WO2025033549A1 - Steel insert-cast vehicle body structure and die casting device - Google Patents

Abstract

A steel insert-cast vehicle body structure (11) according to an embodiment of the present invention comprises: a vehicle body skeleton member (13) which constitutes a vehicle body skeleton (10) formed from a steel material and having a prescribed shape; and a pair of cast members (15a, 15b) which are provided so as to be cast respectively around a pair of side wall parts (13b, 13c) provided to the vehicle body skeleton member (13). The pair of side wall parts (13b, 13c) are set apart from each other by a prescribed distance, and the pair of cast members (15a, 15b) are each provided as a separate part. In this way, when using a die casting device (30) to manufacture a product for a vehicle body, a steel insert-cast vehicle body structure with which it is possible to suppress misrun appearance defects as much as possible is obtained.

Description

Cast-in steel body structure and die-casting equipment

The present invention relates to a steel cast-in car body structure and a die-casting device.

Recently, with the spread of electric vehicles, one-piece cast car bodies that are both lightweight and easy to mass-produce are being adopted (see Non-Patent Document 1). One-piece cast car bodies are becoming mainstream mainly in the United States and China. On the other hand, in Japan, the introduction of one-piece cast car bodies has not progressed due to various circumstances.

"Tesla's New Body Strategy: The World's Largest Casting Technology to Advance Lightweighting," [online], 2020.07.20, [Retrieved July 25, 2023], Internet <URL: https://blog.evsmart.net/electric-vehicles/tesla-aluminum-die-cast-technology/>

To produce a one-piece cast vehicle body, a 6,000-ton class die-casting machine (hereinafter sometimes referred to as a "giga press machine"). Here, the size of the die-casting machine refers to the clamping force. However, in Japan, due to constraints such as the country's road conditions (more on this later), only die-casting machines of around 3,500 ton class exist.

The weight of the components related to the Giga Press Machine is approximately 100 tons. However, in Japan, the maximum weight of goods that can be transported by road is limited to 100 tons (provided that advance notification is given and that travel is at or below 20 km/h during late night hours). For this reason, it is not easy to transport the components related to the Giga Press Machine in Japan. As a result, it is extremely difficult to install a Giga Press Machine in a factory or other facility in Japan.

For example, the dimensions of a one-piece cast car body workpiece related to the car body floor are about 1700 mm in both width and height. If molten aluminum is poured into the center of the workpiece for casting, the aluminum filling distance will be about 1000 mm. As a result, there are concerns that the appearance of the molten metal may deteriorate when casting a one-piece cast car body workpiece. Common sense in the die casting industry holds that it is extremely difficult to manufacture a workpiece with a filling distance (flow length) of about 1000 mm.

The extent to which the appearance of the molten metal running affects its strength is currently unknown. To clarify the extent to which the appearance of the molten metal running affects its strength, a comprehensive verification is required that takes into account evaluations of the strength in a perfect molten metal running state and in an imperfect state. Including consideration of what level of strength margin should be set, the current situation is that there are a mountain of difficult issues to overcome before introducing one-piece cast car bodies, and the end is uncertain.

In addition, the issue of preventing poor appearance due to molten metal running when manufacturing car bodies using die casting equipment is not unique to Japan, but is a universal issue in countries around the world.

The present invention has been made to solve the above-mentioned problem, and has an object to provide a cast-in steel car body structure that can minimize poor appearance due to molten metal running when manufacturing a car body using a die casting device.
Another object of the present invention is to provide a die casting apparatus applicable to the manufacture of a car body having the above-mentioned cast-in steel car body structure.

In order to achieve the above objective, the steel cast-in car body structure of the present invention comprises a car body frame member made of steel, and cast members arranged to cast-in each of a plurality of portions of the car body frame member, the plurality of portions being set apart a predetermined distance from each other, and the cast members being arranged as separate bodies, as its most important feature.

The present invention provides a steel cast-in car body structure that can minimize appearance defects due to molten metal running when manufacturing car body products using a die casting machine.

1 is an external perspective view of a steel cast-in body structure according to an embodiment of the present invention; 1B is a perspective view showing a state in which the steel cast-in body structure shown in FIG. 1A is incorporated into a body frame. FIG. FIG. 2 is a front view of a fixed die plate provided in the die casting apparatus according to the embodiment of the present invention. FIG. 1 is an explanatory diagram showing a comparison of the specifications of the die casting apparatus according to a comparative example and an embodiment of the present invention. 1 is a front view of a die casting apparatus according to an embodiment of the present invention. 1 is a diagram showing a die casting apparatus according to an embodiment of the present invention as viewed from above. 1 is a conceptual diagram showing a state in which molten metal is sucked in by a water supply robot that supplies molten metal to an injection section provided in a die casting apparatus according to an embodiment of the present invention. FIG. 4B is a conceptual diagram showing a state in which molten metal is supplied to an injection part of a die casting device in the hot water supply robot shown in FIG. 4A. FIG. 2 is a process diagram of a die casting device according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cast-in steel vehicle body structure and a die casting device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
In the drawings shown below, components having common functions are denoted by common reference symbols, and the sizes and shapes of components may be exaggerated or deformed for ease of explanation.
When directions are used in the explanation, they are based on front-rear, left-right, and up-down as seen by the driver sitting in the driver's seat (front right side) unless otherwise specified. In other words, the "front-rear direction" corresponds to the "vehicle length direction," the "left-right direction" corresponds to the "vehicle width direction," and the "up-down direction" corresponds to the "vehicle height direction."

[Steel cast-in car body structure 11 according to an embodiment of the present invention]
First, a steel cast-in car body structure 11 according to an embodiment of the present invention will be described with reference to Figs. 1A and 1B.
Fig. 1A is an external perspective view of a cast-in steel body structure 11 according to an embodiment of the present invention. Fig. 1B is a perspective view showing a state in which the cast-in steel body structure 11 shown in Fig. 1A is assembled into a body frame 10.

As shown in FIG. 1A , a steel cast-in body structure 11 according to an embodiment of the present invention is configured to include a body frame member 13 that constitutes a body frame 10 made of steel having a predetermined shape, and a pair of cast members 15 a, 15 b that are arranged to cast-in a plurality of portions (a pair of side wall portions) 13 b, 13 c of the body frame member 13.
In this embodiment, a rear skeleton member will be exemplified as the vehicle body skeleton member 13. Therefore, in the following description, the vehicle body skeleton member 13 will be referred to interchangeably as the "rear skeleton member 13."

As shown in FIG. 1B, the rear frame member 13 is made up of a substantially rectangular floor wall portion 13a that constitutes the rear seat floor, and a pair of side walls 13b, 13c that rise upward from both ends of the floor wall portion 13a in the vehicle width direction and have a substantially U-shaped cross section when viewed from the front, forming the vehicle body frame 10 at the rear of the vehicle.

The pair of side wall portions 13b, 13c are configured to include a pair of skeletal main body portions 13b1, 13c1 respectively connected to both end edges in the vehicle width direction of the floor wall portion 13a, a pair of skeletal relay portions 13b2, 13c2 respectively connected to the front lower portions of the pair of skeletal main body portions 13b1, 13c1, and a pair of skeletal joint portions 13b3, 13c3 respectively connected to the front sides of the pair of skeletal relay portions 13b2, 13c2.
Each of the pair of framework main body portions 13b1, 13c1 is provided with a pair of framework flange portions 13b11, 13c11 that protrude from the upper outer circumferential edge toward the outside of the vehicle body.
The pair of side walls 13b, 13c correspond to the "pair of bent portions" of the present invention.

1A, the pair of cast members 15a, 15b are provided so as to cast-in the pair of side wall portions 13b, 13c, respectively. That is, the pair of cast members 15a, 15b are configured to include a pair of cast main body portions 15a1, 15b1 which cast-in the pair of skeletal main body portions 13b1, 13c1, respectively, a pair of cast relay portions 15a2, 15b2 which cast-in the pair of skeletal relay portions 13b2, 13c2, respectively, and a pair of cast joint portions 15a3, 15b3 which cast-in the pair of skeletal joint portions 13b3, 13c3, respectively.
A pair of skeletal flange portions 13b11, 13c11 belonging to the pair of skeletal main body portions 13b1, 13c1 are provided with a pair of cast flange portions 15a11, 15b11 that respectively cast-in the pair of skeletal flange portions 13b11, 13c11.

A roughly rectangular through hole 13d is provided in the floor wall portion 13a of the rear frame member 13. The through hole 13d is provided with the aim of reducing the weight of the rear frame member 13 including the floor wall portion 13a.

Furthermore, a pair of skeletal flanges 13b11, 13c11 belonging to the pair of skeletal main bodies 13b1, 13c1 of the pair of side walls 13b, 13c are provided with mounting parts for the rear suspension (not shown). However, the mounting parts for the rear suspension may be provided on the pair of cast members 15a, 15b (pair of cast flanges 15a11, 15b11), which are the surface material, as long as the pair of side walls 13b, 13c (pair of skeletal flanges 13b11, 13c11) made of steel are present as the core material.

Furthermore, the pair of frame joints 13b3, 13c3 of the pair of side wall portions 13b, 13c are welded to the side sills 17a, 17b made of steel, for example. However, a configuration may be adopted in which the pair of cast joints 15b3, 15c3 that encase the pair of frame joints 13b3, 13c3 by casting are welded to the side sills 17a, 17b.
The reference numeral 15c denotes a remaining portion of the molten metal injected through a pair of gates into a cavity formed in the closed mold 41 (see Figs. 3A and 3B), which corresponds to the gates. The remaining portion 15c is cut off in the finishing process of the vehicle body product.

[Functions and Effects of the Cast-in Steel Car Body Structure 11 According to the Embodiment of the Present Invention]
The steel cast-in body structure 11 according to an embodiment of the present invention comprises a rear skeleton member (body skeleton member) 13 made of steel, and a pair of cast members 15a, 15b arranged to cast-in multiple portions (a pair of side wall portions 13b, 13c) of the rear skeleton member 13, the pair of side wall portions 13b, 13c being set a predetermined distance apart, and the pair of cast members 15a, 15b being arranged as separate bodies.
According to the steel cast-in car body structure 11 according to the embodiment of the present invention, when a car body product is manufactured using a die casting device 30 (see Figures 3A and 3B), poor appearance due to molten metal running can be suppressed as much as possible.
More specifically, according to the steel cast-in car body structure 11 according to the embodiment of the present invention, the flow length of the molten metal in the casting process can be shortened compared to the case where the car body product is manufactured by integral casting. As a result, it is possible to improve the molten metal flow and improve the appearance quality of the car body product, which contributes to improving the yield of the car body products.

In addition, in conventional car body manufacturing, flat steel workpieces are bent and multiple bent steel workpieces are welded together at specified locations to produce a car body product with the required external shape.

The steel workpiece is a flat-plate shaped material. Automobile body products are manufactured by bending such flat-plate steel workpieces. Therefore, steel workpieces are suitable for manufacturing automobile body products with relatively simple shapes and many flat surfaces.
In contrast, in the case of casting workpieces using die casting equipment, a specific shape is created by filling a mold with molten metal, which makes it suitable for manufacturing car body products with relatively complex shapes.

The vehicle body product is divided into left and right wheel receiving sections (a pair of side walls 13b, 13c) in which the wheels are located, and a connecting section (floor wall section 13a) connecting the left and right wheel receiving sections.
As shown in Fig. 1A, the left and right wheel housings form a generally arcuate path when viewed from the side of the vehicle body, and have a relatively complex shape. In contrast, the connecting portion has a relatively simple shape with many flat surfaces.
Therefore, it can be said that the left and right wheel housing sections are suitable for manufacturing using cast workpieces by the die casting device 30, while the connecting section is suitable for manufacturing using bending and welding of a steel workpiece.

Therefore, the steel cast-in car body structure 11 according to an embodiment of the present invention makes it possible to utilize the advantages of the steel workpiece and the cast workpiece while mutually compensating for their respective weaknesses.

In particular, in the steel cast-in body structure 11 according to an embodiment of the present invention, a pair of cast members 15a, 15b are provided to cast in a plurality of portions (a pair of side walls 13b, 13c) of a body frame member 13 made of steel. This simultaneously ensures the strength of the cast-in and reduces the casting area. As a result, it is possible to obtain a steel cast-in body structure 11 that can minimize poor appearance due to molten metal running, using, for example, a 3,500-ton die-casting machine 30 (see Figures 3A and 3B), without introducing a high-class die-casting machine such as a gigapress machine.

[Manufacturability of the steel cast-in car body structure 11 according to the embodiment of the present invention]
Next, the manufacturability of the steel cast-in car body structure 11 according to the embodiment of the present invention will be described with reference to FIGS. 2A and 2B.
Fig. 2A is a front view of a fixed die plate 21 provided in a die casting apparatus 30 according to an embodiment of the present invention. Fig. 2B is an explanatory diagram showing the specifications of the die casting apparatus 30 according to the comparative example and the embodiment of the present invention in comparison.

The metal fixed die plate 21 provided in the die casting device 30 according to the embodiment of the present invention is formed in a substantially rectangular shape when viewed from the front and has a predetermined thickness, as shown in FIG. 2A. The four corners of the fixed die plate 21 are provided with through holes 21a, 21b, 21c, and 21d for inserting and fixing tie bars 35 (see FIG. 3A and FIG. 3B). A pair of support legs 23a and 23b are provided on the lower part of the fixed die plate 21.

In FIG. 2B, the comparative example shows the specifications of a 6000-ton class die casting machine 30, and the embodiment shows the specifications of a 3500-ton class die casting machine 30.
The mold clamping force of the die casting apparatus 30 is 6118 tons in the comparative example and 3500 tons in the embodiment, and the mold clamping force of the die casting apparatus 30 in the embodiment is approximately 43% smaller than that of the comparative example.
Regarding the dimensions L1 and L2 of the fixed die plate 21, the dimensions L1 and L2 of the fixed die plate 21 according to the embodiment are smaller than those of the comparative example by about 24 to 25% in both length and width.
Concerning the tie bar intervals (inner side) L3, L4, the tie bar intervals (inner side) L3, L4 in the embodiment are smaller by about 24% both vertically and horizontally as compared to the comparative example.
Concerning the tie bar spacing (outside) L5, L6, the tie bar spacing (outside) L5, L6 in the embodiment is smaller by about 22% both vertically and horizontally than in the comparative example.
Regarding the tie bar diameter L7, the tie bar diameter L7 in the embodiment is about 18% smaller than that in the comparative example.
Although the dimensions of the fixed die plate 21 have been exemplified here, the dimensions of the movable die plate 33 (see FIGS. 3A and 3B) also conform to the dimensions of the fixed die plate 21 .
In other words, the sizes of the fixed die plate 21 and the movable die plate 33 to which the dies are attached are not significantly different between the comparative example and the embodiment, as shown in comparison with Fig. 2B. Therefore, it can be seen that the die casting apparatus 30 according to the embodiment can be fitted with dies of a size capable of casting a vehicle body product of 1700 mm size taking into account the vehicle width dimension.

Next, when manufacturing a 1700 mm sized vehicle body product using the die casting device 30, the necessary clamping force can be calculated by the following formula (1).
Required mold clamping force = required casting pressure x casting projected area ÷ 0.85 (safety factor) Formula (1)
The necessary casting pressure is said to be about 800 to 1000 kg/cm ² for pressure-resistant parts and about 300 to 800 kg/cm ² for covers.
The casting projection area is roughly the size of the one-piece cast body product x 0.7 (because there are holes that are not filled with molten metal).
If the casting pressure is 300 kg/ ^cm2 and the casting projected area is (170 x 170 x 0.7), and these are substituted into formula (1), the calculated value of the required clamping force is 6069 tons. If a safety factor (0.85) is applied to this calculated value (6069), the calculated value of the required clamping force after applying the safety factor is 7140 tons, as shown in the following formula (2).
Required clamping force after applying safety factor = Calculated required clamping force (6069 tons) ÷ 0.85 (safety factor) = 7140 tons Formula (2)
Considering the calculated value (7,140 tons) of the above formula (2), if an attempt is made to operate a Gigapress machine having a clamping force of 6,000 tons under the assumption of a minimum casting pressure (300 kg/cm ² ), it can be seen that casting beyond the machine's capacity would be required.

Next, the feasibility of manufacturing the steel cast-in car body structure 11 according to the embodiment of the present invention using the 3,500-ton class die casting machine 30 according to the embodiment will be described.
As described above, the steel cast-in car body structure 11 according to the embodiment of the present invention has a pair of cast members 15a, 15b so as to cast in a plurality of portions (a pair of side walls 13b, 13c) of a car body frame member 13 made of steel. This not only ensures the cast-in strength, but also reduces the casting area (to about half the area required when a car body product is manufactured by integral casting).

Here, the calculated value of the required clamping force after applying the safety factor (0.85) is (7140 tons) as shown in the above formula (2). Dividing this by 2 (due to the reduction in the casting area) gives (3570 tons). By using the 3500-ton class die casting machine 30 according to the embodiment, the calculated value of the required clamping force (3570 tons) can be roughly achieved.
Therefore, by using the 3,500-ton class die casting machine 30 according to the embodiment of the present invention, it is possible to substantially manufacture the steel cast-in car body structure 11 according to the embodiment of the present invention.

[Configuration of the die casting device 30 according to the embodiment of the present invention]
Next, the configuration of a die casting apparatus 30 according to an embodiment of the present invention will be described with reference to FIGS. 3A, 3B, 4A, and 4B.
Fig. 3A is a front view of the die casting apparatus 30 according to the embodiment of the present invention. Fig. 3B is a view of the die casting apparatus 30 according to the embodiment seen from above. Fig. 4A is a conceptual diagram showing a state of suction of molten metal in a molten metal supply robot 51 that supplies molten metal to an injection part 39 provided in the die casting apparatus 30 according to the embodiment. Fig. 4B is a conceptual diagram showing a state of supply of molten metal to an injection part 39 provided in the die casting apparatus 30 in the molten metal supply robot 51 shown in Fig. 4A.

As shown in Figures 3A and 3B, the die casting device 30 according to the embodiment of the present invention is configured with the fixed die plate 21, the base frame 31, the movable die plate 33, a number of tie bars 35 (four in the embodiment), an injection mold 37, an injection section 39, a mold 41, and a plunger 43.

The cylindrical tie bar 35 has a guide function when moving the movable die plate 33, to which the movable die 41a is attached, back and forth relative to the fixed die plate 21.

The injection mold 37 has multiple (a pair in this embodiment) injection sections 39a, 39b, as well as a fixed mold 41b. When the movable die plate 33 moves forward to the casting position, the movable mold 41a and the fixed mold 41b (sometimes collectively referred to as "mold 41") are clamped together and closed. At this time, a cavity (not shown) is formed inside the closed mold 41.

The injection mold 37 cooperates with the plunger 43 to inject molten metal (such as an aluminum alloy) into a cavity formed inside the closed mold 41 using a pair of injection parts 39a, 39b (sometimes collectively referred to as "injection parts 39"). Injection by the injection parts 39 will be described in more detail later.

In order to supply molten metal to each of the pair of injection sections 39a, 39b, as shown in FIG. 3B, a pair of hot water supply robots 51a, 51b (sometimes referred to as "hot water supply robot 51") are provided near both sides of the die casting device 30. The pair of hot water supply robots 51a, 51b are equipped with robot arms 52a, 52b (sometimes referred to as "robot arm 52"). A pair of hot water supply devices 53a, 53b (sometimes referred to as "hot water supply devices 53") are provided near each of the pair of hot water supply robots 51a, 51b.

As shown in FIG. 4A, the hot water supply device 53 is equipped with a hot water supply tank 55 that stores molten metal 57.

As shown in FIG. 4B, the injection section 39 is composed of a cylindrical piston 71 and a cylindrical cylinder 73. The cylinder 73 of the injection section 39 is provided with a sleeve 75 that has an inner diameter into which the piston 71 fits and that contains the molten metal, and a pouring port 39a1 for pouring the molten metal into the sleeve 75.

As shown in FIG. 4A, the robot arm 52a of the hot water supply robot 51a is provided with a head portion 59. The head portion 59 is provided with a storage portion 61 for the molten metal 57. The head portion 59 operates by the action of a suction and exhaust mechanism (not shown) to suck the molten metal 57 stored in the hot water tank 55 of the hot water supply device 53 into the storage portion 61 through the suction and exhaust port 61a of the storage portion 61, while discharging (falling by gravity) and pouring the molten metal 57 stored in the storage portion 61 into the sleeve 75 through the pouring port 39a1 of the injection portion 39.

The piston 71 operates in conjunction with the forward and backward movement of the plunger 43 to inject the molten metal contained in the sleeve 75 formed inside the cylinder 73 into the cavity formed inside the closed mold 41.

[Operation of the die casting device 30 according to the embodiment of the present invention]
Next, the operation of the die casting apparatus 30 according to the embodiment of the present invention will be described with reference to FIG.
FIG. 5 is a process diagram showing the operation of the die casting apparatus 30 according to the embodiment of the present invention.

In step S11 shown in FIG. 5, the die casting device 30 advances the movable die plate 33 to the casting position with the rear frame member (body frame member) 13 as shown in FIG. 1A set in a predetermined position within the movable die 41a and fixed die 41b (die 41). As a result, the movable die 41a and fixed die 41b (die 41) are clamped together and placed in a closed state.

In step S12, the die casting device 30 uses a pair of injection parts 39a, 39b of the injection mold 37 to inject molten metal into the cavity of the closed mold 41 through a pair of gates (not shown) formed in the fixed mold 41b. This produces a car body product having a steel cast-in car body structure 11 according to an embodiment of the present invention, as shown in FIG. 1A.

In step S13, the die casting device 30 moves the movable die plate 33 back to the standby position, opens the metal mold 41, and removes the cast product workpiece. At this time, the injection mold 37 may be retreated to the side of the fixed die plate 21.
In addition, an appropriate lubricant is applied to the inside of the mold 41 opened in step S13.

In step S14, the remaining portion 15c of the solidified cast workpiece after cooling that corresponds to the gate is cut off, and other predetermined finishing processes are carried out. This completes the vehicle body product.

[Functions and Effects of the Die Casting Apparatus 30 According to the Embodiment of the Present Invention]
In general, it is difficult to provide a plurality of injection parts 39 in the die casting device 30. To explain this, in order to provide the injection parts 39 in the die casting device 30, it is necessary to make holes at predetermined positions in the fixed die plate 21 through which the injection parts 39 can pass. In general, the two-dimensional position of the injection parts 39 relative to the fixed die plate 21 differs for each vehicle model.
The fixed die plate 21 is required to have a strength capable of withstanding the clamping pressure generated during casting while holding the die 41. In this case, when a plurality of injection sections 39 are provided in the die casting device 30, it is necessary to design the fixed die plate 21 for each different vehicle model, which causes a difficult problem to be solved in terms of design man-hours and associated costs.

In order to solve the above problems, the die casting device 30 according to the embodiment of the present invention has a configuration as shown in Figures 3A and 3B, in which an injection mold 37 for injecting molten metal 57 into a cavity formed in a mold 41 is provided between a fixed die plate 21 and a movable die plate 33, and the injection mold 37 has a plurality of injection sections 39 that each inject the molten metal into the cavity through a plurality of gates provided in the mold 41.

The die-casting device 30 according to the embodiment of the present invention employs a novel configuration of an injection mold 37 with multiple injection sections 39, making it possible to manufacture a car body product having a steel cast-in car body structure 11 while using existing die-casting devices as they are without requiring any special modifications.

In the die casting apparatus 30 according to the embodiment of the present invention, a configuration can be adopted in which the molten metal is supplied to each of the multiple injection sections 39 via a molten metal supply robot 51.
According to the die-casting apparatus 30 of the embodiment of the present invention, molten metal is supplied to each of the multiple injection sections 39 via the water supply robot 51, and thus, by injecting the molten metal from the multiple injection sections 39, a pair of cast members 15a, 15b can be provided that cast-in each of the multiple sections (a pair of side wall sections) 13b, 13c of the rear skeleton member (body skeleton member) 13.

In addition, in the die casting device 30 according to the embodiment of the present invention, the molten metal 57 is injected into the cavity formed in the mold 41 via each of the multiple injection parts 39, so the flow length of the molten metal in the casting process can be shortened compared to the case where the molten metal 57 is injected into the cavity formed in the mold 41 via a single injection part 39. As a result, it is possible to improve the flow of the molten metal and improve the appearance quality of the vehicle body products, which can contribute to improving the yield of the vehicle body products.

Before the casting process in which the cast members 15 are cast to encase each of the multiple parts of the body frame member 13 made of steel, it is preferable to preheat the body frame member 13 to a predetermined temperature (e.g., about 250 to 350 degrees Celsius). This is because it is possible to remove grease and oil adhering to the steel surface and to suppress the difference in the shrinkage rate between the steel and the molten metal.

Other embodiments
The above-described embodiments are merely examples of the realization of the present invention. Therefore, the technical scope of the present invention should not be interpreted as being limited by these embodiments. The present invention can be embodied in various forms without departing from the spirit or main characteristics of the present invention.

In the explanation of the steel cast-in body structure 11 according to the embodiment of the present invention, the rear frame member 13 is given as an example of a body frame member, and a configuration in which cast members 15 are provided so as to cast-in each of a plurality of portions of the rear frame member 13 is given as an example, but the present invention is not limited to this example.
For example, a front frame member may be used as the vehicle body frame member, and the cast members 15 may be provided so as to encase a plurality of portions of the front frame member by casting.

In addition, for example, a vehicle body skeleton may be adopted that integrally comprises a front skeleton member, a rear skeleton member, and a bridging skeleton member that connects the front skeleton member and the rear skeleton member, and a configuration may be adopted in which a cast member 15 is provided so as to cast-in the front skeleton member and the rear skeleton member, respectively.
Furthermore, for example, a vehicle body skeleton may be adopted that includes a right side skeleton member and a left side skeleton member in the vehicle width direction, as well as a bridging skeleton member that connects these members to bridge each other, and a configuration may be adopted in which a cast member 15 is provided so as to cast-in the right side skeleton member and the left side skeleton member, respectively.

Furthermore, in the description of the steel cast-in body structure 11 according to an embodiment of the present invention, a pair of side wall portions 13b, 13c are given as an example of multiple portions of the rear frame member (body frame member) 13, and a configuration is given in which a pair of cast members 15a, 15b are provided so as to cast-in the pair of side wall portions 13b, 13c, respectively; however, the present invention is not limited to this example.
A configuration may be adopted in which the cast members 15 are provided for three or more portions of the body frame member 13 so as to encase these three or more portions.
In this case, the number of injection parts 39 provided in the injection mold 37 may be appropriately increased or decreased according to the three or more parts.

Furthermore, in the steel cast-in body structure 11 according to an embodiment of the present invention, the body frame member 13 made of steel is a member used as the body frame 10, which requires rigidity. Therefore, for the body frame member 13, an appropriate combination of structures that increase rigidity may be used, such as bending the steel or using a pipe structure or a box structure.

Furthermore, in the steel cast-in body structure 11 according to an embodiment of the present invention, an example has been described in which the cast members 15 are provided so as to cast-in each of a plurality of portions of the body frame member 13. In this regard, a configuration may be adopted in which the contact area is increased by forming an uneven shape, for example, at the joint between the body frame member 13 and the cast members 15.

In addition, when a steel pipe structure or box structure is used as the body frame member 13, if molten metal is filled inside and outside the pipe structure or box structure, it is possible to expect the effect of further increasing the rigidity and joint strength at the joint between the body frame member 13 and the cast member 15.

Finally, a 3,500-ton class die-casting machine 30 has been illustrated as an example of the die-casting machine 30 according to an embodiment of the present invention, and an example of manufacturing a car body product having a steel cast-in car body structure 11 according to an embodiment of the present invention using the 3,500-ton class die-casting machine 30 has been described, but the present invention is not limited to this example.
For example, a giga press machine having a clamping force of 6000 tons or more may be used to manufacture a car body product having the steel cast-in car body structure 11 according to an embodiment of the present invention.
This configuration can further enhance the effect of suppressing poor appearance of molten metal running.

10 Body frame 11 Steel cast-in body structure 13 Rear frame member (body frame member)
13b, 13c A pair of side walls (a pair of bent portions)
Reference Signs List 15 Casting member 15a, 15b Pair of casting members 21 Fixed die plate 30 Die casting device 33 Movable die plate 37 Injection mold 39 Injection section 39a, 39b Pair of injection sections 41 Mold 51 Hot water supply robot

Claims (5)

A vehicle body frame member made of steel;
and a cast member provided so as to encase each of a plurality of portions of the vehicle body frame member,
The plurality of portions are set at a predetermined distance from each other,
The steel cast-in car body structure, wherein the cast members are provided as separate bodies. a vehicle body frame member made of steel, the vehicle body frame member including a floor portion of a vehicle body and a pair of bent portions at both ends of the floor portion in a vehicle width direction;
a pair of cast members provided so as to respectively cast-in at least the pair of bent portions of the vehicle body frame member,
The steel cast-in car body structure, wherein the pair of cast members are provided as separate bodies. The steel cast-in car body structure according to claim 2,
A steel cast-in car body structure, characterized in that the pair of bent portions are provided with mounting portions for a suspension. A die casting apparatus used for providing cast members by casting into a plurality of portions of a vehicle body frame member made of steel, the plurality of portions being set at a predetermined distance apart, comprising:
an injection mold for injecting molten metal into a cavity formed in the mold is provided between the fixed die plate and the movable die plate;
The die casting apparatus according to claim 1, wherein the injection mold is provided with a plurality of injection portions each for injecting molten metal into the cavity through a plurality of gates provided in the die. The die casting apparatus according to claim 4,
A die casting apparatus, characterized in that the molten metal is supplied to each of the plurality of injection parts via a molten metal supply robot.

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