JP2653871B2 - Method and apparatus for casting a body frame for a motorcycle - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method and apparatus for casting a body frame for a motorcycle, and more particularly, to a light-weight, high-rigidity light alloy frame having excellent formability. The present invention relates to a method and an apparatus for casting a body frame for a motorcycle for production.

BACKGROUND OF THE INVENTION In recent years, sport-type motorcycles have become popular among young people, and the performance of these sport-type motorcycles has been remarkably improved. Along with this, the body frame is required to be further enhanced in rigidity and reduced in weight.
With the above background, recently, a cast body frame made of aluminum alloy or the like has been developed.

Actually, a body frame is known in which the constituent members such as a head pipe, a main frame, and a down tube are separately cast by gravity casting or low pressure casting, and these are welded and joined. But,
In such a body frame, welding work using a jig is complicated, and welding stress remains at the joint. Therefore, a step of removing the stress is required, so that the number of steps is increased and productivity is increased. Absent. Further, there is an inconvenience that the strength of the body frame itself depends on the welding quality.

Therefore, the development of a body frame in which the entire body frame is integrally cast is progressing.

As a prior art relating to this type of body frame, for example, Japanese Patent Application Laid-Open Nos.
2. Description of the Related Art A body frame disclosed in Japanese Patent No. 31576 is known.

First, in a vehicle body frame disclosed in Japanese Patent Application Laid-Open No. 60-176876, components such as a head pipe, a main frame, and a down tube are integrally cast and formed, and the main frame and the down tube are connected. The parts are configured to be connected by a curved part that draws a smooth curve.

This body frame focuses on strengthening rigidity, and although holes are formed in various places for the purpose of weight reduction, the cross-sectional shape is I-shaped, and Inadequate in terms of promotion.

On the other hand, a body frame disclosed in Japanese Patent Application Laid-Open No. 62-31576 is similar to the body frame in that a head pipe and a main frame are integrally formed by casting, but is cast using a core. The cross-sectional shape is partially hollowed out for measurement, and has a U-shaped, E-shaped or C-shaped cross-section.

However, in the case of casting such a body frame, since the core used to form a predetermined cross-sectional shape for weight reduction contains a resin as a binder, the molten metal is There is an inconvenience that the molten gas entrains the resin combustion gas generated when the resin comes into contact with the resin, and casting defects such as nests due to this gas are likely to occur.

On the other hand, there has not been a body frame in which a head pipe, a main frame, a down tube, and the like are integrally cast, and the entire body is not thinned or hollowed for weight reduction. In particular, the first problem is that when trying to increase the thin part of the vehicle body claim, the run-off property becomes extremely poor, and second, the casting defect caused by entrainment of the combustion gas causes the problem of the hollow thin body frame. This is because it has been a technical obstacle in casting.

[Object of the Invention] The present invention has been made in order to overcome the above-mentioned disadvantages, and a low-pressure casting method for a body frame in which each of the components such as a main frame, a head pipe, and a down tube has a thin-walled hollow integrated structure. When casting, the cavities are arranged so that the main pipe side is inclined downward and the rear frame side is inclined upward, and the main gate and the auxiliary gate are arranged along the center line of the cavity, The height of the sprue is varied, and the runner and gate are selected and arranged so as to correspond to the shape of the cavity. An object of the present invention is to provide a method and an apparatus for casting a motorcycle body frame, which enable casting of a motorcycle body frame.

Means for Achieving the Object In order to achieve the above object, the present invention defines a motorcycle body frame including a head pipe, a main frame, and a down tube, the interior of which has a hollow shape. At the time of casting by pouring a molten metal into the cavity, the predetermined portion of the cavity corresponding to the head pipe of the mold is positioned below, and the predetermined portion of the cavity corresponding to the rear frame is positioned upward. The mold is arranged so that the down tube side is directed upward, and the molten metal is directed from the head pipe side to the rear frame and the down tube by a low pressure casting method from a gate communicating with a predetermined portion of the cavity corresponding to the head pipe. The head pipe, main frame, down tube, etc. are integrally formed by pouring And features.

Further, the present invention is a casting apparatus for a motorcycle body frame including a head pipe, a main frame, and a down tube, and having a hollow inside and an integral structure, wherein the down tube side of the body frame is directed upward. A cavity is defined in the mold so as to gradually increase from the front side to the rear side of the body frame, and a plurality of gates are communicated from a front side below the cavity to an upper rear side, and the gate is formed. It is characterized in that it is connected to a pouring device that fills the molten metal by low-pressure casting.

[Embodiment] Next, a preferred embodiment of a casting method for a motorcycle body frame according to the present invention will be described in detail with reference to the accompanying drawings, with reference to preferred embodiments in relation to the apparatus.

FIG. 1 shows a frame body 10 which is a body frame for a motorcycle manufactured by a casting method according to the present embodiment.

The frame body 10 includes a head pipe 12 located at a front end thereof, a main frame 14, and a down tube 16 extending downward from a front portion of the main frame 14.
Is cast by a low-pressure casting method as a seamless integrated structure composed of the respective components. FIG. 2 is a sectional view taken along the line II-II of the frame body 10 in FIG. As can be understood from this figure, the inside of the frame body 10 is entirely hollow.

FIG. 3 shows a motorcycle 18 employing such a frame body 10. Here, reference numeral 20 indicates a front wheel, and a front fork 22 that supports the front wheel 20 is inserted into the head pipe 12. And the mainframe
The engine 24 and the crankcase 26 are mounted and supported by the down tube 14 and the down tube 16. Also the mainframe
A fuel tank 28 is attached to the upper side of 14.

As other members constituting the body frame of the motorcycle 18, in addition to the frame body 10, a swing arm 32 extending horizontally from the rear end of the main frame 14 and supporting the rear wheel 30, A rear frame 36 extends slightly obliquely upward from the rear side of the main frame 14 and has a seat 34 attached thereto.

Next, a casting machine used for casting the frame body 10 will be described with reference to FIG.

In the figure, reference numeral 40 denotes a casting machine. The casting machine 40 is a so-called vertical casting machine, a molten metal holding furnace 42 in which molten metal is heated and held, a work table 44, and a work table 44. The first step in which the core is assembled into the mold by running the
, A second truck 48 for dispensing a casting, and a casting mold 50. Among them, the casting mold 50 is shown in FIG. 7 to FIG.

First, a rack 52 is laid on the work table 44, and the first and second vehicles 46 and 48 run along the rack 52. In this case, the first carriage 46 includes a main body 54 and a mounting table 56 on which a core described later is mounted at a predetermined position via a positioning piece 55.
And the pinion 58 meshing with the rack 52 is driven by a motor to rotate so as to be capable of self-running. The main body 54 and the mounting table 56 are connected via a pantograph 60, and the mounting table 56 is configured to be able to move up and down by using the cylinder 62 as a drive source.

The second truck 48 is also configured in the same manner as the first truck 46, and the components performing the same functions as those of the first truck 46 are denoted by the same reference numerals, and the detailed description of the configuration is omitted. Omitted.

Next, in the center of the worktable 44, four columns 64a to 64d are provided.
The fixed plate 66 is provided at the upper end of the columns 64a to 64d.
Is supported. The fixed plate 66 is provided with a hydraulic cylinder 68, and a piston rod 68a of the hydraulic cylinder 68 is provided.
A movable platen 70 for holding an upper die 82 of a casting die 50 described later is connected to a tip of the movable die 70. Here, guide posts 72a to 72d are connected to the movable plate 70, and the guide posts 72a to 72d
a to 72d are inserted into the fixed board 66. On the lower surface of the fixed board 66, required ejector pins 76 for taking out the cast product are fixed as required, and these ejector pins 76 are fixed to the upper mold 82.
Is inserted through.

 Next, the casting mold 50 will be described.

FIG. 7 is a longitudinal sectional view of the casting mold 50 taken along a longitudinal direction thereof. The casting mold 50 includes a lower die 80 as a fixed die, an upper die 82 fixed to the movable plate 70 described above, and sliding dies 84a and 84b provided before and after the upper die 82, and an eighth die.
As shown in the figure, the upper die 82 is basically composed of sliding dies 86a and 86b provided side by side. The lower mold 80,
The inner surfaces of the upper die 82, the sliding dies 84a, 84b, and the sliding dies 86a, 86b are formed in a shape corresponding to the contour of the frame body, and a core 88 described later and a cavity 88 are defined by these. (See FIG. 9).

First, the lower mold 80 will be described.
Is composed of a lower mold body 89 and inserts 90a and 90b having a product molding surface molded so as to follow the shape of the frame body.
a and 90b are mounted so as to be exchangeable via a required number of positioning blocks 92.

In FIGS. 9 and 10, a gate provided on the lower mold 80 from below includes a main gate 94 provided at the most end side of the lower mold 80 and two auxiliary gates 96, 98.
Consists of Main gate 94 is connected to Stoke 1 via connecting pipe 100
02, the end of the stalk 102 is
It is immersed in the molten metal stored in 2. Similarly, the auxiliary gates 96 and 98 are connected to the molten metal holding furnace via the auxiliary stokes 104 and 106.
It communicates with 42.

Here, as shown in FIG. 10, the main spout 94 communicates with the main runners 108a, 108b and the cavity 88 via the main gates 110a, 110b, while the auxiliary spout 96,
Reference numeral 98 denotes the cavities via the sub-runners 112a to 112c and 114a to 114c, and the sub-gates 116a to 116c and 118a to 118c, respectively.
It communicates with the 88 side. As described above, a runner-gate method is employed as a gate scheme for injecting molten metal from the main gate section 94 and the auxiliary gate sections 96 and 98 into the cavity 88. Other detailed description of this gate method will be described later.

Next, the upper mold 82 will be described. The upper mold 82 has an upper mold body 120 and inserts 122a and 122 on which a product molding surface is formed.
b, and the inserts 122a and 122b
Is fixed so as to be exchangeable via a positioning block 124 as in the case of the lower die 80 described above.
In this case, a first vacuum circuit 126 communicating with the cavity 88 is connected to the upper die 82. That is, the sliding dies 84a, 84
Cavity 8 via parting line between b and upper mold 82
The intake holes 128 and 130 communicating with the intake hole 8 are defined.
8, 130 are connected to the first vacuum pump 136 via lines 132, 134.

Next, a total of four sliding dies 84a, 84b and sliding dies 86a, 86b are provided on the front, rear, left and right sides of the upper die body 120. Seventh
FIG. 8 shows sliding dies 84a and 84b provided at the front and rear, and FIG. 8 shows sliding dies 86a and 86b provided at the left and right.

In FIG. 7, the sliding dies 84a and 84b respectively correspond to the sliding dies 13a.
8a, 138b and inserts 140a, 140b,
The piston rods 146a, 14b of the sliding cylinders 144a, 144b attached via L-shaped stays 142a, 142b to
Connected to 6b. A second vacuum circuit 148 is connected to one of the sliding dies 84a. In this case, insert 1
A hole 150 is defined in 40a, the hole 150 communicates with the intake passage 152 via an air vent 154, and the intake passage 152 has a conduit 156.
Is connected. A second vacuum pump 158 is connected downstream of the pipe 156.

On the other hand, in FIG. 8, the sliding dies 86a and 86b disposed on the left and right of the upper die 82 have the same configuration, and include the sliding die main bodies 160a and 160b and the inserts 164a and 164b. Body
It is connected to piston rods 170a, 170b of sliding cylinders 168a, 168b attached to L via 120 through L-shaped stays 166a, 166b.

Next, the frame body 10 performed using the casting machine 40 is used.
Hereinafter, a method of manufacturing the device will be described.

First, FIG. 5 shows a core. In casting the frame body 10, each component of the frame body 10, that is, the head pipe 12, the main frame 1
4. In order to make the shape of the down tube 16 or the like hollow and thin in cross section, a divided core corresponding to each part is adopted in advance.

As will be understood that FIG. 1 and FIG. 5 are mutually contrasted, each core is prepared so as to correspond to the shape of each part of the frame body 10. These cores are head pipe 1
2, while forming the down tube 16, the main frame 14, and hollowing the inside of the head pipe molding core 180,
The down tube forming cores 182a and 182b and the main frame forming core 184 are divided and configured. The main frame forming core 184 includes a first split core 186 corresponding to a front portion of the frame body 10 and a second split core 188 corresponding to a rear portion thereof. The first split core 186
Projections 187a and 187b are formed at the tip of the. Each of such various divided cores is solidified with a resin using sand as a raw material, and each is formed into a predetermined shape. In particular, the inside is hollow, and the inside of each core communicates. As shown in FIG. 6, these cores are subjected to a casting process as an integrally assembled core assembly 109, and a first split core 186 of a main frame molding core 184 is described later. A vacuum is drawn from the protrusions 187a and 187b.

Next, in FIG. 4, the core assembly 190 is positioned on the positioning piece 55 on the mounting table 56 of the first truck 46. Thereafter, the first carriage 46 runs by rotating the pinion 58 meshing with the rack 52 of the worktable 44, and stops at a predetermined position below the upper die 82.

Then, the hydraulic cylinder 68 is operated, and the upper die 82 descends and temporarily stops at a position surrounding the core assembly 190. Upper mold 82
While this position is maintained, the mounting table 56 on which the core assembly 109 is mounted rises in the first bogie 46. That is, the pantograph is driven by the driving action of the cylinder 62.
As a result of the extension of 60 upward, the mounting table 56 approaches the upper mold 82. Then, the sliding dies 84a and 84b and the sliding dies 86a and 86b attached to the upper die 82 are clamped. That is, the sliding cylinders 144a, 144b, 168a, 168b operate and the respective piston rods 146a, 146b, 170a, 170b extend, so that the sliding dies 84a, 84b and the sliding dies 86a, 86b move forward. As a result, the core assembly 190 is held,
It will be positioned accurately.

Thereafter, the first carriage 46 moves and separates from the lower die 80 when the fixing of the core assembly 190 is completed. The upper mold 82 descends again and fits into the lower mold 80, whereby the mold is in a clamped state.

Thereafter, a casting step of injecting the molten metal into the cavity 88 is started. The casting conditions at this time are shown below.

Casting conditions Material Aluminum alloy Hot water temperature 720 ° C Mold temperature 360 ° C Pressure 0.5kg / cm ² Then, a predetermined pressure of incurable gas is fed into the molten metal holding furnace 42, where it is heated and held by the molten metal holding furnace 42. The molten metal surface is pressurized with this inert gas. In FIG. 9, the molten metal rises through the main stalk 102, the auxiliary stalks 104 and 106, and a main spout 94 provided in the lower mold 80.
The cavities 88 will be filled from the auxiliary gate portions 96 and 98, and a gate method particularly adopted in the present invention will be described.

As can be understood with reference to FIG. 1, the frame body 10 has a loop shape as a whole and a down tube 16.
It has a rather complicated form including protruding parts such as.
Therefore, when such a product is to be integrally formed and the inside thereof is to be hollow and the inside thereof is to be cast and molded into a thin shape, it is necessary to take a countermeasure against the deterioration of the melt flow.

Thus, in the present invention, when casting the frame body 10 as a hollow and thin integral structure, the direction of the cavity, the number of gates, the gate area, the height of the gate, the location of the runner gate from each gate to the cavity, etc. The following scheme is adopted.

Cavity direction As will be understood when FIG. 1 and FIG. 9 and FIG. 10 are mutually contrasted, the frame body 10 in the mounting posture of the motorcycle is understood.
Mold for casting cavity 88 so that it is upside down
Formed inside 50. In this case, frame body 10
Has a form that extends substantially horizontally from the front side to the rear side and bends downward at the rear side, so that the cavity 88 is conversely substantially horizontal from the front side to the center, and from the center to the rear side. Extends so as to be higher than the front side. The main spout 94 is provided at the lowermost front end, and the molten metal is filled from the main spout 94 to the front side requiring the most volume of the melt, and the auxiliary spouts 96, 98 Should be filled with molten metal. As a result, the head in the process of turning the molten metal in the cavity 88 is reduced, and as a result, the molten metal becomes easy to turn, and there is an effect that it is possible to prevent poor running of the molten metal due to a decrease in the temperature of the molten metal during filling.

Number of Gates and Gate Area As described above, the main gate section 94 and the auxiliary gate sections 96 and 98 are provided as the gate section to provide a multi-point gate. This is because it is actually difficult to spread the molten metal to the cavity 88 only from the main gate 94. So at least 3
There are two gates, that is, in Cavity 88,
The front side with the largest volume of molten metal is filled with molten metal from the main spout 94, and the central and rear sides are supplementary spouts respectively.
It was decided to fill from 96 and 98. At that time, the auxiliary gate section 9
The molten metal poured from 6, 98 goes to the front side of the cavity 88 and interferes with the molten metal from the main spout 94, or the molten metal from the auxiliary spouts 96, 98 goes to the rear side of the cavity 88 first. After that, the molten metal from the main spout 94 becomes the cavity 88
When the front side is filled, the directional solidification of the molten metal is eventually hindered. For this reason, the cavities 94
The total cross-sectional area of the gates 110a and 110b leading to 88 is maximized, and the total cross-sectional area of the gates 116a to 116c and 118a to 118c is reduced in order from the front side to the rear side in the order of the auxiliary gates 96 and 98. I made it. Thereby, the auxiliary gate section 9
The inconvenience of dissolving the solidification balance by avoiding that the molten metal which has been filled in the rear side first and the temperature has been lowered from 6, 98 and turned to the front side is avoided.

Gate height In addition to the cross-sectional area of the gate, the height of the gate is increased from the front side to the rear side. That is, the height of the main gate portion 94 and the auxiliary gate portions 96 and 98 are increased in this order. By doing so, the cavity 88 is filled with the molten metal from the front side to the rear side, together with the similar change in the gate cross-sectional area.

Gate Positions Further, FIG. 10 shows the positional relationship between the main gate 94 and the auxiliary gates 96 and 98 described above and these gates. That is, the main spout 94 faces from below the end of the cavity 88 via the runners 108a, 108b and the gates 110a, 110b, while the auxiliary spouts 96, 98 are runners 112a to 112, respectively.
c, 114a to 114c, gates 116a to 116c, 118a to 118c
Through the inside of the loop formed by the cavity 88. The main gate 94 and the auxiliary gates 96 and 98 are located on the center line of the loop. Thus, the auxiliary gate
The runners 112a to 112c and 114a to 114c of 96 and 98 are branched to form gates 116a to 116 inside the loop of the cavity 88.
By locating c, 118a to 118c, the gate cut processing of the product is facilitated, and the appearance of the product is not spoiled because the cut mark is inside.

Next, according to the above gate method, when the cavity 88 is filled with the molten metal, the resin combustion gas generated when the molten metal contacts the core assembly 190 is led out as follows. That is, a negative pressure state is generated in the hollow portion of the core assembly 190 under the suction action of the second vacuum pump 158, so that the combustion gas is led out of the intake passage 152 through the air vent 154.

In addition, the first vacuum pump 136 sucks the cavity 8
If the pressure on the side 8 is also reduced, the circulation of the molten metal is promoted, and the cavity 88 is filled with the molten metal without corners in combination with the effect of the above-described gate design.

As described above, the pressurized state of the molten metal filled in the cavity 88 is maintained for a predetermined time to solidify the molten metal. Thereafter, the upper mold 82 is lifted to open the mold, and in the upper mold 82, the sliding dies 84a and 84b and the sliding dies 86a and 86b are displaced away from each other to discharge the product. In this case, after the upper mold 82 is lifted, in FIG. 4, the second bogie 48 runs on the work table 44 and stops at a position below the upper mold 82. Thereafter, the sliding cylinders 144a and 144b and the sliding cylinders 168a and 168b are respectively operated, and the sliding dies 84a and 84b and the sliding dies 86a and 86b are retracted.
Then, when the upper die 82 further rises, the ejector pins 76 of the fixed board 66 push out the product, and the product is paid out to the second carriage 48. At this time, in the second carriage 48, the cylinder 62 operates and the pantograph 60 extends upward, so that the mounting table 56 rises and receives the product. And
After the pantograph 60 is folded, the second carriage 48 returns to the end of the worktable by itself while carrying the product. Thereafter, the product is subjected to finishing processes such as gate cutting, core removal, barrel polishing, etc., and becomes a finished product of the frame body 10.

[Effects of the Invention] As described above, according to the present invention, it is possible to overcome the problem of poor runnability, which is a drawback when casting a hollow, monolithic body frame by a low-pressure casting method. Casting defects are prevented, and directional solidification is easily obtained. Therefore, an effect is obtained in which a light-weight, high-quality body frame can be manufactured with excellent appearance moldability.

As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to these embodiments, and various improvements and design changes can be made without departing from the gist of the present invention. Of course.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the appearance of a body frame cast by a casting method according to the present invention, FIG. 2 is a cross-sectional view of the body frame taken along the line II-II in FIG. 1, and FIG. FIG. 4 is a side view of a casting machine used to manufacture the vehicle body frame, FIG. 5 is a perspective view of an individual core used to manufacture the vehicle body frame, FIG. FIG. 7 is a perspective view of a state in which the cores are integrally assembled. FIG. 7 is a sectional view of a casting mold according to the present invention, which constitutes the casting machine shown in FIG. FIG. 9 is a longitudinal sectional view of the casting mold, and FIG. 10 is a perspective view showing the arrangement of gates and runners in a lower mold of the casting mold. It is. 10… Frame body, 12… Head pipe 14 …… Main frame, 16 …… Down tube 40 …… Casting machine, 42 …… Molten metal holding furnace 46, 48 …… Dolly, 50 …… Casting die 66 …… Fixed plate, 68 ... Hydraulic cylinder 70 ... Movable plate, 80 ... Lower die 82 ... Upper die 84a, 84b, 86a, 86b ... Sliding die 88 ... Cavity, 94 ... Main spout 96, 98 …… Auxiliary gate, 190… Core assembly

Continued on the front page (72) Inventor Hironobu Oikawa 1-10-1 Shinsayama, Sayama City, Saitama Prefecture Honda Engineering Co., Ltd. (72) Inventor Shin Otsubo 1-10-1 Shinsayama, Sayama City, Saitama Prefecture Honda Engineering Co., Ltd. (56) References JP-A-1-254479 (JP, A)

Claims (6)

(57) [Claims] The present invention relates to a motorcycle body frame including a head pipe, a main frame, and a down tube, the interior of which is hollow, and is formed by pouring a molten metal into a cavity defined in a mold. The mold is arranged so that a predetermined portion of the cavity corresponding to the head pipe of the mold is positioned below and a predetermined portion of the cavity corresponding to the rear frame is positioned upward and the down tube side is directed upward. The head pipe, the main frame, and the down tube are poured by directing molten metal from the head pipe side to the rear frame and the down tube by a low-pressure casting method from a gate communicating with a predetermined portion of the cavity corresponding to the head pipe. And a method for casting a body frame for a motorcycle. 2. A method according to claim 1, wherein the molten metal is poured from a plurality of gates to the cavities on the rear frame and the down tube side located on the upper side from the head pipe located on the lower side via the runner and the gate, respectively. A casting method for a motorcycle body frame, wherein a molten metal pouring amount on a head pipe side is made larger than that on a rear frame and a down tube side. 3. A casting apparatus for a motorcycle body frame including a head pipe, a main frame, and a down tube and having a hollow interior and an integral structure, wherein the down tube side of the body frame is directed upward. A cavity is defined in the mold so as to gradually increase from the front side to the rear side of the body frame, and a plurality of gates are communicated from a front side below the cavity to an upper rear side, and the gate is formed. A casting apparatus for a body frame for a motorcycle, wherein the casting apparatus is configured to be connected to a pouring apparatus for filling a molten metal by a low pressure casting method. 4. A casting apparatus according to claim 3, wherein the gate comprises a main gate and a plurality of auxiliary gates, each of which is communicated with a cavity through a plurality of runners and gates. A casting apparatus for a motorcycle body frame, wherein a gate cross-sectional area of each gate decreases from a front side to a rear side of the cavity. 5. A casting apparatus for a motorcycle body frame according to claim 4, wherein the height of the gate is increased from the front side to the rear side of the cavity. 6. A casting apparatus according to claim 4, wherein the runner is branched from a plurality of gates and communicates with the cavities through gates, and at least the auxiliary gates are located in a loop formed by the cavities, and the gates are located in the loop. A casting apparatus for a body frame for a motorcycle, wherein the casting apparatus is formed to be located inside the loop.