WO2013047762A1

WO2013047762A1 - Cooling device

Info

Publication number: WO2013047762A1
Application number: PCT/JP2012/075110
Authority: WO
Inventors: 隆舩橋; 俊輔竹口
Original assignee: 日本ピストンリング株式会社
Priority date: 2011-09-30
Filing date: 2012-09-28
Publication date: 2013-04-04
Also published as: JP6078000B2; KR101580241B1; KR20140050734A; WO2013046446A1; JPWO2013047762A1

Abstract

The objective of the present invention is to provide a cooling device that is capable of uniform cooling of an article to be processed inserted into a cooling process chamber provided to a continuous sintering furnace. To achieve the objective, a cooling device is adopted that is provided to a continuous furnace that conveys, by means of a plurality of rollers provided in parallel, a plurality of workpieces loaded on a carrying tool stacked in a plurality of stages, and successively subjects the workpieces to a heating process and a cooling processs, wherein the cooling device is provided with: a cooling device that can, in the state of housing the plurality of workpieces, seal/enclose the plurality of workpieces subjected to the heating process; a decompressing device that decompresses the cooling device; a cooling fan that circulates a cooling gas within the cooling device and can adjust the circulation speed thereof; a heat exchanger for cooling the cooling gas; and a graphite sheet that is disposed in a manner so as to enclose the plurality of workpieces within the cooling device.

Description

Cooling system

The present invention relates to a cooling device used in a continuous sintering furnace in which a metal powder is heated and sintered.

Conventionally, a continuous sintering furnace used for sintering a metal powder molded product generally includes a sintering device for sintering a workpiece and a cooling device for cooling the sintered workpiece. I have. Here, in the continuous sintering furnace, the workpieces are sequentially conveyed to these apparatuses to be processed. In the cooling process performed after the sintering process, a cooling gas is introduced into the cooling device, and the cooling gas is circulated by a fan provided in the cooling device to cool the workpiece due to radiant heat loss. It was.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 3-257119) discloses a roller hearth type vacuum furnace that heats an object to be processed in a vacuum state. Specifically, the roller hearth vacuum furnace disclosed in Patent Document 1 is “a roller hearth vacuum furnace in which a cooling device is provided on the outlet side of a heating chamber that heats the workpiece in a vacuum state. A plurality of nozzles for ejecting a cooling gas are provided on the side of the conveyance path, and a rotary table that is rotated around a vertical axis is provided in the cooling device with a conveyance roller for conveying the workpiece on the upper surface. The cooling gas ejected from the nozzle is sprayed on the object to be processed which is transported from the heating chamber and placed on the turntable ”(refer to claim 1). Of that.)

JP-A-3-257119

However, the roller hearth type vacuum furnace according to Patent Document 1 circulates a cooling gas by a fan in a cooling device that accommodates a material to be processed, and performs a cooling process by heat exchange between the cooling gas and the material to be processed. However, when a plurality of objects to be processed are carried into the cooling device for processing, the cooling rate varies depending on the arrangement positions of the objects to be processed. Further, in the roller hearth type vacuum furnace of Patent Document 1, the cooling rate varies even in a portion of the workpiece, and the mechanical characteristics of the product are not stabilized, leading to a reduction in product quality.

In view of the above, an object of the present invention is to provide a cooling device capable of uniforming the cooling rate of the workpiece charged in the cooling treatment chamber provided in the continuous sintering furnace.

Thus, as a result of earnest research, the present inventors have solved the above-mentioned problems by satisfying predetermined conditions for a cooling device used in a continuous sintering furnace that heats and sinters metal powder. Arrived. Hereinafter, the present invention will be described.

The cooling device according to the present invention is a continuous furnace in which a plurality of works loaded on a mounting jig stacked in a plurality of stages are conveyed by a plurality of arranged rollers to sequentially perform a heating process and a cooling process. The cooling device includes a cooling device that can be sealed in a state in which a plurality of heat-treated workpieces are accommodated, a decompression device that depressurizes the cooling device, and circulating a cooling gas in the cooling device. And a cooling fan whose circulation speed can be adjusted, a heat exchanger for cooling the cooling gas, and a graphite plate arranged so as to surround the plurality of workpieces inside the cooling device. Features.

The continuous furnace provided with the cooling device according to the present invention is preferably a roller hearth type continuous furnace or a pusher type continuous furnace.

The continuous furnace provided with the cooling device according to the present invention is preferably used for heat treatment of the internal combustion engine camshaft as the workpiece.

According to the cooling device according to the present invention, the graphite plate is disposed so as to surround all of the plurality of workpieces placed on the jig, so that all of the heat-treated workpieces can be made at a uniform speed. And since it can cool in a short time, the quality improvement of the said workpiece | work and shortening of processing time can be aimed at.

It is the front view illustrated in order to demonstrate the continuous sintering furnace provided with the cooling device which concerns on this invention. FIG. 2 is a cross-sectional view taken along line A-A ′ of FIG. 1. It is explanatory drawing from the front cross section for demonstrating the cooling device of FIG.

The preferred embodiment of the cooling device according to the present invention will be described below in more detail with reference to the drawings.

Cooling device according to the present invention: Provided in a continuous furnace in which a plurality of workpieces loaded on a mounting jig stacked in a plurality of stages are conveyed by a plurality of arranged rollers and heat treatment and cooling treatment are sequentially performed. In the cooling device, the cooling device includes a cooling device that can be sealed in a state where a plurality of heat-treated workpieces are accommodated, a decompression device that depressurizes the cooling device, and circulating a cooling gas in the cooling device. A cooling fan capable of adjusting the circulation speed, a heat exchanger for cooling the cooling gas, and a graphite plate arranged so as to surround the plurality of works inside the cooling device. To do.

FIG. 1 is a front view for explaining a continuous sintering furnace according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. FIG. 3 is a front sectional view for explaining the cooling device of FIG. As illustrated in FIG. 1, a continuous sintering furnace 1 including a cooling device 5 according to the present invention includes a vacuum standby chamber 2, a preheating device 3 that performs dewaxing, a sintering device 4 that performs sintering, and a cooling device. 5 can be configured. The continuous sintering furnace 1 shown in FIG. 1 is configured such that an inlet door 11 for carrying in a workpiece before processing and an outlet door 12 for carrying out the workpiece after processing are driven up and down by opening and

closing devices

13 and 14, respectively. ing. Reference numerals 15 to 20 in the figure also indicate opening / closing devices, respectively, for driving up and down each door (not shown) partitioning each chamber. A transfer roller 21 for transferring the workpiece W is provided over the entire length of the continuous sintering furnace 1.

Here, the conveyance roller 21 has a cylindrical shape, and is disposed in the furnace through the entrance door 11 and the exit door 12 so that the axis of the conveyance roller 21 is horizontal and parallel to the front-rear direction. A plurality of such transport rollers 21 are arranged at the same height and at an interval narrower than the transport direction length of the jig J on which the workpiece W is loaded. Further, each of the transport rollers 21 is supported so as to be rotatable about the axis of the roller. For example, all the rollers can be rotated in the same direction and at the same rotational speed by a chain (not shown) using a motor (not shown) as a power source. The continuous sintering furnace 1 provided with the cooling device 5 according to the present invention places the workpiece W on such a conveyance roller 21 and gradually moves the workpiece W forward by the rotation of the conveyance roller 21. A method of applying a cooling process is adopted.

Here, before explaining the cooling device 5 according to the present invention, a brief description will be given of the treatment applied to the workpiece W in the continuous sintering furnace 1 shown in FIG. First, the workpiece W is carried into the continuous sintering furnace 1 through a carry-in entrance having the entrance door 11 for carrying in the continuous sintering furnace 1. Then, the loaded work W is carried into the preheating chamber 3 by the rotation of the carrying roller 21 serving as a carrying means, and is heated to, for example, 500 to 700 ° C. to evaporate and remove the previously added wax. Then, the workpiece W that has been processed in the preheating device 3 is carried into the sintering device 4 and heated to a sintering temperature of 900 ° C. to 1200 ° C. to be sintered. The workpiece W after the sintering process is finished is cooled by the cooling device 5 and carried out from the outlet door 12 for carrying out.

The preheating device 3 and the sintering device 4 provided in the continuous sintering furnace 1 of the present invention are provided with heat sources (not shown) on the upper, lower, left and right surfaces of the workpiece W. The continuous sintering furnace 1 of the present invention employs a roller hearth type continuous furnace or a pusher type continuous furnace, so that heat from a heat source disposed on the bottom surface between adjacent rollers can be directly transmitted to the workpiece W. . As a result, according to the continuous sintering furnace 1 of the present invention, it is possible to uniformly heat all the workpieces W loaded on the jig J.

In the drawings for explaining the invention of the present specification, a roller hearth type continuous furnace is used to explain the present invention. The roller hearth type continuous furnace is a tunnel-type firing furnace in which the workpiece W loaded on the jig J in the furnace is fired while being transported on a roller and cooled. This roller hearth type continuous furnace has preheating, firing, and cooling temperature zones, and has the advantage of being capable of precise temperature control and excellent mass production efficiency. When this roller hearth-type continuous furnace is used, the workpiece W loaded on the firing jig J is accommodated in the cooling device 5 by the movement of the rotating roller.

A pusher-type continuous furnace (not shown) is a type in which a jig loaded with a plurality of stages of workpieces W is placed on a base plate, and the base plate is moved by a hydraulic pusher to transport the workpiece into the furnace. This is a continuous firing furnace. This pusher type continuous furnace can maintain high airtightness in the furnace compared to the roller hearth type continuous furnace, so it is suitable for atmosphere firing suitable for product specifications such as nitrogen atmosphere, hydrogen reduction atmosphere, etc. The amount of gas can also be reduced. When this pusher-type continuous furnace is used, the plurality of stages of workpieces W loaded on the firing-finished jig are accommodated in the cooling device 5 by moving the base plate with a hydraulic pusher. At this time, by providing a retracting means for pulling a jig loaded with a plurality of stages of workpieces W on the side of the cooling device 5, the jig loaded with a plurality of stages of workpieces W can be easily placed inside the cooling apparatus 5. Can be accommodated.

These roller hearth type continuous furnaces or pusher type continuous furnaces can be used, but it is most preferable to use a roller hearth type continuous furnace. The roller hearth-type continuous furnace is easier to level the furnace temperature than the pusher-type continuous furnace in which a plurality of stages of workpieces W are loaded on a jig, and the workpiece W accommodated in the furnace This is because the variation in heating is less likely to occur. Therefore, in the following description, a roller hearth type continuous furnace will be described with reference to the drawings.

Next, the cooling device 5 according to the present invention will be described below. As shown in FIGS. 2 and 3, the cooling device 5 according to the present invention has a configuration in which a loading door 59 for loading the workpiece W and an outlet door 12 illustrated in FIG. 1 for unloading the workpiece W are opened and closed. It has a structure that can close the inside of the cooling device 5 by closing the door. The cooling device 5 of the present invention can uniformly cool all the plurality of workpieces W loaded on the jig J by performing cooling in a state where the inside is pressurized. Incidentally, the cooling device 5 according to the present invention is connected via a pressurizing device (not shown) that pressurizes the inside of the cooling processing chamber 52, and during the cooling processing, the pressure in the cooling processing chamber 52 is a predetermined value of about 1500 TORR. It is possible to control the pressurization up to the pressure. When the cooling gas is agitated (circulated) during cooling, the cooling process chamber 52 is pressurized to reduce the difference in cooling rate at each location of the circulating cooling gas compared to the atmospheric pressure state. It can be made. By utilizing the effect of the pressurization in the cooling processing chamber 52, it is possible to suppress the occurrence of distortion even in the workpiece W where the cooling distortion is likely to occur, and the cooling process while maintaining high dimensional accuracy. Can be done.

Moreover, since the cooling device 5 according to the present invention has a structure in which the graphite plate 51 is provided so as to surround all the workpieces W loaded on the jig J, the heat insulating action by the graphite plate 51 during the cooling process, In addition, the work can be cooled at a uniform speed without any individual difference without being affected by the placement position of the work W on the jig J by the heat radiation action. Further, the cooling device 5 according to the present invention has the graphite plate 51 disposed therein, so that the cooling gas does not directly contact the workpiece W disposed in the cooling processing chamber 52, and the workpiece W is Even in the case of rapid cooling, it is possible to cool at a uniform speed.

As described above, the cooling device 5 according to the present invention is provided with the graphite plate 51 so as to surround all the workpieces W loaded on the jig J, and a system for performing the cooling process in this state is provided. Adopted. Here, the graphite refers to a lump of carbon that can be formed by high-temperature heat treatment called graphitization. The graphite material is porous, and the air existing inside absorbs heat and functions as a heat insulating material. Also, the graphite itself has a good thermal conductivity (high thermal conductivity), so it can be used for heat dissipation and cooling. It can also be suitably used for a floor board or the like. That is, the graphite plate 51 that surrounds the workpiece W in the cooling device 5 of the present invention also acts as a heat storage body, can prevent partial overcooling of the workpiece W, and from the workpiece W by the temperature rise of the graphite plate itself. By suppressing the heat radiation, the temperature difference due to the arrangement position of the workpiece W can be reduced. As a result, according to the cooling device 5 of the present invention, it is possible to cool all the workpieces W in the cooling chamber 52 at a uniform speed, resulting in variations in mechanical characteristics in the portions of the workpieces W and products. There is no loss of quality. Incidentally, since the graphite plate is porous and air permeable, it is considered that these effects can be obtained. In view of this point, a porous ceramic plate having excellent thermal conductivity can be used instead. I can do it.

Further, as shown in FIG. 2, the cooling device 5 according to the present invention has a fan 53 provided therein and is rotated by a motor stored in the fan driving device M, thereby introducing a cooling gas (not shown). The cooling gas introduced from the mouth can be circulated in the cooling processing chamber 52. Further, in the cooling device 5 according to the present invention, the heat exchanger 55 that distributes the heat introduced from the refrigerant introduction pipe 56 and exchanges heat, and leads the heat through the refrigerant lead-out pipe 57 can be installed in the cooling processing chamber 52. . When the cooling device 5 of the present invention has such a structure, the cooling device or cooling air circulating in the cooling processing chamber 52 is cooled each time it contacts the heat exchanger 55 and can be rapidly cooled. Further, a rectifying plate 58 is provided in the cooling processing chamber 52 for efficiently convectively circulating the introduced cooling gas. The fan 53 can change the circulation speed when the cooling gas is circulated. For example, the fan 53 can be controlled between a state where the fan speed is 0 Hz, which is a state where the cooling gas is not circulated, and a state where the fan speed is 20 Hz to 60 Hz. Therefore, according to the cooling device according to the present invention, the cooling process speed of the workpiece W can be improved by optimizing the combination of the pressure state in the cooling process chamber 52 and the fan rotation speed condition. The desired mechanical characteristics can be stably imparted to the workpiece W. In FIG. 2, the fan 53 is configured and arranged to send the cooling gas from the side, but is not limited to this position. Moreover, what pressurized nitrogen, argon, helium etc. can be used for the cooling gas used at the cooling treatment process of this invention, for example.

Since the cooling device 5 according to the present invention has the above-described structure, it is possible to obtain both an excellent cooling strain suppression effect and a cooling efficiency improvement effect in a temperature region where the possibility of occurrence of cooling strain is low. After the work W is cooled, for example, nitrogen gas is introduced into the cooling device 5 to restore the pressure to atmospheric pressure, and then the outlet door 12 on the carry-out side is opened and the transport roller 21 is rotated. By doing so, the workpiece W can be carried out from the cooling device 5.

3 shows a plurality of workpieces W stacked and placed in a plurality of stages. According to the cooling device 5 of the present invention, the workpiece W can be uniformly cooled regardless of the placement position of the workpiece W. It becomes possible, and generation | occurrence | production of inferior goods can be suppressed by performing uniform cooling of the workpiece | work W reliably.

Further, according to the cooling device 5 according to the present invention, the cooling processing time can be significantly shortened as compared with the conventional case. Therefore, among the devices constituting the continuous sintering furnace 1, the processing time is relatively long. Processing can be performed in parallel with the short preheating device 3 and the sintering device 4. Therefore, according to the continuous sintering furnace 1 provided with the cooling device 5 according to the present invention, the processing can be performed very efficiently. In other words, the continuous sintering furnace 1 includes the cooling device according to the present invention, so that the workpiece W is moved by the transport roller 21 so as to sequentially move the processing devices 2 to 5 (in the direction of the arrow shown in FIG. 1). It is possible to move the workpiece W efficiently when making it.

In the cooling device according to the present invention, the work is preferably a camshaft for an internal combustion engine.

Camshafts for internal combustion engines that are used under severe sliding conditions have higher wear resistance than conventional models, and are light weight that can withstand high surface pressures and loads as the internal combustion engines become more powerful and have higher output. There is a need for a camshaft. Specifically, a camshaft for an internal combustion engine is required to have excellent wear characteristics such as pitting resistance and scuffing resistance that can withstand severe sliding conditions under high engine speed and high contact surface pressure. . In order to meet these requirements, a camshaft for an internal combustion engine is a so-called sintered camshaft in which a sintered cam lobe is joined to a steel shaft, and the cooling speed of the camshaft is increased in the cooling process after sintering. Control is required so that the entire circumference is uniform.

Here, since the cooling device 5 according to the present invention has a structure in which the arranged graphite plate surrounds the camshaft, the camshaft can be cooled at a uniform speed without unevenness. Further, in the cooling device according to the present invention, the above-mentioned characteristics required for the camshaft are stably imparted in a short time by an optimal combination of the pressure state in the cooling processing chamber 52 and the fan rotational speed condition. It will be possible. For example, in the cooling process of the sintered camshaft, after the sintering process is completed, first, the cooling in the cooling process chamber 52 is performed at a pressure of 760 torr and the fan rotational speed is 0 Hz to 20 Hz for a predetermined time (first slow cooling mode). Next, cooling is performed for a predetermined time (second slow cooling mode) in a state where the pressure in the cooling processing chamber 52 is 910 torr and the fan rotational speed is 20 Hz to 30 Hz, and then the fan is heated in the cooling processing chamber 52 at 1500 torr. Cooling mode conditions can be set such that cooling is performed for a predetermined time (rapid cooling mode) at a rotational speed of 30 Hz to 60 Hz. Thus, according to the cooling device according to the present invention, a cooling rate of the sintered camshaft A ₁ can also be varied cut before and after the temperature near the transformation point, pitting resistance and the scuffing resistance, etc. A sintered camshaft excellent in wear characteristics can be provided stably in a short time.

For reference, the heat treatment and cooling treatment of the sintered camshaft is performed at once in a state where, for example, a plurality of placement plates stacked in a horizontal and horizontal manner are stacked in order to improve the processing efficiency. (See Work W in FIG. 3). Therefore, the temperature difference between the camshafts is likely to occur depending on the position where the camshaft is placed, and it is necessary to uniformly heat and cool the entire circumference of the camshaft during the heat treatment and the cooling treatment. According to the continuous sintering furnace 1 of the present invention, as described above, a heat source can be arranged on the bottom surface side in the heat treatment, and a graphite plate can be arranged on the bottom surface side in the cooling treatment as well. Therefore, the temperature of the camshaft can be controlled without individual differences.

The cooling device according to the present invention has a configuration in which a plurality of workpieces are surrounded and a graphite plate is disposed, so that all the workpieces can be cooled in a short time and at a uniform speed. Therefore, according to the cooling device according to the present invention, it is possible to improve the quality of the workpiece and shorten the processing time, and to reduce the manufacturing cost. From the above, the cooling device according to the present invention can be suitably used for other sliding elements used in, for example, an internal combustion engine, which require high quality and high mechanical strength.

DESCRIPTION OF SYMBOLS 1 Continuous sintering furnace 2 Standby chamber 3 Preheating apparatus 4 Sintering apparatus 5 Cooling apparatus 21 Conveying roller 11 Inlet door 12 Outlet door 51 Graphite plate 52 Cooling processing chamber 53 Fan 54 Wind collection induction duct 55 Heat exchanger 56 Refrigerant introduction Pipe 57 Refrigerant outlet pipe 58 Rectifier plate 59 Carry-in door J Jig M Fan drive motor device W Work (camshaft)

Claims

In a cooling device provided in a continuous furnace in which a plurality of workpieces loaded on a mounting jig stacked in a plurality of stages are conveyed by a plurality of rollers arranged in parallel and sequentially subjected to heat treatment and cooling treatment,
The cooling device is a cooling device that can be sealed in a state in which a plurality of heat-treated workpieces are accommodated, and
A decompression device for decompressing the cooling device;
A cooling fan that circulates the cooling gas in the cooling device and adjusts the circulation speed;
A heat exchanger for cooling the cooling gas;
A cooling device comprising a graphite plate disposed so as to surround the plurality of workpieces inside the cooling device.
The cooling device according to claim 1, wherein the continuous furnace is a roller hearth type continuous furnace or a pusher type continuous furnace.
The cooling device according to claim 1, wherein the workpiece is a camshaft for an internal combustion engine.