JPH063213A - Tire pressure guage for performing isothermal measurement - Google Patents

Abstract

PURPOSE: To precisely measure the pressure of air in a tire under the temperature condition that the temperature is adjusted to be the same as that in the inside of the tire at the time of measurement. CONSTITUTION: To carry out quick leveling of the difference of the temperature in a tire 70 and in a bellows 1, the bellows 1 to detect the pressure is installed in the tire 70. A flexible display rod 2 extensible to the outside from the inside of the tire 70 is installed in the bellows 1 and moves back and forth with the expansion and contract of the bellows 1. Consequently, based of the movement of the tip position 23 of the flexible display rod 2 positioned in the outside of the tier 70, the pressure state of the tire 70 can be easily known.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure gauge, and more particularly to a pressure gauge for measuring tire pressure.

[0002]

2. Description of the Related Art At present, most automobile tires are made by compressing air into an elastic body such as rubber and filling the same.
The optimum value of the inflated air pressure generally differs depending on the type of tire, the weight of the vehicle, the driving conditions, and the like. Therefore, in order to confirm the air pressure in the tire and adjust the pressure, a tire pressure gauge for measuring the tire pressure is required, and various types are used.

An example of such a pressure gauge is a tire pressure gauge disclosed in US Pat. No. 1,582,523. This pressure gauge has a main tube attached to a hole formed in the inner tube of the tire, and a flange formed at the base end of the main tube and a washer or nut screwed onto the outer circumference of the main tube. The main tube is fixed to the inner tube by pinching the inner tube. In the main tube,
A bag-shaped member made of flexible rubber, that is, a tube, is housed, the lower end of the tube is fixed to the main tube by the recess of the flange and the nut mounted from inside the inner tube, and the upper end is the shoulder of the slide tube. It is fixed to the shaped piston. The slide tube is accommodated in the main tube so as to be movable back and forth, and protrudes from the upper end of the main tube to the outside. In addition, the end portion, that is, the flange, accommodated in the main tube is held by a washer located at the stepped portion of the cylindrical member that is screwed and mounted on the slide tube. A spring is wound around the outer circumference of the slide tube with play. The outer end of the spring is in contact with the flange of the upper end of the main tube, and the inner end of the spring is in contact with the flange of the slide tube, that is, the piston. .
Also, as shown, a conventional valve is screwed onto the upper end of the slide tube. The upper part of the slide tube is threaded, and the upper flange of the scale sleeve is clamped by a nut screwed in here. Therefore, when the slide tube moves due to the pressure change in the inner tube, the scale tube moves together with it. Further, an outer sleeve for preventing breakage of the scale tube is engaged with a nut portion formed on the outer circumference of the bottom portion of the main tube, and can be slid up and down. Further, the outer sleeve covers a large part of the main tube at a constant distance, and the scale tube is housed therein.

[0004]

However, in such a device for directly measuring pressure by connecting a valve for filling air with a tire pressure gauge, a main body in which a slide tube and a scale sleeve are fixed to a tire at the time of pressure measurement is used. Since it slides on the tube, if it is used for a long period of time, the washers, nuts and other packing rings will be worn out, and air leakage will easily occur. Therefore,
The measured values will be inaccurate, and the tire pressure will drop, which may cause unexpected trouble.

Further, the elastic rubber tube is not sealed and easily leaks, and most of it faces the outside of the tire, that is, the outside air. Therefore, the air inside the rubber tube is easily affected by the outside air temperature, and the measured tire pressure is easily affected by the outside air temperature change. In particular, the air in the tire during high speed running and immediately after that is heated by frictional heat etc. and its temperature rises, so the measured pressure value will be affected by the temperature difference between the inside and outside of the tire, resulting in an error. .

Further, since the valve and the pressure gauge for filling the air are provided so as to project from the surface of the tire in a substantially vertical direction, the valve and the pressure gauge are deformed and destroyed by the centrifugal force generated by the rotation of the tire. It's easy to do.

The present invention, which has been made in view of the above problems, is an isothermal tire pressure gauge for accurately measuring the pressure of air in a tire under the temperature condition that the temperature is the same as the temperature in the tire at the time of measurement. The purpose is to provide.

[0008]

DISCLOSURE OF THE INVENTION The present invention for achieving the above object is a tire pressure gauge which is attached to a tire of an automobile to constantly measure the pressure inside the tire, and a holding member attached to the tire. The bellows, which is expandable and retractable and which seals air, is held inside the tire, and the base end portion of the flexible display rod housed in the introduction hole formed in the holding member so as to be movable back and forth is attached to the bellows. This is a tire pressure gauge for isothermal measurement characterized in that A holding member having a recessed chamber is formed of a heat conductive material, and an expandable bellows for sealing gas is housed in the recessed chamber of the holding member, and is movable back and forth in an introduction hole formed in the bottom of the recessed chamber. Is a tire pressure gauge for isothermally measuring the base end portion of the flexible display rod accommodated in the bellows. Further, the insertion member is formed of an introduction hole opened on the bottom surface of the recess of the holding member, a guide hole communicating with the introduction hole, and a hollow portion smoothly communicating with the guide hole and extending in an arc shape or a spiral shape to be closed. It is a tire pressure gauge for isothermal measurement having a flexible display bar which is housed in a hole so as to be movable back and forth. Further, the base end portion of the flexible display rod accommodated in the introduction hole so as to be movable back and forth is attached to the pressure sensitive plate attached to the bellows accommodated in the concave chamber of the holding member,
4. The tire pressure gauge for isothermal measurement according to claim 3, wherein the tip end portion of the flexible display rod is housed in a hollow portion that extends in an arc or spiral shape and communicates with the introduction hole and the guide hole and is closed so as to move back and forth. Further, a hollow portion communicating with the introduction hole and the guide hole is formed into a disk shape, and the hollow portion is interlocked with the forward / backward movement operation of the flexible display rod housed in the introduction hole and the guide hole so as to be able to move forward / backward. It is a tire pressure gauge that rotatably accommodates a rotating disk and measures isothermally. A tire pressure gauge for isothermal measurement is provided, in which a transparent lid is attached to a position covering the disk-shaped hollow portion, and a transparent lid having a scale is formed at a position along the outer circumference of the hollow portion.

The charging valve is attached to the holding member so that the introduction hole formed in the holding member and the guide path formed on the fitting surface of the holding member of the charging valve communicate with each other. An outer peripheral surface of a charging valve that communicates with the guide path and a hollow path extending in a circular arc shape or a spiral shape that accommodates the tip of a display rod so as to move forward and backward and to a fitting surface with a holding member of the charging valve. A tire pressure gauge for isothermal measurement, characterized in that a cylindrical transparent lid with a scale engraved on the outer peripheral surface thereof is fitted. Then, an insertion hole formed in the bottom surface of the concave chamber of the holding member installed on the inner surface of the tire is smoothly bent to be installed along the outer surface of the tire, and is attached to the bellows housed in the concave chamber. A tire pressure gauge for accommodating a rod, the rod being housed in the insertion hole so as to be movable back and forth, and a transparent lid covering the insertion hole is attached to the outer surface of the insertion hole extending along the outer surface of the tire.

Further, the fixed end of a bellows tube having a closed end and integrally formed with the flexible display rod is attached to a holding member integrally formed with a transparent tube having a graduated scale. A tube and a closed end portion for sealing gas are formed, and a display rod for displaying the pressure inside the tire is housed in the tube protruding outside the tire so as to be movable forward and backward. It is a tire pressure gauge. Further, the tire pressure gauge is for isothermal measurement, in which a bellows attached to the holding member is formed in a sealed bag shape for enclosing a gas or a liquid, and one end of the sealed bag-shaped bellows is provided with an end portion that can move back and forth.

[0011]

[Function] The pressure is detected by the bellows installed inside the tire. A flexible indicator bar extending from the inside of the tire to the outside is attached to the bellows so that the bellows can move forward and backward in conjunction with expansion and contraction of the bellows.
Therefore, the pressure state inside the tire can be easily known by the movement of the tip position of the flexible display rod located outside the tire. Then, the bellows is housed in the concave chamber of the holding member made of a heat conductive material. As a result, the temperature difference between the inside of the tire and the inside of the bellows is quickly leveled.

Further, when the bellows is made of a material having excellent elasticity, the position of the closed end changes depending on the pressure inside the tire. Therefore, the bellows itself can be used as a display rod for displaying pressure, and the structure is simplified. By integrating the holding member for holding the bellows and the display rod for displaying the pressure, that is, the tube for housing the bellows, the structure is simplified and the air is sealed more easily.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1, 2 and 3, the pressure gauge of this embodiment mainly includes a bellows tube 1, a flexible display rod 2, a display rod insertion hole 3, a transparent lid 4, and a charging valve 5. The packing 6 is fixed to the tire 7.

As shown in FIG. 1, the pressure gauge of the present invention is covered on the outside with a stepped cylindrical outer packing 63, and a large diameter portion of the outer packing 63 is accommodated in a tire 70. As shown in FIGS. 2 and 3, the small diameter portion is attached so as to protrude from the surface of the tire 7. Further, as shown in FIG. 1, an inner packing 61 is attached to seal the outer packing 63 and the inner surface of the tire 7 more tightly. As shown in the figure, the holding member 13 made of a heat conductive material is fitted in the outer packing 63, and has a recessed chamber 14 opened toward the inside of the tire 7. This recess chamber 14
At the center of the convex portion provided at the center of the bottom surface of the tire 7, there is provided an introduction hole 30 whose opening end is the taper port 15 which is opened in a tapered shape, and a central hole 301 which is opened to the outside of the tire 7. Penetrates into.

A valve body 5a for sealing air in the tire 70 is attached to the central hole 301 by screw connection. A groove extending in the longitudinal direction from the end surface of the valve body 5a on the joining side is provided on the side surface of the fitting portion 54 with the holding member of the valve body 5a. A guide hole 31 communicating with the hole 30 is formed. Further, the holding member 13 is provided with a spiral groove extending to the guide hole 31, and the hollow portion 32 communicating with the guide hole 31 by the inner surface of the transparent lid 4 fitted to the side surface of the valve body 5a. Are formed. Therefore, the holding member 13,
By combining the valve body 5a and the transparent lid 4, a series of display rod insertion portions 3 extending from the introduction hole 30 formed on the bottom surface of the concave chamber to the tip of the spiral hollow portion 32 is formed. Needless to say, the holding member 13 and the valve body 5a may be integrally formed. Then, the holes 30 and 31 may be formed in the holding member or the valve body, and the openings of the holes may face each other to communicate with each other. Further, as shown in the figure, the transparent lid 4 has its end face on the side opposite to the tire 7 in contact with the ring-shaped protrusion 55 provided on the valve body 5a via the packing 65, and the upper end of the outer packing 63. The end surface of the step portion at the end portion on the tire side fitted to the inner surface has the center hole 301 of the holding member 13 via the packing 64.
Since it is pressed against the upper end surface of the transparent lid 4, the transparent lid 4 can be fixed by attaching the valve body 5a to the holding member 13.

As further illustrated, the valve body 5a
A ventilation hole 60 is formed in the inside, and communicates with a ventilation pipe 50 provided in the holding member 13. A valve seat 56 having a tapered valve seat surface 53 is fitted in the hollow portion 32 which is in contact with the side surface of the valve body 5a, and is held by the valve body 5a by a holder 57 screwed into the hollow portion 32. There is. In addition, a rod-shaped spindle valve 51 penetrating the valve seat 56 is installed in the hollow portion 32, and a spring 58 abutted against an umbrella-shaped valve 52 provided in the middle of the spindle valve 51 is shown in the figure. It is biased upward. Therefore, the valve 52 pushed upward in the drawing by the biasing force of the spring 58 is in close contact with the valve seat surface 53 and closes the air passage, so that the leakage of air from the inside 70 of the tire is surely prevented. A cover 59 is attached to the front end surface of the valve body 5a by screwing to prevent foreign matter from entering and malfunction of the valve.

On the other hand, in the concave chamber 14 of the holding member 13, a bellows tube 1 having a bellows shape, in which air is sealed and expandable and contractible.
Has been charged. One end of the bellows tube 1, that is, the fixed end 11, is fixed on the bottom surface of the recess chamber 14,
The other end, that is, the moving end 12 is movable toward and away from the fixed end 11. Therefore, when the bellows tube 1 expands and contracts, the moving end 12 comes close to and separates from the bottom surface of the concave chamber 14.

The movable end 12 is integrally formed with a pressure sensitive plate 21 attached to the movable end 12, and the flexible display rod 2 extends in a direction penetrating the inside of the bellows tube 1.
The flexible display rod 2 is inserted into the introduction hole 30 and is housed in the display rod insertion portion 3. As shown in the figure, the side edge of the pressure sensitive plate 21 slidably contacts the side wall of the recessed chamber 14, so that when the pressure of the air filled in the tire 70 changes, the pressure sensitive plate 21 is fixed.
Moves away from and moves toward 1. Further, the base end portion of the display rod 2 has a taper shape that becomes thinner as the distance from the pressure sensitive plate 21 increases, and the tip end side 22 is smoothly bent along the spiral hollow portion 32 of the display rod insertion path 3. . Therefore,
When the bellows tube 1 is compressed and the pressure sensitive plate 21 approaches the fixed end 11 side and approaches a predetermined distance, the base end portion of the display rod 2 fits into the tapered port 15, so that the bellows tube 1 or the transparent tube 1 should be transparent. Even if the lid 4 is damaged, the air filled in the tire 7 does not leak to the outside.

When the pressure in the tire 70 changes due to air leak in the tire 70, the pressure sensitive plate 21 moves and the flexible display rod 2 moves, so that the position of the tip 22 of the flexible display rod 2 changes. The pressure change can be confirmed by recognizing through the transparent lid 4. That is, as shown in FIG. 3, by calibrating the scale 40 on the transparent lid 4 in advance, the position of the tip 23 of the display rod 2 and its change can be instantly and easily confirmed. Flexible display bar 2
Is a member made of a flexible elastic material such as soft plastic and is easily deformed, so that it can be moved smoothly even in the hollow portion 32 at the tip of the display rod insertion portion 3 that is spirally bent. Further, the tip 23 of the display rod 2 may be colored so that the scale 40 of the transparent lid 4 corresponding to the position of the display rod 2 can be read quickly and reliably.

Next, a tire mounting example of the tire pressure gauge will be specifically described. As shown in FIG. 2, the tire pressure gauge is attached at a position facing the tire hob portion 71,
The upper portion of the valve is adapted to protrude from the tire hob portion 71.

When air is filled into the tire 70 from the valve of the tire pressure gauge attached in this way, the pressure in the tire 70 rises. Therefore, the indicator bar 2 of the pressure gauge shown in FIG. Moves upward in the figure according to the pressure,
Along with this, the tip 23 of the display rod 2 moves forward. Since the tip 23 of the display rod 2 is adapted to move back and forth along the hollow portion 32 formed facing the transparent lid 4 on which the scale 40 is graduated, the position of the tip 23 of the display rod 2 and The scale 40 of the transparent lid 4 corresponding to this can be easily and instantly read. And for some reason, inside the tire 7
Even in the case where the air of 0 leaks and the pressure in the tire 70 drops, the same as above, the changed position of the tip 23 of the display rod 2 and the scale of the transparent lid 4 corresponding to this position. 40 can be read easily and instantly. The transparent lid 4 may be provided with a portion having the function of the convex lens 41 to make it easier to read.

Further, since the bellows tube 1 is fixed in the tire 70 and is mounted in the concave chamber 14 of the holding member 13 made of a heat conductive material, the temperature of the air enclosed in the expandable bellows and the inside of the tire. The air temperature is always leveled, and the temperature inside the bellows is hardly affected by the outside air temperature. Therefore, the difference between the outside air temperature and the temperature inside the tire does not affect the display indicated by the pressure gauge. In other words, since the tire pressure gauge of this embodiment displays the amount of air filled in the tire 7, the occurrence of air leakage can be displayed very reliably. In this way, the tire pressure gauge of the above embodiment is like a pressure sensor.

Next, another embodiment will be described. The same members as those already described are designated by the same reference numerals.
As shown in FIG. 4, the tire pressure gauge of this embodiment is
The holding member 13 is in contact with the tire 7 via the inner packing 61. A sleeve 15a is provided in the center of the bottom surface of the holding member 13, and the holding member 13 is also in contact with the tire 7 at the outer end surface of the sleeve 15a.
An introduction pipe 31a of a penetrating member 3a provided to penetrate the tire 7 is screwed to the sleeve 15a.
The disk-shaped head 33 of the penetrating member 3a is an outer packing 63.
It contacts the outside of the tire 7 via a. Therefore,
The tire pressure gauge can be firmly attached to the tire 7 by securely fastening the holding member 13 and the penetrating member 3a that are screwed together and sandwiching the tire 7 securely, and prevent air leakage from the attaching portion. it can.

Further, as shown in FIG. 5, the penetrating member 3a
The guide hole 31a provided in the introduction pipe 31a of the above is smoothly bent toward the side surface of the disk-shaped head 33, and then penetrates to the outside, and the head 33 is provided at the head-side opening of the guide hole 31a. Is smoothly connected to the step formed along the peripheral edge of the end face. As shown in FIG. 4, a transparent lid 4a whose outer periphery is sealed by an outer packing 63a is fitted into the head 33 of the penetrating member 3, and the head 3
Since the hollow portion 32 surrounded by the stepped portion provided on the outer periphery of the end face of the transparent lid 3 and the inner surface of the transparent lid 4a is formed, by combining the penetrating member 3a and the transparent lid 4a, the through member 3a
A series of display bar insertion holes 3 having openings at the end faces of the are formed. Since the transparent lid 4a is sealed by the outer packing 63a, the air in the display rod insertion hole 3 does not leak outside.

On the other hand, in the concave chamber 14 of the holding member 13, the bellows tube 1 whose one end, that is, the fixed end 11 is fixed to the bottom surface of the concave chamber 14 is housed, which is the other end, as in the above embodiment. A pressure sensitive plate 21 is attached to the end 12.
The pressure sensitive plate 21 is slidably in contact with the side wall of the concave chamber 14,
The flexible display rod 2 extending from the pressure sensitive plate 21 as a base end is inserted into the display rod insertion hole 3. Therefore,
When the pressure-sensitive plate 21 slides according to the pressure inside the tire 70, the tip 23 of the flexible display rod 2 moves back and forth along the hollow portion 32 that is housed. As described above, the tire 70 may be used as a single pressure gauge instead of being integrated with the valve for filling the tire with air.

Further, as shown in FIG. 6, it may be attached to the tire in parallel to the outer surface of the tire along the circumferential direction. The same members as those already described are designated by the same reference numerals. As shown in FIG. 7, in the tire pressure gauge of this embodiment, the holding member 13 that accommodates the telescopic bellows tube 1 is attached with the side surface in contact with the tire 7, and is attached to the moving end 12 of the bellows tube 1. The pressure plate 21 is
It moves forward and backward along the side surface of the tire 7. Further, as shown in the drawing, the display rod insertion hole 3b in which the flexible display rod 2 extending with the pressure sensitive plate 21 as a base end is housed so as to be movable back and forth,
It is opened on the bottom surface of the holding member 13 and smoothly communicates with a hollow portion extending along the outer surface of the tire 7 via the inclined portion 32b. As shown in FIG. 6, the portion along the outer surface of the tire 7 extends in an arc shape, and the transparent lid 4b
Since it is covered with, the position of the tip of the flexible display rod 2 can be easily recognized from the outside. The packing 6b for holding the holding member 13 fixed to the content surface of the tire 7
May be integrally formed with the tire 7.

Although the respective embodiments have been described above, the basic structure common to these embodiments is as shown in FIG. That is, as shown, the bellows tube 1
Is installed inside the tire 7, and the display rod 2 that displays the pressure inside the tire in conjunction with the expansion and contraction of the bellows pipe 1 is attached to the display rod insertion hole 3 and pulled out of the tire 7. The pressure inside the tire 7 is recognized by the position indicated by the display rod 2 pulled out of the tire 7.

Further, for example, a tire pressure gauge having a structure as shown in FIGS. 9 to 12 can be considered. In the pressure gauge of the embodiment shown in FIGS. 9 and 10, the holding member 13c integrally formed with the tube 4c and the expandable bellows 1 are provided.
Air is sealed in the space A formed by c and
As a result, the bellows 1c moves back and forth in response to pressure changes. Further, in the pressure gauge shown in FIG. 11, the sealing member 1d having the function of the bellows tube and the function of the display rod is fixed to the holding member 13d. The sealing member 1d is housed in a transparent tube 4d, and a change in pressure due to air leakage or the like is displayed by expansion and contraction of a closed end 2d portion of the sealing member 1d housed in the tube 4d. Further, in the pressure gauge shown in FIG. 12, the display rod 2e is a telescopic member 1 for enclosing the liquid B therein.
It is formed of e and is fixed to the holding member 13e at the flange portion provided on the side portion. Therefore, the pressure sensed in the liquid pool of the display rod 2e is displayed by the position of the tip of the display rod 2e housed in the transparent tube 4e. Further, in the pressure gauge shown in FIG. 13, a display rod 1f made of an expansion and contraction member and having a space for enclosing gas is fixed to the tip end side of the tube 4f, and the display rod 1f depends on the pressure inside the tire 7. One end 2f of the is expanded and contracted. In addition, in the sectional views shown in FIGS. 9 to 13, in order to clarify the structure, packing for preventing air leakage is omitted, and the function of the display rod insertion hole and the transparent lid are combined. A transparent tube is used as a holding member. Furthermore, this transparent tube is integral with the holding member.

[0029]

As described above, according to the present invention, the coefficient of expansion of air in the bellows tube and the coefficient of expansion of air in the tire match each other, so that measurement error can be minimized. Further, since the sliding surface between the members is small, air leakage is unlikely to occur. Since most of them are mounted inside the tire, the load applied to the mounting part is small and the pressure gauge itself can be used stably for a long period of time.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment,

FIG. 2 is an external view showing a tire equipped with the pressure gauge of the embodiment shown in FIG.

FIG. 3 is an enlarged perspective view showing a pressure gauge attachment portion of a tire to which the pressure gauge of FIG. 1 is attached,

FIG. 4 is a side sectional view showing a tire pressure gauge of another embodiment,

5 is a plan view showing the tire pressure gauge shown in FIG. 4,

FIG. 6 is an external view showing a tire to which a tire pressure gauge of yet another embodiment is attached,

FIG. 7 is a side sectional view showing the tire pressure gauge shown in FIG.

FIG. 8 is a side cross-sectional view showing the basic structure of the tire pressure gauge of each of the above embodiments,

FIG. 9 is a side sectional view showing a modified example in which the embodiment is modified.

FIG. 10 is a side sectional view showing another modified example,

FIG. 11 is a side sectional view showing still another modified example,

FIG. 12 is a side sectional view showing a modification different from the modification already shown.

FIG. 13 is a side sectional view showing still another modified example.

[Explanation of symbols]

1, 1c, 1d, 1e, 1f ... Bellows
2 ... indicator rod 3 ... insertion hole 3a
... Penetrating member 4, 4a, 4b, 4c, 4d, 4e, 4f ... Transparent lid 5 ... Valve 5a
… Valve body 6… Packing 7
… Tire 11… Fixed end 1
2 ... Moving end 13, 13c, 13d, 13e, 13f ... Holding member 14 ... Recessed chamber 15 ... Tapered port 15
a ... sleeve 21 ... pressure sensitive plate 30, 30a ... introduction hole 31, 31
a ... Guide hole 32, 32a ... Hollow part 51 ... Spindle valve 5
2 ... valve 53 ... valve seat surface 54 ... inner tube 5
6 ... Valve seat 57 ... Boulder 58 ... Spring 5
9 ... Cover 60 ... Vent hole 61 ... Inner packing 6
3 ... Outer packing 71 ... Tire hob

Claims (10)

[Claims] 1. A tire pressure gauge which is attached to a tire of an automobile to constantly measure the pressure inside the tire, and a bellows which is expandable and air-tight is held inside the tire by a holding member attached to the tire. A tire pressure gauge for isothermal measurement, characterized in that a base end portion of a flexible display rod that is held in the holding member and is housed in an introduction hole formed in the holding member so as to be movable back and forth is attached to the bellows. 2. A holding member having a recessed chamber is formed of a heat conductive material, and an expandable bellows for sealing gas is housed in the recessed chamber of the holding member, and is provided in an introduction hole formed in the bottom of the recessed chamber. The tire pressure gauge for isothermal measurement according to claim 1, wherein a base end portion of a flexible display rod housed so as to be movable back and forth is attached to the bellows. 3. An introduction hole formed in the bottom surface of the concave chamber of the holding member, a guide hole communicating with the introduction hole, and a hollow portion smoothly communicating with the guide hole and extending in an arc shape or a spiral shape to be closed. The tire pressure gauge for isothermal measurement according to claim 1, further comprising a flexible display rod that is housed in an insertion hole that is formed so as to be movable back and forth. 4. A flexible display rod having a base end portion housed in an introduction hole so as to be movable back and forth is attached to a pressure sensitive plate attached to a bellows housed in a concave chamber of a holding member, and the distal end portion of the flexible display rod is mounted. The tire pressure gauge for isothermal measurement according to claim 3, wherein the tire pressure gauge is housed in a hollow portion that extends in an arc shape or a spiral shape that communicates with the introduction hole and the guide hole and is closed so as to be movable back and forth. 5. An advancing / retracting movement operation of a flexible display rod, wherein a hollow portion communicating with the introduction hole and the guide hole is formed into a disc shape, and the hollow portion is accommodated in the introduction hole and the guide hole so as to be able to move back and forth. The tire pressure gauge for isothermal measurement according to claim 3, wherein a disk that rotates in conjunction with is rotatably housed. 6. The tire pressure gauge for isothermal measurement according to claim 5, wherein a transparent lid is attached to a position covering the disk-shaped hollow portion, and a transparent lid having a scale is formed at a position along the outer periphery of the hollow portion. . 7. The charging valve is attached to the holding member so that an introduction hole formed in the holding member and a guide path formed on a fitting surface of the holding member of the charging valve communicate with each other, An outer peripheral surface of a charging valve that communicates with the guide path and a hollow path extending in a circular arc shape or a spiral shape that accommodates the tip of a display rod so as to move forward and backward and to a fitting surface with a holding member of the charging valve. The tire pressure gauge for isothermal measurement according to claim 1, wherein the tire pressure gauge is formed on the outer peripheral surface of which a scale is engraved and a cylindrical transparent lid is fitted. 8. A bellows housed in the recessed chamber, which is installed along the outer surface of the tire by smoothly bending an insertion hole formed in the bottom surface of the recessed chamber of the holding member installed on the inner surface of the tire and extending the same. The isothermal member according to claim 1, wherein a display rod to be attached is housed in the insertion hole so as to be movable back and forth, and a transparent lid covering the insertion hole is attached to the outer surface of the insertion hole extending along the outer surface of the tire. Tire pressure gauge to measure. 9. A bellows tube having a closed end, which is integrally formed with a flexible display rod, is attached to a holding member which is integrally formed with a transparent tube having a graduated scale. The tube and the tube form a closed end for sealing gas, and an indicator rod for displaying the pressure inside the tire is housed in the tube protruding outside the tire so as to be movable forward and backward. Tire pressure gauge. 10. The bellows attached to the holding member is formed in a sealed bag shape for enclosing a gas or a liquid, and one end of the sealed bag-shaped bellows is provided with an end portion that is movable back and forth. Tire pressure gauge for isothermal measurement.