EP1285726A2

EP1285726A2 - Centerless grinding method for barshape work centerless grinder

Info

Publication number: EP1285726A2
Application number: EP02254844A
Authority: EP
Inventors: Hirohisa c/o Koyo Machine Ind. Co Ltd Yamada; Haruyuki c/o Koyo Machine Ind. Co Ltd Hirayama
Original assignee: Koyo Machine Industries Co Ltd
Current assignee: JTEKT Machine Systems Corp
Priority date: 2001-07-17
Filing date: 2002-07-10
Publication date: 2003-02-26
Anticipated expiration: 2022-07-10
Also published as: JP3984804B2; EP1285726B1; DE60211078T2; KR20030007125A; DE60211078D1; KR100899136B1; EP1285726A3; JP2003025194A

Abstract

A high efficiency centerless grinding method capable of grinding the tip portion of bar-shape work, assuring high coaxiality and cylindricity even in case of work having extremely small diameter. The base portion (Wa) of work (W) is pressed and supported by pressure roller (4) against regulating wheel (2), forcibly rotating the work (W), and the work (W) is fed by pusher (5) in the axial direction in order to grind the tip portion (Wb) of work (W) by grinding wheel (1). In this way, even when the tip portion (Wb) of work (W) is extremely small in diameter, the lengthwise grinding of the work (W) may be accurately controlled, and the tip portion (Wb) of work (W) is ground in accordance with the diameter of the base portion (Wa) . As a result, it is possible to grind the work (W) into a stepped work (W) in a short time with little deflection in axial center of the work (W) while assuring high coaxiality and cylindricity.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a centerless grinding method for bar-shape work, and a centerless grinder, and more particularly, to centerless grinding techniques for grinding the tip portion of bar-shape work.

Description of the Related Art

As a method of machining the tip portion of bar-shape work (hereinafter called work) into a stepped shape, a centerless grinding method based on an infeed grinding system is preferably employed.
For example, various methods as shown in Fig. 9 to Fig. 11 have been developed and proposed as centerless grinding methods of the kind.
The grinding method shown in Fig. 9 is such that by using a grinding wheel (a) and regulating wheel (b), each having a profile corresponding to the final shape of work (W) to be subjected to grinding, the work (W) is rotated and supported by the regulating wheel (b) and a blade (not shown), while the entire periphery of work (W) is ground by the grinding wheel (a) into a stepped shape that includes a large-diameter base portion (Wa) and a small-diameter tip portion (Wb) (refer to Japanese Laid-open Patent No. 7-246548).
Also, the grinding method shown in Fig. 10, an improved version of the grinding method of Fig. 9, is such that the base portion (Wa) of work (W) is rotated and supported by regulating wheel (c) and blade (d), while backup shoe (e) making sliding contact with the tip portion (Wb) of work (W), regulating wheel (c), and blade (d) are moved to the grinding wheel (f) side, and in this way, the tip portion (Wb) of work (W) is ground by the grinding wheel (f) having a profile corresponding to the final shape of the tip portion (Wb) of work (W) (refer to Japanese Laid-open Patent No. 7-246548).
Further, the grinding method shown in Fig. 11 is such that the large-diameter base portion (Wa) of work (W) is rotated and supported by regulating wheel (g) and blade (h), and at the same time, the work (W) is pressed against the regulating wheel (g) by means of pressing roller (i), while the tip portion (Wb) of work (W) is ground by grinding wheel (j) having a profile corresponding to the final shape of small-diameter tip portion (Wb) of work (W) (refer to Japanese Laid-open Patent No. 60-177849).
However, since all of these conventional grinding methods are based on an infeed grinding system, there arise the following problems and it is difficult to obtain the desired coaxiality or the like.
That is, in the method of Fig. 9, both of base portion (Wa) and tip portion (Wb) of work (W) are simultaneously ground, therefore it is difficult to attain the accuracy of the small-diameter tip portion (Wb) and to obtain the coaxiality of the entire work (W), and in particular, when the diameter of the tip portion (Wb) is extremely small, there is a fear of causing damage to the small-diameter tip portion (Wb).
Also, in the grinding method of Fig. 10, when the tip portion (Wb) of work (W) is ground by the grinding wheel (f), the tip portion (Wb) of work (W) is supported by the backup shoe (e) making sliding contact therewith, while the tip portion (Wb) changes in diameter every second, and accordingly it is necessary to adjust the movement of the backup shoe (e), and the adjustment of the movement is not easy, making it difficult to obtain the desired coaxiality.
Further, in the grinding method of Fig. 11, the tip portion (Wb) of work (W) without being supported is ground by radial feed of the grinding wheel (j), therefore it is difficult to obtain the coaxiality because the tip portion (Wb) flexes, and for avoiding such flexing, it is also necessary to make the rate of radial feed of the grinding wheel (j) lower as compared with the above two grinding methods, resulting in longer cycle time and lower production efficiency.

BRIEF SUMMARY OF THE INENTION

The main object of the present invention is to provide a new centerless grinding method and centerless grinder which may solve the above conventional problems.
Another object of the present invention is to provide a centerless grinding method and centerless grinder which may assure the high coaxiality and cylindricity of the tip portion of bar-shape work and enable the grinding operation even when the work is extremely small in diameter or in diametric size and moreover make it possible to obtain high production efficiency.
Also, still another object of the present invention is to provide a center less grinding method and center less grinder which may accurately control the size in grinding lengthwise direction or axial direction of the work even when the tip portion of the work is extremely small in diameter.
Further another object of the present invention is to provide a centerless grinding method and centerless grinder which may grind the work into a stepped shape in a short time with little deflection in axial center of the work, assuring high coaxiality and cylindricity thereof, as a result of grinding the tip portion of the work in accordance with the outer diameter of the base portion of the work.
The centerless grinding method of the present invention is a method of centerless grinding of the tip portion of bar-shape work and is configured that the base portion of the work is pressed and supported by a pressing means against an regulating wheel, thereby forcibly rotating the work, while the work is fed by a feeding means in the axial direction relative to a grinding wheel so that the tip portion of the work is ground by the grinding wheel.
As preferred embodiments, the methods of feeding the work by the feeding means in the axial direction relative to the grinding wheel include: a method of axially feeding only the work by the feeding means; a method of axially feeding the work by the feeding means together with the pressing means and regulating wheel; and a method of feeding the grinding wheel by the feeding means in the direction opposite to the axial direction.
Further, the operation for radial feed of the grinding wheel is performed in accordance with the outer diameter of the base portion of the work and with the grinding wheel synchronized with the feeding operation of the work.
Also, the configuration of the centerless grinder of the present invention is suited for executing the centerless grinding method, and comprises a blade for supporting the base portion of the work; an regulating wheel rotationally driven to rotate and support the base portion of the work; a pressing means for pressing and supporting the work against the regulating wheel; a grinding wheel rotationally driven to grind the tip portion of the work forcibly rotated and supported by the regulating wheel; and a feeding means for feeding the work forcibly rotated and supported by the regulating wheel and blade in the axial direction relative to the grinding wheel.
As a preferred embodiment, the pressing means comprises a pressure roller capable of making rolling contact with the periphery of the base portion of the work, and a pressing means for pressing the pressure roller against the periphery of the base portion of the work by applying a predetermined pressure thereto. Also, the feeding means comprises a pusher capable of abutting the rear end of the work, and a moving means for moving the pusher in the axial direction of the work. The grinding wheel comprises a wheel surface having a profile corresponding to the final shape of the tip portion of the work.
Also, as the feeding means, preferably employed are a configuration of feeding only the work axially, a construction having a pusher capable of abutting the rear end of the work, and a moving means for moving the pusher in the axial direction of the work; a configuration of axially feeding the work together with the pressing means and regulating wheel, a construction having a mobile base to mount and support the pressing means and regulating wheel, and a moving means for moving the mobile base in the axial direction of the work; and a configuration of feeding the grinding wheel in the direction opposite to the axial direction, a construction having a mobile base to mount and support the grinding wheel, and a moving means for moving the mobile base in the axial direction of the work.
Further, it is constructed in that the grinding wheel is operated for radial feed relative to the work and is configured so that the operation for radial feed of the grinding wheel is synchronized with the work feeding operation by the feeding means.
In the present invention, the work is forcibly rotated with the base portion of the work pressed and supported by the pressing means against the regulating wheel, while the work is fed by the feeding means in the axial direction relative to the grinding wheel, and thereby, the tip portion of the work is ground by the grinding wheel. In this way, the size in grinding lengthwise direction or axial direction of the work can be accurately controlled even in case the tip portion of the work is extremely small in diameter, and it is possible to grind the tip portion of the work while assuring high coaxiality and cylindricity.
The above and other related objects and features of the present invention will be made clear by reading the detailed description based on the attached drawings and the new matters pointed out in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic plan view of a centerless grinder in embodiment 1 of the present invention, showing a state of grinding bar-shape work.
Fig. 2 shows the centerless grinder: Fig. 2 (a) is a sectional view along the A-A line of Fig. 1; and Fig. 2 (b) is a sectional view along the B-B line of Fig. 1.
Fig. 3 is an explanatory diagram of the process for grinding bar-shape work into a stepped shape by the centerless grinder.
Fig. 4 is a schematic plan view of a centerless grinder in embodiment 2 of the present invention, showing a state of grinding bar-shape work.
Fig. 5 is an explanatory diagram of the process for grinding bar-shape work into a stepped shape by the centerless grinder.
Fig. 6 is a schematic plan view showing a state of grinding bar-shape work into other different stepped shape by the centerless grinder.
Fig. 7 is a schematic plan view of a centerless grinder in embodiment 3 of the present invention, showing a state of grinding bar-shape work.
Fig. 8 is a schematic plan view of a centerless grinder in embodiment 4 of the present invention, showing a state of grinding bar-shape work.
Fig. 9 is a schematic plan view of a conventional centerless grinder for grinding bar-shape work into a stepped shape.
Fig. 10 is a schematic plan view of other conventional centerless grinder for grinding bar-shape work into a stepped shape.
Fig. 11 shows another conventional centerless grinder for grinding bar-shape work into a stepped shape: Fig. 11 (a) is a front view, and Fig. 11 (b) is a plan view.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The exemplary embodiments of the present invention will be described in the following with reference to the drawings.
In Fig. 1 to Fig. 8 are shown a centerless grinder related to the present invention, and the same reference numerals used in all the drawings base for same component members or elements.

Embodiment 1

A centerless grinder in one preferred embodiment of the present invention is shown in Fig. 1 to Fig. 13. The grinder performs centerless grinding of the periphery of bar-shape work W into a stepped shape having, for example, large-diameter base portion Wa and small-diameter tip portion Wb as shown in Fig. 1, and specifically, the grinder is configured to grind only the tip portion Wb, and comprises grinding wheel 1, regulating wheel 2, blade 3, pressure roller 4, and pusher 5 as essential components.
Grinding wheel 1 serves to grind the periphery of tip portion Wb of work W, and its wheel surface 1a has a profile corresponding to the final shape of the tip portion Wb of work W, that is, the final finish shape of the periphery of tip portion Wb, and also has a general basic structure that has been conventionally well-known. That is, the grinding wheel 1 is removably secured on grinding wheel spindle 6 shown in Fig. 2 (b), and the grinding wheel spindle 6 is in rotatable bearing engagement with a grinding wheel housing (not shown) fixedly disposed, and is also connected to a driving source such as a drive motor or the like via power transmission belt or gear mechanism.
Also, the wheel surface 1a of the grinding wheel 1 is formed of conductive grindstone having undergone discharge truing. As such conductive grindstones, metal bonded grindstones such as diamond and CBN are employed. The wheel surface 1a formed of such conductive grindstone is very high in grain retention, hard to be deformed, and sufficient in grain protrusion due to shape correction by discharge truing, thereby having excellent sharpness.
Regulating wheel 2 serves to rotate and support only the base portion Wa, namely large-diameter portion of work W which is not to be ground in grinding, and comprises rotational support surface 2a formed of a cylindrical surface and is disposed in a position shifted in the axial direction of work W as against the grinding wheel 1.
The regulating wheel 2 has a general basic structure that has been conventionally well known and is removably secured on regulating wheel spindle 7 shown in Fig. 2 (a), and the regulating wheel spindle 7 is rotatably supported on a regulating wheel housing (not shown), and is also connected to a driving source such as a drive motor or the like via power transmission belt or gear mechanism.
The axial center of the regulating wheel 2 is arranged and set in the feed direction of work W, in the anti-feed direction, that is, in the direction diagonally opposite to the feed direction, or in the direction parallel to the axial center of grinding wheel 1, and the selection of the direction is decided according to the purpose.
In the preferred embodiment shown, the axial center of regulating wheel 2 is arranged and set in the anti-feed direction, and structurally gives a thrust force to the work W in the anti-feed direction (in the direction opposite to feed direction X in Fig. 1 and Fig. 3) in cooperation with pressing means 14 described later.
Blade 3 supports the base portion Wa of work W together with regulating wheel 2 as shown in Fig. 2 (a), and is disposed on a regulating wheel housing same as the regulating wheel 2 and has an inclined support surface 3a which supports the base portion Wa of work W from underneath.
Pressure roller 4 is an essential portion of pressing means 14 which presses and supports the large-diameter portion Wa of work W, together with the pressing means 10, against the rotational support surface 2a of regulating wheel 2, and is rotatably supported by roller shaft 8.
The pressure roller 4 is disposed opposite to the regulating wheel 2 and capable of making rolling contact with the periphery of base portion Wa of work W, and is pressed by the pressing means 10 against the periphery of base portion Wa of work W with a predetermined pressure applied thereto. In the preferred embodiment shown, a resilient force applying means such as an elastic spring is employed as the pressing means 10, by which the pressure roller 4 is always resiliently pressed against the periphery of base portion Wa of work W.
And, the pressing means 14 including the pressure roller 4 serves to resiliently press and support the base portion Wa of work W against the regulating wheel 2, and cooperates with the regulating wheel 2 rotationally driven in order to forcibly rotate the work W, while giving a thrust force to the work W in the anti-feed direction.
Pusher 5 is an essential portion of feeding means 15 which forcibly feeds the work W in the axial direction, that is, in the feed direction X toward the grinding wheel 1 side.
The pusher 5 is not specifically shown, but it is disposed nearly coaxially with the work W supported by the regulating wheel 2 and blade 3 and is also supported so as to be able to rotate in the axial direction of the work W. Also, the pusher 5 is in drive connection to a moving means not shown. As a moving means to reciprocally move the pusher 5 in the axial direction, a linear motor or a conventionally well-known feed drive unit provided with a screw mechanism is properly employed.
And, by the feeding means, the end portion 5a of pusher 5 is abutted on the rear end of the base portion Wa of work W, thereby feeding the work W in the axial direction (feed direction) X only by a predetermined distance at a given speed.
In this case, in the present preferred embodiment where the regulating wheel 2 is diagonally arranged so as to give a thrust force to the work W in the anti-feed direction, the pusher 5 forcibly feeds the work W in the feed direction X at a given speed against the thrust force.
In case the regulating wheel 2 is diagonally arranged so as to give a thrust force to the work W in the feed direction, the feeding speed of pusher 5 will be set to be higher than the feeding rate caused due to the thrust force of the regulating wheel 2.
Accordingly, in a centerless grinder having a configuration as described above, the base portion Wa of work W is pressed and supported by the pressing means 14 against the regulating wheel 2, then the work W is forcibly rotated and the work W forcibly rotated is fed by the feeding means 15 in the axial direction (feed direction) X, and thereby, the tip portion Wb of work W is ground by the grinding wheel 1.
Specifically, the grinding wheel 1 being set and arranged in accordance with the finish size of the tip portion Wb of work W, the grinding wheel 1 and regulating wheel 2 are driven to rotate respectively at predetermined speeds, and as the pusher 5 of feeding means 15 moves forward in the feed direction X, bar-shape work W is fed to the position of the regulating wheel 2 along the inclined support surface 3a of blade 3 (see Fig. 2). Then, the pressure roller 4 of pressing means 14 presses the work W against the regulating wheel 2 with a predetermined resilient force, and as a result, the work W is forcibly rotated by the rotational force of the regulating wheel 2 [see Fig. 3 (a)]
Further, as the pusher 5 moves forward, the work W is fed in the axial direction X and then the tip portion thereof is fed to the grinding wheel 1. In this case, only the base portion Wa of work W is rotationally supported by the regulating wheel 2 and blade 3 due to the pressing force of the pressure roller 4, and the periphery of the tip portion Wb of work W is ground by the grinding wheel 1 to be formed in the shape of a small-diameter cylindrical portion and a tapered portion as shown in Fig. 3 (b).
The grinding mechanism in the above process is such that the tip of the work W first abuts the wheel surface 1a of grinding wheel 1 when grinding is started, and then the tip portion Wb of work W is ground into a predetermined shape and size as the work W is fed by the pusher 5. In other words, in grinding of the work W, the periphery of tip portion Wb is ground by the grinding wheel 1 in accordance with the outer diameter of the base portion Wa rotationally supported by the pressure roller 4 and regulating wheel 2. In this case, the tip portion Wb of work W fed while being ground is in a state of being free without being rotationally supported by the rotational support surface 2a of regulating wheel 2 as shown in Fig. 3 (b).
And, when the work W is axially fed to the specified position, grinding the tip portion Wb of work W into the predetermined final finish shape, then the grinding wheel 1 is completely separated from the work W, thereby completing the grinding operation [see Fig. 3 (d)].
Or, even after grinding the tip portion Wb of work W into the predetermined final finish shape, the grinding wheel 1 moves backward (minus cutting) in synchronism with the movement of the work W fed by the pusher 5, while the work W is axially fed to the specified position [see Fig. 3 (c)] and, after that, the grinding wheel 1 is completely separated from the work W, thereby completing the grinding operation [see Fig. 3 (d)].
In this way, the work W with its tip portion Wb ground is ejected by an ejecting means (not shown) outside from the machining position between grinding wheel 1 and regulating wheel 2.
As described above, employing a system such that, while feeding the work W by the pusher 5 in the axial direction X, only the base portion Wa of work W is forcibly rotationally supported in order to grind the periphery of the tip portion Wb of work W by the grinding wheel 1, it is possible to accurately control the size of the work W in the lengthwise or axial grinding size thereof, and moreover, since the tip portion Wb of work W is ground in accordance with the diameter of the base portion Wa of work W, it is possible to grind the work W into a stepped shape in a short time with little deflection in axial center of the work W while assuring high coaxiality and cylindricity.
Particularly, since the tip portion Wb of work W subjected to grinding is ground in a state of being completely free without being supported by the rotational support surface 2a of regulating wheel 2 and the inclined support surface 3a of blade 3, high coaxiality and cylindricity as described above may be precisely assured even in case the tip portion Wb is extremely small in diameter. As a result, it is possible to easily perform grinding of the work W having extremely thin tip portion Wb in a short cycle time that has been conventionally considered impossible to perform by using a centerless grinding method of this kind.
Also, in such structure that the tip portion Wb of work W is not supported at all by the rotational support surface 2a of regulating wheel 2 and the inclined support surface 3a of blade 3, the structure brings about an advantage such as it is not necessary to make the blade 3 extremely thin in the design, and also, it is possible to easily and readily carry out the rearrangements according to the type change of work W or the like.
Further, since the wheel surface 1a of grinding wheel 1 is configured by conductive grindstone having undergone discharge truing, the quantity of grain protrusion is sufficient and excellent sharpness may be ensured. As a result, it is possible to improve the grinding efficiency while maintaining the sharpness of the wheel surface 1a for a long period of time, and to effectively prevent the tip portion Wb of work W from being damaged even when the tip portion is extremely small in diameter.
Particularly, with reference to Fig. 1 for example, the boundary portion P between the two peripheries comprising the wheel surface 1a in the grinding wheel 1 is a portion which is especially liable to be damaged due to grinding operation, but since the wheel surface 1a of grinding wheel 1 is configured by conductive grindstone having undergone discharge truing, it may bring about such a great advantage as mentioned above that is unable to obtain by a conventional general wheel surface. That is, a conventional general wheel surface is configured by grindstone having undergone truing by rotary dresser, and in such configuration, the rotary dresser (truer) will soon wear out resulting in excessive abrasion.
Also, regarding the grinding techniques related to the present invention (grinding techniques related to the present preferred embodiment), the comparison between the grinding techniques and the conventional grinding techniques shown in Fig. 10 and Fig. 11 shows that, when grinding work W whose tip portion Wb is extremely small in diameter, a micro-drill for example, the time required for grinding by the grinding technique of the present invention is about 1/2 to 1/3 of the time required for grinding by the conventional grinding technique.
Although it is not shown, the timing for ending the grinding of the tip portion Wb of work W is preferable to be settled according to the result of detection executed, for example, by a sensor such as a proximity switch which detects the amount of feed of the work W by pusher 5, and also preferable is to be settled by forcibly stopping the feed of work W by a stop means such as a stopper, and as a specific mans, an appropriate means may be employed.
Also, as for how to eject the work W out of the machine, for example, it is preferable to eject the work W by moving the grinding wheel 1 or regulating wheel 2 off from the work W, or by disposing an external mechanism such as a loader arm and using an attracting means or the like to chuck and take out the work W in order to eject the work W, and as a specific method, an appropriate method may be employed according to the purpose or the like.
Further, as in the preferred embodiment shown, when the regulating wheel 2 is diagonally arranged so as to give a thrust force to the work W in the anti-feed direction (opposite to the feed direction X), the pusher 5 is moved backward from the end of large-diameter portion Wa of work W after completion of the grinding process, and thereby, the work W can be moved backward and ejected due to the thrust force given in the anti-feed direction by the regulating wheel 2.

Embodiment 2

The present preferred embodiment is shown in Fig. 4 and Fig. 5, and it is intended to grind work W having different shapes of tip portion Wb by means of a center less grinder of the Embodiment 1.
That is, in the centerless grinder in the embodiment 1, the structure is such that grinding wheel 1 is operated for radial feed relative to work W to be ground, and therefore, by controlling the grinding wheel 1 so as to be operated in synchronism with the feeding operation of work W by feedingmeans 15, it is possible to execute grinding of the tip portion Wb as shown.
The grinding process of work W by means of the centerless grinder will be specifically described in the following. The grinding process until the periphery of the tip portion Wb of work W is formed in the shape of a small-diameter cylindrical portion and a tapered portion as shown in Fig. 5 (a) is same as in the embodiment 1, and the steps thereafter will be described.
When the periphery of the tip portion Wb of work W has been formed in the shape of a small-diameter cylindrical portion and a tapered portion as shown in Fig. 5 (a), work W feeding operation by pusher 5 is stopped, and then the grinding wheel 1 moves forward (for plus cutting) by a specified distance relative to the tip portion Wb of work W. In this way, the tip portion Wb, as shown in Fig. 5 (b), part of the small-diameter cylindrical portion is further ground into a smaller diameter, thereby forming the tip portion into a swelling stepped shape, and as a result, the tapered portion is further ground as well.
In this condition, the grinding wheel 1 stops moving forward relative to the tip portion Wb of work W, then the work W feeding operation by pusher 5 is started again, and the work W stops when it is axially fed to the predetermined position [see Fig. 5 (c)].
Thus, when the tip portion Wb of work W has been ground into the specified final finish shape, the grinding wheel 1 is completely separated from the work W, thereby completing the grinding operation [see Fig. 5 (d)].
The work W with the tip portion Wb ground is ejected outside from the machining position between grinding wheel 1 and regulating wheel 2.
As described above, in the centerless grinding of the embodiment 1, by controlling the grinding wheel 1 so as to be operated in synchronism with the work W feeding operation by feeding means 15, it is possible to execute grinding of tip portion Wb as shown in Fig. 6 (a) to Fig. 6 (c) although it is not specifically described.
Incidentally, the tip portion Wb of work W shown in Fig. 6 (a) is ground into a stepped cylindrical shape whose tip portion is a shaft extremely small in diameter, and the shape is formed by grinding in that the grinding wheel 1 stops after moving backward only by a specified distance as against the tip portion Wb in predetermined timing with respect to the work W feeding operation by pusher 5.
Also, the tip portion Wb of work W shown in Fig. 6 (b) is ground into a reversely tapered shape, and the shape is formed by grinding in that the grinding wheel 1 slowly moves forward as against the tip portion Wb corresponding to the work W feeding operation by pusher 5.
Further, the tip portion Wb of work W shown in Fig. 6 (c) is ground into a conical shape with a sharp tip, and the shape is formed by grinding in that the grinding wheel 1 moves backward as against the tip portion Wb corresponding to the work W feeding operation by pusher 5.
The other configurations and actions are same as in the embodiment 1.

Embodiment 3

The present preferred embodiment is shown in Fig. 7, wherein the work W feeding structure in the embodiment 1 is improved.
That is, in the embodiment 1, the feeding means 15 is configured so as to feed only the work W in the axial direction X, but in the present preferred embodiment, it is configured so as to feed the work W together with pressing means 14 and regulating wheel 2 in the axial direction X.
Specifically, the pressing means 14 is mounted and supported on regulating wheel housing 25 on which the regulating wheel 2 is rotatably supported, and the regulating wheel housing 25 functions as a mobile base of the feeding means 15. The regulating wheel housing 25 supports the pressing means 14 and regulating wheel 2 placed thereon, and although it is not specifically shown, the mobile base is movable in the axial direction X of work W supported by the regulating wheel 2 and blade 3. Also, the regulating wheel housing 25 is in driving connection to a moving means (not shown). As a moving means for reciprocally moving the regulating wheel housing 25 in the axial direction, properly employed is a linear motor or a conventionally well-known feeding drive unit provided with a feeding screw mechanism.
Also, in this connection, there is provided a stopper 31 on the regulating wheel housing 25, which abuts the rear end of base portion Wa of work W. The stopper 31 is arranged nearly coaxially with the work W and serves a function of axially positioning the work W with respect to the pressing means 14 and regulating means 2.
Thus, in the centerless grinder of the present preferred embodiment, the base portion Wa of work W is pressed and supported by the pressing means 14 against the regulating wheel 2, forcibly rotating the work W, and the work W forcibly rotated is fed in the axial direction X (feed direction) together with the pressing means 14 and regulating wheel 2, and thereby, the tip portion Wb of work W is ground by the grinding wheel 1.
The other configurations and actions are same as in the embodiment 1.

Embodiment 4

The present preferred embodiment is, as shown in Fig. 8, is improved in the work W feeding structure the same as the embodiment 3.
That is, in the present preferred embodiment, it is configured that the grinding wheel 1 is fed by a feeding means (not shown) in the direction Y opposite to the axial direction (feed direction) of work W.
Although it is not specifically shown, the grinding wheel housing on which the grinding wheel 1 is rotatably supported functions as a mobile base of the feeding means. The grinding wheel housing as a mobile base is movable in the axial direction of work W and is also in driving connection to a moving means. As a moving means for reciprocally moving the mobile base or the grinding wheel housing, properly employed is a linear motor or a conventionally well-known feeding drive unit provided with a feeding screw mechanism.
Also, in this connection, there is provided a stopper 31, same as in the embodiment 3, which abuts the rear end of base portion Wa of work W.
Thus, in the centerless grinder of the present preferred embodiment, the base portion Wa of work W is pressed and supported by the pressing means 14 against the regulating wheel 2, forcibly rotating the work W, while the grinding wheel 1 is fed in the direction Y opposite to the axial direction (feed direction) of work W, and thereby, the tip portion Wb of work W is ground by the grinding wheel 1.
The other configurations and actions are same as in the embodiment 1.
In the preferred embodiment described above, as the pressing means 14, for example, it is not limited to pressure roller 4 but also preferable to use a simple mechanism like a spring provided that the mechanism is capable of pressing the work W against the regulating wheel 2. Contrarily, when required, it is also preferable to make accurate control by using a power unit such as a pressing cylinder and the like.
Also, it is possible to perform grinding the base portion Wa of work W into a right cylindrical shape in accordance with the requirement.
As described above, according to the present invention, the base portion of the work is pressed and supported by a pressing means against the regulating wheel, forcibly rotating the work, and the work is fed in the axial direction by the feeding means, and thereby, the tip portion of the work is ground by the grinding wheel. Accordingly, even when the tip portion of the work is extremely small in diameter, it is possible to accurately control the size in grinding lengthwise direction or axial direction of the work, and moreover, because the tip portion of the work is ground in accordance with the diameter of the base portion of the work, it is possible to grind the work into a stepped shape in a short time with little deflection in axial center of the work while maintaining high coaxiality and cylindricity.
In the above detailed description of the invention, the description of specific exemplary embodiments is intended to make clear the technical detail of the present invention. Therefore, the present invention should not be interpreted in a narrow sense by limiting it only to the forgoing examples but in a board sense such that various changes and modifications may be made in the invention without departing from the spirit thereof and the scope of the claims.

Claims

A centerless grinding method for bar-shape work, which may perform centerless grinding of tip portion of bar-shape work.
wherein base portion of the work is pressed and supported by a pressing means against a regulating wheel, forcibly rotating the work, and the work is fed by a feeding means in axial direction relative to a grinding wheel, and thereby, the tip portion of the work is ground by the grinding wheel.
The centerless grinding method for bar-shape work of claim 1, wherein outer periphery of said tip portion is ground by said grinding wheel in accordance with outer diameter of the base portion of said work.
The centerless grinding method for bar-shape work of claim 1 or 2, wherein only the work is axially fed by said feeding means.
The centerless grinding method for bar-shape work of claim 1 or 2, wherein the work is axially fed by said feeding means together with said pressing means and said regulating wheel.
The centerless grinding method for bar-shape work of claim 1 or 2, wherein said grinding wheel is fed by said feeding means in a direction opposite to the axial direction.
The centerless grinding method for bar-shape work of any one of claims 1 to 5, wherein said pressing means is provided with a pressure roller which makes rolling contact with the outer periphery of the base portion of the work while applying a predetermined pressure thereto.
The centerless grinding method for bar-shape work of any one of claims 1 to 6, wherein said grinding wheel is operated for radial feed in synchronism with work feeding operation.
The centerless grinding method for bar-shape work of any one of claims 1 to 7, wherein the wheel surface of said grinding wheel is formed of conductive grinding stone having undergone discharge truing.
A centerless grinder for centerless grinding of tip portion of bar-shape work, comprising:

a blade which supports the base portion of work;

a regulating wheel which is rotationally driven to rotate and support the base portion of the work;

a pressing means for pressing and supporting the work against said regulating wheel;

a grinding wheel which is rotationally driven to grind the tip portion of the work forcibly rotated and supported by said regulating wheel; and

a feeding means which feeds the work forcibly rotated and supported by said regulating wheel and said blade in the axial direction relative to said grinding wheel.
The centerless grinder for bar-shape work of claim 9,
wherein said pressing means comprises a pressure roller capable of making rolling contact with the outer periphery of the work, and a pressing means which presses the pressure roller against the outer periphery of the base portion of the work while applying a predetermined pressure thereto.
The centerless grinder for bar-shape work of claim 9 or 10,
wherein said feeding means serves to feed only the work in the axial direction, and comprises a pusher capable of abutting the rear end of the work, and a moving means for moving the pusher in the axial direction of the work.
The centerless grinder for bar-shape work of claim 9 or 10,
wherein said feeding means serves to feed the work in the axial direction together with the pressing means and said regulating wheel, and comprises a mobile base for mounting and supporting the pressing means and the regulating wheel, and a moving means for moving the mobile base in the axial direction of the work.
The centerless grinder for bar-shape work of claim 9 or 10,
wherein said feeding means serves to feed said grinding wheel in a direction opposite to the axial direction, and comprises a mobile base for mounting and supporting the grinding wheel, and amoving means for moving the mobile base in the axial direction of the work.
The centerless grinder for bar-shape work of any one of claims 9 to 13,
wherein there is provided a structure that said grinding wheel is operated for radial feed relative to the work.
The centerless grinder for bar-shape work of any one of claims 9 to 14,
wherein said grinding wheel is operated for radial feed in synchronism with the work feeding operation by said feeding means.
The centerless grinder for bar-shape work of any one of claims 9 to 15,
wherein the axial center of said grinding wheel is diagonally set in the direction opposite to the work feeding direction.
The centerless grinder for bar-shape work of any one of claims 9 to 16,
wherein the wheel surface of said grinding wheel is formed of conductive grindstone having undergone discharge truing.