, and the plunger 240 are magnetized and thus the plunger 240 moves to the core 260. At this time, the rod 250 fixed to the core 260 moves together with the plunger 240. At the time of the initial movement of the rod 250, the rod 250 and the plunger 240 slowly move upward up to a specific current value and thus the control pressure through the control port 113b is not applied to the clutch. That is, since any external force other than the magnetic force is not applied while the rod 250 is moving up, no excessive control pressure is applied to the clutch through the control chamber 113a and the control port 113b. Accordingly, it is possible to minimize the leakage of the hydraulic pressure. Thereafter, as the magnetic force increases over the specific current value, the rod 250 and the plunger 240 move upward to open the supply port and thus the control pressure in the control chamber 113a increases. The increased control pressure is partially applied to the feedback chamber 112 via the feedback flow channel 119 and a downward force is accordingly applied to the spool 120 by the feedback pressure in the feedback chamber 112 and the spring force of the spring 130. At this time, an upward force is applied to the spool 120 by the magnetic force. That is, at the time of the upward movement of the spool 120, the control pressure is linearly controlled with the balance of the upward force and the downward force.

As described above, the solenoid valve for a transmission according to this embodiment includes the plunger, the core, and the yoke being separated from the core by 1.5 mm to 2.5 mm and having three widths, thereby guaranteeing the magnetic force sufficient to control a high pressure and a high flow rate.

A solenoid valve for a transmission according to a second embodiment of the invention will be described with reference to the accompanying drawings. The same description as made for the solenoid valve for a transmission according to the first embodiment of the invention will not be repeated or will be made in brief.

FIG. 8 is a sectional view illustrating the solenoid valve for a transmission according to the second embodiment of the invention. FIG. 9 is an enlarged sectional view of Area B in FIG. 8. FIG. 10 is a diagram illustrating output waveforms in the solenoid valve for a transmission according to the second embodiment of the invention and a solenoid valve for a transmission according to the related art.

As shown in FIG. 8, the solenoid valve for a transmission according to the second embodiment of the invention includes a valve section 100 and a solenoid section 200 driving the valve section 100. The solenoid section 200 of the solenoid valve for a transmission according to the second embodiment of the invention is the same as the solenoid valve for a transmission according to the first embodiment of the invention and thus description thereof is not repeated. Accordingly, since the solenoid section 200 can be used in common at the time of manufacturing the NH-type solenoid valve for a transmission and the NL-type solenoid valve for a transmission according to the first and second embodiments of the invention, any particular manufacturing line need not be provided, thereby reducing the manufacturing cost. It is also possible to stabilize the performance of the manufacture solenoid valves for a transmission by using the same components (solenoid section).

The valve section 100 according to this embodiment is disposed on a valve body (not shown) side having plural flow channels, serves to supply a fluid to a clutch (not shown) while applying a predetermined control pressure to the fluid supplied from a hydraulic pressure supply source, and includes a hollow holder 110, a spool 120 movably disposed in the holder 110, and a spring 130 and a pressure adjusting screw 140 disposed on the top of the spool 120.

The spool 120 is movable in the hollow holder 110 and one or more annular grooves are formed on the outer peripheral surface thereof. In this embodiment, a first annular groove 121a and a second annular groove 121b having a width greater than that of the first annular groove 121a are sequentially formed as such annular grooves.

The holder 110 has a hollow shape in which the movement of the spool 120 is guided. A feedback chamber 112, a supply chamber 115a, a control chamber 113a, and a discharge chamber 117a are sequentially formed from up to down in the spool 120. Here, an opening 118, a supply port 115b, a control port 113b, and a discharge port 117b are formed at ends of the feedback chamber 112, the supply chamber 115a, the control chamber 113a, and the discharge chamber 117a, respectively. A first auxiliary discharge chamber 111a and a first auxiliary discharge port 114a formed at one end thereof are formed on the top of the feedback chamber 112. A second auxiliary discharge chamber 111b and a second auxiliary discharge port 114b formed at one end thereof are formed on the bottom of the discharge chamber 117a. In this embodiment, as shown in FIG. 9, the feedback flow channel 119 is formed with a diameter R of 0.5 mm to 1.5 mm and a thickness T of 1.5 mm to 2.5 mm, thereby enhancing the overlap.

According to this embodiment having the above-mentioned structure, as shown in FIG. 10, it is possible to provide a solenoid valve for a transmission in which a response speed is enhanced in comparison with the solenoid valve for a transmission according to the related art and the influence of undershoot can be removed. Accordingly, it is possible to prevent an instantaneous variation in clutch force to prevent the shifting shock and to improve the durability of the automatic transmission.

As described above, since the solenoid valve for a transmission according to this embodiment includes the plunger, the core, and the yoke being separated from the core by 1.5 mm to 2.5 mm and having three widths, it is possible to guarantee the magnetic force sufficient to control a high pressure and a high flow rate. In addition, since the feedback flow channel 119 has a diameter of 0.5 mm to 1.5 mm and a thickness, that is, a length, of 1.5 mm to 2.5 mm, it is possible to enhance the overlap.

While the invention has been described with reference to the accompanying drawing and the exemplary embodiment, it will be understood by those skilled in the art that the invention can be modified in various forms without departing from the technical spirit of the invention taught from the appended claims.

Claims

A solenoid valve for a transmission comprising a solenoid section and a valve section made to work by the solenoid section,

wherein the solenoid section includes:

a core;

a yoke separated from the core by a predetermined gap and having a first width, a second width, and a third width, which are different from each other, sequentially in a direction getting close to the core in a plane parallel to a longitudinal direction; and

a plunger made to reciprocate by the core and the yoke so as to cause the valve section to operate.
The solenoid valve according to claim 1, wherein the first width is greater than the second width and the second width is greater than the third width.
The solenoid valve according to claim 2, wherein the yoke includes a first surface and a ninth surface forming the first width, a fourth surface and the ninth surface forming the second width, and a sixth surface and the ninth surface forming the third width in the sectional plane in the longitudinal direction,

wherein a second surface which is an oblique plane and a third surface which is a vertical plane are formed between the first surface and the fourth surface,

wherein a fifth surface which is an oblique plane is formed between the fourth surface and the sixth surface, and

wherein a seventh surface which is an oblique plane and an eighth surface which is connected to an end of the ninth surface and which is a vertical plane are formed at an end of the sixth surface.
The solenoid valve according to claim 1, wherein the predetermined gap between the yoke and the core is in the range of 1.5 mm to 2.5 mm.
The solenoid valve according to claim 1, wherein the valve section includes:

a hollow holder having one or more chambers and ports formed therein; and

a spool having one or more annular grooves and vertically reciprocating in the holder by the solenoid section.
The solenoid valve according to claim 5, wherein the holder has a discharge chamber, a control chamber, a supply chamber, and a feedback chamber which are sequentially formed toward the solenoid section, and

wherein the spool has a first annular groove and a second annular groove having a width smaller than that of the first annular groove, which are sequentially formed toward the solenoid section.
The solenoid valve according to claim 5, wherein the holder has a feedback chamber, a supply chamber, a control chamber, and a discharge chamber which are sequentially formed toward the solenoid section, and

wherein the spool has a first annular groove and a second annular groove having a width greater than that of the first annular groove, which are sequentially formed toward the solenoid section.
The solenoid valve according to claim 6 or 7, further comprising:

a feedback flow channel formed in the feedback chamber of the holder;

a supply port formed at one end of the supply chamber of the holder;

a control flow channel formed in the control chamber of the holder;

a control port formed at one end of the control chamber of the holder; and

a discharge port formed at one end of the discharge chamber of the holder.
The solenoid valve according to claim 8, wherein the feedback flow channel is connected to the control flow channel, and

wherein the feedback flow channel has a diameter of 0.5 mm to 1.5 mm and a thickness of 1.5 mm to 2.5 mm.
The solenoid valve according to claim 8, further comprising a filter mounted on at least one of the supply port and the control port.
The solenoid valve according to claim 10, wherein a filter mounting groove is formed in at least one of the supply port and the control port, and

wherein mounting jaws to be mounted on the filter mounting groove are formed at ends of the filter.
The solenoid valve according to claim 1, further comprising a guide disposed to surround the outer circumferences of the core and the yoke and to allow the core and the yoke to form a body.
The solenoid valve according to claim 12, wherein end jaws are formed in the outer circumferences of the core and the yoke, and

wherein the guide is disposed in the end jaws.