GB2053105A - Vehicle posture control system using hydropneumatic suspension units - Google Patents

Abstract

A vehicle posture control system for a road vehicle, comprising first and second hydropneumatic suspension units (A and B) each of which has a piston rod (1, 1a) defining a fluid pressure operating chamber (21) which is in communication with a pressure storing chamber (14, 14a), and an aperture (26, 26a) which is openable to the fluid pressure operating chamber (21) in response to the movement of the piston rod (1, 1a), and a valve (33, 33a) disposed between the aperture and the fluid storing chamber (13) of the first hydropneumatic suspension unit (A) and being closable to block communication therebetween in response to the pressure within the pressure storing chamber (14a) of the second hydropneumatic suspension unit (B), thereby attaining a desirable vehicle posture without noticeable inclination of a vehicle body even during turning of the vehicle to the right or left. <IMAGE>

Description

SPECIFICATION Vehicle posture control system using hydropneumatic suspension units This invention relates in general to a system for controlling the posture of a road vehicle, and more particularly to such a system composed of self-pumping type hydropneumatic suspension units which are provided with vibration dampening, spring and self-vehicle level control functions.

A hydropneumatic suspension unit is usually positioned between a vehicle body and a suspension member of a road vehicle, which suspension unit is varied in its effective length by the vibration of the suspension member in order to carry out a pumping action for a hydraulic fluid in the suspension unit. The vibration of the suspension member is caused from the irregular surface of a road. Such pumping action generates hydraulic pressure which maintains vehicle body at a constant level.

However, the road vehicle equipped with such hydropneumatic suspension units have encountered the problems that a suspension unit is usually used for each road wheel and therefore the posture of the vehicle body unavoidably becomes unstable, for example, when the vehicle is turned to the left or right.

In other words, with the above-mentioned vehicle equipped with the suspension units, during vehicle turning movement in which the vehicle body inclines, a suspension unit located on the outside of the turn of the vehicle is compressed to contract its length in which the pumping action for hydraulic fluid continues to raise the hydraulic pressure within the suspension unit so as to restore the level of the vehicle body to a predetermined level, whereas another suspension unit located on the inside of the turn of the vehicle extends in length in which the pumping action for the hydraulic fluid is stopped to lower the hydraulic pressure within the suspension unit until the level of the vehicle body reaches the predetermined level.Accordingly, during vehicle turning movement, the hydraulic pressure within the above-mentioned outside and inside suspension units relative to the vehicle turning are kept high and low, respectively.

Therefore, at the time point where the vehicle turning has been completed and is shifted back into the straight-ahead position, the side of the vehicle body which has been located on the outside of the turn until the time point is raised, whereas the other side of the vehicle located on the inside of the turn until the time point is lowered, by which the vehicle body inclines to make the vehicle posture unstable.

Such phenomena are particularly noticeable in the case where the vehicle has finished its turn in one direction and then makes a turn in the opposite direction. This not only causes the vehicle occupants to feel uneasy, but also reduces the stability of the vehicle, which is very dangerous for vehicle occupants.

In view of the above, the object of the present invention is to solve the above-discussed problems which have been encountered in a road vehicle equipped with conventional hydropneumatic suspension units.

According to the present invention, there is provided a vehicle posture control system for a road vehicle having a vehicle body and suspension members, comprising: a first hydropneumatic suspension unit disposed between the vehicle body and the suspension member, said first hydropneu matic suspension unit including a cylinder, a piston rod coaxial with and reciprocally movable in said cylinder, said piston rod defining a fluid pressure operating chamber the fluid pressure in which is capable of acting on said piston rod, a fluid storing chamber formed outside of said cylider, an aperture which is openable to said fluid pressure operating chamber in accordance with the movement of said piston rod, and a pressure storing chamber in communication with said fluid pressure operating chamber; a second hydropneumatic suspension unit disposed between the vehicle body and the suspension member, said second hydropneumatic suspension unit including a cylinder, a piston rod coaxial with and reciprocally movable in said cylinder, said piston rod defining a fluid pressure operating chamber the fluid pressure in which is capable of acting on said piston rod, a fluid storing chamber formed outside of said cylinder, an aperture which is openable to said fluid pressure operating chamber in accordance with the movement of said piston rod, and a pressure storing chamber in communication with said fluid pressure operating chamber; and a first valve disposed between said aperture and said fluid storing chamber of said first hydropneumatic suspension unit, said first valve being closable to block communication between said aperture and said fluid storing chamber in response to the pressure within said pressure storing chamber of said second hydropneumatic suspension unit.

The accompanying drawing is a cross-sectional illustration of an embodiment of a vehicle posture control system in accordance with the present invention.

Referring now to the single Figure, the system comprises a pair of self-pumping type hydropneumatic suspension units A and B which are disposed at the left and right sides of a road vehicle, respectively. The construction and operation of these units A and B are the same as each other, and therefore the following explanation will be given only with respect to the unit A, and reference to the unit B will be by merely adding the character "a" to the reference numeral or character for the corresponding part or element.

The hydropneumatic suspension unit A comprises a hollow piston rod 1 which is formed at one end with a piston 2 which is slidably disposed in a cylinder 3. The piston 2 is formed with a control passage 4 which extends from one end face to the other end face of the piston 2.

A piston rod guide 5 is provided to close one end of the cylinder 3 and provided with a sealiny member 6 which maintains a fluid seal between the piston rod guide 5 and the piston rod 1. An end wall 7 is provided to close the other end of the cylinder 3. and formed with a mounting eye 8. Inner and outer cylinders 9 and 10 are securely connected to the end wall 7 so as to coaxially enclose the cylinder 3. As shown. the outer cylinder 10 is integral with the piston rod guide 5 A mounting eye 11 is securely connected to the outer end of the piston rod 1.

A partition wall 1 2 is formed integral with the outer cylinder 10 to divide an annular space formed between the inner and outer cylinders 9 and 10 into two sections one of which is a storing chamber 1 3 and the other a pressure storing chamber 1 4. The reference numeral 1 5 indicates the free surface of a hydraulic fluid which surface receives the pressure of a gas which is already in the storing chamber 1 3. A cylindrical resilient and flexible partition wail 1 6 is provided to divide the pressure storing chamber 14 into inner and outer annular chambers (no numerals).

The partition wall 1 6 serves to accumulate the pressure of the hydraulic fluid in response to the pumping action of this suspension unit A under the action of the pressure of a gas which is in the above-mentioned outer annular chamber.

A hollow fixed plunger 1 7 is coaxially projected into the cylinder 3 and extends into the hollow piston rod 1, passing through the piston 2. The end section of the plunger 1 7 is provided with a pump intake valve 1 8 through which the hollow 20 of the plunger 1 7 is communicable with the interior of the piston rod 1. A pump discharge valve 1 9 is mounted on the upper surface of the piston 2 so that passages (no numerals) formed through the piston 2 are closable thereby. It is to be noted that the closed pump intake and discharge valves 18 and 1 9 define a pump chamber P within the interior of the hollow piston rod 1.The hollow 20 of the plunger 1 7 communicates with the storing chamber 1 3 through the annular space formed between the inner cylinder 9 and the cylinder 3, in which the hollow 20 serves as a passage through which the fluid is inducted into the pump chamber P. A discharge chamber or fluid pressure operating chamber 21 is separate from the pump chamber P, and communicates with the pressure storing chamber through a passage 22 which is formed through the end wall 7 and the inner cylinder 9. The above-mentioned plunger 1 7 is formed with a small diameter section 23 which extends into the pump chamber P which is smaller in diameter than the other section of the plunger 1 7 and extends into the pump chamber P.It will be understood that a step section 23' is formed at the boundary between the small size section and the other section. A sleeve 24 is slidably disposed around the small diameter section 23, which sleeve is biased to urgingly contact the step section 23' by a spring 25 so as to move relative to the piston 2 along with the hollow plunger 1 7. The small diameter section 23 is formed with a load removal hole 26 which is located at a central part of a range which is covered by the sleeve 24 in the state shown in the Figure. The load removal hole 26 is connected to a passage 31 through a passage (no numeral) formed through the plunger 1 7 and the end wall 7. The sleeve 24 is formed with a pawl section 27 which is contactable with the piston 2 when the piston 2 moves downward relative to the sleeve 24.The pawl section 27 restricts the movement of the sleeve 24 along with the excessive extending movement of the plunger 1 7 relative to the piston 2. It is to be noted that the abovementioned load removal hole 26 is opened to the fluid pressure operating chamber 21 when the extending movement of the plunger 1 7 relative to the piston 2 continues after the above-mentioned restriction of the relative movement of the sleeve 24.

A passage 32 is provided to connect the storing chamber 1 3 with a valve chamber of a valve 33 to which the passage 31 is connected. The valve 33 is so arranged as to normally establish communication between the passages 31 and 32, whereas to block such communication when the pressure in a pressure storing charnber 1 4a of the other unit B or in a passage 34 is higher than the pressure in the pressure storing chamber 14 of the unit A or in the passage 31. The passage 34 connects the pressure storing chamber 1 4a of the unit B with the chamber of the valve 33 as shown. The valve 33 is provided with a spring 35 within the valve chamber to bias a movable valve member (no numeral) in the direction to open the passage 32 to the valve chamber. The valve 33 is further so arranged as to establish communication between the passages 31 and 32 when the pressure within both units A and B simultaneously change to simultaneously raise the levels of the left and right sides of the vehicle.

The operation of the vehicle posture control system with the above-mentioned arrangement will now be discussed: The unit A itself operates as foliows: The unit A is mounted by the mounting eyes 8, 11 along with a metal spring on the vehicle to support a part of the load of the vehicle, in which the reaction force is generated by the pressure of the gas within the pressure storing chamber 1 4 during the no load condition of the vehicle.When both units A and B are balanced with each other as shown in the Figure, the end surface of the body piston 2 becomes coincident with the step section 23' of the plunger 1 7. In this state, when a load is placed on the vehicle, the cylinder 3 moves relative to the piston rod 1 in accordance with the weight of the load, so that the posture control system is at once lowered in its level.

As a result, the gas within the pressure storing chamber 14 is compressed and therefore the reaction force for supporting the load is increased.

When the vehicle begins to move after the loading is completed, the vibration due to the vehicle movement causes reciprocal movement of the piston 2 relative to the cylinder 3, in which the displacement of the fluid from the chamber 21 to the chamber P and vice versa is carried out through the control passages 4 to be restricted, and therefore the above-mentioned vibration is dampened and absorbed.Additionally, during the extending step of the piston rod 1 relative to the piston rod guide 5, a vacuum is created in the pump chamber P so that the hydraulic fluid is inducted from the storing chamber 1 3 to the pump chamber P through the intake passage 20 and the intake valve 18, whereas during the contracting step of the piston rod 1 relative to the piston rod guide 5, the pressure in the pump chamber P rises so that the pressurized hydraulic fluid is discharged through the discharge valve 1 9 to the fluid pressure operating chamber 21 and the pressure storing chamber 1 4. Such pumping action is continued without stopping during vehicle movement.Thus, as a result of the accumulative supply of the hydraulic fluid into the fluid pressure operating chamber 21, the pressure within the fluid pressure operating chamber 21 pushes the piston 1 downward in the drawing, by which the action for restoring the level of the vehicle body is achieved. This action is also achieved the same as above also when the the load on the vehicle is increased.

As soon as the level of the vehicle body has restored to a normal, or predetermined level, the end face of the piston 2 becomes coincident with the surface of the step section 23' of the fixed hollow plunger 1 7. Accordingly, if the piston 2 is pushed downwardly in the drawing, a flow passage 28 has immediately formed in association with the step section 23' so that the pump chamber P becomes directly in communication with the fluid pressure operating chamber 21. This disables the above-mentioned pumping action and therefore the normal level of the vehicle body is maintained. It will be understood that the flow passage 28 is defined between the wall surface of a central bore (no numeral) of the piston 2 and the outer surface of the small diameter section 23 of the fixed plunger 1 7.

It will be apparent that the state of the unit A shown in the Figure which corresponds to the normal level of the vehicle body is maintained irrespective of the weight of the load of the vehicle. When direct communication is established between the chambers 21 and P through the flow passage 28, the piston 2 operates without any contact relationship with the surface of the plunger 17, thereby preventing the clearance between the body piston 2 and the plunger 1 7 from increasing due to wear thereof which will adversely affect the pumping action at the vehicle level storing step, because, the slidable contact between the piston 2 and the plunger 1 7 takes place only during vehicle cruising after the level of the vehicle body is once lowered due to loading on the vehicle.

On the contrary, when the load is removed from the vehicle, the balance between the carried load and the pressure between the pressure storing chamber 1 4 is lost and accordingly the pressure, within the fluid pressure operating chamber 21, acting on the piston 2 causes an excessive extension of the suspension unit A so that the plunger 1 7 moves upward in the drawing relative to the piston 2. During this relative movement of the plunger, since the pawl section 27 of the sleeve 24 contacts the piston 2 so that its further movement is prevented, the plunger 1 7 further moves upward in the drawing, leaving the sleeve 24.Then, the load removal hole 26 of the small diameter section 23 of the plunger 1 7 opens to the fluid pressure operating chamber 21, and therefore the fluid pressure operating chamber 21 comes into communication with the storing chamber 1 3 at low pressure through the passage formed through the plunger 1 7 and the end wall 7, passage 31, the valve 33 and the passage 32. As a result, the hydraulic fluid flows back into the storing chamber 1 3 through the passage formed through the plunger 1 7 and the end wall 7, the passage 31, the valve 33 and the passage 32.This causes a lowering in the pressure within the fluid pressure operating chamber 21, by which the level of the vehicle is lowered until the pressure in the fluid pressure operating chamber 21 is balanced with the residual carrying load and the vehicle weight. This lowered vehicle level approximately corresponds to the normal level.

It will be understood that the hydropneumatic suspension unit B also oprates the same as the hydropneumatic suspension unit A.

Now, the operation of the vehicle posture control system according to the present invention during vehicle turning will be explained.

When the vehicle is, for example, turning to the right, the vehicle body inclines to the left under the action of centrifugal force. Then, the left side suspension unit A contracts, whereas the right side suspension unit B ex tends, and therefore the pressures within the suspension unit A and the suspension unit B are raised and lowered, respectively. As a result, in the left side suspension unit A, the hydraulic fluid in the storing chamber 1 3 is supplied to the fluid pressure operating chamber 21 through the passage 20, the intake valve 18, the pump chamber P and the discharge valve 1 9 under the above-mentioned pumping action, so that the pressure within the fluid pressure operating chamber 21 is raised to extend the length of the suspension unit A.On the contrary, in the right side suspension unit B, a sleeve 24a is lowered in the drawing as mentioned above. which may cause the hydraulic fluid in a fluid pressure operating chamber 21 a to drain into a storing chamber 1 3a through a load removal hole 26a, a passage 31 a, a valve 33a, and a passage 32a. However, since the fluid pressure in the left suspension unit A is sufficiently higher than that in the right suspension unit B, a valve member (no numeral) of a valve 33a is moved upwardiy in the drawing against the bias of the spring to close the valve. Accordingly, the draining operation of the hydraulic fluid from the chamber 21 a to the chamber 1 3 is prevented so as to suppress the lowering in the fluid pressure within the suspension unit B.

When the vehicle subsequently turns to the right, the right suspension unit B is compressed to contract, and the left suspension unit A is extended. Although the left suspension unit B contracts, the degree of contraction thereof is less by an amount which is obtained for the reason that the fluid pressure lowering within the suspension unit B is restricted under the action of the valve 33a as discussed above. Additionally, the fluid pressure rise in the right side suspension unit B due TO the compression thereof is transmitted through the passage 34 to the valve 33 to close the valve 33.As a result, although the hydraulic fluid in the fluid pressure operating chamber 21 is to be drained to the storing chamber 1 3 also under the extension of the left side suspension unit A the same as mentioned above, this draining operation is prevented to suppress the pressure lowering within the left suspension unit A. It will be understood that this vehicle posture control system functions to suppress an excessively large amount of outward inclination of the vehicle body when the vehicle turns in the opposite direction immediately after the initial turning of the vehicle.

When the vehicle is travelling straight ahead, the fluid pressures within the left and right side suspension units A and B become equal, so that the valves 33 and 33a are conditioned as shown in the Figure in which the passage 31 is in communication with the passage 32, and the passage 31 a is in communication with the passage 32a. As a result, if the vehicle body level deviates from the normal level, the left and right side suspension unit A and B operate independently of each other to control the vehicle level to a normal level, thereby restoring automatic vehicle level control function.

As will be appreciated from the above, according to the present invention, a valve is provided in a passage through which a hydraulic fluid of a pressure storing chamber is discharged to a fluid storing chamber in a hydropneumatic suspension unit, and the valve is arranged to close to prevent the discharge of the hydraulic fluid when the pressure in a pressure storing chamber of another hydropneumatic suspension unit is higher than that of the suspension unit. Therefore, pressure drop in the hydropneumatic suspension unit is suppressed, thereby effectively preventing the inclination of a vehicle body immediately after turning of the vehicle to the left or right.

Claims (14)

1. A vehicle posture control system for a road vehicle having a vehicle body and suspension members, comprising: a first hydropneumatic suspension unit disposed between the vehicle body and the suspension member, said first hydropneumatic suspension unit including a cylinder, a piston rod coaxial with and reciprocally movable in said cylinder, said piston rod defining a fluid pressure operating chamber the fluid pressure in which is capable of acting on said piston rod, a fluid storing chamber formed outside of said cylinder, an aperture which is openable to said fluid pressure operating chamber in accordance with the movement of said piston rod, and a pressure storing chamber in communication with said fluid pressure operating chamber;; a second hydropneumatic suspension unit disposed between the vehicle body and the suspension member, said second hydropneumatic suspension unit including a cylinder, a piston rod coaxial with and reciprocally movable in said cylinder, said piston rod defining a fluid pressure operating chamber the fluid pressure in which is capable of acting on said piston rod, a fluid storing chamber formed outside of said cylinder, an aperture which is openable to said fluid pressure operating chamber in accordance with the movement of said piston rod, and a pressure storing chamber in communication with said fluid pressure operating chamber; and a first valve disposed between said aperture and said fluid storing chamber of said first hydropneumatic suspension unit, said first valve being closable to block communication between said aperture and said fluid storing chamber in response to the pressure within said pressure storing chamber of said second hydropneumatic suspension unit.

2. A vehicle posture control system as claimed in Claim 1, further comprising a second valve disposed between said aperture and said fluid storing chamber of said second hydropneumatic suspension unit, said second valve being closable to block communication between said aperture and said fluid storing chamber in response to the pressure within said pressure storing chamber of said first hydropneumatic suspension unit.

3. A vehicle posture control system as claimed in Claim 2, in which said first valve is so arranged as to be openable to establish communication between said aperture and said fluid storing chamber of said first hydropneumatic suspension unit when the pressure in said pressure storing chamber of said first hydropneumatic suspension unit is higher than that in said pressure storing chamber of said second hydropneumatic suspension unit, whereas to be closable to block the communication when the pressure in said pressure storing chamber of said first hydropneumatic suspension unit is lower than that of said pressure storing chamber of said second hydropneumatic suspension unit.

4. A vehicle posture control system as claimed in Claim 3, in which said second valve is so arranged as to be openable to establish communication between said aperture and said fluid storing chamber of said second hydropneumatic suspension unit when the pressure in said pressure storing chamber of said second hydropneumatic suspension unit is higher than that in said pressure storing chamber of said first hydropneumatic suspension unit, whereas to be closable to block the communication when the pressure in said pressure storing chamber of said second hydropneumatic suspension unit is lower than that in said pressure storing chamber of said first hydropneumatic suspension unit.

5. A vehicle posture control system as claimed in Claim 4, in which said first valve is a first three-way valve having a valve member movably disposed in a first valve chamber to which first, second and third passages open, said first passage communicating with said aperture of said first hydropneumatic suspension unit, said second passage communicating with said fluid storing chamber of said first hydropneumatic suspension unit, said third passage communicating with said pressure storing chamber of said second hydropneumatic suspension unit, said valve member being biased by a valve spring to close said third passage when the pressure in said third passage is lower than that in said first passage, whereas being moved to such a position as to close the first passage, compressing said spring, when the pressure in said third passage is higher than that in said first passage.

6. A vehicle posture control system as claimed in Claim 5, in which said second valve is a second three-way valve having a second valve member movably disposed in a valve chamber to which fourth, fifth and sixth passages open, said fourth passage communicating with said aperture of said second hydropneumatic suspension unit, said fifth passage communicating with said fluid storing chamber of said second hydropneumatic suspension unit, said sixth passage communicating with said pressure storing chamber of said pressure storing chamber of said first hydropneumatic suspension unit, said second valve member being biased by a valve spring to close said sixth passage when the pressure in said sixth passage is lower than that in said fourth passage, whereas being moved to such a position as to close said fourth passage when the pressure in said sixth passage is higher than that in said fourth passage.

7. A vehicle posture control system as claimed in Claim 4, in which said piston rod is hollow and formed integrally with a piston through which said piston rod slidably contacts the surface of said cylinder, said piston being formed with a central bore and provided with a valve through which said fluid pressure operating chamber and the inside of said hollow piston rod of said first hydropneumatic suspension unit are communicable.

8. A vehicle posture control system as claimed in Claim 7, in which said aperture is formed in a fixed plunger which is in fixed relation with said cylinder and extends into said hollow piston rod through said central bore of said piston, the tip of said fixed plunger being provided with a valve through which the inside of said hollow piston rod and said fluid storing chamber of said first hydropneumatic suspension unit are communicable, said aperture being formed at the central section of said fixed plunger.

9. A vehicle posture control system as claimed in Claim 8, further comprising a sleeve disposed around said fixed plunger so as to be capable of closing said aperture of said plunger, said sleeve being slidably movable to open said aperture to said fluid pressure operating chamber of said first hydropneumatic suspension unit in response to the movement of said piston rod.

10. A vehicle posture control system as claimed in Claim 9, in which said sleeve is formed with a pawl section which is contactable with said piston of said piston rod so as to be movable with said piston rod.

11. A vehicle posture control system as claimed in Claim 10, in which said fixed plunger is formed with a diameter section which is smaller than the other section of said fixed plunger, a step section being formed at the boundary of said small diameter section and the other section, a part of said small diameter section being always in said hollow piston rod, said sleeve being disposed around said small diameter section.

1 2. A vehicle posture control system as claimed in Claim 11, in which said bore of said piston has a diameter which is larger than the diameter of said small section of said fixed plunger as to form an annular fluid passage between the surface of said bore and the surface of said small diameter section.

1 3. A vehicle posture control system as claimed in Claim 11, further comprising a spring for biasing said sleeve in the direction to contact said step section of said fixed plunger.

14. A vehicle posture control system as claimed in Claim 1, in which said first and second hydropneumatic suspension units are located at the left and right sides of the vehicle, respectively.

1 5. A vehicle posture control system as constructed and arranged substantially as described herein with reference to, and as illustrated in, the accompanying drawing.

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