JP2001079737A - Grinding wheel and double-faced grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the cracking or chipping of a work during the grinding work by providing a partially annular outer press section having an outer peripheral circle around the rotation center axis on the outside of an annular grinding section provided eccentrically to the rotation center axis, and setting the end faces of the grinding section and the outer press section nearly flush with each other. SOLUTION: A cutting grinding wheel B used for a double-faced grinding device is provided with an outer press section 8 having an outer peripheral circle around the rotation center axis (s) on the outside of a grinding section 7 provided eccentrically to the rotation center axis (s). A void is formed between the outer peripheral face of the grinding section 7 and the inner peripheral face of the press section 8 on one side in the radial direction of the grinding wheel B, the inner peripheral face of the press section 8 is closely stuck to the outer peripheral face of the grinding section 7 on the opposite side, and the width in the radial direction of the press section 8 is formed gradually smaller toward the center on the eccentric side of the grinding section 7. The outer peripheral face of the grinding section 7 and the inner peripheral face of the press section 8 are connected by a proper means, and both end faces of the grinding section 7 and the press section 8 are made nearly flush with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding wheel and a double-side grinding apparatus suitable for simultaneously grinding both surfaces of a thin disk-shaped work such as a semiconductor wafer.

[0002]

2. Description of the Related Art Currently used semiconductor wafers have an outer diameter of about 200 mm (8 inches) and a diameter of about 300 mm (1 inch).
2 inches), but all have a thickness (finished dimensions) of about 0.8 mm, which is extremely thin compared to the outer diameter. And it was difficult to simultaneously grind both surfaces of such a thin disk-shaped work.

The present applicant has disclosed a device for simultaneously grinding both surfaces of a thin disk-shaped work, a pair of grinding wheel shafts arranged on the same axis so as to be relatively movable in the axial direction, and a circle of an end surface. A pair of annular grinding wheels fixed concentrically to the opposite ends of these grinding wheel shafts so that the annular grinding surfaces face each other, and the processing surfaces on both surfaces of the workpiece are respectively on the grinding surfaces of a pair of grinding wheels. Work rotation means for supporting and rotating the work at the grinding position between the grinding surfaces so that the outer periphery of the work intersects with the outer periphery of the grinding surface and the center of the work is always located within the grinding surface. (See JP-A-10-128646).

In this apparatus, double-sided grinding of a thin disk-shaped work is performed as follows. In other words, by rotating the pair of grindstones and moving them in a direction approaching each other in a state where the work is rotated at the grinding position,
Each grinding surface is brought into contact with the corresponding processing surface and cut to a predetermined position, cutting of each grindstone is stopped, and after performing spark-out grinding for a predetermined time, a pair of grindstones are moved in a direction away from each other. Then, separate each grinding surface from the processing surface.

[0005] According to this apparatus, the work rotates while the outer periphery of the work intersects the outer periphery of the grinding surface and the center of the work is always located within the grinding surface. Since the entire surface of the processed surface passes between the ground surfaces and comes into contact with the ground surface, the entire surfaces of the processed surfaces on both surfaces of the work can be simultaneously ground.

However, during grinding, since the center of the work is always located within the grinding surface, portions other than the vicinity of the center of the work are in contact with the grinding surface only for a part of the time during one rotation of the work. The vicinity of the center is always in contact with the ground surface.
For this reason, the amount of grinding near the center is larger than that of other parts, and the thickness of the work after grinding is thicker on the outer peripheral side, thinner near the center, and there is a problem that the thickness of the work greatly varies.

If each grindstone is mounted to be eccentric with respect to the center axis of rotation with respect to the radial width of the grinding surface, and the positional relationship between the grindstone and the work in the radial direction is set appropriately, the vicinity of the center of the work can be improved. Also, the workpiece can be brought into contact with the ground surface only for a part of the time during one rotation. By doing so, the above problem can be solved, but the following new problem arises.

That is, since the pair of grinding wheels are eccentrically mounted on the pair of grinding wheel shafts and driven to rotate independently of each other, even when both grinding wheels are rotated in the same direction and at the same speed, both grinding wheels are rotated. It is impossible to match the phase (rotational phase) in the rotation direction (circumferential direction) of the grindstones, and at a location of the work corresponding to the outer peripheral parts of both grindstones, the radial direction of the outer peripheral edge of the grinding surface of both grindstones A difference occurs in the position, and a state occurs in which the outer peripheral edge of the grinding surface of one of the grinding wheels is located radially outside the outer peripheral edge of the grinding surface of the other grinding wheel. When the two grindstones are rotated in the same direction at different speeds, or when both grindstones are rotated in opposite directions, the above-described state always occurs. During the grinding operation, both whetstones are pressed in the axial direction against the work surface of the work, so when the above-mentioned condition occurs, the outer peripheral edge of the grinding surface of one whetstone is more radially oriented than the other grinding surface. Is pressed in the axial direction, and a bending force acts on the work. For this reason, concentrated stress is generated particularly in the portion of the work that comes into contact with the outer peripheral edge of the grinding surface of the other grindstone that is located inside in the radial direction, and this causes the work to crack or chip.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, to reduce the variation in the thickness of a workpiece after grinding, and to prevent the workpiece from cracking or chipping during grinding. And a double-side processing apparatus.

[0010]

According to the first aspect of the present invention, there is provided a grinding wheel having an outer periphery centered on the rotation center axis outside an annular grinding portion provided eccentrically with respect to the rotation center axis. A partially annular or annular outer pressing portion which is a circle to be provided is provided, and end faces of the grinding portion and the outer pressing portion are substantially flush.

A partial annular or annular outer pressing portion whose outer periphery is a circle centered on the rotation center axis is provided outside the annular grinding portion provided eccentrically with respect to the rotation center axis. Accordingly, the outer peripheral shape of the entire grinding wheel including the grinding portion and the outer pressing portion becomes a substantially perfect circle centered on the rotation center axis.

A grinding wheel according to a second aspect of the present invention is the grinding wheel according to the first aspect, wherein a partial annular or annular inner holding member whose inner periphery is a circle centered on the rotation center axis is also provided inside the grinding portion. And an end face of the grinding portion and the inner pressing portion are substantially flush with each other.

Inside the annular grinding portion provided eccentrically with respect to the rotation center axis, a partial annular or annular inner pressing portion whose inner periphery is a circle centered on the rotation center axis is provided. Thus, the inner peripheral shape of the entire grinding wheel including the grinding portion and the inner pressing portion becomes a substantially perfect circle centered on the rotation center axis. Therefore, both the outer peripheral shape and the inner peripheral shape of the entire grinding wheel are substantially perfect circles centered on the rotation center axis.

Preferably, the amount of eccentricity of the grinding portion with respect to the rotation center axis is larger than the radial width of the grinding portion.

[0015] The grinding section is made of a suitable grinding stone material. The holding portion is made of a suitable grinding wheel material or another suitable material that satisfies the following conditions. First, the grinding of the work is mainly performed by the grinding unit, and the work is pressed in the axial direction by the grinding unit and the pressing unit.
Therefore, the pressing portion may have a grinding action, but in that case, it is necessary that the sharpness is lower than that of the grinding portion. Further, the grinding portion itself wears by grinding the work, but the pressing portion also needs to be worn by the work being pressed by the same manner as the grinding portion. By doing so, the end faces of the grinding portion and the holding portion are kept substantially flush.

According to a third aspect of the present invention, a pair of grinding wheels are disposed on the same axis so that a pair of grinding wheel shafts can relatively move in the axial direction. At the opposite end of the grinding wheel shaft, the rotation center axis is fixed in an opposed manner so as to coincide with the axis of the grinding wheel shaft, and supports a thin disk-shaped work at a predetermined grinding position between the grinding wheels. And a work rotation device for rotating the work.

Usually, the same pair of grinding wheels are used, and the end faces of the grinding portion and the pressing portion of each grinding wheel face each other in a parallel state. The work rotation means supports the work at the grinding position and rotates the work such that the processing surfaces on both sides of the work face the end faces of the respective grinding wheels.

The grinding position of the work is determined as follows. First, when viewed from the axial direction, the center of the work is defined as a circle inscribed on the inner periphery of the grinding unit around the rotation center axis of the grindstone and a circle circumscribing the outer periphery of the grinding unit around the rotation center axis of the grindstone. Be located between them. In this way, when the amount of eccentricity of the grinding unit with respect to the rotation center axis is larger than the radial width of the grinding unit, a part of the time that each grindstone makes one rotation always causes the center of the work to be within the grinding unit. (Between the inner circumference and the outer circumference of the grinding part when viewed from the axial direction), and the remaining part is such that the center of the work is located outside the grinding part.
If the amount of eccentricity of the grinding unit with respect to the rotation center axis is not larger than the radial width of the grinding unit, part of the time during which each grinding wheel makes one rotation is such that the center of the work is located in the grinding unit and the remaining Partly, the center of the work is located outside the grinding part,
Determine the grinding position.

In this double-sided grinding apparatus, for example, double-sided grinding of a thin disk-shaped work is performed as follows. That is, by rotating the pair of grinding wheels and moving them in a direction approaching each other in a state where the work is rotated at the grinding processing position, the end surfaces of the respective grinding wheels are brought into contact with the corresponding processing surfaces to reach a predetermined position. After the cutting and the cutting of each grindstone are stopped and spark-out grinding is performed for a predetermined time, a pair of grindstones are moved in a direction away from each other to separate each grindstone from the processing surface.

The cutting surface is ground mainly by the grinding portion of the grinding wheel by bringing the end face of the rotating grinding stone into contact with the processing surface of the work, and the work rotates on the grinding position as described above. Thus, while the work makes one rotation, the entire surface of the work surface of the work passes between the grinding portions and comes into contact with the grinding portion. For this reason, it is possible to simultaneously grind the entire surface of both surfaces by simply rotating the work in place using a grindstone whose outer diameter of the grinding portion is slightly larger than the radius of the work. It is only necessary to rotate the work on the spot, and it is not necessary to move it using a carrier as in the past.Thus, even a thin disk-shaped work can be easily and reliably ground, and the size of the device is small. Is possible. Also, the entire processing surface of the work can be ground using a grindstone having a slightly larger outer diameter of the grinding portion than the radius of the work, and there is no need to use a large grindstone having an outer diameter larger than the outer diameter of the work. From this point of view, the size of the apparatus can be reduced.

In the grinding wheel, since the grinding portion is eccentric with respect to the rotation center axis, the center of the work supported at the grinding position is viewed from the axial direction, and the grinding portion is centered on the rotation center axis of the grinding wheel. Between the circle inscribed on the inner circumference of the grinding wheel and the circle circumscribed on the outer circumference of the grinding part with the rotation center axis of the grinding wheel as the center, a part of the time that each grinding wheel makes one rotation is the center of the work Can be located inside the grinding section, and the remaining part can be such that the center of the work is located outside the grinding section. By doing so, the portion near the center of the work comes into contact with the grinding portion for a part of the time during one rotation of the grindstone, but the remaining portion comes off the grinding portion. Therefore, unlike the conventional case, the vicinity of the center of the work does not always contact the grinding portion, and the difference between the thickness of the vicinity of the center of the work after grinding and the thickness of other parts is smaller than in the conventional case. Therefore, the variation in the thickness of the entire work is reduced.

In each grinding wheel, a pressing portion is provided outside the grinding portion, and the outer peripheral shape of the entire grinding wheel is substantially a perfect circle centered on the rotation center axis. Therefore, regardless of the rotational phase of both grinding wheels. The outer peripheral shapes of both grinding wheels viewed from the axial direction substantially match. Therefore, at any point in the circumferential direction of the grindstones, the radial positions of the outer peripheral edges of the two grindstones substantially match, such that the outer peripheral edge of one grindstone is located radially outside the outer peripheral edge of the other grindstone. Nothing. For this reason, during the grinding operation, the portion of the work corresponding to the outer peripheral portion of the grindstone is not pushed by only one of the grindstones, so that the bending force does not act on the work, and the work does not crack or chip. .

When each grinding wheel is provided with an inner pressing portion also inside the grinding portion, both the outer peripheral shape and the inner peripheral shape of the entire grinding wheel are substantially perfect circles centered on the rotation center axis. Therefore, regardless of the rotation phase of both grinding wheels,
The outer peripheral shape and the inner peripheral shape of both whetstones viewed from the axial direction substantially match. Therefore, in both the part of the work corresponding to the outer peripheral part of the grindstone and the part of the work corresponding to the inner peripheral part of the grindstone, the bending force is not applied to the work by being pushed by only one grindstone, The work does not crack or chip. In addition, the grinding is performed in a state where the work is sandwiched between the grindstones from both sides at the outer peripheral portion and the inner peripheral portion of the grindstone, so that more stable grinding can be performed.

As described above, according to the grinding wheel of the first aspect, it is possible to simultaneously and easily grind both surfaces of a thin disk-shaped work with a small apparatus, and furthermore, to reduce the thickness of the work after grinding. Of the work can be reduced, and cracking or chipping of the work during the grinding operation can be prevented.

According to the grinding wheel of the second aspect, both sides of the thin disk-shaped work can be simultaneously and easily ground with a small apparatus, and the fluctuation of the thickness of the work after the grinding is reduced. At the same time, the work can be prevented from cracking or chipping during the grinding operation, and more stable grinding can be performed.

According to the double-sided grinding apparatus of the third aspect, it is possible to simultaneously and easily grind both sides of the thin disk-shaped work, and to reduce the variation in the thickness of the work after the grinding, and to reduce the work during the grinding operation. The work can be prevented from cracking or chipping, and the device can be downsized.

[0027]

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

FIG. 1 shows a main part of a double-side grinding apparatus for a thin disk-shaped work. The double-sided grinding device is obtained by adding a work rotation device (1) as a work rotation device to a horizontal-axis double-ended surface grinding machine. FIG. 1 shows a pair of grinding wheels (A) (A) ( Only part B) is shown. 2 and 3 are enlarged views of a thin disk-shaped work (wafer) (W) and grindstones (A) and (B) supported by the rotation device (1). In the following description, the front side of the sheet of FIG. 2 is the front, the back side is the rear, and the left and right of FIG.

The work (W) to be used in this embodiment has no positioning flat portion, and has a perfect circular outer diameter. Work (W)
Is rotated about its center (c) by the rotation device (1) in a posture in which both processing surfaces (a) and (b) face left and right.
At this time, the processing surface (a) facing left is referred to as a left processing surface, and the processing surface (b) facing right is referred to as a right processing surface.

Although not shown, the grinding machine has a bed and left and right grinding stone heads fixed to the upper surface of the bed.
Grinding wheel shaft (2) extending horizontally in each wheel head
Are rotatably supported. The positions of the left and right grinding wheel heads are adjusted so that the axes of the left and right grinding wheel shafts (2) coincide with one common horizontal axis extending in the left and right direction.
Indicates the axial direction (left-right direction) for each grinding wheel head
It is moved to. The base (3) is fixed concentrically to the tip of the left grinding wheel shaft (2) projecting to the right from the left grinding wheel head and the tip of the right grinding wheel shaft (2) projecting to the left from the right grinding head, On the opposite end faces of these bases (3),
The grindstones (A) and (B) are fixed respectively.

As shown in detail in FIG. 2, the base (3) has a thick cylindrical shape, and the end of the center hole (4) of the base (3) has a grinding wheel shaft (2).
Short cylindrical part (2a) for positioning, formed concentrically on the end face of
And the end face of the base (3) is
Is adhered to the end face of. A plurality of bolt holes (5) are formed around the center hole (4) of the base (3), and the base (3) is fixed to the grinding wheel shaft (2) by bolts (not shown) passed through these holes. Have been.

The right side grindstone (B) is provided outside the annular grinding portion (7) provided eccentrically with respect to the rotation center axis (s), and has an outer periphery centered on the rotation center axis (s). And a partially annular outer pressing portion (8). The grinding unit (7)
Centering on the center axis (g) of the grinding part, for example, the inner diameter is 97m
m, having an outer diameter of 103 mm and a complete annular shape having a radial width of 3 mm. The holding portion (8) has, for example, an inner diameter of 10
A 4 mm, outer diameter of 110 mm, and a radial width of 3 mm are superimposed on the grinding part (7) such that the outer circle is in contact with the outer circle of the grinding part (7), and the grinding part ( Partial toroidal shape with the part that interferes with 7) removed. By doing so, the eccentricity of the rotation center axis (s) and the grinding section center axis (g) becomes 3.5.
mm. Also, one side of the grinding wheel (B) in the radial direction (pressing part
On the opposite side of the eccentric direction of the grinding portion (7) with respect to (8)), a crescent-shaped space is formed between the outer peripheral surface of the grinding portion (7) and the inner peripheral surface of the holding portion (8). On the side (the eccentric direction side of the grinding part (7) with respect to the holding part (8)), the inner peripheral surface of the part removed as described above of the holding part (8) is in close contact with the outer peripheral surface of the grinding part (7). The radial width of the pressing portion (8) gradually decreases toward the center on the eccentric side of the grinding portion (7). Grinding part (7)
In the center of the eccentric side of the, the radial width of the pressing part (8) becomes almost 0, and in this part, the pressing part (8) may be continuous or discontinuous, Also in this case, the outer peripheral shape of the entire grindstone (B) including the grinding portion (7) and the pressing portion (8) is a substantially perfect circle centered on the rotation center axis (s). The outer peripheral surface of the grinding portion (7) and the inner peripheral surface of the pressing portion (8) that are in close contact with each other are joined by appropriate means such as adhesion. Both end surfaces of the grinding portion (7) and the holding portion (8) are substantially flush with each other. Adhesive or the like is attached to the left end face of the base (3) so that the right end faces of the grinding section (7) and the holding section (8) coincide with the rotation center axis (s) and the axis of the base (3). It is fixed by appropriate means. The left end surface of the grinding portion (7) is a grinding surface (7a), and the left end surface of the pressing portion (8) is a pressing surface (8a).

The portion where the left base (3) and the grindstone (A) are combined and the portion where the right base (3) and the grindstone (B) are combined are the same. That is, the left-side grinding wheel (A) has the same shape and the same dimensions as the right-side grinding wheel (B), so that the right-sided grinding wheel (B) and the left-right direction are opposite, and the rotation center axis (s) is Left base (3)
Is fixed to the right end face of the left base (3) so as to coincide with the axis of the base. The grinding surface (7a) and the pressing surface (8a) of the left and right grinding wheels (A) and (B) face each other in a state of being parallel to each other.

In the above grindstones (A) and (B), the grinding of the work (W) is mainly performed by the grinding section (7), and the holding section (8) is formed by the grinding section (7) and the work (W). Plays the role of holding in the direction. The grinding unit (7) is made of a suitable grinding stone material such as a diamond grinding stone. The pressing portion (8) may be made of a grindstone material having a grinding action, but in that case, the sharpness becomes worse as compared with the grinding portion (7). For example, when the grinding part (7) and the holding part (8) are formed of diamond grinding stones, the degree of bonding of the diamond grinding stone of the holding part (8) is softer than that of the diamond grinding stone of the grinding part (7), and the diamond abrasive Lower the degree of concentration. Further, the holding portion (8) can be made of a material having no grinding action, such as plastics. The grinding unit (7)
The work (W) is worn by grinding, but the holding part (8) is also pressed by the work (W).
It is made of a material that wears as in (7). By doing so, the grinding surface (7a) and the pressing surface (8a) are kept substantially flush.

As the left and right grinding wheel shafts (2) move in the axial direction, the left and right grinding wheels (A) and (B) relatively move in the axial direction. The left and right grinding wheel shafts (2) are rotated at the same speed in the same direction by driving means (not shown).
(A) and (B) are rotated in the same direction at the same speed. Note that the rotation directions and rotation speeds of the left and right grinding wheels (A) and (B) may be different from each other.

The other parts of the grinding machine can be configured in the same manner as a known horizontal-axis double-ended surface grinding machine.

The rotation device (1) is provided with a grinding position between the left and right grinding wheels (A) and (B) such that the axis of the workpiece (W) is parallel to the axis of the grinding wheels (A) and (B). It is supported vertically and rotates on its own, and is provided with three outer guide rollers (10), a driving roller (11), and three pressing rollers (12). Although not shown in detail, the rollers (10), (11), and (12) are all attached to the bed via appropriate support members. Roller (10) (11) (12)
The required one of them is switched between an operating position when supporting the work (W) and rotating, and a standby position when loading and unloading the work (W) to and from the rotating device (1). FIG. 1 shows a state in which all such rollers (10) (11) (12) are in the operating position.

FIG. 3 shows the positional relationship between the grindstones (A) and (B) and the work (W) supported at the grinding position by the rotation device (1) as viewed from the left. In the case of this embodiment, the whetstone (A)
The outer diameter of (B) is about 80% of the outer diameter of the work (W), and the center (c) of the work (W) supported at the grinding position is the rotation center axis of the grindstone (A) (B). s) It is located above. Then, when the work (W) is supported at the grinding position, the work (W)
The lower part, including the center (c), enters between the whetstones (A) and (B),
The remaining upper part protrudes out from between the grinding wheels (A) and (B), and the processing surfaces (a) and (b) on both surfaces of the work (W) are ground surfaces of the left and right grinding wheels (A) and (B). 7a) and the pressing surface (8a), respectively, the outer periphery of the work (W) intersects the outer periphery of the grinding surface (7a), and the center (c) of the work (W) is viewed from the axial direction. Grinding wheel
(A) A circle (d) inscribed on the inner circumference of the grinding section (7) about the rotation center axis (s) of (B) and a grinding section about the rotation center axis (s).
Circle (e) circumscribing the outer periphery of (7) (in this case, the holding part (8)
With the outer circle of. ) And located between.

The guide roller (10) contacts the outer peripheral surface of the portion of the work (W) protruding from between the grindstones (A) and (B) to regulate the radial position of the work (W). And work (W)
Are divided into three equal parts in the circumferential direction, that is, at one upper position in the center in the front-rear direction of the work (W) and at two lower positions in the front and back of the work (W). The drive roller (11) and the press roller (12) form a pair. The drive roller (3) and the press roller are used to move the work (W) out of the area between the grinding wheels (3) and (4). (12) The position of the workpiece in the axial direction (left-right direction) is restricted by being sandwiched from the left and right. The pressing roller (12) is pressed against the right processing surface (b) of the work (W) by a spring (not shown) to press the left processing surface (a) of the work (W) against the drive roller (11). The drive roller (11) is rotationally driven by an electric motor (not shown), and rotates the work (W) by rotating while being pressed against the processing surface (a) of the work (W). The pressing roller (12) comes into pressure contact with the processing surface (b) of the work (W) and rotates freely.
The drive roller (11) and the holding roller (12)
Of the work (W) in three places out of four positions in the circumferential direction, that is, one place in the upper part of the center of the work (W) in the front-rear direction and two places in the center of the work (W) in the vertical direction. I have.

In the above double-side grinding apparatus, the work (W)
Is performed, for example, as follows.

During the grinding operation, the left and right grinding wheels (A) and (B) rotate in the same direction and at the same speed as indicated by arrows in FIG.

With the grindstones (A) and (B) stopped at standby positions separated to the left and right, the required rollers (10) (11) (12) of the rotation device (1)
Is moved to the standby position, the work (W) is carried into the rotation device (1) by the work transfer device (not shown), and the above-described necessary rollers (10), (11), (12) are moved to the operation position. hand,
The work (W) is supported at the grinding position.

When the work (W) is supported at the grinding position, the drive roller (11) starts rotating. Drive roller (11)
Is rotated, the work (W) is moved by the rollers (10) and (11).
With the position in the radial and axial directions regulated by (12), the speed is lower than that of the grindstones (A) and (B) in the direction determined by the rotation direction of the drive roller (11), as indicated by the arrow in FIG. Then, it is rotated around its center (c).

At the same time, the grindstones (A) and (B) are moved in a cutting direction approaching each other at a relatively high rapid traverse speed. When the grindstones (A) and (B) approach the work (W) to some extent, the grindstones (A) and (B) are further moved in the cutting direction at a coarse grinding feed speed lower than the rapid feed speed. Thus, the grinding surface (7a) and the pressing surface (8a) come into contact with the corresponding processing surfaces (a) and (b), and the grinding wheels (A) and (B) are cut in the axial direction. Whetstone (A) (B)
Is cut into a predetermined position, and is further moved in the cutting direction at a lower dense grinding feed speed. Whetstone
When (A) and (B) are cut to a predetermined position, the cutting of the grindstones (A) and (B) is stopped, and spark-out grinding for a predetermined time is performed. And, when the spark-out grinding is finished,
The grindstones (A) and (B) are moved to the left and right standby positions, and the grinding surface (7a) and the pressing surface (8a) are separated from the processing surfaces (a) and (b).

When the grindstones (A) and (B) are separated from the work (W), the work (W), which has been ground by the work transfer device, with the grindstones (A) and (B) stopped at the standby position. Is a rotation device (1)
It is carried out from. Then, as described above, the next work
(W) is carried into the rotation device (1), and a grinding operation is performed.

The grinding surface (7a) and the pressing surface (8a) of the grindstones (A) and (B) rotating as described above are used as the processing surface (a) of the work (W).
By making a cut by contacting (b), the machined surfaces (a) and (b) are mainly ground by the ground surface (7a),
(W) rotates at the grinding position as described above, so that the entire surface of the work surface (a) (b) of the work (W) becomes the ground surface (7a) during one rotation of the work (W). Through the grinding surface (7
a), and as a result, while the work (W) rotates several times, the entire surfaces of the processing surfaces (a) and (b) on both surfaces are simultaneously ground. Since the outer periphery of the work (W) at the grinding operation position intersects with the outer periphery of the grinding surface (7a), parts other than near the center (c) of the processing surface (a) (b) of the work (W) W) makes contact with the grinding surface (7a) for a part of the time during one rotation. Further, the amount of eccentricity of each grinding wheel (A) (B) with respect to the rotation center axis (s) of the grinding portion (7) is larger than the radial width of the grinding portion (7), and the work (W) is as described above. As described below, since the spindle rotates at the grinding position, the vicinity of the center (c) of the processing surface (a) (b) of the workpiece (W) also
(A) The grinding surface (7a) comes into contact with the grinding surface (7a) only for a part of time during one rotation of (B). FIG. 3 shows the relative position of the work (W) with respect to some rotational positions of the grindstone (B) in a state where the work (W) is rotated around the grindstone (B). While the grindstone (B) makes one rotation, the relative positional relationship of the work (W) to the grindstone (B) changes as (W) → (W1) → (W2) → (W3) → (W) .
In the state of (W), the center (c) of the work deviates radially inward from the grinding surface (7a), and in the state of (W1), the center (c1) of the work is located in the grinding surface (7a), In the state of (W2), the center of the work (c
2) is displaced radially outward from the grinding surface (7a), and in the state of (W3), the center (c3) of the work is located within the grinding surface (7a). From this, it can be seen that the vicinity of the center (c) of the work (W) comes into contact with the grinding surface (7a) for a part of the time when the grindstone (B) makes one rotation. And since the grindstone (B) rotates at a higher speed than the work (W), the vicinity of the center (c) of the work (W) is on the ground surface (7a) only for a part of the time during which the work (W) makes one revolution. Contact. The same applies to the whetstone (A).

Thus, the vicinity of the center (c) of the work (W) is
Part of the time during which the grinding stones (A) and (B) make one revolution comes in contact with the grinding surface (7a), but the rest of the time comes off the grinding surface (7a).
The vicinity of the center (c) of the work (W) does not always contact the ground surface (7a). Further, in this embodiment, since the center (c) of the work (W) at the grinding position is located further inside than the smallest diameter portion of the inner periphery of the holding portion (8),
The vicinity of the center (c) of the work (W) does not come into contact with the pressing surface (8a). Suppose the center (c) of the workpiece (W) at the grinding position
Is positioned outside the smallest diameter part of the inner circumference of the holding part (8), the vicinity of the center (c) of the work (W) alternately contacts the holding surface (8a) and the grinding surface (7a). But the ground surface (7a)
Work (W) because the holding surface (8a) is less sharp than
The grinding amount in the vicinity of the center (c) does not increase. Therefore, in any case, the difference between the thickness in the vicinity of the center (c) of the work (W) after grinding and the thickness of the other parts is smaller than in the conventional case, and the thickness of the entire work (W) is reduced. Fluctuations are reduced.

In each of the grinding wheels (A) and (B), a holding portion (8) is provided outside the grinding portion (7), and the outer peripheral shape of the whole of the grinding wheels (A) and (B) corresponds to the rotation center axis (s). Since it is a substantially perfect circle at the center, the outer peripheral shapes of both grinding wheels (A) and (B) when viewed from the axial direction substantially match regardless of the rotational phase of both grinding wheels (A) and (B). Therefore, at any point in the circumferential direction of the grinding wheels (A) and (B),
(A) The radial position of the outer peripheral edge of (B) almost coincides, and the outer peripheral edge of one of the grindstones (A) and (B) is radially outward from the outer peripheral edge of the other grindstone (A) (B). There is no such thing as being located. For this reason, during the grinding operation, the portion of the work (W) corresponding to the outer peripheral portion of the grindstones (A) and (B) is pushed only by the grindstones (A) and (B) on one side, and the bending force is applied to the work (W). It does not act, and the work (W) does not crack or chip.

In each of the grinding wheels (A) and (B), the grinding portion (7) itself wears by grinding the work (W), but the holding portion (8) is also pressed by the work (W). As a result, it is worn as in the case of the grinding portion (7), whereby the grinding surface (7a) and the pressing surface (8a) are always kept substantially flush.

FIG. 4 shows another embodiment of the grinding wheel.

In this case, the holding portion (8) is shaped so as to fill a crescent-shaped space between the holding portion (8) and the grinding portion (7) in the above embodiment, and the entire inner peripheral surface of the holding portion (8) is formed. Grinding unit
It is tightly joined to the outer peripheral surface of (7). Others are the same as those of the above-mentioned embodiment, and the same portions are denoted by the same reference numerals.

FIG. 5 shows still another embodiment of the grinding wheel.

In this case, the pressing portion (8) forms a complete annular shape having a uniform radial width, and a part of the outer periphery of the grinding portion (7) is part of the inner periphery of the pressing portion (8). Inscribed. Others are the same as those of the first embodiment, and the same parts are denoted by the same reference numerals.

In the grinding wheel of FIG. 5, as in the case of FIG. 4, the pressing portion (8) may be shaped so as to fill the gap between the pressing portion (8) and the grinding portion (7).

The configuration of the outer holding portion (8) is not limited to the above-mentioned configuration, but may be another appropriate configuration.

FIG. 6 shows still another embodiment of the grinding wheel.

In this case, an outer pressing portion (8) as shown in FIG. 4 is provided outside the grinding portion (7). Similarly, inside the grinding portion (7), the inner circumference also corresponds to the rotation center axis (s). A partial annular inner pressing portion (9) that is a center circle is provided. Both end surfaces of the inner holding portion (9) are almost flush with both end surfaces of the grinding portion (7), respectively, and the inner holding portion on the same side as the grinding surface (7) is provided.
The end face of (9) is the pressing face (9a). Others are the same as those of the first embodiment, and the same parts are denoted by the same reference numerals.

When the grindstone shown in FIG. 6 is used in a double-sided grinder, each grindstone is provided with holding portions (8) and (9) on the outside and inside of the grinding portion (7), so that the outer peripheral shape and the inner shape of the whole grindstone are provided. Since both circumferential shapes are substantially perfect circles centered on the rotation center axis (s), the outer peripheral shapes of the two grindstones viewed from the axial direction substantially match regardless of the rotational phases of the two grindstones. Therefore, in both the part of the work corresponding to the outer peripheral part of the grindstone and the part of the work corresponding to the inner peripheral part of the grindstone, the bending force is not applied to the work by being pushed by only one grindstone, The work does not crack or chip. In addition, the grinding is performed in a state where the work is sandwiched between the grindstones from both sides at the outer peripheral portion and the inner peripheral portion of the grindstone, so that more stable grinding can be performed.

When both the outer pressing portion and the inner pressing portion are provided on the grindstone, the outer pressing portion may have any one of the structures shown in FIGS. 3 to 5 or another appropriate structure. The same applies to the inner holding portion.

The configuration of each part such as a grinding machine and a work rotating device which constitute the double-sided grinding device, the method of the grinding operation, and the like are not limited to those of the above-described embodiment, and can be appropriately changed.

The present invention is not limited to the horizontal double-sided grinding apparatus in which a pair of grinding wheels are horizontally opposed as in the above embodiment, but also the vertical type in which a pair of grinding wheels are vertically opposed. It can also be applied to double-sided grinding machines.

The present invention can also be applied to double-side grinding of a work having a flat portion for positioning formed at one place on the outer periphery. In that case, in the work rotating device, two outer peripheral guide rollers are provided at three places around the work, each having an interval slightly larger than the circumferential dimension of the positioning flat portion.

In the above embodiment, the cut is given by moving both grindstones (A) and (B) in the axial direction, but one of the grindstones (A) and (B) and the work (W) are axially moved. The cut may be given by moving.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a double-sided grinding apparatus showing an embodiment of the present invention.

FIG. 2 is a partially cutaway front view showing an enlarged portion of a grinding wheel.

FIG. 3 is an enlarged end view showing a grinding wheel part;

FIG. 4 is an end view showing another embodiment of the grinding wheel.

FIG. 5 is an end view showing still another embodiment of the grinding wheel.

FIG. 6 is an end view showing still another embodiment of the grinding wheel.

[Explanation of symbols]

 (A) (B) Grinding wheel (7) Grinding part (7a) Grinding surface (8) Outside holding part (8a) Holding surface (9) Inside holding part (9a) Holding surface (g) Grinding part center axis (s) Rotation center axis

Claims (3)

[Claims] 1. A partial annular or annular outer pressing portion whose outer periphery is a circle centered on the rotation center axis is provided outside the annular grinding section provided eccentrically with respect to the rotation center axis. A grinding wheel provided, wherein the end faces of the grinding portion and the outer pressing portion are substantially flush. 2. A partial annular or annular inner pressing portion whose inner periphery is a circle centered on the rotation center axis is also provided inside the grinding portion. The end face is substantially flush.
Grinding wheel. 3. A grinding wheel according to claim 1, wherein a pair of grinding wheel shafts are arranged on the same axis so as to be relatively movable in the axial direction. A work rotation device, which is fixed in an opposed manner so that the rotation center axis coincides with the axis of the grinding wheel shaft, and supports a thin disk-shaped work at a predetermined grinding position between the grinding wheels to rotate. A double-sided grinding device, which is provided.