JP2000320555A - Shaft assembly and valve mechanism provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the shaft assembly suferior in durability and valve mechanism using it, which can reduce the wear of the shaft come into question, when a rolling bearing is adopted as the bearing for supporting the shaft. SOLUTION: This valve mechanism has at least a rolling bearing 28 and a plunger 24, supported by the rolling bearing 28, relatively moving with respect to the rolling bearing 28 in an axial direction. The plunger 24 has a story structure, including a super hard compound layer 52 which contains a nitride and a diffused layer 54 of N atoms inside as a hardened layer 50 nitrided the surface, in the order heading for from the surface of a plunger 24 to the inside and in the order heading for from the surface of the shaft to the inside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a shaft assembly and a valve mechanism provided with the same.

[0002]

2. Description of the Related Art As a valve mechanism, for example, a solenoid valve is configured such that a valve for opening and closing a flow path in a valve body is driven by a plunger passed through a central insertion hole of a coil bobbin. Here, the plunger moves in the axial direction by controlling the energization of the coil wound around the coil bobbin to open and close the valve. In such a case, in the conventional solenoid valve, a sliding bearing is used as a bearing for supporting the plunger in the central insertion hole of the coil bobbin. By the way, when the plunger is supported by a sliding bearing, the frictional resistance of the plunger from the sliding bearing which is exerted when the valve is opened and closed at a high speed is increased, which greatly affects the high-speed control performance of the plunger. Therefore, the inventor has considered using a rolling bearing as a bearing in order to eliminate or reduce the frictional resistance described above. This is because the rolling element of the rolling bearing comes into rolling contact with the plunger.

[0003]

However, austenitic stainless steel is used for the plunger due to its necessity of being a non-magnetic material, but the hardness cannot be improved by heat treatment. Therefore, there is a problem that the surface hardness of the plunger which comes into contact with the rolling element is easily worn (fretting phenomenon) because the surface hardness is lower than that of the rolling element.
In addition, there is a problem that the wear of the valve increases as the opening / closing speed of the valve increases and the number of times of opening / closing increases, and the degree of progress increases, and the durability of the valve rapidly decreases significantly.

[0004] Such a problem is not a problem peculiar to a valve mechanism such as a solenoid valve, but, in short, a problem caused when a rolling bearing is arranged as a bearing for supporting a shaft relatively moving in the axial direction. It is.

[0005] Therefore, the present invention provides a shaft assembly which can reduce wear of the shaft, which is a problem when a rolling bearing is employed as a bearing for supporting the shaft in such a structure, and has excellent durability, and a valve using the same. Providing a mechanism is an issue to be solved.

[0006]

A shaft assembly according to the present invention has at least a rolling bearing and a shaft supported by the rolling bearing and moving relative to the rolling bearing in the axial direction, wherein the shaft is , Characterized by having a cured layer subjected to a nitriding treatment on the surface.

Preferably, in this shaft assembly, the hardened layer includes, in order from the surface of the shaft to the inside, a super-hard compound layer containing nitride and a diffusion layer of N atoms inside. It has a hierarchical structure.

Preferably, in the shaft assembly, the hardened layer is formed of a soft sulfur layer, an ultra-hard and dense nitride compound layer, and a relatively hard nitride diffusion layer in the order from the surface of the shaft toward the inside. It has a hierarchical structure including layers.

Preferably, in the shaft assembly, the rolling bearing is formed of a linear ball bearing, and the ball bearing has an outer ring slidable relative to the shaft, A plurality of rolling elements interposed between the shaft and the shaft.

In short, according to the present invention, since the shaft surface has the hardened layer subjected to the nitriding treatment, the abrasion by the rolling elements of the rolling bearing is reduced, resulting in a shaft assembly having excellent durability.

[0011] A valve mechanism according to the present invention is characterized in that any one of the shaft assemblies, a valve provided at one end of a shaft included in the shaft assembly, a valve body having a passage opened and closed by the valve, and a device for driving the shaft. A shaft drive mechanism for opening and closing the passage of the valve body by the valve.

In short, in the present invention, a shaft having a hardened layer subjected to a nitriding treatment on the shaft surface is used. Therefore, even if a rolling bearing is used to support the shaft, the shaft is not moved when the shaft and the rolling bearing move relative to each other. Since the sliding property between the surface and the rolling element of the rolling bearing is improved, fretting hardly occurs. As a result, the wear of the shaft is reduced, and the responsiveness of the rolling bearing, which is an advantage of the rolling bearing, is improved, for example, the relative movement of the shaft or the bearing is increased.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. In the present invention, the valve mechanism will be described as applied to a solenoid valve, but the present invention is not limited to this. The shaft assembly is also applied to this solenoid valve, but is not limited to this. In short, it is applied to all those having a structure in which rolling bearings are arranged as bearings for supporting shafts that move relatively in the axial direction. can do.

A solenoid valve incorporating a shaft assembly according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a front sectional view of a solenoid valve, FIG. 2 is a front view showing a plunger as a shaft and a linear ball bearing as a rolling bearing for supporting the plunger, and FIG. FIG. 4 is a cross-sectional view of the plunger of FIG.

First, referring to FIG. 1, reference numeral 2 denotes a valve body. The valve body 2 has a structure in which a fluid passage 4 is provided, and a fluid flowing from one of the sides in the fluid passage 4 flows out to the other side. The valve body 2 also
It has a plunger insertion port 6. Reference numeral 8 denotes a member for mounting a plunger (shaft) driving mechanism described below, and the mounting member 8 is fixed to the outer periphery of the valve body 2.
Reference numeral 10 denotes a casing, and the casing 10 is fixed on the mounting member 8. 12 is a bobbin with a coil 14. Each end of the coil 14 is a pair of leads 1
Each of the leads 16 is connected to one end of the casing 6, and the other end of each of the leads 16 is drawn out of an opening 18 of the casing 10. The coil 14 can be energized via the lead 16. The bobbin 12 has an axial insertion hole 2 at the center.
Has zero. At the upper end of the bobbin 12, a suction member 22 made of a magnetic material that sucks the plunger by magnetic force is mounted. The center of the suction member 22 protrudes downward, and the protruding portion enters the insertion hole 20 of the bobbin 12. A plunger 24 is inserted through the insertion hole 20. The lower end side of the plunger 24 faces the inside of the fluid passage 4 through the plunger insertion opening 6 of the valve body 2.
The lower end of the plunger 24 constitutes a valve 24a. The plunger 24 has a spring engaging portion 24b
Having. The spring locking portion 24b and the mounting member 8
And a compression spring 26 interposed therebetween. The compression spring 26 urges the plunger 24 downward. At the upper end of the plunger 24, a to-be-sucked member 26 made of a magnetic material that is attracted to the attraction member 22 by magnetic force is fixed. Inner wall of insertion hole 20 of bobbin 12 and plunger 24
A linear ball bearing 28 as an example of a rolling bearing is mounted between the outer peripheral wall and the outer peripheral wall.

The linear ball bearing 28 will be described with reference to FIGS.

The bearing 28 has an outer ring 30, a ball 32 as a rolling element, and a retainer 34. 36 is a ring. The plunger 24 is provided with axial linear grooves 38 extending along the entire length at six locations on the outer peripheral surface.
The outer race 30 has grooves 4 of a load circulation ball train and a no-load circulation ball train at radially opposed linear grooves 38 of the plunger 24 at six circumferential positions in an axially intermediate region of the inner peripheral surface thereof.
0 and 42 are provided. The retainer 34 has a cylindrical shape curved so as to extend along a part of the inner peripheral surface of the outer ring 30. Both end portions are supported by the ring 36.
In the axially intermediate region of the retainer 34, a total of six horizontally long annular grooves 44 are provided in the circumferential direction when viewed in plan. One straight portion 44a along the axial direction of the annular groove 44 has a bottom penetrated and has no bottom, and the other straight portion 44b has a bottom.

Two opposing linear grooves 38 and 40 on the side of the plunger 24 and the outer ring 30 are paired to form a total of six load ball transfer paths 46. In the ball transfer path 46, the bottomless straight portion 4 of the annular groove 44 of the cage 34 is provided.
4a is located. Further, the groove 42 of the outer ring 30 and the retainer 34
And the straight portion 44b with the bottom of the annular groove 44 constitutes a pair to form a total of six no-load ball circulation paths 48. Each of the six ball transfer paths 46 and each of the six ball circulation paths 48 adjacent to the six ball transfer paths 46 are formed in the annular groove 4 of the cage 34.
4 are connected to each other one by one along the circumferential direction, thereby constituting a ball circulation circuit. Therefore, the balls 32 are rolled and circulated between the ball transfer path 46 and the ball circulation path 48 with the relative axial sliding operation of the plunger 24 and the outer ring 30.

In the above configuration, when power is not supplied to both ends of the coil 14 via the lead 16, the plunger 24 moves downward by the urging force of the compression spring 26, and the valve portion 24a at the lower end of the plunger 24 is Is closed. When both ends of the coil 14 are energized, the plunger 24 moves upward as a result of the attraction member 22 at the upper end being attracted by the attraction member 22 against the urging force of the compression spring 26, and as a result The valve portion 24a at the lower end opens the fluid passage 4 of the valve body 2.

In such a structure, when the plunger 24 moves up and down, the outer peripheral surface of the plunger 24 comes into contact with the ball 32 which is a rolling element of the bearing 28. Therefore,
The surface of the plunger 24 is worn by contact with the ball 32. Therefore, the embodiment is characterized in that a hardened layer of non-magnetic and high hardness (about Hv1000) described with reference to FIGS. 5 and 6 is formed on the surface of the plunger 24 in order to reduce the wear. Have.

Hereinafter, the formation of the cured layer will be described with reference to FIGS.

(1) The case where the surface of the plunger 24 is subjected to soft nitriding to form the first hardened layer 50 as shown in FIG. 5 will be described.

That is, a plunger 24 is prepared from JIS standard SCM415 as a raw material, and the outer shape of the plunger 24 is adjusted through cold forging, turning, raw grinding, roll forming and the like. The plunger 24 is set in a chamber having an airtight structure, and two kinds of a fluorine gas and a nitriding gas are separately supplied in a vacuum with a time lag. NF ₃ , BF
₃ , a gas obtained by combining a fluorine source component consisting of CF ₄ , HF, SF ₆ , or F ₂ alone or in a mixture with an inert gas such as N ₂ . For example, nitrogen trifluoride (NF
₃ ) A mixture of nitrogen and the like is preferably used. From the viewpoint of the effect, the fluorine source component such as NF ₃ is 0.05% to 20%.
% (Based on weight, the same applies hereinafter), preferably a concentration within the range of 3% to 5%. Examples of the nitriding gas include a gas composed of NH ₃ alone or a mixed gas composed of NH ₃ and a carbon source (for example, RX gas).

Here, first, a fluorine gas is supplied into the chamber, and the temperature is set at 300 ° C. to 400 ° C., and is maintained for 10 minutes to 120 minutes. As a result, oxides and the like on the surface of the plunger 24 are removed and purified, and at the same time, are replaced with a metal fluoride film. At this time, since the metal fluoride film formed on the surface is a passive film, it prevents the adsorption and oxidation of oxygen to the surface and prevents the formation of oxide until the next nitriding treatment.

Next, a nitriding gas is supplied into the chamber,
The temperature is in the range of 480 ° C. to 700 ° C. and is maintained for 0.5 to 5 hours. Thereby, the first hardened layer 50 is formed on the surface of the plunger 24. At this time, plunger 2
The metal fluoride film on the surface of No. 4 becomes an activation film, and nitrogen is easily and deeply permeated and diffused into the metal in the nitriding treatment.

Thereafter, cooling is performed by oil cooling or air cooling over a required time. Since the plunger 24 is held in the nitrogen gas until the cooling is completed, no oxide is generated on the surface. As shown in FIG. 3, the first hardened layer 20 thus formed is formed from the surface of the plunger 24 toward the inside, such as CrN, Fe ₂ N, Fe ₃ N, and Fe ₄ N.
An ultra-hard compound layer 52 containing a nitride such as that described above, and a diffusion layer 54 of N atoms in the interior.

The surface roughness of the first cured layer 20 is determined by the surface roughness of the target product before it is formed (center line average roughness Ra =
0.7 μm to 1.0 μm, ten-point average roughness Rz = 4.0 μ
m to 7.0 μm, maximum height Rmax = 4.5 μm to 7.
5 μm). By the way, the first
When the cross section of the cured layer 20 was observed with an electron microscope at a magnification of 400, it was found that the average particle size was 1 μm or less, and it was dense and smooth.

It should be noted that the hardness of the surface of the plunger 24 by a simple thermosetting treatment and the hardness of the first
Compared with the hardness of the plunger 24 surface at 0, the Vickers hardness [Hv] is 800 to 10 in the present embodiment.
00 (test load: 50 gf), which is equivalent to or higher than the thermosetting product. Further, the friction coefficients of the first cured layer 20 of the present embodiment and the cured layer obtained by the thermal curing treatment are 0.24 and 0.
54, which is better in this embodiment, which is less than half.

(2) Next, the formation of the second hardened layer 56 on the surface of the plunger 24 by nitrosulphurizing will be described with reference to FIG.

First, the cold forged plunger 24 is set in a chamber having an airtight structure. Thereafter, the inside of the chamber is evacuated, and a required reaction gas is supplied into the chamber. As a reaction gas, a mixture of gases having carburizing, nitriding, and sulfurizing properties, that is, CO ₂ + (NH ₃ +
N ₂ ) + H ₂ S is used.

Here, the ambient temperature in the chamber for the curing treatment is 480 ° C. to 700 ° C. (550 in this specific example).
° C), and the holding time of the ambient temperature is 0.5 to 5 hours (120 minutes in this specific example). Then, the chamber is cooled by oil cooling or air cooling over a required time.

As a result, first of all, impurity factors such as an oxide film inevitably present on the surface of the plunger 24 are removed by the reaction gas, particularly the sulfurizing gas (H ₂ S). Surface is exposed. Subsequently, the N component of the nitriding gas quickly and deeply penetrates and diffuses into the plunger 24 to form the second hardened layer 56. The depth of the second hardened layer 56 can be controlled by appropriately setting the processing temperature and the holding time. Second cured layer 56
Are F in order from the surface side of the plunger 24 to the inside.
Relatively soft sulfurized layer 58 containing eS as a main component, Fe _2-3
It has a hierarchical structure including an ultra-hard and dense nitride compound layer 60 containing N as a main component and a relatively hard nitrided diffusion layer 62 in which N atoms are diffused into the plunger 24.

As described above, the processing temperature for forming the second hardened layer 56 is lower than that of the thermosetting processing, so that the surface of the plunger 24 is hardly distorted. Incidentally, the surface roughness of the second cured layer 56 is determined by the surface roughness of the target product before it is formed (center line average roughness Ra = 0.7 μm).
１．０1.0 μm, ten-point average roughness Rz = 4.0 μm to 7.0
μm, the maximum height Rmax = 4.5 μm to 7.5 μm). Thus, the second cured layer 5
Since the dimensional change due to thermal strain can be suppressed in the process of forming 6, it is not necessary to polish the surface of the plunger 24 after this processing.

As described above, the surface of the plunger 24 is first hardened by cold forging, and further hardened by the subsequent hardening treatment. For this reason, the plunger 24
Has improved abrasion resistance and seizure resistance. In addition, since the hardening treatment is performed by the sulphonitriding treatment, the nitrocarburizing treatment or the salt bath quenching, the distortion of the plunger 24 can be avoided in this treatment process.

If such a nitrosulphurizing treatment is performed,
Since the second hardened layer 56 is formed by removing the oxide film inevitably existing on the surface of the plunger 24, heat treatment can be performed at a very low temperature as compared with a general hardening process. 24 distortions are avoided. For this reason, the manufacturing cost can be reduced, for example, the labor for removing the distortion by polishing as in the related art can be omitted.

As described above, in the present embodiment, the present invention is applied to the plunger 24 of the solenoid valve. However, the present invention is not limited to this. Some axis moves in the axial direction, and between this axis and another member. The present invention can be applied to all cases where a rolling bearing is arranged.

In the above-described embodiment, the linear ball bearing 28 is used as an example of the rolling bearing. However, the ball of the linear ball bearing 28 may not be circulated. A thrust ball bearing may be used.

[0038]

As described above, according to the present invention, at least a rolling bearing and a shaft supported by the rolling bearing and relatively moving in the axial direction with respect to the rolling bearing are provided. Since it has a hardened layer which has been subjected to a nitriding treatment, wear of the rolling elements of the rolling bearing is reduced, resulting in a shaft assembly having excellent durability.

In addition, even when a rolling bearing is used to support the plunger as a shaft, the wear of the plunger by the rolling elements of the rolling bearing is greatly reduced, resulting in excellent durability and responsiveness. Valve mechanism.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a solenoid valve according to an embodiment of the present invention.

FIG. 2 is a front view of the upper half longitudinal section of the shaft assembly of FIG. 1;

FIG. 3 is a cross-sectional end view of the shaft assembly of FIG. 1;

FIG. 4 is a sectional view of a plunger of the shaft assembly of FIG. 1;

FIG. 5 is a sectional view of a main part of a plunger for explaining formation of a first hardened layer.

FIG. 6 is a sectional view of an essential part of a plunger for explaining formation of a second hardened layer.

[Explanation of symbols]

 2 valve body 4 fluid passage 6 plunger insertion opening 8 mounting member 10 casing 12 bobbin 14 coil 16 lead 20 plunger insertion hole 22 plunger suction member 24 plunger 26 spring 28 linear ball bearing (rolling bearing) 50 first hardened layer 56 second Hardened layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H106 DA23 DB02 DB12 DB23 DB32 DC02 DC17 DD02 EE30 GA16 GA22 3J104 AA03 AA23 AA37 AA63 AA69 AA74 AA76 BA05 CA20 DA06

Claims (5)

[Claims] 1. A rolling bearing, and at least a shaft supported by the rolling bearing and axially moving relative to the rolling bearing, wherein the shaft has a hardened layer on its surface that is nitrided. A shaft assembly, characterized in that: 2. The shaft assembly according to claim 1, wherein the hardened layer is arranged in the order from the surface of the shaft to the inside.
A shaft assembly having a hierarchical structure including a superhard compound layer containing nitride and a diffusion layer of N atoms inside. 3. The shaft assembly according to claim 1, wherein the stiffening layer is arranged in the order from the surface of the shaft to the inside.
A shaft assembly having a hierarchical structure including a soft sulfurized layer, an ultra-hard and dense nitride compound layer, and a relatively hard nitrided diffusion layer. 4. The shaft assembly according to claim 1, wherein said rolling bearing comprises a linear ball bearing, and said ball bearing is slidable relative to said shaft. And a plurality of rolling elements interposed between the outer ring and the shaft. 5. The shaft assembly according to claim 1, a valve provided at one end of a shaft of the shaft assembly, a valve body having a passage opened and closed by the valve, and driving the shaft. And a shaft drive mechanism for opening and closing the passage of the valve body by the valve.