U.S. patent application number 12/528196 was filed with the patent office on 2009-12-31 for carburizing apparatus and carburizing method.
Invention is credited to Takashi Nakabayashi, Hiroshi Nakai.
Application Number | 20090320962 12/528196 |
Document ID | / |
Family ID | 39709961 |
Filed Date | 2009-12-31 |
United States Patent
Application |
20090320962 |
Kind Code |
A1 |
Nakai; Hiroshi ; et
al. |
December 31, 2009 |
CARBURIZING APPARATUS AND CARBURIZING METHOD
Abstract
A carburizing apparatus that performs a vacuum carburizing
treatment with respect to an object includes: a carburizing furnace
that contains the object; a gas supply apparatus that supplies a
carburizing gas to the carburizing furnace; a light emitting device
that emits light by using an in-furnace gas inside of the
carburizing furnace which is supplied with the carburizing gas; a
light receiving device that receives light emitted from the light
emitting device; and a processing device that calculates the
composition of the in-furnace gas based on the light receiving
result of the light receiving device.
Inventors: |
Nakai; Hiroshi;
(Yokohama-shi, JP) ; Nakabayashi; Takashi;
(Chita-gun, JP) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
US
|
Family ID: |
39709961 |
Appl. No.: |
12/528196 |
Filed: |
February 14, 2008 |
PCT Filed: |
February 14, 2008 |
PCT NO: |
PCT/JP2008/052411 |
371 Date: |
August 21, 2009 |
Current U.S.
Class: |
148/216 ;
266/80 |
Current CPC
Class: |
F27B 17/0016 20130101;
C23C 8/22 20130101; G01N 21/67 20130101; F27D 7/06 20130101; C23C
8/20 20130101; C21D 1/74 20130101; C21D 1/773 20130101; C21D 1/06
20130101 |
Class at
Publication: |
148/216 ;
266/80 |
International
Class: |
C21D 3/00 20060101
C21D003/00; C21D 11/00 20060101 C21D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2007 |
JP |
2007-043973 |
Claims
1. A carburizing apparatus that performs a vacuum carburizing
treatment with respect to an object comprising: a carburizing
furnace that contains the object; a gas supply apparatus that
supplies a carburizing gas to the carburizing furnace; a light
emitting device that emits light by using an in-furnace gas inside
of the carburizing furnace which is supplied with the carburizing
gas; a light receiving device that receives light emitted from the
light emitting device; and a processing device that calculates the
composition of the in-furnace gas based on the light receiving
result of the light receiving device.
2. The carburizing apparatus according to claim 1, wherein the
light emitting device emits light by using the in-furnace gas which
is introduced to a detection space connected to an internal space
of the carburizing furnace.
3. The carburizing apparatus according to claim 1, wherein the
light emitting device emits light by imparting energy to the
in-furnace gas.
4. The carburizing apparatus according to claim 3, wherein the
light emitting device generates plasma in a space which includes
the in-furnace gas.
5. The carburizing apparatus according to claim 3, wherein the
light emitting device emits a laser light into the in-furnace
gas.
6. The carburizing apparatus according to claim 1, wherein the
light receiving device detects the light intensity emitted from the
light emitting device.
7. The carburizing apparatus according to claim 1, further
comprising: a control device that controls at least one of an
amount of the carburizing gas supplied per unit time by the gas
supply apparatus or a carburizing time based on the composition of
the in-furnace gas calculated by the processing device.
8. A carburizing method that performs a vacuum carburizing
treatment with respect to an object comprising: supplying a
carburizing gas to a carburizing furnace that contains the object;
causing an in-furnace gas existing inside of the carburizing
furnace which is supplied with the carburizing gas to emit light;
receiving the light which is emitted; and calculating a composition
of the in-furnace gas based on the light receiving result.
9. The carburizing method according to claim 8, wherein the
receiving the light further comprising detecting intensity of the
light received; and the carburizing method further comprising:
calculating the relationship in advance between the composition of
the in-furnace gas and the intensity of the light which caused the
in-furnace gas to emit light; and calculating the composition of
the in-furnace gas based on the relationship and the light
intensity which is detected.
Description
TECHNICAL FIELD
[0001] The present invention relates to a carburizing apparatus and
carburizing method.
[0002] Priority is claimed on Japanese Patent Application No.
2007-43973, filed Feb. 23, 2007, the content of which is
incorporated herein by reference.
BACKGROUND ART
[0003] A vacuum carburization, which is performed under reduced
pressure, has been conventionally known as one of the carburizing
treatments that are used for surface treatment of steel.
[0004] The following Patent documents disclose part of examples of
techniques related to the vacuum carburization.
[0005] Patent Document 1: Japanese Unexamined Patent Application,
first publication No. 2001-081543
[0006] Patent Document 2: Japanese Unexamined Patent Application,
first publication No. 2001-240954
[0007] Patent Document 3: Japanese Unexamined Patent Application,
first publication No. 2001-262313
[0008] Patent Document 4: Japanese Unexamined Patent Application,
first publication No. 2002-173759
[0009] Patent Document 5: Japanese Unexamined Patent Application,
first publication
[0010] Patent Document 6: Japanese Unexamined Patent Application,
first publication No. 2004-053507
[0011] Patent Document 7: Japanese Unexamined Patent Application,
first publication No. 2004-059959
[0012] Patent Document 8: Japanese Unexamined Patent Application,
first publication No. 2004-332075
[0013] Patent Document 9: Japanese Unexamined Patent Application,
first publication No. 2005-350729
[0014] Patent Document 10: Japanese Unexamined Patent Application,
first publication No. 2005-351761
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0015] conventionally, as one of the methods to confirm
reproducibility of the vacuum carburization treatment, sampling
inspections have been performed with respect to objects to be
treated (steel) after being treated by the vacuum carburizing
treatment. In particular, the vacuum carburizing treatment has been
performed with respect to the objects to be treated by controlling,
for example, various carburizing conditions (carburizing time,
carburizing temperature, the amount of a carburizing gas supplied,
or the like). The treatment has been followed by inspecting
carburizing quality (surface carburization density, carburization
density distribution, case hardness, effective case depth after
carburizing, or the like) by sampling the objects to be treated
after being treated by the vacuum carburizing treatment. The
treatment has been further followed by confirming whether or not a
desired carburizing quality has been obtained, or re-adjusting the
carburizing conditions so as to obtain the desired carburizing
quality.
[0016] However, with the above-described method, in order to obtain
the desired carburizing quality, a cumbersome process is necessary,
in which quality confirmation results of the objects to be treated
with carburizing needs to be fed back in each case. Also, in the
case where the amount of the carburizing gas is not appropriate
with respect to the size of the objects to be treated with
carburizing, the following problems occur. For example, in the case
where the amount of the carburizing gas is too little with respect
to the size of the objects to be treated with carburizing, the
carburizing quality fluctuates because the amount of the
carburizing gas which is supplied to surfaces of the objects to be
treated with carburizing fluctuates. In contrast, in the case where
the amount of the carburizing gas is too much with respect to the
size of the objects to be treated with carburizing, soot is
generated in a carburizing furnace due to excessive gas that does
not contribute to the carburizing, and accordingly, maintenance
work for getting rid of the soot is frequently necessary.
[0017] In order to perform the vacuum carburizing treatment with
excellent reproducibility, it is preferable to control the
composition of an in-furnace gas inside of the carburizing furnace.
Accordingly, it is necessary to calculate the composition of the
in-furnace gas immediately and accurately, use the calculated
result, and perform appropriate treatments in order to have a
desired composition of the in-furnace gas. However, conventionally,
an effective method for calculating the composition of the
in-furnace gas immediately and accurately has not been established.
Accordingly, an effective method for calculating the composition of
the in-furnace gas immediately and accurately has been
demanded.
[0018] The present invention was achieved in view of the forgoing
circumstances and has an objective to provide a carburizing
apparatus and carburizing method that enables calculations of the
composition of the in-furnace gas immediately and accurately and
preferably perform the vacuum carburizing treatment with high
reproducibility.
Means for Solving the Problem
[0019] In order to solve the aforementioned problems, the present
invention employs the following structures.
[0020] A first aspect of the present invention is a carburizing
apparatus that performs a vacuum carburizing treatment with respect
to an object. The carburizing apparatus includes: a carburizing
furnace that contains the object; a gas supply apparatus that
supplies a carburizing gas to the carburizing furnace; a light
emitting device that emits light by using an in-furnace gas inside
of the carburizing furnace which is supplied with the carburizing
gas; a light-receiving device that receives light emitted from the
light emitting device; and a processing device that calculates the
composition of the in-furnace gas based on the light receiving
result of the light receiving device.
[0021] In accordance with the first aspect of the present
invention, since the light emitting device that emits light by
using the in-furnace gas and the light-receiving device that
receives light emitted from the light emitting device are provided,
it is possible to optically calculate the composition of the
in-furnace gas immediately and accurately based on the light
receiving result of the light receiving device. Accordingly, by
using the calculated result, it is possible to perform appropriate
treatments in order to achieve desired composition of the
in-furnace gas and preferably to perform the vacuum carburizing
treatment with high reproducibility.
[0022] In the carburizing apparatus of the above aspect, a
structure may be employed, in which the light emitting device emits
light by using the in-furnace gas introduced to a detection space
which is connected to an internal space of the carburizing
furnace.
[0023] In accordance with the above structure, an exclusive
detection space different from the internal space of the
carburizing furnace for emitting light by the light emitting device
is provided. Accordingly, it is possible to smoothly perform a
light emitting operation using the light emitting device and a
light receiving operation using the light-receiving device. Since
the detection space is connected with the internal space of the
carburizing furnace, the environment of the detection space
corresponds to the internal space of the carburizing furnace.
Accordingly, under the environment corresponding to the internal
space of the carburizing furnace, it is possible to emit light by
using the in-furnace gas.
[0024] In the carburizing apparatus of the above aspect, a
structure may be employed, in which the light emitting device emits
light by imparting energy to the in-furnace gas.
[0025] In accordance with the above structure, the light emitting
device can emit light by forming the in-furnace gas into an excited
state.
[0026] In the carburizing apparatus of the above aspect, a
structure may be employed, in which the light emitting device
generates plasma in a space which includes the in-furnace gas.
[0027] In accordance with the above structure, the light emitting
device can emit light by forming the in-furnace gas into an excited
state.
[0028] In the carburizing apparatus of the above aspect, a
structure may be employed, in which the light emitting device emits
a laser light into the in-furnace gas.
[0029] In accordance with the above structure, the light emitting
device can emit light by forming the in-furnace gas into an excited
state.
[0030] In the carburizing apparatus of the above aspect, a
structure may be employed, in which the light receiving device
detects intensity of the light emitted from the light emitting
device.
[0031] In accordance with the above structure, since the light
emitting device emits light having a predetermined wavelength and
intensity corresponding to the composition of the in-furnace gas,
it is possible to calculate the composition of the in-furnace gas
accurately based on the light receiving result of the light
receiving device.
[0032] In the carburizing apparatus of the above aspect, a
structure may be employed, in which a control device is provided
that controls at least one of an amount of the carburizing gas
supplied per unit time by the gas supply apparatus or the
carburizing time based on the composition of the in-furnace gas
calculated by the processing device.
[0033] In accordance with the above structure, the control device
can have a desired composition of the in-furnace gas and preferably
perform the vacuum carburizing treatment with high reproducibility
by controlling the amount of the carburizing gas per unit time
supplied from the gas supply apparatus or by controlling the
carburizing time based on the calculated composition of the
in-furnace gas.
[0034] A second aspect of the present invention is a carburizing
method which performs the vacuum carburizing treatment with respect
to the object. The carburizing method includes: supplying the
carburizing gas to the carburizing furnace that contains the
object; causing an in-furnace gas existing inside of the
carburizing furnace which is supplied with the carburizing gas to
emit light; receiving the light which is emitted and; calculating
the composition of the in-furnace gas based on the light receiving
result.
[0035] In accordance with the second aspect of the present
invention, since an operation which causes the in-furnace gas to
emit light and an operation which receives the light which is
emitted are performed, it is possible to optically calculate the
composition of the in-furnace gas immediately and accurately based
on the light receiving result. Accordingly, by using the calculated
result, it is possible to perform appropriate treatments in order
to have a desired composition of the in-furnace gas and preferably
to perform the vacuum carburizing treatment with high
reproducibility.
[0036] In the carburizing method of the above aspect, a structure
may be employed, in which the operation which receives the light
includes an operation which detects the intensity of the light
received and further includes an operation which calculates the
relationship in advance between the composition of the in-furnace
gas and the intensity of the light which caused the in-furnace gas
to emit light. Accordingly, it is possible to calculate the
composition of the in-furnace gas based on the relationship and the
light intensity of the detected light.
[0037] In accordance with the above method, by calculating the
relationship between the composition of the in-furnace gas and the
intensity of the light which the in-furnace gas emits in advance,
it is possible to calculate the composition of the in-furnace gas
accurately based on the relationship and the light intensity of the
detected light.
EFFECT OF THE INVENTION
[0038] In accordance with the present invention, it is possible to
calculate the state of the in-furnace gas inside of the carburizing
furnace immediately and accurately Accordingly, it is possible to
preferably perform the vacuum carburizing treatment with high
reproducibility.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is an outline block diagram showing a carburizing
apparatus in accordance with a present embodiment.
[0040] FIG. 2 is an enlarged view showing the vicinity of a light
emitting device and of a light receiving device.
[0041] FIG. 3A is a schematic view explaining the relationship
between a carburizing condition and an in-furnace gas.
[0042] FIG. 3B is a schematic view explaining the relationship
between a carburizing condition and an in-furnace gas.
[0043] FIG. 4 is a view showing an example of an emission spectrum
developed based on a light receiving result of a light receiving
device.
[0044] FIG. 5 is a view showing the relationship between the
partial pressure ratio and the normalized value of the light
emission intensity corresponding to the partial pressure ratio.
[0045] FIG. 6 is a schematic view showing an alternative example of
a light emitting device.
[0046] FIG. 7 is a schematic view showing an alternative example of
a light emitting device.
[0047] FIG. 8 is a schematic view showing an alternative example of
a light emitting device.
BRIEF DESCRIPTION OF THE REFERENCE NUMERALS
[0048] 1 Carburizing apparatus [0049] 2 Carburizing furnace [0050]
3 Gas supply mechanism [0051] 4 Gas emission mechanism [0052] 5
Light emitting device [0053] 6 Light receiving device [0054] 7
Processing device [0055] 8 Control device [0056] 12 Treatment room
(internal space) [0057] 15 Discharge room (detection space)
BEST MODE FOR CARRYING OUT THE INVENTION
[0058] Hereinbelow, embodiments of the present invention shall be
described with reference to the appended drawings. The present
invention shall not be limited to the following embodiments, and
structural elements of the embodiments may be arbitrarily combined
for example.
[0059] FIG. 1 is an outline block diagram showing a carburizing
apparatus in accordance with the present embodiment. The present
embodiment shall be described with a vacuum carburizing apparatus
as an example of the carburizing apparatus, in which the
carburizing apparatus performs a carburizing treatment under
reduced pressure (below atmospheric pressure) with respect to
objects to be treated such as steel.
[0060] In FIG. 1, a carburizing apparatus 1 is provided with: a
carburizing furnace 2 that contains an object to be treated S such
as a steel which is to be treated with a vacuum carburizing
treatment; a gas supply mechanism 3 that supplies carburizing gas
G1 to the carburizing furnace 2; a gas emission mechanism 4 that
emits to the outside an in-furnace gas G2 which exists inside of
the carburizing furnace 2 and is supplied with the carburizing gas
G1; a light emitting device 5 that emits light by using the
in-furnace gas G2 existing inside of the carburizing furnace 2
which is supplied with the carburizing gas G1; a light receiving
device 6 that receives light emitted from the light emitting device
5; a processing device 7 that calculates the composition of the
in-furnace gas G2 based on the light receiving result of the light
receiving apparatus 6; and a control device 8 that controls the
whole operation of the carburizing apparatus 1. To the control
device 8, a storage device 9 that stores each piece of information
about the carburizing treatment; an output device 10 that is
capable of outputting information about the carburizing treatment;
and an input device 11 that is capable of inputting operational
signals to the control device 8 are connected. The output device 10
may be a display, a printer, or the like. The input device 11 may
be a keyboard, a mouse, or the like.
[0061] The carburizing furnace 2 has an internal space (treatment
room) 12 where the object to be treated S is disposed. The
carburizing furnace 2 has a furnace wall 2A and an adiabatic wall
2B. The treatment room 12 is formed inside of the adiabatic wall
2B.
[0062] The gas supply mechanism 3 supplies the carburizing gas G1
to the treatment room 12 of the carburizing furnace 2. The gas
supply mechanism 3 is provided with: a gas supply device 3A that is
capable of sending the carburizing gas G1; an air supply opening 3M
that is formed in part of the treatment room 12; and an air supply
pipe 3L that connects the gas supply device 3A and the air supply
opening 3M. The gas supply mechanism 3 is provided with an
adjustment mechanism 3B that adjusts the amount of the carburizing
gas G1 supplied per unit time to the treatment room 12. The
adjustment mechanism 3B includes a bulb mechanism and is connected
to the control device 8. The control device 8 can adjust the amount
of the carburizing gas G1 supplied by the gas supply mechanism 3
per unit time to the treatment room 12 by controlling the
adjustment mechanism 3B.
[0063] The carburizing gas G1, which includes a predetermined
hydrocarbon system gas, is a gas that is supplied to the treatment
room 12 so as to perform the vacuum carburizing treatment on the
object to be treated S. In the present embodiment, the gas supply
mechanism 3 supplies acetylene (C.sub.2H.sub.2) to the treatment
room 12 as the carburizing gas G1.
[0064] The gas emission mechanism 4 emits the in-furnace gas G2,
existing inside of the treatment room 12 of the carburizing furnace
2 where the carburizing gas G1 is supplied, to the outside of the
treatment room 12. The gas emission mechanism 4 includes a vacuum
system such as a vacuum pump or the like and is provided with: a
gas suction device 4A that can suction gas; an exhaust opening 4M
that is formed in part of the treatment room 12; and an exhaust
pipe 4L that connects the gas suction device 4A to the exhaust
opening 4M.
[0065] The in-furnace gas G2 is a gas which was supplied to the
treatment room 12 by the gas supply mechanism 3. The in-furnace gas
G2 includes at least one of the following gases: the gas (reaction
gas) which is left after the carburizing gas G1 is chemically
reacted (carburizing reaction) in the treatment room 12 by the
carburizing treatment, or the gas (non-reaction gas) which is the
carburizing gas which is not used for the carburizing treatment and
hasn't cause the carburizing reaction. For example, in accordance
with the carburizing condition, there is a case, in which not all
of the carburizing gas G1 supplied to the treatment room 12 is used
for the carburizing reaction. In this case, there exists both the
gas (reaction gas) used for the carburizing treatment and the gas
(non-reaction gas) not used for the carburizing treatment in the
treatment room 12. The gas which is emitted from the treatment room
12 includes both the reaction gas and the non-reaction gas.
[0066] As described above, in the present embodiment, acetylene
(C.sub.2H.sub.2) is supplied in the treatment room 12 as the
carburizing gas G1. The part of the acetylene supplied to the
treatment room 12 which caused carburizing reaction with the object
to be treated S generates a carbon component and a hydrogen
component. That is, the carburizing reaction of the present
embodiment is represented by C.sub.2H.sub.2.fwdarw.H.sub.2+2C. The
carbon component generated by the carburizing reaction permeates
(carburize) the surface of the object to be treated S and the
hydrogen is emitted from the treatment room 12. That is, in the
present embodiment, a main component of the reaction gas after the
carburizing gas G1 causing the carburizing reaction is hydrogen
gas. Also, in the present embodiment, a main component of the
non-reaction gas which was not used for the carburizing treatment
and did not cause the chemical reaction is acetylene.
[0067] The light emitting device 5 emits light by using the
in-furnace gas G2. The light emitting device 5 emits light by using
the in-furnace gas G2 which is introduced to a detection space 15
which is connected to the treatment room 12 of the carburizing
furnace 2. The light emitting device 5 is provided with a discharge
member 5A that has an internal space (detection space, discharge
room) 15 which is connected to the midstream of the exhaust pipe 4L
and an electrode which is disposed in the discharge room 15 of the
discharge member 5A that generates plasma in the discharge room 15.
The discharge member 5A can be made of a discharge tube (for
example, a Geissler tube). The exhaust pipe 4L and the discharge
room 15 are connected and the treatment room 12 and the discharge
room 15 are connected via the exhaust pipe 4L. At least part of the
in-furnace gas G2 which is emitted from the treatment room 12 and
flows in the exhaust pipe 4L is introduced to the discharge room
15. The light emitting device 5 generates plasma in the discharge
room 15 where the in-furnace gas G2 is introduced. The light
emitting device causes the in-furnace gas G2 to emit light by
generating plasma. As described above, in the present embodiment,
the light emitting device 5 can emit light by using the in-furnace
gas G2 which is introduced to the discharge room 15 which is
connected to the treatment room 12 of the carburizing furnace
2.
[0068] The light receiving device 6 receives light emitted from the
light emitting device 5. The light receiving device 6 includes a
spectroscope disposed in the vicinity of the discharge member 5A of
the light emitting device 5. The light receiving device 6 including
the spectroscope can detect the light intensity and the emission
spectrum of the light emitted from the discharge member 5A of the
light emitting device 5. The light receiving device 6 is connected
to the processing device 7 (control device 8) and detection result
(light receiving result) of the light receiving device 6 is output
to the processing device 7 (control device 8).
[0069] The processing device 7 is provided with a CPU or the like
and is capable of performing a predetermined arithmetic processing,
various information processing, or the like. The light receiving
result of the light receiving device 6 is output to the processing
device 7. The processing device 7 can calculate the composition of
the in-furnace gas G2 based on the light receiving result of the
light receiving device 6.
[0070] The carburizing apparatus 1 is provided with a temperature
adjustment device 13 which can adjust at least one of the
temperature of the treatment room 12 or the temperature of the
object to be treated S which is contained in the treatment room 12.
At least part of the temperature adjustment device 13 is disposed
in the treatment room 12. The temperature adjustment device 13
includes a heating device (heater). The control device 8 can
control (heat) the temperature of the treatment room 12 and the
object to be treated S which is contained in the treatment room 12
to a predetermined temperature by controlling the temperature
adjustment device 13 including the heating device. Also, the
carburizing apparatus 1 is provided with a temperature sensor 16
which can detect the temperature of the treatment room 12. At least
part of the temperature sensor 16 (a probe or the like) is disposed
in the treatment room 12. The temperature sensor 16 is connected to
the control device 8 and a detection result of the temperature
sensor 16 is output to the control device 8. The control device 8
can adjust the temperature of the treatment room 12 to a
predetermined temperature by controlling the temperature adjustment
device 13 including the heating device based on the detection
result of the temperature sensor 16.
[0071] The control device 8 can adjust (reduce) the pressure of the
treatment room 12 by controlling the gas suction device 4A
including the vacuum system. The carburizing apparatus 1 is
provided with a pressure sensor 17 which can detect the pressure of
the treatment room 12. At least part of the pressure sensor 17
(probe or the like) is disposed in the treatment room 12. The
pressure sensor 17 is connected to the control device 8 and a
detection result of the pressure sensor 17 is output to the control
device 8. The control device 8 can adjust the pressure of the
treatment room 12 to a desired pressure by controlling the gas
suction device 4A including the vacuum system based on the
detection result of the pressure sensor 17.
[0072] Next, an operation of the carburizing apparatus 1 having the
above-described structure shall be described. In order to perform
the vacuum carburizing treatment with respect to the object to be
treated S, the control device 8 heats the treatment room 12 of the
carburizing furnace 2 which contains the object to be treated S by
using the temperature adjustment device 13. At the same time, the
control device 8 reduces the pressure (increase vacuum) of the
treatment room 12 by suctioning the gas in the treatment room 12 by
using the gas emission mechanism 4. After the treatment room 12 is
set to a predetermined heating state and pressure reduced state,
the control device 8 supplies a predetermined amount of the
carburizing gas G1 per unit time from the gas supply mechanism 3
with respect to the treatment room 12 of the carburizing furnace 2
which contains the object to be treated S. The control device 8
performs the vacuum carburizing treatment with respect to the
object to be treated S for a predetermined time while the control
device supplying the predetermined amount of the carburizing gas G1
per unit time from the gas supply mechanism 3 to the treatment room
12, emitting the gas in the treatment room 12 from the gas emission
mechanism 4, and maintaining a predetermined heating state and
pressure reduced state of the treatment room 12. The in-furnace gas
G2 in the treatment room 12 is emitted via the exhaust opening 4M
and flows in the exhaust pipe 4L. Part of the in-furnace gas G2
flowing in the exhaust pipe 4L flows toward to the gas suction
device 4A and another part of the in-furnace gas G2 flows into the
discharge room 15 of the light emitting device 5. The control
device 8 causes the in-furnace gas G2 to emit light by using the
light emitting device 5.
[0073] FIG. 2 is an enlarged view showing the vicinity of the light
emitting device 5 and the light receiving device 6. As shown in
FIG. 2, the light emitting device 5 is provided with the discharge
member 5A having the discharge room 15 and electrodes 5B that are
disposed in the discharge room 15 of the discharge member 5A and
generate plasma in the discharge room 15. The light emitting device
5 generates plasma in the discharge room 15. The in-furnace gas G2
emitted from the treatment room 12 is introduced into the discharge
room 15 and is supplied to a plasma generation area PU, in which
plasma is generated, in the discharge room 15. The light emitting
device 5 causes the in-furnace gas G2 to emit light by generating
plasma.
[0074] The light receiving device 6 receives light, which is
emitted by the in-furnace gas G2 inside the light emitting device
5. The detection result (light receiving result) of the light
receiving device 6 is output to the processing device 7. The
processing device 7 calculates the composition of the in-furnace
gas G2 based on the light receiving result of the light receiving
device 6. In the present embodiment, the vacuum carburizing
treatment with respect to the object to be treated S in the
treatment room 12, the light emitting operation by the light
emitting device 5, and the light receiving operation by the light
receiving device 6 are performed in parallel. That is, while the
vacuum carburizing treatment is performed with respect to the
object to be treated S, the light receiving operation by the light
receiving device 6 and the processing operation by the processing
device 7 (operation that calculates the composition of the
in-furnace gas G2) based on the light receiving result are
performed in real time.
[0075] The control device 8 controls, by using the adjustment
mechanism 3B, the amount of the carburizing gas G1 supplied per
unit time with respect to the treatment room 12 by the gas supply
mechanism 3 based on the composition of the in-furnace gas G2 which
is calculated by the processing device 7. That is, in the present
embodiment, the control device 8 controls in real time a supply
operation of the carburizing gas G1 with respect to the treatment
room 12 (control the adjustment mechanism 3B) by the gas supply
mechanism 3 based on the composition of the in-furnace gas G2 which
is calculated by the processing device 7 while the vacuum
carburizing treatment is performed with respect to the object to be
treated S.
[0076] Next, an operation, in which the processing device 7
calculates the composition of the in-furnace gas G2 based on the
light receiving result of the light receiving device 6, shall be
described.
[0077] As described above, the in-furnace gas G2 includes the
reaction gas, which is left after the carburizing gas G1 causing
the carburizing reaction in the treatment room 12 and the
non-reaction gas which is not used for the carburizing treatment
and has not caused the carburizing reaction. In the present
embodiment, the in-furnace gas G2 includes hydrogen as the reaction
gas and acetylene as the non-reaction gas.
[0078] In the present embodiment, the gas supply mechanism 3
supplies the predetermined amount of the carburizing gas G1 per
unit time to the treatment room 12. However, in accordance with
various carburizing conditions such as carburizing time,
carburizing temperature, the supply amount of the carburizing gas,
or the like, the amount of the carbon component permeated the
object to be treated S, in other words, a reaction speed of the
carburizing reaction might fluctuate. When the amount of the carbon
component that permeates the object to be treated S changes, the
amount of the reaction gas (hydrogen gas) in the treatment room 12
changes in correspondence therewith.
[0079] Here, carburizing time means elapsed time since the
carburizing treatment started. Carburizing temperature means the
temperature of the treatment room 12, in which the carburizing
treatment is performed. The supply amount of the carburizing gas
means the amount of the carburizing gas G1 supplied per unit time
with respect to the treatment room 12.
[0080] For example, as shown in a schematic view of FIG. 3A, in the
case where carburizing time is short and the amount of the carbon
component at the surface of the object to be treated S (the amount
of carbon already permeated at the surface of the object to be
treated S) is low, there is enough room for the carbon component to
permeate the surface of the object to be treated S. In this case,
from the acetylene supplied to the treatment room 12, most of the
acetylene is used for the carburizing reaction and the amount of
carbon component which permeates the object to be treated S
(reaction speed of the carburizing reaction) increases. In this
case, the gas in the treatment room 12 and the in-furnace gas G2
emitted from the treatment room 12 include a lot of the reaction
gas (hydrogen gas).
[0081] On the other hand, as shown in a schematic view of FIG. 3B,
in a case where the carburizing time is long and the amount of the
carbon component at the surface of the object to be treated S (the
amount of carbon already permeated at the surface of the object to
be treated S) is high, in other words, the amount of carbon
component capable of permeating the surface of the object to be
treated S has almost reached a saturated state, there is little
room for the carbon component to permeate the surface of the object
to be treated S. In this case, from the acetylene supplied to the
treatment room 12, most of the acetylene is not used for the
carburizing reaction and the amount of carbon component which
permeates the object to be treated S (reaction speed of the
carburizing reaction) decreases. In this case, the gas in the
treatment room 12 and the in-furnace gas G2 emitted from the
treatment room 12 include a lot of the non-reaction gas
(acetylene).
[0082] As described above, in accordance with carburizing time, the
composition of the in-furnace gas G2 changes. In accordance with
not only carburizing time, but also with the carburizing conditions
such as carburizing temperature, the amount of the carburizing gas
supplied per unit time to the treatment room 12, or the like, the
composition of the in-furnace gas G2 changes. That is, in
accordance with the carburizing conditions such as carburizing
time, the carburizing temperature, the amount of the carburizing
gas supplied per unit time, or the like, the composition of the
in-furnace gas G2 changes.
[0083] In accordance with the composition of the in-furnace gas G2,
the state of the light changes at the time when the in-furnace gas
G2 inside the light emitting device 5 emits light. In particular,
in accordance with the composition of the in-furnace gas G2, the
light intensity and the emission spectrum change at the time when
the in-furnace gas G2 emits light inside the light emitting device
5. For example, when the in-furnace gas G2, having the composition
shown in FIG. 3A (the composition with a lot of hydrogen), inside
the light emitting device 5 emits light, an emission spectrum
having a peak intensity derived from hydrogen is obtained. Also,
when the in-furnace gas G2, having the composition shown in FIG. 3B
(the composition with a lot of acetylene), emits light inside the
light emitting device 5, the emission spectrum having a peak
intensity derived from acetylene is obtained.
[0084] FIG. 4 is a view showing the emission spectrum developed
based on the light receiving result of the light receiving device
6. In FIG. 4, the horizontal axis represents a wavelength and the
vertical axis represents emission intensity. In FIG. 4, the line L1
shows the emission spectrum when the partial pressure ratio of
hydrogen with respect to the total pressure of the in-furnace gas
G2 (the total pressure of the treatment room 12) is 1. That is, the
line L1 shows the emission spectrum in the case where, from the
acetylene supplied to the treatment room 12, all the acetylene is
used for the carburizing reaction and all the in-furnace gas G2
(the in-furnace gas G2 emitted from the treatment room 12) in the
treatment room 12 is hydrogen gas.
[0085] Also, in FIG. 4, the line 2 shows the emission spectrum when
the partial pressure ratio of hydrogen with respect to the total
pressure of the in-furnace gas G2 (total pressure of the treatment
room 12) is 0.56. That is, the line L2 shows the emission spectrum
in the case where, among acetylene supplied to the treatment room
12, about half the acetylene is used for the carburizing reaction
and about half the in-furnace gas G2 (the in-furnace gas G2 emitted
from the treatment room 12) in the treatment room 12 is hydrogen
gas.
[0086] Also, in FIG. 4, the line L3 shows the emission spectrum
when the partial pressure ratio of hydrogen with respect to the
total pressure of the in-furnace gas G2 (total pressure of the
treatment room 12) is 0. That is, the line L3 shows the emission
spectrum in the case where, among acetylene supplied to the
treatment room 12, all the acetylene is not used for the
carburizing reaction and all the in-furnace gas G2 (the in-furnace
gas G2 emitted from the treatment room 12) in the treatment room 12
is acetylene.
[0087] As described above, in accordance with the composition of
the in-furnace gas G2, the light receiving result of the light
receiving device 6, which receives light emitted from the light
emitting device 5 which emits light by using the in-furnace gas G2,
changes.
[0088] Accordingly, the processing device 7 can calculate the
partial pressure ratio of hydrogen with respect to the total
pressure of the in-furnace gas G2 based on the light receiving
result of the light receiving device 6. Since the partial pressure
ratio of hydrogen with respect to the total pressure of the
in-furnace gas G2 corresponds to the composition of the in-furnace
gas G2, the processing device 7 can calculate the composition of
the in-furnace gas G2 based on the light receiving result of the
light receiving device 6.
[0089] FIG. 5 is plotted with a horizontal axis representing the
partial pressure ratio of hydrogen with respect to the total
pressure of the in-furnace gas G2 and a vertical axis representing
the light receiving result (the peak intensity of a hydrocarbon
derived from acetylene with respect to the peak intensity derived
from hydrogen). Accordingly, it is understood that the composition
of the in-furnace gas G2 and the light receiving result
correlate.
[0090] In the present embodiment, the relationship between the
composition of the in-furnace gas G2 and the light intensity when
the in-furnace gas G2 emits light is stored in advance in the
storage device 9. Here, this relationship can be obtained from, for
example, at least one of a preliminary experiment or a simulation
for example and can be stored in the storage device 9. In the
present embodiment, the relationship between the partial pressure
ratio of hydrogen (or the composition of the in-furnace gas G2)
with respect to the total pressure of the in-furnace gas G2 and
normalized value of light emission intensity corresponding to the
partial pressure ratio (composition), as shown in FIG. 5, is stored
in advance in the storage device 9. Here, for the light emission
intensity, the ratio between the peak intensity derived from
hydrogen and the peak intensity of hydrocarbon derived from
acetylene is preferably used. For a simplified case, the peak
intensity derived from hydrogen may be used.
[0091] The control device 8 controls, by using the adjustment
mechanism 3B, the amount of the carburizing gas G1 supplied per
unit time by the gas supply mechanism 3 based on the composition of
the in-furnace gas G2 which is calculated by the processing device
7.
[0092] It is considered that the carburizing quality of the object
to be treated S (the surface carburizing density, the carburization
density distribution, the case hardness, the effective case depth
after carburizing (carburized depth), or the like) changes
corresponding to the composition of the in-furnace gas G2
(atmosphere of the treatment room 12). In other words, since it is
considered that the carburizing quality of the object to be treated
S and the composition of the in-furnace gas G2 correlate, the
control device 8 adjusts the amount of the carburizing gas G1
supplied per unit time by the gas supply mechanism 3. Here, the
adjustment is performed based on the composition of the in-furnace
gas G2 calculated by the processing device 7 based on the light
receiving result of the light receiving device 6 so as to optimize
the composition (such as acetylene density) of the in-furnace gas
G2, in other words, in order to obtain the composition of the
in-furnace gas G2 in which desired carburizing quality is obtained.
Accordingly, it is possible to obtain a desired state in the
composition of the in-furnace gas G2 and to preferably perform the
vacuum carburizing treatment with high reproducibility.
[0093] Also, as described above, the carburizing condition includes
not only the amount of the carburizing gas G1 supplied per unit
time by the gas supply mechanism 3 but also the carburizing time,
the carburizing temperature, or the like. Accordingly, the control
device 8 can obtain a desired state in the carburizing quality with
respect to the object to be treated S by also adjusting the
carburizing time, the carburizing temperature, or the like as the
carburizing condition based on the calculated composition of the
in-furnace gas G2. Also, the control device 8 may adjust the
composition of the carburizing gas G1, which is supplied to the
treatment room 12 from the gas supply mechanism 3, based on the
calculated composition of the in-furnace gas G2.
[0094] As described above, it is possible to calculate the
composition of the in-furnace gas G2 immediately and accurately in
real time since the composition of the in-furnace gas G2 inside of
the carburizing furnace 2 is calculated optically.
[0095] In the present embodiment, it is possible to calculate the
composition of the in-furnace gas G2 optically and fast (with good
response). Since the structure of the present embodiment can be
made with relatively lower cost compared to a conventional sensor
capable of detecting, for example, the hydrogen density, and is
provided with good sensitivity, it is suitable for a feedback
control and it is possible to improve the controllability
thereof.
[0096] In the present embodiment, the carburizing apparatus is the
vacuum carburizing apparatus and the treatment room 12 of the
carburizing furnace 2 has a high vacuum. Accordingly, it is
possible to make the detection space 15 which is connected to the
treatment room 12 in high vacuum without providing a new (another)
vacuum system for increasing the vacuum of the detection space
(discharge room) 15. Therefore, it is preferable to generate plasma
in the detection space 15 having a high vacuum.
[0097] The detection space 15 and the treatment room 12 of the
carburizing furnace 2 are connected; accordingly it is possible to
make the detection space 15 and the treatment room 12 of the
carburizing furnace 2 have substantially the same environment
(atmosphere). Therefore, it is possible to calculate the
composition of the in-furnace gas G2 accurately since it is
possible to emit light by using the in-furnace gas G2 in the
detection space 15 which has substantially the same environment as
the treatment room 12.
[0098] Based on the calculated composition of the in-furnace gas
G2, among the carburizing conditions, by adjusting in particular
the amount of the carburizing gas G1 supplied per unit time with
respect to the treatment room 12, it is possible to obtain a
desired composition of the in-furnace gas G2. That is, the present
embodiment calculates the composition of the in-furnace gas G2 in
real time by using the light emitting device 5, the light receiving
device 6, the processing device 7, and the like. Based on the
calculated result, it is possible to implement a feedback control
which adjusts the amount of the carburizing gas G1 supplied per
unit time with respect to the treatment room 12 for optimizing the
carburizing condition so as to obtain a desired carburizing
quality. Accordingly, it is preferable to perform the vacuum
carburizing treatment with respect to the object to be treated S
with high reproducibility. Therefore, it is possible to obtain the
object to be treated S with a desired carburizing quality.
[0099] In the present embodiment, it is preferable to control the
carburizing condition to obtain a desired carburizing quality and
so it is possible to perform the treatment with respect to the
object to be treated S with the desired carburizing quality. Also,
in the present embodiment, it is possible to prevent problems such
as generation of the soot in the carburizing furnace or the like
from happening and so it is possible to simplify the maintenance
work of the carburizing furnace.
[0100] In the present embodiment, the light emitting device 5
causes the in-furnace gas G2 to emit light by generating plasma in
the detection space (discharge room) 15 which includes the
in-furnace gas G2, giving energy to the in-furnace gas G2, and
forming the in-furnace gas G2 into an excited state. However, the
light emitting device 5 may be provided with a laser light emitting
device 5L which is capable of emitting a laser light into a
detection room 15' to which the in-furnace gas G2 is introduced as
shown in a schematic view of FIG. 6. The detection room 15' is
connected to the treatment room 12 via the exhaust pipe 4L. The
in-furnace gas G2 is introduced to the detection room 15'. The
detection room 15' is made of a transparent object that transmits
laser light. The light emitting device 5 can cause the in-furnace
gas G2 to emit light by emitting a laser light into the in-furnace
gas G2 from the laser light emitting device 5L and giving energy to
the in-furnace gas G2. That is, since the in-furnace gas G2 becomes
an excited state and emits light by being emitted with a laser, the
light emitting device 5 can emit light by using the in-furnace gas
G2 by also emitting a laser light into the in-furnace gas G2.
[0101] The light emitting device 5 may emit light by using other
methods such as burning the in-furnace gas G2 or the like as long
as it is possible to emit light by giving energy to the in-furnace
gas G2.
[0102] In the above-described embodiment, the space 15 (15') is
branched from the midstream of the exhaust pipe 4L. However, as
shown in FIG. 7, the electrodes 5B for generating plasma may be
disposed in the midstream of the exhaust pipe 4L and the light
generated by plasma may be received by the light receiving device 6
via a transmissive window which is disposed in a predetermined
position of the exhaust pipe 4L. Also, the transmissive window may
be disposed in the midstream of the exhaust pipe 4L and the laser
light may be emitted into the in-furnace gas G2 via the
transmissive window.
[0103] In the present embodiment, the light emitting device 5 emits
light by using the in-furnace gas G2 flowing in the exhaust pipe
4L. However, as shown in FIG. 8 for example, a detection member 5A'
forming an exclusive detection space 115, which is connected to the
treatment room 12 of the carburizing furnace 2, may be provided and
so the light emitting device 5 may emit light by using the
in-furnace gas G2 which is introduced to the detection space
115.
* * * * *