Automobile suspension system

• US 6,017,044 A
• Filed: 07/02/1997
• Issued: 01/25/2000
• Est. Priority Date: 07/05/1996
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Kawagoe, Kenji
• Primary Examiner(s): Dickson, Paul N.
• Assistant Examiner(s): JASMIN, LYNDA C
• Application Number:
  US08/887,236
• Time in Patent Office: 937 Days
• Field of Search: 280/124.141, 280/124.159, 280/124.142, 280/124.145, 280/124.146, 280/124.16, 280/124.103, 280/124.104, 280/124.106 , 280/5.506, 280/5.513, 280/5.515, 280/5.519, 188/322.12, 188/321.11, 267/35, 267/220, 267/226
• US Class Current: 280/124.106
• CPC Class Codes: B60G 2200/1442 including longitudinal rods
• CPC Class Codes: B60G 2200/182 with one longitudinal arm or rod and lateral rods
• CPC Class Codes: B60G 2200/184 Assymetric arrangements
• CPC Class Codes: B60G 2202/12 Wound spring
• CPC Class Codes: B60G 2202/135 Stabiliser bar and/or tube
• CPC Class Codes: B60G 2202/24 Fluid damper
• CPC Class Codes: B60G 2202/312 The spring being a wound spring
• CPC Class Codes: B60G 2500/10 Damping action or damper
• CPC Class Codes: B60G 2500/326 only left or right side
• CPC Class Codes: B60G 2800/012 Rolling condition
• CPC Class Codes: B60G 3/265 with a strut cylinder contributing to the suspension geometry by being linked to the wheel support via an articulation
• CPC Class Codes: F16F 9/38 Covers for protection or appearance
• CPC Class Codes: F16F 9/516 resulting in the damping effects during contraction being different from the damping effects during extension , i.e. responsive to the direction of movement F16F9/504 takes precedence
• CPC Class Codes: F16F 9/54 Arrangements for attachment grommet-type rubber mounting springs per se F16F1/3732; construction of cylinder ends F16F9/3242; attachments to vehicles B60G13/001, B60G15/00

Abstract

An automobile suspension system comprises a front suspension having at least a spring placed between sprung and unsprung masses to support the sprung mass thereon and a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound, and a rear suspension having at least a spring placed between the sprung and unsprung masses to support the sprung mass thereon and a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound. Vertical downward jacking-force characteristics of the front suspension is set to be stronger relatively with respect to vertical downward jacking-force characteristics of the rear suspension during cornering.

Claims

1. An automobile independent suspension system comprising:

a front independent suspension having at least a spring placed between sprung and unsprung masses to support the sprung mass thereon, and a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound; and

a rear independent suspension having at least a spring placed between the sprung and unsprung masses to support the sprung mass thereon, and a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound;

wherein vertical downward jacking-force characteristics of said front suspension is set to be stronger relatively with respect to vertical downward jacking-force characteristics of said rear independent suspension, so that a front end of the vehicle is operated in a falling mode relatively with respect to a rear end of the vehicle during cornering.

2. An automotive front independent suspension system comprising:

a spring placed between sprung and unsprung masses to support the sprung mass thereon; and

a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound,

wherein said front independent suspension system has a spring constant k_fA at each of front-left and front-right road wheels of an automotive vehicle on extension during rebound and a spring constant k_fB at each of the front-left and front-right road wheels of the vehicle on compression during bound,

wherein a ratio ε

_f (=k_fB /k_fA) of said spring constant k_fB on compression during bound to said spring constant k_fA on extension during rebound is determined to satisfy the following inequality, so that a vertical downward jacking-force component is created at a front end of the vehicle and the front end of the vehicle is operated in a falling mode relatively with respect to a rear end of the vehicle during cornering, ##EQU17## where φ

is a roll angle of the vehicle and is equal to Wα

h/(K_f +K_r), W is a car weight, α

is a centripetal acceleration exerted on the vehicle, K_f is a roll stiffness of a front wheel side, K_r is a roll stiffness of a rear wheel side, h is a height of center of gravity of the vehicle, h_f0 is an initial height of roll center of the front wheel side, t is a track being equivalent to a traverse distance between left and right road wheels on a front axle, and a_f is a rate of change in the roll center of the front wheel side with respect to a front-suspension stroke.

3. An automobile front independent suspension system comprising:

a spring placed between sprung and unsprung masses to support the sprung mass thereon; and

a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound,

wherein the shock absorber of said front independent suspension system has a first auxiliary spring placed at each of front-left and front-right ends of an automotive vehicle for suppressing rebound and a second auxiliary spring placed at each of the front-left and front-right ends of the vehicle for suppressing bound,

wherein a spring constant of said first auxiliary spring is set to be greater than a spring constant of said second auxiliary spring, so that a vertical downward jacking-force component is created at a front end of the vehicle and the front end of the vehicle is operated in a falling mode relatively with respect to a rear end of the vehicle during cornering.

4. An automobile rear independent suspension system comprising:

a spring placed between sprung and unsprung masses to support the sprung mass thereon; and

a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound,

wherein said rear independent suspension system has a spring constant k_rA at each of rear-left and rear-right road wheels of an automotive vehicle on extension during rebound and a spring constant k_rB at each of the rear-left and rear-right road wheels of the vehicle on compression during bound,

wherein a ratio ε

_r (=k_rB /k_rA) of said spring constant k_rB on compression during bound to said spring constant k_rA on extension during rebound is determined to satisfy the following inequality, so that a vertical upward jacking-force component is created at a rear end of the vehicle and the rear end of the vehicle is operated in a rising mode relatively with respect to a front end of the vehicle during cornering, ##EQU18## where φ

is a roll angle of the vehicle and is equal to Wα

h/(K_f +K_r), W is a car weight, α

is a centripetal acceleration exerted on the vehicle, K_f is a roll stiffness of a front wheel side, K_r is a roll stiffness of a rear wheel side, h is a height of center of gravity of the vehicle, h_r0 is an initial height of roll center of the front wheel side, t is a track being equivalent to a traverse distance between left and right road wheels on a rear axle, and a_r is a rate of change in the roll center of the rear wheel side with respect to a rear-suspension stroke.

5. An automobile rear independent suspension system comprising:

a spring placed between sprung and unsprung masses to support the sprung mass thereon; and

a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound,

wherein the shock absorber of said rear independent suspension system has a first auxiliary spring placed at each of rear-left and rear-right ends of an automotive vehicle for suppressing rebound and a second auxiliary spring placed at each of the rear-left and rear-right ends of the vehicle for suppressing bound,

wherein a spring constant of said second auxiliary spring is set to be greater than a spring constant of said first auxiliary spring, so that a vertical upward jacking-force component is created at a rear end of the vehicle and the rear end of the vehicle is operated in a rising mode relatively with respect to a front end of the vehicle during cornering.

6. An automobile independent suspension system comprising:

a front independent suspension having at least a spring placed between sprung and unsprung masses to support the sprung mass thereon, and a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound; and

a rear independent suspension having at least a spring placed between the sprung and unsprung masses to support the sprung mass thereon, and a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound,

wherein said front independent suspension has a spring constant k_fA at each of front-left and front-right road wheels of an automotive vehicle on extension during rebound and a spring constant k_fB at each of the front-left and front-right road wheels of the vehicle on compression during bound,

wherein said rear independent suspension has a spring constant k_rA at each of rear-left and rear-right road wheels of the vehicle on extension during rebound and a spring constant k_rB at each of the rear-left and rear-right road wheels of the vehicle on compression during bound,

wherein said spring constant k_fA, k_fB, k_rA and k_rB are determined to satisfy the following inequality, so that a rear end of the vehicle is operated in a rising mode relatively with respect to a front end of the vehicle during cornering, ##EQU19## where φ

is a roll angle of the vehicle and is equal to Wα

h/(K_f +K_r), W is a car weight, α

is a centripetal acceleration exerted on the vehicle, K_f is a roll stiffness of a front wheel side, K_r is a roll stiffness of a rear wheel side, h is a height of center of gravity of the vehicle, γ

is a car-weight distribution rate of the front road wheels with respect to the rear road wheels, h_f0 is an initial height of roll center of the front wheel side, h_r0 is an initial height of roll center of the rear wheel side, t is a track being equivalent to a traverse distance between left and right road wheels, a_f is a rate of change in the roll center of the front wheel side with respect to a front-suspension stroke, and a_r is a rate of change in the roll center of the rear wheel side with respect to a rear-suspension stroke.

7. A method of controlling lacking characteristics at an automobile front independent suspension system having at least a spring placed between sprung and unsprung masses to support the sprung mass thereon, and a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound, the method comprising:

determining a lateral load transfer Δ

W_f of a front independent suspension during a steady-state cornering, using the following expression,

space="preserve" listing-type="equation">Δ

W.sub.f =Wγ

α

h/t

where W is a car weight, γ

is a car-weight distribution rate of front road wheels with respect to rear road wheels, α

is a centripetal acceleration exerted on an automotive vehicle, h is a height of center of gravity of the vehicle, and t is a track being equivalent to a traverse distance between left and right wheels on a front axle;

determining a cornering force F_fA of a front inner wheel and a cornering force F_fB of a front outer wheel, using the following expression,

space="preserve" listing-type="equation">F.sub.fA Wα

γ

(1/2-α

h/t)

space="preserve" listing-type="equation">F.sub.fB Wα

γ

(1/2+α

h/t);

determining an angle θ

_fA between a horizontal line and a line segment including a center of a front inside tire contact and a front inside wheel roll-center height, and an angle θ

_fB between the horizontal line and a line segment including a center of a front outside tire contact and a front outside wheel roll-center height, using the following expression,

space="preserve" listing-type="equation">θ

.sub.fA =a.sub.f φ

+2h.sub.f0 /t-φ

space="preserve" listing-type="equation">θ

.sub.fB =-a.sub.f φ

+2h.sub.f0 /t+φ

where φ

is a roll angle of the vehicle and is equal to Wα

h/(K_f +K_r), K_f is a roll stiffness of a front wheel side, K_r is a roll stiffness of a rear wheel side, h_f0 is an initial height of roll center of the front wheel side, and a_r is a rate of change in the roll center of the front wheel side with respect to a front-suspension stroke;

determining a vertical downward jacking force J_fA created at the front inside wheel and a vertical upward jacking force J_fB created at the front-outside wheel, using the following expression, ##EQU20## determining, during the steady-state cornering, a steady-state rebound amount Z_fA of the front inside wheel and a steady-state bound amount Z_fB of the front outside wheel, using the following expression,

space="preserve" listing-type="equation">Z.sub.fA =(Δ

W.sub.f -J.sub.fA)/k.sub.fA

space="preserve" listing-type="equation">Z.sub.fB =(Δ

W.sub.f -J.sub.fB)/k.sub.fB

where k_fA is a spring stiffness at each front end of the vehicle on extension during rebound and k_fB is a spring stiffness at each front end of the vehicle on compression during bound;

determining a ratio ε

_f (=k_fB /k_fA) of said spring stiffness k_fB on compression during bound to said spring stiffness k_fA on extension during rebound, using the following expression which satisfies a condition defined by an inequality Z_fA ≦

Z_fB according to which a front end of the vehicle is operated in a falling mode being equivalent to stronger vertical downward jacking-force characteristics during cornering, ##EQU21## controlling jacking characteristics of said front independent suspension based on a suspension stiffness characteristics having said spring stiffness k_fB on compression during bound and said spring stiffness k_fA on extension during rebound, said ratio ε

_f (=k_fB /k_fA) of said spring stiffness k_fB to said spring stiffness k_fA being determined to satisfy said expression.

8. A method of controlling jacking characteristics at an automobile rear independent suspension system having at least a spring placed between sprung and unsprung masses to support the sprung mass thereon, and a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound, the method comprising:

determining a lateral load transfer Δ

W_r of a rear independent suspension during a steady-state cornering, using the following expression,

space="preserve" listing-type="equation">Δ

W.sub.r =W(1-γ

)α

h/t

where W is a car weight, γ

is a car-weight distribution rate of front road wheels with respect to rear road wheels, α

is a centripetal acceleration exerted on an automotive vehicle, h is a height of center of gravity of the vehicle, and t is a track being equivalent to a traverse distance between left and right wheels on a rear axle;

determining a cornering force F_fA of a front inner wheel and a cornering force F_fB of a front outer wheel, using the following expression,

space="preserve" listing-type="equation">F.sub.fA =α

W(1-γ

)·

{1/2-α

h/t}

space="preserve" listing-type="equation">F.sub.fB =α

W(1-γ

)·

{1/2+α

h/t};

determining an angle θ

_rA between a horizontal line and a line segment including a center of a rear inside tire contact and a rear inside wheel roll-center height, and an angle θ

_rB between the horizontal line and a line segment including a center of a rear outside tire contact and a rear outside wheel roll-center height, using the following expression,

space="preserve" listing-type="equation">θ

.sub.rA =a.sub.r φ

+2h.sub.r0 /t-φ

space="preserve" listing-type="equation">θ

.sub.rB =a.sub.r φ

+2h.sub.r0 /t+φ

where φ

is a roll angle of the vehicle and is equal to wα

h/(K_f +K_r), K_f is a roll stiffness of a front wheel side, K_r is a roll stiffness of a rear wheel side, h_r0 is an initial height of roll center of the rear wheel side, and a_r is a rate of change in the roll center of the rear wheel side with respect to a rear-suspension stroke;

determining a vertical downward jacking force J_rA created at the rear inside wheel and a vertical upward jacking force J_rB created at the rear-outside wheel, using the following expression, ##EQU22## determining, during the steady-state cornering, a steady-state rebound amount Z_rA of the rear inside wheel and a steady-state bound amount Z_rB of the rear outside wheel, using the following expression,

space="preserve" listing-type="equation">Z.sub.rA =(Δ

W.sub.r -J.sub.rA)/k.sub.rA

space="preserve" listing-type="equation">Z.sub.rB =(Δ

W.sub.r -J.sub.rB)/k.sub.rB

where k_rA is a spring stiffness at each rear end of the vehicle on extension during rebound and k_rB is a spring stiffness at each rear end of the vehicle on compression during bound;

determining a ratio ε

_r (=k_rB /k_rA) of said spring stiffness k_rB on compression during bound to said spring stiffness k_rA on extension during rebound, using the following expression which satisfies a condition defined by an inequality Z_rA ≦

Z_rB according to which a rear end of the vehicle is operated in a rising mode being equivalent to stronger jack-up characteristics during cornering, ##EQU23## controlling jack-up characteristics of said rear independent suspension based on a suspension stiffness characteristics having said spring stiffness k_rB on compression during bound and said spring stiffness k_rA on extension during rebound, said ratio ε

_r (=k_rB /k_rA) of said spring stiffness k_rB to said spring stiffness k_rA being determined to satisfy said expression.

9. A method of controlling jacking characteristics at an automobile independent suspension system employing a front independent suspension having at least a spring placed between sprung and unsprung masses to support the sprung mass thereon and a shock absorber placed between the sprung and unsprung masses to regulate spring rebound and bound and a rear independent suspension system having at least a spring placed between the sprung and unsprung masses to support the sprung mass thereon and a shock absorber placed between the sprung and unsprung mosses to regulate spring rebound and bound, the method comprising:

determining lateral load transfers Δ

W_f and Δ

W_r of the front and rear independent suspensions during a steady-state cornering, using the following expression,

space="preserve" listing-type="equation">Δ

W.sub.f =Wγ

α

h/t

space="preserve" listing-type="equation">Δ

W.sub.r =W(1-γ

)α

h/t

where W is a car weight, γ

is a car-weight distribution rate of front road wheels with respect to rear road wheels, α

is a centripetal acceleration exerted on an automotive vehicle, h is a height of center of gravity of the vehicle, and t is a track being equivalent to a traverse distance between left and right wheels;

determining a cornering force F_fA of a front inner wheel, a cornering force F_fB of a front outer wheel, a cornering force F_rA of a rear inner wheel, and a cornering force F_rB of a rear outer wheel, using the following expression,

space="preserve" listing-type="equation">F.sub.rA =Wα

γ

(1/2-α

h/t)

space="preserve" listing-type="equation">F.sub.fB =Wα

γ

(1/2-α

h/t)

space="preserve" listing-type="equation">F.sub.rA =α

W(1-γ

)·

{1/2-α

h/t}

space="preserve" listing-type="equation">F.sub.rB =α

W(1-γ

)·

{1/2+α

h/t}

determining an angle θ

_fA between a horizontal line and a line segment including a center of a front inside tire contact and a front inside wheel roll-center height, an angle θ

_fB between the horizontal line and a line segment including a center of a front outside tire contact and a front outside wheel roll-center height, an angle θ

_rA between the horizontal line and a line segment including a center of a rear inside tire contact and a rear inside wheel roll-center height and an angle θ

_rB between the horizontal line and a line segment including a center of a rear outside tire contact and a rear outside wheel roll-center height, using the following expression,

space="preserve" listing-type="equation">θ

.sub.fA =a.sub.f φ

+2h.sub.f0 /t-φ

space="preserve" listing-type="equation">θ

.sub.fB --a.sub.r φ

+2h.sub.f0 /t+φ

space="preserve" listing-type="equation">θ

.sub.rA =a.sub.r φ

+2h.sub.r0 /t-φ

space="preserve" listing-type="equation">θ

.sub.rB =-a.sub.r φ

+2h.sub.r0 /t+φ

where φ

is a roll angle of the vehicle and is equal to Wα

h/(K_f +K_r, K_f is a roll stiffness of a front wheel side, K_r is a roll stiffness of a rear wheel side, h_f0 is an initial height of roll center of the front wheel side, and a_f is a rate of change in the roll center of the front wheel side with respect to a front-suspension stroke, h_rφ

is an initial height of roll center of the rear wheel side, a_r is a rate of change in the roll center of the rear wheel side with respect to a rear-suspension stroke;

determining a vertical downward jacking force J_fA created at the front inside wheel, a vertical upward jacking force J_fB created at the front-outside wheel, a vertical downward jacking force J_rA created at the rear inside wheel, and a vertical upward jacking force J_rB created at the rear-outside wheel, using the following expression, ##EQU24## determining, during the steady-state cornering, a steady-state rebound amount Z_fA of the front inside wheel, a steady-state bound amount Z_fB of the front outside wheel, a steady-state rebound amount Z_rA of the rear inside wheel, and a steady-state bound amount Z_rB of the rear outside wheel, using the following expression,

space="preserve" listing-type="equation">Z.sub.fA =(Δ

W.sub.f -J.sub.fA)/k.sub.fA

space="preserve" listing-type="equation">Z.sub.fB =(Δ

W.sub.f -J.sub.fB)/k.sub.fB

space="preserve" listing-type="equation">Z.sub.rA =(Δ

W.sub.r -J.sub.rA)/k.sub.rA

space="preserve" listing-type="equation">Z.sub.rB =(Δ

W.sub.r -J.sub.rB)/k.sub.rB

where k_fA is a spring stiffness at each front end of the vehicle on extension during rebound, k_rB is a spring stiffness at each front end of the vehicle on compression during bound, k_rA is a spring stiffness at each rear end of the vehicle on extension during rebound, and k_rB is a spring stiffness at each rear end of the vehicle on compression during bound;

determining said spring stiffnesses k_fA, k_fB, k_rA and k_rB, using the following expression which satisfies a condition defined by an inequality Z_fB -Z_fA ≦

-Z_rB -Z_rA according to which a front end of the vehicle is operated in a falling mode being equivalent to stronger vertical downward jacking-force characteristics, relatively with respect to the rear end of the vehicle during cornering, ##EQU25## controlling jacking characteristics of said front independent suspension based on a suspension stiffness characteristics having said spring stiffness k_fB on compression during bound and said spring stiffness k_fA on extension during rebound, and on a suspension stiffness characteristics having said spring stiffness k_rB on compression during bound and said spring stiffness k_rA on extension during rebound, said spring stiffnesses k_fA, k_fB, k_rA and k_rB being determined to satisfy said expression.