Patent Description:
A solenoid valve for water(or water inlet valve) functions to control supply or cut off of water source, see document <CIT>. Since water has a certain pressure during operation, it can be designed as a packless pilot-operated solenoid valve for water. <FIG> shows the structure of a solenoid valve for water that is currently more commonly used, including an plastic-sealed layer <NUM> for plastic-sealing a coil winding, a magnetic yoke <NUM> mounted on the outside of the plastic sealed layer, a plug <NUM>, a water inlet <NUM> and a water outlet <NUM>.

<FIG> shows a solenoid valve for water consisting essentially of two parts, a pilot valve and a primary valve. When a winding <NUM> is not energized, a movable iron core <NUM> falls due to the self-weight and the reaction force of the return spring, and closes a flow-through hole <NUM> of a primary valve plug <NUM>, so that the water entering the upper cavity of the valve plug from a balanced hole <NUM> cannot leak out, and due to the difference in effective bearing areas on and below the valve diaphragm, a pressure difference is formed, so that the valve plug diaphragm is pressed against the primary valve seat, and the valve is closed. When the winding <NUM> is energized, the magnetic attraction draws the movable iron core <NUM> up, and the water in the upper cavity <NUM> of the valve plug is discharged to an outlet of the valve through the flow-through hole <NUM>. Since the flow capacity of the flow-through hole is designed to be much greater than the flow capacity of the balanced hole <NUM>, a sufficient pressure loss is generated on the balanced hole <NUM> by the water flow, the pressure in the upper cavity <NUM> of the valve plug sharply decreases, while the pressure in the lower cavity <NUM> of the valve plug maintains the same as the pressure of the inlet, so that the pressure difference between the upper and lower sides of the valve plug diaphragm causes the valve plug diaphragm to bulge upwards, the valve is opened.

The major problem of the solenoid valve for water shown in <FIG> is that a water-isolating sleeve <NUM> needs to be separately manufactured, and the manufactured water-isolating sleeve is inserted into the magnetic conductive inner sleeve by means of assembly, so the water-isolating sleeve <NUM> installed in a middle hole of a coil rack <NUM> needs to have a certain thickness in order to withstand the pressure impact when the valve is closed and the possible structural damage during mechanical assembly, resulting in that the non-working air gap of the existing solenoid valve for water is greater than <NUM>, thus requiring more electromagnetic force to make the movable iron core act; in addition, manufacturing the water-isolating sleeve separately increases the manufacturing cost.

In addition, since the yoke <NUM> is mounted to the outside of the plastic-sealed layer <NUM> of the plastic-sealed coil winding, the yoke <NUM> must be welded together with the magnetic conductive inner sleeve in order to fix the yoke to the coil rack via the magnetic conductive inner sleeve, which the welding process and manufacturing cost are increased.

The winding enameled wires of the solenoid valves for waters in the market all use copper wires, with a total amount of about <NUM>-<NUM>. Reducing the amount of copper wire is the most straightforward way to reduce cost. However, reducing the amount of copper wires will inevitably affect the performance of the solenoid valves for waters. By improving the magnetic circuit structure, the usage of copper wire can be reduced under the condition of maintaining or even improving the performance level of the water inlet valve, and the balance between performance and cost can be achieved, which is the problem to be solved by the invention.

It is an object of the present invention to provide a solenoid valve for water capable of elevating a electromagnetic force and an method thereof for enhancing a electromagnetic force acting on a movable iron core and simplifying a production process for manufacturing the solenoid valve for water and reducing a production cost. The invention is defined by independent claims <NUM>, <NUM> and respective dependent claims.

The present invention will be described in detail below with reference to the accompanying drawings and embodiments, so as to further understand the content, features and technical effects of the present invention.

Description of reference numerals: stator assembly with a water-isolating sleeve-<NUM>; primary plastic-sealed stator assembly-<NUM>; stator assembly <NUM>; coil rack-<NUM>; yoke positioning boss-<NUM>; magnetic conductive inner sleeve positioning ring-<NUM>; insert-<NUM>; electronic components-<NUM>; coil winding-<NUM>; yoke-<NUM>; yoke positioning groove-<NUM>; upper magnetic conductive inner sleeve-<NUM>; lower magnetic conductive inner sleeve-<NUM>; magnetic conductive inner sleeve glue passing hole-<NUM>; plastic-sealed layer-<NUM>; water-isolating sleeve-<NUM>; water-isolating sleeve base-<NUM>; inner cavity of water-isolating sleeve-<NUM>; magnetic conductive seat-<NUM>; magnetic conductive inner sleeve axial inner groove-<NUM>; magnetic conductive inner sleeve joint seam-<NUM>; return spring-<NUM>; movable iron core-<NUM>; flow-through hole plug rubber-<NUM>; valve plug-<NUM>; valve plug rubber-<NUM>; valve body <NUM>; mounting rack-<NUM>; pressure relief ring-<NUM>; rubber gasket-<NUM>; filter screen assembly-<NUM>; flow-through hole-<NUM>; valve plug upper cavity-<NUM>; valve plug lower cavity-<NUM>; balanced hole-<NUM>; water inlet-<NUM>; water outlet-<NUM>.

The present invention starts from the structure of a coil rack, a magnetic conductive inner sleeve, a water-isolating sleeve, a movable iron core and a magnetic conductive base, and enhance the electromagnetic suction force when a water inlet valve is started by improving a magnetic circuit structure , the wire consumption is reduced and the cost is reduced under the condition of meeting the minimum starting voltage requirement.

The magnetic circuit of the solenoid valve for water of the present invention is composed of a yoke, a magnetic conductive seat, an upper magnetic conductive inner sleeve, a movable iron core and a lower magnetic conductive inner sleeve.

<FIG> shows the relationship between load reaction force of the movable iron core and the stroke of the movable iron core, and the load reaction force characteristic acting on the movable iron core in operation is shown as curve <NUM> in <FIG>. In the F-S coordinate system, F is a load reaction force acting on the movable iron core, and S is a suction stroke of the movable iron core. The load reaction force is mainly composed of the force F1 of water acting on the movable iron core, the self-weight G of the movable iron core and the elastic force F2 of the spring. ,wherein F1 and F2 are significant and varied. When the movable iron core closes the flow-through hole, F1 is equal to the product of the water source pressure and the cross-sectional area of the flow-through hole, and point A in the figure corresponds to the closed valve state; at the initial stage of the movable iron core rising after the power-on, since the valve plug diaphragm also rises, the flow-through hole fails to be unblocked, the pressure of the upper cavity of the valve plug still has a downward action force on the movable iron core, but has been continuously reduced; the spring is then compressed and the spring force is intensified. Since F1 decreases faster than F2 increases, the first half of curve <NUM> decreases slowly. At point B, the valve plug diaphragm fully rises, the flow-through hole is unblocked, F1 completely disappears, and the load reaction force rapidly drops to the lowest point; thereafter, the movable iron core rises against F2, and the slope of the inclined line segment after point B is the elastic coefficient of the spring.

In order to adapt to the load reaction force characteristic, the electromagnetic suction force characteristic acting on the movable iron core is as shown in <FIG>. The relative positions of the upper magnetic conductive inner sleeve and the lower magnetic conductive inner sleeve and the movable iron core plays an important role in the specific effect of electromagnetic suction force. A working air gap exists between the movable iron core and the upper magnetic conductive inner sleeve, and a main non-working air gap is formed between the movable iron core and the lower magnetic conductive inner sleeve. Before the movable iron core is not sucked into the upper magnetic conductive inner sleeve, the magnetic potential mainly falls in the working air gap; the electromagnetic suction force includes the electromagnetic force generated by the leakage flux on the side surface of the movable iron core and the end surface suction force generated by the main magnetic flux; when the upper end surface of the movable iron core is close to the lower edge of the upper magnetic conductive inner sleeve, the effect of the end surface suction force is greater; the closer the upper end surface is to the lower edge of the upper magnetic inner sleeve, the greater the total electromagnetic suction force, and the maximum value is reached when the movable iron core is about to enter the upper magnetic conductive inner sleeve. After the movable iron core is sucked into the upper magnetic conductive inner sleeve, the length of the working air gap does not change, and the area of the air gap increases with the depth of the movable iron core, the working air gap magnetic quickly increases to a degree that can be compared with the non-working air gap magnetic conductance, so that the working air gap magnetic pressure drop decreases proportionally and the electromagnetic suction force thus decreases. The descending section of the electromagnetic suction force characteristic curve and the ascending section of the load reaction characteristic curve intersect at point C, the movable iron core is completed, and the solenoid valve for water is also conducted.

In view of the fact that the movable iron core must have a certain suction stroke, magnetic leakage exists in the gap between the upper magnetic inner sleeve and the lower magnetic inner sleeve, and the magnetic seat is installed in the upper magnetic inner sleeve, the present invention improves the magnetic circuit structure as follows:.

The specific numerical values are set as follows:.

As a result of the reduced diameter of the moving iron core, the noise generated by the attractive collision between the magnetized magnetic conductive seat and the moving iron core is also reduced when the coil winding is energized. The apertures of the water-isolating sleeve, the upper magnetic conductive inner sleeve and the lower magnetic conductive inner sleeve and the coil rack are reduced to accommodate the reduction of the diameter of the movable iron core. When the aperture of the coil rack is reduced, the copper wire consumption is reduced, the winding resistance is reduced and the current is increased under the condition that the number of winding turns and the wire diameter are unchanged, which improves the solenoid attraction and low voltage starting performance.

The present invention provides an implementation method of a solenoid valve for water capable of improving a electromagnetic suction force, which comprises:.

Referring to <FIG>, the valve body assembly of the solenoid valve for water of the present invention includes: a return spring <NUM> and a movable iron core <NUM> which are received in a water-isolating sleeve; a flow-through hole valve plug rubber <NUM>; a valve plug <NUM>; a valve plug rubber <NUM>; a valve body <NUM>, a mounting rack <NUM>, a pressure relief ring <NUM>, a rubber gasket <NUM>, and a filter screen assembly <NUM>, etc. Since these components of the valve body assembly of the solenoid valve for water are all components of an existing solenoid valve for water, and the connection relationship thereof is also substantially the same as that in the prior art, it falls within the prior art. For the sake of brevity, a detailed description of what is considered to be prior art is omitted.

According to the present invention, by setting the length of the movable iron core in the lower magnetic conductive inner sleeve in the initial position to be not less than <NUM>/<NUM> of a sum of the heights of the upper magnetic conductive inner sleeve and the lower magnetic conductive inner sleeve, so as to ensure that the magnetic conduction of the non-operating air gap is not too small, avoiding magnetic saturation of the iron core, and improving the ability of the solenoid valve for water to withstand a large impulse current impact.

Specific parameters of the present invention for achieving the above-mentioned improvement of the magnetic circuit structure include: the gap between the upper and lower magnetic conductive inner sleeves is between <NUM> and <NUM>; the diameter of the movable iron core is reduced from <NUM> to <NUM> ± <NUM>; the inner diameter of the upper magnetic conductive inner sleeve and the lower magnetic conductive inner sleeve is <NUM> ± <NUM>, the wall thickness is <NUM>, and the outer diameter is <NUM> ± <NUM>; the inner diameter of water-isolating sleeve is <NUM> ± <NUM>, and the outer diameter is <NUM> ± <NUM>; and the weight of the magnetic conductive seat is not less than <NUM>% of the weight of the movable iron core, so as to appropriately increase the magnetic conductive seat, increase the electromagnetic suction force, and enhance the reliability of valve suction.

Referring to <FIG>, the present invention can form a water-isolating sleeve inside the upper and lower magnetic conductive inner sleeves <NUM> and <NUM> by injecting plastic inside the upper and lower magnetic conductive inner sleeves <NUM> and <NUM> mounted in the coil assembly.

<FIG> show a specific process of forming a water-isolating sleeve inside the upper and lower magnetic conductive inner sleeves <NUM> and <NUM> according to the present invention.

As shown in <FIG>, an upper magnetic conductive inner sleeve <NUM> and a lower magnetic conductive inner sleeve <NUM> are mounted on a cavity on the coil assembly, and a magnetic conductive inner sleeve positioning ring <NUM> (see <FIG>) in a hole in the coil rack <NUM> defines the upper magnetic conductive inner sleeve <NUM> and the lower magnetic conductive inner sleeve <NUM> at a position capable of contacting the magnetic yoke <NUM>; then, the yoke positioning grooves <NUM> of the yoke <NUM> are engaged with the yoke positioning bosses <NUM> of the upper and lower end faces of the coil rack <NUM>, so that the yoke <NUM> is positioned on the coil rack <NUM> on the one hand and closely contacted and coupled with the upper and lower magnetic conductive inner sleeves <NUM> and <NUM> on the other hand, thereby forming the stator assembly <NUM> shown in <FIG>.

Compared with the prior art, the present invention can reduce the welding process of welding the yoke <NUM> to the upper and lower magnetic conductive inner sleeves, and can reduce one yoke. However, in the prior art, it is necessary to weld the upper magnetic conductive inner sleeve with one yoke, weld the lower magnetic conductive inner sleeve with the other yoke, and then butt-join the two yokes (there might be a quality problem that the butt joint cannot be achieved). Thus, according to the present invention, the steps can be reduced, the cost can be reduced, and the product quality can be improved.

In the present invention, the stator assembly <NUM> is used as a base or an insert, and plastic is injectied on the stator assembly <NUM> with a water-isolating sleeve, comprising:
by putting the stator assembly <NUM> shown in <FIG> into the mold and injecting plastic for the first time, the coil winding <NUM>, the yoke <NUM> and the electronic component <NUM> are wrapped with plastic, but the insert <NUM> and the hole in the coil rack <NUM> with the upper magnetic conductive inner sleeve <NUM> and the lower magnetic conductive inner sleeve <NUM> are exposed, thus forming the primary plastic-sealed assembly <NUM> shown in <FIG>;.

By putting the primary plastic-sealed assembly <NUM> into another mold and injecting plastic for the second time, the water-isolating sleeve <NUM> is formed on the hole in the coil rack <NUM> with the upper magnetic conductive inner sleeve <NUM> and the lower magnetic conductive inner sleeve <NUM>, so as to manufacture the integrated stator assembly <NUM> with water-isolating sleeve as shown in <FIG>.

<FIG> shows the structure of the integrated stator assembly <NUM> having a water-isolating sleeve. The yoke <NUM> is tightly fixed to the coil assembly by a plastic-sealed layer <NUM>, and the water-isolating sleeve <NUM> is injection molded on the inner walls of the upper and lower magnetic conductive inner sleeves <NUM> and <NUM>, so that the water-isolating sleeve <NUM> having a thickness of about <NUM> is formed in the hole of the coil rack, that is, the present invention reduces the thickness of the water-isolating sleeve <NUM> by the injection-plastic process. The present invention can greatly reduce the gap between the movable iron core <NUM> and the magnetic conductive inner sleeve, and increase the electromagnetic force acting on the movable iron core <NUM>, with respect to the water-isolating sleeve of <NUM> thick in the prior art.

In addition, in the second injection plastic, the base <NUM> of the water-isolating sleeve having external threads is also injection molded so that the integrated stator assembly <NUM> having a water-isolating sleeve can be screwed onto the valve body <NUM> having internal threads when assembling the solenoid valve for water, see <FIG>.

The magnetic conductive seat <NUM> is then mounted within the upper magnetic conductive inner sleeve <NUM> to form the plastic-sealed stator assembly shown in <FIG>.

<FIG> show the structure of the upper and lower magnetic conductive inner sleeves of the present invention. The upper magnetic conductive inner sleeve <NUM> and the lower magnetic conductive inner sleeve <NUM> of the present invention are cylindrical, and its wall is provided with a radial through-hole <NUM> for glue passing, and the inner surface of the cylinder wall is provided with an magnetic conductive inner sleeve axial groove <NUM> (for facilitating the flow of hot melt plastic during injection-plastic), and the magnetic conductive inner sleeve axial groove <NUM> communicates with the radial through-hole <NUM>. By injecting plastic oin the hole of the coil rack having the upper and lower magnetic conductive inner sleeves, the injected plastic used to form the water-isolating sleeve flows along the upper and lower magnetic conductive inner sleeve axial grooves <NUM> into the magnetic conductive inner sleeve through hole <NUM>, forming a root for positioning the water-isolating sleeve <NUM>, such that the water-isolating sleeve <NUM> is firmly secured to the upper and lower magnetic conductive inner sleeves <NUM>, <NUM> that have been positioned by the magnetic conductive inner sleeve positioning ring <NUM>.

In addition, the present invention may further provide a plurality of circumferential grooves (not shown) on the inner surfaces of the upper and lower magnetic conductive inner sleeves <NUM> and <NUM> for further fixing the water-isolating sleeve using the radial grooves when the water-isolating sleeve is plastic sealed.

<FIG> illustrate another embodiment of the present invention for forming a water-isolating sleeve. First, the upper magnetic inner sleeve <NUM>, the stopper <NUM> and the lower magnetic inner sleeve <NUM> are placed together (as shown in <FIG>). Second, the upper magnetic inner sleeve <NUM>, the stopper <NUM> and the lower magnetic inner sleeve <NUM>, which are placed together, are used as inserts for injecting plastic, so as to manufacture a water-isolating sleeve assembly including the water-isolating sleeve formed inside the upper magnetic inner sleeve and the lower magnetic inner sleeve (see <FIG>). Then, the water-isolating sleeve assembly is installed into the hole in the coil assembly and plastic is injected, thus forming the plastic-sealed stator assembly as shown in <FIG>.

Compared with a technology of "injection molding the upper and lower magnetic conductive inner sleeves as inserts together with the water jacket and the bobbin", the realization method of the water inlet solenoid valve of the present invention can greatly reduce the working air gap, because the water-isolating sleeve of the present invention is formed by injecting palstic in the hole of the coil rack, and a very thin water isolating sleeve can be formed. The technology of "injection molding the upper and lower magnetic inner sleeves as inserts together with the water jacket and the bobbin" is that "the magnetic inner sleeve, the water jacket and the coil rack are injection molded into an integrated part", so it is necessary to manufacture separate water jacket, coil rack and magnetic inner sleeve; Considering factors such as manufacturing process and strength, the water jacket must have a certain thickness, so that its thickness is greater than that of the water-isolating sleeve of the present invention which plastic is injected in the hole of the coil rack. In addition, the technology of "injection molding the upper and lower magnetic inner sleeves as inserts together with the water jacket and the bobbin" can not package the yoke, the coil winding, the insert, the coil rack, the magnetic inner sleeve and the water-isolating sleeve together to form an integrated stator assembly. The present invention also provides a solenoid valve for water with increasing electromagnetic suction force, made according to the above method, which comprises:.

Referring to <FIG>, the valve body assembly of the solenoid valve for water of the present invention includes: a return spring <NUM> and a movable iron core <NUM> which are received in a water-isolating sleeve; a flow-through hole valve plug rubber <NUM>; a valve plug <NUM>; a valve plug rubber <NUM>; a valve body <NUM>, a mounting rack <NUM>, a pressure relief ring <NUM>, a rubber gasket <NUM>, and a filter screen assembly <NUM>, etc..

According to the present invention, the upper end face of the movable iron core at the initial position is set as not lower than the upper edge of lower magnetic conductive inner sleeve and not higher than <NUM>/<NUM> of the distance from the upper edge of lower magnetic conductive inner sleeve to the lower edge of upper magnetic conductive inner sleeve, so as to enhance the electromagnetic suction force of the solenoid valve for water.

Moreover, according to the present invention, the water-isolating sleeve inside the upper and lower magnetic conductive inner sleeves is formed by injecting plastic on the inner surfaces of the upper and lower magnetic conductive inner sleeves.

Alternatively, the invention can also place the upper magnetic inner sleeve, the stopper and the lower magnetic inner sleeve together as an insert, and perform injection molding on them to form the water-isolating sleeve assembly which is installed in the hole of the coil assembly and includes water-isolating sleeve formed by injection molding on the inner surfaces of the upper magnetic inner sleeve and the lower magnetic inner sleeve.

On the other hand, the upper magnetic conductive inner sleeve <NUM> and the lower magnetic conductive inner sleeve <NUM> of the present invention are cylindrical, and its wall is provided with a radial through-hole <NUM> for glue passing. the inner surface of its wall is provided with an magnetic conductive inner sleeve axial groove <NUM>, and the magnetic conductive inner sleeve axial groove <NUM> communicates with the radial through-hole <NUM>. By injecting plastic in the hole of the coil rack having the upper and lower magnetic conductive inner sleeves, the injected plastic used to form the water-isolating sleeve flows along the upper and lower magnetic conductive inner sleeve axial grooves <NUM> into the magnetic conductive inner sleeve through hole <NUM>, forming a root for positioning the injection molded water-isolating sleeve <NUM>.

According to the experimental study of the inventor, the magnetic circuit structure of the solenoid valve for water is designed in such a size that, while not affecting the low-pressure starting performance of the valve, the consumables can be reduced and the cost can be reduced. The diameter of the movable iron core is reduced from <NUM> to <NUM> ± <NUM>; the inner diameter of the water-isolating sleeve is <NUM> ± <NUM>, the wall thickness is <NUM>, and the outer diameter is <NUM> ± <NUM>; the inner diameter of the upper and lower magnetic conductive inner sleeves is <NUM> ± <NUM>, the wall thickness is <NUM>, and the outer diameter is <NUM> ± <NUM>; the aperture in the hole in the coil rack is about <NUM>.

Since the water-isolating sleeve vibrates due to the action of the movable iron core during the operation of the valve, the coil rack needs to meet certain rigidity requirements to prevent damage. According to the provisions of <CIT> "Electrical automatic controllers for household and similar purposes" and <CIT> "Safety of electrical appliances for household and similar purposes", the magnetic yoke of water inlet valve is exposed and accessible to human hands. In order to meet the requirements for insulation, the skeleton wall thickness must be greater than <NUM>. The magnetic yoke of the water inlet valve of the present invention is plastic-sealed, which can't be touched by human hands, and the skeleton has no thickness requirement, and only needs to ensure the strength so as not to be deformed when winding, so that the thickness of the skeleton can be minimized.

Since the invention adopts the manufacturing process of water-isolating sleeve injection molding, the water-isolating sleeve is formed by injecting plastic on the stator assembly and is integrated with the coil rack, and the wall thickness of the coil rack is not limited by the national standard, the wall thickness of the hole in the coil rack is reduced from <NUM> to <NUM>, so that the coil diameter is further reduced, and the amount of copper wire is further reduced under the condition that the number of winding turns and the wire diameter are unchanged.

Moreover, as the movable iron core becomes smaller and lighter, when the coil winding <NUM> is energized, the noise generated by the attraction between the magnetized magnetic seat <NUM> and the movable iron core <NUM> also decreases.

It should be noted that the injection-molding process of the water-isolating sleeve used in the solenoid valve for water of the present embodiment is merely illustrative of the manufacturing process of the solenoid valve for water, and does not limit the magnetic circuit structure. The magnetic circuit structure improvement method of the present invention is effective for all solenoid valve for waters in enhancing the solenoid attraction force at start-up, reducing the wire consumption and reducing the noise generated by moving iron core suction under the condition of meeting the minimum start-up voltage requirements.

Claim 1:
A method of manufacturing a water inlet solenoid valve configured to enhance an electromagnetic suction force, comprising:
obtaining a plastic-sealed stator assembly by injecting plastic on a stator assembly (<NUM>), comprising:
mounting an upper magnetic conductive inner sleeve (<NUM>) and a lower magnetic conductive inner sleeve (<NUM>) in a hole (<NUM>) of a coil assembly;
injecting plastic on an inner surface of the upper magnetic conductive inner sleeve (<NUM>) and the lower magnetic conductive inner sleeve (<NUM>), configured to form a water-isolating sleeve (<NUM>) on the inner surface of the upper magnetic conductive inner sleeve (<NUM>) and lower magnetic conductive inner sleeve (<NUM>);
mounting a yoke (<NUM>) outside the coil assembly and connecting the yoke (<NUM>) with the upper magnetic conductive inner sleeve (<NUM>) and the lower magnetic conductive inner sleeve (<NUM>);
mounting a magnetic conductive seat (<NUM>) on an inner side of the water-isolating sleeve (<NUM>);
injecting plastic on the coil assembly and the yoke (<NUM>), configured to form a plastic-sealed layer (<NUM>) configured to cover the coil assembly and to tightly connect the yoke (<NUM>) with the upper magnetic conductive inner sleeve (<NUM>) and lower magnetic conductive inner sleeve (<NUM>);
assembling the plastic-sealed stator assembly (<NUM>) and a valve body assembly comprising a movable iron core (<NUM>) together to form the water inlet solenoid valve ;
wherein an upper end face of the movable iron core (<NUM>) at an initial position is slightly higher than an upper edge of the lower magnetic conductive inner sleeve (<NUM>) ;
wherein the upper end face of the movable iron core (<NUM>) at an initial position is set as not lower than the upper edge of lower magnetic conductive inner sleeve and not higher than <NUM>/<NUM> of the distance from the upper edge of lower magnetic conductive inner sleeve to the lower edge of upper magnetic conductive inner sleeve, so as to enhance the electromagnetic suction force of the solenoid valve for water.