JP2011174515A - Coil spring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coil spring which is low in cost and good in responsiveness to a temperature change, and its manufacturing method. <P>SOLUTION: The closed-end coil spring constituted of an alloy wire composed of a Ti-Ni based shape-memory alloy is characterized in that a ratio (d<SB>E</SB>/d) of the thickness d<SB>E</SB>(mm) of the tip of the alloy wire in the spring axial direction and the line diameter d(mm) of the alloy wire is 0.50 to 0.75 at one or both coil ends, and a ratio (D/d) of the average diameter D(mm) of a coil and the line diameter d(mm) of the alloy wire is not larger than 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coil spring, and more particularly, to a coil spring used for the purpose of controlling fluid temperature in a hot and cold water mixing faucet or the like.

  A shape memory alloy is an alloy that can be memorized by performing a predetermined heat treatment after it has been formed into a predetermined shape, and even when deformed by applying force, it is heated above a certain temperature (operating temperature). Then, it has the property of returning to the original shape. This is because the elastic modulus of the shape memory alloy varies greatly with temperature.

  In particular, a Ti—Ni-based shape memory alloy is an alloy applied in various technical fields. As an example of utilizing the property that the modulus of elasticity of the Ti—Ni-based shape memory alloy is high at high temperatures and low at low temperatures, there is control of fluid temperature such as a hot and cold water mixing tap.

  FIG. 1 is a diagram showing the mixing principle of a hot and cold water mixing faucet. As shown in FIG. 1, a hot and cold water mixing tap 100 includes a high temperature water hole 102, a room temperature water hole 101, a mixing chamber 108 connected to the high temperature water hole 102 and the room temperature water hole 101, and a mixing chamber. The shape memory alloy coil spring 103, a bias spring 104 made of stainless steel, and a spool valve 106 are disposed in the mixing chamber 108.

  When the temperature setting knob 107 is turned to set a predetermined temperature, the spool valve moves, each of the room temperature water hole 101 and the high temperature water hole 102 is opened by a predetermined amount, and the inside of the mixing chamber 108 is distributed in a predetermined distribution. To be introduced. At this time, if the temperature of the mixed water in the mixing chamber 108 becomes too high, the shape memory alloy coil spring 103 pushes the bias spring 104, so that the position of the spool valve moves and the flow path of the room temperature water hole 101 is widened. Therefore, lower the temperature of the mixed water. On the other hand, if the temperature of the mixed water in the mixing chamber 108 becomes too low, the shape memory alloy coil spring 103 is pushed into the bias spring 104, so that the position of the spool valve moves and the flow path of the high-temperature water hole 102 is widened. Therefore, raise the temperature of the mixed water. In this way, the temperature of the mixed water is controlled.

  For example, Patent Document 1 discloses an invention relating to an “automatic temperature control type hot water mixing tap” using a coil spring made of a shape memory alloy of Ti—Ni or Cu—Zn—Al.

A coil spring made of a shape memory alloy is usually formed into a desired coil shape by cold working and then subjected to a heat treatment in a temperature range of about 400 to 500 ° C. (hereinafter referred to as “shape memory heat treatment”). Remember the shape. At this time, one or both of the coil ends are ground for the purpose of stabilizing the sitting of the spring, and the thickness d _E (mm) of the tip end portion of the alloy wire in the spring axial direction is the wire diameter d of the alloy wire. Generally, the thickness is set to ¼ or less of (mm), that is, the ratio (d _E / d) is 0.25 or less.

  However, since frictional heat is generated at the coil end during the grinding process, if this is performed after the shape memory heat treatment, the shape memory alloy characteristics are adversely affected. In order to cause a shape defect such as opening of the winding part, it is necessary to perform a grinding process after the temporary heat treatment and then perform a shape memory heat treatment. In addition, after the grinding process, it is necessary to remove burrs generated during grinding.

  On the other hand, as a method of stabilizing the spring sitting without performing the grinding process, Patent Document 2 discloses a coil spring having a final end winding portion that is perpendicular to the center line of the spring and having a half or more turns of the coil. Yes.

Japanese Utility Model Publication No. 57-35567 Japanese Patent Laid-Open No. 2002-364691

  Patent Document 1 describes the use of a coil spring made of a shape memory alloy, but does not mention its specific shape. The invention described in Patent Document 2 is effective when the wire diameter d (mm) of the alloy wire is sufficiently thin with respect to the average diameter D (mm) of the coil, but as a spring for a mixed faucet. A generally used coil spring having a ratio (D / d) of 10 or less makes little sense.

  On the other hand, the coil spring made of a shape memory alloy has a quick response to changes in the ambient temperature, so temperature control with less overshoot (a phenomenon in which the water temperature exceeds the set water temperature and then the set water temperature) is becoming possible. Still, the occurrence of overshoot is not completely eliminated, and there is a demand for a coil spring that is more responsive to temperature changes.

  Accordingly, it is an object of the present invention to provide a coil spring that can be manufactured at low cost and that has good response to temperature changes, and a method for manufacturing the same, on the premise of grinding processing of the coil end.

The present inventors paid attention to the relationship between the processing heat generated when grinding the coil end of a coil spring made of a shape memory alloy and the shape collapse, and conventionally, the thickness d _E (mm) of the tip end portion of the alloy wire in the spring axial direction. Was examined until the end of the alloy wire was reduced to 1/4 or less of the wire diameter d (mm), that is, the ratio (d _E / d) was 0.25 or less. As a result, even if the tip shape of the alloy wire after the grinding process of the coil end is made somewhat thicker than the conventional one, it is possible to secure a stable spring sitting, and in doing so, the heat treatment process before the grinding process can be ensured. It has been found that it is possible to omit the deburring process after the grinding process, and to greatly simplify the manufacturing process.

  Furthermore, the present inventors can increase the contact area with the fluid as compared with the conventional shape as long as the coil spring has the tip shape as described above, and also has a housing (mixing) with a large heat capacity. In the case of a faucet, it was found that the contact area with the housing of the mixing chamber) can be reduced, so that the responsiveness to temperature changes can be improved.

  The present invention has been made on the basis of the above findings, and the gist thereof is a coil spring shown in the following (1) and a manufacturing method of the coil spring shown in the following (2).

(1) A closed-end coil spring composed of an alloy wire made of a Ti—Ni-based shape memory alloy, wherein one or both of the coil ends has a thickness d _E (mm) at the tip end of the alloy wire. ) And the wire diameter d (mm) of the alloy wire (d _E / d) is 0.50 to 0.75, and the average diameter D (mm) of the coil and the wire diameter d (mm) of the alloy wire A coil spring having a ratio (D / d) of 10 or less.

(2) A method for manufacturing a coil spring comprising the following steps 1 to 3.
Step 1: Cold working is performed on an alloy wire made of a Ti—Ni-based shape memory alloy, and the ratio (D / d) of the coil average diameter D (mm) to the wire diameter d (mm) of the alloy wire is 10 A step of obtaining a closed-end coil spring-shaped coil formed body,
Step 2: Continuously with Step 1, the obtained coil molded body is ground, and at one or both of the coil ends, the thickness d _E (mm) of the tip of the alloy wire in the spring axial direction and the wire of the alloy wire Obtaining a coil grinding body having a ratio (d _E / d) to a diameter d (mm) of 0.50 to 0.75, and
Step 3: A step of applying a shape memory heat treatment to the coil grinding body to obtain a coil spring.

  In addition, it is preferable that said Ti-Ni type | mold shape memory alloy has a composition which contains Ni of 50.0-51.2% by atomic percentage, and the remainder consists of Ti and an impurity. The Ti—Ni-based shape memory alloy is more preferably 3% or less in total with one or more elements selected from Cr, Fe and Co in atomic percentage.

  The coil spring of the present invention can be manufactured at a low cost because it can be ground without performing a temporary heat treatment in the manufacturing process, and it is not necessary to perform a deburring operation after grinding. Since the responsiveness to temperature changes is good, it is particularly suitable for use in a hot water / water mixing faucet and other fluid temperature control devices. The coil spring of the present invention can reduce the spring molding cost by about 25% compared to the conventional coil spring.

Diagram showing the mixing principle of the hot and cold water faucet Diagram showing the configuration of a closed-end coil spring (a) With grinding (b) Without grinding

  The coil spring of the present invention is a closed-end coil spring made of an alloy wire made of a Ti—Ni-based shape memory alloy.

  FIG. 2 is a diagram showing the configuration of a closed-end coil spring, in which (a) shows a configuration with grinding and (b) shows a configuration without grinding. As shown by reference numeral 3 in FIGS. 2A and 2B, the closed-end coil spring means a coil spring having a shape in which a terminal is in contact with an adjacent coil in the coil axis direction (JIS B 0103). .

In the present invention, as shown in FIG. 2 (b), a closed-end coil spring in which the tip end portion 4 is ground and the thickness thereof is smaller than the wire diameter of the alloy wire 2 is an object. Note that “d _E ”, “d”, and “D” shown in FIG. 2B are the thickness d _E (mm) of the tip end portion of the alloy wire in the spring axis direction and the wire of the alloy wire, which will be described below. It means the diameter d (mm) and the average diameter D (mm) of the coil.

<Ratio (d _E / d): 0.50 to 0.75>
When the ratio (d _E / d) of the thickness d _E (mm) of the tip of the alloy wire in the spring axis direction to the wire diameter d (mm) of the alloy wire is less than 0.50, the alloy wire is ground without being subjected to temporary heat treatment. In this case, loss of shape and generation of burr occur. On the other hand, when the ratio (d _E / d) exceeds 0.75, the sitting of the spring becomes unstable. If the sitting of the spring becomes unstable, it will be difficult to use as a product, and if it is tilted during shape memory processing, a product longer than the design free length will be generated. Therefore, the ratio (d _E / d) was set in the range of 0.50 to 0.75. If the coil spring has a ratio (d _E / d) in the range of 0.50 to 0.75, even if grinding of the coil end is performed without performing a temporary heat treatment, the loss of shape and burrs that occur during grinding are performed. Can be suppressed, and the sitting as a spring is also stable. Therefore, the provisional heat treatment step and the deburring step can be omitted, and the manufacturing cost can be greatly reduced. Further, if the ratio (d _E / d) is 0.50 or more, the amount of grinding is less than that of the conventional one, so that the contact area with the fluid becomes large and the contact area with the spring receiving jig having a large heat capacity. Therefore, the response of the temperature change of the fluid is improved.

<Ratio (D / d): 10 or less>
In the case of exceeding 10, since the sitting is stabilized by providing the end face with the end winding that goes straight to the spring shaft, the grinding process itself of the coil end is unnecessary. Therefore, in the present invention, the coil end grinding process for stabilizing the sitting of the spring is indispensable, and the ratio (D / d) of the average coil diameter D (mm) to the wire diameter d (mm) of the alloy wire. The target was a coil spring of 10 or less. There is no particular restriction on the lower limit of the ratio (D / d), but if the ratio (D / d) is too small, there is a possibility that the sitting may be slightly unstable when the ratio (d _E / d) is around 0.75. Therefore, the ratio (D / d) is preferably 4 or more.

<Chemical composition of Ti-Ni shape memory alloy>
The shape memory alloy used in the coil spring of the present invention is not particularly limited as long as it is a Ti—Ni alloy, but in particular, the atomic percentage (hereinafter, “%” for the content of each element of the shape memory alloy is “ , "Atomic percentage"), preferably contains 50.0 to 51.2% Ni with the balance being Ti and impurities. This is because, when the Ni content is less than 50% or more than 51.2% in terms of atomic percentage, the workability is deteriorated, and there is a possibility that folding may occur during coiling. In addition, an impurity means the component mixed by various factors of raw materials such as ores and scraps and manufacturing processes, and is allowed within a range that does not adversely affect the present invention.

The Ti—Ni-based shape memory alloy may further contain a total of 3% or less of one or more elements selected from Cr, Fe, and Co. It is because the change rate of the elastic modulus with respect to the operating temperature and temperature of a shape memory alloy can be adjusted by containing appropriate amounts of these elements. If the total content of these elements exceeds 3%, workability may be adversely affected. Accordingly, when one or more selected from these elements is contained, the total content is made 3% or less.
<Manufacturing method>

  Although there is no restriction | limiting in particular about the manufacturing method of a coil spring, It is preferable that the following processes 1-3 are included at least.

Step 1: Cold working is performed on an alloy wire made of a Ti—Ni-based shape memory alloy, and the ratio (D / d) of the coil average diameter D (mm) to the wire diameter d (mm) of the alloy wire is 10 A step of obtaining a closed-end coil spring-shaped coil formed body,
Step 2: Continuously with Step 1, the obtained coil molded body is ground, and at one or both of the coil ends, the thickness d _E (mm) of the tip of the alloy wire in the spring axial direction and the wire of the alloy wire Obtaining a coil grinding body having a ratio (d _E / d) to a diameter d (mm) of 0.50 to 0.75, and
Step 3: A step of applying a shape memory heat treatment to the coil grinding body to obtain a coil spring.

  In the above step 1, that is, the coiling step, the ratio (D / d) of the average coil diameter D (mm) to the alloy wire diameter d (mm) is 10 or less, and a closed-end coil spring The reason for making the shape is as described above. There is no restriction | limiting in particular about the cold working method for obtaining the coil molded object which has said shape. For example, an automatic coiling machine can be used, or a lathe-type coiling machine in which a core metal (metal bar) is attached to a lathe spindle and rotated, and a wire is wound around the core to be coiled.

In the above step 2, that is, in the step of obtaining the coil grinding body, the obtained coil molded body is ground, and the thickness d _E (mm) of the tip end portion of the alloy wire in the spring axis direction at one or both of the coil ends. The reason for obtaining a coil grinding body in which the ratio (d _E / d) of the wire diameter d (mm) of the alloy wire is 0.50 to 0.75 is as described above. There is no limitation on the grinding method. For example, an automatic end surface grinder can be used, or grinding can be performed manually using a grinder. At this time, it is desirable to use a jig so that the axial direction of the spring and the grindstone are orthogonal to each other.

Here, the process of obtaining this coil grinding body is performed continuously to the process 1, that is, by performing grinding as it is without performing a temporary heat treatment. If the grinding process is such that the ratio (d _E / d) falls within the range of 0.50 to 0.75, the coil end is not deformed during grinding even if the coil end grinding process is performed without performing a temporary heat treatment. There is no burrs and the sitting as a spring is stable.

  In the step 3, that is, the shape memory heat treatment step, a coil spring storing a predetermined shape can be obtained. The shape memory heat treatment is performed while being constrained to a predetermined shape. The shape memory heat treatment condition may be set according to the required phase transformation temperature. For example, the shape memory heat treatment is preferably performed at 400 ° C. to 500 ° C. If it is less than 400 ° C., moldability may be deteriorated (spring average diameter or restraint length becomes larger than the target value due to springback). On the other hand, when it exceeds 500 ° C., the repetition characteristics of the shape memory effect may be deteriorated. However, the temperature level is adjusted according to the target phase transformation temperature. The shape memory heat treatment time is preferably several minutes to 2 hours. The length of time depends mainly on the heat capacity of the restraining jig used. Also in this case, if the time is too short, the moldability is poor, and if it is too long, the repetitive characteristics may be deteriorated.

  Although there is no limitation about manufacturing conditions other than said process 1-3, the following manufacturing method is employable, for example.

Drawing The alloy wire which is a starting material of the coil spring of the present invention can be manufactured by a normal manufacturing method. For example, after hot working an alloy material having a predetermined chemical composition, the alloy wire can be obtained by die reduction or other cold working, diameter reduction and wire drawing, and annealing as necessary. Here, when the cold working rate (reduction in the cross-sectional area of the wire) exceeds 30%, the deformation resistance is remarkably increased due to the working strain. Therefore, when performing such die drawing, the working strain is removed by annealing. There is a need. As other cold working methods, cold rolling or swaging (forging) can also be used.

Deburring According to the production method of the present invention, it is not necessary to perform deburring. However, deburring may be performed particularly when high properties are required for the ground surface. Examples of the deburring method include a method of polishing using a grinder, a method of processing by shot peening, and a method of removing with an acid.

  Sponge Ti and electrolytic Ni plate (in some cases, further Cr) are weighed in predetermined amounts, melted and cast in an argon atmosphere using a high frequency induction heating furnace, and an ingot having the chemical composition shown in Table 1 is obtained. Produced. After smoothing the surface of each ingot with a grinder, it was heated to 950 ° C., subjected to hot forging, further reheated to 950 ° C., and subjected to hot rolling to produce a hot rolled wire having a wire diameter of 4 mm.

  Next, each hot-rolled wire was subjected to die drawing and annealing repeatedly to obtain a cold-drawn wire having a wire diameter of 2 mm. Each cold wire was processed into a coil shape by an automatic coiling machine, and a coil spring molded body having a coil average diameter of 10 mm or 16 mm and an effective winding number of 5 closed ends (a shape in which 1 winding on each end was in close contact) was produced. .

Subsequently, each of the coil springs molded product, tentatively heat treatment is not performed, it performs a grinding process to the coil end, to prepare a coil spring grinding bodies having a "d _{E /} d" shown in Table 1. The grinding process was performed by an automatic end face grinding machine. The automatic end surface grinding machine is composed of a disk for storing a coil spring and end grinders provided above and below the disk spring, and is an apparatus for grinding both ends of the coil spring at once.

Furthermore, each coil spring grinding body was constrained to a total length of 24 mm by a restraining jig and subjected to shape memory heat treatment at 450 ° C. × 1 hour to obtain a coil spring. About the obtained coil spring, the presence or absence of shape loss, the presence or absence of burr | flash generation | occurrence | production, and sitting stability were evaluated. The respective evaluation results are also shown in Table 1. Regarding the sitting stability, the case where the inclination angle of the outside of the spring was less than 3 ° using a measuring jig was evaluated as good. When the inclination angle of the outer side of the spring is 3 ° or more, for example, a spring having a length of 25 mm has an inclination of 1 mm or more, and there is a high possibility that trouble will occur when the spring is incorporated into the apparatus.

As shown in Table 1, Examples 1 to 5 of the present invention are coil springs in which the ratio (D / d) of the average coil diameter D (mm) to the alloy wire diameter d (mm) is 10 or less. The ratio (d _E / d) of the thickness d _E (mm) of the tip of the alloy wire in the spring axis direction to the wire diameter d (mm) of the alloy wire is in the range of 0.50 to 0.75. There was no loss of shape and burrs, and the sitting stability was good. On the other hand, in Comparative Examples 1 and 2 in which the ratio (d _E / d) is lower than the range defined by the present invention, burrs or further loss of shape occurred. In Comparative Example 3 in which the ratio (d _E / d) exceeded the range defined in the present invention, the shape loss and burrs did not occur, but the coil sitting became unstable.

  The coil spring of the present invention can be manufactured at a low cost because it can be ground without performing a temporary heat treatment in the manufacturing process, and it is not necessary to perform a deburring operation after grinding. Since the responsiveness to temperature changes is good, it is particularly suitable for use in a hot water / water mixing faucet and other fluid temperature control devices. The coil spring of the present invention can reduce the spring molding cost by about 25% compared to the conventional coil spring.

DESCRIPTION OF SYMBOLS 1 Closed end coil spring 2 Alloy wire 3 Terminal 4 Tip part 100 Hot water mixing faucet 101 Room temperature water hole 102 Hot water hole 103 Shape memory alloy coil spring 104 Bias spring 105 Discharge hole 106 Spool valve 108 Mixing chamber

Claims (6)

A closed-end coil spring composed of an alloy wire made of a Ti-Ni-based shape memory alloy,
In one or both of the coil ends, the ratio (d _E / d) of the thickness d _E (mm) of the tip of the alloy wire in the spring axis direction to the wire diameter d (mm) of the alloy wire is 0.50 to 0.00. 75,
A coil spring, wherein a ratio (D / d) of an average coil diameter D (mm) to an alloy wire diameter d (mm) is 10 or less.   2. The coil spring according to claim 1, wherein the Ti—Ni-based shape memory alloy contains 50.0 to 51.2% Ni in atomic percentage and the balance is composed of Ti and impurities. .   3. The coil spring according to claim 2, wherein the Ti—Ni-based shape memory alloy further contains at least 3% of one or more elements selected from Cr, Fe and Co in atomic percentage. . The manufacturing method of the coil spring characterized by including the following processes 1-3.
Step 1: Cold working is performed on an alloy wire made of a Ti—Ni-based shape memory alloy, and the ratio (D / d) of the coil average diameter D (mm) to the wire diameter d (mm) of the alloy wire is 10 A step of obtaining a closed-end coil spring-shaped coil formed body,
Step 2: Continuously with Step 1, the obtained coil molded body is ground, and at one or both of the coil ends, the thickness d _E (mm) of the tip of the alloy wire in the spring axial direction and the wire of the alloy wire Obtaining a coil grinding body having a ratio (d _E / d) to a diameter d (mm) of 0.50 to 0.75, and
Step 3: A step of applying a shape memory heat treatment to the coil grinding body to obtain a coil spring.   5. The coil spring according to claim 4, wherein the Ti—Ni-based shape memory alloy contains 50.0 to 51.2% of Ni in atomic percentage, and the balance is composed of Ti and impurities. Manufacturing method.   6. The coil spring according to claim 5, wherein the Ti—Ni-based shape memory alloy further contains at least 3% of one or more elements selected from Cr, Fe and Co in atomic percentage. Manufacturing method.

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