CN113059139A

CN113059139A - Brake drum heating device and heating process

Info

Publication number: CN113059139A
Application number: CN202110403254.8A
Authority: CN
Inventors: 林强盛; 张建荣
Original assignee: JIAXING STONE WHEEL CO Ltd
Current assignee: JIAXING STONE WHEEL CO Ltd
Priority date: 2021-04-15
Filing date: 2021-04-15
Publication date: 2021-07-02

Abstract

The invention discloses a brake drum heating device which comprises at least one heating station and two or more groups of moving workpiece conveying devices. The heating station is provided with a heating coil, the movable workpiece conveying device is provided with a brake drum positioning mechanism, and the workpieces can be alternately and circularly transferred to the heating station for heating. The specific structure can be a three-station heating device, and the three-station heating device further comprises a feeding station and a preheating station, wherein the preheating station is provided with a preheating coil, and the feeding station, the preheating station and the heating station are fixed stations. The three groups of moving workpiece conveying devices respectively move the corresponding feeding station, the preheating station and the heating station which are alternately circulated, and convey the workpieces to the preheating station and the heating station alternately and circularly. The heating process is completed through the processes of feeding, descending and rotating, ascending preheating, descending and rotating, ascending heating, material taking and the like. The three groups of workpiece conveying devices respectively and alternately complete the processes, the assembly line operation is realized, and the production efficiency is improved.

Description

Brake drum heating device and heating process

Technical Field

The invention relates to a workpiece heating device, in particular to a heating device in the preparation and maintenance process of a metal brake drum, and also relates to a heating process of the heating device.

Background

In the manufacturing and repairing processes of the metal brake drum, the brake drum or a semi-finished brake drum shell needs to be heated, and a commonly used heating device at present is medium-frequency electromagnetic heating. A workpiece to be heated is placed in the medium-frequency induction coil, and after the workpiece is electrified, the function of heating by temperature rise is realized through eddy current generated by electromagnetic induction.

For example, in the manufacture of bimetallic brake drums, it is necessary to heat a brake drum shell of steel material to a temperature above 700 c, and even up to 1200 c, in order to facilitate the centrifugal casting of a friction layer of grey cast iron within the steel shell. Heating and warming up of the brake drum shell is a key necessary process for manufacturing the bimetal brake drum, and the steel brake drum shell is placed in the medium-frequency induction coil and heated through electromagnetic induction. However, the heating of the shell of the existing brake drum is still in a monomer heating state, and the production efficiency is low. In order to improve the production efficiency, assembly line operation is adopted in some cases, namely, a plurality of sets of electromagnetic induction heating devices are arranged for circulating assembly line heating. The method needs to be provided with a plurality of sets of heating systems and a plurality of sets of independent heating control devices, and the plurality of sets of heating control devices still need to be respectively and independently controlled when in cyclic heating. Different workpieces need to be heated in different heating devices, so that the heating effects of the different workpieces are not completely consistent, the heating temperature difference is generated, and the casting quality of the brake drum is influenced. The heating system which needs a plurality of sets of control devices and a plurality of sets of heating devices has the defects of complex structure and high operation and maintenance cost.

In the prior art, a heating device is combined with a brake drum centrifugal casting line, as shown in fig. 7, a single heating device is arranged on a multi-station centrifugal casting machine to heat each brake drum shell entering the line. The electromagnetic heating coil shown in the figure is required to reciprocate, and a brake drum shell on the centrifuge is sleeved in the heating coil through reciprocating motion. The multi-station centrifugal casting machine using the heating device needs to be provided with at least one feeding station, one heating station and one casting station, otherwise, the assembly line operation cannot be realized. The heating device needs to occupy a certain station, and the produced defects are that the assembly line runs slowly and the production efficiency is difficult to improve. Meanwhile, the heating station is single, only heating can be performed, the preheating function is not available, the heating effect of a wave-shaped shell or shells with different thicknesses is not uniform during heating, the temperature rise of different parts of the brake drum shell is not uniform, and the casting quality is further influenced.

In view of the above, the present inventors have invented a brake drum heating device, and developed a brake drum heating process of such a device, which can not only achieve pipelined brake drum heating, but also ensure uniform and consistent heating effect and high production efficiency.

Disclosure of Invention

The invention aims to provide a brake drum heating device which can realize rapid and uniform heating of a brake drum or a brake drum shell.

Another object of the present invention is to provide a heating process for use in the above heating apparatus.

The brake drum heating device comprises at least one heating station and two or more groups of workpiece conveying devices; the heating station is provided with a heating coil, the workpiece conveying device is provided with a workpiece positioning mechanism, and the two or more groups of workpiece conveying devices can convey the workpieces to the heating coil of the heating station in an alternate circulating mode.

In the brake drum heating device, the brake drum heating device further comprises a feeding station and a preheating station, and the preheating station is provided with a preheating coil; the feeding station, the preheating station and the heating station are fixedly arranged; the workpiece conveying devices are in three groups, can move to correspond to the feeding station, the preheating station and the heating station in an alternate circulating mode respectively, and convey the workpieces to the preheating coil of the preheating station and the heating coil of the heating station in an alternate circulating mode.

In the brake drum heating device, the feeding station, the preheating station and the heating station are arranged on a fixed disc in the same plane, in the same center, in the same diameter and in the same radian; the workpiece conveying device is arranged on a rotating disc in the same plane, concentric, equal-diameter and equal-radian mode; the fixed disc and the rotating disc are coaxially and horizontally arranged in parallel, and the rotating disc is provided with a rotating device and a lifting device.

In the brake drum heating device, the rotating disc rotates to enable the workpiece conveying device to alternately and circularly vertically correspond to the feeding station, the preheating station and the heating station; the rotating disc realizes that the workpiece conveying device is alternately and circularly positioned at the feeding station, the preheating station and the heating station through the lifting device. The rotating disc is provided with a rotating device, and the workpiece conveying device is provided with a lifting device.

In the brake drum heating device, the rotating disc rotates to enable the workpiece conveying device to alternately and circularly vertically correspond to the feeding station, the preheating station and the heating station; the workpiece conveying device is positioned at the feeding station, the preheating station and the heating station in an alternate and cyclic mode through the lifting device.

In the brake drum heating device, the workpiece conveying device is provided with a rotation device, and the workpiece conveying device drives the workpiece to rotate when the workpiece is preheated or heated.

The brake drum heating process of the brake drum heating device comprises the following steps:

first-step feeding: when the rotating disc is horizontally high, the workpiece is fixed on a workpiece conveying device of the feeding station;

the second step is descending and rotating: the rotating disc descends to a horizontal low position and rotates by 120 degrees until the workpiece conveying device is arranged below the preheating station;

third step, ascending preheating: the rotating disc rises to a horizontal high position, and the workpiece is placed in a preheating station preheating coil for preheating;

the fourth step is descending and rotating: the rotating disc descends to a horizontal low position and rotates by 120 degrees until the workpiece conveying device is arranged below the heating station correspondingly;

fifthly, ascending heating: the rotating disc rises to a horizontal high position, and the workpiece is placed in a heating station heating device for heating;

sixth, material taking: taking down the workpiece to finish the heating process; the rotating disc continues to rotate to enter the next working procedure.

In the heating process, when the workpiece conveying device preheats and heats the workpiece at the preheating station and the heating station, the subsequent workpiece conveying devices are respectively positioned at the feeding station and the preheating station to carry out workpiece feeding and workpiece preheating, and the workpiece conveying devices in the preorder are respectively positioned at the heating station and the feeding station to carry out workpiece heating and workpiece feeding; when the workpiece is preheated in the preheating coil and heated in the heating coil, the workpiece conveying device is provided with a rotation device which drives the workpiece to rotate.

first-step feeding: when the workpiece conveying device is positioned at the horizontal high position of the feeding station, the workpiece is fixed on the workpiece transferring device;

the second step is descending and rotating: the workpiece conveying device descends to a horizontal low position, and the rotating disc rotates by 120 degrees until the workpiece conveying device is arranged below the preheating station;

third step, ascending preheating: the workpiece conveying device rises to a horizontal high position when rotating to a preheating station, and the workpiece is preheated in a preheating coil;

the fourth step is descending and rotating: the workpiece conveying device descends to a horizontal low position, and the rotating disc rotates by 120 degrees until the workpiece conveying device is arranged below the heating station correspondingly;

fifthly, ascending heating: the workpiece conveying device rises to a horizontal high position when rotating to a heating station, and the workpiece is positioned in a heating coil for heating;

The brake drum heating device can realize preheating and heating only by using the same set of preheating coil and heating coil, and further can completely achieve uniform heating effect under the condition that the set of heating device runs stably and workpieces are uniform, so that the heating temperature of the shell of the brake drum is effectively ensured to be uniform. Meanwhile, the heating coil and the preheating coil can be fixedly arranged, so that the problems of complex structure and high maintenance cost of the heating device are avoided. The brake drum heating device who sets up alone breaks away from heating device from centrifugal casting machine, avoids heating device to occupy the station on the centrifugal casting machine, can improve casting efficiency.

The heating device of the invention can completely realize mechanized flow line production by combining with the heating process of the invention, thereby improving the production efficiency.

Drawings

FIG. 1 is a schematic side view of a brake drum heating apparatus according to embodiment 1 of the present invention;

fig. 2 is a schematic top view of the brake drum heating apparatus according to embodiment 1 of the present invention;

FIG. 3 is a schematic perspective view of a brake drum heating apparatus according to embodiment 1 of the present invention in a horizontally elevated position;

FIG. 4 is a schematic perspective view of a brake drum heating apparatus according to embodiment 1 of the present invention in a horizontally lowered position;

FIG. 5 is a sectional view showing a brake drum in a preheating state according to embodiment 1 of the present invention;

FIG. 6 is a schematic sectional view showing a heated state of a brake drum according to embodiment 1 of the present invention;

FIG. 7 is a schematic view of a heating device on a centrifugal casting machine of the prior art;

fig. 8 is a flow chart of a heating process of the heating apparatus of example 1 of the present invention.

Shown in the figure: 1 is a fixed disc; 11 is a feeding station; 12 is a preheating station; 13 is a heating station; 121 is a preheating coil; 122 is a preheating coil frame; 131 is a heating coil; 132 is a heating coil frame;

2 is a rotating disc; 21. 22, 23 are workpiece conveying devices; 221 is a rotation device; 25 is a lifting device; 26 is a rotating device; 27 is a fixed bracket; 28 is a rotating shaft;

31. 32 and 33 are brake drum shell workpieces; 321 is a thicker portion.

Detailed Description

The brake drum heating device and the heating process of the present invention will be described in detail with reference to the accompanying drawings and specific embodiments, which are used for illustration of the technical solutions and are not intended to limit the protection scope.

Example 1:

as shown in fig. 1 and 2, the present embodiment is described with a three-position brake drum heating device. The three-position brake drum heating device of the embodiment comprises a fixed part and a rotating part, wherein the fixed part and the rotating part are arranged coaxially.

The fixing part comprises a horizontally arranged fixing disc 1, and three fixing stations, namely a feeding station 11, a preheating station 12 and a heating station 13, are arranged on the fixing disc 1. The three fixed stations are annularly arranged in the same radius and equal radian by taking the center of the fixed disk 1 as the circle center, and the radians among the three stations are all 120 degrees.

The feeding station 11 does not need a special structure, and is an opening formed in the fixed disc 1, and the opening has a size which ensures that the workpiece brake drum passes through. The preheating station 12 is also provided with an opening which is the same as the loading station 11, a preheating coil 121 is arranged at the position of the opening, the preheating coil 121 is fixed on a preheating coil frame 122, the preheating coil frame 122 is also provided with a power supply device to ensure that the preheating coil 121 is fixedly arranged on the preheating station 12, and the power supply device is arranged to provide preheating power for the preheating coil 121. As shown in fig. 5, the preheating coil 121 is only disposed at a portion that needs to be preheated, such as a portion that needs to be heated when casting or a portion that needs to be heated when casting on the preheating brake drum shell workpiece 32, where 321 is shown as a portion that needs to be heated when casting and is thick on the brake drum shell, and such a portion may be heated slowly when heating, which affects the heating speed. Since only partial preheating is performed, the number of turns of the preheating coil 121 can be small and the power can be low. The purpose of preheating is to ensure that the heating speed is as uniform as possible with the temperature of each part after heating is finished, or the temperature of the thicker part is higher.

The heating station 13 is also provided with a hole similar to the feeding station 11, and a heating coil 131 is provided. Since the purpose of the heating station is to heat up the entire surface, as shown in fig. 6, it is necessary to distribute heating coils 131 over the entire part of the barrel portion of the workpiece 33 for heating the brake drum housing for rapid warming of the brake drum. The heating coil 131 is fixedly provided on the heating coil frame 132, and the heating coil frame 132 is fixedly provided on the fixed tray 1. The power of the heating coil 131 is also supplied collectively by the power supply device. The heating coil 131 has a large heating power and a large number of turns.

Therefore, a preheating station and a preheating coil are required to be arranged, so that the problem that when a single heating device is used for heating the brake drum shell, the brake drum shell with a wave-shaped structure generates wave temperature difference or thickness temperature difference caused by different casting layer thicknesses and different brake drum shell thicknesses is solved.

The structure realizes that the heating coil and the preheating coil are separately and fixedly arranged, the heating coil does not need to move along with the movement of a brake drum assembly line, and then a complex wiring structure can be avoided.

The rotating part of the heating device of the embodiment is provided with a rotating disk 2, the rotating disk 2 is arranged below the fixed disk 1 and is also horizontally arranged and parallel to the fixed disk 1, and the axis of the rotating disk 2 is superposed with the axis of the fixed disk 2. The rotary plate 2 is provided with a rotary shaft 28 at the axis to achieve horizontal rotation of the rotary plate 2 itself, herein referred to as revolution of the rotary plate 2. The rotary disk 2 also corresponds to the fixed disk 1, and three groups of moving

workpiece conveying devices

21, 22 and 23 are arranged in an annular arrangement with the same radius and equal radian by taking the axis as the center of a circle, and the radians among the three groups of workpiece conveying devices are all 120 degrees. Through the rotation of the rotating disc 2, three groups of workpiece conveying devices can be positioned below the fixed disc 1 and respectively and circularly vertically correspond to the feeding station 11, the preheating station 12 and the heating station 13.

As shown in fig. 1 and 2, three sets of workpiece conveying devices are provided on the rotary table 2, and each of the workpiece conveying devices itself is also provided with a horizontal turning device, such as the horizontal turning device 221 provided in the workpiece conveying device 22 in the present embodiment. The structure of the other workpiece transport devices is identical to that of the workpiece transport device 22. This structure makes it possible to horizontally rotate the workpiece conveying device itself about its own rotation axis, which is called rotation.

The rotating disc 2 is provided with a rotating shaft 28, the rotating disc 2 can rotate around the rotating shaft 28, and the rotating device 26 is also provided, the rotating shaft 28 is arranged on a fixed bracket 27, and the fixed bracket 27 is used as a supporting structure of a moving part in the device of the embodiment. Meanwhile, the rotating disc 2 is also provided with a lifting device 25, the lifting device 25 can drive the rotating disc 2 to do lifting reciprocating motion, so that the rotating disc 2 can ascend and descend, the vertical distance between the rotating disc 2 and the fixed disc 1 can be changed, and the state conversion of the rotating disc 2 between a horizontal high position and a horizontal low position can be realized.

As shown in fig. 4, when the rotary disk 2 is in the horizontally high position, three sets of

workpiece conveyers

21, 22, and 23 may be positioned at the loading station 11, the preheating station 12, and the heating station 13, respectively. The workpiece transport device 21, which is now located at the loading station 11, is used to receive the brake drum housing workpiece 31 to be heated, which is transported by the robot and to position it on this transport device 21. The workpiece transport device 22 at the preheating station 12 is used to place the positioned preheating brake drum housing workpiece 32 within the preheating coil 121 for workpiece preheating. The workpiece transport device 23 at the heating station 13 is used to place the positioned heated brake drum housing workpiece 33 in the heating coil 131 for heating and warming. However, the above is only a specific state in one working cycle, and since the rotary disk 2 is rotated, the relationship between the workpiece conveyor and the fixed station is dynamically changed alternately and cyclically.

As shown in fig. 3, when the rotary plate 2 is located at a horizontal low position, the workpiece conveying device moves downward along with the rotary plate 2 to separate from the fixed station on the fixed plate 1, and then the rotary plate 2 is rotated by an angle of 2 to 120 degrees, and after the corresponding relationship between the workpiece conveying device and the fixed station is changed, the rotary plate 2 is lifted again, so that the workpiece conveying device and the fixed station can be cyclically and alternately changed, and the assembly line operation can be realized.

The workpiece conveying devices are respectively provided with the rotation devices, so that the rotation of the workpiece conveying devices can be realized, the rotation of the workpiece conveying devices can realize the rotation of the brake drums in the preheating station 12 and the heating station 13, and the preheating and the heating are more uniform.

This is true of the plant heating process run of this example 1. The heating process performed by one brake drum casing is described as one cycle.

First, in the initial state, the rotary table 2 is in the horizontally low position, as shown in fig. 3, and the overheated workpiece brake drum housing workpieces 32 and the heated workpiece 33 are respectively fixed to the two sets of

workpiece transfer devices

22 and 23 on the rotary table 2. The workpiece conveyor 11 corresponding to the loading station 11 is in an empty state.

When the device is started, the first step is started, the lifting device 25 of the rotating disk 2 operates firstly to lift the rotating disk 2 to a horizontal high position, and the three groups of

workpiece transfer devices

21, 22 and 23 are respectively positioned at the loading station 11, the preheating station 12 and the heating station 13 which reach the fixed disk. I.e. the state shown in fig. 4.

The second step is that the robot arm conveys the opening of the brake drum shell workpiece 31 upwards to the loading station 11, and places the brake drum shell workpiece on the workpiece transfer device 21 positioned at the loading station 11, and at this time, the workpiece transfer device is assumed to be 21, and actually, the brake drum shell workpiece is changed alternately. Meanwhile, the

workpiece transfer devices

22 and 23 are respectively arranged at the preheating station 12 and the heating station 13, the preheating brake drum shell workpiece 32 is sent into the preheating coil 121 by the conveying device 22 for preheating, the heating brake drum shell workpiece 33 is sent into the heating coil 131 for heating by the conveying device 23, the discharging operation is carried out after the heating is finished, and the workpiece conveying device 23 is in an empty state.

The third action is that the rotating disc lifting device 25 operates to lower the rotating disc 2 to a horizontal low position. Returning to the state shown in figure 3.

The fourth step is to rotate the rotary disk 2 by 120 degrees by operating the rotary disk rotating device 26, thereby changing the correspondence between the workpiece conveying device and the fixed station. The workpiece transport device 21, on which the brake drum housing workpiece 31 is placed at this time, is moved to a vertical position corresponding to the preheating station 12, while the

other transport devices

22 and 23 vertically correspond to the heating station 13 and the loading station 11 of the fixed platter 1, respectively, with the transport device 23 in an empty state.

The fifth operation is to move the rotary 2 elevating device 25 again to raise the rotary 2 to the horizontal high position. The conveyor 21 for placing the brake drum shell workpiece 31 is positioned at the preheating station 12, the conveyor 22 is positioned at the heating station 13, and the conveyor 23 is positioned at the loading station 11 and is vacant. At this time, the brake drum housing workpiece 31 becomes a preheating workpiece to be preheated, and the original preheating workpiece 32 becomes a heating workpiece to be heated. The conveyor 23 is already in position at the loading station 11, and the robot then places the subsequent brake drum shell on the conveyor 23.

The sixth operation is to start the rotation device 221 of the workpiece transfer device 21 to rotate it, and to turn on the intermediate frequency power supply to the preheating coil 121 to preheat the workpiece 31 located therein. Meanwhile, the required action is that the mechanical arm conveys the brake drum shell workpiece to the feeding station 11 again and places the brake drum shell workpiece on the workpiece transfer device 23 for positioning, and secondary feeding is completed.

The seventh operation is to operate the rotary disk lifter 25 again to lower the rotary disk 2 to the horizontal low position again.

And the eighth step is that the rotating disc rotates 120 degrees again, and the corresponding relation between the workpiece conveying device and the fixed station is changed. The workpiece transfer device 21 is rotated together with the brake drum housing workpiece 31 to a position vertically corresponding to the heating station 13. The transport device 23 for placing the brake drum housing is located vertically opposite the preheating station 12, and the transport device 22 without the brake drum housing is located vertically opposite the loading station 11.

The ninth operation is to raise the rotary table 2 to the horizontal high position again, and at this time, the workpiece transfer device 21 and the brake drum housing workpiece 31 are positioned in the heating coil 131 of the heating station 23, and are heated by energization, and the workpiece conveying device 221 rotates while heating, thereby achieving uniform heating. The brake drum housing work 33 of the work transfer device 23 is positioned in the preheating coil 121 of the preheating station 22, and rotates while being preheated. The workpiece transfer device 22 is located in the loading station 11 and simultaneously receives the third workpiece brake drum conveyed by the robot.

The tenth action is that the workpiece transfer device 21 and the brake drum shell workpiece 31 stop rotating after being heated to a preset temperature, and the heated workpiece brake drum is taken away by the manipulator to complete a complete heating process. The rotating disc 2 is then lowered again into the next cycle.

The above-mentioned process is through three promotion three-drop and the cubic of rotary disk 2 and is rotated, accomplish three brake drum shell and take one's place the placing, preheat and the three process of heating, and then can realize rotatory circulation operation, can promote the production efficiency in the unit interval, simultaneously because the heating device who preheats station 12 and heating station 13 is fixed, it is relatively simple to set up operating condition parameter, the heating of each work piece is all preheated at same preheating station, heat at same heating station, under the unanimous prerequisite of work piece, realize the even unanimity of heating effect.

The rotation device 221 provided in the workpiece conveying device is not rotated at the time of workpiece loading and unloading, and ensures stable operation of the robot.

Example 2:

the structure of the present embodiment is basically the same as that of embodiment 1, except that the elevating device 25 is not provided in the rotary plate 2 itself, and the rotary plate 2 itself does not perform the elevating operation. Instead, the workpiece transfer devices are provided with lifting devices, so that each group of workpiece transfer devices can realize independent lifting action. The rotation of the rotating disc and the independent lifting of the workpiece transfer device are used for realizing the function of circularly positioning the workpiece transfer device, and the technical process is realized.

Example 3:

the above-described embodiment can also be simplified to a configuration having only two fixed stations and two sets of workpiece transfer devices. The preheating station 12 is not arranged on the fixed disc 1 any more, and only the feeding station 11 and the heating station 13 are arranged. After the feeding at the feeding station 11 is completed, the rotating disc 2 descends and rotates to the heating station 13 again, and then ascends and directly enters the heating station 13 for heating. Thus, the heating device is a two-station heating device. The purpose of alternate heating line production can be realized by only realizing twice lifting and rotating in operation. The two-station heating device of the embodiment heats directly from the feeding temperature, and the time for using the two-station heating device is probably longer, but the two-station heating device can also be more suitable for workpieces made of certain materials, such as brake drum shells without wave structures and the same thickness.

Example 4:

this embodiment can be further simplified on the basis of embodiment 3, and can also realize the basic functions of the present invention. If no dedicated holding pan 1 is provided, only a heating station with heating coils 131 is provided. Because material loading station 11 need not other special construction, does not set up the station alone, directly with the manipulator with the work piece brake drum transport to work piece conveyor can. And after the workpieces are placed in the two groups of workpiece conveying devices, the workpieces are alternately conveyed to the heating station 13 for heating.

Example 5:

this embodiment can be further simplified on the basis of embodiment 3, and two fixing stations and two sets of workpiece conveying devices are provided. A special feeding station is not arranged any more, the feeding station and the preheating station are integrated into one station, two steps of operation of feeding and preheating are carried out at the station, and the operation of heating and discharging is carried out at the other station.

The heating device can be manufactured into a four-station, five-station or even six-station structure, namely, a heating step can be added when each station is added, the heating effect of the brake drum can be more favorable when the heating step is smaller, but operation steps are required to be added after the stations are added, if the stations are six, the rotating disc is required to be lifted for six times to complete a cycle, and six workpieces can be heated in one cycle.

In summary, the structure of the present invention should not be limited to the above-mentioned embodiments, and modifications made by those skilled in the art on the basis of the present invention without departing from the basic idea of the present invention should fall within the protection scope of the present invention.

Claims

1. A brake drum heating apparatus characterized by: comprises at least one heating station and two or more groups of workpiece conveying devices; the heating station is provided with a heating coil, the workpiece conveying device is provided with a workpiece positioning mechanism, and the two or more groups of workpiece conveying devices can convey the workpieces to the heating coil of the heating station in an alternate circulating mode.

2. The brake drum heating apparatus according to claim 1, wherein: the brake drum heating device further comprises a feeding station and a preheating station, and the preheating station is provided with a preheating coil; the feeding station, the preheating station and the heating station are fixedly arranged; the workpiece conveying devices are in three groups, can move to correspond to the feeding station, the preheating station and the heating station in an alternate circulating mode respectively, and convey the workpieces to the preheating coil of the preheating station and the heating coil of the heating station in an alternate circulating mode.

3. The brake drum heating apparatus according to claim 2, wherein: the feeding station, the preheating station and the heating station are arranged on a fixed disc in the same plane, in the same center, in the same diameter and in the same radian; the workpiece conveying device is arranged on a rotating disc in the same plane, concentric, equal-diameter and equal-radian mode; the fixed disc and the rotating disc are coaxially and horizontally arranged in parallel, and the rotating disc is provided with a rotating device and a lifting device.

4. The brake drum heating apparatus according to claim 3, wherein: the rotating disc realizes that the workpiece conveying device alternately and circularly vertically corresponds to the feeding station, the preheating station and the heating station through rotation; the rotating disc realizes that the workpiece conveying device is alternately and circularly positioned at the feeding station, the preheating station and the heating station through the lifting device.

5. The brake drum heating apparatus according to claim 2, wherein: the feeding station, the preheating station and the heating station are arranged on a fixed disc in the same plane, in the same center, in the same diameter and in the same radian; the workpiece conveying device is arranged on a rotating disc in the same plane, concentric, equal-diameter and equal-radian mode; the fixed disc and the rotating disc are coaxially and horizontally arranged in parallel, the rotating disc is provided with a rotating device, and the workpiece conveying device is provided with a lifting device.

6. The brake drum heating apparatus of claim 5, wherein: the rotating disc realizes that the workpiece conveying device alternately and circularly vertically corresponds to the feeding station, the preheating station and the heating station through rotation; the workpiece conveying device is positioned at the feeding station, the preheating station and the heating station in an alternate and cyclic mode through the lifting device.

7. The brake drum heating apparatus according to claims 1 to 6, wherein: the workpiece conveying device is provided with a self-rotating device, and the workpiece conveying device drives the workpiece to rotate when the workpiece is preheated or heated.

8. A brake drum heating process of the brake drum heating apparatus according to claims 1 to 7, wherein: the method comprises the following steps:

first-step feeding: when the rotating disc is horizontally high, the workpiece is fixed on a workpiece transfer device of the feeding station;

the second step is descending and rotating: the rotating disc descends to a horizontal low position and rotates by 120 degrees;

the fourth step is descending and rotating: the rotating disc descends to a horizontal low position and rotates by 120 degrees;

9. A heating process according to claim 8, wherein: when the workpiece conveying device preheats and heats workpieces at the preheating station and the heating station, the subsequent workpiece conveying devices are respectively positioned at the feeding station and the preheating station to carry out workpiece feeding and workpiece preheating, and the workpiece conveying devices in the pre-sequence are respectively positioned at the heating station and the feeding station to carry out workpiece heating and workpiece feeding; when the workpiece is preheated in the preheating coil and heated in the heating coil, the workpiece conveying device is provided with a rotation device which drives the workpiece to rotate.

10. A brake drum heating process of the brake drum heating apparatus according to claims 1 to 7, characterized by comprising the steps of:

the second step is descending and rotating: the workpiece conveying device descends to a horizontal low position, and the rotating disc rotates by 120 degrees;

the fourth step is descending and rotating: the workpiece conveying device descends to a horizontal low position, and the rotating disc rotates by 120 degrees;

fifthly, ascending heating: the workpiece conveying device rises to a horizontal high position when rotating to a heating station, and the workpiece is preheated in a heating coil;

11. A heating process according to claim 10, wherein: when the workpiece conveying device preheats and heats workpieces at the preheating station and the heating station, the subsequent workpiece conveying devices are respectively positioned at the feeding station and the preheating station to carry out workpiece feeding and workpiece preheating, and the workpiece conveying devices in the pre-sequence are respectively positioned at the heating station and the feeding station to carry out workpiece heating and workpiece feeding; when the workpiece is preheated in the preheating coil and heated in the heating coil, the workpiece conveying device is provided with a rotation device which drives the workpiece to rotate.