JPH0481766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a zoom lens barrel, and particularly to a zoom lens barrel having a structure suitable for plastic molding.

[Background of the invention]

The zoom part of a zoom lens barrel is basically
A cam ring is inserted inside the fixed main cylinder, and a zoom ring for zoom operation is provided on the outside of the main cylinder.The side wall of the main cylinder has a rotation regulating groove in the circumferential direction. There are long grooves called
The cam ring and the zoom ring are connected by a pin that passes through the rotation regulating groove.

When the operator rotates the zoom ring in the circumferential direction, the cam ring is also rotated, and a predetermined optical system is moved in the optical axis direction by a cam groove formed in the cam ring, thereby performing a zoom operation.

Here, if there is any play in the optical axis direction in the cam ring (hereinafter referred to as cam ring thrust play), the smoothness of the zoom operation will be impaired, images may be skipped, and the zoom operation will become unstable.

In order to eliminate this problem, conventionally,
Measures are taken to prevent cam ring thrust play, as described in No. 60824.

According to this, a plurality of balls are rotatably provided on one end surface of the cam ring, and the cam ring is supported by a leaf spring material provided in the main cylinder via these balls. Therefore, the cam ring is elastically biased in one direction in the optical axis direction by the leaf spring material.
This eliminates the occurrence of cam ring thrust play.

However, such a structure is complicated, and since it is made of aluminum, it is expensive and heavy. Further, the influence on the cam groove formed in about half of the side wall of the cam ring is not taken into account.

On the other hand, in recent years, attention has been paid to reducing the weight and cost of zoom lens barrels by using plastic. However, generally, plastic parts are subject to variations in molding conditions and expansion and contraction due to temperature, so there has been a problem that cam ring thrust play is likely to occur.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive zoom lens barrel that eliminates the drawbacks of the prior art described above, reduces cam ring thrust play, and is inexpensive.

[Summary of the invention]

In order to achieve this object, the present invention provides a cam ring play regulating groove on one end side of the inner surface of the main cylinder, and a rotation regulating groove on the one end of the main cylinder,
On the other hand, a flange is provided at one end of the outer surface of the cam ring, and the flange is fitted into a cam ring play regulating groove provided in the main cylinder to rotatably hold the cam ring inside the main cylinder. Further, by providing a notch groove on the one end of the cam ring and a connecting protrusion on the inner surface of the zoom ring, and fitting the connecting protrusion into the notch through the rotation regulating groove, the cam ring and the zoom ring are integrally connected, and the width of the cam ring backlash regulating groove and the flange is made sufficiently small to sufficiently suppress cam ring thrust play, and the main cylinder can be made of plastic. It is distinctive in that it did so.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of a zoom lens barrel according to the present invention, showing a portion of the zoom lens barrel above the optical axis. Figures 2 to 4
The figure is a sectional view of main parts showing each part of FIG. 1,
FIG. 2 shows the main cylinder, FIG. 3 shows the cam ring, and FIG. 4 shows the zoom ring. Note that FIG. 4a is a longitudinal sectional view of the zoom ring, and FIG. 4b is a plan view of the main part thereof.

In these figures, 3 is the main cylinder, 4 is a cam ring rattling regulating groove, 5 is a cam ring, 6 is a flange, 7 is a rotation regulating groove, 8 is a zoom ring, 9 is a connecting projection, 10 is a notch groove, 11 is an indicator ring, 12 and 12' are presser plates,
13 is a guide rod, 14 and 15 are holding frames, 16,
17 is a protrusion, and 18 and 18' are cam grooves.

In FIG. 1, the main cylinder 3 is attached to presser plates 12 and 12' that are provided facing each other in the optical axis direction, and the inner cam ring of the main cylinder 3 is rotatable, and the zoom ring 8 is rotatable on the outer side. It is attached.

The main cylinder 3, as shown in more detail in FIG.
A cam ring backlash regulating groove 4 is provided on the inner wall on the imaging lens side (right side in the drawing), and a rotation regulating groove 7 is provided at the end on the imaging lens side. This main cylinder 3
However, as shown in FIG. 1, when attached to the holding plates 12, 12', the rotation regulating groove 7 becomes a through groove whose width is regulated by the holding plate 12.

As shown in more detail in FIG. 3, the cam ring 5 is provided with a protruding flange 6 at the end of its outer wall, and a notch groove is provided at the side end of the flange 6. . Furthermore, two substantially spiral cam grooves 18, 1 are provided on the side wall of the cam ring 5.
8' is provided. This flange 6 is the first
As shown in the figure, it is slidably fitted into the cam ring rattling regulating groove of the main cylinder 3. Further, the outer end of the cam groove 5 on the side of the presser plate 12' protrudes slightly, and this protrusion comes into sliding contact with the inner wall of the main cylinder 3. That is, since this protrusion is on the inner wall of the main cylinder 3 and the flange 6 is fitted into the cam ring rattling regulating groove 4 provided in the main cylinder 3,
A cam ring 5 is slidably supported by the main cylinder 3.

The zoom ring 8 has a connecting projection 9 at its inner wall end, as shown in more detail in FIGS. 4a and 4b.
is provided. As shown in FIG. 1, this connecting protrusion 9 is fitted without play into a notch groove 10 provided in the cam ring 5 through a rotation regulating groove 7 whose width is regulated by a presser plate 12 of the main cylinder 3. It is. Thereby, the cam ring 5 and the zoom ring 8 are connected, and when the zoom ring 8 is rotated, the cam ring 5 is rotated together with the rotation of the zoom ring 8.

A guide rod 13 is attached parallel to the optical axis between the holding plates 12 and 12', and a holding frame 14 holding a variable power lens group and a holding frame 14 holding a correction lens group are attached to the guide rod 13. 15 are slidably provided, and furthermore, the protrusion 16 of the holding frame 14 and the protrusion 17 of the holding frame 15 fit into the cam grooves 18, 18' (FIG. 3) of the cam ring 5, respectively, without play. are doing. Therefore, when the zoom ring 8 is rotated, the cam ring 5 is also rotated, so that the protrusions 16 and 17 move along the substantially spiral cam grooves 18 and 18', respectively. (Therefore,
The variable power lens group and the correction lens group are respectively displaced in the optical axis direction.

Here, the possible rotation angle of the zoom ring 8 is determined by the rotation regulating groove 7. That is, the connecting protrusion 9
The zoom ring 8 can only rotate within the range from one end of the rotation regulating groove 7 until it hits the other end.

In this configuration, the main cylinder 3 is molded from plastic material. As shown in FIG. 3, the cam ring 5 is provided with substantially spiral cam grooves 18, 18' on its side wall extending approximately half its circumference. It is difficult to form these cam grooves 18, 18' with high precision. Therefore, the cam ring 5 is made of metal such as aluminum.

As mentioned above, when the main cylinder is made of plastic, a particular problem is the cam ring thrust play (the cam ring's play in the optical axis direction) due to variations in the dimensions of the main cylinder and changes in size due to temperature changes. The cam ring thrust play is 0.015~
It is necessary to keep it to 0.025mm.

On the other hand, dimensional variations in plastic molded products are
The shorter the dimensions of the molded product, the less. For example, it is easier to increase the precision of a 3 mm part than a 30 mm part, and the dimensional accuracy of a 3 mm part can be approximately 0.01 mm at 3σ, including molding variations.

Further, the shorter the dimension, the smaller the dimensional change due to temperature change.

In the above embodiment, the cam ring backlash regulating groove 4 is provided in the main cylinder 3.
The main cylinder 3 holds the cam ring 5 by fitting the flange 6 of the cam ring 5 into this. The dimensions of the flange 6 are approximately 3 mm, so that even if the cam ring backlash regulating groove 4 has dimensional variations or changes due to temperature changes, the cam ring thrust play is within the above range of 0.015 to 0.025 mm. .

Here, the cam ring 5 is made of aluminum, and the main cylinder 3 is made of, for example, polycarbonate resin (30% glass fiber).
In the case where the cam ring 5 and the main cylinder 3 are made from a material having a temperature range of -10 DEG C. to 50 DEG C., the amount of dimensional change due to temperature change between the cam ring 5 and the main cylinder 3 is determined from the difference in linear expansion coefficient of the respective materials. In this case, if the temperature in normal use is 20℃, there will be a temperature change of 30℃, but as mentioned above,
If the dimension of the cam ring holding part of the main cylinder 3 is 3 mm, then 30
The dimensional change of the cam ring holding part due to temperature change in °C is
It is about 0.003mm, and the influence of temperature can be ignored.

From the above, even if the main cylinder 3 is made of plastic, the cam ring thrust play can be sufficiently suppressed to an acceptable level in terms of performance.

In the above embodiment, the flange 6 is provided at the end of the cam ring 5 on the imaging lens side, but this is adjustable on the focusing lens side, and the cam groove 18 , 18' are set.

Further, the roundness of the cam ring holding portion of the main cylinder 3 in the above embodiment is very good. As shown in Fig. 5, when plastic molding a main cylinder with the same structure as before, molten resin is poured into the mold through gate 2, but in order to improve the dimensional accuracy of the main cylinder, a large number of gates are used at the same time. Must be placed at intervals. However, since it is necessary to provide the rotation regulating groove 1 in the upper circumferential direction of the side wall of the main cylinder, a member for forming this rotation regulating groove 1 is provided in the mold, and for this purpose, the gate The molten resin injected into the mold from 2 is blocked by this member, and its flow becomes turbulent as shown by arrow B. As a result,
The roundness of this portion of the inner surface of the main cylinder where the cam ring touches becomes poor, making it impossible to achieve smooth rotation of the cam ring.

On the other hand, in the main cylinder 3 of the above embodiment,
Since the rotation regulating groove 7 is provided at the end of the main cylinder 3, by providing a gate on the side of the rotation regulating groove 7 in the mold for the main cylinder 3, there is no obstacle to the flow of the injected molten resin. The flow of molten resin is
There is almost no disturbance and the flow is uniform in the direction of arrow A (FIG. 2). As a result, the roundness of the main cylinder 3 becomes very good throughout. In this way, the main cylinder 3 has a simple structure that allows for easy roundness.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to sufficiently suppress the cam ring thrust play that occurs due to the molding accuracy of the main cylinder and dimensional changes due to temperature changes, and the main cylinder can be made of plastic. This makes it possible to provide a zoom lens barrel that is lighter and less expensive than the above-mentioned conventional technology without any deterioration in performance.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a main part of an embodiment of a zoom lens barrel according to the present invention, FIG. 2 is a vertical cross-sectional view showing a main part of the main barrel of FIG. 1, and FIG. 4 shows the zoom ring of FIG. 1, FIG. 4a is a vertical sectional view of the main part of the zoom ring, and FIG. FIG. 5 is a perspective view showing an example of a conventional main cylinder. 3...Main cylinder, 4...Cam ring play regulation groove, 5...
Cam ring, 6...flange, 7...rotation regulating groove, 8
...Zoom ring, 9...Protrusion, 10...Notch groove.

Claims (1)

[Claims] 1 A cam ring is rotatably provided on the inside of the main cylinder, and a zoom ring is rotatably provided on the outside of the main cylinder. In the zoom lens barrel integrally connected to the zoom ring, a sufficiently narrow cam ring play regulating groove is provided on the inner surface of the main barrel, and a sufficiently narrow flange is provided on the outer surface of the cam ring, and the flange is fitted into the cam ring play regulating groove to rotatably support the cam ring with the main cylinder, the rotation regulating groove is provided at an end of the main cylinder, and the connecting member is formed on the inner surface of the zoom ring. The zoom ring is a protruding member, wherein the tip of the connecting member is fitted into a notched groove provided at an end of the cam ring to integrally connect the zoom ring and the cam ring. lens barrel.