JP2005096587A - Vehicle suspension system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle suspension device capable of realizing a vehicle excellent in riding comfort.
An electromagnetic suspension 4 includes a coil spring 22 that elastically supports an unsprung portion on a spring, a shock absorber 80 that generates a damping force between the unsprung portion and the unsprung portion, and an upper that couples the shock absorber 80 to a vehicle body. Support 70 is provided. The shock absorber 80 controls the damping force by rotating the ball screw 24 by the motor 20 and sliding the rod 28 and the outer shell 30 up and down. High frequency vibrations that cannot be absorbed by the shock absorber 80 are absorbed by the vibration absorbing means 50 of the upper support 70. The vibration absorbing means 50 is configured to be variable in rigidity, and the rigidity is controlled according to an input from the road surface.
[Selection] Figure 2

Description

  The present invention relates to a vehicle suspension device, and more particularly to a vehicle suspension device that controls an absorber disposed between a spring on a vehicle and an unspring basis by a motor.

An electric motor type electromagnetic suspension has been proposed as a vehicle suspension device (see, for example, Patent Document 1). In the vehicle suspension device disclosed in Patent Document 1, a male screw member and a female screw member that mesh with each other are driven to extend and contract by a motor to actively control the damping force between the sprung and unsprung portions. When a shocking load is input from the wheel, at least one of the motor and the screw member is elastically supported on the wheel or the vehicle body by a spring such as a coil spring in order to absorb the load.
JP 2001-180244 A JP-A-8-197931

  In conventional electromagnetic suspensions, when high-frequency vibration is input from the road surface due to the influence of the inertia force of the motor, etc., the drive of the motor cannot follow, and the vibration may be transmitted to the vehicle body and affect the riding comfort. . Technology that improves ride comfort while ensuring steering stability is required.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a vehicle suspension device capable of realizing a vehicle having excellent riding comfort.

  One embodiment of the present invention relates to a vehicle suspension apparatus. The vehicle suspension device includes an absorber disposed between a spring and an unspring of a vehicle, a motor that contributes to control of the absorber, an upper support that couples the absorber on the spring, Rigidity changing means for changing the rigidity of the upper support in accordance with a vibration state.

  The rigidity changing means may reduce the rigidity when vibrations having a frequency higher than a predetermined threshold value under the spring exceeds a predetermined level. When the vibration input from the road surface is a high frequency of, for example, 5 Hz or more, the rigidity may be lowered to make it easier to absorb the vibration. Thereby, riding comfort can be improved.

  The rigidity changing means may be a piezoelectric element or an MR fluid provided inside the upper support. The rigidity of the upper support can be changed by utilizing expansion / contraction of the piezoelectric element by application of an electric field or change in viscosity of the MR fluid by application of a magnetic field. Thereby, a rigidity change means can be comprised simply.

  The rigidity changing means may change the rigidity of the upper support using regenerative electric power generated by the rotation of the motor accompanying the operation of the absorber. Thereby, power consumption can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which implement | achieves the vehicle excellent in riding comfort can be provided.

(First embodiment)
FIG. 1 shows a configuration of a vehicle 1 according to an embodiment of the present invention. The vehicle 1 includes a vehicle body 2, a wheel 3a that is a left front wheel, a wheel 3b that is a right front wheel, a wheel 3c that is a left rear wheel, and a wheel 3d that is a right rear wheel (hereinafter collectively referred to as "wheel 3" as appropriate). Prepare. The wheel 3 is composed of a wheel and a rubber tire. The vehicle body 2 and the wheels 3 are connected to each other via an electromagnetic suspension which is an example of a vehicle suspension device provided with an absorber that generates a spring force and an unsprung damping force of the vehicle 1 using a motor. The position of the member supported by the spring of the electromagnetic suspension is referred to as “sprung”, and the position of the member not supported by the spring is referred to as “unsprung”. That is, the sprung is on the vehicle body 2 side, and the unsprung is on the wheel 3 side. In this example, the wheel 3a is attached to the electromagnetic suspension 4a, the wheel 3b is attached to the electromagnetic suspension 4b, the wheel 3c is attached to the electromagnetic suspension 4c, and the wheel 3d is attached to the electromagnetic suspension 4d. Hereinafter, the electromagnetic suspensions 4a, 4b, 4c, and 4d are collectively referred to as “electromagnetic suspension 4”. Each electromagnetic suspension 4 is independently controlled by an electronic control device (hereinafter, the electronic control device is referred to as “ECU”) 10. The ECU 10 includes a CPU, a RAM, and a ROM.

  The current flowing through the motor of the electromagnetic suspension 4 is detected by a current sensor. A current sensor 5a is provided for the electromagnetic suspension 4a, a current sensor 5b is provided for the electromagnetic suspension 4b, a current sensor 5c is provided for the electromagnetic suspension 4c, and a current sensor 5d is provided for the electromagnetic suspension 4d. Hereinafter, the current sensors 5a, 5b, 5c, and 5d are collectively referred to as “current sensor 5”. The detection result of each current sensor 5 is transmitted to the ECU 10. The current detection function by the current sensor 5 may be realized by the ECU 10.

  By providing the electromagnetic suspension 4 for each wheel 3, the ECU 10 can independently control the current applied to the motor of the electromagnetic suspension 4 according to the state of each wheel 3. Further, by adopting the electromagnetic suspension 4, it is possible to realize control with excellent responsiveness.

  An acceleration sensor is provided in order to detect the vertical acceleration of the vehicle 1 above or below the spring. In this example, an acceleration sensor 6a is provided near the wheel 3a, an acceleration sensor 6b is provided near the wheel 3b, an acceleration sensor 6c is provided near the wheel 3c, and an acceleration sensor 6d is provided near the wheel 3d. Hereinafter, the acceleration sensors 6a, 6b, 6c, and 6d are collectively referred to as “acceleration sensor 6”. The vertical acceleration detected by the acceleration sensor 6 is transmitted to the ECU 10 and used to control the rigidity of the upper support, as will be described later. The acceleration sensor 6 may be provided on the spring, may be provided below the spring, or may be provided on both sides. In the present embodiment, the acceleration sensor 6 is provided in accordance with the vibration input from the road surface. In order to control the rigidity of the support, it is preferable to provide the acceleration sensor 6 under the spring near the road surface. In the example of FIG. 1, the acceleration sensor 6 is provided for each wheel 3, but the acceleration sensor 6 may be one or plural.

  FIG. 2 shows the configuration of the electromagnetic suspension 4. The electromagnetic suspension 4 includes a motor 20, a ball screw 24, a ball screw nut 26, a rod 28, an outer shell 30, bearings 32, 34 and 36, a dust seal 38 and a rotation angle sensor 44, and a spring under the spring. A coil spring 22 elastically supported on the upper side and an upper support 70 for coupling the shock absorber 80 to the vehicle body 2 are provided. The bearing 32 rotatably supports the ball screw 24 inside the rod 28, and the bearings 34 and 36 support the rod 28 slidably inside the outer shell 30. The dust seal 38 prevents foreign matters such as dust from entering the outer shell 30. The rotation angle sensor 44 detects the amount of rotation of the motor 20. The detection result of the rotation angle sensor 44 is transmitted to the ECU 10. The rotation angle sensor 44 may be provided outside the motor 20 or may be provided inside the motor 20. The electromagnetic suspension 4 is attached to the configuration on the vehicle body 2 side at the first attachment portion 40, and is attached to the configuration on the wheel 3 side at the second attachment portion 46. The coil spring 22 is contracted between the body surface in the vicinity of the first mounting portion 40 and the spring seat 42, and is given a predetermined load in advance.

  The coil spring 22 supports the weight of the sprung portion of the vehicle 1 and prevents vibrations and shocks from the road surface from being transmitted to the vehicle body 2 through the wheels 3. The shock absorber 80 attenuates the vertical vibration of the vehicle body 2 caused by the coil spring 22. The shock absorber 80 can generate a damping force between the sprung and unsprung parts of the vehicle 1 using the motor 20 and has excellent control response.

  The ball screw 24, the rod 28 and the outer shell 30 are arranged coaxially. The outer shell 30 is internally provided with a ball screw nut 26 having a female screw portion. The ball screw 24 has a male screw portion and is in a state of being screwed into the ball screw nut 26. The motor 20 supports one end of the ball screw 24 by serration so as to be rotatable. When the motor 20 is driven, the ball screw 24 rotates relative to the ball screw nut 26, and the outer shell 30 is pushed downward or lifted upward with respect to the motor 20. In this embodiment, an example in which the ball screw 24 is provided on the vehicle spring and the ball screw nut 26 is provided below the vehicle spring will be described. Conversely, the ball screw 24 is provided below the vehicle spring. A screw nut 26 may be provided on the spring of the vehicle.

  When the vehicle 1 is traveling on a good road, the ECU 10 sets the current value applied to the motor 20 of each electromagnetic suspension 4 to a reference current value, for example, 0A. When the road surface is uneven and the wheel 3 moves up and down, the coil spring 22 expands and contracts due to the relative movement between the rod 28 and the outer shell 30. At this time, when the ball screw 24 rotates relative to the ball screw nut 26, the motor 20 rotates and acts as a generator, and a damping force is generated by the resistance force generated at this time. The current sensor 5 detects a current generated by electromagnetic induction inside the motor 20 and transmits it to the ECU 10. The ECU 10 applies to the motor 20 a current in a direction that suppresses expansion and contraction of the coil spring 22, that is, a current that is opposite to the current generated by electromagnetic induction. ECU10 sets the electric current applied to the motor 20 according to the acceleration of the up-down direction of the vehicle body 2, and adjusts damping force. Thus, the shock absorber 80 of the present embodiment functions as an electromagnetic shock absorber. Further, since the vehicle body 2 can be displaced in the vertical direction by rotating the ball screw 24, the shock absorber 80 of the present embodiment can be used for controlling the posture of the vehicle body 2.

  The shock absorber 80 is controlled by the rotation of the motor 20. However, since inertial force acts on the rotor of the motor 20, when high-frequency vibration is input from the road surface, the control cannot follow, and the vehicle body 2 is vibrated. There is a case where the ride comfort is worsened. Therefore, in this embodiment, in order to absorb high-frequency vibration, the shock absorber 80 is coupled to the vehicle body 2 via the upper support 70 including the vibration absorbing means 50 made of an elastic body such as rubber. When the rigidity of the vibration absorbing means 50 is increased, the steering stability is increased, but the road surface input is easily transmitted to the vehicle body 2. Conversely, if the rigidity of the vibration absorbing means 50 is lowered, the ride comfort is improved, but the steering stability is deteriorated. Thus, steering stability and ride comfort are in a trade-off relationship, and the rigidity of the vibration absorbing means 50 needs to be determined in consideration of them, but in this embodiment, the rigidity of the vibration absorbing means 50 is determined. It is configured to be changeable, and its rigidity is controlled according to the state of vibration input from the road surface. As a result, it is possible to achieve both excellent handling stability and comfortable riding comfort.

  FIG. 3 shows the configuration of the upper support 70. Inside the vibration absorbing means 50, piezoelectric elements 52a and 52b which are examples of rigidity changing means are provided vertically. A clearance 54 is provided between the piezoelectric elements 52a and 52b. When an electric field is applied, the width of the clearance 54 increases or decreases as the piezoelectric elements 52a and 52b expand and contract. Thereby, the rigidity of the upper support 70 can be changed. Specifically, when the vibration input from the road surface is a high frequency, the rigidity of the upper support 70 is lowered by widening the clearance 54 in order to absorb the vibration by the upper support 70. Thereby, a comfortable riding comfort can be ensured. When the vibration input from the road surface has a low frequency, the shock absorber 80 absorbs the vibration, and the clearance 54 is narrowed to increase the rigidity of the upper support 70. Thereby, steering stability can be ensured.

  FIG. 4 shows a dynamic model of the vehicle 1 of the present embodiment. The shock absorber 80 and the upper support 70 are connected in series, and support the mass m3 of the vehicle body 2 together with the coil spring 22 connected in parallel with them. The vibration absorbing means 50 of the upper support 70 can be regarded as a spring having a variable spring constant and a viscous damping having a variable viscosity coefficient.

FIG. 5 is a flowchart showing a method for changing the rigidity of the upper support 70 in the electromagnetic suspension 4 of the present embodiment. First, vibration input from the road surface is detected by the acceleration sensor 6 (S10). Instead of the acceleration sensor 6, the rotation amount of the ball screw 24 is acquired by the current detected by the current sensor 5 or by the rotation angle sensor 44, the stroke amount is calculated from the rotation amount, and the stroke amount is differentiated twice with respect to time. Thus, the acceleration in the vertical direction may be calculated. When the ECU 10 acquires acceleration in the vertical direction from the acceleration sensor 6, the high-pass filter extracts a high frequency component of, for example, 5 Hz or more (S12), and the magnitude of the electric field applied to the piezoelectric element according to the level of the high frequency component. To control the rigidity of the upper support 70 (S14). For example, when the amplitude of a high frequency component of 5 Hz or more is larger than a predetermined threshold, the rigidity is lowered to easily absorb vibration, and the amplitude of the high frequency component of 5 Hz or more is smaller than a predetermined threshold. Increases rigidity and ensures steering stability.
(Second Embodiment)
FIG. 6 shows the configuration of the upper support 70 according to the second embodiment. In the present embodiment, an example will be described in which an MR fluid (Magneto-Rheological Fluid) provided in the upper support 70 functions as rigidity changing means. The overall configuration of the vehicle 1 and the configuration of the electromagnetic suspension 4 of the present embodiment are the same as those of the vehicle 1 and the electromagnetic suspension 4 of the first embodiment shown in FIGS.

An MR fluid 56 is injected into the vibration absorbing means 50 of the upper support 70. Considering that the vibration absorbing means 50 compresses when vibration is input from the road surface, the MR fluid is not injected so as to fill the flow path, but a gap 58 is provided so as to leave room for compression. It has been. When a current is supplied to the coil 60 provided inside the MR fluid 56 via the harness 62, a magnetic field is generated around the MR fluid 56. The MR fluid 56 is a slurry in which ferromagnetic metal fine particles are dispersed at a high concentration in a liquid as a medium. When an external magnetic field is applied, the magnetized particles strongly attract each other and become highly viscous. Have. For this reason, the magnetic field generated around the coil 60 increases the viscosity of the MR fluid 56 and increases the rigidity of the upper support 70. Thus, the rigidity of the upper support 70 can be adjusted by adjusting the current supplied to the coil 60. The method for changing the rigidity of the upper support 70 is the same as in the first embodiment.
(Third embodiment)
In the present embodiment, the rigidity of the upper support 70 described in the first and second embodiments is controlled using the regenerative power generated by the motor 20. FIG. 7 schematically shows how regenerative power is supplied to the upper support 70. When the motor 20 rotates with the operation of the shock absorber 80 by the input from the road surface, the generated back electromotive force is stored in the capacitor C. When the rigidity of the upper support 70 needs to be controlled, a current is supplied from the capacitor C to the upper support 70. Thereby, control can be performed by effectively using regenerative power, and power consumption of a battery or the like provided in the vehicle 1 can be reduced.

  When regenerative electric power is generated by input from the road surface, the electric power may be supplied to the upper support 70 immediately or at a predetermined time interval to change the rigidity of the upper support 70. Accordingly, the rigidity of the upper support 70 can be automatically changed without using the ECU 10 or the like, so that the configuration can be simplified.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention.

It is a figure which shows the structure of the vehicle which concerns on 1st Embodiment. It is a figure which shows the structure of the electromagnetic suspension which concerns on 1st Embodiment. It is a figure which shows the structure of the upper support which concerns on 1st Embodiment. It is a figure which shows the dynamic model of the vehicle which concerns on 1st Embodiment. It is a flowchart which shows the method to change the rigidity of an upper support in the electromagnetic suspension which concerns on 1st Embodiment. It is a figure which shows the structure of the upper support which concerns on 2nd Embodiment. It is a figure which shows typically a mode that regenerative electric power is supplied to an upper support.

Explanation of symbols

  1 vehicle, 2 vehicle body, 3 wheels, 4 electromagnetic suspension, 5 current sensor, 6 acceleration sensor, 10 ECU, 20 motor, 22 coil spring, 24 ball screw, 26 ball screw nut, 28 rod, 30 outer shell, 50 vibration absorption Means, 52 piezoelectric element, 54 clearance, 56 MR fluid, 60 coils, 70 upper support, 80 shock absorber.

Claims (4)

An absorber disposed between the sprung and unsprung parts of the vehicle;
A motor that contributes to the control of the absorber;
An upper support for coupling the absorber on the spring;
Rigidity changing means for changing the rigidity of the upper support according to the vibration state of the unsprung;
A vehicle suspension device comprising:   2. The vehicle suspension according to claim 1, wherein the rigidity changing unit lowers the rigidity when a vibration having a frequency higher than a predetermined threshold value under the spring exceeds a predetermined level. apparatus.   The vehicle suspension system according to claim 1 or 2, wherein the rigidity changing means is a piezoelectric element or an MR fluid provided inside the upper support.   4. The vehicle suspension device according to claim 1, wherein the rigidity changing unit changes the rigidity of the upper support using regenerative electric power generated by the rotation of the motor accompanying the operation of the absorber. 5. .

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