JP2009120026A - Vehicular electric suspension system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric suspension system reducing the load of one of an extension and contraction direction force generating part and an unsprung part vibration suppressing part, while suppressing deterioration of the damping degree of an unsprung part. <P>SOLUTION: When it is highly necessary to reduce the load of one of the extension and contraction direction force generating part 40 and a damping force generating part 102, owing to shortage of heat generation or electric power, one of an unsprung part damping force component of the extension and contraction direction force generating part 40 and damping force of the damping force generating part 102 is reduced, and the other is increased by processing of a damping load changing program. For example, by processing of S16, S17, when it is determined that a temperature of the extension and contraction direction force generating part 40 is high and a temperature of the damping force generating part 102 is low, in S20, the unsprung part damping force component is reduced, heat generation of the extension and contraction direction force generating part 40 is suppressed, and the damping force of the damping force generating part 102 is increased to suppress deterioration of the damping degree of the unsprung part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric suspension system for a vehicle, and more particularly, to an electric suspension system including an approaching / separating direction force generation device that generates a force in a direction in which a vehicle body and a wheel approach and separate by an electric machine.

The approaching / separating direction force generating device constitutes a part of the suspension device, and is provided to be extendable and contractable between the wheel and the vehicle body. Patent Documents 1 and 2 below describe an example of an approaching / separating direction force generator. The approaching / separating direction force generator includes an electrically operated machine such as an electric motor or a generator, and generates approaching / separating direction force, for example, to improve the riding comfort of the vehicle or to control the posture of the vehicle body. Can do.
Further, in Patent Document 2 below, when the electric working machine generates heat or the capacity of the power supply device is reduced during the roll suppression control, the electric operation is performed by gradually weakening the roll suppression control force and the vibration suppression force. A technique for suppressing the heat generation of the machine and the capability deterioration of the power supply device is described.
JP 2005-271738 A JP 2007-168611 A

However, although the vibration suppression effect decreases when the vibration suppression force is weakened, the above-mentioned Patent Document 2 does not suggest suppressing the decrease in the vibration suppression effect. Further, Patent Document 1 does not describe suppression of heat generation of the electric machine.
As described above, there is still room for improvement in the conventional electric suspension system from the viewpoint of improving practicality, for example, when the heat generation of the electric machine is suppressed, the decrease in the vibration suppression effect is suppressed. In view of such circumstances, the present invention has been made to obtain a more practical electric suspension system.

  In order to solve the above-mentioned problems, an electric suspension system according to the present invention has an approaching / separating force in which an expansion / contraction direction force generation unit and a damping force generation unit, which are two expansion / contraction portions that can be independently expanded and contracted, are provided in series. In order to reduce the burden on one of the expansion force generation unit and damping force generation unit, including the generator, reduce one of the unsprung damping force component of the expansion force generation unit and the damping force of the damping force generation unit In this case, the other of the unsprung damping force component and damping force is increased.

  According to the electric suspension system of the present invention, for example, when reducing the load on the expansion / contraction force generation unit, it is possible to increase the damping force of the damping force generation unit and suppress a decrease in the degree of damping of the unsprung portion. . That is, according to the present invention, a more practical suspension system can be obtained.

Aspects of the Invention

  In the following, some aspects of the invention that can be claimed in the present application (hereinafter sometimes referred to as “claimable invention”) will be exemplified and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is for the purpose of facilitating the understanding of the claimable invention, and is not intended to limit the combinations of the constituent elements constituting the claimable invention to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, the prior art, and the like. In addition, an aspect in which is added, and an aspect in which some constituent elements are deleted from the aspect of each item can also be an aspect of the claimable invention.

  In each of the following paragraphs, (1) is in claim 1, (2) is in claim 2, (3) is in claim 3, (4) is in claim 4, (5) ) Corresponds to claim 5 respectively.

(1) An approaching / separating direction force generator that generates an approaching / separating direction force that is a force in a direction in which the sprung portion and the unsprung portion of the vehicle approach and separate from each other, and a control device that controls the approaching / separating direction force generator. A suspension system,
The approaching / separating direction force generator is
An expansion / contraction direction force generation unit that generates an expansion / contraction direction force that is a force in an expansion / contraction direction including an unsprung damping force component that attenuates vibration of the unsprung portion according to an output of an electric working machine that the device has
A damping force generator that is connected in series with the expansion / contraction direction force generation unit, generates a damping force when passively expanded and contracted, and can change the magnitude of the damping force; and
In order for the control device to reduce a burden on one of the expansion / contraction direction force generation unit and the damping force generation unit, an unsprung damping force component of the expansion / contraction direction force generation unit and a damping force of the damping force generation unit An electric suspension system for a vehicle, comprising: a damping load changing unit that increases the other of the unsprung damping force component and damping force when one of the two is reduced.
The approaching / separating direction force generating device of this section is disposed between the vehicle body and the wheel, and generates an approaching / separating direction force that is a force in a direction in which the vehicle body and the wheel are approached and separated. By controlling the force in the approaching / separating direction to an appropriate magnitude, for example, vibration in the approaching / separating direction of the vehicle can be suppressed, the posture of the vehicle body can be controlled, the vehicle height can be changed, and the like. “Spring upper part” is a part that moves up and down together with the vehicle body, and “Unsprung part” includes a part of the wheel, a wheel holding part that holds the wheel, etc., and a part that moves up and down together with the wheel shaft. .
An approach / separation direction force generator (hereinafter abbreviated as an approach / separation force generator) is arranged in series, and an extension / contraction direction force generator and a damping force generator, which are two extendable parts that can be extended and contracted independently. Part. The expansion / contraction direction force generation unit (hereinafter abbreviated as expansion / contraction force generation unit) generates an expansion / contraction direction force by supplying electric power to the electric working machine, and generates electric power by the electric operation machine to generate resistance to expansion / contraction ( It is possible to generate at least one of generating a stretching direction force. In other words, the electric machine of this section can be, for example, a generator, or can function as both an electric motor and a generator.
The expansion / contraction direction force generated by the expansion / contraction force generation unit includes an unsprung damping force component. This unsprung damping force component can be, for example, the product of the displacement rate of the unsprung portion and the damping coefficient.
The damping force generation unit can be provided, for example, between the expansion / contraction force generation unit and the unsprung portion and is passively expanded / contracted to generate a damping force due to the influence of the expansion / contraction direction force and the displacement of the unsprung portion. Then, for example, the unsprung damping force component of the expansion / contraction direction force is transmitted to the lower part of the spring via the damping force generation part, and the spring is generated by the damping force generated by expanding and contracting the damping force generation part by the displacement of the lower part of the spring. Lower vibration is attenuated. In other words, the unsprung part is damped by the unsprung damping force component and the damping force, and for example, fluctuations in the ground load can be suppressed. In addition, for example, the electrically operated machine can include a linear motion element or a rotor, and the expansion / contraction force generation unit can include a motion conversion device. And since the components such as the electric machine and the motion conversion device become inertial mass with respect to expansion and contraction, even if the expansion and contraction direction force is not generated, a damping force is generated by the damping force generation unit, and the spring The lower part can be controlled.
That is, for damping the unsprung portion, two elements are involved: the unsprung damping force component of the expansion / contraction direction force and the damping force of the damping force generator. As will be described in detail later, the degree of vibration suppression of the unsprung portion can be changed by changing these two elements.
By the way, the unsprung damping force component of the expansion / contraction direction force and the damping force of the damping force generation unit cannot always be appropriately set. For example, as will be described later, one of the unsprung damping force component of the expansion / contraction direction force and the damping force of the damping force generator is reduced due to heat generation or lack of power, etc., so that the stretching force generator and the damping force generator A situation may arise where it is desirable to alleviate the burden on one. For example, when driving on a rough road, the road surface input becomes large, so the unsprung damping force component and the sprung damping force component are increased, and the stretching direction force generated by the stretching force generation unit is increased. As a result, for example, the amount of power consumption increases, and the temperature of the electrically operated machine may increase excessively, or the amount of electricity stored in the storage battery may excessively decrease. Moreover, the temperature of the damping force generation part may rise excessively.
When the temperature of the electric working machine rises excessively, the power consumption of the electric working machine can be reduced by reducing the unsprung damping force component, and the temperature rise of the electric working machine can be suppressed. That is, it is possible to reduce the load on the stretch force generation unit. However, simply reducing the unsprung damping force component reduces the degree of vibration suppression of the unsprung part, and increases, for example, ground contact load fluctuation.
On the other hand, the damping load changing unit of this section suppresses a decrease in the degree of damping of the unsprung portion by increasing the damping force of the damping force generating unit, for example, when reducing the load of the stretching force generating unit. be able to. Conversely, when reducing the load on the damping force generation unit, the damping force of the damping force generation unit is reduced and the unsprung damping force component is increased to suppress a decrease in the degree of damping of the unsprung portion. can do. That is, according to the aspect of this section, a more practical electric suspension system can be obtained.
The configuration of the damping force generation unit is not particularly limited as long as the magnitude of the damping force can be changed, and can include, for example, a hydraulic damper with a variable damping force. Further, in order to change the magnitude of the damping force, the damping characteristic can be changed by changing the flow area of the working fluid of the hydraulic damper, for example, by a variable throttle or the like. That is, changing the magnitude of the damping force means changing the magnitude of the damping force for the same expansion / contraction speed, such as increasing the damping coefficient. The magnitude of the damping force for the same expansion / contraction speed can be referred to as “attenuation capacity” or “attenuation intensity”.
(2) When the damping load changing unit is in a state where it is necessary to reduce a load that is highly necessary to reduce one of the stretching direction force generation unit and the damping force generation unit, the expansion direction force generation unit The electric suspension system for a vehicle according to item (1), wherein one of an unsprung damping force component and a damping force of the damping force generation unit is reduced.
Usually, the unsprung damping force component and the damping force of the damping force generator are changed, for example, to change the riding comfort or running stability of the vehicle in accordance with the running state or the driver's selection. However, it may be necessary to change the unsprung damping force component, damping force, or the like for purposes other than the original purpose. For example, as will be described later, when one of the temperature of the expansion / contraction direction force generation unit and the temperature of the damping force generation unit exceeds the set temperature, or when the power to be supplied to the electric machine is insufficient, etc. The necessity of reducing one burden of the expansion / contraction direction force generation part and the damping force generation part becomes high.
In other words, the burden reduction necessary state is not the original necessity of changing the riding comfort or running stability of the vehicle, but the necessity of protecting the component parts or the necessity of suppressing the consumption of power has increased. State. For this reason, even if the burden on one of the expansion / contraction direction force generation unit and the damping force generation unit is reduced, it is desirable to suppress a decrease in the degree of damping of the unsprung portion.
On the other hand, according to the attenuation load changing unit of this section, it is possible to reduce the load on the expansion / contraction direction force generation unit and the like while suppressing a decrease in the degree of vibration suppression of the unsprung portion in the state of reducing the load.
(3) The attenuation burden changing unit is
When one of the temperature of the stretching direction force generation unit and the temperature of the damping force generation unit exceeds the set temperature, the unsprung damping force component and damping force of the stretching direction force generation unit exceed the set temperature. While reducing one of the damping force of the generating unit and increasing the other of them, a temperature corresponding load changing unit,
A power corresponding load changing unit that decreases an unsprung damping force component of the expansion / contraction direction force generation unit and increases a damping force of the damping force generation unit when power to be supplied to the electric machine is insufficient. The electric suspension system for vehicles according to item (1) or (2), including at least one.
The mode of this section is a mode that shows a specific example of the burden reduction necessary state. An excessive temperature rise in the expansion / contraction direction force generation unit and a shortage of electric power may occur, for example, during the above-described rough road traveling or roll suppression control. When traveling on a rough road, it is the same as described above. During roll restraint control, expansion / contraction direction force including roll restraining force that cancels roll moment is generated. However, when a large roll restraining force is generated for a relatively long time, the temperature exceeds the set temperature. Or there may be a shortage of power. In such a case, by reducing the unsprung damping force component and increasing the damping force of the damping force generation unit, it is possible to suppress temperature rise and power consumption while suppressing a decrease in the degree of damping of the unsprung portion. . On the other hand, the temperature of the damping force generation unit exceeding the set temperature may occur, for example, when traveling on a rough road.
In the expansion / contraction direction force generation unit, the electric working machine is mainly a heat generation source, and therefore the temperature of the electric operation machine can be set to the temperature of the expansion / contraction direction force generation unit.
(4) The control device includes the unsprung damping force component including a product of a displacement rate of the unsprung portion in the approaching / separating direction, which is a direction in which the sprung portion and the unsprung portion approach and separate, and a set damping coefficient. Including an expansion / contraction direction force determining unit for determining the expansion / contraction direction force;
The vehicular electricity according to any one of (1) to (3), wherein the damping load changing unit includes a damping coefficient changing unit that changes the unsprung damping force component by changing the damping coefficient. Suspension system.
By changing the damping coefficient, the unsprung damping force component can be easily changed. Note that, as will be described in detail later, the attenuation coefficient can be changed according to the displacement speed.
(5) The expansion / contraction direction force determination unit determines an expansion / contraction direction force including the unsprung damping force component and a sprung damping force component that attenuates vibration of the sprung portion.
The electric suspension system for a vehicle according to item (4), wherein the damping load changing unit reduces the load on the expansion / contraction direction force generating unit without reducing the sprung damping force component.
When reducing the load on the expansion and contraction force generation unit, it is possible to suppress a decrease in the degree of damping of the sprung portion by reducing the unsprung damping force component without reducing the sprung damping force component.
In addition, although it is different from the aspect of this section, when reducing the load of the expansion and contraction force generation unit, the sprung damping force component may be reduced together with the unsprung damping force component. In this case, it is possible to increase the burden reducing effect of the stretch force generation unit.

(6) The approaching / separating direction force generation device is provided in series with the expansion / contraction direction force generation unit and in parallel with the damping force generation unit, and generates an elastic force generation unit that generates an elastic force according to an elastic deformation amount. The vehicle electric suspension system according to any one of items (1) to (5).
The elastic force generation part of this term can include, for example, a spring member such as a coil spring or a leaf spring, a gas spring using a gas such as air, or the like. A portion that includes the damping force generation unit and the elastic force generation unit and is connected in series with the expansion / contraction direction force generation unit and can be passively expanded and contracted can be referred to as a passive expansion / contraction unit.
When the elastic force generation part and the damping force generation part in this section are arranged between the stretch force generation part and the unsprung part, the inertial mass, the elastic force generation part, and the damping force with respect to the expansion and contraction of the stretch force generation part A so-called dynamic damper is constituted by the generating portion and the like, and even if there is no expansion / contraction direction force, the vibration of the unsprung portion can be effectively suppressed.
(7) The damping force generator is
A hydraulic damper that generates a resistance force according to its expansion / contraction speed by a passage resistance when the hydraulic fluid passes through the liquid passage;
Provided in the hydraulic damper, including a passage resistance changing portion for changing the passage resistance of the fluid passage,
The damping load changing unit includes a passage resistance control unit that changes the damping force of the damping force generation unit by changing the passage resistance of the liquid passage by controlling the passage resistance changing unit. The electric suspension system for a vehicle according to any one of (6).
In the aspect of this section, for example, the passage resistance of the hydraulic fluid is increased by reducing the flow path area, and the resistance force can be easily increased. Further, for example, as will be described in detail in a later embodiment, since the passage resistance changing portion can be provided in the piston of the damper, it is possible to suppress an increase in the size of the approaching / separating force generator.
(8) The damping force generator is
A magnetic reactive damper that uses a magnetic reaction viscous fluid, which is a fluid in which particles having ferromagnetism are dispersed in a liquid, as a working fluid, and generates resistance to expansion and contraction by the flow resistance of the magnetic reaction viscous fluid;
A magnetic field generator for generating a magnetic field that acts on the magnetic reaction viscous fluid,
The attenuation load changing unit includes a magnetic field strength control unit that changes the damping force of the damping force generation unit by changing the strength of the magnetic field by controlling the magnetic field generation unit (1) to (7) The electric suspension system for vehicles according to any one of items 1).
The magnetic reaction viscous fluid can include, for example, a magnetorheological fluid (sometimes referred to as an MR fluid) in which fine particles having an average particle size of about several μm are dispersed in a liquid such as oil. Further, for example, it may include a magnetic fluid in which fine particles having an average particle diameter of about 10 nm are dispersed in a liquid such as oil. The magnetic reaction viscous fluid flows in the same manner as a normal liquid in the absence of a magnetic field, but when a magnetic field acts, a crosslinked structure is formed between a plurality of particles and the viscosity increases.
The magnetic field generator can have an electromagnet, for example. By adjusting the strength of the magnetic field applied by the magnetic field generator, the viscosity of the magnetic reaction viscous fluid can be adjusted, and the damping force of the damper can be changed.
(9) The electric working machine is a rotating electric machine that has a rotor and can generate a rotating torque by generating electric power when the rotor is rotated by an external force;
The expansion / contraction direction force generator is
A relative moving body capable of linear motion relative to the rotating electrical machine;
A motion conversion device that converts the linear motion of the relative motion body into the rotational motion of the rotor, and the relative motion body expands and contracts by a relative linear motion, and in the expansion and contraction direction by the rotational torque of the rotating electrical machine. The electric suspension system according to any one of items (1) to (8), which generates an expansion / contraction direction force that is a force.
In the aspect of this section, the mass equivalent to the rotation inertia moment of the rotating part of the rotating electric machine and the rotating part of the motion conversion device and the inertial mass of the relative moving body are included in the inertial mass with respect to the expansion and contraction of the expansion / contraction force generation unit. . The motion conversion device of this section can include, for example, a ball screw, a pinion and a rack, or the like.

  Embodiments of the claimable invention will be described below with reference to the drawings. In addition to the following examples, the claimable invention can be practiced in various modifications based on the knowledge of those skilled in the art, including the aspects described in the above [Aspect of the Invention] section. .

FIG. 1 schematically shows an outline of an electric suspension system for a vehicle (hereinafter simply abbreviated as “suspension system” unless otherwise required) as an embodiment of the claimable invention. In this embodiment, the suspension system includes four suspension devices 10, and each of the four wheels 12 and each of the four portions of the vehicle body 14 are connected to each other so as to be able to approach and separate by the four suspension devices 10. .
The suspension device 10 is provided between the wheel 12 and the vehicle body 14, and the approach / separation direction force generation device 20 that generates a force in the direction in which the wheels 12 approach and separate from each other and the approach / separation direction force generation device 20 are connected to the vehicle body 14. And a lower support 24 connected to a wheel holding portion that rotatably holds the wheel 12. The wheel holding unit 26 includes a wheel holding member such as a steering knuckle that rotatably holds the wheel, a lower arm 28 (see FIG. 15) that is connected to the vehicle body and supports the wheel holding member so as to move up and down. .
In this embodiment, the axial direction of the approach / separation direction force generator 20 (hereinafter, abbreviated as the approach / separation force generator unless otherwise required), that is, the direction in which the upper support 22 and the lower support 24 approach and separate. Is the expansion / contraction direction of the approaching / separating force generator 20. In this embodiment, the expansion / contraction direction is a direction including a component in a direction in which the wheel 12 and the vehicle body 14 approach and separate from each other.

  FIG. 2 is a front sectional view of a part of the suspension device 10. The upper support 22 includes an annular mount rubber 30 that is an impact absorber, and an upper contact plate 34 that is joined to the upper portion of the mount rubber 30 and is brought into contact with the vehicle body 14. The upper contact plate 34 is provided with a plurality of stud bolts 36 for fastening the upper support 22 to a part of the vehicle body 14 (specifically, a suspension tower).

The approaching / separating force generator 20 includes a control expansion / contraction direction force generation unit 40 (hereinafter abbreviated as an expansion / contraction force generation unit unless otherwise required) that generates an expansion / contraction direction force according to a control command, and the expansion / contraction force generation unit 40 and the lower An unsprung vibration suppressing portion 42 provided in series with the support 24 and a main spring 44 that generates an elastic force in a direction to separate the upper support 22 and the lower support 24 are provided.
The main spring 44 is composed of a compression coil spring that is a spring. The disk-shaped upper support member 50 that extends to the outer peripheral side of the expansion / contraction force generation unit 40 and the disk-shaped lower side that extends to the outer peripheral side of the unsprung vibration suppression unit 42. It is sandwiched between the support member 52. That is, the main spring 44 is disposed in parallel with the expansion / contraction force generation unit 40 and the unsprung vibration suppression unit 42 and generates an elastic force that supports the vehicle body 14.

The expansion / contraction force generation unit 40 includes a rotary electric machine 60 that is an electric operation machine, a ball screw device 62 that is a motion conversion device, and a generally cylindrical base 64. The base 64 extends in the expansion and contraction direction, penetrates the center of the upper support member 50, and is provided in a state of protruding above the upper support 22. A rotary electric machine 60 is disposed on the upper inner peripheral side of the base body 64, and a ball screw device 62 is disposed on the lower inner peripheral side.
The rotary electric machine 60 includes a hollow rotary shaft 72 rotatably supported on a base 64 via a ball bearing, a rotor 74 fixed to the rotary shaft 72, a stator fixed to the base 64 and facing the rotor 74. 76. Further, while the rotor 74 is configured by a permanent magnet, the stator 76 is configured by an electromagnet, and the rotary electric machine 60 is configured on the basis of a brushless DC motor, but not only as an electric motor but also as a generator. Is also called a rotating electric machine.

The ball screw device 62 includes a rotary motion unit 82 that is rotatably provided on the base body 64, a screw rod 84 that is a relative motion body screwed into the rotary motion unit 82, and prevents the screw rod 84 from rotating. Rotation prevention part 86.
On the outer peripheral surface of the screw rod 84, a spiral thread groove 90 that forms a raceway on which a large number of bearing balls (hereinafter abbreviated as “balls” unless otherwise required) rolls, and an axial spline groove 92 is formed. Then, the screw rod 84 is screwed into the rotational movement portion 82 via a large number of balls in the screw groove 90, and is engaged with the rotation prevention portion 86 via the balls in a non-rotatable and relatively movable manner via the balls. It has been made. The rotation blocking portion 86 may be configured to block the rotation of the screw rod 84 without using the spline nut 96.
The rotary motion part 82 is provided with a nut holding part 93 formed at the tip part of the rotary shaft 72 and a screw nut 94 held in the nut holding part 93 so as not to move. On the inner peripheral side of the screw nut 94, an outer peripheral side thread groove facing the thread groove 90 is formed. Further, the rotation preventing portion 86 is constituted by a spline nut 96 in which an outer peripheral spline groove facing the axial spline groove 92 is formed. Each of the screw nut 94 and the spline nut 96 includes a ball circulation portion that scoops up a ball that rolls along a track from a set location and guides it to another location.
By the ball screw device 62 described above, the rotational motion of the rotary electric machine 60 and the linear motion of the screw rod 84 are mutually converted. In this embodiment, the ball screw device 62 constitutes a “motion converting device”. In addition, the “relatively moving body” is configured by the screw rod 84. The screw rod 84 is also a component of the ball screw device 62.

The unsprung vibration suppression unit 42 as a passive expansion / contraction unit is provided between the expansion / contraction force generation unit 40 and the lower support 24 so as to be expandable / contractible. Further, on the vehicle body 14 side, it is connected to the tip end portion of the screw rod 84 of the expansion / contraction force generation unit 40, and moves relative to the vehicle body 14 together with the screw rod 84.
The unsprung vibration suppression unit 42 is provided with an elastic force generation unit 100 and a damping force generation unit 102. The elastic force generator 100 includes two compression coil springs 104 and 106 (a kind of spring, hereinafter abbreviated as “spring”) arranged in series in the axial direction, and the two springs 104 and 106. A transmission member 108 that transmits the displacement of the screw rod 84 and a cylindrical member 109 that supports the spring 104 from above are provided. The transmission member 108 has a cup shape that opens to the wheel 12 side, and includes a flange portion 110 that extends to the outer peripheral side. The bottom portion is attached to the tip of the screw rod 84 and the flange portion 110 is sandwiched between the two springs 104 and 106. On the other hand, the ends of the springs 104 and 106 are brought into contact with the upper end of the cylindrical member 109 and the lower support member 52, respectively, and are prevented from moving in the axial direction. As a result, when the transmission member 108 and the housing 98 are relatively moved in the axial direction, one of the springs 104 and 106 is compressed and an elastic force is generated.

  In the present embodiment, the damping force characteristic of the damping force generation unit 102 of the unsprung vibration suppression unit 42 can be changed. The damping force generator 102 is disposed on the inner peripheral side of the spring 106, passes through the center of the lower support member 52, and is connected to the lower support 24.

The damping force generator 102 includes a shock absorber 114 that is a hydraulic damper. The shock absorber 114 has a single cylinder type, a cylinder 120 filled with oil as a working fluid, a piston 122 disposed in the cylinder 120, a piston 122 attached to one end, and the other end. The piston rod 124 is connected to the end of the screw rod 84, and the free piston 126 is movably fitted to the lower portion of the cylinder 120. The lower side of the free piston 126 is filled with high-pressure gas, and the movement of the free piston 126 allows a change in volume on the upper side of the cylinder 120.
FIG. 3 is a front sectional view of the piston 122 portion of the shock absorber 114. As shown in the figure, a hard valve 130 is provided at the bottom of the piston 122 and a soft valve 132 is provided at the top. The hard valve 130 and the soft valve 132 are respectively provided with annular leaf valves 134 and 136, and when the shock absorber 114 is contracted, the outer peripheral portion is bent upward so that the lower chamber 140 is changed to the upper chamber 142. Allow the oil to flow toward On the other hand, when the shock absorber 114 is extended, the inner peripheral portion is bent downward to allow oil to flow from the upper chamber 142 toward the lower chamber 140. Since the leaf valve 134 of the hard valve 130 is small in diameter, it is difficult to bend and the passage resistance is increased. Further, in the figure, a bypass passage, which will be described later, is closed and the damping coefficient is large, and the oil is allowed to pass through the liquid passage 144 passing through both the hard valve 130 and the soft valve 132. A state in which the damping force is large and strong, that is, the damping force is maximized. Note that the damping force maximum state can also be referred to as a “damping capacity maximum state”.
The piston rod 124 has a hollow shaft, and a piston support portion 148 is attached to the tip of the shaft portion 146. A control rod 150 is inserted into the piston rod 124. The control rod 150 is held in the large diameter portion 152 so as to be rotatable through a bearing and immovable in the axial direction. Further, the front end portion 154 of the control rod 150 is formed with a notch 156 in the radial direction. In this figure, a radial hole 162 that connects the axial hole 160 of the piston rod 124 and the portion of the liquid passage 144 between the hard valve 130 and the soft valve 132 is formed by the tip 154 of the control rod 150. It is blocked.
However, when the rotational position of the control rod 150 is changed, as shown in FIG. 4 which is a plan sectional view of the tip 154 (II sectional view in FIG. 3), the axial hole 160 and the radial hole 162 are Are communicated to form a bypass passage 164. As a result, since at least a part of the oil does not need to pass through the hard valve 130 having a large passage resistance, the passage resistance is relatively small and the damping force is weaker than the high damping force state. By changing the degree of overlap between the notch 156 and the radial hole 162, the flow passage area of the bypass passage 164 can be changed, and the damping force characteristic can be changed in multiple steps or continuously. Normally, the rotational position of the control rod 150 is set to the position shown in the figure, and the damping force characteristic is set to the “medium damping force state” having a moderate magnitude for normal running.
In the present embodiment, the control rod 150, the axial hole 160, and the radial hole 162 constitute a flow path resistance changing device 170 of the shock absorber 114.

A rotational position changing device 180 that changes the rotational position of the control rod 150 of the flow path resistance changing device 170 is provided above the approaching / separating force generating device 20. The rotational position changing device 180 includes a driving unit 182 and a hollow hollow rotating shaft 184 that is rotated by the driving unit 182. The drive unit 182 is provided with a step motor and a speed reduction mechanism that decelerates the rotation of the step motor.
As shown in FIG. 5, the screw rod 84 is hollow, and a through hole 186 that linearly penetrates from the upper end of the screw rod 84 to the lower end of the piston rod 124 is formed. The hollow rotary shaft 184 is inserted into the screw rod 84, and the upper portion of the control rod 150 is inserted into the axial hole 188 of the hollow rotary shaft 184. An engagement groove 190 is formed in the axial hole 188 along the axial direction, and a key 192 that engages with the engagement groove 190 is attached to the upper end portion of the control rod 150. Since the keys 192 and the engagement groove 190 are engaged so as to be relatively movable in the axial direction and not to be relatively movable in the circumferential direction, the hollow rotary shaft 184 and the control rod 150 are relatively moved in the axial direction. It is possible and connected so that it cannot rotate relative to it.

  As described above, the elastic force generator 100 and the damping force generator 102 are provided in parallel between the screw rod 84 and the lower support 24. Therefore, in the unsprung vibration suppressing portion 42, an elastic force corresponding to the relative displacement amount and a resistance force (that is, a damping force) corresponding to the relative displacement speed with the relative movement between the lower support member 52 and the screw rod 84. Occur at the same time and suppress the vibration of the unsprung part.

A portion where the unsprung vibration suppressing portion 42 and the tip of the screw rod 84 are connected is referred to as a connecting portion 194.
A first temperature sensor 196 that detects the temperature of the stator 76 of the rotary electric machine 60 is provided on the upper portion of the base body 64. A second temperature sensor 198 for detecting the temperature of the cylinder 120 is provided on the side surface of the shock absorber 114. The temperature sensors 196 and 198 are composed of thermocouples, but other sensors such as a thermistor can also be used. The second temperature sensor 198 is configured such that the thermocouple is brought into contact with the outer peripheral surface of the cylinder 120 and the portion other than the contact surface is covered with a heat insulating case so that the temperature of the cylinder 120 can be accurately detected. ing. The signal line 199 of the second temperature sensor 198 is disposed along a lower arm (not shown), passes through the vehicle body wall, is drawn into a vehicle body such as an engine room, and is connected to an ECU described later.

  The approaching / separating force generating device 20 of the suspension system is controlled by an electronic control unit 200 (hereinafter sometimes simply referred to as “ECU 200”) shown in FIG. The ECU 200 is mainly configured by a computer having a CPU, a ROM, a RAM, and the like. The ECU 200 also includes an unsprung acceleration sensor 210 (shown as “Ga” in the drawing) for detecting the vertical acceleration of the vehicle body 14 and an unsprung acceleration sensor 212 (shown as “Gb” in the drawing) for detecting the vertical acceleration of the unsprung portion. ), A vehicle speed detection device 214 for detecting the vehicle speed, a lateral acceleration sensor 216 for detecting the lateral acceleration of the vehicle body (shown as “lateral G sensor” in the figure), a steering angle sensor 218 for detecting the operation angle of the steering wheel as the operation member, Various detection devices such as a rotation angle sensor 220 for detecting the rotational position of the rotor 74, the first temperature sensor 196, the second temperature sensor 198, and a voltmeter 226 for detecting the voltage of the battery are connected.

The ECU 200 is connected to an electronic drive unit 230 (hereinafter abbreviated as EDU) which is an electronic drive device. The EDU 230 receives power supplied from a direct current transformer 234 (also referred to as a DC-DC converter, which is described as “CONV” in the drawing) that transforms the power of the storage battery 232, and supplies power to the rotating electrical machine 60 in accordance with a command from the ECU 200. Supply.
Specifically, the EDU 230 is a kind of power adjustment device, has an inverter circuit, and performs pulse width modulation control (PWM control) by turning on and off a plurality of switching elements by a controller (not shown). Thus, the electric power flowing between the DC transformer 234 and the rotary electric machine 60 is adjusted. Then, a driving power is supplied to the three-phase coil included in the stator 76 of the rotating electric machine 60 or power is generated by the rotating electric machine 60 to generate a stretching force. In addition, the EDU 230 includes a resistor and a switching element, and includes a power consumption circuit (not shown) that consumes the power generated by the rotating electrical machine 60 as necessary.
Note that the DC transformer 234 is a non-insulated type and has a switching element, a reactor, a capacitor, a diode, etc., and drops the voltage of the storage battery 232 by chopper control of the switching element composed of IGBT, MOSFET, etc. In addition, the electric power generated by the rotating electrical machine 60 is boosted and regenerated in the storage battery 232. Note that the DC transformer 234 can change the output voltage, but the maximum value of the output voltage is determined, and power below the set maximum voltage can be output.
Furthermore, the ECU 200 is connected to a drive circuit 240 that drives the rotational position changing device 180. The drive circuit 240 supplies power to the drive unit 182 of the rotational position changing device 180 in accordance with a command from the ECU 200, changes the rotational position of the control rod 150, and changes the damping force of the shock absorber 114.

  The ECU 200 includes an output control unit 260 and an attenuation load changing unit 262 as functional units. The output control unit 260 rotates in accordance with a control expansion / contraction direction force F to be generated by the expansion / contraction force generation unit 40 of each of the four approach / separation force generation devices 20 (hereinafter, abbreviated as expansion / contraction force F unless otherwise required). The damping load changing unit 262 is a part that determines the output value of the electric machine 60. The damping load changing unit 262, as will be described in detail later, is a process of changing the load related to the damping of the unsprung portion between the stretching force generating unit 40 and the damping force generating unit 102. It is a part to do.

The determination of the output value of the rotating electric machine 60 by the output control unit 260 serving as the expansion / contraction direction force determination unit will be briefly described.
Each stretching force F is a value obtained by adding a damping term Fa that suppresses vibration in the approaching / separating direction and an attitude control term Fb that suppresses a change in attitude of the vehicle body, as shown in the following equation.
F = Fa + Fb (1-1)
Here, the damping term Fa is multiplied by a sprung gain Ca that is a coefficient set to the vertical displacement speed Xva of the vehicle body 14 obtained based on the detection value of the sprung acceleration sensor 210 as shown in the following equation. The unsprung damping force obtained by multiplying the unsprung damping force by the unsprung gain Cb, which is a coefficient set to the vertical displacement speed Xvb of the unsprung portion obtained based on the detection value of the unsprung acceleration sensor 212, is obtained. The
Fa = Ca · Xva−Cb · Xvb (1-2)
The attitude control term Fb is a term for suppressing the roll and pitch of the vehicle body 14, and is a value obtained by adding the roll suppression force and the pitch suppression force. The roll restraining force is a value obtained by multiplying the control lateral acceleration acquired based on the detection values of the lateral acceleration sensor 216, the steering angle sensor 218, and the vehicle speed detection device 214 by a set coefficient. By this roll restraining force, the separating force on the turning outer wheel side is increased and the separating force on the turning inner wheel side is reduced, thereby suppressing the roll of the vehicle body. The pitch suppression force is a value obtained by multiplying the longitudinal acceleration acquired based on the detection value of the vehicle speed detection device 214 by a set coefficient. Due to this pitch restraining force, the descending side (for example, the front side during braking) is increased and the ascending side separating force is decreased, and the pitch of the vehicle body 14 during acceleration / deceleration is suppressed.
After the output value corresponding to the control expansion / contraction direction force F is determined as described above, an instruction is issued to the EDU 230, and appropriate electric power is supplied from the EDU 230 to the rotating electric machine 60, or the rotating electric machine 60 is passively operated. Power generation by rotation is allowed, and an approaching / separating force corresponding to the output value is generated.

FIG. 6 shows a single-wheel model of the suspension device 10.
In this figure, the sprung portion includes a part of the vehicle body 14 corresponding to one wheel 12 and a part that moves up and down together with the part, for example, an upper contact plate 34 of the upper support 22 and a stud bolt 36. The unsprung portion is a portion that moves up and down together with the axis of the wheel 12, and includes the wheel holding portion 26, most of the wheel 12, the lower support 24, the lower support member 52, and the like. “Kc” is a spring constant of the main spring 44, K ₀ is a spring constant of the tire portion of the wheel 12, and “Rc” is a friction coefficient with respect to relative movement between the spring top and the spring bottom. “Ku, Cu” are a spring constant and a damping coefficient of the mount rubber 30 of the upper support 22, respectively.
The drive unit is a portion that moves up and down together with the upper support member 50, and includes a base 64, a rotary electric machine 60, a screw nut 94, a spline nut 96, and the like. The relative moving part is a part that moves up and down together with the screw rod 84, and includes the transmission member 108, the piston rod 124, the piston 122, etc. of the unsprung vibration suppressing part 42.
“F” is an expansion / contraction force, and “Ra” is a friction coefficient when the expansion / contraction force generation unit 40 is expanded / contracted. “Id” is the inertia in the expansion / contraction direction (extension / contraction inertia) generated by the moment of inertia generated when the expansion / contraction force generating unit 40 expands / contracts, and the inertia of the rotating portion including the rotation shaft 72, the rotor 74, the screw nut 94, and the like. This is the inertia in the expansion and contraction direction equivalent to the moment. “Kt” is a spring constant of the elastic force generation unit 100, “Ct” is a damping coefficient of the damping force generation unit 102, and “Ra” is a friction coefficient during expansion / contraction of the unsprung vibration suppression unit 42.
The differential value of the sprung displacement X ₂ of this model corresponds to the sprung displacement speed Xva when calculating the sprung damping force component (Ca · Xva) in the above equation (1-2). Similarly, the differential value of the unsprung displacement X ₁ corresponds to the unsprung displacement speed Xvb when the unsprung damping force component (Cb · Xvb) is calculated.

FIG. 7 shows equations of motion (2-1) to (2-4) of the above model.
8 and 9 show examples of changes in the ground load variation of the wheel 12 when the unsprung gain and the damping force of the damping force generator 102 are changed. That is, it shows a change in the unsprung vibration suppression degree. The graphs of FIGS. 8 and 9 simulate fluctuations in the difference between the unsprung displacement X ₁ and the road surface displacement X ₀ when the frequency of the vibration input to the road surface displacement X ₀ in the equation (2-4) is changed. It is an example of the result. That is, the variation of the deformation amount of the tire portion of the wheel 12 is acquired by the simulation, and the larger the variation of the deformation amount, the larger the contact load variation.
FIG. 8 shows changes in the ground load variation when the unsprung gain Cb is kept small and the damping force of the damping force generator 102 is changed. In this figure, when the damping force is increased, that is, when the damping force is increased, the ground load fluctuation is indicated by a solid line. When the damping force is increased, the rotational position of the control rod 150 is changed to reduce the flow passage area of the bypass passage 164. The damping force is larger than the middle damping force state and smaller than the damping force maximum state. Put into a state. Further, when the damping force is reduced, that is, when the damping force is reduced, the ground load fluctuation is indicated by a broken line. When the damping force is reduced, the rotational position of the control rod 150 is changed to make the damping force smaller than the middle damping force state.
An intermediate value between the ground load fluctuation when the damping force increases and the ground load fluctuation when the damping force decreases is indicated by a two-dot chain line. It is estimated that the ground load fluctuation indicated by the two-dot chain line has the same tendency as the ground load fluctuation in the medium damping force state described above. Therefore, for the sake of convenience, it is assumed that the ground load fluctuation indicated by a two-dot chain line is a ground load fluctuation when the unsprung gain Cb is reduced and the damping force is set to the middle damping force state.
FIG. 9 shows changes in the ground load variation when the damping force of the damping force generator 102 is kept small and the unsprung gain Cb is changed. In this figure, when the unsprung gain Cb is increased, that is, when the unsprung gain increases, the ground load fluctuation is indicated by a solid line. In addition, when the unsprung gain Cb is reduced, that is, when the unsprung gain is decreased, the ground load fluctuation is indicated by a broken line.
An intermediate value between the ground load variation when the unsprung gain increases and the ground load variation when the unsprung gain decreases is indicated by a two-dot chain line. The ground load fluctuation indicated by the two-dot chain line is presumed to have the same tendency as the ground load fluctuation when the unsprung gain Cb is set to the normal set value which is the set value for normal travel. Therefore, for convenience, the ground load fluctuation indicated by the two-dot chain line is a ground load fluctuation when the damping force of the damping force generation unit 102 is reduced and the unsprung gain Cb is set to the normal setting value. To do.

In the above graph, when both the unsprung gain Cb of the stretching force and the damping force of the damping force generation unit 102 are reduced, the ground load fluctuation increases the peaks A and B in the two frequency regions. The valley tends to deepen. Further, when either the unsprung gain Cb of the expansion / contraction force or the damping force of the damping force generator 102 is increased, the peaks in the two frequency regions tend to decrease and the valleys tend to become shallow. That is, when the unsprung gain Cb is changed and when the damping force is changed in a state where at least one of the unsprung gain Cb and the damping force is reduced, the change in the ground load variation is almost the same. Indicates. A state in which the peaks A and B of the ground load fluctuation are large is a state in which the degree of vibration suppression is reduced, and a state in which the peaks A and B are small is a state in which the degree of vibration suppression is good. That is, the state indicated by the solid line in the graph is a state in which the degree of vibration suppression is good. That is, when one of the unsprung gain Cb and the damping force is reduced, a tendency that the decrease in the degree of damping of the unsprung portion can be suppressed by increasing the other of them is recognized.
As shown in the above example, when one of the unsprung gain Cb and the damping force is reduced in order to reduce the burden on one of the stretching force generation unit 40 and the damping force generation unit 102, these unsprung portions. By increasing the other of the gain Cb and the damping force, the ground load fluctuation peaks A and B can be reduced and the characteristics can be made gentle. That is, it is possible to suppress a decrease in the degree of damping of the unsprung portion.
As described above, when the unsprung gain Cb is decreased, the decrease in the degree of damping of the unsprung portion can be suppressed by increasing the damping force of the damping force generation unit 102 in the model of FIG. The inertia that combines the inertia of the part and the inertia moment Id of the rotary electric machine 60, etc., and the elastic force generator 100 and the damping force generator 102 constitute a mass / spring / damper system and function as a dynamic damper under the spring. It is presumed to be. And it is estimated that the damping effect as a dynamic damper increases with the increase in damping force.
On the other hand, when the damping force of the damping force generation unit 102 is decreased, the decrease in the degree of vibration suppression of the unsprung portion can be suppressed by increasing the unsprung gain Cb. The unsprung damping force component generated by the generating unit 40 is transmitted to the lower part of the spring through the elastic force generating part 100 and the damping force generating part 102 of the unsprung vibration suppressing part 42 to attenuate the vibration of the unsprung part. Guessed.
In the above simulation, the damping characteristic of the damping force generator 102 is a linear characteristic, and the expansion side and the contraction side are the same. On the other hand, the damping characteristic of the damping force generation unit 102 of the present embodiment is a non-linear characteristic and the contraction side is reduced. However, when one of the unsprung gain Cb and the damping force is reduced, these springs are reduced. By increasing the other of the lower gain Cb and the damping force, it is possible to suppress a decrease in the degree of damping of the unsprung portion.

In FIG. 10, when one of the expansion force generation unit 40 and the damping force generation unit 102 generates heat or power is insufficient, the above one load is reduced while suppressing a decrease in the degree of vibration suppression of the unsprung portion. The flowchart of an attenuation burden reduction program is shown. In the present embodiment, four attenuation burden reducing programs corresponding to the four approaching / separating force generation devices 20 are executed in parallel at the same time by the time division process in the computer of the ECU 200. Since the four programs are configured in the same manner, one program will be described as a representative.
In step 11 (hereinafter abbreviated as S11), various detection values are acquired. Specifically, the first temperature T1 that is the temperature of the rotating electrical machine 60 is acquired based on the detection value of the first temperature sensor 196, and the second temperature T2 that is the temperature of the shock absorber 114 is the second temperature sensor. The voltage E of the storage battery 232 is acquired based on the detection value of the voltmeter 226.
In S <b> 12 to S <b> 15, when the voltage E of the storage battery 232 becomes equal to or lower than the threshold voltage, a process of reducing the power consumption by reducing the attenuation load of the stretching force generation unit 40 is performed. The threshold voltage is set to be larger than the stretching force insufficient voltage, which is a voltage at which sufficient electric power cannot be supplied to the rotating electrical machine 60 and the desired stretching force cannot be obtained.
When the voltage E becomes equal to or lower than the threshold voltage, the unsprung gain is reduced in S14 and S15. In S13, it is determined whether or not the load on the damping force generator 102 can be increased. . That is, in S13, it is determined whether or not the second temperature T2 of the shock absorber 114 is equal to or lower than the second threshold temperature. When the second temperature T2 exceeds the second threshold temperature, the amount of heat generated by the shock absorber 114 is large, and the damping force of the damping force generator 102 is reduced in order to suppress the heat generation. On the other hand, when the second temperature T2 is equal to or lower than the second threshold temperature, the amount of heat generated by the shock absorber 114 is not large, and the damping force of the damping force generator 102 is increased, so that the degree of damping of the unsprung portion decreases. Is suppressed.

In S16 to S22, when at least one of the heat generation amounts of the stretching force generation unit 40 and the damping force generation unit 102 is large, a process of reducing the attenuation burden is performed. One of the four types of processing divided into the following cases is selected by the determination processing of S16 to S18.
(a) When the first temperature T1> the first threshold temperature and the second temperature T2> the second threshold temperature, the amount of heat generated by both the expansion force generation unit 40 and the damping force generation unit 102 is large. In S19, both the unsprung gain and the damping force of the damping force generation unit 102 are reduced, and the damping burden on both the stretching force generation unit 40 and the damping force generation unit 102 is reduced.
(b) When the first temperature T1> the first threshold temperature and the second temperature T2 ≦ the second threshold temperature, the heat generation amount of the stretching force generation unit 40 is large, and the heat generation amount of the damping force generation unit 102 In S20, the unsprung gain is decreased, while the damping force of the damping force generation unit 102 is increased, the damping load of the expansion / contraction force generation unit 40 is reduced, and the damping of the unsprung portion is suppressed. A decrease in the degree is suppressed.
(c) When the first temperature T1 ≦ the first threshold temperature and the second temperature T2> the second threshold temperature, the heat generation amount of the damping force generation unit 102 is large, and the heat generation amount of the expansion / contraction force generation unit 40 In step S21, the damping force of the damping force generation unit 102 is reduced, while the unsprung gain is increased, the damping load of the damping force generation unit 102 is reduced, and the vibration suppression of the unsprung portion is performed. A decrease in the degree is suppressed.
(d) When the first temperature T1 ≦ the first threshold temperature and the second temperature T2 ≦ the second threshold temperature, the heat generation amounts of both the expansion force generation unit 40 and the damping force generation unit 102 are small. Therefore, it is not necessary to suppress the heat generation. In S22, both the unsprung gain and the damping force of the damping force generator 102 are set for normal travel (indicated as “medium” in the figure). To be).
When both the unsprung gain and the damping force of the damping force generation unit 102 are set for normal running, one of the unsprung gain and the damping force is reduced, as in the graphs of FIGS. The two peaks A and B of the ground load fluctuation are smaller than in the case, and the characteristics are gentle.
The unsprung gain and the value of the damping force generator 102 when the damping force is increased are values that can moderately suppress the unsprung portion when the damping force or the unsprung gain of the damping force generator 102 is decreased. It is desirable to do. That is, when one of the unsprung gain and the damping force is decreased and the other is increased, it is desirable that the vibration suppression degree of the unsprung part becomes a target vibration suppression degree. The unsprung gain and the damping force for normal driving are set to be smaller than the above-described increase value and larger than the decrease value. As described above, when one of the unsprung gain and the damping force is reduced by providing a margin for the damping capacity of the expansion force generation unit 40 and the damping force generation unit 102, the other is more effectively performed. Can be suppressed to suppress a decrease in the degree of unsprung vibration suppression.
In the present embodiment, the first threshold temperature and the second threshold temperature are set lower than the temperatures at which the rotary electric machine 60 or the shock absorber 114 may be damaged, respectively, and a general pavement is used. The temperature is set higher than the temperature when the vehicle travels without sudden acceleration / deceleration or sudden turning. In this program, in S14, S15, and S19 to S22, the unsprung gain and the damping force of the damping force generator 102 are changed to the target values for each process, but they are already set to the target values. If so, that state is maintained.
With the above processing, when one of the expansion force generation unit 40 and the damping force generation unit 102 generates heat or when power is insufficient, the above one load is reduced while suppressing a decrease in the degree of vibration suppression of the unsprung portion. can do.

  In the damping load changing program, when both the stretching force generation unit 40 and the damping force generation unit 102 generate heat, both the unsprung gain and the damping force are reduced. It is also possible to increase the unsprung gain or damping force of the higher durability between the damping force generator 102 and the damping force generator 102. Specifically, for example, when the durability of the damping force generation unit 102 is high, even if both the temperature of the stretching force generation unit 40 and the temperature of the damping force generation unit 102 exceed the threshold temperature, the rotating electrical While giving priority to protecting the machine 60, the unsprung gain can be reduced and the damping force of the damping force generator 102 can be increased.

In the present embodiment, the “attenuation load changing unit 262” is configured by a portion of the ECU 200 that executes the attenuation load changing program. In addition, a portion of the ECU 200 that executes the processes of S12 to S15 of the attenuation load changing program constitutes an “electric power corresponding load changing unit”. In addition, a “temperature-related load changing unit” is configured by the part that executes the processing of S16 to S22 of the attenuation load changing program. Further, in the processing of S14, S15, and S19 to S22 of the attenuation load changing program in the ECU 200, the “attenuation coefficient changing unit” is configured by the part that changes the unsprung gain. In addition, in the processing of S14, S15, and S19 to S22 of the damping load changing program in the ECU 200, a “pass resistance control unit” is configured by a part that commands the drive circuit 240 to change the damping force.
Further, in the present embodiment, the passage resistance changing device 170 and the rotational position changing device 180 constitute a “passing resistance changing portion”.

In this embodiment, the unsprung damping force component generated by the expansion / contraction force generator 40 is set to a value proportional to the unsprung displacement speed Xvb as shown by the broken line in FIG. Can do. For example, as shown by the solid line in the figure, the inclination can be increased when the absolute value of the unsprung displacement speed Xvb is less than the set speed α, and the inclination can be decreased when the absolute value is greater than or equal to the set speed α. In this case, the damping force component Fg is determined by the following equation.
Fg = Ch · Xvb (| Xvb | <α) (3-1)
Fg = Cl · Xvb + β (| Xvb | ≧ α) (3-2)
β = α · (Ch-Cl), Ch> Cl
Ch and Cl are unsprung gains, and Ch is made larger than Cl.
The shock absorber 114 of the present embodiment has a damping characteristic similar to the solid line graph due to the characteristics of the leaf valve 134 and the like. Then, by adjusting Ch, Cl, and α, the change in the unsprung damping force component with respect to the displacement speed Xvb can show the same tendency as the change in the damping force with respect to the expansion / contraction speed of the shock absorber 114.

Furthermore, as shown in FIG. 12, the magnitude of the unsprung damping force component is determined depending on the direction of displacement of the unsprung portion, that is, when the approaching / separating force generator 20 is extended (extended) and contracted (contracted). It can also be changed. For example, as shown by a broken line, the unsprung gain can be set to Cb during expansion, and the unsprung gain can be set to Cb ′ smaller than Cb during contraction. Further, for example, as shown by a solid line, the unsprung gain can be set to a smaller value during contraction than during expansion (Ch ′ <Ch, Cl ′ <Cl).
The shock absorber 114 of the present embodiment has a damping characteristic in which the magnitude of the damping force differs between when extended and when contracted. Then, by adjusting Ch ′, Cl ′, α ′, the change in the unsprung damping force component with respect to the displacement speed Xvb during contraction shows the same tendency as the change in the damping force with respect to the contraction speed of the shock absorber 114. It can also be.

An embodiment different from the above will be described.
The shock absorber 114 of the above embodiment includes the leaf valve 134 and the like, and the damping force characteristic is nonlinear. However, the shock absorber 114 may have a substantially linear characteristic.
FIG. 13 shows a front sectional view of a part of a shock absorber 300 in which the damping force is changed by a flow path resistance changing device 170 that functions as a variable throttle without using a leaf valve. Since the shock absorber 300 has many parts in common with the shock absorber 114, the same components are denoted by the same reference numerals, description thereof is omitted, and different parts are mainly described.
The piston 310 of the shock absorber 300 has a first liquid passage 320 that connects the upper portion of the piston 310 and the axial hole 160, and a second liquid passage 322 that connects the first liquid passage 320 and the lower chamber 140. Is provided. A flow path resistance changing device 170 is provided at a portion where the first liquid passage 320 and the second liquid passage 322 are connected, and the flow passage area can be changed as described above. In this figure, the rotational position of the control rod 150 is the rotational position shown in FIG. When the damping force is changed, the rotational position of the control rod 150 is changed, and the flow path area is increased or decreased. In principle, the flow path area is not reduced to zero.
Further, the damping force of the shock absorber 300 is approximately equal on the expansion side and the contraction side.
Even when the shock absorber 300 is used, when one of the expansion force generation unit 40 and the damping force generation unit 102 generates heat or when power is insufficient, the above one is suppressed while suppressing a decrease in the degree of vibration suppression of the unsprung portion. Can be reduced.

Another embodiment different from the above will be described.
In the above embodiment, the damping force generation unit 102 changes the oil flow passage area by the flow passage resistance changing unit 170. However, the MR damper changes the damping force by changing the viscosity of the MR fluid by the magnetic field. Can be included.
FIG. 14 shows a front cross-section of the approaching / separating force generator 400 in which the damping force generator is an MR damper that is a magnetically responsive damper. In addition, since the approach / separation force generator 400 has many parts in common with the approach / separation force generator 20, the same components are denoted by the same reference numerals and description thereof is omitted.
In the unsprung vibration suppression unit 402, the damping force generation unit 410 is disposed on the inner peripheral side of the spring 106, passes through the center of the lower support member 52, and is connected to the lower support 24. As shown in the front cross-sectional view of FIG. 15, the damping force generation unit 410 includes a shock absorber 414 that is a hydraulic damper, and a magnetic field generator 416 provided on the outer peripheral side of the shock absorber 414.
The shock absorber 414 has a single cylinder type, a cylinder 420 filled with a working fluid, a piston 422 disposed in the cylinder 420, a piston 422 attached to one end, and the other end screwed. It has a piston rod 424 connected to the end of the rod 84 and a free piston 426 movably fitted to the lower part of the cylinder 420. When the piston 422 is moved in the cylinder 420, a damping force is generated by the passage resistance of the hydraulic fluid that passes through the gap between the cylinder 420 and the piston 422. The free piston 426 is filled with high-pressure gas under the free piston 426, and the change in volume on the upper side of the cylinder 420 is allowed by the movement of the free piston 426.
In this embodiment, the working fluid in the cylinder 420 is an MR fluid 428 which is a magnetorheological fluid. The MR fluid 428 is obtained by dispersing fine particles in oil using a surfactant as a dispersoid with fine particles having ferromagnetism such as iron powder as a dispersion medium. The MR fluid 428 flows almost in the same manner as normal oil in the absence of a magnetic field, and the viscosity increases when the magnetic field acts.

The magnetic field generation device 416 includes a housing 430 that has a generally cylindrical shape, and a solenoid coil 432 provided on the inner peripheral side of the housing 430. The housing 430 is formed of, for example, a ferromagnetic material such as steel, and generates a magnetic field in the gap between the piston 422 and the cylinder 420 by guiding the magnetism generated by the solenoid coil 432 to the piston rod 424. The piston rod 424 and the piston 422 are also made of a ferromagnetic material. In the cylinder 420, the main body 434 is formed of a ferromagnetic material, and the seal 436 and the guide body 438 at the upper end are formed of a paramagnetic material (which may be a diamagnetic material) such as synthetic rubber or resin. Further, a disc-shaped member 439 formed of a paramagnetic material such as aluminum or stainless steel is inserted between the upper end surface of the cylinder 420 and the upper end portion of the housing 430 in the axial direction. Since the disk-shaped member 439 increases the magnetic resistance between the upper end of the housing 430 and the upper end of the cylinder body 434, the center of the upper end of the housing 430 moves to the piston rod 424 (or vice versa). ) Magnetism will flow.
The solenoid coil 432 is obtained by winding a conductive wire around a cylindrical member formed of a paramagnetic material such as aluminum or stainless steel. A power receiving terminal 440 electrically connected to the solenoid coil 432 is provided on a side surface of the housing 430, and a conductive cord 442 is electrically connected to the power receiving terminal 440. The conductive cord 442 is disposed along the lower arm 28 via the cushion material 444. And it penetrates the vehicle body wall and is drawn into the vehicle body such as the engine room, and is connected to a drive circuit described later. That is, when power is supplied through the conductive cord 442, the solenoid coil 432 generates magnetism.
The magnetism generated by the solenoid coil 432 generally passes through a magnetic circuit formed by the housing 430, the piston rod 424, the piston 422, and the cylinder body 434, as indicated by arrows in the figure, and the piston 422 and the cylinder body 434 are connected to each other. A magnetic field is generated between them. Due to this magnetic field, fine particles of iron as a dispersoid form a cross-linked structure to increase the viscosity of the MR fluid 428 and increase the damping force generated by the shock absorber 414. That is, the damping force can be changed by adjusting the intensity of the magnetic field generated by the magnetic field generator 416. In the state where the magnetic field is not acting, the damping force with respect to the expansion and contraction of the shock absorber 414 is the smallest.

Since the configuration of this suspension system is substantially the same as that of the above embodiment, the drawing corresponding to FIG. 1 is omitted. In the present embodiment, the drive circuit 240 is connected to the magnetic field generation device 416 and supplies electric power according to a command from the ECU 200 to the magnetic field generation device 416.
Also in the present embodiment, the damping load reduction program is executed, and in the processing of S14, S15, and S20 to S22, when the damping force is set to medium, power set for normal running is supplied. In addition, when the damping force is increased or decreased, the supplied power is increased or decreased. As a result, when one of the expansion force generation unit 40 and the damping force generation unit 402 generates heat, the one load is reduced while suppressing a decrease in the degree of vibration suppression of the unsprung portion.

In the present embodiment, a “magnetic reactive damper” is constituted by the shock absorber 414 filled with the MR fluid 428. The magnetic field generator 416 and the drive circuit 240 constitute a “magnetic field generator”. Further, in the processing of S14, S15, and S20 to S22 in the ECU 200, a “magnetic field strength control unit” is configured by a part that performs a control to change the supplied power by giving a command to change the damping force.

It is a figure showing typically an electric suspension system which is an example of a claimable invention. It is front sectional drawing which shows the approach / separation direction force generator of the said suspension system. It is front sectional drawing which shows the shock absorber of the said approach / separation direction force generator. It is a figure which shows the plane cross section of the front-end | tip part of the control rod of the said flow-path resistance change apparatus. It is front sectional drawing which shows the hollow rotating shaft which rotates the said control rod. It is a figure which shows the single-wheel model of the suspension apparatus of the said Example. It is a figure which shows the equation of motion of the said model. It is a figure which shows the ground-contact load fluctuation | variation at the time of changing damping force in the said model. It is a figure which shows the ground-contact load fluctuation | variation at the time of changing the unsprung gain in the said model. It is a figure which shows the flowchart of an attenuation burden change program. It is a figure which shows the change of the unsprung damping force component which the expansion / contraction direction force generation part of the said approach / separation direction force generator generates. It is a figure which shows another change of the said unsprung damping force component. It is front sectional drawing which shows another shock absorber different from the above. It is front sectional drawing which shows the approach / separation direction force generator different from the above. It is front sectional drawing which shows the shock absorber of the said approach / separation direction force generator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10: Suspension apparatus 12: Wheel 14: Vehicle body 20: Approaching / separating direction force generator 22: Upper support 24: Lower support 26: Wheel holding part 28: Lower arm 40: Control expansion / contraction direction force generation part (expansion / contraction force direction generation part) 42 : Unsprung vibration suppressing part (passive expansion / contraction part) 44: Main spring 60: Rotating electric machine (electrically operated machine) 62: Ball screw device (motion converting device) 72: Rotating shaft 74: Rotor (rotor) 76: Stator 84: Screw rod (relative moving body) 94: Screw nut 96: Spline nut 100: Elastic force generator 102: Damping force generator 104, 106: Compression coil spring 108: Transmission member 114: Shock absorber 130: Hard valve 132: Soft valve 13 136: Leaf valve 144: Liquid passage 150: Control rod 154: Tip portion 164: Bypass passage 170: Flow path resistance changing device 180: Rotation position changing device 184: Hollow rotating shaft 194: Connection portion 196: First temperature sensor 198 : Second temperature sensor 200: electronic control unit [ECU] 210: sprung acceleration sensor (acceleration detector) 212: unsprung acceleration sensor 226: voltmeter 230: electronic drive unit [EDU] 232: storage battery 240: drive circuit 260 : Output control unit 262: damping load changing unit <second embodiment> 300: shock absorber 320: first liquid passage 322: second liquid passage <third embodiment> 400: approaching / separating direction force generator 410: damping force Generator 414: Shock Ab Over bar 416: magnetic field generator 428: MR fluid

Claims (5)

A suspension system including an approaching / separating direction force generator that generates an approaching / separating direction force that is a force in a direction in which an unsprung part and an unsprung part of a vehicle approach / separate, and a control device that controls the approaching / separating direction force generator. There,
The approaching / separating direction force generator is
An expansion / contraction direction force generation unit that generates an expansion / contraction direction force that is a force in an expansion / contraction direction including an unsprung damping force component that attenuates vibration of the unsprung portion according to an output of an electric operation machine that the device has.
A damping force generator that is connected in series with the expansion / contraction direction force generation unit, generates a damping force when passively expanded and contracted, and can change the magnitude of the damping force; and
In order for the control device to reduce a burden on one of the expansion / contraction direction force generation unit and the damping force generation unit, an unsprung damping force component of the expansion / contraction direction force generation unit and a damping force of the damping force generation unit An electric suspension system for a vehicle, comprising: a damping load changing unit that increases the other of the unsprung damping force component and damping force when one of the two is reduced.   Unsprung damping of the expansion / contraction direction force generation unit when the attenuation load change unit is in a state where it is necessary to reduce the load, which is highly necessary to reduce one load of the expansion / contraction direction force generation unit and the damping force generation unit. The electric suspension system for a vehicle according to claim 1, wherein one of a force component and a damping force of the damping force generator is reduced. The attenuation burden changing unit is
When one of the temperature of the stretching direction force generation unit and the temperature of the damping force generation unit exceeds the set temperature, the unsprung damping force component and damping force of the stretching direction force generation unit exceed the set temperature. While reducing one of the damping force of the generating unit and increasing the other of them, a temperature corresponding load changing unit,
A power corresponding load changing unit that decreases an unsprung damping force component of the expansion / contraction direction force generation unit and increases a damping force of the damping force generation unit when power to be supplied to the electric machine is insufficient. The electric suspension system for vehicles according to claim 1 or 2 containing at least one. Stretching direction force including the unsprung damping force component including the product of the unsprung displacement speed and the set damping coefficient in the approaching / separating direction, in which the control device approaches and separates the sprung portion and the unsprung portion. Including an expansion / contraction direction force determination unit for determining
The electric suspension system for a vehicle according to any one of claims 1 to 3, wherein the damping load changing unit includes a damping coefficient changing unit that changes the unsprung damping force component by changing the damping coefficient. The expansion / contraction direction force determination unit determines an expansion / contraction direction force including the unsprung damping force component and a sprung damping force component that attenuates vibration of the sprung portion,
The electric suspension system for a vehicle according to claim 4, wherein the damping load changing unit reduces the load of the expansion / contraction direction force generation unit without reducing the sprung damping force component.

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