U.S. patent application number 11/291816 was filed with the patent office on 2006-06-08 for grinding method of crank pin and grinding machine.
This patent application is currently assigned to TOYODA KOKI KABUSHIKI KAISHA. Invention is credited to Nobumitsu Hori, Makoto Nonoyama, Kikutoshi Okada.
Application Number | 20060121830 11/291816 |
Document ID | / |
Family ID | 35809985 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060121830 |
Kind Code |
A1 |
Hori; Nobumitsu ; et
al. |
June 8, 2006 |
Grinding method of crank pin and grinding machine
Abstract
A grinding method of a crank pin that grinds an outer
circumferential surface of the crank pin of a crankshaft having a
crank journal and the crank pin eccentric to the crank journal by
rotating a crankshaft around a central axis (a center of the
journal) of the crank journal and moving a rotating grinding wheel
in a diametric direction of the crankshaft according to rotation
phase angle of the crankshaft, in which a rotation number of the
crankshaft is changed in one revolution of the crankshaft to
perform a grinding process.
Inventors: |
Hori; Nobumitsu;
(Ichinomiya-shi, JP) ; Nonoyama; Makoto;
(Kariya-shi, JP) ; Okada; Kikutoshi; (Nagoya-shi,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOYODA KOKI KABUSHIKI
KAISHA
Kariya-shi
JP
|
Family ID: |
35809985 |
Appl. No.: |
11/291816 |
Filed: |
December 2, 2005 |
Current U.S.
Class: |
451/11 ;
451/62 |
Current CPC
Class: |
B24B 5/42 20130101; B24B
47/22 20130101 |
Class at
Publication: |
451/011 ;
451/062 |
International
Class: |
B24B 51/00 20060101
B24B051/00; B24B 1/00 20060101 B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2004 |
JP |
2004-350997 |
Claims
1. A grinding method comprising: rotating a crankshaft comprising a
crank journal and a crank pin eccentric to the crank journal around
a central axis of the crank journal; moving a rotating grinding
wheel in a radial direction of the crankshaft according to a
rotation phase angle of the crankshaft; and grinding an outer
circumferential surface of the crank pin by the moving of the
rotating grinding wheel and the rotation of the crankshaft while a
rotation speed of the crank shaft is changed in one revolution of
the crankshaft
2. The grind method according to claim 1, further comprising:
rotating the crankshaft and the grinding wheel in the same
direction; making slow the rotation speed of the crankshaft when
the crank pin is located closer to the grinding wheel than the
center of the crank journal; and making fast the rotation speed of
the crankshaft when the crank pin is located farther from the
grinding wheel than the center of the crank journal.
3. A grinding machine comprising: a grinding wheel capable of
rotating; and a crankshaft having a crank journal and a crank pin
eccentric to the crank journal, wherein an outer circumferential
surface of the crank pin is grinded by rotating the crankshaft
around a central axis of the crank journal and moving the rotating
grinding wheel in a radial direction of the crankshaft according to
a rotation phase angle of the crankshaft, and wherein a rotation
speed of the crankshaft is changed in one revolution of the
crankshaft to perform a grinding process.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims the benefit of
priority from the prior Japanese Patent Application No.
2004-350997, filed on Dec. 3, 2004; the entire contents of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a grinding method of a
crank pin, and particularly to the grinding method of the crank pin
that grinds an outer circumferential surface of a crank pin by
rotating a crankshaft having the crank journal and the crank pin
eccentric to a crank journal around a central axis of the crank
journal and moving a rotating grinding wheel T in a diametric
direction of the crankshaft CS according to a rotation phase angle
of the crankshaft. The present invention also relates to a grinding
machine performing such method.
[0004] 2. Description of the Related Art
[0005] A crankshaft includes a crank journal and a crank pin
eccentric to the crank journal. An outer circumferential surface of
the crank pin is ground by rotating the crankshaft around a central
axis of the crank journal and moving a grinding wheel, facing the
crank pin, in the diametric direction of the crankshaft according
to the rotation phase angle of the crankshaft. Herein, `the
rotation phase angle of the crankshaft` is a position of the
crankshaft represented by an angle in one revolution of the
crankshaft, and more specifically, the location of the crank pin
from a rotation center of the crankshaft, that is, `the central
axis of the crank journal` represented by the rotation angle of the
crankshaft.
[0006] The above grinding method of the crank pin is performed by a
so-called `C-X control`, that is, the control of C-axis and X-axis,
in which the rotation axis of an object is defined as a C-axis and
the moving axis of the grinding wheel in the diametric direction of
the object is defined as an X-axis in a grinding machine having a
numerical value control device such as a NC cylindrical grinding
machine or the like. In addition, in a grinding method of the crank
pin by the C-X control in the related art, the outer
circumferential surface of the crank pin is grinded by controlling
the rotation number of the C-axis to be constant, that is, by
rotating the crankshaft at a constant rotation speed.
SUMMARY OF THE INVENTION
[0007] However, as shown in FIG. 1, when a crankshaft CS is rotated
around a central axis of a crank journal (hereinafter referred to
as `journal center JO`) (solid arrow C), a crank pin P revolves not
only on an axis thereof but also around the journal center JO, a
so-called `sun and planet motion` (one-dotted line A). Therefore, a
relative speed between an outer circumferential surface of a
grinding wheel T and an outer circumferential surface of the crank
pin P is changed according to a rotation phase angle of the
crankshaft SC at grinding portions KS, at which the crank pin P
comes into contact with the grinding wheel T, even when the
crankshaft CS is rotated at a constant speed. As a result, the
grinding speed is changed variously at the grinding portions KS in
one revolution of the crankshaft CS. Furthermore, the changed
grinding speed affects the grinding efficiency or abrasive grain
load essentially. Herein, a grinding speed is the speed of a grind
stone against the object, and a grinding efficiency is an index
expressed by a grinded volume per unit time, and the abrasive grain
load is an index expressed by a maximum cut depth of the abrasive
grain.
[0008] Still furthermore, the grinding portion KS is changed to be
revolved around the journal center JO, the rotation center of the
crankshaft CS. More specifically, the grinding portion KS moves in
an elliptical orbit in one revolution of the crankshaft CS
(one-dotted line B). Therefore, the grinding speed, the grinding
efficiency, and abrasive grain load are variously changed even
more. Since the grinding portion KS deviates vertically from the
central axis PO of the crank pin P, a coolant can be flowed into
the grinding portions KS in various manners, and the cooling effect
or lubrication effect of the coolant is changed in various
manners.
[0009] As described above, in the grinding method of the crank pin
P by the C-X control in the related art, various conditions for a
grinding process described above (hereinafter referred to as simply
`grinding condition`) can be changed variously in one revolution of
the crankshaft CS. In addition, since the grinding wheel T
reciprocates in the X-axis direction as the crankshaft CS is
revolved (solid arrow X), the grinding conditions can be changed by
the mechanical features of the grinding machine, for example, the
delayed following of the X-axis to the c-axis, the rotation speed
of the crankshaft CS or the rotation speed of the grinding wheel T
disturbed by the change in the grinding resistance.
[0010] Furthermore, if the grinding conditions are changed
variously in one revolution of the crankshaft CS, it is impossible
to obtain grinded surfaces having uniform surface roughness
throughout the outer circumferential surface of the crank pin P.
Therefore, the grinding method in the related art cannot meet the
requirement of making the surface roughness uniform throughout the
outer circumferential surface of the crank pin P.
[0011] Since the entire outer circumferential surface of the crank
pin P including the roughest surface has to meet the required
surface roughness, there is a limit in shortening the process time
by hastening the rotation speed of the crankshaft CS, thereby the
grinding method in the related art cannot deal with the requirement
of further shortening the process time. Since no grinding burn has
to occur even under the worst grinding condition, there is a limit
in shortening the process time by hastening the rotation speed of
the crankshaft CS, thereby the grinding method in the related art
cannot meet the requirement of further shortening the process
time.
[0012] Meanwhile, a lifespan of the grind stone is determined under
the worst grinding condition. Herein, even though it can be
considered to improve the grinding condition by making the rotation
speed of the crankshaft CS slow, the process time is increased
considerably in this case, and thus the grinding method in the
related art cannot meet the requirement of improving the lifespan
of the grind stone while the process time is not considerably
increased.
[0013] The invention has been finalized in consideration of the
above problems, and it is an object of the invention to provide a
grinding method of a crank pin which is capable of properly meeting
various requirements that cannot be properly dealt with by the
grinding method of the crank pin using a C-X control in the related
art. In addition, it is another object of the invention to provide
a grinding machine capable of properly meeting the above
requirements.
[0014] According to an aspect of the invention, there is provided a
grinding method including: rotating a crankshaft comprising a crank
journal and a crank pin eccentric to the crank journal around a
central axis of the crank journal; moving a rotating grinding wheel
in a radial direction of the crankshaft according to a rotation
phase angle of the crankshaft; and grinding an outer
circumferential surface of the crank pin by the moving of the
rotating grinding wheel and the rotation of the crankshaft while a
rotation speed of the crank shaft is changed in one revolution of
the crankshaft
[0015] According to the above-aspect, there is provided the grind
method further including: rotating the crankshaft and the grinding
wheel in the same direction; making the rotation speed of the
crankshaft when the crank pin is located closer to the grinding
wheel than the center of the crank journal; and making the rotation
speed of the crankshaft when the crank pin is located farther from
the grinding wheel than the center of the crank journal.
[0016] According to another aspect of the invention, there is
provided a grinding machine including: a grinding wheel capable of
rotating; and a crankshaft having a crank journal and a crank pin
eccentric to the crank journal. An outer circumferential surface of
the crank pin is grinded by rotating the crankshaft around a
central axis of the crank journal and moving the rotating grinding
wheel in a radial direction of the crankshaft according to a
rotation phase angle of the crankshaft. A rotation speed of the
crankshaft is changed in one revolution of the crankshaft to
perform a grinding process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These and other objects and advantages of this invention
will become more fully apparent from the following detailed
description taken with the accompanying drawings in which:
[0018] FIG. 1 is an explanatory view showing a change in locations
of a crank pin in a grinding process by a C-X control; and
[0019] FIG. 2 is a plan view showing an example of a grinding
machine that performs a grinding method of the crank pin according
to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Next, embodiments will be described in detail. Meanwhile,
the following examples describe a so-called "up-cut grinding", in
which a crankshaft and a grinding wheel rotate in the same
direction.
[0021] As shown in FIG. 1, in the grinding method of the crank pin
P by a C-X control, a crank pin P is revolved on an axis thereof
and around a journal center JO of the crankshaft CS, a so-called
sun and planet motion. Therefore, various requirements can be met
by changing the rotation speed, that is, "rotation number (rpm)" of
the crankshaft CS in various manners like the followings in one
revolution of the crankshaft CS. Hereinafter, the rotation speed of
the crankshaft CS will be referred to as "rotation number
(rpm)".
EMBODIMENT 1
[0022] At grinding portions KS, at which the grinding wheel T comes
into contact with the crank pin P, the rotation number of the
crankshaft CS is changed according to a rotation phase angle of the
crankshaft CS in order to make constant the relative speed between
an outer circumferential surface of the grinding wheel T and an
outer circumferential surface of the crank pin P or to make the
change in the relative speed between the outer circumferential
surface of the grinding wheel T and the outer circumferential
surface of the crank pin P small comparing with the constant
rotation number of the crankshaft CS, that is, to make the relative
speed almost constant.
[0023] For example, the rotation number of the crankshaft CS by the
rotation phase angle of the crankshaft CS is extracted from fixed
values defined by the shapes of the crankshaft CS or the grinding
wheel T such as "the diameter of the crank pin P", "the distance
between a journal center JO and a center axis of the crank pin P",
that is, "the eccentric amount of the crank pin P", and "the
diameter of the grinding wheel T" so that the relative speed
between the outer circumferential surface of the grinding wheel T
and the outer circumferential surface of the crank pin P becomes
constant, and then the crankshaft CS is rotated on the basis of the
extracted rotation number. Accordingly, the grinding speed can be
kept constant at the grinding portions KS.
[0024] In addition, if the grinding portions KS are located on a
surface connecting the journal center JO and the rotation center of
the grinding wheel T without vertical deviation with respect to the
journal center JO, the change in the grinding speed can be kept
slow comparing with the constant rotation number of the crankshaft
CS by calculating the rotation number of the crankshaft CS by the
rotation phase angle and rotating the crankshaft CS with a simple
conception not considering the diameter of the grinding wheel
T.
[0025] Meanwhile, in the above embodiment, the change in the
rotation phase angle of the crankshaft CS accompanies the change in
the rotation number of the crankshaft CS in one revolution of the
crankshaft CS. In addition, the rotation speed of the crankshaft CS
becomes slow when the crank pin P is located closer to the grinding
wheel T than the center JO of the crank journal J, and the rotation
speed of the crankshaft CS becomes fast when the crank pin P is
located farther from the grinding wheel T than the center JO of the
crank journal J.
[0026] As described above, the surface roughness can be uniform
throughout the outer circumferential surface of the crank pin P by
changing the rotation number of the crankshaft CS and thus making
the grinding speed constant or almost constant.
EMBODIMENT 2
[0027] In one revolution of the crankshaft CS, since the grinding
portions KS deviate vertically from the surface connecting the
journal center JO and the rotation center of the grinding wheel T,
the position of the crank pin P with respect to the grinding wheel
T is changed. Therefore, the grinding efficiency and abrasive grain
load are affected by the change in the position of the crank pin P
as well as the change in the grinding speed. Therefore, the
rotation number of the crankshaft CS is changed according to the
rotation phase angle of the crankshaft CS in order to make constant
the relevant indices such as grinding efficiency, abrasive grain
load or the like on the basis of fixed values such as "the diameter
of the crank pin P", "the eccentric amount of the crank pin P",
"the diameter of the grinding wheel T" or the like; theoretical
values extracted from fixed values or the like such as
"grinding-removal allowance"; or estimated values extracted while
some fixed values are omitted.
[0028] It is possible to make the grinding conditions constant more
precisely and to make the surface roughness uniform throughout the
outer circumferential surface of the crank pin P by changing the
rotation number of the crankshaft CS as described above.
EMBODIMENT 3
[0029] When the crankshaft CS is revolved at a constant rotation
number, there can be portions having superior surface roughness
than required value and portions capable of enduring severer
grinding conditions, for example, portions without grinding burn
even at a higher grinding speed, throughout the outer
circumferential surface of the crank pin P. Therefore, the rotation
phase angles at the above portions are extracted as the theoretical
values extracted from the various fixed values described above or
values measured after an actual process, and then the rotation
number of the crankshaft CS is changed to make the rotation number
fast at the rotation phase angles.
[0030] Then, the process time can be shortened.
EMBODIMENT 4
[0031] In grinding the outer circumferential surface of the crank
pin P, there is a limit to make the rotation speed of the
crankshaft CS fast when the crankshaft CS needs to be rotated at a
constant rotation number in order to secure the surface roughness
satisfying at least the required values, and to perform a grinding
with no grinding burn generated.
[0032] Contrary to the above, the entire rotation number of the
crankshaft CS is made faster than the rotation number of the
crankshaft CS rotated at a constant rotation number, and the
rotation phase angles at portions having the highest surface
roughness or high possibility of grinding burn are extracted as the
theoretical values extracted from the various fixed values
described above or values measured after an actual process. And
then, the rotation number of the crankshaft CS is changed to
partially make the rotation number slow at the rotation phase
angles.
[0033] Accordingly, the process time can be shortened while the
sufficient process quality is secured.
EMBODIMENT 5
[0034] In an actual grinding process, the grinding conditions are
changed in various manners by the mechanical features of the
respective grinding machines such as the fluctuation in the inflow
way of coolant, the delayed following of the X-axis, the
disturbance in the C-axis or the rotation of the grinding wheel T,
or the like in one revolution of the crankshaft CS. Accordingly,
there are various portions having the surface roughness getting
coarsened or high possibility of grinding burn.
[0035] Therefore, such items as surface roughness, surface
hardness, circularity or the like are examined on a grinded object
after an actual grinding process, and portions barely generating
disadvantages even at a high grinding speed are defined. Then, the
rotation number of the crankshaft CS is partially changed at the
proper rotation phase angles of the crankshaft CS in order to make
the grinding speed fast at the above portions.
[0036] Then, the process time can be shortened while the sufficient
process quality is secured.
EMBODIMENT 6
[0037] In general, it is considered that the lifespan of a grind
stone is shortened further as the grinding condition is worse.
Therefore, the rotation number of the crankshaft CS is partially
changed in order to make the rotation number of the crankshaft CS
slow at the rotation phase angles of the crankshaft CS, at which
the grinding portions KS become portions having bad grinding
conditions, for example, a portion having a fast grinding speed,
portion having a high grinding efficiency, a portion having a high
abrasive grain load, a portion difficult for a coolant to flow in,
a portion having a high possibility of grinding burn, a portion
having a large cutting angle of the abrasive grain, at which the
abrasive grain of the grind stone begins to come into contact with
the object, or the like. That is, bad grinding conditions can be
improved by making the grinding speed slow at the rotation phase
angles of the crankshaft CS having bad grinding conditions.
[0038] Accordingly, the lifespan of the grind stone can be
increased while the rotation number of the crankshaft SC is not
made slow, that is, the process time is not increased considerably
in one revolution of the crankshaft CS. Therefore, the lifespan of
the grind stone can be improved.
[0039] Meanwhile, the grinding process includes various processes,
such as a finish grinding for obtaining a grinded surface of a
final product, a rough grinding performed prior to the finish
grinding, or the like. When the crank pin P is grinded by a series
of processes such as the above various grinding processes, the
rotation number of the crankshaft CS may be changed according to
the type of the grinding process.
[0040] For example, although a high precision of the surface
roughness, circularity or the like is required in the finish
grinding, the precision as high as the above is not required in the
rough grinding. Therefore, in the rough grinding, the shortening of
process time is the top priority, and thus the rotation number of
the crankshaft CS can be changed in order to shorten the process
time of the rough grinding on the condition that no disadvantages
such as grinding burn or the like occurs. On the other hand, in the
finish grinding, the rotation number of the crankshaft CS may be
changed in order to make the crank pin P have a uniform surface
roughness on the entire outer circumferential surface and a precise
circularity.
[0041] Meanwhile, it is preferable that the rotation number of the
crankshaft CS be changed gradually in proper angle ranges before
and after the rotation phase angles, at which the rotation number
becomes the maximum or minimum, when the rotation number is made
fast or slow partially as described in the above examples. Since
there can occur unexpected disadvantages such as portions having
grinding remnants resulting from incomplete removal of the removal
stock, scars on the grinded surface, or the like if the rotation
number of the crankshaft CS is changed abruptly.
[0042] So far, the grinding method of the crank pin P has been
described. The grinding method can be performed preferably by a
grinding machine having a numerical control device. Accordingly, an
example of the grinding machine for performing the grinding method
will be described below.
[0043] FIG. 2 illustrates an example of the grinding machine 10.
The grinding machine 10 includes a control device 50 such as a NC
device, a CNC device, or the like, and more particularly, the
machine 10 is a circular grinding machine capable of grinding a
circular surface of an object.
[0044] The grinding machine 10 includes a bed 20 composing a base,
a Z-axis table 40 loaded on the bed 20 and movable in the Z-axis,
and an X-axis table 30 loaded on the bed 20 and movable in the
X-axis direction. Herein, the Z-axis table 40 is moved in the
Z-axis direction by a Z-axis driving device 41, and the X-axis
table 30 is moved in the X-axis direction by an X-axis driving
device 31. In addition, each of the Z-axis driving device 41 and
the X-axis driving device 31 are composed of a proper driving
source such as a servo motor or the like, and a proper mechanism
such as a feed screw mechanism or the like operated by the driving
source.
[0045] Meanwhile, the Z-axis table 40 of the grinding machine 10
according to the present example supports an object, that is, the
crankshaft CS, more specifically, the crankshaft CS having the
crank journal J and the crank pin P eccentric to the crank journal
J, and composes a so-called `object table`. In addition, a
headstock 42 and a tailstock 43 are loaded on the Z-axis table 40,
and the crankshaft CS is interposed between the headstock 42 and
the tailstock 43 with the crank journals J at both ends contact the
headstock 42 and the tailstock 43 respectively, and thus is
rotatably supported by the Z-axis table 40. Furthermore, the
headstock 42 includes a spindle-driving device (not shown), and the
crankshaft CS is revolved by the spindle-driving device around the
central axis of the crank journals J.
[0046] Meanwhile, the X-axis table 30 includes a grinding wheel
shaft, on which a grinding wheel T is installed, a bearing that
rotatably bears the grinding wheel, and a grinding wheel driving
device 32 that rotates the grinding wheel through a transmission
mechanism such as belt or the like, and composes a so-called
"grinding wheel table".
[0047] Furthermore, the Z-axis driving device 41, the X-axis
driving device 31, the grinding wheel driving device 32, and the
head-driving device are connected with the control device 50
including a computer, and the control device 50 controls the above
driving devices.
[0048] Although not shown in the drawings, the control device 50
includes various control units, as functional components, such as a
Z-axis control unit that controls the Z-axis driving device 41, an
X-axis control unit that controls the X-axis driving device 31, a
grinding wheel control unit that controls the grinding wheel
driving device 32, and a C-axis control unit that controls the
spindle-driving device. In addition, although the Z-axis control
unit, the X-axis control unit, and the grinding wheel driving
control unit are constructed similar to those in the related art,
the C-axis control unit is constructed to have a peculiar function
not known in the related art. Hereinafter, the C-axis control unit
will be described in detail.
[0049] The C-axis control unit includes a calculation unit that
performs calculation on the basis of numerical values inputted to
the control device 50 (hereinafter referred to as `input values`) .
Herein, various values can be set as the input values, and thus the
C-axis control unit performs various calculations according to the
input values and controls the head-driving device to rotate the
crankshaft CS at the rotation number corresponding to the rotation
phase angle.
[0050] For example, when the rotation number of the crankshaft CS
needs to be changed in order to perform a grinding under the
constant or almost constant conditions, numerical values for
determining the grinding conditions such as "grinding speed",
"grinding efficiency", "abrasive grain load" or the like can be set
as the input values.
[0051] The C-axis control unit calculates the rotation number
corresponding to the rotating angle of the crankshaft CS as the
theoretical value by using the input value and the previously
stored calculation equation in order to make the grinding
conditions constant or almost constant, and controls the rotation
of the spindle-driving device on the basis of the calculation
result.
[0052] Meanwhile, in the calculation equation calculated by the
C-axis control unit, proper fixed values corresponding to the
calculation equation from various fixed values such as fixed values
relating to the shapes of the crankshaft CS or the grinding wheel T
such as "the diameter of the crank pin P", "the eccentric amount of
the crank pin P", "the diameter of the grinding wheel T", "grinding
removal stock" or the like, fixed values relating to the grinding
contents, or the like are used. The fixed values can be inputted to
the control device 50 before the input values.
[0053] In addition, when the rotation number of the crankshaft CS
needs to be changed at a certain rotation phase angle in order to
meet the desired requirements such as the shortening of the
grinding process time, the improvement of the grind stone lifespan
or the like, values defining the rotation phase angle, at which the
rotation number is changed, or values of the changed rotation
number or the like can be set as the input value.
[0054] For example, a proper position of the crankshaft CS such as
the position of the crankshaft CS at a location, at which the crank
pin P is located at the rearmost from the crank journal JO (a
location expressed by a solid line in FIG. 1), or the like is
defined as a reference value of the rotation phase angle `0`
degree, and angles, at which the rotation number needs to be
changed, are defined as `a.degree.`. In addition, the rotation
number `b` rpm, the ratio of the rotation number to the previously
set rotation number `b` % or the like are defined in order to
specify the rotation number to be changed. Then the `a` and `b` can
be set as the input values.
[0055] The C-axis control unit performs a calculation by using the
input values and the previously stored calculation equation and
controls the rotation of the head-driving device on the basis of
the calculation result.
[0056] Meanwhile, when the rotation number of the crankshaft CS
needs to be changed slowly, an angle range, in which the rotation
number can be changed, is defined by a specific angle range
`c.degree. to `d.degree.` that includes `a.degree.` or by an
allowable angle range `e.degree.` from the reference angle
`a.degree.`, and thus the values `c.degree.` and `d.degree.`,
`e.degree.` or the like can be used as the input value for the
calculation. In the above system, the head-driving device is
controlled to increase slowly the changing amount of the rotation
number from a predetermined rotation number as the rotation phase
angle exceeds `c.degree.` or `a.degree.-e.degree.`, to make the
changing amount reach the maximum at `a.degree.`, to decrease the
changing amount as the rotation phase angle approaches `d.degree.`
or `a.degree.+e.degree.`, and to make the changing amount return to
the predetermined rotation number when the rotation phase angle
exceeds `d.degree.` or `a.degree.+e.degree.`. Therefore, the
rotation number of the crankshaft CS does not change abruptly.
[0057] According to the above-embodiments, since the rotation
speed, so-called `rotation number (rpm) `, of the crankshaft is not
constant, that is, changed in one revolution of the crankshaft, the
grinding condition can be changed as desired in one revolution of
the crankshaft.
[0058] For example, a grinding can be performed at a constant
grinding speed by changing the rotation speed of the crankshaft in
order to make constant the relative speed between the outer
circumferential surface of the grinding wheel and the outer
circumferential surface of the crank pin in one revolution of the
crankshaft. As a result, the surface roughness can be uniform
throughout the outer circumferential surface of the crank pin.
[0059] According to the above-embodiments, the grinding condition
can be variously changed by making fast or slow the rotation speed
locally at proper rotation phase angles of the crankshaft. As a
result, the process time can be shortened, and the lifespan of the
grind stone can be improved while the entire rotation speed of the
crankshaft is not made slow in the revolution.
[0060] According the above-embodiments, since the crankshaft and
the grinding wheel are rotated in the same direction, the moving
direction of the circumferential surface of the grinding wheel is
opposite to that of the outer circumferential surface of the crank
pin at the grinding portions, thereby the grinder performs a
so-called `up-cut grinding`. Meanwhile, since the grinding portions
are moved vertically along the shaft line connecting the central
axis of the rotating crank journal of the crankshaft with the
rotation center of the grinding wheel according to the rotation of
the crankshaft, the relative speed between the outer
circumferential surface of the crank pin and the outer
circumferential surface of the grinding wheel is changed as much as
the vertical movement, described above, at the grinding portions,
at which up-cut grinding is performed when the crankshaft is
rotated at a constant rotation speed. More specifically, the
relative speed becomes fast when the crank pin is located closer to
the grinding wheel than the central axis of the crank journal, and,
on the contrary, the relative speed becomes slow when the crank pin
is located farther from the grinding wheel than the central axis of
the crank journal. In addition, the grinding condition deteriorates
when the relative speed is made fast, and the grinding condition
improves when the relative speed is made slow.
[0061] According to the above-embodiments, it is possible to
suppress the deterioration of the grinding condition when the crank
pin is located at positions making the grinding condition worse and
to suppress the unnecessary improvement of the grinding condition
when the crank pin is located at positions making the grinding
condition exceedingly better.
[0062] According to the above-embodiments, the above grinding
machine may be used for performing the above grinding method.
Therefore, the grinding machine can properly meet various
requirements for a grinding.
[0063] According to the above-embodiments, the grinding method of
the crank pin can deal properly with various requirements that
cannot be met by the grinding method of the crank pin using the C-X
control in the related art. According to the above-embodiments, the
grinding machine can perform a grinding that can properly meet the
various requirements described above.
[0064] The foregoing description of the embodiments of the present
invention has been provided for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise forms disclosed. Obviously, many
modifications and variations will be apparent to practitioners
skilled in the art. The embodiments were chosen and described in
order to best explain the principles of the invention and its
practical applications, thereby enabling others skilled in the art
to understand the invention for various embodiments and with the
various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined solely by the following claims and their equivalents.
* * * * *