JP2006022919A - Camera platform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress expansion and shrinkage of parts caused by a change in ambient temperatures to reduce a backlash involved especially in a drive mechanism in a camera platform with panning and tilting functions. <P>SOLUTION: The camera platform includes the drive mechanism capable of moving in panning and tilting directions. In the camera platform, a linear expansion coefficient of gears constituting the drive mechanism and that of a support plate for supporting the gears are made to be equal to each other. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pan / tilt head device that rotates an installed surveillance camera, a television camera, or the like in a panning direction or a tilting direction to displace the shooting direction in the vertical and horizontal directions.

  Surveillance cameras are installed on the rooftop of the building, the ceiling in the building, etc. via a pan head device. This surveillance camera rotates in the pan direction and the tilt direction based on the operation of the pan head device, and has a function of photographing a subject in the vertical and horizontal directions.

  A drive mechanism of a conventional pan head apparatus will be described with reference to FIG. Torque generated from the drive generator 1 having a drive motor is transmitted to the small gear 2. The small gear 2 is fastened to the drive generator 1 or is held by a bearing in the drive generator. The drive generator 1 is fastened to an aluminum material fastened to the pan head body 3 and a support plate 4 having a thickness of 6 mm or more. Since the total weight of many pan head devices is 10 kg or more, if the support plate 4 having a thickness of 6 mm or more is not used, the strength is weak, and deformation occurs. A hole for fitting the lower portion of the outer periphery of the bearing 5 is provided in the center portion of the support plate 4, and the lower portion of the outer periphery of the bearing 5 is fitted. A presser ring 8 fastened to the support plate 4 is used to hold the presser on the outer periphery of the bearing 5. The support plate 4 is fastened with a sensor unit 6 for detecting the rotational speed of the gear. The large gear 7 and the bearing 10 hold the inner periphery of the bearing 5. Torque transmitted from the small gear 2 is transmitted to the large gear 7 combined with the bearing 10 fastened to the base 9.

Next, the assembly order of the conventional pan head apparatus will be described. FIG. 6 is an explanatory diagram of the assembly order.
(1) The lower part of the outer peripheral portion of the bearing 5 is fitted into the fitting surface at the center of the support plate 4.
(2) The presser ring 8 is fastened to the support plate 4 to fix the bearing 5 in order to press down the upper part of the outer periphery of the bearing 5.
(3) Insert the large gear 7 into the fitting surface of the bearing 5. Next, the bearing 10 is similarly inserted into the bearing 5, and the large gear 7 and the bearing 10 are fastened.
(4) Fasten the assembled parts to the pedestal 9 and the platform body 3.
(5) The drive generating unit 1 and the sensor unit 6 constituting the small gear 2 are attached to the support plate 4.

  The drive mechanism was attached to the pan head main body 3 using the above method. The backlash adjustment between the large gear 7 and the small gear 2 cannot be performed unless the drive mechanism is attached to the pan head body 3.

The pan / tilt head device is required to perform a pan / tilt operation in a temperature range of −20 ° C. to + 40 ° C. in the product specifications. In general, since the component material constituting the pan head device expands and contracts due to a change in temperature, large thermal expansion and contraction also occur in the parts constituting the drive mechanism of the pan head device. Conventionally, an iron-based material having a linear expansion coefficient of 9.6 to 12.0 × 10 ⁻⁶ / ° C. is used in the gear portion, and a linear expansion coefficient of 2.15 to a support plate formed in the bearing portion. 2.36 × 10 ⁻⁵ / ° C. aluminum, an alloy for aluminum casting, and an alloy for aluminum die casting were used.

  The problem of backlash has been well known, and an example is an electric motor that generates an auxiliary steering torque of an electric power steering device (Patent Document 1). In this document, a core metal resin gear having resin teeth formed around a cylindrical core metal is used as a driven gear of a gear device that transmits the rotational output of an electric motor. This is to prevent the generation of noise between the driving gear and the driven gear by using resin teeth. However, in the gear made of the core metal resin, the linear expansion coefficient of the resin portion is much larger than that of the metal, so that there is a problem that the backlash allowable range is exceeded when the temperature environment changes greatly. With respect to this problem, Patent Document 1 discloses that the backlash amount can be kept substantially constant by appropriately determining the thickness of the resin portion.

Patent Document 2 similarly relates to backlash of an electric steering device. The pitch circle diameter φd of a metal worm, the diameter φD of a fitting body of a worm wheel having an annular tooth body made of synthetic resin and a metal fitting body fitted inside the annular tooth body, The thickness t from the inside to the pitch circle, the distance L between the centers of the support holes of the aluminum housing, the linear expansion coefficient α of the worm and the fitting body, the linear expansion coefficient β of the annular tooth body, and the linear expansion coefficient γ of the housing if you did this,
γL≈α (φD / 2 + φd / 2) + βt
It is disclosed that the annular tooth body and the fitting body are formed so that
JP 2003-118600 A JP2002-039331

  As described above, a pan head capable of pan / tilt operation is required to operate in a temperature range of −20 ° C. to + 40 ° C. according to product specifications. However, normal operation of the pan / tilt head device may be hindered by the thermal expansion and contraction of components in such a temperature range of 60 ° C. In the drive mechanism of the conventional pan head apparatus, the gear portion has a relatively small linear expansion coefficient, while the linear expansion coefficient of the support plate that supports the gear portion has a relatively large value. When the linear expansion coefficients are different from each other in this way, the mutual positional relationship changes due to a difference in expansion amount due to a temperature change. For this reason, conventionally, when assembling the gear portion at a normal temperature of 27 ° C., the backlash is designed to occur at normal temperature in consideration of the backlash of 2 to 7 minutes. This is to avoid the fact that the distance between the shafts of the gear portion becomes narrow and the resistance between the gears increases due to the shrinkage of the aluminum-based support plate having a relatively small linear expansion coefficient at a low temperature. However, the backlash amount of the gear portion at normal temperature for 2 to 7 minutes has caused a backlash in the image provided from the lens device mounted on the pan head. At high temperatures, more backlash will occur.

  In addition, since the measurement of the backlash of the conventional gear unit is performed with the support plate and the gear unit assembled on the pan head body, the backlash measurement is judged from the image of the imaging device mounted on the pan head. Or measuring a backlash by providing a measurement point on the pan head body. Thus, in the conventional pan head apparatus, the backlash cannot be measured unless the gear section is assembled to the pan head main body.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a drive mechanism for a pan head apparatus that reduces backlash of a gear portion and simplifies a backlash measurement method.

  A pan head apparatus of the present invention that achieves the above object is a pan head apparatus having a drive mechanism that can be driven in a pan direction and a tilt direction, and includes a linear expansion coefficient of a gear part constituting the drive mechanism and the gear part. The support plates to be supported are characterized by equal linear expansion coefficients. Since the thermal expansion amount and shrinkage amount of the parts due to temperature change are equal, it has the effect of reducing the backlash fluctuation amount.

  Furthermore, the pan head device of the present invention is a pan head device having a drive mechanism that can be driven in the pan direction and the tilt direction, and the drive generating portion, the gear portion, the sensor portion, and the bearing portion constituting the drive mechanism are integrated. It is characterized by doing. The backlash measurement can be performed without assembling the support plate and the gear portion on the pan head body, and the backlash measurement can be performed more easily than in the past.

  According to the present invention, it is possible to reduce the backlash fluctuation amount by selecting a material in which the linear expansion coefficient of the gear portion included in the drive mechanism and the linear expansion coefficient of the support plate are substantially the same. Furthermore, the backlash can be easily measured by integrating the drive mechanism.

  The details of the present invention will be described in detail with reference to the embodiments shown in the drawings.

(First embodiment)
The drive mechanism of the pan head apparatus of the present invention will be described with reference to FIG.

  The drive mechanism generates torque from a drive generator 1 having a drive motor and transmits the torque to the small gear 2. The small gear 2 is fastened to the drive generator 1 or is held by a bearing in the drive generator 1. The drive generator 1 is fastened to a support plate 11 having a thickness of 3 mm and an iron-based material fastened to the pan head body 3. Since iron-based materials are stronger than aluminum, a thickness of 3 mm has sufficient strength. A hole for fitting the lower part of the outer periphery of the bearing 5 is provided at the center of the support plate 11, and the lower part of the outer periphery of the bearing 5 is fitted. A presser ring 8 fastened to the support plate 11 is used to hold the presser on the outer periphery of the bearing 5. The support plate 11 is fastened with a sensor unit 6 for detecting the rotational speed of the gear. The large gear 7 and the bearing 10 hold the inner periphery of the bearing 5. Torque transmitted from the small gear 2 is transmitted to the large gear 7 combined with the bearing 10 fastened to the base 9.

  FIG. 2 is a schematic perspective view for explaining the relationship between the gear portion and the support plate 11. Table 1 shows the specifications regarding the shapes of the large gear 7 and the small gear 2 in the present embodiment. Table 2 shows the linear expansion coefficients of various materials.

  FIG. 2 shows three types of components, a small gear 2, a support plate 11, and a large gear 7, which occupy a large factor with respect to fluctuations in the amount of backlash due to temperature changes. This is because the support plate 11 is thermally expanded and contracted due to a change in temperature condition, and the distance between the shafts of the small gear and the large gear is changed. In this example, three combinations of materials were prepared for these three types of components, and the backlash amount when the temperature condition was changed was calculated for each. The combinations of the three materials are as follows. Since the iron head material is often used for the gear of the pan head device, medium carbon steel is used for the small gear 2 and the large gear 7. For the support plate 11, conventionally used aluminum was used, SUS304 was used for Example 1-1, and SCM440 was used for Example 1-2.

  In the calculation of the backlash amount, the gear distance between the gears is set to 50 mm, the large gear 7 and the small gear 2 having the specifications shown in Table 1 are meshed, and the temperature is changed to + 40 ° C. with an initial value of −20 ° C. I let you.

  FIG. 4 shows the amount of backlash when the temperature is changed in the temperature range of −20 ° C. to 40 ° C. under the above calculation conditions. The amount of backlash was 2 minutes when medium carbon steel was used for the small and large gears and aluminum was used for the support plate as in the conventional case. On the other hand, in Example 1-1 using SUS304 as the support plate, the time was 1.1 minutes, and in Example 2-2 using SCM440 as the support plate, the time was 0.2 minutes. From the above results, it can be seen that the backlash amount can be greatly reduced by making the linear expansion coefficients of the gear portion and the support plate 11 substantially equal.

As the material of the support plate 11, stainless steel, heat resistant steel, carbon steel, Cr—Mo steel, Ni—Cr steel, Ni—Cr—Mo steel having a linear expansion coefficient of 9.0 to 18.0 × 10 ⁻⁶ / ° C. It is desirable to use carbon tool steel, alloy tool steel, high speed tool steel, sulfur composite free-cutting steel, bearing steel, silicon magnetic steel, nickel base alloy, cobalt base alloy and iron-based materials.

  Even if the gear material is other than iron, it is possible to reduce the backlash amount by using a material having a value close to the linear expansion coefficient of the gear for the material of the support plate 11.

(Second embodiment)
The assembly order of the pan / tilt head device according to the present invention will be described. FIG. 3 is an explanatory diagram of the assembly order.
(1) The lower part of the outer peripheral portion of the bearing 5 is fitted into the fitting surface at the center of the support plate 11.
(2) The presser ring 8 is fastened to the support plate 11 and the bearing 5 is fixed in order to press the outer periphery from above.
(3) Insert the large gear 7 into the surface of the bearing 5. Next, the bearing 10 is similarly inserted into the bearing 5, and the large gear 7 and the bearing 10 are fastened.
(4) The drive generator 1 and the sensor unit 6 constituting the small gear 2 are attached to the support plate 11. At this time, the part shown inside the two-dot chain line becomes a drive mechanism, and shows a unitized state.
(5) The above-described assembled parts are assembled into the camera platform body 3 and the base 9.

  The drive mechanism can be unitized by designing the drive mechanism so that the assembly order is as described above. For this reason, since the backlash adjustment can be performed using only the unit of the drive mechanism without attaching the drive mechanism to the pan head main body at the time of the assembly sequence (4), according to the present invention, the backlash can be reduced more than before. Measurement is simplified.

Explanatory drawing of the drive mechanism of the pan head apparatus concerning this invention Schematic configuration diagram of gear and support plate Explanatory drawing of the assembly order of the pan head apparatus concerning this invention Graph of backlash when temperature changes Explanatory drawing of drive mechanism of conventional pan head device Explanatory drawing of assembly order of conventional pan head device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive generating part 2 Small gear 3 Pan head main body 4 Support plate 5 Bearing 6 Sensor part 7 Large gear 8 Presser ring 9 Base 10 Bearing 11 Support plate

Claims (2)

  A pan head apparatus having a drive mechanism that can be driven in a pan direction and a tilt direction, wherein a linear expansion coefficient of a gear portion that constitutes the drive mechanism is equal to a linear expansion coefficient of a support plate that supports the gear portion. A pan head device. A pan head device having a drive mechanism that can be driven in a pan direction and a tilt direction, wherein a drive generation unit, a gear unit, a sensor unit, and a bearing unit constituting the drive mechanism are integrated. .

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