Patent ID: 12257865

MODE FOR CARRYING OUT THE INVENTION

First Embodiment

FIG.1shows a tire valve100having a valve stem10of the first embodiment. The tire valve100of this embodiment is so designed that the valve stem10is mounted to a valve mounting hole81H provided in a tire wheel81(more particularly, rim). The tire valve100includes an electrical circuit unit90fixed to a proximal end of the valve stem10. The valve stem10at a portion close to the proximal end is fitted to the valve mounting hole81H. When the tire valve100is mounted to the tire wheel81, the electrical circuit unit90is disposed inside the tire82. The valve stem10has an air injection port20K (seeFIG.2) at a distal end, and this distal end is disposed outside the tire82.

The valve mounting hole81H extends through a side face of a drop center81U of the rim of the tire wheel81and the tire valve100is arranged to extend laterally. More particularly, the side face of the center drop81U is inclined with respect to the center axis of the tire wheel81so that the tire valve100is arranged to be tilted, with the distal end of the valve stem10oriented downward.

Inside the electrical circuit unit90are provided a sensor91that detects the status of the tire82, and a wireless circuit92that wirelessly transmits the detection results from the sensor91. In this embodiment, for example, the sensor91is a pressure sensor that detects internal pressure of the tire82.

As shown inFIG.2, the valve stem10has a pipe-shaped stem body20and a cover member40covering an outer side of the stem body. Specifically, the cover member40covers a middle part of the stem body20so that the distal end and proximal end of the stem body20stick out from the cover member40. The air injection port20K mentioned in the foregoing for air injection into the tire82is provided at the distal end of the stem body20. An external thread29N is formed on an outer circumferential surface at the distal end of the stem body20. A cap29(seeFIG.1) is mated from outside with the external thread29N. The electrical circuit unit90mentioned in the foregoing is fixed to the proximal end of the stem body20. In this embodiment, the stem body20is made of brass. The stem body20may instead be made of other metal than brass, or resin, for example.

The stem body20contains a valve core11inside. Between an outer circumferential surface of the valve core11and an inner circumferential surface of the stem body20is provided a seal, so that an air passage formed inside the stem body20and communicating the inside and outside of the tire82is opened and closed by opening and closing the valve core11.

An annular protrusion21extends out from an outer circumferential surface near the distal end of the stem body20. The annular protrusion21is located at the boundary between the part of the stem body20covered by the cover member40and the external thread29N. The proximal end side portion of the stem body20is formed as a small diameter part23having a smaller outer diameter than the annular protrusion21, and between this small diameter part23and the annular protrusion21is formed an intermediate diameter part22, having an outside diameter that is intermediate between the diameters of the small diameter part23and the annular protrusion21.

The cover member40is made of elastomer. An annular engagement groove41is formed on an outer circumferential surface of a proximal end of the cover member40. The engagement groove41is located such as to surround a portion of the small diameter part23close to the proximal end of the stem body20. The engagement groove41engages with an opening edge of the valve mounting hole81H when the tire valve100is mounted to the valve mounting hole81H of the tire wheel81.

The valve stem10further includes a weight adjustment member50embedded in the cover member40closer to the distal end than the engagement groove41. The weight adjustment member50has a higher specific gravity than the cover member and is made of a material different from that of the stem body20. In this embodiment, the weight adjustment member50is made of iron.

As long as the weight adjustment member50has a higher specific gravity than the cover member40and is made of a material different from that of the stem body20, the weight adjustment member50may be made of other metal than iron, or resin, for example.

In this embodiment, the weight adjustment member50is tubular and is fitted to the outer side of the stem body20. Specifically, a fitting fixing part51that is fitted and fixed to the intermediate diameter part22of the stem body20is provided to an axial distal end of the weight adjustment member50. A tubular region R is formed between the entire weight adjustment member50except for the fitting fixing part51and the outer circumferential surface of the stem body20. The tubular region R is so formed that the elastomer forming the cover member40can enter into the region. In this embodiment, the tubular region R is filled with the elastomer (seeFIG.2andFIG.3(A)).

As shown inFIG.4andFIG.5, in this embodiment, notches31are formed at the distal end of the weight adjustment member50. The notch31extends from the distal end to a point close to the distal end of the weight adjustment member50. A plurality of such notches that are circumferentially equally spaced, for example, are provided to the weight adjustment member50(seeFIG.5(A)). A plurality of projecting pieces32left standing between the notches31at the distal end of the weight adjustment member50(more particularly, distal ends or middle portions of the projecting pieces32) constitute the fitting fixing part51. Moreover, a portion of the notch31between proximal ends of the projecting pieces32adjacent to each other forms a communication passage39that communicates a distal end of the tubular region R with an outer side of the weight adjustment member50. In this embodiment, as will be described later, this communication passage39allows the elastomer to readily enter into the tubular region R (seeFIG.3(B)) during the molding of the cover member40, so that the tubular region R is readily filled with the elastomer (seeFIG.3(A)). The rectangular shape of the notches31and projecting pieces32in this embodiment should not be limited thereto. The notches and projecting pieces may be semi-circular, triangular, hexagonal, and so on.

In this embodiment, the valve stem10is produced in the following manner, for example. First, the weight adjustment member50is fitted to the outer side of the stem body20, both of which are then inserted into a cavity79of a mold70for forming the cover member40(seeFIG.6). In this embodiment, as shown inFIG.6, the cover member40is formed by transfer molding from elastomer, for example. More particularly, the mold70is made up of a plurality of split molds71to74. The stem body20is set with the distal end oriented downward so that the external thread29N is mated with an internal thread hole in the upper surface of a lowermost located lower mold71. An elastomer material M that is the raw material of the cover member40and softened by heat is pressed into the cavity79from above. The cavity79is thus filled with the elastomer material M as shown inFIG.7. The elastomer material M is then cured (vulcanized) to fixedly attach to the stem body20, and thus the cover member40with the weight adjustment member50embedded therein is formed.

FIG.9shows one example of the cover member40formed with a weight adjustment member50without notches31. When there are no notches31, no communication passages39are formed, so that gaps S are readily formed in the distal end of the tubular region R as shown in the drawing, due to the difficulty for gas to escape from the distal end of the tubular region R. In contrast, since the notches31that form the communication passages39are provided to the weight adjustment member50in this embodiment, the elastomer material M can easily enter into the tubular region R through the communication passages39, and the gas can easily escape from the distal end of the tubular region R. Therefore, the entire tubular region R can be readily filled with the elastomer.

After forming the cover member40inside the mold70as shown inFIG.7, the stem body20, weight adjustment member50, and cover member40are removed from the mold70, and a waste portion78of elastomer is removed from the cover member40, to obtain the valve stem10shown inFIG.2.

In the case where the tire valve100is attached to the tire wheel81as described above in the manner illustrated inFIG.1, the weight balance of the tire valve100may be adjusted by setting the tire valve100such that its center of gravity is in the distal end side portion located outside the tire82, for example, which minimizes changes in attitude of the tire valve100caused by a centrifugal force during rotation of the tire82. According to the tire valve100and valve stem10of this embodiment, the engagement groove41that engages with the opening edge of the valve mounting hole81H of the tire wheel81is formed on an outer circumferential surface of a proximal end of the cover member40. The weight adjustment member50is embedded in the cover member40closer to the distal end than the engagement groove41. This enables easy adjustment of the weight balance of the tire valve100attached to the tire wheel81and allows for secure fixing of the tire valve100.

In this embodiment, the weight adjustment member50is made of a material having a higher specific gravity than the cover member40. This enables easy weight balance adjustment of the valve stem10as compared to a case where the weight balance of the tire valve100is adjusted by increasing the size of the cover member40, because there is no need to provide a new mold70for forming the cover member40. Moreover, since the weight adjustment member50is made of a material different from that of the stem body20, a cost reduction is possible, by using a more inexpensive material than that of the stem body20. The weight adjustment member50is embedded in the cover member so that the weight adjustment member50is securely fixed. Further, in the case where the weight adjustment member50is made of iron, the weight adjustment member50being embedded in the cover member40and not exposed can prevent corrosion.

In this embodiment, since the weight adjustment member50that surrounds the stem body20is tubular, the weight adjustment member50can reinforce the valve stem10. Moreover, since the weight adjustment member50is fitted to the outer side of the stem body20, the weight adjustment member50is securely fixed. This can prevent a possible loss of weight balance of the tire valve100due to a centrifugal force applied to the valve stem10during the drive of the vehicle.

In this embodiment, the weight adjustment member50is provided with the fitting fixing part51that is fitted and fixed to the stem body only at one end of the weight adjustment member, and the tubular region R is formed between the entire weight adjustment member50except for the fitting fixing part51and an outer surface of the stem body20, into which the elastomer forming the cover member40is able to enter. Since the weight adjustment member50is fitted to the stem body20only at one end, the weight adjustment member50can be fitted to the stem body20easily. This can minimize application of an excessive force during fitting and prevent deformation of the stem body20.

In this embodiment, the weight adjustment member50is provided with the communication passage39that communicates between an end (distal end) of the tubular region R close to the fitting fixing part51and the outside of the weight adjustment member50. This can minimize stagnation of gas in the distal end of the tubular region R during the forming of the cover member40from elastomer.

Other Embodiments

(1) In the above embodiment, the communication passage39is formed by the notches31of the weight adjustment member50. Instead, a through hole extending radially through the weight adjustment member50may be formed in a distal end, and the communication passage39may be formed by this through hole. Alternatively, a groove extending in an axial direction of the stem body20may be formed in the intermediate diameter part22of the stem body20, and the communication passage39may be formed by this groove.

(2) While the weight adjustment member50in the above embodiment has a fitting point with the stem body20at one end, a fitting point may also be provided to other parts along the axial direction. The fitting point may be provided not at the distal end of the weight adjustment member50but at other part (such as, for example, proximal end). In a case where the fitting point is provided at a proximal end of the weight adjustment member50, notches31and communication passages39may be provided at the proximal end.

(3) While the weight adjustment member50is fitted to the outer side of the stem body20in the above embodiment, the weight adjustment member may not necessarily be fitted to the stem body. In this case, for example, the tubular region R may extend entirely along the axial direction between the weight adjustment member50and the stem body20.

(4) While the weight adjustment member50in the above embodiment is tubular, the weight adjustment member may not necessarily be tubular. For example, the weight adjustment member may be cuboidal, spherical, rod-shaped (e.g., extending along the axial direction of the stem body20), ring-shaped (e.g., in the shape of letter O, or C), reticular, and so on.

DESCRIPTION OF THE REFERENCE NUMERAL

10Tire valve stem20Stem body2039Communication passage40Cover member50Weight adjustment memberR Tubular region