JP2007008373A - Suspension characteristic computing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a design index of a suspension considering a correlation between a roll and a pitch. <P>SOLUTION: The suspension characteristic computing method includes a first step (S1) computing a pitch moment by the geometry of a suspension as the sum of vertical force on a front wheel side by the product of a geometry proportionality factor on the front wheel side and the square of tire lateral force, and vertical force on a rear wheel side by a geometry proportionality factor on a rear wheel side and the square of the tire lateral force; a second step (S2) computing a pitch moment due to damping force of the suspension as the product of a damping force proportionality factor and a roll rate; a third step (S3) computing a pitch angle as the product of the sum of the computed two pitch moments and a gain and of the pitch angle and the phase delay of the pitch angle to the pitch moments; and forth steps (S4, S5) computing the phase difference between the pitch angle and a roll angle from the computed pitch angle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a suspension characteristic calculation method for improving a roll feeling.

  When designing a vehicle suspension, various design indexes have been proposed in order to improve steering stability. Steering stability is greatly affected by the movement of a vehicle body such as a roll generated during steering. Roll feeling is evaluated as a feeling evaluation (sensory evaluation) of the movement of the vehicle body. It has been found that the roll and pitch generated during steering are important as affecting the roll feeling. Therefore, in order to improve the steering stability, the suspension is designed with a design index considering the roll and a design index considering the pitch.

Some vehicles have an active suspension that dynamically controls the suspension in order to improve steering stability. In the active suspension, the behavior of the vehicle is detected from the suspension stroke or the like, and the hydraulic pressure of the absorber is controlled so as to achieve the target roll characteristics and pitch characteristics (see Patent Document 1).
Japanese Patent Publication No. 5-45442

  However, in the conventional suspension design, the design index considering the roll and the design index considering the pitch are separately examined, and the correlation between the roll and the pitch is not considered. Therefore, there are cases where sufficient steering stability cannot be obtained. In the case of the active suspension, there is a case where sufficient steering stability cannot be obtained because the control is not performed in consideration of the correlation between the roll and the pitch.

  Therefore, an object of the present invention is to provide a suspension design index that takes into account the correlation between roll and pitch.

  The suspension characteristic calculation method according to the present invention is a product of the pitch moment due to the suspension geometry, which is the product of the geometric proportionality factor determined from the front wheel geometry and the square of the tire lateral force on the front wheel set based on the basic vibration of the roll angle. Is generated on the rear wheel side by the product of the vertical force generated on the front wheel side by the geometry and the geometric proportionality coefficient determined from the geometry on the rear wheel side and the square of the tire lateral force on the rear wheel side set based on the basic vibration of the roll angle The first step of calculating as the sum of the vertical force and the second step of calculating the pitch moment due to the damping force of the suspension as the product of the damping force proportional coefficient determined by the difference in the damping force characteristics of the front and rear wheel suspensions and the roll rate And the pitch angle in the second step and the pitch moment due to the suspension geometry calculated in the first step. The third step of calculating as the product of the sum of the pitch moment due to the damping force of the suspended suspension, the gain of the pitch angle with respect to the pitch moment and the phase delay of the pitch angle, and the pitch angle and roll angle from the pitch angle calculated in the third step And a fourth step of calculating a phase difference between the first and second phases.

  This suspension characteristic calculation method pays attention to the fact that it is possible to improve the roll feeling during steering (and thus the steering stability) by synchronizing the generation timing of the roll and the pitch. Ask for. For this reason, in the suspension characteristic calculation method, the vertical force during turning caused by the suspension geometry (particularly the roll center geometry), which is the main factor that generates pitch during steering, is caused by the difference between the front and rear wheels. The pitch moment generated by the difference in the vertical force during turning caused by the difference in the expansion between the braking moment and the damping force of the suspension (especially the damping force of the absorber) is obtained for each of the front wheels and the rear wheels. From the pitch angle, the phase difference between the pitch angle and the roll angle is obtained. Specifically, in the first step, a product of the geometric proportionality coefficient determined from the front wheel side geometry and the square of the tire lateral force on the front wheel side set based on the basic vibration of the roll angle (the upper and lower generated on the front wheel side). Force) multiplied by the geometric proportionality factor determined from the rear wheel geometry and the square of the tire lateral force on the rear wheel side set based on the basic vibration of the roll angle (the vertical force generated on the rear wheel side) Add to find the pitch moment due to the suspension geometry. Also, in the second step, the pitch moment due to the damping force of the suspension is obtained by multiplying the roll force by the damping force proportional coefficient determined by the difference between the damping force characteristics of the front and rear wheel suspensions. Then, in the third step, the pitch angle is obtained by multiplying the added value (pitch moment) of the pitch moment by the suspension geometry and the pitch moment by the suspension damping force by the gain of the pitch angle with respect to the pitch moment and the phase delay. Furthermore, a conditional expression that represents the phase difference between the pitch angle and the roll angle from the obtained pitch angle by the fourth step (including the geometric characteristics, damping force characteristics, roll dynamic characteristics, pitch dynamic characteristics, etc. necessary for suspension design). Ask for. Using this conditional expression to express the phase difference, the suspension is designed so that the phase difference is zero in order to synchronize the roll and pitch generation timing (geometry characteristics, damping force characteristics, roll dynamic characteristics, pitch dynamic characteristics). Etc.) As described above, in the suspension characteristic calculation method, a condition considering the correlation between the roll and the pitch can be obtained, and from this condition, a suspension that improves the roll feeling (steering stability) can be designed.

  The suspension characteristic calculation method of the present invention may be configured to calculate the tire lateral force based on a roll angle delay time with respect to the tire lateral force.

  In the first step of the suspension characteristic calculation method, the tire lateral force is obtained in consideration of the roll angle delay time with respect to the tire lateral force generated during steering with respect to the basic vibration of the roll angle. As a result, the pitch moment due to the suspension geometry can be obtained with high accuracy.

  In the suspension characteristic calculation method of the present invention, the geometric proportionality coefficient is set to a larger value as the height of the roll center is higher.

  In the first step of the suspension characteristic calculation method, the proportionality factor of the geometry is set to a larger value as the height of the roll center is higher. Therefore, the higher the roll center, the greater the pitch moment due to the suspension geometry.

  In the suspension characteristic calculation method of the present invention, the damping force proportional coefficient is set to a larger value as the difference in the damping force characteristics of the suspensions of the front and rear wheels is larger.

  In the second step of the suspension characteristic calculation method, the damping force proportional coefficient is set to a larger value as the difference between the damping force characteristics of the front and rear wheel suspensions increases. Accordingly, the greater the difference in the damping force characteristics of the front and rear wheel suspensions, the greater the pitch moment due to the suspension damping force.

  In the suspension characteristic calculation method of the present invention, the phase difference between the pitch angle and the roll angle may be obtained from the coefficient of the quadratic component of the Fourier expansion of the pitch angle calculated in the third step.

  In the fourth step of the suspension characteristic calculation method, since the fundamental frequency of the pitch at the time of steering is twice that of the roll, the pitch angle obtained in the third step is Fourier transformed, and the coefficient of the secondary component of the Fourier expansion. Is used to determine the phase difference between the pitch angle and the roll angle. In this way, the condition can be expressed by a simple expression by obtaining the phase difference only by the secondary component of the Fourier expansion that most affects the pitch.

  In the suspension characteristic calculation method of the present invention, the damping force characteristics of the front and rear wheel suspensions may be the difference between the front wheel differential pressure difference and the rear wheel differential pressure difference.

  In this suspension characteristic calculation method, the damping force characteristic of the suspensions of the front and rear wheels is the difference between the tension difference between the front wheels and the tension difference between the rear wheels, so that the phase difference between the pitch angle and the roll angle is zero. By appropriately setting the difference between the pressure difference and the rear wheel pressure difference, it is possible to synchronize the generation timing of the roll and the pitch.

  In the suspension characteristic calculation method of the present invention, the basic vibration of the roll angle is the vibration of the roll angle in the roll motion of the vehicle caused by the driver's steering input.

  In this suspension characteristic calculation method, since the basic vibration of the roll angle is the vibration of the roll angle in the roll motion of the vehicle caused by the driver's steering input, the cycle of the roll motion and the pitch motion of the vehicle generated by the driver's steering input. Can be obtained in an appropriate relationship, and the conditions considering the correlation between the roll and the pitch can be obtained with high accuracy.

  According to the present invention, it is possible to provide a suspension design index in consideration of the correlation between the roll and the pitch, and it is possible to improve the roll feeling (steering stability) by designing the suspension according to this design index. .

  Hereinafter, an embodiment of a suspension characteristic calculation method according to the present invention will be described with reference to the drawings.

  In this embodiment, first, the timing between the roll and the pitch will be described, and then the suspension design for synchronizing the generation timing between the roll and the pitch will be described. In the suspension design according to the present embodiment, a case where the suspension design is applied to a normal suspension without an active suspension will be described.

  The timing between the roll and the pitch will be described with reference to FIGS. FIG. 1 is a diagram illustrating a Lissajous waveform of a roll angle and a pitch angle of a vehicle having a high sensory evaluation of a roll feeling, where (a) is an example of a highly evaluated vehicle, and (b) is a highly evaluated vehicle. Another example. FIG. 2 is a diagram illustrating a Lissajous waveform of a roll angle and a pitch angle of a vehicle with a low sensory evaluation of a roll feeling, where (a) is an example of a low evaluation vehicle and (b) is a high evaluation vehicle. It is another example. FIG. 3 is a diagram illustrating a time change of a roll angle and a time change of a pitch angle of a vehicle having a high sensory evaluation of a roll feeling. FIG. 4 is a diagram illustrating a time change of a roll angle and a time change of a pitch angle of a vehicle having a low sensory evaluation of the roll feeling.

  When designing a suspension, steering stability at the time of steering is important, and the movement of the vehicle body such as a roll and a pitch generated at the time of steering greatly affects the steering stability. A roll feeling is used for the feeling evaluation (sensory evaluation) of the movement of the vehicle body. As a result of analyzing the sensory evaluation of the roll feeling of a test driver who specializes in steering stability evaluation, it was found that the part of the roll feeling is felt visually and the relationship between roll and pitch is important.

  Therefore, an evaluation was conducted focusing on the relationship between roll and pitch using a plurality of vehicles having different suspension characteristics. In this evaluation, each vehicle was steered with the same steering pattern, and the movement of the vehicle body such as roll and pitch was measured, and the vehicle occupant performed sensory evaluation such as roll feeling. FIG. 1 and FIG. 2 show Lissajous waveforms with the horizontal axis representing the roll angle and the vertical axis representing the pitch angle. FIG. 1 shows an example of a Lissajous waveform of two vehicles having a high sensory evaluation, and it can be seen that the hysteresis of the Lissajous waveform is small. In the case of the vehicle shown in FIG. 1, the sensory evaluation showed that the line of sight was less disturbed and the roll feeling was good. FIG. 2 shows an example of a Lissajous waveform of two vehicles with low sensory evaluation, and it can be seen that the hysteresis of the Lissajous waveform is large.

  The hysteresis in this Lissajous waveform means the time difference between the roll angle and the pitch angle, and it has been clarified that the smaller the hysteresis, the better the roll feeling. FIG. 3 shows an example of the relationship between the time change RA1 of the roll angle and the time change PA1 of the pitch angle in a vehicle having a high sensory evaluation, and the time difference (phase difference) between the roll angle and the pitch angle is small. I understand. FIG. 4 shows an example of the relationship between the time change RA2 of the roll angle and the time change PA2 of the pitch angle in a vehicle having a low sensory evaluation, and the time difference (phase difference) between the roll angle and the pitch angle is large. I understand. From the above evaluation, it can be seen that the smaller the time difference between the roll angle and the pitch angle during steering, the better the roll feeling, and in order to improve steering stability, it is most desirable to synchronize the generation timing of the roll and pitch. It was.

  The suspension design according to the present embodiment will be described with reference to FIGS. FIG. 5 is an explanatory diagram of the roll center, instantaneous center, tire lateral force, and vertical force. FIG. 6 is a diagram showing the relationship between the pitch moment and the pitch angle. FIG. 7 is a diagram showing the relationship between the time change of the pitch angle and the time change of the pitch moment. FIG. 8 is a diagram illustrating a relationship between a change in roll angle with time and a change in tire lateral force with time. FIG. 9 is an explanatory diagram of the pitch moment resulting from the geometry of the suspension. (A) shows tire lateral force and vertical force on the front wheel side, (b) shows tire lateral force and vertical force on the rear wheel side, and (c) shows front and rear vertical force and pitch moment. FIG. 10 is an explanatory diagram of the pitch moment resulting from the damping force of the suspension. (A) shows the front wheel side damping force and vertical force, (b) shows the rear wheel side damping force and vertical force, and (c) shows the front and rear vertical force and pitch moment.

  In this suspension design, a conditional expression of the generation mechanism of the roll and the pitch is derived, and the suspension is designed to synchronize the generation timing of the roll and the pitch by this conditional expression. In this embodiment, in order to perform suspension design, a suspension design program is executed on a computer such as a personal computer, thereby executing first pitch moment calculation processing, second pitch moment calculation processing, pitch angle calculation processing, and Fourier transform. The suspension is designed by performing processing, time difference calculation processing, and suspension design processing.

  The first pitch moment calculation process will be described. There are two main factors that generate a pitch during steering, and one of them is a pitch moment that occurs when the vertical force during turning due to the roll center geometry (suspension geometry) differs between the front and rear. As shown in FIG. 5 (an example of the case of turning left), during turning, tire lateral forces RFL and RFR are generated on the left and right wheels around the instantaneous centers MCL and MCR. The instantaneous centers MCL and MCR are the intersections of the extension lines of the upper arm UA and the lower arm LA of the suspension, and the roll center RC is the instantaneous center MCR of the right wheel and the line connecting the instantaneous center MCL of the left wheel and the ground center of the tire of the left wheel. And the line connecting the ground contact center of the right wheel tire.

  Thus, since the tire lateral forces RFL and RFR act around the instantaneous centers MCL and MCR, vertical forces VFL and VFR are also generated on the left and right wheels as their component forces. Since the positions of the instantaneous centers MCL and MCR change every moment during the turn, they are different positions on the left and right wheels. Therefore, the tire lateral forces RFL and RFR are different between the left and right wheels, and the vertical forces VFL and VFR are also different. As a result, as shown in FIGS. 9A and 9B (an example in the case of turning left), the front wheel side and the rear wheel side are moved up and down by the difference between the left wheel vertical force VFL and the right wheel vertical force VFR. Forces FVF1 and RVF1 act. As shown in FIG. 9C, a pitch moment JPM corresponding to the geometry acts on the vehicle due to the difference between the front wheel vertical force FVF1 and the rear wheel vertical force RVF1. In the example of FIG. 9, since the front wheel vertical force FVF1 acts downward and the rear wheel vertical force RVF1 acts upward, a pitch moment JPM that sinks the front wheel and lifts the rear wheel is obtained. It works.

The pitch moment resulting from this geometry is specifically expressed by a mathematical expression. The vertical forces FVF1 and RVF1 of the front and rear wheels can be approximated as being proportional to the square of the tire lateral force. Therefore, assuming that the steering frequency is ω (corresponding to the basic frequency of the roll angle), the roll angle is proportional to sin ωt, and the tire lateral force is proportional to sin ω (t−τ _{φ *} ), the pitch moment for the geometry is given by equation (1) Can be expressed as In the formula (1), the front term is the front wheel side vertical force FVF1, and the rear term is the rear wheel side vertical force RVF1. In the first pitch moment calculation process, Expression (1) is derived.

G _f is a proportional coefficient of the pitch moment corresponding to the front wheel geometry determined by the roll center geometry of the front wheels. G _r is a proportional coefficient of the pitch moment corresponding to the rear wheel geometry determined by the roll center geometry of the rear wheel. The proportional coefficient of the pitch moment for the geometry is expressed by a function such as roll center geometry, roll stiffness distribution, weight distribution, etc., and is set to a larger value as the height of the roll center is higher. As shown in FIG. 8, tau _.phi.f is delay time of the roll angle RA to the front wheel tire lateral force RF [s], tau _{[phi] r} is a delay time of the roll angle RA with respect to the tire lateral force RF of the rear wheel [s] is there. This delay time is expressed by a function such as roll inertia moment, roll rigidity, roll damping, etc., and τ _φf and τ _φr may be obtained from the simplified formulas of formulas (2) and (3) or by actual measurement. You may ask for it.

_Cφ is the roll damping coefficient [N / (rad / s)]. _Kφ is roll rigidity [Nm / rad]. I _γ is the yaw moment of inertia [kgm ² ]. m is the vehicle weight [kg]. L _r is the distance [m] between the rear wheel and the vehicle center of gravity. L _f is the distance [m] between the front wheel and the vehicle center of gravity. V is the vehicle speed “m / s”.

  The second pitch moment calculation process will be described. Another main factor that generates a pitch at the time of steering is that a pitch moment is generated when the vertical force at the time of turning due to the difference in expansion of the absorber damping force (suspension damping force) differs from front to back. When turning, the damping forces DFL and DFR of the absorber differ between the left and right wheels. In the case of the example shown in FIGS. 10A and 10B (an example in the case of turning left), in the front wheel of FIG. 10A, the absorber of the left wheel extends and the damping force DFL acts downward, and the right wheel The absorber of the right wheel is compressed and the damping force DFR acts upward, and in the rear wheel of (b), the left wheel absorber extends and the damping force DFL acts downward, and the right wheel absorber compresses A damping force DFR is acting upward. Vertical forces FVF2 and RVF2 act on the front wheel side and the rear wheel side due to the difference between the damping force DFL of the left wheel and the damping force DFR of the right wheel. As shown in FIG. 10C, a pitch moment DPM corresponding to the damping force acts on the vehicle due to the difference between the front wheel vertical force FVF2 and the rear wheel vertical force RVF2. In the example of FIG. 10, the front wheel side vertical force FVF2 acts greatly downward, and the rear wheel side vertical force RVF2 acts downwardly, so that the pitch moment is such that the front wheel side sinks and the rear wheel side rises. DPM is working.

  The pitch moment resulting from this damping force expansion difference is specifically expressed by a mathematical expression. The vertical forces FVF2 and RVF2 of the front and rear wheels are proportional to the roll rate. The roll rate is expressed as ω cos ωt by differentiating the roll angle sin ωt. Therefore, the pitch moment corresponding to the damping force can be expressed by Expression (4). In the second pitch moment calculation process, Expression (4) is derived.

M _ab is a proportional coefficient of the pitch moment corresponding to the damping force. The proportional coefficient of the pitch moment for the damping force is expressed by a function such as the front / rear difference of the damping force expansion difference of the absorber, the tread, the roll angle, etc., and the difference in the damping force expansion difference of the left and right wheels of the front and rear wheels is large. Larger values are set.

The pitch angle calculation process will be described. The pitch moment obtained by combining the pitch moment for the geometry and the pitch moment for the damping force is converted into a pitch angle in consideration of dynamic damping force and inertial force. The pitch angle can be expressed by Expression (5) by multiplying the sum of Expression (1) and Expression (4) by the pitch response (gain G _θ , phase τ _θ ). In the pitch angle calculation process, Expression (5) is derived.

G _θ is the magnitude (gain) of the pitch angle with _respect to the pitch moment, and as shown in FIG. 6, is a slope of a straight line indicating the relationship between the pitch moment and the pitch angle. The gain _Gθ can be expressed by a function such as pitch moment of inertia, pitch rigidity, pitch attenuation, and the like. The gain _Gθ may be obtained from the simple expression of Expression (6) or the exact expression of Expression (7), or may be obtained by actual measurement. As shown in FIG. 7, τ _θ is a delay time of the pitch angle PA with respect to the pitch moment PM. This delay time τ _θ can be expressed by a function such as pitch inertia moment, pitch rigidity, pitch attenuation, or the like. The delay time τ _θ may be obtained from a simple expression of Expression (8) or a strict expression of Expression (9), or may be obtained by actual measurement.

_Kθ is the pitch rigidity [Nm / rad]. C _θ is the pitch attenuation coefficient [N / (rad / s)]. I _θ is the pitch moment of inertia [kgm ² ].

  The Fourier transform process will be described. Since the pitch angle represented by the equation (5) includes a nonlinear term such as a square or an absolute value and is difficult to handle, the equation representing the time difference between the roll and the pitch becomes complicated. Therefore, since the fundamental frequency of the pitch at the time of steering is twice the fundamental frequency ω of the roll, Equation (5) is Fourier transformed and the Fourier coefficient of the 2ω component that has the greatest influence on the pitch angle is used in the Fourier expansion. . The quadratic component of the Fourier coefficient is expressed by Expression (10). In the Fourier transform process, the pitch angle represented by Equation (5) is Fourier transformed to derive Equation (10) which is the secondary component (pitch angle) of the Fourier coefficient.

  Expression (10) is a simple expression that does not include the square component or the nonlinear component of the absolute value. By using the pitch angle represented by this formula (10), the time difference between the roll and the pitch can also be represented by a simple formula.

  The time difference calculation process will be described. As shown in equation (11), if the cosine coefficient of equation (10) is A and the sine coefficient of equation (10) is B as shown in equation (12), the pitch angle can be expressed by equation (13). it can. Further, α can be expressed by equation (15) from equation (14) showing the relationship between α and A, B in equation (13). On the other hand, the roll angle can be expressed by Equation (16).

Time t _phi roll angle reaches a peak, because the equation (17) Differentiating roll angle represented by formula (16), become a d.phi = 0 (peak) becomes Equation (18). On the other hand, the time t _theta pitch angle reaches the peak, so by differentiating the pitch angle according to formula (13) becomes Equation (19), become a d [theta] = 0 (peak) becomes equation (20).

Therefore, the time difference t _phi -t _theta peaks between the roll angle and the pitch angle can be expressed by Equation (21). (2n−m) is an arbitrary integer, and is a time difference between adjacent peaks of the roll angle and the pitch angle, and thus can be regarded as Expression (22). From equation (22), equation (21) becomes equation (23). Further, when Expression (15) is substituted for α in Expression (23), Expression (11) is substituted for A, and Expression (12) is substituted for B, the time difference t _φ between the peaks of the roll angle and the pitch angle. −t _θ can be expressed by Expression (24). In the time difference calculation process, Expression (24) is derived.

Expression (24) is a theoretical expression of a mechanism for generating roll and pitch in consideration of the correlation between roll and pitch. In Expression (24), the time difference becomes 0 (that is, the occurrence timing of the roll and the peak is synchronized) when tan ⁻¹ [] becomes π / 2, and the denominator of tan ⁻¹ . Is when becomes zero.

The suspension design process will be described. Designing a suspension of specifications when the time difference t _phi -t _theta of formula (24) becomes zero. For example, the geometric characteristics (G _f , G _r ), roll dynamic characteristics (τ _φf , τ _φr ), and pitch dynamic characteristics (τ _θ ) are fixed, and the time difference t _φ −t _{θ is set} to 0 by the damping force characteristic (M _ab ). The case will be described. When Equation (24) is solved for M _{ab under} the condition of zero time difference, Equation (25) is obtained. The proportional coefficient M _ab of the damping moment component pitch moment can be approximated to the relationship shown in the equation (26) with the actual damping force characteristic (the difference between before and after the damping force expansion difference between the left and right wheels of the absorber). Therefore, the damping force characteristic in which the time difference between the roll angle and the pitch angle is 0 is expressed by equation (27), and this equation (27) is a condition (design index) for synchronizing the roll and pitch. In the suspension design process, this equation (27) is derived, and the known G _f , G _r , τ _φf , τ _φr , τ _{θ and the} like are substituted into the equation (27), and the damping force characteristic (before and after the damping force _expansion difference) Find the difference. And the damping force of an absorber is set from the difference before and after this damping force expansion difference.

T is a tread. L is a wheelbase. RR is a roll rate. RG is a lateral acceleration acting on the vehicle. For example, when the longitudinal difference of the damping force expansion difference is large, M _ab is increased, and the damping force of the absorber is designed so that the longitudinal expansion difference is large.

The suspension design can be set other than the damping force characteristic, and an example is shown below. Roll dynamics, pitch dynamics, the damping force characteristic is fixed and when the time difference t _phi -t _theta geometry characteristic and 0 is solved for G _f and G _r Equation (24) under the conditions of the time difference 0, Set the height of the roll center. When the geometric characteristic, pitch dynamic characteristic and damping force characteristic are fixed and the time difference t _φ −t _{θ is set} to 0 in the roll dynamic characteristic, Equation (24) is solved for τ _φf and τ _{φr under} the condition of zero time difference, Set the stiffness of the suspension spring and stabilizer. Geometry characteristics, roll dynamics, the damping force characteristic is fixed and when the zero time difference t _phi -t _theta at a pitch dynamics is solved for tau _theta equation (24) under the conditions of the time difference 0, the suspension spring And set the rigidity of the stabilizer.

  Finally, the flow of the suspension design according to the present embodiment will be described along the flowchart of FIG. FIG. 11 is a flowchart showing a design flow of the suspension according to the present embodiment.

First, the pitch moment at the time of turning caused by the roll center geometry is calculated using the proportional coefficient G _f , G _{r of} the geometrical pitch moment and the roll angle delay times τ _φf , τ _φr with respect to the tire lateral force. ) Is derived (S1). Further, the pitch moment during turning caused by the suspension damping force expansion difference is calculated using the proportional coefficient M _ab of the damping force component pitch moment, and the formula (4) is derived (S2). Then, the pitch angle is calculated using the two pitch moments, the pitch angle gain Gθ with _{respect to the} pitch moment, and the pitch angle delay time τθ with _respect to the pitch moment, and Equation (5) is derived (S3).

  The pitch angle represented by the equation (5) is Fourier transformed, the 2ω component of the Fourier coefficient is extracted, and the equation (10) is derived (S4). The time difference between the pitch angle and the roll angle is calculated using the pitch angle composed of the 2ω component of the Fourier coefficient, and the formula (24) is derived (S5).

  Suspension characteristics (damping force characteristics, geometry characteristics, roll dynamic characteristics, pitch dynamic characteristics, etc.) when the time difference between the pitch angle and roll angle in equation (24) is 0 are designed (S6).

  According to this suspension design, by deriving the theoretical formula of the generation mechanism considering the correlation between roll and pitch during steering, the conditions (design index) for synchronizing the generation timing of roll and pitch are clarified Can be. By designing the suspension based on this condition, the roll feeling can be improved and the steering stability can be improved.

  As mentioned above, although embodiment which concerns on this invention was described, this invention is implemented in various forms, without being limited to the said embodiment.

  For example, although the present embodiment is applied to a vehicle having a normal suspension, it may be applied to a vehicle having an active suspension.

  Further, in the present embodiment, the tire lateral force is obtained based on the roll angle delay time with respect to the tire lateral force, but may be obtained by other methods.

  In the present embodiment, the coefficient of the quadratic component of the Fourier expansion of the pitch angle represented by the equation (5) is handled as the pitch angle. However, the pitch angle may be obtained using a coefficient other than the secondary component. Alternatively, the pitch angle represented by Expression (5) may be used as it is without being subjected to Fourier transform.

  Further, in the present embodiment, the damping force characteristic of the suspension is the difference between before and after the damping force expansion difference, but the damping force characteristic of the suspension may be expressed by other elements.

It is a figure which shows the Lissajous waveform of the roll angle and pitch angle of a vehicle with high sensory evaluation of a roll feeling, (a) is an example of a vehicle with high evaluation, (b) is another example of a vehicle with high evaluation. . It is a figure which shows the Lissajous waveform of the roll angle and pitch angle of a vehicle with low sensory evaluation of a roll feeling, (a) is an example of a vehicle with low evaluation, (b) is another example of a vehicle with low evaluation. . It is a figure which shows the time change of the roll angle of a vehicle with high sensory evaluation of a roll feeling, and the time change of a pitch angle. It is a figure which shows the time change of the roll angle of a vehicle with low sensory evaluation of a roll feeling, and the time change of a pitch angle. It is explanatory drawing of a roll center, an instantaneous center, a tire lateral force, and a vertical force. It is a figure which shows the relationship between a pitch moment and a pitch angle. It is a figure which shows the relationship between the time change of a pitch angle, and the time change of a pitch moment. It is a figure which shows the relationship between the time change of a roll angle, and the time change of a tire lateral force. It is explanatory drawing of the pitch moment resulting from the geometry of a suspension. (A) shows tire lateral force and vertical force on the front wheel side, (b) shows tire lateral force and vertical force on the rear wheel side, and (c) shows front and rear vertical force and pitch moment. It is explanatory drawing of the pitch moment resulting from the damping force of a suspension. (A) shows the front wheel side damping force and vertical force, (b) shows the rear wheel side damping force and vertical force, and (c) shows the front and rear vertical force and pitch moment. It is a flowchart which shows the flow of the design of the suspension which concerns on this Embodiment.

Explanation of symbols

  UA ... Upper arm, LA ... Lower arm, MCL, MCR ... Instantaneous center, RC ... Roll center, RFL, RFR ... Tire lateral force, VFL, VFR ... Vertical force, FVF1, RVF1 ... Vertical force by geometry, JPM ... Geometry Pitch moment, DFL, DFR ... absorber damping force, FVF2, RVF2 ... vertical force due to damping force expansion difference, DPM ... pitch moment for damping force

Claims (7)

The vertical moment and rear force generated on the front wheel side by the product of the geometric proportionality factor determined from the front wheel side geometry and the square of the tire lateral force on the front wheel side set based on the basic vibration of the roll angle First calculated as the sum of the vertical force generated on the rear wheel side by the product of the geometric proportion coefficient determined from the wheel side geometry and the square of the tire lateral force on the rear wheel side set based on the basic vibration of the roll angle Process,
A second step of calculating a pitch moment due to the damping force of the suspension as a product of a damping force proportional coefficient determined by a difference in damping force characteristics of the suspensions of the front and rear wheels and a roll rate;
The pitch angle is the sum of the pitch moment due to the suspension geometry calculated in the first step and the pitch moment due to the suspension damping force calculated in the second step, the gain of the pitch angle with respect to the pitch moment, and the phase delay of the pitch angle. A third step of calculating as a product of
And a fourth step of calculating a phase difference between the pitch angle and the roll angle from the pitch angle calculated in the third step.   The suspension characteristic calculation method according to claim 1, wherein the tire lateral force is calculated based on a delay time of a roll angle with respect to the tire lateral force.   The suspension characteristic calculation method according to claim 1 or 2, wherein the geometric proportionality coefficient is set to a larger value as the height of the roll center is higher.   The suspension characteristic calculation method according to any one of claims 1 to 3, wherein the damping force proportional coefficient is set to a larger value as a difference in damping force characteristics between the suspensions of the front and rear wheels is larger. .   5. The phase difference between the pitch angle and the roll angle is obtained from a coefficient of a secondary component of a Fourier expansion of the pitch angle calculated in the third step. 6. Suspension characteristics calculation method described in 1.   The suspension characteristic calculation method according to any one of claims 1 to 5, wherein the damping force characteristic of the suspension of the front and rear wheels is a difference between a pressure difference between the front wheels and a pressure difference between the rear wheels. .   The suspension characteristic calculation method according to any one of claims 1 to 6, wherein the basic vibration of the roll angle is a vibration of a roll angle in a roll motion of a vehicle caused by a driver's steering input. .

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