VEHICLE HEIGHT CONTROL DEVICE

Abstract

Vehicle height control device (10) applied to a vehicle (20) equipped with: a wheel (12) rotatably mounted about an axis of rotation (24) by a wheel carrier (22) and having a tire; a drive system (14) which drives the wheel by means of a drive source (28) via a transmission (30) by rotating it; and a suspension arm (16) arranged between the wheel carrier (22) and a vehicle body (34), characterized in that the suspension arm (16) is arranged such that the axis of rotation (24), when viewed in the lateral direction of the vehicle, traces a locus (36) which is inclined backwards when the wheel (12) moves up and down;The vehicle height control device (10) comprises a vehicle height adjustment device (42) configured to change a vehicle height and an electronic control unit (44) controlling the vehicle height adjustment device, wherein the electronic control unit is configured to receive information about an index (Rt or St) indicating an equivalent moment of inertia (IP) of the drive system (14) and to control the vehicle height adjustment device such that the smaller the equivalent moment of inertia indicated by the index, the lower the vehicle height (H).

Description

Background of the inventionTechnical field

[0001] The present invention relates to a vehicle height control device for a vehicle such as an automobile. State of the art

[0002] A suspension is known that improves the ride comfort of a vehicle by reducing the longitudinal force acting on a wheel due to vertical impact from a road surface. For example, Japanese Patent Application Publication No. JP 2009-40349 A describes a suspension in which a suspension arm is arranged so that a rotational axis of a wheel traces a backward-inclined locus as the wheel moves up and down when viewed in a lateral direction of a vehicle, and a shock absorber is arranged so that it is inclined forward.

[0003] According to this type of suspension, a longitudinal force acting on the wheel due to vertical action from a road surface can be at least partially balanced by a longitudinal force generated by the backward inclination of the locus of the rotation axis and a longitudinal force generated by a damping force of the shock absorber, which makes it possible to reduce a longitudinal force of the wheel.

[0004] In a vehicle with a drive system in which a wheel is rotationally driven by a power source via a transmission, as a torsional resonance frequency of the drive system approaches a vertical resonance frequency of a suspension, longitudinal vibrations due to a longitudinal force of the wheel become significant. As explained in more detail later, the torsional resonance frequency of the drive system is determined by a moment of inertia and the torsional rigidity of the drive system, and the moment of inertia of the drive system varies when a gear ratio of the transmission changes. Therefore, the longitudinal force acting on the wheel due to vertical action from the road surface changes with changes in the moment of inertia of the drive system, and therefore changes with changes in the gear ratio of the transmission.

[0005] The suspension described in the above publication cannot handle the fluctuation of the longitudinal force acting on a wheel due to the fluctuation of the moment of inertia of a drive system. Therefore, it is not possible to effectively reduce the longitudinal force acting on the wheel due to vertical impact from the road surface, independent of fluctuations in the moment of inertia of the drive system due to changes in the gear ratio of a transmission. Summary of the invention

[0006] The present invention provides an improved vehicle height control device capable of effectively reducing a longitudinal force acting on a wheel due to vertical impact from a road surface even when an equivalent moment of inertia of a drive system changes due to changes in a gear ratio of a transmission.

[0007] According to the present invention, there is provided a vehicle height control device applied to a vehicle equipped with: a wheel rotatably supported by a wheel carrier about a rotation axis and having a tire; a drive system that rotatably drives the wheel by a drive source via a transmission; and a suspension arm disposed between the wheel carrier and a vehicle body.

[0008] The suspension arm is arranged so that the rotation axis, when viewed in the lateral direction of the vehicle, draws a locus that is inclined backward / rearward as the wheel moves up and down; the vehicle height control device includes a vehicle height adjusting device configured to change a vehicle height, and an electronic control unit that controls the vehicle height adjusting device, wherein the electronic control unit is configured to acquire information about an index indicating an equivalent moment of inertia of the drive system and to control the vehicle height adjusting device such that the smaller the equivalent moment of inertia indicated by the index, the lower the vehicle height.

[0009] According to the above configuration, since the wheel's rotational axis traces a locus inclined backward / rearward as the wheel moves up and down, as will be explained in more detail later, a longitudinal force acting on the wheel due to vertical impact from a road surface is at least partially offset by a longitudinal force generated by the backward inclination of the locus. The longitudinal force acting on the wheel due to vertical impact from the road surface fluctuates as the equivalent moment of inertia of the drive system changes, but the vehicle height adjustment device is controlled so that the smaller the equivalent moment of inertia, the lower the vehicle height.

[0010] Therefore, as will be explained in more detail later, the longitudinal force generated by the backward inclination of the locus can be varied in accordance with the change in the longitudinal force acting on the wheel due to the change in the equivalent moment of inertia of the drive system. Accordingly, even if the equivalent moment of inertia of the drive system changes, the longitudinal force acting on the wheel can be effectively reduced.

[0011] In one aspect of the present invention, an angle of the backward inclination of the locus is set so that a first longitudinal force acting on the wheel due to vertical action from a road surface is at least partially balanced by a second longitudinal force generated by the backward inclination of the locus, and the electronic control device is configured to control the vehicle height adjusting device so that a change in the angle of the backward inclination (or in the backward inclination angle) of the locus required to balance a change in the first longitudinal force due to a change in the equivalent moment of inertia by a change in the second longitudinal force is achieved by a change in the vehicle height.

[0012] In another aspect of the present invention, the electronic control device stores a relationship between a target vehicle height and the index for achieving, by controlling the vehicle height, a change in the angle of backward inclination (or in the backward inclination angle) of the locus required to compensate for a change in the first longitudinal force due to a change in the equivalent moment of inertia by a change in the second longitudinal force.

[0013] In another aspect of the present invention, the index is a gear ratio of the transmission, and the relationship is a relationship between a target vehicle height and a gear ratio of the transmission, which is set such that the smaller the gear ratio of the transmission, the lower the target vehicle height.

[0014] In another aspect of the present invention, the transmission is a multi-stage transmission, the index is a gear stage of the transmission, and the relationship is a relationship between a target vehicle height and a gear stage of the transmission, which is set such that the higher the gear stage of the transmission, the lower the target vehicle height.

[0015] Other objects, other features and attendant advantages of the present invention will be readily understood from the description of the embodiments of the present invention described with reference to the following drawings. Short description of the characters Fig. 1 is a schematic configuration diagram showing an embodiment of a vehicle height control device according to the present invention. Fig. Figure 2 is an explanatory diagram showing a wheel driven by a drive system. Fig. Figure 3A is a diagram showing an example of a relationship between a vertical displacement Z of a wheel and a longitudinal force F X1 shows. Fig. Figure 3B is a diagram showing an example of a relationship between a vertical displacement Z of the wheel and a longitudinal force F X2 shows. Fig. 3C is a diagram showing an example of a relationship between a difference value of the vertical displacement Z of the wheel and a longitudinal force F X3 shows. Fig. 4 is a diagram showing a longitudinal force F XT acting on a wheel due to an inclination of a road surface. Fig. 5 is a diagram explaining a longitudinal force F XS acting on a wheel due to wheel slip. Fig. Figure 6 is a graph showing a relationship between the gain of h'(s) (upper part) and frequency and a relationship between the phase of h'(s) and frequency (lower part). Fig. Figure 7 is a diagram showing a relationship between gain and frequency of a transfer function from a deflection Z-Z0 of a tire to a longitudinal force F X1 (upper part) and a relationship between phase and frequency of a transfer function from the deflection Z-Z0 of the tire to the longitudinal force F X1 (lower part) shows. Fig. 8 is a graph showing a relationship between gain and frequency of a transfer function from the deflection Z-Z0 of the tire to a vertical displacement Z of a wheel (upper part) and a relationship between phase and frequency of the transfer function from the deflection Z-Z0 of the tire to the vertical displacement Z of the wheel (lower part). Fig. Figure 9 is a diagram showing a relationship between frequency and gain of a transfer function from the vertical displacement Z of the wheel to the longitudinal force F X1 (upper part) and a relationship between frequency and phase of the transfer function from the vertical displacement Z of the wheel to the longitudinal force F X1 (lower part) shows. Fig. Figure 10 is a vector diagram showing FX 1 / Z of a vertical resonance frequency of the wheel divided into a real part and an imaginary part. Fig. 11 is a diagram showing a relationship between the real part of the transfer function from the vertical displacement Z of the wheel to the longitudinal force F X1 and a moment of inertia I P of a drive system. Fig. 12 is a diagram showing a relationship between a target angle γt of the backward inclination of a locus of a wheel rotation axis and an equivalent moment of inertia I Pof the drive system (left part) and a relationship between the target reverse inclination angle γt of the locus and a target deviation ΔHt of a vehicle height (right part). Fig. 13A is a diagram showing a relationship between gear ratio Rt and target vehicle height Ht. Fig. 13B is a diagram showing a relationship between the gear stage St and the target vehicle height Ht. Fig. 14 is a flowchart corresponding to a vehicle height control program of the embodiment. Detailed description of the embodiment

[0016] The present invention will now be described in detail with respect to an embodiment with reference to the accompanying drawings. [Embodiment]

[0017] As in the Fig. 1 and Fig. As shown in Fig. 2, the vehicle height control device 10 according to the embodiment of the present invention is applied to a vehicle 20 including a wheel 12, a drive system 14, a suspension arm 16, and a shock absorber 18. The vehicle 20 may be a vehicle capable of automatic travel. The wheel 12 is rotatably supported about a rotational axis 24 by a wheel carrier 22 and has an elastically deformable tire 26, as is well known. The drive system 14 is configured to rotatably drive the wheel 12 via a transmission 30 and a drive shaft 32, with a motor 28 serving as a drive source. The suspension arm 16 and the shock absorber 18 are disposed between the wheel carrier 22 and a vehicle body 34.

[0018] Although in Fig. 1, the suspension arm may include a plurality of arms, links, etc., and the suspension arm 16 is illustrated as one suspension arm corresponding to a plurality of arms, links, etc. when viewed from the side of the vehicle 20. The power source may be any power source known in the art, except for an engine. In the embodiment, the transmission 30 is a continuously variable transmission, but it may also be a multi-speed transmission, such as a gear transmission.

[0019] The suspension arm 16 is connected to the wheel carrier 22 and the vehicle body 34 such that the rotation axis 24 draws a locus 36 inclined backward at an angle γ with respect to the vertical direction when the wheel 12 moves up and down as viewed in the lateral direction of the vehicle 20. The end of the suspension arm 16 on the vehicle body 34 side is located higher than the end on the wheel carrier 22 side. In a situation where the wheel 12 is in a neutral position of vertical displacement, an inclination angle of the suspension arm 16, that is, an angle that a straight line connecting the two ends makes with the horizontal direction, is β.It should be noted that the locus 36 does not have to be a straight line, and the angle γ of the backward inclination of the locus 36 can be considered to be the same as the inclination angle β within a range of the vertical displacement of the wheel 12 when the vehicle 20 is moving.

[0020] The shock absorber 18 is disposed between the wheel carrier 22 and the vehicle body 34 in a forward / forward tilted state, and a forward tilt angle, that is, an angle formed by a main axis (not shown) of the shock absorber with the vertical direction, is α. The shock absorber 18 has an upper end connected to the vehicle body 34 via an upper bracket 38 and a lower end connected to the wheel carrier 22. The upper bracket 38 functions as a spring 38A and a damper 38B.

[0021] The backward inclination angle γ of the locus 36 and the forward inclination angle α of the shock absorber are set so that a longitudinal force F X1 acting on the wheel 12 at a ground contact point P due to a vertical action from a road surface 40, at least partly by a longitudinal force F X2 generated by the backward inclination of the locus 36 and a longitudinal force F X3 generated by a damping force of the shock absorber.

[0022] For example, Fig. 3A an example of a relationship between the vertical displacement Z of the wheel 12 as unsprung and the longitudinal force F X1 . The longitudinal force F X1 takes a negative value if the vertical displacement Z is positive (upward displacement). Fig. Figure 3B shows an example of a relationship between the vertical displacement Z of the wheel 12 and the longitudinal force F X2 . The longitudinal force F X2takes a positive value when the vertical displacement Z is positive and is proportional to the vertical displacement Z. Fig. Figure 3C shows an example of a relationship between the vertical displacement Z of the wheel 12 and the longitudinal force F X3 . The longitudinal force F X3 takes a positive value when a difference value of the vertical displacement Z, ie, an upward displacement speed of the wheel 12, is positive, and is substantially proportional to the displacement speed.

[0023] A sum of the longitudinal forces F X2 and F X3 is the value indicated by the dashed line in Fig. 3A. Therefore, the longitudinal force F X1 at least partly by the sum of the longitudinal forces F X2 and F X3 It should be noted that in the Fig. 3A and Fig. 3C Arrows indicate the directions of changes in the longitudinal forces F X1 and F X2due to the vertical displacement of wheel 12.

[0024] A suspension spring 42 is also arranged between the wheel carrier 22 and the vehicle body 34. Specifically, in the embodiment, the suspension spring 42 is an air spring with a vehicle height adjustment function, and functions as a vehicle height adjustment device configured to change the vehicle height. Therefore, in this specification, the suspension spring 42 is referred to as the vehicle height adjustment device 42. Note that the suspension spring may be, for example, a spring such as a coil spring, and the vehicle height adjustment device may be any vehicle height adjustment device known in the art independent of the suspension spring.

[0025] The vehicle height control device 10 includes an electronic control device 44 that controls the vehicle height adjustment device 42. The electronic control device 44 includes a vehicle height sensor 46, a drive system control unit 48, and a vehicle height control unit 50. Each (electronic) control unit is an electronic control unit that has a microcomputer as its main component. The vehicle height sensor 46 detects a vehicle height H as the vertical distance between a reference position (not shown) of the vehicle body 34 and the rotation axis 24.

[0026] The microcomputer of each (electronic) control unit includes a CPU, a ROM, a RAM, a readable / writable non-volatile memory (N / M), an interface (I / F), and the like. The CPU performs various functions by executing instructions (programs, routines) stored in the ROM.

[0027] Furthermore, these control units and sensors such as the vehicle height sensor 46 are communicatively connected to one another via a CAN (Controller Area Network) 52.

[0028] The drive system control unit 48 controls an output torque T of the drive system 14 and thus a drive torque applied to a wheel 12 by controlling an output of the engine 28 and a gear ratio Rt of the transmission 30. The drive system control unit 48 outputs a signal indicating the gear ratio Rt of the transmission 30 to the vehicle height control unit 50 via the CAN 52. The gear ratio Rt is an index that represents an equivalent moment of inertia I P of the drive system 14, and the equivalent moment of inertia I Pis a product of a sum of equivalent moments of inertia of each individual component of the transmission 30 and a square of the gear ratio Rt. It is therefore proportional to the square of the gear ratio Rt.

[0029] As will be described in more detail later, the longitudinal force F acting on the wheel 12 at the ground contact point P X1 due to vertical action from the road surface 40 depending on changes in the equivalent moment of inertia I P of the drive system 14. Therefore, the vehicle height control unit 50 acquires information about the gear ratio Rt as an index representing the equivalent moment of inertia I Pof the drive system 14, and controls the vehicle height adjustment device 42 so that the smaller the equivalent moment of inertia indicated by the index, the lower the vehicle height H. In particular, the vehicle height control unit 50 controls the vehicle height adjustment device 42 so that a change in the vehicle height H achieves a change in the angle γ of the backward inclination of the locus 36, which is necessary to compensate for the change in the longitudinal force F X1 due to the change in the equivalent moment of inertia I caused by the backward inclination of the locus P the longitudinal force F X2 to balance. (Principle of vehicle height control of the present invention adopted in embodiment)

[0030] In order to facilitate understanding of the present invention and the embodiment, the principle of vehicle height control in the present invention will be explained.

[0031] It is assumed that the longitudinal force F acting on the wheel 12 at the grounding point P X1 due to the vertical action of the road surface 40 a sum of a longitudinal force F XT ( Fig. 4), which acts on the wheel 12 due to an inclination of the road surface 40, and a longitudinal force F XS ( Fig. 5), which acts on the wheel 12 due to the slip of the wheel.

[0032] As in Fig. As shown in Figure 4, an inclination angle of the road surface 40 is represented by θx, and a ground load of the wheel 12 is represented by W (not shown). A steady component of a longitudinal velocity of the wheel 12 is represented by U, a fluctuating component of the longitudinal velocity of the wheel 12 is represented by ΔU, and a vertical displacement of the road surface 40 is represented by Z0. The longitudinal force F XT is expressed by the following equation (1). FXT=−Wtanθx =−WZ˙0U + ΔU

[0033] As in the Fig. 2 and Fig. 5, a driving stiffness is represented by Px and a slip rate of the wheel 12 by Sx (not shown). A radius (constant component) of the tire 26 is represented by r0, and a fluctuating component of a rolling radius of the tire 26 is represented by ηΔr. Note that η is a ratio between the amount of change in the rolling radius and the amount of vertical deformation of the tire. A steady component and a fluctuating component of the rotational angular velocity of the wheel 12 are represented by ω0 and Δω, respectively. A longitudinal force acting on the wheel at the grounding point P due to a driving torque applied to the wheel 12 is represented by F XW shown, a longitudinal spring constant of the tire 26 by K X and a Laplace operator is represented by s. The longitudinal force F XSis expressed by the following equation (2). FXS=PXSX =PX{(r0+μΔr)(ω0+Δω)−FXws / KXU + ΔU−1}

[0034] If the rotational angular speeds of the drive system 14 and the wheel 12 are represented by ω P or ω T (=ω0 +Δω) and the torsional stiffness of the drive shaft 32 by K P the following equation (3) is considered the equation of motion in the direction of rotation of the drive system 14. IpωpS=−Kp(ωPS−ωTS)

[0035] If one sets an equivalent moment of inertia of the wheel 12 by I T , the following equation (4) is considered the equation of motion in the direction of rotation of the wheel. ITwTS=−FXwr0+KP(ωpS−ωTS)

[0036] If the longitudinal force F XW determined from the above equations (3) and (4) and inserted into the above equation (2), the longitudinal force F acting on the wheel 12 is X1expressed by the following equation (5). FX1=FXT+FXS =h'(s){−WUZ˙0+PXω0ηU(Z−Z0)−PXUX˙}

[0037] In equation (5), h'(s) is a term of the dynamic characteristic, and the terms in curly brackets are terms of the continuous characteristic. The influence of the first and third terms of the continuous characteristic on the longitudinal force F X1 is smaller than that of the second term. Therefore, h'(s) is expressed by the following equation (6) when the first and third terms are omitted. h'(s)≅UKXsPX(s2IT+IPITIPKP)(s2+ωE2)(s2+2ζWωWs+ωW2)

[0038] In particular, in equation (6) ω E a resonance frequency of the rotation of the drive system 14, expressed by the following equation (7), and ω W is a resonance frequency of the rotation of the wheel 12, expressed by the following equation (8). ω Dis a torsional resonance frequency, ie anti-resonance frequency, of the drive shaft 32, expressed by the following equation (9), and ζ W is a damping ratio in the rotation direction of the wheel 12, expressed by the following equation (10). ωE=KPIP ωW=KXr02IT ωD=KP(IP+IT)IPIT ζw=U3PXr0ITKX

[0039] The upper part of Fig. 6 shows an example of a gain-frequency relationship of h'(s), and the lower part of Fig. Figure 6 shows an example of a relationship between phase and frequency of h'(s). In Fig. 6, a solid line, a dashed line and a dashed-dotted line indicate values ​​at which the equivalent moment of inertia I P of the drive system 14 is 0, 0.43 and 0.60 respectively.

[0040] Out of Fig. 6 it can be seen that with increasing equivalent moment of inertia I Pthe gain of h'(s) increases and the phase of h'(s) lags in the frequency range from 10 to 20 Hz. It can also be seen that the gain of h'(s) at the antiresonance frequency ω D becomes minimal.

[0041] The upper part of Fig. Figure 7 shows an example of a relationship between gain and frequency of a transfer function from a deflection Z-Z0 of the tire 26 to the longitudinal force F X1 , and the lower part of Fig. Figure 7 shows an example of a relationship between phase and frequency of a transfer function from the deflection Z-Z0 to the longitudinal force F X1 . In Fig. 7, the solid line, the dashed line and the dashed-dotted line indicate values ​​when the equivalent moment of inertia I P of the drive system 14 is 0.4, 0.8 and 1.6 respectively.

[0042] Out of Fig. 7 it can be seen that with increasing equivalent moment of inertia I Pin the frequency range from 10 to 20 Hz the gain of the transfer function from the deflection Z-Z0 to the longitudinal force F X1 and the delay of the phase of the transfer function from the deflection Z-Z0 to the longitudinal force F X1 increases.

[0043] The upper part of Fig. Figure 8 shows an example of a relationship between gain and frequency of a transfer function from the deflection Z-Z0 of the tire 26 to a vertical displacement Z of the wheel 12, and the lower part of Fig. Figure 8 shows an example of a relationship between phase and frequency of the transfer function from the deflection Z-Z0 to the vertical displacement Z of the wheel 12. Fig. 8 it can be seen that the gain and phase of the transfer function from the deflection Z-Z0 to the vertical displacement Z of the wheel 12 decreases with increasing frequency.

[0044] Since an object to be controlled has the transfer function from the vertical displacement Z of the wheel 12 to the longitudinal force F X1 is the relationship between frequency and the gain and phase of the transfer function from the vertical displacement Z to the longitudinal force F X1 determined according to the following equation (11) based on the values ​​in Fig. 7 and Fig. 8. FX1Z=FX1Z−Z0 / ZZ−Z0

[0045] The upper part of Fig. Figure 9 shows an example of a relationship between frequency and the gain of the transfer function from the vertical displacement Z to the longitudinal force F X1 , and the lower part of Fig. Figure 9 shows an example of the relationship between frequency and phase of the transfer function from the vertical displacement Z to the longitudinal force F X1 . In Fig. 9, the solid line, the dashed line and the dashed-dotted line indicate values ​​when the equivalent moment of inertia I P of the drive system 14 is 0.4, 0.8 and 1.6 respectively.

[0046] If F X1 / Z at a vertical resonance frequency (15 Hz) of the wheel 12 as an unsprung vector based on Fig. 9 is expressed by dividing a real part, ie a component proportional to the vertical displacement Z, and an imaginary part, ie a component proportional to a first-order difference value of the vertical displacement Z (vertical velocity), one obtains Fig. 10. In Fig. 10, the solid arrow, the dashed arrow and the dashed-dotted arrow indicate vectors when the equivalent moment of inertia I P of the drive system 14 is 0.4, 0.8 and 1.6 respectively.

[0047] Fig. 11 shows, based on Fig. 10, an example of a relationship between the real part of the transfer function from the vertical displacement Z to the longitudinal force F X1 and the equivalent moment of inertia I P of the drive system 14. As Fig. 11, the real part of the transfer function increases from the vertical displacement Z to the longitudinal force F X1 with increasing equivalent moment of inertia I P of the drive system 14.

[0048] The “longitudinal force F generated by the backward inclination of the locus 36 X2 “, which is required to calculate the real part of the transfer function from the vertical displacement Z to the longitudinal force F X1 to cancel (a component of the longitudinal force F X1 proportional to the vertical displacement Z), βZK SK . Since “the longitudinal force F generated by the backward inclination of the locus 36 X2 “ per unit vertical displacement Z βK SKthe following equation (12) applies. In particular, K SK a modulus of elasticity of the suspension arm 16 in the direction along a phantom straight line connecting both ends of the suspension arm (for example, 1,000,000 N / m). βKSK = Reality of the transfer function from vertical displacement Z to longitudinal force FX1…

[0049] Therefore, an angle of backward inclination of the locus 36, which is required to convert the real part of the transfer function from the vertical displacement Z to the longitudinal force F X1 to cancel, ie, a target angle γt of backward inclination, expressed by the following equation (13) based on the above equation (12). γt=β= (Reality of the transfer function from vertical displacement Z to longitudinal force FX1) / KSK…

[0050] The left half of Fig. 12 shows an example of a relationship between the desired angle γt of the backward inclination of the locus 36 and the equivalent moment of inertia I P of the drive system 14 according to Fig. 11. As can be seen from the figure, the desired angle γt of the backward inclination of the locus 36 increases with the equivalent moment of inertia I P of the drive system 14. The right half of Fig. Figure 12 shows a relationship between the target angle γt of the backward inclination of the locus 36 and a target deviation ΔHt of the vehicle height. Specifically, the target deviation ΔHt of the vehicle height is a target value of a difference between a target vehicle height Ht and a preset standard vehicle height (ΔHt=0). As shown in Fig. 12, the smaller the equivalent moment of inertia I Pof the drive system 14, the smaller the target angle γt of the backward inclination of the locus 36, and the smaller the target deviation ΔHt of the vehicle height, the smaller the target angle γt of the backward inclination of the locus 36. Therefore, the smaller the target backward inclination angle γt of the locus 36, the smaller the target vehicle height Ht becomes, and accordingly, the smaller the equivalent moment of inertia I P of the drive system 14. In Fig. 12, the dashed-dotted line arrows show how to calculate from the equivalent moment of inertia I P the target deviation ΔHt of the vehicle height H, and thus the target vehicle height Ht, is obtained.

[0051] Fig. 13A shows an example of a relationship between a gear ratio Rt of the transmission 30 and the target vehicle height Ht based on Fig. 12 and the relationship between the equivalent moment of inertia I Pof the drive system 14 and the gear ratio Rt (I P is proportional to the square of Rt). As in Fig. As shown in Figure 13A, the target vehicle height Ht is lower as the gear ratio Rt is smaller.

[0052] In the embodiment, the ROM of the vehicle height control unit 50 stores a vehicle height control program and a map corresponding to Fig. 13A, ie a map of the relationship between the gear ratio Rt and the target vehicle height Ht. The program corresponds to the one in Fig. 14, and the vehicle height control is executed according to this flowchart. <Fahrzeughöhen-Steuerprogramm in Ausführungsform>

[0053] Hereinafter, the vehicle height control in the embodiment will be described with reference to the Fig. The flowchart shown in Figure 14 is described. The vehicle height control according to the Fig. The flowchart shown in Fig. 14 is repeatedly executed by the CPU of the vehicle height control unit 50 at predetermined intervals while an ignition switch (not shown) is turned on.

[0054] First, in step S10, the CPU reads a signal indicating a gear ratio Rt of the transmission 30 from the drive system control unit 48. As described above, the gear ratio Rt is the index indicating an equivalent moment of inertia I P of the drive system 14.

[0055] In step S20, the CPU determines a target vehicle height Ht with reference to the map according to Fig. 13A based on the gear ratio Rt.

[0056] In step S30, the CPU controls the vehicle height adjusting device 42 so that a vehicle height H detected by the vehicle height sensor 46 becomes the target vehicle height Ht.

[0057] As can be seen from the above description, the rotation axis 24 of the wheel 12 according to the embodiment draws a backward / rearward inclined locus 36 when the wheel moves up and down, so that a longitudinal force F acting on the wheel due to a vertical action from the road surface 40 X1 at least partly by a longitudinal force F generated by the backward inclination of the locus X2 The longitudinal force F X1 acting on the wheel due to vertical action from the road surface varies with changes in the equivalent moment of inertia I P of the drive system 14, but the vehicle height adjustment device 42 is controlled so that the smaller the equivalent moment of inertia, the lower the vehicle height.

[0058] Therefore, the longitudinal force F generated by the backward inclination of the locus X2 according to the change in the longitudinal force F acting on the wheelX1 due to the change in the equivalent moment of inertia I P of the drive system 14. Accordingly, even if the equivalent moment of inertia of the drive system changes, a longitudinal force F acting on the wheel X1 + F X2 can be effectively reduced, thereby effectively reducing the longitudinal force transfer from the wheel to the vehicle body.

[0059] In particular, according to the embodiment, the angle γ of the backward inclination of the locus 36 and the angle α of the forward inclination of the shock absorber 18 are set so that the first longitudinal force F acting on the wheel X1 due to the action of the road surface at least partly by the second longitudinal force F X2 generated by the backward tilt and the third longitudinal force F X3generated by a damping force of the shock absorber. The vehicle height adjustment device 42 is controlled so that a change in the angle of backward inclination (or in the backward inclination angle) γ of the locus required to compensate for a change in the first longitudinal force F X1 due to the change in the equivalent moment of inertia I P of the drive system 14 by a change in the second longitudinal force F X2 compensated by a change in the vehicle height H.

[0060] Therefore, the vehicle height H can be controlled so that the backward inclination angle γ of the locus 36 is changed by changing the vehicle height by an angle required to compensate for a change in the first longitudinal force F X1 due to the change in the equivalent moment of inertia I P of the drive system 14 by a change in the second longitudinal force F X2Accordingly, the second longitudinal force can be changed by changing the angle of the backward inclination (or the backward inclination angle) of the locus by changing the vehicle height so that even if the equivalent moment of inertia I P of the drive system changes by a change in the gear ratio Rt of the transmission 30, the change in the first longitudinal force is compensated by the change in the equivalent moment of inertia by the change in the second longitudinal force.

[0061] Furthermore, according to the embodiment, the relationship ( Fig. 13A or Fig. 13B) between the desired vehicle height Ht and the index (gear ratio Rt or gear step St) to achieve a change in the angle γ of the backward inclination of the locus 36 is required to compensate for the change in the first longitudinal force F X1 due to the change in the equivalent moment of inertia I Pby the change in the second longitudinal force F X2 Furthermore, a target vehicle height is determined from the above relationship based on the index, and the vehicle height adjusting device 42 is controlled so that the vehicle height becomes the target vehicle height.

[0062] Therefore, by controlling the vehicle height adjusting device 42 so that the vehicle height becomes the target vehicle height, the second longitudinal force can be changed so that even if the equivalent moment of inertia I P of the drive system 14 changes, the change in the first longitudinal force due to the change in the equivalent moment of inertia is / is compensated by the change in the second longitudinal force.

[0063] As described above, the equivalent moment of inertia I Pof the drive system 14 is proportional to the square of the gear ratio Rt of the transmission 30, and becomes smaller the smaller the gear ratio of the transmission. According to the embodiment, the relationship between the target vehicle height and the index is the relationship ( Fig. between the target vehicle height Ht and the gear ratio Rt of the transmission, which is set so that the smaller the gear ratio of the transmission, the lower the vehicle height. Therefore, even if the equivalent moment of inertia I P of the drive system 14 changes with a change in the gear ratio of the transmission, the vehicle height can be controlled so that the smaller the equivalent moment of inertia, the lower the vehicle height.

[0064] Furthermore, according to the embodiment, the shock absorber 18 is arranged to be inclined forward / forward at the angle α. The angle γ of the backward inclination of the locus 36 and the angle α of the forward inclination are set so that the first longitudinal force F X1 at least partly by the second longitudinal force F X2 is generated by the backward inclination of the locus and the third longitudinal force F X3 generated by the damping force of the shock absorber 18. Therefore, even if the equivalent moment of inertia of the drive system changes, a change in the longitudinal force F acting on the wheel X1 + F X2 + F X3 can be effectively reduced compared to where the shock absorber 18 is arranged without forward / forward inclination.

[0065] Although the present invention has been described in detail with reference to the specific embodiment, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiment and various other embodiments are possible within the scope of the present invention.

[0066] For example, in the embodiment described above, the relationship between the index indicating the equivalent moment of inertia I P of the drive system 14, and the target vehicle height Ht, the relationship between the gear ratio Rt of the transmission 30 and the target vehicle height Ht ( Fig. 13A). However, in a vehicle height control device applied to a vehicle in which the transmission 30 is a multi-stage transmission, the relationship between the index and the target vehicle height Ht may be a relationship between the gear stage St of the transmission 30 and the target vehicle height Ht (modified example). In this case, the relationship between the gear stage St and the target vehicle height Ht is set such that the higher the gear stage, the lower the target vehicle height, as shown in Fig. 13B for example.

[0067] Fig. 13B shows an example of a relationship between a gear stage St of the transmission 30 and the target vehicle height Ht based on Fig. 12 and the relationship between the equivalent moment of inertia I P of the drive system 14 and the gear St of the transmission 30. In particular, the black circles in Fig. 13B are examples of the positions of the gear stages. Furthermore, in the modified example, in step S10 in Fig. 14, a signal indicating a gear stage St is read, and in step S20, with reference to a map indicating Fig. 13B and is based on the gear St, determines a target vehicle height Ht.

[0068] Since the gear ratio Rt of the gearbox 30 becomes smaller the higher the gear stage St of the gearbox, the equivalent moment of inertia I P of the drive system 14 is smaller, the higher the gear ratio of the transmission is. According to the modified example, the higher the gear ratio St of the transmission 30, the lower the target vehicle height Ht. Therefore, even if the equivalent moment of inertia I Pof the drive system 14 fluctuates when the gear stage of the transmission changes, the vehicle height can be controlled so that the smaller the equivalent moment of inertia, the lower the vehicle height.

[0069] Furthermore, in the above-described embodiment, the shock absorber 18 is arranged between the wheel carrier 22 and the vehicle body 34 in a forward / forward tilted state. However, the shock absorber 18 may also be arranged without forward / forward tilt. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2009 - 40349 A

[0002]

Claims

[1] A vehicle height control device (10) applied to a vehicle (20) equipped with: a wheel (12) rotatably supported by a wheel carrier (22) about a rotation axis (24) and having a tire; a drive system (14) rotatably driving the wheel by a drive source (28) via a transmission (30); and a suspension arm (16) disposed between the wheel carrier (22) and a vehicle body (34), characterized by , that the suspension arm (16) is arranged so that the rotation axis (24), when viewed in the lateral direction of the vehicle, draws a locus (36) which is inclined backward when the wheel (12) moves up and down; the vehicle height control device (10) comprises a vehicle height adjustment device (42) configured to change a vehicle height, and an electronic control unit (44) controlling the vehicle height adjustment device, wherein the electronic control unit is arranged to acquire information about an index (Rt or St) indicating an equivalent moment of inertia (Ip) of the drive system (14) and to control the vehicle height adjustment device so that the smaller the equivalent moment of inertia indicated by the index, the lower the vehicle height (H). [2] A vehicle height control device (10) according to claim 1, wherein an angle (γ) of the backward inclination of the locus (36) is set such that a first longitudinal force (F X1 ) at least partially by a second longitudinal force (F X2) is compensated, and the electronic control unit (44) is arranged to control the vehicle height adjustment device (42) so that a change in the angle (γ) of the backward inclination of the locus (36) required to compensate for a change in the first longitudinal force (F X1 ) due to a change in the equivalent moment of inertia (I P ) by a change in the second longitudinal force (F X2 ) is achieved by changing the vehicle height (H). [3] Vehicle height control device (10) according to claim 2, wherein the electronic control unit (44) stores a relationship between a target vehicle height (Ht) and the index (Rt or St) to achieve, by controlling the vehicle height (H), a change in the angle (γ) of the backward inclination of the locus (36) required to achieve a change in the first longitudinal force (F X1 ) due to a change in the equivalent moment of inertia (I P) by a change in the second longitudinal force (F X2 ) to compensate. [4] The vehicle height control device (10) according to claim 3, wherein the index is a gear ratio (Rt) of the transmission (30), and the relationship is a relationship between a target vehicle height (Ht) and a gear ratio of the transmission, which is set such that the smaller the gear ratio of the transmission, the lower the target vehicle height. [5] The vehicle height control device (10) according to claim 3, wherein the transmission (30) is a multi-stage transmission, the index is a gear stage (St) of the transmission, and the relationship is a relationship between a target vehicle height (Ht) and a gear stage of the transmission, which is set such that the higher the gear stage of the transmission, the lower the target vehicle height.

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