Suspension device

In manufacturing a knuckle body forged or cast from light alloy of a suspension device, a large vertical height of a pair of bosses protruding downward from front and rear ends in a lower portion of the knuckle body may cause degradation in forgeability or castability of the knuckle body to hinder manufacturing, and also cause reduction in rigidity of the bosses to reduce mounting strength of a lower arm support bracket made of ferrous metal. A vertical height of the pair of bosses of the knuckle body is set to be smaller than a vertical height of the lower arm support bracket, thereby improving forgeability or castability of the knuckle body and increasing rigidity of the bosses.

RELATED APPLICATION DATA

The Japanese priority application Nos. 2004-57450 and 2004-57453 upon which the present application is based are hereby incorporated in their entirety herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a suspension device in which a knuckle is supported by an upper arm and a lower arm. More particularly, the present invention relates to a suspension device in which a knuckle is formed by connecting a knuckle body forged or cast from light alloy and a lower arm support bracket made of ferrous metal, and a suspension device in which an outer end of a lower arm in a vehicle width direction is supported on a lower arm support bracket connected to a lower surface of an upper arm body via a ball joint.

2. Description of the Related Art

FIG. 5shows a knuckle01of a suspension device according to a first conventional example (Prior Art 1). The knuckle01is formed by connecting a lower arm support bracket03made of ferrous metal to a lower end of a knuckle body02forged from light alloy with two bolts04and05, an outer end of an upper arm06in a vehicle width direction is connected to an upper end of the knuckle01, and an outer end of a lower arm07in the vehicle width direction is connected to the lower arm support bracket03. A pair of bosses02aand02bprotruding downward are integrally formed at front and rear ends in a lower portion of the knuckle body02to which the lower arm07is connected. Front and rear ends of the lower arm support bracket03are fastened to lower surfaces of the bosses02aand02bwith the bolts04and05.

FIG. 6shows a knuckle01of a suspension device according to a second conventional example (Prior Art 2). A space08is formed between a recess02cinterposed between a pair of bosses02aand02bof a knuckle body02and an upper surface of a lower arm support bracket03, and an outer end of a lower arm07in a vehicle width direction is secured with a nut09to an upper end of a ball joint010oscillably supported on the lower arm support bracket03and extending into the space08.

In the knuckle01of the suspension device according to Prior Art 1, the pair of bosses02aand02bsignificantly protrude from the lower portion of the knuckle body02, thus the elongated bosses02aand02bmay cause degradation in forgeability to increase manufacturing costs, and strength of the bosses02aand02bmay be insufficient to which a heavy load from the lower arm07is transferred. Also when the knuckle body02is cast from light alloy, the elongated bosses02aand02bmay interfere with flowing molten metal to cause degradation in castability, and cavities may be created in the bosses02aand02bto reduce quality.

In the knuckle01of the suspension device according to Prior Art 2, when the nut09loosens from vibration caused by driving of a vehicle, the lower arm07may fall off from the ball joint010leading to separation of the lower arm07from the knuckle01.

SUMMARY OF THE INVENTION

The present invention has been achieved in view of the above-mentioned circumstances, and has a first object to improve forgeability or castability and increase rigidity of a pair of bosses formed in a lower portion of a knuckle body forged or cast from light alloy and secured to a lower arm support bracket made of ferrous metal.

The invention has a second object to prevent a ball joint that supports an outer end of a lower arm in a vehicle width direction from falling off from a knuckle even if a nut for securing the ball joint to the knuckle loosens.

In order to achieve the first object, according to a first feature of the present invention, there is proposed a suspension device including: a knuckle formed by connecting a knuckle body forged or cast from light alloy and a lower arm support bracket made of ferrous metal; an upper arm having an inner end in a vehicle width direction connected to a vehicle body, and an outer end in the vehicle width direction connected to an upper portion of the knuckle body; and a lower arm having an inner end in the vehicle width direction connected to the vehicle body, and an outer end in the vehicle width direction connected to the lower arm support bracket, the lower arm support bracket being secured to lower surfaces of a pair of bosses protruding downward from front and rear ends in a lower portion of the knuckle body, wherein a vertical height of the pair of bosses is smaller than a vertical height of the lower arm support bracket.

In manufacturing the knuckle body forged or cast from light alloy, a large vertical height of the pair of bosses protruding downward from the front and rear ends in the lower portion of the knuckle body may cause degradation in forgeability or castability of the knuckle body to hinder manufacturing, and also cause reduction in rigidity of the bosses to reduce mounting strength of the lower arm support bracket. With the above described configuration, however, the vertical height of the pair of bosses is smaller than the vertical height of the lower arm support bracket, thereby improving forgeability or castability of the knuckle body and increasing rigidity of the bosses to increase mounting strength of the lower arm support bracket.

In order to achieve the second object, according to a second feature of the present invention, there is proposed a suspension device including: a knuckle formed by connecting a lower arm support bracket to a lower surface of a knuckle body so as to form a space; an upper arm having an inner end in a vehicle width direction connected to a vehicle body, and an outer end in the vehicle width direction connected to an upper portion of the knuckle body; and a lower arm having an inner end in the vehicle width direction connected to the vehicle body, and an outer end in the vehicle width direction connected to the lower arm support bracket via a ball joint, the ball joint having a head connected to the lower arm in the space, a shaft extending downward from the head to pass through a mounting hole of the lower arm support bracket, and an external thread extending downward from the shaft and onto which a nut is screwed, wherein a distance between the lower surface of the knuckle body facing the space and an upper surface of the outer end of the lower arm in the vehicle width direction is smaller than a distance between a lower end of the external thread of the ball joint and an upper end of the mounting hole of the lower arm support bracket.

With the above described configuration, the ball joint that supports the outer end of the lower arm in the vehicle width direction on the lower arm support bracket of the knuckle includes the head connected to the lower arm in the space between the knuckle body and the lower arm support bracket, the shaft extending downward from the head to pass through the mounting hole of the lower arm support bracket, and the external thread extending downward from the shaft and onto which the nut is screwed; and the distance between the lower surface of the knuckle body facing the space and the upper surface of the outer end of the lower arm in the vehicle width direction is smaller than the distance between the lower end of the external thread of the ball joint and the upper end of the mounting hole of the lower arm support bracket. Thus, even if the nut loosens and falls off from the external thread, the upper surface of the lower arm interferes with the lower surface of the knuckle body to prevent upward movement the lower arm, thereby preventing the ball joint from falling off from the lower arm support bracket to prevent the lower arm from being separated from the knuckle.

The above-mentioned object, other objects, characteristics, and advantages of the present invention will become apparent from an explanation of preferred embodiments, which will be described in detail below by reference to the attached drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown inFIGS. 1 and 2, a double wishbone type suspension device S includes a knuckle13supported on a vehicle body by an upper arm11and a lower arm12. The knuckle13includes a knuckle body14forged from light alloy and a lower arm support bracket15made of ferrous material and fastened to a lower portion of the knuckle body14. The knuckle body14includes an axle support portion14athat rotatably supports an axle of a wheel W and an upper arm support portion14bextending upward from the axle support portion14a. An outer end of the upper arm11in a vehicle width direction is pivotably supported on an upper end of the upper arm support portion14bvia a ball joint16.

As is apparent fromFIG. 3, a pair of bosses14cand14dprotrude downward from front and rear ends in a lower surface of the axle support portion14aof the knuckle body14. A recess14ebowed upward is formed between the bosses14cand14d. The lower arm support bracket15includes mounting portions15aand15bat front and rear ends, a lower arm support portion15cin the middle, and a pair of inclined connecting portions15dand15econnecting the mounting portions15aand15band the lower arm support portion15c. The front mounting portion15ais secured to a lower end of the front boss14cwith a stud bolt17and a nut18, and the rear mounting portion15bis secured to a lower end of the rear boss14dwith a bolt19. The lower arm support portion15cof the lower arm support bracket15is placed in a position lower than the mounting portions15aand15b. An outer end of the lower arm12in the vehicle width direction is placed in a space20formed between the recess14eof the knuckle body14and the lower arm support portion15cof the lower arm support bracket15.

A ball joint21that pivotably supports the outer end of the lower arm12in the vehicle width direction on the lower arm support bracket15has a ball stud22including a spherical head22a, a conical shaft22bconnecting to the head22a, and an external thread22cconnecting to the shaft22b. The shaft22bof the ball stud22passes from above to down through a mounting hole15fprovided in the lower arm support portion15cof the lower arm support bracket15, and is secured by screwing a nut23onto the external thread22cprotruding downward from the lower arm support portion15c. The ball joint21includes a cup-shaped housing12aprovided at an end of the lower arm12. A bearing25made of synthetic resin and in slide contact with the head22aof the ball stud22is housed in the housing12aalong an inner peripheral surface thereof, and held by a retainer26secured so as to cover an opening of the housing12a. A boot27is fitted between the opening of the housing12aand the lower arm support portion15cof the lower arm support bracket15so as to prevent dust from entering a slide surface between the head22aof the ball stud22and the bearing25.

A height h1from a bottom surface of the recess14eof the knuckle body14to lower ends of the bosses14cand14dis smaller than a height h2from the lower ends of the bosses14cand14dto the lower arm support portion15cof the lower arm support bracket15, that is, an input point of a load from the lower arm12to the lower arm support bracket15. Thus, the protruding height h1of the pair of bosses14cand14dprovided at the lower end of the knuckle body14is decreased to facilitate machining for the bosses14cand14dto protrude in forging the knuckle body14to thereby reduce machining costs, and also increase rigidity of the bosses14cand14dto which the load from the lower arm12is transferred via the lower arm support bracket15.

A distance d1from the bottom surface of the recess14eof the knuckle body14to an upper end of the ball joint21is smaller than a distance d2from an upper end of the mounting hole15fin the lower arm support portion15cto a lower end of the external thread22cof the ball stud22. Therefore, even if the nut23for securing the ball stud22of the ball joint21to the lower arm support bracket15loosens and falls off due to vibration caused by driving of a vehicle, and the shaft22bof the ball stud22is about to slip upward out of the mounting hole15fin the lower arm support bracket15, the housing12aof the ball joint21abuts against the bottom surface of the recess14eof the knuckle body14to prevent falling of the ball joint21and reliably prevent the lower arm12from being separated from the knuckle13.

Because the ball joint21cannot be mounted after the lower arm support bracket15is connected to the knuckle body14, the lower arm support bracket15to which the ball joint21is previously mounted needs to be connected to the knuckle body14.

In the first embodiment, the ball stud22of the ball joint21is secured to the lower arm support bracket15, while in the second embodiment, a housing24of a ball joint21is secured to a lower arm support bracket15. Specifically, the housing24of the ball joint21is pressed from above to down into a mounting hole15fformed in a lower arm support portion15cof the lower arm support bracket15. An outer end of a lower arm12in a vehicle width direction fits to a ball stud22protruding downward from the housing24and is fastened with a nut28.

Also in the second embodiment, a height h1from a bottom surface of a recess14eof a knuckle body14to lower ends of bosses14cand14dis smaller than a height h2from the lower ends of the bosses14cand14dto the lower arm support portion15cof the lower arm support bracket15, that is, an input point of a load from the lower arm12to the lower arm support bracket15. This facilitates machining for the bosses14cand14dto protrude in forging the knuckle body14to reduce machining costs, and also increases rigidity of the bosses14cand14d.

The embodiments of the invention have been described, but the invention is not limited to the above described embodiments, and various changes in design may be made without departing from the subject matter of the invention described in the claims.

For example, the double wishbone type suspension device S is described as an example in the embodiments, but the invention is applicable to any other types of suspension devices.

The knuckle body may be cast from light alloy rather than forged from light alloy.