JPH09303556A - Resin constant velocity joint boot and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both elasticity and flexibility in addition to mechanical strength, and maintain high connecting sealability by forming a coupling ring part out of an alloy of both thermoplastic polyester resin and thermoplastic urethane resin. SOLUTION: A boot has coupling ring parts 10 of large and small diameters at both ends for connection to mating members, as well as a bellows part 12 of stretchable type at an intermediate part in such a state as continuous to the ring parts 10. Also, both of the coupling ring parts 10 and the bellows part 12 are required to have mechanical strength, water resistance, oil resistance and heat resistance. In particular, the coupling ring parts 10 are externally coupled and connected to mating members and required to have elasticity and flexibility in addition to the mechanical strength. Also, the bellows part 12 is subjected to a strong centrifugal force and, therefore, required to have high mechanical strength. Thus, the coupling ring parts 10 are made of an alloy of thermoplastic polyester resin and thermoplastic urethane resin, and the blending ratio of the alloy is set so as to have strength as per JIS within 50 to 90. Also, the bellows part 12 is formed out of thermoplastic polyester resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin constant velocity joint boot for covering and closing a drive shaft of an automobile having fitting ring portions connected to mating members at both ends and bellows portions such as bellows formed in the middle thereof. And a manufacturing method thereof.

[0002]

2. Description of the Related Art In a constant velocity joint boot (hereinafter, simply referred to as boot), a fitting ring portion having a connecting function for connecting to a mating member at both ends can cover a cover member in the middle. A bellows portion having a flexible covering function is formed. In this case, the fitting ring portion is required to have high elasticity and high sealing property, and the bellows portion is required to have high strength to withstand a large centrifugal force due to high speed rotation.

On the other hand, recently, these boots are also shifting from those made of rubber to those made of resin. Resin boots have excellent mechanical strength and durability, but have poor elasticity and poor sealing performance as a fitting ring. For this reason, a special tightening band that complements its function is used in the fitting ring portion, but this band is expensive, and this increases the cost.

[0004]

[Patent Document 1] Japanese Patent Laid-Open No. 2-1
In 20574, even with the same thermoplastic resin, the fitting ring portion is made of a material having a high elasticity and the bellows portion is made of a material having a high strength, and both are joined by high frequency or vibration pressure welding, or by an adhesive. A method of adhering is proposed.
However, the properties of a single thermoplastic resin are specified, and such a method requires more steps and is costly. The present invention solves this problem by applying an alloy of a resin which has recently been put to practical use to this and adopting a thermoplastic urethane as the resin to be mixed.

[0005]

Under the above-mentioned problems, the present invention provides a resin boot comprising a fitting ring portion formed at both ends and a bellows portion formed at an intermediate portion. Provided is a resin boot characterized in that a part thereof is composed of an alloy of a thermoplastic polyester resin and a thermoplastic urethane resin. Then, in this means, the resin boot in which the alloying ratio of the alloy is set in the range where the JIS hardness of the fitting ring portion is 50 to 90 is provided.

Further, the present invention is characterized in that, in the above-described method for manufacturing a resin boot, the bellows part is manufactured by the primary molding and the fitting ring part is molded by the secondary molding. Also provided is a method of manufacturing the resin boot. Then, there is provided a method of manufacturing a resin boot in which the bellows portion of the primary molding is injection-molded on the entire circumference by a film gate.

Since the fitting ring portions at both ends of the resin boot according to the present invention are made of the alloy of the thermoplastic polyester resin and the thermoplastic urethane resin, the high strength of the thermoplastic polyester resin and the thermoplastic urethane are obtained. It also has the high elasticity properties of the resin, and it does not become dissatisfied with the sealing property and durability. In addition, by manufacturing the resin boot according to the present invention by the above method, the resin boot can be manufactured by a series of molding steps and without the need for joining and bonding operations. Furthermore, the fusion surface is not formed by injection molding the bellows portion around the entire circumference with the film gate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view of a boot showing an example of the present invention. The boot has a large-diameter and a small-diameter fitting ring portion 10 connected to opposite members at both ends thereof, and a bellows which is continuous to these in the middle thereof. A bellows portion 12 having a shape is formed.

Here, the fitting ring portion 10 and the bellows portion 1
Both of them are required to have mechanical strength, water resistance, oil resistance, and heat resistance, but in particular, since the fitting ring portion 10 is externally fitted and connected to the mating member, in addition to mechanical strength, elasticity, Since flexibility is required and strong centrifugal force acts on the bellows portion 12, high mechanical strength is required. Therefore, in the present invention, the fitting ring portion 10 is made of an alloy of thermoplastic polyester resin and thermoplastic urethane resin, and the bellows portion 12 is formed.
Is composed of a thermoplastic polyester resin.

As the thermoplastic urethane resin, a combination of polyurethane as a hard segment and polyol or polyester as a soft segment is generally used. According to this soft segment component, it is roughly classified into four types, polycarbonate type polyol type, ether type polyol type, caprolactone type polyester type, and adipate type polyester type. It is selected appropriately. Among them, the boots are particularly required to have water resistance and oil resistance, and therefore ether type polyols are preferably used.

The thermoplastic polyester resin is roughly classified into an aliphatic polyether and an aliphatic polyester depending on the kind of the soft component in the polymer. Since each has unique characteristics, it is appropriately selected according to the purpose and application. It Among these, the aliphatic polyether type is preferable.

In order to obtain an alloy of the thermoplastic polyester resin and the thermoplastic urethane resin, a material resin may be obtained by mixing the two in a molten state by a known method. Specifically, both may be extruded by a twin-screw extruder to form mixed pellets for use.

When a thermoplastic urethane resin (TPu) is alloyed with a thermoplastic polyester resin (TPEE), elasticity and flexibility are added to its mechanical properties, the degree of which is generally proportional to the reciprocal of hardness (in other words, , Mechanical strength is proportional to hardness).

The following table shows the mixing ratio and hardness (JI
S A)).

Use TPu Examples 1-3 Kuramiron u8000 manufactured by Kuraray Co., Ltd. Example 4 ET370 manufactured by Takeda-Bardiche Urethane Industry Co., Ltd. Example 5 1180A50 manufactured by Takeda-Bardiche Urethane Industry Co., Ltd. Used TPEE Examples 1-5 Toyobo Co., Ltd. Company-made Perprene P-55B

Generally, the hardness decreases as the compounding ratio of the low hardness TPu increases, and increases as the compounding ratio decreases.
In order to maintain its function, it is desirable that the hardness is in the range of 50 to 90, preferably 60 to 70. If it is lower than this, the mechanical strength is insufficient, and if it is higher, the elasticity becomes insufficient.

Next, a method of manufacturing a boot having such a structure will be described. 2 and 3 are explanatory views thereof, this resin boot is a composite using a bellows part molding die 14, a core mold 16, a fitting ring part molding upper mold 18, a fitting ring part molding lower mold 20, and the like. Manufactured by injection molding.

Here, the bellows part molding die (hereinafter referred to as bellows mold) 14 is one in which two mold spaces each having the outer shape of the bellows part 12 are formed at regular intervals. The upper die 18 and the fitting ring portion forming lower die 20 can be moved in parallel or rotationally.

The core die 16 is held in the die space of the bellows die 14 with a certain gap in order to secure the inner shape of the bellows portion 12.

The fitting ring portion molding upper die (hereinafter referred to as upper die) 18 is a mold space for forming the fitting ring portion 10 having a smaller diameter, and an injection path 22 communicating with this mold space.
And an injection path 24 communicating with the film gate method in the gap between the mold space of the bellows mold 14 and the core mold 16.

The fitting ring portion molding lower die (hereinafter referred to as the lower die) 20 has a mold space for forming the larger diameter fitting ring portion 10 and an injection path 22 communicating with this mold space. It was formed.

A thermoplastic polyester resin for forming the bellows portion 12 is supplied to the injection hole (A) communicating with the injection path 24, and the injection hole (B) communicating with the injection path 22 is supplied with the thermoplastic polyester resin. The alloy of thermoplastic polyester resin and thermoplastic urethane resin for forming the fitting ring portion 10 is supplied.

As described above, the bellows mold 14, the upper mold 18, and the lower mold 20 are arranged as shown in FIG.
At this time, it is assumed that the thermoplastic polyester resin has been already injected into the gap between the mold space of the right bellows mold 14 and the core mold 16. In this state, an alloy of the thermoplastic polyester resin and the thermoplastic urethane resin is injected from the injection hole (B), and at the same time, the thermoplastic polyester resin is injected from the injection hole (A).

By this operation, the resin boot is completed at the right side position in FIG. 2, and the bellows portion 12 is molded at the left side position. Therefore, the upper mold 18 and the lower mold 20 are opened, and the completed resin boot (product) at the right side position is taken out. At this time, the bellows mold 14 needs to be appropriately divided, and the core mold 16 needs to be divided and the like and pulled out from the product, but these are already performed. , Detailed description is omitted here.

After the above operation is completed, the core mold 16 is inserted, the bellows mold 14 is closed, and the bellows mold 14 is parallel to the upper mold 18 and the lower mold 20 so that the state shown in FIG. To move. In this state, the thermoplastic polyester resin is injected from the injection hole (A), and the injection hole (B)
When an alloy of a thermoplastic polyester resin and a thermoplastic urethane resin is injected, the product is formed at the left side position and the bellows portion 12 is formed at the right side position. Therefore, the same operation as described above may be performed thereafter. By repeating such a process, products are successively formed.

Such a molding method is called a compound injection molding method. In the present invention, the bellows portion 12 is molded by the primary molding,
The molding of the fitting ring portion 10 is called secondary molding. According to this method, since many kinds of resins can be injected simultaneously, there is an advantage that the molding time can be shortened, and the secondary resin can be injected while the resin injected in the primary is hot, resulting in a special joining operation. There is an advantage that they can be firmly integrated without each other.

In this case, when the bellows portion 12 of the primary molding is injection-molded on the entire circumference by the film gate method, the fusion surface is not formed on the peripheral surface, so that the strength becomes strong. .

Although a few embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to these and various modified forms can be taken. For example,
The fitting ring portion may be an alloy of a thermoplastic polyester resin and rubber which has been put into practical use in recent years. or,
The molding method is not limited to the composite injection molding. The point is that it is sufficient that the next resin can be injected while the already-injected resin is hot. As long as this is satisfied, a method of taking out from one mold and transferring it to the next mold may be used.

[0029]

As described above, the present invention is as described above, that is, the fitting ring portions at both ends of the resin boot are made of an alloy of thermoplastic polyester resin and thermoplastic urethane resin. The former has high mechanical strength and the latter has elasticity and flexibility, so that the connection sealing property can be made excellent. Since the resin boot is manufactured by the composite molding method, the molding time can be shortened, and the boot can be firmly integrated without any operation such as joining or bonding, which contributes to cost reduction.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a boot showing an example of the present invention.

FIG. 2 is an explanatory diagram of a boot manufacturing method showing an example of the present invention.

FIG. 3 is an explanatory view of a boot manufacturing method showing an example of the present invention.

[Explanation of symbols]

 10 Mating ring part 12 Bellows part

Claims (4)

[Claims] 1. A resin constant velocity joint boot comprising a fitting ring portion formed at both ends and a bellows portion formed at an intermediate portion, wherein the fitting ring portion is made of a thermoplastic polyester resin and a thermoplastic urethane resin. A constant velocity joint boot made of resin, which is made of an alloy of 2. The JIS hardness of the fitting ring portion is 50 to 90.
The resin constant velocity joint boot according to claim 1, wherein the alloying ratio is set within the range. 3. The method of manufacturing a resin dustproof boot according to claim 1, wherein the bellows part is manufactured by the primary molding and the fitting ring part is molded by the secondary molding. And a method for manufacturing resin constant velocity joint boots. 4. The method for manufacturing a resin constant velocity joint boot according to claim 3, wherein the bellows portion of the primary molding is injection molded with a film gate over the entire circumference.