Interior measuring instrument

Abstract

Head part (200) of an interior measuring instrument (100) that measures an interior of a measurement target object, the head part (200) comprising: a head main body part (300); a measuring head (400) including a spherical measuring surface (430) on one end surface and slidably provided by passing through an inner space and an outer space of the head main body part (300); a guide member (230) having an opening in a lower surface, slidably disposed in a displacement direction of the measuring head (400) on one side of the head main body part (300) and biased in a protruding direction from the head main body part (300); a rod (210) movable in a direction perpendicular to a direction of movement of the measuring head (400); and a cam (330) provided between the other end of the measuring head (400) and the rod (210) and rotatably supported about an axis by the head main body part (300); wherein: the measuring head (400) includes a spring retaining groove (450) which is introduced in a circumferential direction at the other end side, a compression coil spring (500) is arranged between the spring retaining groove (450) and an interior end surface (324) of the head main body part (300); the compression coil spring (500) includes a diameter that accommodates or receives the measuring head (400) within it, and a diameter of an end turning part (520) corresponding to the other end of the measuring head (400) is smaller than the other part to be fitted to the spring retaining groove (450); the end turning part (520) is fitted to the spring retaining groove (450) and thus the compression coil spring (500) is arranged on the measuring head (400); and the compression coil spring (500) biases the measuring head (400) in the direction opposite to the protruding direction.

Description

Inclusion by reference

[0001] This application is based on Japanese Patent Application No. 2015-027800 filed on February 16, 2015, and claims the benefit of priority therefrom. Background of the invention 1. Field of the invention

[0002] The present invention relates to an interior measuring instrument. 2. Description of the state of the art

[0003] A bore gauge or internal measuring instrument is already known as an internal measuring instrument that measures the inner diameter of a hole or the dimension of the inner width of a groove.

[0004] The bore gauge or internal gauge measures the displacement of a measuring head by converting the displacement into the displacement of a rod in a direction perpendicular to the measuring head.

[0005] JP 2003-28 603 A describes a dimension measuring device with a movable rod and a pair of measuring heads arranged at one end of the rod. JP H07-14 237 U describes a compression spring with an inwardly bent end.

[0006] A thin-bottom type bore gauge or internal measuring device is already known as a bore gauge or internal measuring device, which is suitable for measuring a diameter near a bottom of a flat hole or a hole with a bottom (blind hole or blind hole) (JP S62-44327 Y).

[0007] First, a thin-bottomed bore gauge or internal gauge is briefly described.

[0008] Fig. 1 is an external view of a bore gauge or internal gauge 100.

[0009] Fig. 2 is an enlarged view of a headboard 200.

[0010] The head portion 200 of the bore gauge 100 will now be mainly described as background of the present invention.

[0011] Fig. 3 is a cross-sectional view of the head part 200.

[0012] Fig. 4 is an exploded perspective view of the head part 200.

[0013] The head portion 200 of the bore gauge or internal gauge 100 includes a head main body portion 300, a lower rod 210, a measuring head 400, an anvil 240, and a guide member 230.

[0014] An outer diameter screw portion 310 is formed at the upper end of the head main body portion 300. The outer diameter screw portion 310 is screwed into and fixed to one end of a cylindrical body 110. A spindle (not shown) is inserted into the cylindrical body 110. The spindle is installed to be movable in an axial direction. A clamp holder 111 is mounted on the other end of the cylindrical body 110, and the clamp holder 111 holds a stem (not shown) of a dial gauge (not shown). The dial gauge (not shown) detects the amount of movement of the spindle (not shown).

[0015] A first hole 321 is drilled in the head main body part 300 along the axial line of the outer diameter screw part 310.

[0016] The lower rod 210 is inserted into the first hole 321, and the lower rod 210 and the spindle (not shown) are coaxial and movable along the coaxial line. Thus, an upper end 211 of the lower rod 210 is in point contact with a lower end of the spindle (not shown), and the lower rod 210 and the spindle (not shown) move together.

[0017] Note that a first compression coil spring (not shown) is disposed between the lower rod 210 or the spindle (not shown) and the cylindrical body 110, and the lower rod 210 or the spindle (not shown) is biased downward (toward the lower end side of the cylindrical body 110).

[0018] A bottom surface 302 of the head main body part 300 is machined to be flat. Furthermore, a second hole 322, which communicates with and is perpendicular to the first hole 321, is drilled into the interior of the head main body part 300 on the side opposite the bottom surface 302. The measuring head 400 is inserted into the second hole 322 and moves freely back and forth. The front-to-back direction of the measuring head 400 is perpendicular to the moving direction of the spindle (not shown) and the lower rod 210.

[0019] A right-triangular cam 330 is rotatably supported about an axis at an intersection point of the first hole 321 and the second hole 322. The base end of the measuring head 400 is in contact with one cam surface of the cam 330, and the lower end of the lower rod 210 is in contact with the other cam surface perpendicular to the one cam surface. The cam 330 converts the amount of forward and backward movement of the measuring head 400 into a right-angle direction and transmits the converted amount to the lower rod 210.

[0020] A long groove 420 with a predetermined length along the axial line is provided on the outer surface of the measuring head 400, and a tip end of a locking plate 340 is engaged in the long groove 420. The locking plate 340 is pressed in from the bottom surface 320 of the head main body part 300.

[0021] The locking plate 340 and the long groove 420 form a stopper which is the limit for the forward movement and the limit for the rearward movement of the measuring head 400.

[0022] The lower rod 210 or the spindle (not shown) is biased downward by the first compression coil spring (not shown), and the measuring head 400 is continuously biased in a protruding direction from the head main body part 300.

[0023] The anvil 240 is screwed into the head main body portion 300 on the opposite side to the measuring head 400.

[0024] The guide member 230 is provided on the right side of the head main body part 300, slidably displaceable in the front-to-back direction of the measuring head 400 in the drawing. The head main body part 300 has a groove 304 in the center of the end surface on the side facing the measuring head 400 and has a substantially U-shape when viewed from the side. The opening of the groove 304 is parallel. The guide member 230 has a first groove 231 and a substantially U-shape when viewed in plan. The opening of the first groove 231 is vertical. Furthermore, the guide member 230 has a second groove 232 at the lower part of the guide member 230. The second groove 232 is perpendicular to the first groove 231 and has an opening in the lower surface.

[0025] The guide member 230 is engaged with the groove 304 of the head main body part 300 from the front side (one side) of the head main body part 304. At this time, the first groove 231 and the second groove 232 of the guide member 230 are fitted to the side surface of the head main body part 300.

[0026] Thus, the guide member 230 is guided to the side surface of the head main body part 300 and moves freely forward and backward.

[0027] A second compression coil spring 233 is arranged between the guide member 230 and the head main body part 300.

[0028] Considering the function of the second compression coil spring 233, the guide member 230 is continuously biased in a protruding direction from the head main body part 300.

[0029] A screw 306 is screwed into the head main body portion 300 from the front (one side). The head of the screw 306 is engaged by the front end of the guide member 230 and serves as a stopper for the guide member 230.

[0030] While the guide member 230 is engaged with the head main body 300, the guide member 230 has a substantially gate shape with symmetry with respect to the central axis of the measuring head 400 to cover the measuring head 400 from above. Furthermore, a semicircular protrusion 236, which is a protrusion substantially in the shape of a semicircle, is integrally formed on the right side of the guide member 230 in the drawing. The center of the circular protrusion 236 coincides with the axial line of the measuring head 400, and the circumference of the circular protrusion 236 is smoothly round-chamfered. When the semicircular protrusion 236 is firmly brought into contact with a measurement target surface, such as a hole, the measuring head 400 must be brought into perpendicular contact with the measurement target surface.The amount of forward and backward movement of the measuring head 400 at this time is transmitted to the dial indicator (not shown) through the lower rod 210 and the spindle (not shown), and a measured value of an inner diameter is accordingly obtained from a value displayed on the dial indicator (not shown).

[0031] In the above-described structure, a large part of the components of the head part 200 are provided above the axial line of the measuring head 400.

[0032] Thus, the size between the axial line of the measuring head 400 and the bottom surface 302 of the head main body part 300 is shortened accordingly, and the bore gauge 100 is suitable for measuring a diameter near a bottom of a flat hole or a blind hole.

[0033] Specifically, the biasing means such as a spring is not directly provided on the measuring head 400, and the force of the first compression coil spring (not shown) is biased or generated by indirectly transmitting it to the measuring head 400 through the lower rod 210 or the spindle (not shown). Therefore, the size from the central axis of the measuring head 400 to the bottom surface 302 should be shortened. Summary of the invention

[0034] When measuring the inner diameter of a hole with the bore gauge 100, the measuring head 400 is pushed back toward the inner diameter by the measurement target surface. Then, the head portion 200 is withdrawn from the hole in this state, and the measuring head 400 is allowed to move forward in the protruding direction under the force of the first compression coil spring (not shown). The stopper (locking plate 340) prevents the measuring head 400 from falling out.

[0035] However, when the measuring head 400 hits the stopper (locking plate 340), a strong impact acts on the stopper (locking plate 340), the measuring head 400 and the head main body part 300, whereupon the reaction acts on the cam 330, the lower rod 210 and the spindle (not shown).

[0036] After the measurement has been repeated tens of thousands or hundreds of thousands of times, the damage to the components is great, which affects the service life.

[0037] Although the bore gauge or internal gauge may have the above-described problem with the service life, no damping means are provided between the measuring head 400 and the head main body part 300 so that the structure with the thin bottom can be maintained.

[0038] An object of the present invention is to provide a thin-bottom type bore gauge having damping means between a gauge head and a head main body portion and a long service life.

[0039] A head part of an interior measuring instrument that measures an interior of a measurement target object includes, in an exemplary embodiment of the present invention: a head main body part; and a measuring head including a spherical measuring surface on one end surface and slidably provided by passing through an inner space and an outer space of the head main body part, wherein the measuring head includes a spring retaining groove which is introduced in a circumferential direction at the other end side, and a compression coil spring is arranged between the spring retaining groove and an interior end surface of the head main body part.

[0040] In an exemplary embodiment of the present invention, it is preferred that the compression coil spring includes: a diameter that accepts or accommodates the measuring head within this, and wherein a diameter of an end turning part corresponding to the other end of the measuring head is smaller than other parts to be fitted to the spring retaining groove.

[0041] In an exemplary embodiment of the present invention, it is preferred that the head portion further includes: a rod movable in a direction perpendicular to a direction of movement of the measuring head; and a cam provided between the other end of the measuring head and the rod and rotatably supported about an axis by the head main body part, wherein the measuring head and the rod are ceramic at end surfaces or as a whole.

[0042] A head part of an interior measuring instrument that measures an interior of a measurement target object includes, in an exemplary embodiment of the present invention: a head main body part; a measuring head including a spherical measuring surface on one end surface and being movable by passing through an inner space and an outer space of the head main body part; a rod movable in a direction perpendicular to a direction of movement of the measuring head; and a cam provided between the other end of the measuring head and the rod and rotatably supported about an axis by the head main body part, wherein the measuring head and the rod are ceramic at end surfaces or as a whole.

[0043] An interior measuring instrument in an exemplary embodiment of the present invention includes the head portion.

[0044] In an exemplary embodiment of the present invention, it is preferred that the interior measuring instrument further includes: Preloading means for preloading the rod in a direction toward the cam, wherein a preload force of the compression coil spring is equal to or greater than the preload force of the preloading means, and The headboard also includes: a rod movable in a direction perpendicular to a direction of movement of the measuring head; and a cam provided between the other end of the measuring head and the rod and rotatably supported about an axis by the head main body portion. Short description of the drawing Fig. 1 is an external view of a bore gauge or internal gauge. Fig. 2 is an enlarged view of a headboard. Fig. 3 is a cross-sectional view of the head part. Fig. 4 is an exploded perspective view of the headboard. Fig. 5 is a diagram to explain a problem. Fig. 6 is a cross-sectional view of the present exemplary embodiment. Fig. 7 is a diagram illustrating a measuring head of the present exemplary embodiment. Fig. 8 is a diagram showing a third compression coil spring. Detailed description

[0045] A first characteristic of an exemplary embodiment of the present invention is that a third compression coil spring is provided between a head main body part 300 and a measuring head 400 (see Fig. 6). Before describing the specific structure of an exemplary embodiment of the present invention, Fig. 5 describes a problem that occurs when only one common or general coil spring 50 is present.

[0046] As in Fig. 5, when only the coil spring 50 is to be arranged between the head main body part 300 and the measuring head 400, the following problem occurs.

[0047] If the coil spring 50 is to be arranged between the head main body part 300 and the measuring head 400, a flange 410 for holding a spring on the measuring head 400, as in Fig. 5. However, the diameter of the measuring head 400 must now be increased to accommodate the flange 410, and excessive space must be provided below the axis, which is undesirable given the task of measuring a shallow hole.

[0048] Furthermore, when the coil spring 50 is arranged between the head main body part 300 and the measuring head 400, a holding part 350 of the measuring head 400 must be shortened to accommodate the coil spring 50. Therefore, the operation of the measuring head 400 may be unstable.

[0049] Furthermore, if a partial protrusion, such as the flange 410, is provided on the measuring head 400, the machining effort (cutting effort) is significantly increased. Various solutions exist to make the measuring head 400 and the head main body part 300 more complex to machine. However, it is undesirable if the machining effort and cost do not reflect the downward trend in prices.

[0050] Due to the above-described problem, despite the thin-bottom type bore gauge 100 having a problem in durability, no damping means has been provided between the gauge head 400 and the head main body part 300.

[0051] Exemplary embodiments of the present invention will now be illustrated and described with reference to the reference numerals assigned to the elements in the drawings. First exemplary embodiment

[0052] A first exemplary embodiment of the present invention will now be described.

[0053] As in Fig. 6, the first characteristic of the present exemplary embodiment is that a third compression coil spring 500 (see Fig. 6) is arranged between a head main body part 300 and a measuring head 400.

[0054] The present exemplary embodiment is in Fig. 6 to 8.

[0055] In Fig. 6, the head main body portion 300 includes a first hole 321 and a second hole 322 perpendicular to the first hole 321. At the intersection point of the first hole 321 and the second hole 322, the diameter of the first hole 321 is enlarged, and a cam 330 is disposed in a space formed thereby. This space will be referred to as the cam disposing space 325 hereinafter.

[0056] The measuring head 400 is slidably inserted to one side of the second hole 322 through the interposition of the cam 330. Therefore, the hole of the second hole 322 on the side where the measuring head 400 is disposed is referred to as the measuring head hole 323. Note that the inner surface of the measuring head hole 323 is equivalent to a holding part 350 that holds the measuring head 400.

[0057] In the head main body part 300, the edge of the opening on the other side of the measuring head hole 323 is an end surface 324 perpendicular to the axial line of the measuring head hole 323. The end surface 324 is, as will be understood from the following description, an end surface for holding the spring and is referred to as a spring holding end surface 324.

[0058] Fig. 7 is a diagram illustrating the measuring head 400 of the present exemplary embodiment.

[0059] The measuring head 400 has an overall columnar shape and includes a spherical measuring surface 430 at one end face and a cam contact surface 440 at the other end face. The cam contact surface 440 is brought into contact with the cam 330. The measuring head 400 includes a groove line 450 formed circumferentially at the other end face. The groove line 450, as will be apparent from the following description, is the groove for holding the spring and is referred to as the spring holding groove 450.

[0060] Note that the part to be engaged with the locking plate 340, such as the long groove 420, is not required in the present exemplary embodiment.

[0061] When the measuring head 400 is inserted into the measuring head hole 323, the spring retaining groove 450 protrudes to the other side more than the spring retaining end surface 324. Then, the third compression coil spring 500 is installed between the spring retaining groove 450 and the spring retaining end surface 324.

[0062] Fig. 8 is a diagram showing the third compression coil spring 500. In Fig. 8, the end turn portion on the right side (one side) is brought into contact with the spring retaining end surface 324, while the end turn portion on the left side (the other side) is engaged with the spring retaining groove 450. The end turn portion on the right side (one side) is referred to as the first end turn portion 510, while the end turn portion on the left side (the other side) is referred to as the second end turn portion 520.

[0063] The diameter of the third compression coil spring 500 is slightly larger than that of the measuring head 400, and the measuring head 400 is accurately housed within the third compression coil spring 500. However, the diameter of the second end turning part 520 is smaller than the other parts, and the second end turning part 520 is fitted to the spring retaining groove 450.

[0064] With the above-described structure, the third compression coil spring 500 biases the measuring head 400 to the other side by receiving the reaction from the spring holding end surface 324. In other words, the third compression coil spring 500 biases the measuring head 400 in the direction opposite to the protruding direction, that is, in the direction in which the measuring head 400 is retracted. While a first compression coil spring (not shown) biases a spindle (not shown) or a lower rod 210 in the protruding direction (downward), the third compression coil spring 500 biases the measuring head 400 in the direction opposite to the force direction of the first compression coil spring (not shown).

[0065] Note that the first compression coil spring (not shown) is stronger than the third compression coil spring 500.

[0066] With the above-described structure, while maintaining the thin bottom, it is possible to arrange the third compression coil spring 500 between the measuring head 400 and the head main body part 300. In the third compression coil spring 500 used, the diameter thereof is not fixed, but the diameter of the second end turning part 520 is small. For example, when a coil spring with a fixed diameter is used, the spring holding flange 410 on the measuring head 400 must be provided as shown in Fig. 5, and the thin bottom cannot be maintained. In contrast, a small-diameter coil spring of the second end turn portion 520 is employed in the present exemplary embodiment, and the coil is held by the circumferential groove (spring holding groove) 450 on the side corresponding to the measuring head 400. This makes it possible to provide damping means between the measuring head 400 and the head main body portion 300 while maintaining a thin bottom.

[0067] Furthermore, the end turning part (second end turning part 520) is engaged with the spring retaining groove 450, which results in excellent space efficiency compared to the case where the spring is supported, for example, by the spring retaining flange (see 410 in Fig. 5), thereby ensuring the length of the holding part 350. This results in stable operation of the measuring head 400.

[0068] The third compression coil spring 500 prevents the measuring head 400 from jumping out, and a locking plate (stopper) is not required in the present exemplary embodiment. The operational clearance limit of the measuring head 400 is regulated by an elastic member, which is the third compression coil spring 500, and the components (locking plate 340 and measuring head 400) do not interfere with each other, resulting in a long service life and improved measurement accuracy.

[0069] Since the locking plate 340 is not required, a bottom surface 302 of the head main body part 300 does not have to absorb a large force. This makes it possible to design the bottom surface 302 of the head main body part 300 accordingly thin. Modified Example 1

[0070] In the exemplary embodiment described above, it has been described that the first compression coil spring (not shown) is stronger than the third compression coil spring 500.

[0071] Conversely, however, the third compression coil spring 500 may be stronger than the first compression coil spring (not shown). In this case, the measuring head 400 is normally retracted. Thus, after the head portion 200 is inserted into a hole or groove that is the measurement target W, the spindle (not shown) (or the lower rod) is slowly pushed down, and the spherical measuring surface 430 is brought into contact with the measurement target W.

[0072] Alternatively, the third compression coil spring 500 and the first compression coil spring (not shown) may have substantially the same strength.

[0073] Alternatively, the first compression coil spring (not shown) may not be provided. As long as the third compression coil spring 500 is provided, the spindle (not shown), the lower rod 210, and the measuring head 400 operate in response to mutual movements. Modified Example 2

[0074] It is preferable that the cam contact surface 440 of the measuring head 400 and the cam contact surface 220 of the lower rod 210 be formed of high-hardness materials, such as ceramic. The measuring head 400 and the lower rod 210 may be formed of ceramic not only on the end surfaces but also entirely. When the third compression coil spring 500 is provided similarly to the exemplary embodiments described above, the lower rod 210 and the measuring head 400 push each other with the cam 330 sandwiched therebetween. Thus, the force exerted on the cam contact surface 440 of the measuring head 400 and the cam contact surface 220 of the lower rod 210 becomes correspondingly larger. In addition, it is preferable that the cam contact surface 440 of the measuring head 400 and the cam contact surface 220 of the lower rod 210 are formed of materials with high hardness and excellent wear resistance.In addition, when the lower rod 210 and the measuring head 400 are formed entirely of high-hardness materials such as ceramics, the wear of the entire sliding surface is reduced, and the service life of the bore gauge or internal gauge 100 is extended.

[0075] Note that only the ceramic must have high hardness and excellent wear resistance, while the material of the components themselves is not limited. In one example, a sintered body with zirconium oxide (ZrO2) or aluminum oxide (Al2O3) as the main component, with a hardness of HV 1200 or greater, is preferred.

[0076] Note that the present invention is not limited to the above-described exemplary embodiments, and a structure modified accordingly without departing from the spirit of the invention also belongs to the technical scope of the present invention.

Claims

[1] Head part (200) of an interior measuring instrument (100) which measures an interior of a measurement target object, the head part (200) comprising: a head main body part (300); a measuring head (400) including a spherical measuring surface (430) on one end surface and slidably provided by passing through an inner space and an outer space of the head main body part (300); a guide member (230) having an opening in a lower surface, slidably disposed in a displacement direction of the measuring head (400) on one side of the head main body part (300) and biased in a protruding direction from the head main body part (300); a rod (210) movable in a direction perpendicular to a direction of movement of the measuring head (400); and a cam (330) provided between the other end of the measuring head (400) and the rod (210) and rotatably supported about an axis by the head main body part (300); wherein: the measuring head (400) includes a spring retaining groove (450) which is introduced in a circumferential direction at the other end side, a compression coil spring (500) is arranged between the spring retaining groove (450) and an interior end surface (324) of the head main body part (300); the compression coil spring (500) includes a diameter that accommodates or receives the measuring head (400) within it, and a diameter of an end turning part (520) corresponding to the other end of the measuring head (400) is smaller than the other part to be fitted to the spring retaining groove (450); the end turning part (520) is fitted to the spring retaining groove (450) and thus the compression coil spring (500) is arranged on the measuring head (400); and the compression coil spring (500) biases the measuring head (400) in the direction opposite to the protruding direction. [2] Head part (200) of an interior measuring instrument (100) according to claim 1, wherein the end surfaces or the entirety of the measuring head (400) are ceramic. [3] Head part (200) of an interior measuring instrument (100) according to claim 1 or 2, wherein the end surfaces or the entirety of the rod (210) are ceramic. [4] Head part (200) of an interior measuring instrument (100) according to one of claims 1-3, further comprising: Preloading means, in particular a spring, for preloading the rod (210) in a direction towards the cam (330), wherein a preload force of the compression coil spring (500) is equal to or greater than a preload force of the preloading means. [5] Interior measuring instrument (100) comprising a head part (200) according to one of claims 1-4.

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