JP5387857B2 - Vehicle suspension system - Google Patents

Description

  The present invention relates to a vehicle suspension apparatus, and more particularly to a suspension apparatus including an electromagnetic actuator that generates a propulsive force and a damping force by an electric motor.

  A suspension device for a vehicle is provided with a suspension spring that elastically connects a sprung portion and a unsprung portion of a vehicle, and a shock that is disposed in parallel with the suspension spring and generates a damping force for relative movement between the sprung portion and the unsprung portion. Equipped with an absorber. An electric motor may be used as a source of damping force. When an electric motor is used as a force generation source, the shock absorber generates not only a damping force but also a propulsive force for positively changing the suspension stroke by the energization control of the electric motor. Such a shock absorber is called an electromagnetic shock absorber or an electromagnetic actuator.

  Patent Document 1 proposes an electromagnetic actuator including a ball screw mechanism in which a ball screw and a ball screw nut are engaged, and an electric motor coupled to the ball screw mechanism. In this electromagnetic actuator, an electric motor is caused to generate power by a vertical expansion / contraction operation of a ball screw mechanism that accompanies or moves away from an upper spring portion and a lower spring portion of a vehicle, and a damping force is generated by a resistance force generated by the power generation. Further, the ball screw mechanism is expanded and contracted by energizing the electric motor from the power source to generate a propulsive force.

JP 2007-203933 A

  However, in such an electromagnetic actuator, the frictional resistance of the internal mechanism changes. For example, when the vehicle starts in a low temperature environment, the frictional resistance is high because the grease of the internal mechanism of the electromagnetic actuator has a high viscosity. Therefore, an appropriate actuator force cannot be transmitted to the sprung part and the unsprung part, and the ride comfort and the handling stability may be reduced.

  The present invention is made to solve the above-described problems, and is capable of generating an appropriate actuator force even when a frictional change occurs in an electromagnetic actuator, thereby suppressing a decrease in ride comfort and steering stability. Objective.

A feature of the present invention is that a suspension spring (52) that elastically connects an unsprung part (SU) and an unsprung part (SD) of a vehicle, and the suspension spring is disposed in parallel between the unsprung part and the unsprung part. And an electromagnetic actuator (20) having an electric motor 30 that generates an actuator force that is a propulsion force and a damping force with respect to relative movement between the sprung portion and the unsprung portion, and a target that is a target value of the actuator force actuator force and (f _act ^*) target actuator force calculating means for calculating a (100, S53), on the basis of the target actuator force calculated by the target actuator force calculating means, drive control means for driving and controlling the electric motor ( 100, 73, S66) at the start of the vehicle Friction force calculating means (100, S11 to S22) for driving the electric motor with a preset driving force for friction measurement and calculating the friction force (F) of the electromagnetic actuator from the rotation angle of the electric motor at that time And target actuator force correcting means (100, S55 to S66) for correcting the target actuator force based on the friction force calculated by the friction force calculating means.

  In the present invention, the suspension spring and the electromagnetic actuator are arranged in parallel between the spring top and the spring bottom. The electromagnetic actuator generates an actuator force that is a propulsion force and a damping force for relative movement between the sprung portion and the unsprung portion, and suppresses vibration of the sprung portion. For example, the electromagnetic actuator includes an electric motor that rotates the motor shaft by a magnetic force, and an operation conversion mechanism that mutually converts the rotational motion of the motor shaft and the approach / separation motion between the sprung portion and the unsprung portion. Can do. The target actuator force calculation means calculates a target actuator force. For example, vehicle vibration state quantities such as sprung speed and unsprung speed are acquired, and a target actuator force for suppressing vertical vibration of the vehicle is calculated from the vehicle vibration state quantities. Then, the drive control means drives and controls the electric motor so that the calculated target actuator force is generated from the electromagnetic actuator.

  When the electromagnetic actuator operates, a frictional force is generated in its internal mechanism. This frictional force changes according to the vehicle environment temperature, and this change in frictional force causes a change in the load transmitted to the sprung portion and the unsprung portion. Therefore, in the present invention, the frictional force calculating means drives the electric motor with a preset frictional measurement driving force when starting the vehicle, and calculates the frictional force of the electromagnetic actuator from the rotation angle of the electric motor at that time. In this case, the frictional force calculating means may drive the electric motor with a constant frictional measurement driving force so that the electromagnetic actuator is step-driven. The rotational position of the electric motor changes when a friction measurement driving force is generated from the electric motor, and is stabilized at a position where loads acting on the suspension device (vehicle load, spring load, actuator force, friction force, etc.) are balanced. Therefore, the frictional force of the electromagnetic actuator can be calculated by detecting the angle of rotation of the electric motor (the amount of change in the rotational position). In this case, the rotation angle of the electric motor decreases as the frictional force increases.

  Then, the target actuator force correcting means corrects the target actuator force based on the friction force calculated by the friction force calculating means. Therefore, the target actuator force is corrected to an appropriate value corresponding to the friction force of the electromagnetic actuator. As a result, according to the present invention, it is possible to suppress a decrease in riding comfort and steering stability due to frictional forces.

  Another feature of the present invention includes temperature determination means (100, S11 to S12) for determining whether or not the vehicle is started in a low temperature environment, and the frictional force calculation means and the target actuator force correction. The means is to operate when it is determined by the temperature determination means that the vehicle has been started in a low temperature environment (100, S13 to S14, S54).

  When the vehicle starts in a low temperature environment, the frictional force is large because the grease of the internal mechanism of the electromagnetic actuator has a high viscosity. Therefore, in the present invention, the temperature determination means determines whether or not the vehicle is started in a low temperature environment, and when it is determined that the vehicle is started in a low temperature environment, the friction of the electromagnetic actuator is determined. Force calculation and target actuator force correction are performed. As a result, the processing of the frictional force calculating means and the target actuator force correcting means can be minimized to reduce the calculation burden.

  Note that the temperature determination means acquires information representing the environmental temperature of the vehicle at the start of the vehicle, for example, and when the environmental temperature is less than a preset low temperature determination threshold, the vehicle is started in a low temperature environment. What is necessary is just to determine. The environmental temperature of the vehicle may be any temperature at which the temperature of the electromagnetic actuator can be estimated. For example, the outside air temperature can be employed.

  Another feature of the present invention resides in that the target actuator force correcting means corrects the target actuator force only during a predetermined period from the start of the vehicle (S55 to S57).

  In the electromagnetic actuator, the viscosity of the grease of the internal mechanism decreases after a certain amount of time has elapsed since the start of the vehicle. Therefore, the change in the frictional force of the electromagnetic actuator may be considered only during a predetermined period from the start of the vehicle. Therefore, in the present invention, the target actuator force is corrected only for a predetermined period from the start of the vehicle. Therefore, the target actuator force becomes more appropriate. The “predetermined period” is not limited to measuring the passage of a fixed time. For example, when the number of strokes from the start of the electromagnetic actuator is counted and the count value reaches a set value, It can also be determined that a predetermined period has elapsed since the start.

  Another feature of the present invention is that the target actuator force correction means has a small correction amount for correcting the target actuator force in a range where the rotation speed of the electric motor is smaller than a preset threshold value. It is set to become smaller (S58 to S61).

  The frictional force generated by the electromagnetic actuator acts in the direction opposite to the direction of movement of the electromagnetic actuator. Therefore, the correction value of the target actuator force is calculated to a value that applies a force in the same direction as the moving direction of the electromagnetic actuator. For example, a correction value that works in the extending motion direction is calculated during the stretching operation in which the sprung portion and the unsprung portion are separated, and a correction value that works in the contracting motion direction is calculated during the contracting operation in which the sprung portion and the unsprung portion approach. For this reason, when the moving direction of the electromagnetic actuator is switched, the direction of the correction value of the target actuator force also changes, and the change of the correction value of the target actuator force becomes large.

  Therefore, in the present invention, in a range where the rotational speed of the electric motor is smaller than a preset threshold value, the correction amount for correcting the target actuator force is set to be smaller as the rotational speed is smaller. That is, when the moving direction of the electromagnetic actuator is switched, in the process, the rotating speed of the electric motor increases in the opposite direction after the rotating speed decreases to zero. Therefore, according to the present invention, the correction amount of the target actuator force decreases when the rotation speed of the electric motor passes through zero, and increases with the increase in rotation speed after the rotation direction is reversed. As a result, sudden fluctuations in the actuator force when the moving direction of the electromagnetic actuator is reversed are suppressed, and the ride comfort can be further improved. The “rotational speed of the electric motor” means a magnitude regardless of the rotational direction, that is, an absolute value of the rotational speed.

  In the above description, the reference numerals shown in parentheses assist the understanding of the invention, and do not limit each constituent element of the invention to the embodiment defined by the reference numerals.

1 is a schematic system configuration diagram of a suspension device according to an embodiment. It is a partial section schematic diagram of a suspension body concerning an embodiment. It is a suspension single-wheel model figure concerning an embodiment. It is a flowchart showing the frictional force calculation routine which concerns on embodiment. It is a flowchart showing the actuator force control routine which concerns on embodiment. It is a graph showing the frictional force correction coefficient map which concerns on embodiment. It is a graph showing the correction | amendment load characteristic which concerns on embodiment. It is a graph showing the corrected load characteristic when not correcting a frictional force.

  Hereinafter, a suspension device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a system configuration of an electric active suspension device according to the present embodiment.

  As shown in FIG. 1, the electric active suspension apparatus includes four suspension bodies 10FL, 10FR, 10RL, 10RR provided between the wheels WFL, WFR, WRL, WRR and the vehicle body B, and the suspension bodies. The suspension control device 100 controls the operation of 10FL, 10FR, 10RL, and 10RR. Note that the suspension bodies 10FL, 10FR, 10RL, and 10RR and the wheels WFL, WFR, WRL, and WRR have the same configuration, and hence are simply referred to as the suspension body 10 and the wheels W in the following description. The suspension control device 100 is called a suspension ECU 100, and the electric active suspension device is called a suspension device.

  As shown in FIG. 2, the suspension body 10 is provided between a lower arm LA that supports the wheel W and a mount member HA that is a part of the vehicle body B. The suspension body 10 includes an electromagnetic actuator 20 that functions as a shock absorber, a spring device 50 that absorbs an impact received from a road surface to enhance riding comfort and elastically supports the weight of the vehicle, and a hydraulic damper device 60. The side supported by the spring device 50, that is, the member on the vehicle body B side is the spring top SU. The member that supports the spring device 50, that is, the member on the wheel W side is the unsprung portion SD.

  The electromagnetic actuator 20 includes an electric motor 30 and a ball screw mechanism 40. The electric motor 30 is fixed to the upper surface of the mounting member 11. The attachment member 11 is assembled to the mount member HA on the vehicle body B side via an upper support member 12 made of an elastic member. In this embodiment, the electric motor 30 is a three-phase brushless DC motor that is driven and controlled by a three-phase inverter. The ball screw mechanism 40 is connected to an output shaft (not shown) of the electric motor 30 and has a function as an operation conversion mechanism that converts the rotational motion of the electric motor 30 into linear motion.

  The ball screw mechanism 40 includes a ball screw shaft 41 in which a screw groove 41 a is formed, and a ball screw nut 42 that is screwed into the screw groove 41 a of the ball screw shaft 41. The ball screw shaft 41 is connected to an output shaft (not shown) of the electric motor 30 so as not to rotate relative thereto, and is rotatably supported by the outer tube 21 via a bearing Br. The outer tube 21 is fixed to the lower surface of the mounting member 11, extends downward from the mounting member 11, and covers the periphery of the ball screw shaft 41 with a predetermined interval.

  The ball screw nut 42 is assembled so as not to rotate with respect to the outer tube 21 and to move in the axial direction (vertical direction) by a non-rotating stop mechanism (for example, spline fitting). Thereby, in this ball screw mechanism 40, the rotational motion of the ball screw shaft 41 is converted into the linear motion in the axial direction of the ball screw nut 42, and conversely, the linear motion in the axial direction of the ball screw nut 42 is converted into the ball screw shaft. It is converted into 41 rotational motions.

  The inner tube 22 is integrally connected to the ball screw nut 42. The inner tube 22 is coaxially arranged in the outer tube 21 and can move up and down integrally with the ball screw nut 42, that is, can move relative to the outer tube 21 in the up and down direction. The inner tube 22 is provided such that its lower end is exposed to the outside of the outer tube 21. An operation plate 23 that applies force to the hydraulic damper device 60 is fixed to the lower end of the inner tube 22.

  As shown in FIG. 2, the spring device 50 includes a cover tube 51 in which a hydraulic damper device 60 is assembled at a lower end portion, and a coil spring 52. The coil spring 52 corresponds to the suspension sprue of the present invention, and is interposed between the spring receiver 51 a provided on the outer peripheral surface of the cover tube 51 and the attachment member 11 in a compressed state. The cover tube 51 is fixed to a cylinder 63 of a hydraulic damper device 60 described later, and is provided so as to be movable relative to the outer tube 21 in the axial direction.

  The hydraulic damper device 60 is disposed between the electromagnetic actuator 20 and the unsprung portion SD so as to be connected in series to the electromagnetic actuator 20. As shown in FIG. 2, the hydraulic damper device 60 includes a support spring 61 interposed between the lower surface of the operation plate 23 and the lower wall of the cover tube 51, and a damping force against the axial movement of the operation plate 23. And a damper main body 62 for imparting. The support spring 61 is provided to absorb high-frequency vibration (for example, high-frequency vibration exceeding 10 Hz) generated when the vehicle travels on a rough road surface, etc., and includes a lower arm LA (unsprung SD) and The electromagnetic actuator 20 is elastically connected. The damper main body 62 is a liquid-tight damper, and includes a cylindrical cylinder 63 fixed to the lower arm LA, a piston 64 that is slidably mounted in the cylinder 63 in the axial direction (vertical direction), And a piston rod 65 assembled to the piston 64.

  The cylinder 63 is partitioned into an upper chamber 63a and a lower chamber 63b by a piston 64, and fluid (for example, oil) is sealed in the upper chamber 63a and the lower chamber 63b. The piston 64 has a piston valve 64a. A fluid moves between the upper chamber 63a and the lower chamber 63b through the piston valve 64a, whereby a predetermined resistance force is applied to the piston 64. The piston rod 65 extends upward from the upper wall of the cylinder 63 and is connected to the operation plate 23 at the upper end.

  In the suspension body 10 configured as described above, when the electric motor 30 of the electromagnetic actuator 20 is rotated by power supply from a battery power source or the like, the ball screw shaft 41 connected to the output shaft of the electric motor 30 is rotated. As the ball screw shaft 41 rotates, the ball screw nut 42 moves in the axial direction. As the ball screw nut 42 moves in the axial direction, the inner tube 22, the operation plate 23, the piston rod 65 and the piston 64 connected to the ball screw nut 42 also move in the axial direction. At this time, the cylinder 63 also moves in the axial direction with little relative movement between the cylinder 63 and the piston 64. Thereby, the relative distance between the sprung portion SU and the unsprung portion SD changes. In this way, the electric motor 30 generates a driving force for the relative movement between the sprung portion SU and the unsprung portion SD. This propulsive force is controlled, for example, so as to improve riding comfort.

  For example, when a relatively low frequency external force (such as road surface input) is applied to the suspension body 10, the ball screw nut 42 of the electromagnetic actuator 20 moves in the axial direction due to the external force. As the ball screw nut 42 moves in the axial direction, the sprung portion SU and the unsprung portion SD move relative to each other and the ball screw shaft 41 rotates. The electric motor 30 is rotated by the rotation of the ball screw shaft 41. At this time, since the electric motor 30 acts as a generator, the electric motor 30 generates a resistance force (damping force) against relative movement between the spring upper portion SU and the spring lower portion SD. Thereby, the relative vibration between the sprung portion SU and the unsprung portion SD is suppressed. The piston 64 and the cylinder 63 of the hydraulic damper device 60 do not move relative to each other due to low-frequency external force.

  When a high-frequency road surface input of about 20 Hz is applied to the suspension body 10, the cylinder 63 moves relative to the piston 64 in the hydraulic damper device 60. Thereby, a damping force is generated in the hydraulic damper device 60, and the high frequency vibration is not transmitted to the ball screw mechanism 40 side but is suppressed by the hydraulic damper device 60. That is, the hydraulic damper device 60 functions as a high frequency vibration filter.

  Next, the electronic control system of the suspension device of this embodiment will be described. The suspension device includes a suspension ECU 100. As shown in FIG. 1, an unsprung acceleration sensor 71 and a sprung acceleration sensor 72 are connected to the suspension ECU 100. The unsprung acceleration sensor 71 is provided in an unsprung portion SD such as a lower arm LA to which each suspension body 10 is attached, and detects an acceleration (unsprung acceleration) G1 along the vertical direction of the unsprung portion SD. The sprung acceleration sensor 72 is provided at a position (each wheel position) where each suspension body 10 of the sprung upper SU is attached, and an acceleration along the vertical direction at each wheel position of the sprung SU (sprung acceleration). ) G2 is detected.

  The suspension ECU 100 is connected to a motor drive circuit 73 that drives the electric motor 30 of each electromagnetic actuator 20. The motor drive circuit 73 is composed of a three-phase inverter circuit. The motor drive circuit 73 is supplied with a drive power supply (power supply voltage Vbat) from a battery (not shown), and controls the duty ratio of an internal switching element (not shown), whereby the U phase and V phase of the electric motor 30 are controlled. The amount of current flowing in the W phase is adjusted. The suspension ECU 100 is connected to the gate signal input unit of the motor drive circuit 73 and outputs a PWM control signal for controlling the duty ratio to each switching element to control the energization amount of the electric motor 30.

  In addition, a rotation angle sensor 74 that detects the rotation angle of the electric motor 30 is connected to the suspension ECU 100. The rotation angle sensor 74 is provided in each electric motor 30 and detects a rotation angle θm of a rotor (not shown). The rotation angle θm is used to detect an electrical angle because the suspension ECU 100 needs to control the voltage phase of the motor drive circuit 73. In the present embodiment, the rotation angle θm is also used when measuring a frictional force, which will be described later.

  A temperature sensor 75 is connected to the suspension ECU. The temperature sensor 75 only needs to detect a temperature (for example, the environmental temperature of the vehicle) at which the ambient temperature of the electromagnetic actuator 20 can be estimated. In this embodiment, the existing intake air temperature for detecting the engine supply air temperature is used. Use sensors. The temperature sensor 75 may detect the ambient temperature of each electromagnetic actuator 20. Hereinafter, the temperature detected by the temperature sensor 75 is referred to as a detected temperature Tx.

  The suspension ECU 100 mainly includes a microcomputer having a CPU, a ROM, a RAM, and the like. The suspension ECU 100 calculates target values of the propulsive force and the damping force for the relative movement between the unsprung portion SU and the unsprung portion SD in order to obtain a good ride comfort of the vehicle. In the present embodiment, these propulsive force and damping force are generated by the electric motor 30 of the electromagnetic actuator 20. The propulsive force and damping force generated by the electric motor 30 are referred to as actuator force in this specification. In addition, the target values of the propulsive force and the damping force are referred to as a target actuator force in this specification. The suspension ECU 100 outputs a PWM control signal corresponding to the calculated target actuator force to the motor drive circuit 73 to drive and control the electric motor 30.

  The suspension ECU 100 independently controls the electric motor 30 of the electromagnetic actuator 20 provided on the four wheels. Therefore, in each electromagnetic actuator 20, the actuator force output from the electric motor 30 is independently controlled to attenuate the vibrations of the vehicle body B and the wheels W, that is, the vibrations of the spring upper part SU and the spring lower part SD. Control (vibration suppression control) is executed. The control performed by the suspension ECU 100 described below relates to the control of the electric motor 30 of the electromagnetic actuator 20 for one wheel, but the suspension ECU 100 performs the control of the four electric motors 30 independently in parallel. And execute.

  The suspension ECU 100 calculates the target actuator force based on the sprung speed and the unsprung speed. However, at low temperatures, the friction force of the electromagnetic actuator 20 is large, so that the target actuator force does not become an optimum value. This frictional force is mainly due to the viscosity of the grease of the ball screw mechanism 40. At low temperatures, the viscosity of the grease increases and the frictional force of the electromagnetic actuator 20 increases. Accordingly, the target actuator force is insufficient and a desired load cannot be transmitted to the sprung SU and the unsprung SD. Therefore, in the present embodiment, when the vehicle is started in a low temperature environment, the frictional force is measured, and the target actuator force is corrected by the measured frictional force, so that an appropriate load is applied to the unsprung SU and unsprung SD. Be able to communicate.

  FIG. 4 is a flowchart showing a frictional force calculation routine executed by suspension ECU 100. This frictional force calculation routine is stored as a control program in the ROM of the suspension ECU 100, and is started when the vehicle is started, that is, when an ignition switch (not shown) is turned on.

  When this routine is started, the suspension ECU 100 reads the detected temperature Tx detected by the temperature sensor 75 in step S11. Subsequently, in step S12, it is determined whether or not the detected temperature Tx is lower than a preset low temperature determination threshold value Tref.

  If the detected temperature Tx is equal to or higher than the threshold value Tref, the viscosity of the grease is low and the influence of the frictional force of the electromagnetic actuator 20 is small. In such a starting situation, the suspension ECU 100 sets the flag FL to “0” in step S13 and ends the frictional force calculation routine. This flag FL indicates whether or not the vehicle has been started in a low temperature environment. “1” represents a low temperature start, and “0” represents a normal temperature start.

  On the other hand, if the detected temperature Tx is lower than the threshold value Tref, the flag FL is set to “1” in step S14. Subsequently, in step S15, the suspension ECU 100 reads the rotation angle θm of the electric motor 30 detected by the rotation angle sensor 74, and stores the rotation angle θm as the first rotation angle θm1. The first rotation angle θm1 represents the rotation angle of the electric motor 30 at the time of starting the vehicle (the rotation position of the stationary rotor). Subsequently, in step S <b> 16, the suspension ECU 100 outputs a drive command for causing the electric motor 30 to generate a preset friction measurement drive force to the motor drive circuit 73. The friction measurement driving force is a constant driving force so that the electromagnetic actuator 20 is step-driven in the extending direction. Therefore, the suspension ECU 100 outputs to the motor drive circuit 73 a PWM control signal that provides a constant motor output. In the present embodiment, the friction measurement driving force is set in a direction in which the electromagnetic actuator 20 is extended, but may be set in a direction in which the electromagnetic actuator 20 is contracted. Thus, the electromagnetic actuator 20 extends by the rotation of the electric motor 30 and becomes stable when the load in the vertical direction is balanced.

  Subsequently, in step S17, the suspension ECU 100 reads the rotation angle θm detected by the rotation angle sensor 74, and calculates the rotation speed ω of the electric motor 30 by differentiating the rotation angle θm with time. Subsequently, in step S18, it is determined whether or not the magnitude | ω | of the rotational speed ω is equal to or less than the threshold value ωref. Steps S17 to S18 are for determining whether or not the operation of the electromagnetic actuator 20 (rotation of the electric motor 30) has converged and stopped. Therefore, the threshold value ωref is set to zero or a small value close to zero. Hereinafter, the magnitude | ω | of the rotational speed ω is represented as a rotational speed | ω |. While the rotation speed | ω | exceeds the threshold value ωref, the processes in steps S17 to S18 are repeated. When the rotation speed | ω | becomes equal to or less than the threshold value ωref, the suspension ECU 100 reads the rotation angle θm detected by the rotation angle sensor 74 and stores the rotation angle θm as the second rotation angle θm2 in step S19. The second rotation angle θm2 represents the rotation angle (rotational position of the stationary rotor) after the electric motor 30 is driven by the friction measurement driving force and the electromagnetic actuator 20 is stabilized.

  Subsequently, in step S20, the suspension ECU 100 cancels the drive command for causing the electric motor 30 to generate the friction measurement drive force. Thereby, energization to the electric motor 30 is stopped, and the electromagnetic actuator 20 is contracted to return to the initial state. Subsequently, in step S21, a rotation angle Δθ by which the rotor of the electric motor 30 is rotated by the friction measurement driving force is calculated. The rotation angle Δθ is calculated as an absolute value (Δθ = | θm2−θm1 |) obtained by subtracting the first rotation angle θm1 from the second rotation angle θm2.

  Subsequently, the suspension ECU 100 calculates the frictional force F of the electromagnetic actuator 20 in step S22. Here, calculation of the friction force F will be described with reference to the suspension model diagram of FIG.

In the drawing, the motor member represents the electric motor 30 and a member integrally connected to the electric motor 30, for example, a member such as the ball screw shaft 41, the attachment member 11, and the outer tube 21. Let the mass of this motor member be m ₃ . Further, the intermediate member represents a member interposed between the motor member and the hydraulic damper device 60, for example, a member such as the ball screw nut 42, the inner tube 22 and the operation plate 23. The mass of this intermediate member is m ₄ . The spring constant of the upper support member 12 interposed between the motor member and the sprung portion SU is K _b , and the damping coefficient is C _b . Further, the spring constant (spring constant of the support spring) of the hydraulic damper device 60 interposed between the intermediate member and the unsprung part SD is K _s , and the damping coefficient (damping coefficient of the damper body) is C _s . Further, the spring constant of the coil springs 52 provided between the spring lower SD and the motor member and K _c. The mass of the unsprung portion SD is m ₁ , and the mass of the unsprung portion SU is m ₂ . Further, the spring constant of the tire and K _t.

Further, the vertical displacement amount from a reference position of the unsprung portion SD time t as a parameter and x _1, the vertical displacement from the reference position of the sprung SU that the time t as a parameter and x _2, the parameters of time t the vertical displacement amount from a reference position of the motor member and a x _3, the vertical displacement amount from a reference position of the intermediate member in the time t as a parameter and x _4. Further, an actuator force generated by the electromagnetic actuator 20 when the electric motor 30 is step-driven with a friction measurement driving force is represented by f _test, and a frictional force (load of friction) of the electromagnetic actuator 20 is represented by F.

電磁アクチュエータ２０の伸長動作が停止すると、上記式（１）〜（４）における微分項がゼロになるため、運動方程式は式（５）〜式（８）にて表される。

Equations of motion in the spring upper SU, the motor member, the intermediate member, and the spring lower SD when the electromagnetic actuator 20 is step-driven in the extending direction are expressed by equations (1) to (4).

When the extension operation of the electromagnetic actuator 20 is stopped, the differential term in the above formulas (1) to (4) becomes zero, so the equation of motion is expressed by the formulas (5) to (8).

（ｘ_３−ｘ_４）の値は、電気モータ３０の回転角度Δθ（ｒａｄ）から次式（１０）にて計算することができる。

ここで、ｌは、ボールねじ機構４０のボールねじリード（ｍ）を表す。
従って、摩擦力Ｆは、次式（１１）により計算することができる。

When x ₁ and x ₂ are eliminated from the equations (5) to (7), the frictional force F is calculated by the following equation (9).

The value of (x ₃ −x ₄ ) can be calculated from the rotation angle Δθ (rad) of the electric motor 30 by the following equation (10).

Here, l represents a ball screw lead (m) of the ball screw mechanism 40.
Therefore, the friction force F can be calculated by the following equation (11).

  When the suspension ECU 100 calculates the frictional force F in step S22, the suspension ECU 100 ends the frictional force calculation routine. The frictional force F calculated by this frictional force calculation routine is then used to calculate the target actuator force for suppressing the vibration of the vehicle. In this frictional force calculation routine, the frictional force of the electromagnetic actuator 20 is calculated when the vehicle is started under a low temperature environment, and the frictional force is not calculated when the vehicle is not started under a low temperature environment. .

  Next, an actuator force control routine executed by the suspension ECU 100 will be described. FIG. 5 is a flowchart showing an actuator force control routine. The actuator force control routine is stored as a control program in the ROM of the suspension ECU 100. The actuator force control routine is started when the frictional force calculation routine ends, and is repeated at a predetermined short cycle until the ignition switch is turned off.

  When the actuator force control routine is activated, the suspension ECU 100 reads the unsprung acceleration G1 detected by the unsprung acceleration sensor 71 and the unsprung acceleration G2 detected by the unsprung acceleration sensor 72 in step S51. Subsequently, in step S52, the unsprung acceleration G1 and the unsprung acceleration G2 are respectively integrated with time to obtain the unsprung speed V1 that is the speed in the vertical direction of the unsprung part SD and the vertical speed of the unsprung part SU. The sprung speed V2 is calculated.

Subsequently, the suspension ECU 100 calculates a target actuator force f _act ^* for attenuating vibrations of the vehicle body B and the wheels W in step S53. In the present embodiment, the target actuator force f _act ^* is calculated by the following equation (12) so that the control based on the skyhook damper theory and the control based on the pseudo groundhook theory are simultaneously achieved.
f _act ^* = C 2 · V 2 −C 1 · V 1 (12)
Here, C2 is a gain related to the sprung speed V2, and C1 is a gain related to the unsprung speed V1.

Subsequently, the suspension ECU 100 determines whether or not the flag FL is “1” in step S54. If the flag FL is “0”, the suspension ECU 100 advances the process to step S66 to execute the target actuator force f. A control signal corresponding to _act ^* is output. That is, a control amount (target energization amount and rotation direction) of the electric motor 30 is determined based on the target actuator force f _act ^* , and a PWM control signal having a duty ratio corresponding to the determined control amount is switched by the motor drive circuit 73. Output to the element. Thereby, a damping force or a propulsive force for attenuating the vibrations of the vehicle body B and the wheels W is generated from the electromagnetic actuator 20. In this case, a drive current flows from the battery to the electric motor 30 or a regenerative current flows from the electric motor 30 to the battery according to the balance between the back electromotive voltage generated in the electric motor 30 and the power supply voltage of the battery.

  On the other hand, when it is determined in step S54 that the flag FL is “1”, the suspension ECU 100 advances the process to step S55. In step S55, the timer value Tim is incremented by "1". Subsequently, it is determined whether or not the timer value Tim has reached a preset timer value Tmax. The timer value Tim has an initial value set to “0”. Since the actuator force control routine is repeatedly executed at a predetermined short cycle, the processes in steps S55 and S56 have been performed for a set time corresponding to the set timer value Tmax since the start of the actuator force control routine. This is a process for determining whether or not. Since the timer value Tim has not reached the set timer value Tmax at the beginning of the actuator force control routine, the determination in step S56 is “No”, and the suspension ECU 100 advances the process to step S58.

In step S58, the suspension ECU 100 reads the rotation angle θm detected by the rotation angle sensor 74, and calculates the rotation speed ω of the electric motor 30 by differentiating the rotation angle θm with time. Subsequently, in step S59, it is determined whether or not the rotational speed | ω | is equal to or lower than a preset reference rotational speed ω0. If the rotational speed | ω | is equal to or lower than the reference rotational speed ω0, in step S60, as shown in FIG. 6, the correction coefficient A set so as to decrease as the rotational speed | ω | On the other hand, if the rotational speed | ω | exceeds the reference rotational speed ω0, the value of the correction coefficient A is set to “1” in step S61. If the correction coefficient set in steps S60 and S61 is expressed by a calculation formula, the following formulas (13) and (14) are obtained.
A = | ω | / ω0 (ω ≦ ω0) (13)
A = 1 (ω> ω0) (14)

  Subsequently, in step S62, the suspension ECU 100 calculates the correction load Δf by multiplying the frictional force F by the coefficient A (Δf = A · F). This friction force F is the friction force F calculated in the above-described friction force calculation routine. Therefore, when the rotational speed | ω | is equal to or lower than the reference rotational speed ω0, a correction load Δf that is smaller as the rotational speed | ω | is smaller is set.

  Subsequently, the suspension ECU 100 determines in step S63 whether or not the operating direction of the electromagnetic actuator 20 is the extending direction. The operation direction of the electromagnetic actuator 20 can be determined from the direction (sign) of the motor rotation speed ω calculated in step S58. When the operation direction of the electromagnetic actuator 20 is the extension direction, the resistance load due to the friction force F acts in the contraction direction of the electromagnetic actuator 20, and when the operation direction of the electromagnetic actuator 20 is the contraction direction, the friction force F The resistance load due to the above acts in the extending direction of the electromagnetic actuator 20.

Therefore, when the operation direction of the electromagnetic actuator 20 is the extension direction, the suspension ECU 100 corrects the target actuator force f _act ^* in the extension direction so as to compensate for the resistance load due to the friction force F in step S64. Increase by Δf. In the electromagnetic actuator 20, a force that operates in the extension direction is represented by positive, and a force that operates in the contraction direction is represented by negative. Therefore, in step S64, by directly adding the correction load Delta] f to the target actuator force f _act ^*, obtaining a final target actuator force ^{_{f act * (f act * ←}} f act * + Δf).

On the other hand, when the operation direction of the electromagnetic actuator 20 is the contraction direction, the target actuator force f _act ^* is increased by the correction load Δf in the contraction direction so as to compensate the resistance load due to the frictional force F in step S65. . In this case, shrinkage since the force has a negative value, by subtracting the correction load Δf to the target actuator force f _act ^*, obtaining a final target actuator force ^{_{f act * (f act * ←}} f act * -Δf).

Accordingly, the correction load Δf added to the target actuator force f _act ^* is a value corresponding to the rotational speed ω, as shown in FIG. Thus, when the final target actuator force f _act ^* is calculated, the suspension ECU 100 outputs a control signal corresponding to the target actuator force f _act ^* in step S66. That is, a control amount (target energization amount and rotation direction) of the electric motor 30 is determined based on the target actuator force f _act ^* , and a PWM control signal having a duty ratio corresponding to the determined control amount is switched by the motor drive circuit 73. Output to the element.

When the suspension ECU 100 performs the process of step S66, the actuator force control routine is temporarily terminated. Then, the actuator force control routine is repeated at a very short cycle. When such processing is repeated and the timer value Tim reaches the set timer value Tmax, that is, when the set time has elapsed from the start of the vehicle, the determination in step S56 becomes “Yes”, and the flag FL is set to “1” in step S57. Is changed from “0” to “0”, and the process proceeds to step S66. Accordingly, after that, the correction process of the target actuator force f _act ^* is not performed.

According to the suspension device of the present embodiment described above, the vehicle environment temperature is detected at the time of starting the vehicle, and when the detected temperature Tx is lower than the threshold Tref for low temperature determination, the electromagnetic actuator 20 is step-driven to perform friction. The force F is measured, and the target actuator force f _act ^* is corrected by a correction load Δf corresponding to the friction force F. Therefore, the target actuator force f _act ^* becomes appropriate, and it is possible to suppress a decrease in riding comfort and a decrease in steering stability due to frictional forces.

  In addition, the measurement of the friction force F can be easily performed because it is calculated from the rotation angle of the electric motor 30 when the electric motor 30 is driven with a preset friction measurement driving force.

In the present embodiment, only when the vehicle is started in a low temperature environment, the frictional force F is measured, for correcting the target actuator force f _act ^* according to the frictional force F, the detection of the frictional force F Can be minimized, and the calculation burden on the suspension ECU 100 can be reduced. Further, after the vehicle is started, the viscosity of the grease of the electromagnetic actuator 20 decreases, so that the target actuator force f _act ^* is corrected only until a predetermined time elapses after the vehicle is started. For this reason, the target actuator force f _act ^* becomes more appropriate.

In calculating the correction load Δf for correcting the target actuator force f _act ^* , the correction load Δf is calculated such that the smaller the rotational speed | ω | of the electric motor 30 is, the smaller the correction load Δf is. Therefore, sudden fluctuations in the actuator force when the moving direction of the electromagnetic actuator 20 is reversed are suppressed, and the ride comfort can be further improved. For example, when the correction load Δf is set based only on the movement direction of the electric actuator without being associated with the rotation speed | ω | of the electric motor 30, the movement direction of the electromagnetic actuator 20 is reversed as shown in FIG. The sign of the correction load is reversed at the moment, and the actuator force is likely to fluctuate rapidly. On the other hand, in this embodiment, the magnitude of the correction load Δf is set to be smaller as the rotational speed | ω | of the electric motor 30 is smaller. Therefore, as shown in FIG. Before the direction of motion changes, it gradually decreases as the rotational speed decreases, and after the rotational direction is reversed, it gradually increases as the rotational speed increases. Therefore, sudden fluctuations in the actuator force are suppressed, and riding comfort is improved.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect is employable in the range which does not deviate from the summary of this invention. For example, in the present embodiment, the frictional force F is calculated only at the low temperature start and the target actuator force is corrected. However, it is not necessarily required only at the low temperature start. For example, regardless of the environmental temperature of the vehicle, the frictional force F may be calculated when the vehicle is started, and the target actuator force may be corrected by the frictional force F. In this case, steps S11 to S13 in FIG. 4 may be omitted.

  In this embodiment, the smaller the rotational speed | ω | of the electric motor 30 is, the smaller the correction load Δf is set. However, it is not always necessary to do so, and as shown in FIG. The load Δf may be a constant value. Further, it is not necessary to change the correction load Δf linearly with respect to the change in the rotational speed | ω |, and it may be changed in stages.

  Further, in the present embodiment, the hydraulic damper device 60 is incorporated in the suspension body 10, but a configuration in which the hydraulic damper device 60 is not provided may be employed.

In this embodiment, the target actuator force f _act ^* that suppresses the vertical vibration of the sprung portion SU and the unsprung portion SD is calculated based on the sprung speed V2 and the unsprung speed V1. The actuator force f _act ^* is not limited to this. For example, a roll suppression component based on the lateral acceleration of the vehicle body B or a pitch suppression component based on the longitudinal acceleration of the vehicle body can be added. Further, the target actuator force f _act ^* may be calculated in consideration of the transfer characteristic of the hydraulic damper device 60.

DESCRIPTION OF SYMBOLS 10 ... Suspension main body, 20 ... Electromagnetic actuator, 30 ... Electric motor, 40 ... Ball screw mechanism, 41 ... Ball screw shaft, 42 ... Ball screw nut, 50 ... Spring device, 52 ... Coil spring, 60 ... Hydraulic damper device, 71 ... Unsprung acceleration sensor, 72 ... Spring acceleration sensor, 73 ... Motor drive circuit, 74 ... Rotation angle sensor, 75 ... Temperature sensor, 100 ... Suspension ECU, B ... _Car body, fact ^* ... Target actuator force, Δf ... Correction load, F ... friction force, G1 ... unsprung acceleration, G2 ... unsprung acceleration, SD ... unsprung, SU ... unsprung, V1 ... unsprung velocity, V2 ... unsprung velocity, Tx ... detected temperature, θm ... rotation Angle, ω ... rotational speed.

Claims (4)

A suspension spring that elastically connects the sprung portion and the unsprung portion of the vehicle;
An electric motor which is arranged in parallel with the suspension spring between the sprung portion and the unsprung portion and generates an actuator force which is a driving force and a damping force for relative movement between the sprung portion and the unsprung portion; An electromagnetic actuator;
Target actuator force calculating means for calculating a target actuator force that is a target value of the actuator force;
A vehicle suspension device comprising: drive control means for driving and controlling the electric motor based on the target actuator force calculated by the target actuator force calculation means;
Friction force calculating means for driving the electric motor with a friction measurement driving force set in advance when starting the vehicle, and calculating the friction force of the electromagnetic actuator from the rotation angle of the electric motor at that time;
A vehicle suspension device comprising: a target actuator force correcting unit that corrects the target actuator force based on the frictional force calculated by the frictional force calculating unit. Temperature determining means for determining whether the vehicle is started in a low temperature environment,
2. The vehicle according to claim 1, wherein the frictional force calculating means and the target actuator force correcting means operate when the temperature determining means determines that the vehicle is started in a low temperature environment. Suspension device.   The vehicle suspension apparatus according to claim 1 or 2, wherein the target actuator force correcting means corrects the target actuator force only for a predetermined period from the start of the vehicle.   The target actuator force correction means sets the correction amount for correcting the target actuator force so that the smaller the rotation speed is, the smaller the rotation speed of the electric motor is within a predetermined threshold value. The vehicle suspension device according to any one of claims 1 to 3, characterized in that:

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