Cradle assembly

Abstract: A frame structure used in forming a frame assembly (10) for a motor vehicle frame has a tubular frame member (12,14,24,26) having aligned openings (230,231) in its walls and a fastener receiving sleeve (232) extending between the aligned openings (230,231). The fastener receiving sleeve (232) has one end (236) annularly welded to the interior surface of a wall (206,210) in surrounding relation to one of the aligned openings (230) and extends through an opposite one (231) of said aligned openings (230,231) so that an opposite end of said fastener receiving sleeve (232) is disposed outwardly from said interior of the frame member (12,14,24,26). The opposite end of the fastener receiving sleeve (232) has a radially outwardly extending surface (242) constructed and arranged to be engaged by a head of a fastener (246) used to connect said frame structure with at least one other frame structure to form the motor vehicle frame.

Description: The present invention relates to a frame structure for connection with at least one other frame structure used in forming a frame assembly for a motor vehicle frame as defined by the features of the preamble of claim 1. Such a frame structure is described in DE-A-2536060. Typical motor vehicle frames are constructed as a ladder frame assembly or as a uni-body type. The present invention relates to an engine cradle assembly, which is to be secured to a forward portion of a uni-body vehicle frame. The engine cradle is typically provided beneath the vehicle engine and is adapted to have the engine mounted thereon. The engine cradle is also adapted to mount the vehicle front end suspension, steering hydraulics and any other vehicle components deemed appropriate. The cradle assembly must be of a sturdy construction as it is exposed to large mechanical stresses due to the weight of the engine and the entire weight of the vehicle (and transport load) transferred through the cradle assembly to the front end suspension. The cradle assembly is typically made from a pair of spaced side frame members having front and rear ends, a front cross frame member connected across the front ends of the side frame members, and a rear cross frame member extending between the rear ends of the side frame members. A suspension mount structure is typically mounted on the spaced side frame members and is adapted to mount the vehicle front end suspension. Because of the aforementioned mechanical stresses, especially at the portion of the cradle assembly at which the vehicle suspension is to be mounted, it is desirable to manufacture the cradle assembly with particular "strong points" to accommodate for such large localized stresses. There is typically a connection between frame members, for example, the connection between the rear cross frame member and the respective rear ends of the side frame members in the instance in which the rear cross frame member and side frame members are not provided as an integrally formed assembly. Such a connection is typically accomplished with particular frame connectors which prohibit the exterior surfaces of the frame portions which are to be connected from establishing surface-to-surface contact. More particularly, each frame member is typically defined by a substantially rectangular transverse cross-section defined by two pairs of spaced opposite walls. Each of the walls includes an interior and exterior surface, and the frame member has fastener receptacles which enable it to be fastened with another frame member. The fastener receptacle is defined by aligned openings in the spaced opposite walls of at least one of the pairs of walls and a sleeve member extending through the aligned openings. The sleeve member serves as reinforcement for the aligned openings and has opposite ends thereof extending radially outwardly to define opposite flange portions engaging the exterior surface of each of the opposite walls. It can be appreciated that when another frame member is positioned to have the fastener receptacle thereof aligned with the fastener receptacle of the first frame member for securement therebetween with a fastener, flange portions of each receptacle are brought into engagement. This engagement creates a slight gap between the exterior facing surfaces of the flange members to be secured at the areas to be joined. This results in an inherent weakness in the joint, and thus in the entire cradle assembly or vehicle frame incorporating such type of connections. It is thus an object of the present invention to provide a cradle assembly which overcomes the aforementioned problem. According to the present invention, there is provided a frame structure for connection with at least one other frame structure used in forming a frame assembly for a motor vehicle frame, the frame structure comprising: a tubular frame member formed to have a substantially planar wall and an opposite wall, said walls having interior and exterior surfaces, said tubular frame member having aligned openings in the planar and the opposite walls; and, an integrally formed fastener receiving sleeve extending between said aligned openings constructed and arranged to receive a fastener therethrough to enable said frame structure to be connected with said at least one other frame structure; characterised in that: said integrally formed fastener receiving sleeve has one end thereof annularly welded to the interior surface of said planar wall in surrounding relation to one of said aligned openings, said fastener receiving sleeve including an intermediate portion extending from said one end through an interior of the frame member, said fastener receiving sleeve extending through an opposite one of said aligned openings so that an end of said fastener receiving sleeve opposite to said one end is disposed outwardly from said interior of the frame member, said opposite end of said fastener receiving sleeve having a radially outwardly extending surface constructed and arranged to be engaged by a head of said fastener used to connect said frame structure with said at least one other frame structure. Said fastener receiving sleeve may be threaded along said intermediate portion. Said flange portion may be substantially annular in form and welded to the exterior surface of said opposite wall about said opening therein. Said tubular frame member may be formed from a tubular metal blank during a hydroforming process in which fluid pressure is provided internally to said tubular metal blank to radially expand said tubular metal blank so that the frame member has a peripheral configuration modified with respect to an original peripheral configuration of the tubular metal blank. The opening in said planar wall may be smaller than the opening in said opposite wall, and said fastener receiving sleeve may have said one end thereof provided with a larger cross sectional diameter in comparison with said intermediate portion thereof. Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings. In the drawings: FIGURE 1 is a perspective view showing a cradle assembly manufactured in accordance with the principles of the present invention; FIGURE 2 is a perspective view showing a second embodiment of the cradle assembly manufactured in accordance with the principles of the present invention; FIGURE 3 is a perspective view showing the cradle assembly of the present invention mounting various vehicle components; FIGURE 4 is a sectional view showing the connection of the cradle assembly with the vehicle frame as would be viewed along the line 4-4 of FIGURE 1 when the cradle assembly is attached to the vehicle frame; and, FIGURES 5A-5F are sectional views taken through the mould assembly and tubular blank used in forming the frame members, illustrating the hydroforming process used to manufacture the cradle assembly in accordance with the principles of the present invention. Shown generally in FIGURE 1 is a cradle assembly, shown generally at 10, manufactured in accordance with the principles of the present invention. The cradle assembly 10 has a strong, sturdy construction, and is adapted to mount various motor vehicle components, such as the front end suspension, vehicle engine and transmission. The cradle assembly 10 includes a pair of spaced side frame members 12 and 14 having respective front ends 16 and 18, and respective rear ends 20 and 22. The cradle assembly further includes a front cross-frame member 24 connected across the front ends 16 and 18 of the side frame members. A rear cross-frame member 26 extends between the rear ends 20 and 22 of the side frame members. Each of the frame members is formed from a tubular metal blank during a hydroforming process, which will be described in greater detail later. The side frame members 12 and 14 include respective suspension mounts 28 and 30 rigidly secured thereto preferably by welding. Suspension mounts 28 and 30 are constructed in such fashion to permit the front end suspension to be pivotally connected therewith. For example, as shown, the suspension mounts are provided with a pair of parallel side brackets 34 having aligned holes 36, defining a pivot axis for pivotal suspension strut members. The side frame members also include engine mounting holes 38 for mounting the vehicle engine, sway bars 40, and vehicle frame fastener receiving portions 42 and 43 disposed at rear ends 20 and 22, respectively, for enabling the cradle assembly to be secured with a vehicle frame. The front cross-member 24 includes a central portion 44 to which the front ends 16 and 18 of the side frame members are welded. The front frame member also includes opposite end portions 46 and 48 extending rearwardly and laterally outwards from the front end of the associated side frame member. The opposite end portions 46 and 48 contain vehicle frame fastener receiving portions 50 and 52 similar to those at the rear ends of the side frame members. The fastener receiving portions 50 and 52 of the front cross-frame member 24 cooperate with the fastener receiving portions 42 and 43 in the side frame members 12 and 14 to enable the entire cradle assembly to be mounted on the forward end of the vehicle frame. Rigidly secured between each end portion of the front frame member and the associated side frame member are brace members 56 and 58, preferably welded between the front frame end portion and the associated side frame member. The rear cross-frame member 26 contains transmission mounting holes 60, and may be bolted at opposite ends thereof to rear ends 20 and 22 of the respective side frame members 12 and 14. As an alternative arrangement, shown in FIGURE 2, a cradle assembly 110 may have a rear cross-frame member 126 which is integrally formed with the rearward ends 120 and 122 of respective side frame members 112 and 114. As can be appreciated from FIGURE 2, the cradle assembly 110 is similar in all other respects to the cradle assembly 10 shown in FIGURE 1. This alternative construction can also be completed in a hydroforming process, which will be described in greater detail later. FIGURE 3 is a perspective view showing the cradle assembly 10 mounting various vehicle components, including pivotal suspension strut members 70 mounted on the cradle assembly suspension mounts 28 and 30, and steering hydraulic assembly 72. In FIGURE 4, there is shown a sectional view taken through line 4-4 in FIGURE 1, and further including a resilient frame mounting assembly 200, which is not shown in FIGURE 1. The particular construction in FIGURE 4 permits the rear cross-frame member 26 to be easily connected and disconnected to the opposite rear ends 20 and 22 of the side frame members 12 and 14. It similarly allows the entire cradle assembly 10 to be mounted on the vehicle frame via resilient frame mounting assembly 200 of the frame. As can be appreciated from FIGURES 1 and 4, the rear cross-frame member 26 includes fastener receptacles, shown generally at 202 in FIGURE 4, extending therethrough at the end 82 thereof. It can be appreciated, that the opposite end 80 has the same fastener receptacles extending therethrough. Similarly, the side frame members have fastener receptacles 204 extending therethrough at the rearward ends 20 and 22 thereof (end 22 being shown in FIGURE 4). The fastener receptacles 204 at the rearward ends of the side frame members are aligned with the fastener receptacles 202 at the opposite ends of the rear cross-frame member. An appropriate fastener extends through the respective pairs of aligned fastener receptacles to thereby fasten each of the opposite ends of the rear cross-frame member 26 to the respective rear ends 20 and 22 of the side frame members. As shown, the rear cross-frame member 26 and the side frame members 12 and 14 each has a substantially rectangular cross-section, the cross-section of the rear cross-frame member 26 being defined by a pair of spaced horizontal walls 206 and a pair of spaced vertical walls 208. Similarly, each of the side frame members consists of a pair of spaced horizontal walls 210 and a pair of spaced vertical walls 212. The rear cross-frame member 26 has one of its horizontal walls (the lower wall in FIGURE 4) with its exterior surface 214 disposed in surface-to-surface contact at the opposite ends thereof with a respective exterior surface 216 of one of the horizontal walls 210 (the upper horizontal wall in FIGURE 4) of respective side frame rear ends. By enabling a portion of the exterior surface 214 of the rear cross-frame member to be in surface-to-surface engagement with a portion of exterior surface 216 of the respective side frame members, the connection between the rear-cross frame member 26 and the opposite side frame members 12 and 14 is sturdier than where a space is provided therebetween. To provide this surface-to-surface engagement, each fastener receptacle 204 is defined by vertically aligned openings 230 in the spaced horizontal walls of each frame member. The fastener receptacles also include a cylindrical fastener sleeve 232 extending between the vertically aligned openings 230. Each sleeve 232 has one end 236 thereof annularly welded to the interior surface of the associated frame member about one of the aligned openings 230 in the horizontal wall disposed in a surface-to-surface engagement with the exterior surface of the connected frame member. Each fastener sleeve also includes an intermediate portion 240 extending through the associated frame member and through the other vertically aligned opening 230 of the associated fastener receptacle 204. The fastener sleeve has an end opposite the end 236 which extends radially outward so as to define a flange 242 disposed in surface engagement with the exterior surface of the associated frame member about the vertically aligned opening in the horizontal wall spaced from the wall in surface-to-surface engagement with the connected frame member. It can be appreciated that because ends 236 are annularly welded to the interior surfaces of the walls of the respective frame members which are brought together, and because ends 236 do not extend through the openings 230 at said walls, there is no interference between the surfaces of engagement, and no gap is formed therebetween. As shown in FIGURE 4, the fastener receptacles 204 in the rear-cross frame member and in the side frame members 14 are vertically aligned so that the appropriate fasteners, in the form of bolts 246, each extend through the aligned fastener receptacles to thereby fasten the opposite ends 80 and 82 of the rear-cross frame member 26 to the respective rear ends of the side frame members 12 and 14. Bolts 246 have threaded ends 248 which are threaded to intermediate portions 240 of the respective fastener sleeves 232 in the rear-cross frame member 26. The fasteners further comprise a fastener head 250 which engages the flange 242 of the fastener sleeve 232 extending through side frame member 14. When fasteners 246 are tightened into the threaded intermediate portions 240, the fasteners rigidly secure the exterior surfaces 214 and 216 in surface-to-surface engagement. It can be appreciated that the fastener heads 250 can be inverted to engage the respective flanges 242 of the rear-cross frame member if the intermediate portion 240 of the fastener sleeves 232 which extend through the side frame members are threaded to receive the threaded end 248 of the bolts. Next will be described the manner in which cradle assembly 10 is fastened with the vehicle frame. A portion of the vehicle frame is generally indicated by the resilient frame mounting assembly 200 thereof, shown in FIGURE 4. More specifically, frame fastener receiving portions 42 and 43 in the rear ends 20 and 22 of the side frame members, and the frame fastener receiving portions 50 and 52 at the opposite ends portions 46 and 48 of the front cross-frame member 24 each include a pair of vertically aligned openings 260 and 262, as shown in FIGURE 4, and a fastener sleeve 264 extending between the openings. Each fastener sleeve 264 has one end 268 thereof annularly welded to the interior surface of the associated frame member about the opening 260 in the horizontal wall 210 which is to engage the resilient frame mounting assembly 200 of the vehicle frame. The fastener sleeve also includes an opposite end extending radially outwardly to define a flange 270 disposed in surface engagement with the exterior surface of the associated frame member (for example, side frame member 14 in FIGURE 4) about the opening 262 in the horizontal wall 210 spaced from the wall which is to engage the vehicle frame. Each fastener receiving portion is adapted to enable the cradle assembly to be secured with the vehicle, and may include inner and outer interior sleeves 274 extending through the fastener sleeves 264. Preferably, a resilient material 278 is disposed between the fastener sleeves 264, and a fastener, in the form of a bolt 280, extends through the inner interior sleeve to secure the associated side frame member with the resilient frame mounting assembly 200 of the vehicle frame. It can be appreciated that the interior sleeves 274, resilient material 278, and bolt 280 can be considered to be part of frame mounting assembly 200 and not part of the cradle assembly of the present invention. Shown in FIGURES 5A-5F is an apparatus used in forming the frame members of cradle assembly of the present invention. More specifically, the side frame members, front cross-frame member, and rear cross-frame member are formed from tubular metal blanks during a hydroforming process in which each blank has fluid pressure provided internally thereto so that the respective blank is radially expanded into peripheral surface engagement with an interior mold surface so that the blank is radially expanded an average extent preferably > 5% and so that the expanded blank has a generally uniform wall thickness throughout. The blanks in their initial form generally have a constant amount of metal per unit length and are formed during the hydroforming process into frame members having a peripheral configuration modified with respect to the peripheral configuration of the original blank. The side frame members 12 and 14 have the amount of metal per unit length varied so as to present one or more longitudinal areas at which a transverse cross-section defined by the modified peripheral configuration is increased by more than 5% of the original cross-section defined by the peripheral configuration of the original tubular metal blank, and at which the amount of metal per unit length is greater than that of the remainder of the formed frame members. More specifically, it is preferred that the areas of side frame members 12 and 14 which mount the respective suspension mounts 28 and 30 be provided with more metal per unit length than that which is provided by the original blank, and that such areas are expanded by more than 5% of the original cross-section. This stretching of metal and the increase in the amount of metal per unit length increases the strength of the side frame members at those particular locations. FIGURES 5A-5F will now be described in greater detail. As shown in FIGURE 5A, a tubular blank 300, preferably bent slightly in accordance with the intended shape of the frame member to be formed, is inserted between cooperating die halves 302 and 304. The blank can be manufactured by any known process. Preferably, the blank is formed by rolling a sheet of metallic material into a complete closed tubular section and then seam welding it. Typically, the tubular member 300 is pre-bent mechanically, for example, by use of mandrels in a CNC (computer numerically controlled) bending machine. After the tubular member 300 is inserted into the die, the die halves are then closed, as shown in FIGURES 5C and 5D, and hydroforming ports 308 are engaged with opposite ends 306 of the tubular blank 300, and sealed thereto. As the die halves 302 and 304 are moved towards one another, the tube 300 is slightly crushed, for example, into an oval cross-sectional shape, as shown in FIGURE 5D. Next, high pressure water, of approximately 10,000 PSI is provided through the hydroforming ports 308 and into the inner confines of the tubular blank 300. This high pressure causes the tubular blank to expand outwardly into engagement with the interior surface 310 defining the cavity within the die. This causes the tubular blank to take a substantially rectangular cross-sectional shape that conforms to the interior surface 310 of the die (for example, see FIGURE 5F). As the high pressure fluid is provided into the tubular structure, hydroforming ports 308 are forced inwardly against the opposite ends 306 of the blank to replenish the wall thickness of the metal as it expands into contact with the inner surface 310 of the die. During the hydroforming process, the amount of metal per unit length of tube is varied. More specifically, as the linear exterior circumference is outwardly expanded and metal is replenished from the side portions, the wall thickness is maintained within ± 10% of the original blank so that more metal per unit length is provided at all areas of expansion. In the areas of greatest expansion, the exterior surface can be increased by more than 26%, while the wall thickness is maintained within the ± 10% range. Although slightly exaggerated, it can be appreciated that longitudinal area 330 of the member formed in FIGURE 5E represents a portion of either side frame member which is expanded by more than 5% to provide the side frame member with sufficient strength thereat. This area 330 is well suited to be utilized as the area on the side frame member at which one of the suspension mounts 28 or 30 is mounted, in accordance with the principles of the present invention as described hereinbefore. It can be appreciated that it is not necessary for the area 330 to be the only area of expansion greater than 5%, nor is it necessary for the area 330 to be the area of greatest expansion along the side frame member. However, the latter is most preferable because the portion on the side frame members which is to mount the suspension mount is subjected to the greatest amount of stress in the cradle assembly. In FIGURE 5E it can be seen that the ends 306 are deformed as a result of the hydroforming process. Preferably these ends are cut off in a subsequent process before the hydroformed assembly is incorporated into the cradle assembly. A similar hydroforming molding technique to that employed herein is disclosed in greater detail, for example, in "Industrieanzeiger" No. 20 of 9, March 1984; and "Metallumformtechnik", Issue 1D/91, zp. 15 ff: A. Ebbinghaus: "Precision Workpieces in Light Construction, Manufactured Through Internal High Pressure Mouldings"; and "Werkstatt und Betrieb" 123 (1990), 3, P. 241-243: A. Ebbinghaus: "Economic Construction with Internal High Pressure Moulded Precision Workpieces": and "Werkstatt und Betrieb" 122 (1991), 11 (1989), P. 933-938. In the embodiment shown in FIGURE 1, there are four separate frame members, which are formed by hydroforming four separate tubular blanks. The four frame members are then assembled into the four sided figure, as described hereinabove. In the embodiment of FIGURE 2, however, it can be appreciate that the four-sided figure is formed from only two blanks, one blank being formed into the front-cross frame member 24, and the other blank being formed into the side frame members 112, 114, and the rear-cross frame member 126 as an integral unit. More specifically, with respect to the embodiment shown in FIGURE 2, a substantially U-shaped tubular blank is provided and inserted into a molding die. The U-shaped tubular blank is hydroformed so that the bight portion thereof is formed into the rear-cross frame member 126 and the leg portions thereof are formed into the side frame members 112 and 114. The opposite ends of the leg portions of the U-shaped tubular blank are eventually formed into the front ends 115 and 118 of the respective side frame members 112 and 114. During the hydroforming process, the opposite ends of the U-shaped blank are pushed inwardly by the opposite hydroforming ports (such as ports 308 in FIGURES 5A-5F) to replenish the wall thickness of the metal as the blank is expanded. As with the embodiment shown in FIGURE 1, the side frame members 112 and 114 are provided with respective suspension mounts 128 and 130 at longitudinal areas on the side frame members expanded by more than 5%. While the invention has been illustrated and detailed in detail in the drawings and foregoing description, the same is to be considered as illustrative and not limiting in character, it being understood that the preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the appended claims are to be protected.

Claims: A frame structure for connection with at least one other frame structure used in forming a frame assembly (10) for a motor vehicle frame, the frame structure comprising: a tubular frame member (12,14,24,26) formed to have a substantially planar wall (206, 210) and an opposite wall (206,210), said walls having interior and exterior surfaces, said tubular frame member (12,14,24,26) having aligned openings (230) in the planar (206,210) and the opposite (206,210) walls; and, an integrally formed fastener receiving sleeve (232) extending between said aligned openings (230) and constructed and arranged to receive a fastener (246) therethrough to enable said frame structure to be connected with said at least one other frame structure; characterised in that : said integrally formed fastener receiving sleeve (232) has one end (236) thereof annularly welded to the interior surface of said planar wall (206,210) in surrounding relation to one of said aligned openings (230), said fastener receiving sleeve (232) including an intermediate portion (240) extending from said one end (236) through an interior of the frame member (12,14,24,26), said fastener receiving sleeve (232) extending through an opposite one of said aligned openings (230) so that an end of said fastener receiving sleeve (232) opposite to said one end (236) is disposed outwardly from said interior of the frame member (12,14,24,26), said opposite end of said fastener receiving sleeve (232) having a radially outwardly extending surface (242) constructed and arranged to be engaged by a head of said fastener (246) used to connect said frame structure with said at least one other frame structure. A frame structure according to claim 1, wherein said fastener receiving sleeve (232) is threaded along said intermediate portion (240). A frame structure according to claim 1 or claim 2, wherein said flange portion (242) is substantially annular in form and is welded to the exterior surface of said opposite wall (206,210) about said opening (231) therein. A frame structure according to any of claims 1 to 3, wherein said tubular frame member (12,14,24,26) is formed from a tubular metal blank (300) during a hydroforming process in which fluid pressure is provided internally to said tubular metal blank (300) to radially expand said tubular metal blank (300) so that the frame member (12,14,24,26) has a peripheral configuration modified with respect to an original peripheral configuration of the tubular metal blank (300). A frame structure according to any of claims 1 to 4, wherein the opening (230) in said planar wall (206,210) is smaller than the opening (230) in said opposite wall (206,210), and said fastener receiving sleeve (232) has said one end (236) thereof provided with a larger cross sectional diameter in comparison with said intermediate portion (232) thereof.

Inventors: BUTYNSKI GARY A, DEVOR MICHAEL J, GILLE MATTHIAS, HORTON FRANK A, BUTYNSKI, GARY A., DEVOR, MICHAEL J., GILLE, MATTHIAS, HORTON, FRANK A.
Applicants: COSMA INT INC, COSMA INTERNATIONAL INC.
Application year: 1995
Main classification: B62D21
IPC codes: B62D21, F16F1, B60G7, B60G99