JP5519373B2 - Suspension control device and vehicle control device - Google Patents

Description

  The present invention relates to a suspension control device and a vehicle control device that are mounted on a vehicle such as a four-wheeled vehicle and are preferably used for buffering vibration of the vehicle.

  In general, a vehicle such as an automobile is provided with a damping force adjustment type shock absorber between the vehicle body side and each axle side, and the damping force characteristic by the shock absorber is variable depending on the vehicle posture accompanying the braking operation of the brake, etc. A suspension control device configured to be controlled is mounted (for example, see Patent Document 1).

  This type of conventional suspension control device, for example, has a damping force characteristic in combination with the vehicle stability control device in order to suppress a change in posture caused by a steering operation, a braking operation, etc. of the vehicle and to improve running stability. Control etc. which are changed variably are performed. In other words, the damping force characteristic of the shock absorber on the side of the braking target wheel to which the braking force is applied is soft in the expansion stroke, and is hard in the contraction stroke, and on the non-braking wheel side where the braking force is not applied, the damping force characteristic of the shock absorber. Is controlled to be hard in the expansion stroke and soft in the contraction stroke. Thereby, it is set as the structure which increases the wheel load of a braking wheel transiently.

JP 2003-11635 A

  By the way, in the suspension control device of the prior art, the inventors focused on the wheel load of the wheel in the contraction stroke. When the damping force is hard, the wheel load is larger than when the damping force is soft. We found that the response to the increase was fast, but the maximum amount of wheel load increase was small. In addition, when focusing on the wheel load of the wheel in the extension stroke, when the damping force is hard, the response of wheel load loss (ring load reduction) is faster than when the damping force is soft, but the wheel load We found that the maximum amount of omission is small.

  For this reason, with regard to the wheel load in one stroke of the extension stroke or the contraction stroke, if the wheel load increase or the responsiveness of the drop is improved, the maximum amount of the wheel load increase or the drop is reduced. Both cannot be improved. On the contrary, if the responsiveness is lowered, the maximum amount is improved, so that both the responsiveness and the maximum amount cannot be lowered. Therefore, it has been found that the suspension control device of the prior art has a problem that only one of the responsiveness and the maximum amount can be improved or decreased in both the contraction stroke and the extension stroke of the shock absorber.

  The present invention has been made in view of the problems in the above-described prior art found by the present inventors, and an object of the present invention is to control the response and absolute amount of wheel load increase / decrease, and make the vehicle more It is an object of the present invention to provide a suspension control device and a vehicle control device that can perform safe operation control.

In order to solve the above-mentioned problem, the configuration adopted by the invention of claim 1 is a damping force adjustment type that is interposed between a vehicle body and a wheel of a vehicle and whose damping force characteristics can be adjusted between soft and hard. A vehicle including a shock absorber and a control unit that variably controls a damping force characteristic of the damping force adjustment type shock absorber, and is provided with a vehicle stability control device that stably controls the vehicle by controlling the braking force of the vehicle. In the suspension control device used, the control means is configured to reduce the damping force characteristic of the damping force adjustment type shock absorber of the wheel to which the braking force is applied by a signal for controlling the braking force of the wheel during the contracting process. The contraction stroke control at the time of wheel load increase in which the initial stage is set to the hard side and the latter stage is switched to the soft side, and the damping force adjusting type shock absorber of the wheel to which the braking force is added by the signal for controlling the braking force of the wheel Damping force characteristics And extension stroke control at the time of increasing the wheel load for switching the late hard side together with the initial in a soft side is to have a configuration for executing control of at least hand of.

  According to the present invention, a desired wheel load characteristic can be obtained by the above-described configuration.

1 is a perspective view showing a four-wheeled vehicle to which a suspension control device according to a first embodiment of the present invention is applied. It is a control block diagram which shows the suspension control apparatus by 1st Embodiment. It is a flowchart which shows the damping force control process of each wheel by the controller in FIG. It is a flowchart which shows the damping force calculation process at the time of vehicle stability control action | operation in step 8 in FIG. It is a flowchart which shows the damping force calculation process of the wheel which wants to increase the wheel load in FIG. It is a flowchart which shows the damping force calculation process of the wheel which wants to reduce the wheel load in FIG. FIG. 6 is a characteristic diagram of wheel load, acceleration, speed, and damping force command shown in comparison with a case where the damping force is fixed to hardware and when the damping force is fixed to hardware, in the contraction stroke control on the wheel side where it is desired to increase the wheel load. FIG. 6 is a characteristic diagram of wheel load, acceleration, speed, and damping force command shown in comparison with a case where damping force is fixed to hardware and softly fixed in extension stroke control on the wheel side where it is desired to increase wheel load. FIG. 5 is a characteristic diagram of wheel load, acceleration, speed, and damping force command shown in comparison with a case where damping force is fixed to hardware and software is fixed in extension stroke control on the wheel side where it is desired to reduce wheel load. FIG. 5 is a characteristic diagram of wheel load, acceleration, speed, and damping force command shown in comparison with a case where the damping force is fixed to hardware and when the damping force is fixed to hardware, in the contraction stroke control on the wheel side where it is desired to reduce the wheel load. It is a flowchart which shows the damping force calculation process in the case of switching smoothly the damping force of the wheel which wants to increase the wheel load by 2nd Embodiment. Wheel load, acceleration, speed, and damping force command characteristic lines when compared with the case where the damping force is fixed to the hard and the control to the wheel side where you want to increase the wheel load when the damping force is fixed to the hard FIG. It is a flowchart which shows the damping force calculation process in the case of switching smoothly the damping force of the wheel which wants to reduce the wheel load by 2nd Embodiment. Wheel load, acceleration, speed, and damping when the damping force is fixed to the hard and soft when the control of the expansion and contraction strokes on the wheel is desired to reduce the wheel load in the extension and contraction strokes. It is a characteristic diagram of a force command.

  Hereinafter, a suspension device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings, taking as an example a case where the suspension device is applied to a four-wheeled vehicle.

  Here, FIG. 1 to FIG. 10 show a first embodiment of the present invention. In the figure, reference numeral 1 denotes a vehicle body constituting a vehicle body. On the lower side of the vehicle body 1, for example, left and right front wheels 2 (only one shown) and left and right rear wheels 3 (only one shown) are shown. Is provided.

  Reference numerals 4 and 4 are front wheel side suspension devices provided between the left and right front wheel 2 sides and the vehicle body 1, and each suspension device 4 includes left and right suspension springs 5 (hereinafter referred to as springs). 5), and left and right damping force adjustable dampers 6 (hereinafter referred to as damping force variable dampers 6) provided between the left and right front wheels 2 and the vehicle body 1 in parallel with the springs 5. And).

  7 and 7 are rear wheel side suspension devices provided between the left and right rear wheel 3 sides and the vehicle body 1, and each suspension device 7 includes left and right suspension springs 8 (hereinafter referred to as the left and right suspension springs 8). , Springs 8) and left and right damping force adjustable shock absorbers 9 (hereinafter referred to as damping forces) provided between the left and right rear wheels 3 and the vehicle body 1 in parallel with the springs 8. The variable damper 9).

  Here, the damping force variable dampers 6 and 9 of the suspension devices 4 and 7 are configured using a damping force adjustable hydraulic shock absorber. The damping force variable dampers 6 and 9 have a damping force adjusting valve and an actuator (not shown) for continuously adjusting the damping force characteristic from a hard characteristic (hard characteristic) to a soft characteristic (soft characteristic). A damping force adjusting mechanism is attached. Note that the damping force adjustment valve does not necessarily have a configuration in which the damping force characteristic is continuously changed, and may be a configuration in which the damping force characteristic is intermittently adjusted in two stages or three or more stages. As this damping force adjusting valve, a well-known structure such as a pressure control method for controlling the pilot pressure of the damping force generating valve and a flow rate control method for controlling the passage area can be used.

  Reference numeral 10 denotes a plurality of sprung acceleration sensors provided on the vehicle body 1. Each of the sprung acceleration sensors 10 detects the vibration acceleration in the left and right directions in order to detect the vibration acceleration in the upper and lower directions on the vehicle body 1 side above the spring. It is attached to the vehicle body 1 at a position near the upper end side (rod protruding end side) of the damping force variable damper 6 on the front wheel 2 side, and near the upper end side (rod protruding end side) of the damping force variable damper 9 on the rear wheel 3 side. It is attached to the vehicle body 1 even at the position. The sprung acceleration sensor 10 constitutes a road surface state detector that detects the road surface state as upward and downward vibration acceleration while the vehicle is traveling, and outputs a detection signal to the controller 14 described later. The sprung acceleration sensor 10 may be provided on all four wheels, or may be provided as any one of the left and right front wheels and the left and right rear wheels. Alternatively, only one may be provided on the vehicle body and estimated from the values of other longitudinal acceleration sensors.

  Reference numeral 11 denotes a plurality of unsprung acceleration sensors provided on each front wheel 2 side and each rear wheel 3 side of the vehicle. The unsprung acceleration sensors 11 include the left and right front wheels 2 side and the left and right rear wheels. On the third side, the vibration acceleration in the upward and downward directions is detected for each wheel, and the detection signal is output to the controller 14 described later.

  The unsprung (axle) side acceleration signal from the unsprung acceleration sensor 11 is converted from the unsprung acceleration sensor 10 to the unsprung (vehicle body 1) side in a calculation process (see step 4 in FIG. 3) by the controller 14 described later. The acceleration relative to each other is subtracted, whereby the damper relative acceleration between the sprung and unsprung parts is calculated. Further, by integrating the relative acceleration between the sprung and unsprung parts, the relative speeds in the upper and lower directions between the front wheels 2 and the rear wheels 3 and the vehicle body 1 are calculated.

  Reference numeral 12 denotes a braking device such as a hydraulic disc brake, a drum brake, or the like provided on each front wheel 2 side and rear wheel 3 side of the vehicle. Each brake device 12 is provided with a wheel cylinder hydraulic pressure sensor 12A. Each wheel cylinder hydraulic pressure sensor 12A individually detects the brake hydraulic pressure for each wheel on the left and right front wheel 2 side and the left and right rear wheel 3 side, and each detection signal is sent to a controller 14 described later. Is output. That is, the controller 14 performs a braking operation on any of the braking devices 12 on the side of the left and right front wheels 2 and the left and right rear wheels 3 in accordance with detection signals from the wheel cylinder hydraulic pressure sensors 12A. The brake wheel discrimination shown in step 11 in FIG. 4 is performed. As the braking device 12, an electromagnetic brake may be used. In this case, an ammeter may be used instead of the wheel cylinder hydraulic pressure sensor 12A.

  Here, the wheel cylinder hydraulic pressure sensor 12A provided for each wheel constitutes a braking wheel detection means. For example, the brake wheel discrimination may be performed using a signal output from the vehicle stability controller 13 described later, and the brake wheel detection means may be configured by means other than the wheel cylinder hydraulic pressure sensor 12A.

  Reference numeral 13 denotes a vehicle stability control device provided on the vehicle body 1 side. The vehicle stability control device 13 includes various kinds of sensors such as a steering angle sensor, a front and rear acceleration sensor, a yaw rate sensor, and a wheel speed sensor mounted on the vehicle. The vehicle running state is calculated based on signals from sensors (both not shown), and stable control during vehicle running is performed as follows based on the calculation result.

  That is, the vehicle stability control device 13 is configured to, for example, understeer due to side slip on the front wheel 2 side (a state in which the vehicle tends to face outward in the turning direction with respect to the steering angle) or oversteer due to side slip on the rear wheel 3 side (steering angle The left and right front wheels 2 and the left and right front wheels 2 to return the vehicle to a stable state according to the driving state of the vehicle. The braking force required for the rear wheel 3 is calculated. Then, the vehicle stability control device 13 operates the brake fluid pressure control device 13A based on the calculation result, and performs independent braking control (increase, decrease, or release of the braking force) for each wheel. The turning moment and the deceleration force are controlled to control turning stability and course traceability.

  The brake hydraulic pressure control device 13A is a braking force control means according to the present invention, and includes a pump and a control valve, and supplies hydraulic pressure to the brake device 12 as necessary. The braking force control means is constituted by a current control device in the case of an electromagnetic brake.

  Reference numeral 14 denotes a controller as a control means constituted by a microcomputer or the like. As shown in FIG. 2, the controller 14 has a sprung acceleration sensor 10, an unsprung acceleration sensor 11, a wheel cylinder hydraulic pressure sensor 12A, a vehicle on the input side. The output side is connected to an actuator (not shown) of the damping force variable dampers 6 and 9 and the like.

  The controller 14 includes a storage unit 14A including a ROM, a RAM, a nonvolatile memory, and the like, and the control processing program and the like shown in FIGS. 3 to 6 are stored in the storage unit 14A. Then, the controller 14 calculates a damping force command signal to be output to an actuator (not shown) of each damping force variable damper 6, 9 as a current value according to the damping force control processing of each wheel shown in FIG. Each of the damping force variable dampers 6 and 9 is controlled so that the generated damping force is continuously variable between hardware and software or in a plurality of stages according to the current value (damping force command signal) supplied to the actuator.

  The suspension control apparatus according to the present embodiment has the above-described configuration. Next, processing for variably controlling the damping force characteristics of the damping force variable dampers 6 and 9 by the controller 14 will be described.

  First, the controller 14 executes a damping force control process for each wheel as shown in FIG. That is, initial setting is performed in step 1 in FIG. 3, and time management is performed in the next step 2 to adjust the control cycle. In step 3, sensor input is performed, and signals from the sprung acceleration sensor 10, the unsprung acceleration sensor 11, the wheel cylinder hydraulic pressure sensor 12A, the vehicle stability control device 13, and the like are read.

  In the next step 4, the damper relative acceleration and relative speed (for example, see FIGS. 7 to 10) for each wheel are calculated and obtained. In this case, by subtracting the unsprung acceleration signal from the unsprung acceleration sensor 11 and the unsprung acceleration signal from the unsprung acceleration sensor 10, the damper relative acceleration between the unsprung and unsprung parts is calculated. Further, by integrating the relative acceleration between the sprung and unsprung parts, the relative speeds in the upper and lower directions between the front wheels 2 and the rear wheels 3 and the vehicle body 1 are calculated. Relative acceleration and relative speed are shown with the damper extension side as positive and the contraction side as negative.

  In the next step 5, a damping force command signal according to these calculation results is input. In the next step 6, a vehicle stability control operation signal is input from the vehicle stability control device 13. In step 7, it is determined whether vehicle stability control is being executed based on the vehicle stability control operating state signal.

  If “YES” is determined in step 7, since the vehicle stability control is being performed, the process proceeds to the next step 8, and the damping force calculation processing for each wheel during the vehicle stability control operation shown in FIG. This is executed to variably control the wheel load for each wheel. In the next step 9, a damping force command signal (target damping force signal) is output for each wheel to perform variable control of the damping force, and thereafter, the processing in step 2 and subsequent steps is repeated.

  Further, when “NO” is determined in step 7, since the vehicle stability control is not performed, the process proceeds to step 10 to execute the damping force calculation process for each wheel when the vehicle stability control is not operated as the normal control. . As normal control, vibration suppression control such as skyhook control, rough road control while traveling on rough roads, roll, anti-dive, squat control, and the like are performed. In the next step 9, the damping force command signal (target damping force signal) of each wheel calculated in step 10 is output to variably control the damping force.

  Next, the damping force calculation process for each wheel during the vehicle stability control operation shown in FIG. 4 will be described. First, in step 11, whether the braking operation is being performed on any of the left and right front wheels 2 and the left and right rear wheels 3 according to the detection signal from each wheel cylinder hydraulic pressure sensor 12A is determined. This is performed as a brake wheel discrimination.

  In the next step 12, it is determined whether or not each wheel is a braking wheel, and the processing of step 13 is performed on the wheel side determined as “YES”. That is, in step 13, the damping force is calculated on the side of the wheel (the wheel to be braked) whose wheel load is to be increased, and the process returns in the next step 14. On the side of the wheel determined as “NO” in step 12, the process proceeds to step 15 to calculate a damping force as a wheel for which the wheel load is to be reduced, and the process returns in the next step 14.

  In the damping force calculation process shown in FIG. 4, the case where the braking wheel is set to a wheel where the wheel load is desired to be increased has been described as an example for the purpose of improving the braking force. However, when the control of the present invention is used for another purpose, any wheel may be set as a wheel for which the wheel load is to be increased and a wheel for which the wheel load is to be decreased regardless of whether the wheel is a braking wheel or a non-braking wheel. . Further, for example, it may be set to a wheel whose load is to be increased and a wheel which is to be decreased in accordance with the operation of the antilock brake system.

  Next, the calculation of the damping force on the wheel side at which the wheel load to be increased in step 13 is performed by the calculation process shown in FIG. That is, in step 21 in FIG. 5, it is determined whether or not the relative acceleration a between the sprung and unsprung portions is negative (a <0). In this case, the relative acceleration a between the unsprung and unsprung portions is calculated by the process of step 4 shown in FIG.

When it is determined as “YES” in step 21 (that is, the relative acceleration a is negative), the process proceeds to the next step 22 where the damping force command signal I is set as the hard command signal I _H and the wheel load on the corresponding wheel side is determined. The rate of increase is increased in the contraction stroke, and the minimum value is increased in the expansion stroke. The hardware command signal I _H is a signal for changing the command signal to the hardware side relatively by a predetermined value with respect to the previous damping force command signal I, and is switched between software and hardware in two stages. It does not necessarily mean a signal. Further, the hard command signal I _H is by other conditions such as vehicle speed, may be changed. Then, after the process of step 22, the process returns at the next step 23.

If “NO” is determined in the step 21, the process proceeds to a step 24 to determine whether or not the relative acceleration a of the corresponding damper is zero (a ≠ 0). When it is determined as “YES” in step 24 (ie, the relative acceleration a is positive), the process proceeds to the next step 25 where the damping force command signal I is set as the soft command signal _IS and the wheel load on the corresponding wheel side is determined. The maximum value is increased in the contraction stroke, and the decrease rate is decreased in the expansion stroke. Note that the soft command signal I _S, a signal for changing a command signal to the relatively soft side by the value amount previously determined than the previous damping force command signal I, switching two-stage soft and hard It does not necessarily mean a signal. Further, the soft command signal I _S is by other conditions such as other vehicle speed may be changed. After step 25, the process returns at next step 23.

  When it is determined as “NO” in step 24 (that is, the relative acceleration a is zero), the process proceeds to the next step 26 to set the damping force command signal I to a signal that is maintained similarly to the previous damping force command signal I. In the processing of steps 21 and 24, the relative acceleration a may vibrate in the vicinity of zero (0) due to the influence of noise or the like, and the reversal of positive and negative may be repeated. Therefore, in such a case, a range is provided for the value at which the relative acceleration a is near zero (for example, the condition of step 21 may be “a <− | d |”), or relative speed and relative It may be configured to use the fact that the phase difference from the acceleration is 90 degrees, or to perform the stroke discrimination between the contraction stroke and the extension stroke.

  Here, FIGS. 7 and 8 respectively show test data for the contraction stroke and the extension stroke when the wheel damping force calculation processing for increasing the wheel load shown in FIG. 5 is applied to the suspension control of the vehicle. A characteristic line 15 indicated by a solid line in FIG. 7 indicates the characteristic of the wheel load in the contraction stroke on the wheel side where it is desired to increase the wheel load according to the present embodiment (hereinafter referred to as the first example), and is indicated by a one-dot chain line. A line 16 indicates a wheel load characteristic when the damping force is fixed to soft, and a characteristic line 17 indicated by a two-dot chain line indicates a wheel load characteristic when the damping force is fixed to hard.

  In addition, a characteristic line 18 indicated by a solid line in FIG. 7 indicates the characteristic of relative acceleration according to the first embodiment, and a characteristic line 19 indicated by a one-dot chain line indicates a characteristic indicated by a two-dot chain line when the damping force is fixed softly. Lines 20 indicate the acceleration characteristics when the damping force is fixed to hardware. Further, a characteristic line 21 shown by a solid line in FIG. 7 shows the characteristic of the damper relative speed according to the first embodiment, and a characteristic line 22 shown by a one-dot chain line is shown by a two-dot chain line when the damping force is fixed softly. The characteristic line 23 indicates the speed characteristic when the damping force is fixed to hardware.

As shown by the characteristic line 20 in FIG. 7, when the damping force on the wheel side where the wheel load is desired to be increased is fixed to the hard side, the relative acceleration becomes a negative value, for example, between about 0 and 0.39 seconds. . Therefore, the during which the processing of steps 21 and 22 in FIG. 5, a damping force command signal I as a hard command signal I _H, set to increase in the contraction stroke of the wheel load of the corresponding wheel side. For this reason, for example, the characteristic of the wheel load according to the first embodiment is about 0 to 0.39 seconds, for example, the characteristic of the wheel load when the damping force is fixed as shown by the characteristic line 15 shown by the solid line (2 It is set to a characteristic similar to the characteristic line 17) indicated by the dotted line (characteristic in which the wheel load increases faster compared to the soft fixation).

Then, when the time of about 0.39 seconds in FIG. 7 has passed, as shown by the characteristic line 20 indicated by a two-dot chain line, the relative acceleration is changed from a negative value to zero or more and becomes a positive value (relative speed is 2). When the minimum value as shown by the characteristic line 23 shown by the dotted line, that is, the maximum in the negative direction in the contraction stroke), the damping force command signal I is changed to the soft command signal I _S by the processing of steps 21, 24, and 25 in FIG. And set so that the damping force on the corresponding wheel side becomes soft. Thereby, the characteristic of the wheel load according to the first embodiment is the characteristic when the damping force is fixed to soft and hard for a time period of, for example, about 0.39 to 0.55 seconds as shown by the characteristic line 15 shown by a solid line. It is suppressed to a value smaller than the lines 16 and 17.

  However, for example, after a time of 0.55 seconds, the wheel load according to the first embodiment becomes larger than the characteristic line 17 in the case of being fixed to the hardware. The wheel load characteristic according to one embodiment is larger than the characteristic lines 16 and 17 when fixed to soft and hard as indicated by the characteristic line 15. Then, the wheel load according to the first embodiment is increased to a maximum value of, for example, 7.5 (kN) in a period of about 0.67 to 0.7 seconds.

Therefore, according to the present embodiment, in the contraction stroke on the wheel side where it is desired to increase the wheel load, as shown by the characteristic line 24 shown by the solid line in FIG. The damping force command is set to the hard side (the damping force command signal I is set to the hard command signal I _H ), and at the later stage (for example, between 0.39 and 0.8 seconds), the damping command is set. By switching the force command to the soft side (damping force command signal I is the soft command signal I _S ) and setting it, the wheel load is quickly raised as shown by the characteristic line 15 in the contraction stroke on the wheel side where the wheel load is to be increased. As a result, the responsiveness can be improved and the maximum value of the wheel load increase can be increased to, for example, about 7.5 (kN).

  Next, a characteristic line 25 indicated by a solid line in FIG. 8 indicates the characteristic of the wheel load of the first embodiment in the extension stroke on the wheel side where it is desired to increase the wheel load. On the other hand, a characteristic line 26 indicated by a one-dot chain line indicates a wheel load characteristic when the damping force is fixed to soft, and a characteristic line 27 indicated by a two-dot chain line indicates a wheel load characteristic when the damping force is fixed to hard.

  Further, a characteristic line 28 shown by a solid line in FIG. 8 shows the characteristic of relative acceleration according to the first embodiment, and a characteristic line 29 shown by an alternate long and short dash line indicates a characteristic indicated by a two-dot chain line when the damping force is fixed softly. Lines 30 indicate the characteristics of acceleration when the damping force is fixed to hardware. Further, a characteristic line 31 shown by a solid line in FIG. 8 shows the characteristic of the damper relative speed according to the first embodiment, and a characteristic line 32 shown by a one-dot chain line shows a two-dot chain line when the damping force is fixed softly. A characteristic line 33 indicates a speed characteristic when the damping force is fixed to hardware.

As shown by the characteristic line 30 in FIG. 8, when the damping force of the extension stroke is softly fixed on the wheel side where it is desired to increase the wheel load, for example, the relative acceleration is a positive value during the time from about 0 to 0.37 seconds. It becomes. Therefore, the during which the processing of steps 21, 24 and 25 in FIG. 5, a damping force command signal I and the soft command signal I _S, the damping force at the relevant wheel side is set to be softer. For this reason, for example, until about 0 to 0.37 seconds, the wheel load characteristic according to the first embodiment is the wheel load characteristic when the damping force is fixed softly (as indicated by the characteristic line 25 shown by the solid line). The characteristic is the same as the characteristic line 26) indicated by the chain line (characteristic that the wheel load decreases more slowly than in the case of hardware fixation).

Then, when the time of about 0.37 seconds in FIG. 8 has passed, as shown by the characteristic line 29 shown by a one-dot chain line, the relative acceleration is reduced from a positive value to zero or less and a negative value (relative speed is one-dot chain line). becomes the maximum) as the characteristic line 32 shown in, the process of step 21 in FIG. 5, a damping force command signal I as a hard command signal I _H, the damping force of the appropriate wheel side and harder Set as follows. Thus, the wheel load characteristic according to the first embodiment is the characteristic when the damping force is fixed to soft or hard for a time period of about 0.37 to 0.48 seconds, for example, as indicated by the characteristic line 25 shown by a solid line. It is suppressed to a value smaller than the lines 26 and 27.

  However, for example, after the time of 0.48 seconds, the wheel load according to the first embodiment becomes larger than the characteristic line 26 when fixed to the soft, for example, between the time 0.55 and 0.8 seconds, The wheel load characteristic according to one embodiment is larger than the characteristic lines 26 and 27 when fixed to soft and hard as indicated by the characteristic line 25. The wheel load according to the first embodiment decreases to, for example, 2.6 to 2.7 (kN) when the time is about 0.37 to 0.4 seconds, for example, 0.57 to 0.6 seconds. For example, it is increased to 2.9 (kN) or more.

Therefore, according to the present embodiment, on the wheel side where it is desired to increase the wheel load, as shown by the characteristic line 34 shown by the solid line in FIG. ) Sets the damping force command to the soft side (the damping force command signal I is set to the soft command signal I _S ), and at the later stage (for example, between 0.37 and 0.8 seconds), the damping force command is set to the hard side. By switching and setting the damping force command signal I to the hard command signal I _H , the responsiveness when the wheel load is reduced as indicated by the characteristic line 25 on the wheel side where the wheel load is to be increased (the wheel load missing) ) Can be delayed, and the maximum amount of wheel load loss (minimum value of wheel load) can be made smaller than in the case of soft fixing (characteristic line 26).

Next, the calculation of the damping force of the wheel for which the wheel load is to be reduced in the step 15 is performed by the calculation process shown in FIG. That is, in step 31 in FIG. 6, it is determined whether or not the relative acceleration a between the sprung and unsprung portions is negative (a <0). When it is determined as “YES” in step 31 (that is, the relative acceleration a is negative), the process proceeds to the next step 32 where the damping force command signal I is set as the soft command signal _IS and the corresponding wheel (for example, non-braking) The wheel load on the wheel side is reduced to reduce the rate of increase in the stroke, and the minimum value is reduced in the stroke. After the processing in step 32, the process returns in the next step 33.

If “NO” is determined in the step 31, the process proceeds to a step 34 to determine whether or not the relative acceleration a of the corresponding damper (each of the damping force variable dampers 6 and 9) is zero (a ≠ 0). judge. When it is determined “YES” in step 34 (that is, the relative acceleration a is positive), the process proceeds to the next step 35 where the damping force command signal I is set as the hardware command signal _IH and the corresponding wheel (for example, non-braking) The wheel load on the wheel side is reduced to reduce the maximum value in the stroke, and the reduction rate is increased in the stroke. After step 35, the process returns at the next step 33.

  When it is determined “NO” in step 34 (that is, relative acceleration a is zero), the process proceeds to the next step 36 where the damping force command signal I is set to a signal that is maintained in the same manner as the previous damping force command signal I. It should be noted that in the processing of steps 31 and 34 as well, the width of the value at which the relative acceleration a is near zero is set, or the fact that the phase difference between the relative speed and the relative acceleration is 90 degrees is used to reduce the shrinkage. It is good also as a structure which performs the stroke discrimination | determination with a stroke and an extension stroke.

  Here, FIG. 9 and FIG. 10 show test data when the wheel side damping force calculation processing for reducing the wheel load shown in FIG. 6 is applied to vehicle suspension control. A characteristic line 35 shown by a solid line in FIG. 9 shows the wheel load characteristic of the first embodiment in the extension stroke on the wheel side where it is desired to reduce the wheel load, and a characteristic line 36 shown by a one-dot chain line fixes the damping force softly. In this case, a characteristic line 37 indicated by a two-dot chain line indicates a wheel load characteristic when the damping force is fixed to hardware.

  In addition, a characteristic line 38 indicated by a solid line in FIG. 9 indicates the characteristic of relative acceleration according to the first embodiment, and a characteristic line 39 indicated by a one-dot chain line indicates a characteristic indicated by a two-dot chain line when the damping force is fixed softly. Lines 40 show the acceleration characteristics when the damping force is fixed to hardware. Further, a characteristic line 41 shown by a solid line in FIG. 9 shows the characteristic of the damper relative speed according to the first embodiment, and a characteristic line 42 shown by a one-dot chain line shows a two-dot chain line when the damping force is fixed softly. A characteristic line 43 indicates a speed characteristic when the damping force is fixed to hardware.

As shown by the characteristic line 40 in FIG. 9, when the damping force in the extension stroke on the wheel side where the wheel load is desired to be reduced is fixed to hard, for example, the relative acceleration is positive during the period from about 0 to 0.41 seconds. Value. Therefore, the during which the processing of steps 31, 34, 35 in FIG. 6, a damping force command signal I as a hard command signal I _H, set so as to reduce in the contraction stroke of the wheel load of the corresponding wheel side. For this reason, for example, between about 0 to 0.41 seconds, the wheel load characteristic according to the first embodiment is the wheel load characteristic (2) when the damping force is fixed as shown by the characteristic line 35 shown by the solid line. The characteristic is set to be similar to the characteristic line 37) indicated by the dotted line.

Then, when the time of about 0.41 seconds in FIG. 9 has passed, the relative acceleration is reduced from a positive value to less than zero as shown by a characteristic line 40 indicated by a two-dot chain line, and a negative value (relative speed is 2). becomes the maximum) as the characteristic line 43 shown by a point chain line, the process of step 31 in FIG. 6, a damping force command signal I and the soft command signal I _S, the damping force at the relevant wheel side elongation Set to be soft in the process. Thereby, the characteristic of the wheel load according to the first embodiment is the characteristic when the damping force is fixed to soft and hard for a time period of about 0.41 to 0.56 seconds, for example, as shown by the characteristic line 35 shown by a solid line. The value is larger than those of the lines 36 and 37.

  However, for example, after a time of 0.56 seconds, the wheel load according to the first embodiment becomes smaller than the characteristic line 37 in the case of being fixed to the hardware. The wheel load characteristic according to one embodiment is smaller than the characteristic lines 36 and 37 when fixed to soft and hard as indicated by the characteristic line 35. Then, the wheel load according to the first embodiment is reduced to a minimum value that is, for example, 1.5 (kN) or less in about 0.71 to 0.73 seconds.

Therefore, according to the present embodiment, in the extension stroke on the wheel side where it is desired to reduce the wheel load, as shown by the characteristic line 44 shown by the solid line in FIG. The damping force command is set to the hard side (the damping force command signal I is set to the hard command signal I _H ), and at the later stage (for example, between 0.41 and 0.8 seconds), the damping command is set. By switching and setting the force command to the soft side (damping force command signal I is the soft command signal I _S ), the wheel load can be quickly reduced as indicated by the characteristic line 35 on the wheel side where the wheel load is to be reduced. It is possible to improve the responsiveness of dropout, and to reduce the wheel load to a minimum value that is, for example, 1.5 (kN) or less, and to increase the maximum value of wheel load dropout.

  Next, a characteristic line 45 indicated by a solid line in FIG. 10 indicates the characteristic of the wheel load of the first embodiment in the contraction stroke on the wheel side where it is desired to reduce the wheel load. On the other hand, a characteristic line 46 indicated by a one-dot chain line indicates a wheel load characteristic when the damping force is fixed to soft, and a characteristic line 47 indicated by a two-dot chain line indicates a wheel load characteristic when the damping force is fixed to hard.

  In addition, a characteristic line 48 indicated by a solid line in FIG. 10 indicates the characteristic of relative acceleration according to the first embodiment, and a characteristic line 49 indicated by an alternate long and short dash line indicates a characteristic indicated by a two-dot chain line when the damping force is fixed softly. Lines 50 respectively show the characteristics of acceleration when the damping force is fixed to hardware. Furthermore, a characteristic line 51 shown by a solid line in FIG. 10 shows the characteristic of the damper relative speed according to the first embodiment, and a characteristic line 52 shown by a one-dot chain line shows a two-dot chain line when the damping force is fixed softly. A characteristic line 53 indicates a speed characteristic when the damping force is fixed to hardware.

As shown by the characteristic line 50 in FIG. 10, when the damping force of the contraction stroke is softly fixed on the wheel side where it is desired to reduce the wheel load, for example, the relative acceleration is a negative value during the time from about 0 to 0.35 seconds. It becomes. Therefore, the during which the processing of steps 31 and 32 in FIG. 6, a damping force command signal I and the soft command signal I _S, the damping force at the relevant wheel side is set to be softer. For this reason, for example, until about 0 to 0.35 seconds, the wheel load characteristic according to the first embodiment is the wheel load characteristic when the damping force is softly fixed (as indicated by the characteristic line 45 shown by the solid line). A characteristic similar to the characteristic line 46) indicated by the chain line is set.

Then, when the time of about 0.35 seconds in FIG. 10 has passed, as shown by a characteristic line 49 indicated by a one-dot chain line, the relative acceleration becomes zero or more from a negative value to a positive value (relative speed is one-dot chain line). 6, the damping force command signal I is changed to the hard command signal I _H by the processing of steps 31, 34, and 35 in FIG. 6. Set the damping force on the corresponding wheel side to be harder. Thus, the wheel load characteristic according to the first embodiment is the characteristic when the damping force is fixed to soft or hard for a time period of about 0.35 to 0.45 seconds, for example, as indicated by a characteristic line 45 shown by a solid line. It becomes a value larger than the lines 46 and 47.

  However, for example, between about 0.45 and 0.71 seconds, the wheel load according to the first embodiment becomes smaller than the characteristic line 46 when fixed to soft, for example, between 0.51 and 0.8 seconds. In the meantime, the wheel load characteristic according to the first embodiment is smaller than the characteristic line 47 when fixed to hardware as indicated by the characteristic line 45. The wheel load according to the first embodiment increases to, for example, about 7 (kN) when the time is about 0.35 to 0.4 seconds, for example, when the time is about 0.52 to 0.6 seconds, For example, it is reduced to about 6.8 (kN).

Therefore, according to the present embodiment, on the wheel side where it is desired to reduce the wheel load, as shown by a characteristic line 54 shown by a solid line in FIG. ) Sets the damping force command to the soft side (the damping force command signal I is set to the soft command signal I _S ). In the later stage (for example, between 0.35 and 0.8 seconds), the damping force command is set to the hard side. By switching and setting the side (the damping force command signal I to the hard command signal I _H ), the responsiveness when the wheel load increases as shown by the characteristic line 45 can be delayed on the wheel side where it is desired to reduce the wheel load. The maximum amount of wheel load increase (the maximum value of the wheel load) can be suppressed smaller than that in the case of soft fixing (characteristic line 46).

  Thus, according to the first embodiment, by adopting the configuration as described above, for the wheel whose wheel load is to be increased, the characteristic line shown in FIG. 7 is shown in the contraction stroke of each damping force variable damper 6 (9). As shown in FIG. 15, the wheel load can be quickly raised and the maximum amount of increase in wheel load can be increased. In the extension stroke of each damping force variable damper 6 (9), the wheel load dropout is shown as the characteristic line 25 shown in FIG. The maximum amount of wheel load loss can be reduced while slowing down.

  Further, for a wheel whose wheel load is to be reduced, the wheel load loss is accelerated and the maximum amount of wheel load loss is increased as shown by the characteristic line 35 in FIG. 9 in the extension stroke of each damping force variable damper 6 (9). In the contraction stroke of each damping force variable damper 6 (9), as shown by the characteristic line 45 shown in FIG. 10, the wheel load increase can be slowed and the maximum amount of wheel load increase can be kept small.

  Therefore, regarding the wheel load in one stroke of the expansion stroke or the contraction stroke of each damping force variable damper 6 (9), it is possible to improve both the wheel load increase or drop responsiveness and the maximum amount (absolute amount). On the contrary, when the responsiveness is lowered, the maximum amount (absolute amount) can also be lowered. As a result, the vehicle can be more safely controlled.

  Next, FIGS. 11 to 14 show a second embodiment of the present invention. The feature of the second embodiment is that the damping force characteristic of the damper (damper) is continuously set between the hardware and the software in order to smoothly perform the control for increasing the wheel load and the control for decreasing the wheel load. The configuration is to switch smoothly. There are several methods for smoothly switching between the two controls. In this embodiment, the inversion of the sign of the acceleration is set at the start of switching, and gradually from one control to another control during a predetermined time. We are going to switch. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Here, FIG. 11 shows a wheel damping force calculation process for increasing the wheel load. For example, the wheel damping force calculation for increasing the wheel load in step 13 in FIG. 4 is embodied as a case where the damping force is smoothly switched. Is. That is, in step 41 in FIG. 11, whether or not the relative acceleration a between the sprung and unsprung is zero (a = 0), or the relative speed v between the sprung and unsprung is zero (v = 0).

  When it is determined “YES” in step 41, the relative acceleration a of the damping force variable damper 6 or 9 is zero at the corresponding wheel (either the left or right front wheel 2 or the left or right rear wheel 3) ( a = 0) or the relative speed v is zero (v = 0), the process proceeds to the next step 42 and the damping force command signal I is maintained in the same manner as the previous damping force command signal I. Set to signal. In the next step 43, the timer T for setting the damping force switching time is reset to zero (T = 0), and the process returns in the next step 44.

  Even in the processing of step 42, the relative acceleration a may vibrate near zero (0) due to the influence of noise or the like, and may be repeatedly reversed positively and negatively. It is also possible to employ a configuration in which the stroke is discriminated between the contraction stroke and the extension stroke by using a width of the angle or utilizing the fact that the phase difference between the relative speed and the relative acceleration is 90 degrees. This also applies to the relative speed v.

Next, in step 45, it is determined whether or not the relative speed v is negative (v <0). In this case, the relative speed v between the sprung and unsprung portions is calculated by the process of step 4 shown in FIG. If “YES” is determined in the step 45, the process proceeds to the next step 46 to determine whether or not the relative acceleration a is negative (a <0). When it is determined as “NO” in step 46, the process proceeds to the next step 47, where the damping force command signal I is set as the soft command signal _IS, and the wheel load on the corresponding wheel side is set to increase in the contraction stroke. . In the next step 48, the timer T is reset to zero (T = 0), and the process returns in the next step 44.

  If “YES” is determined in the step 46, the process proceeds to the next step 49 to calculate the damping force command signal I so as to satisfy the following equation (1).

Here, the coefficient A _H-S1 is a constant determined by the above equation (2), and is a hard command signal I _H , a soft command signal I _S (I _S > I _H ), and a time (T _H-S ) that is a constant. Is obtained as a positive coefficient. The damping force command signal I is a signal that increases in proportion to the time of the timer T (damping force switching time) by a coefficient A _H-S1 from a predetermined hardware command signal I _H (see the above equation 3). Is calculated as

In the next step 50, the time of the timer T (damping force switching time) is set to T = T + Δt, and the time is advanced by a predetermined sampling time Δt predetermined for each program cycle. In the next step 52, when the damping force command signal I by the steps 49 and 50 is equal to or large than the soft command signal I _S (I> I _S), is determined as "YES", the next proceeds to step 52 to set the damping force command signal I to the soft command signal I _S of.

Further, when the CPU 51 determines "NO" in the step 51, since the damping force command signal I can be determined to be smaller than the soft command signal I _S, the damping force proceeds to the next step 53 the command signal I is hard command signal I _H It is determined whether or not a smaller value (I <I _H ). When it is determined "YES" in the step 53, it sets the damping-force command signal I then proceeds to the next step 54 the hard command signal I _H.

Between determined as "NO" in step 53, step 49 and 50 the damping force command signal I is greater than the hard command signal I _H according to a value smaller than the soft command signal I _S, in this case, the number 1 A damping force command signal I calculated by the equation is output as a damping force command indicated by a characteristic line 70 in FIG.

  On the other hand, when “NO” is determined in the step 45, the process proceeds to the next step 55 to determine whether or not the relative acceleration a is negative (a <0). If “NO” is determined in the step 55, the process proceeds to the next step 56 to calculate the damping force command signal I so as to satisfy the following equation (4).

Here, the coefficient A _S−H1 is a constant determined by the equation (5), and the hard command signal I _H , the soft command signal I _S (I _S > I _H ), and the time (T _S−H ) that is a constant. Is obtained as a negative coefficient. The damping force command signal I is a signal that decreases in proportion to the time of the timer T (damping force switching time) by a coefficient A _S-H1 from a predetermined soft command signal I _S (see Equation 6 above). Is calculated as And after that, the process over the said steps 50-54 is performed.

If “YES” is determined in the step 55, the process proceeds to the next step 57, where the damping force command signal I is set to the hardware command signal _IH, and the wheel load on the corresponding wheel side is set to be increased. In the next step 58, the timer T is reset to zero (T = 0), and thereafter, the process returns in step 44.

  Here, FIG. 12 shows a comparison of wheel load, relative acceleration, relative speed, and damping force command when the damping force is softly fixed, when the hardware is fixed, and when the wheel is controlled to increase the wheel load. Data are shown. A characteristic line 61 indicated by a solid line in FIG. 12 indicates the characteristics of the wheel load in the contraction stroke and the extension stroke on the wheel side where it is desired to increase the wheel load according to the second embodiment (hereinafter referred to as the second embodiment). A characteristic line 62 indicated by a one-dot chain line indicates a wheel load characteristic when the damping force is fixed softly, and a characteristic line 63 indicated by a two-dot chain line indicates a wheel load characteristic when the damping force is fixed hard. .

  In addition, a characteristic line 64 indicated by a solid line in FIG. 12 indicates the characteristic of relative acceleration according to the second embodiment, and a characteristic line 65 indicated by an alternate long and short dash line indicates an acceleration characteristic when the damping force is fixed softly. A characteristic line 66 indicated by a two-dot chain line indicates an acceleration characteristic when the damping force is fixed to hardware. Further, a characteristic line 67 indicated by a solid line in FIG. 12 indicates a characteristic of the damper relative speed according to the second embodiment, and a characteristic line 68 indicated by a one-dot chain line indicates a characteristic of speed when the damping force is fixed softly. A characteristic line 69 indicated by a two-dot chain line indicates a speed characteristic when the damping force is fixed to hardware.

The relative speed is a negative value during the time period Ta1 to Ta2, and the relative acceleration is also a negative value. Therefore, during this time by the process of step 41,45,46,49 in FIG. 11, the control that increases gradually until it reaches the soft command signal _{I S} is performed a damping force command signal I from the hard command signal _{I H.}

  Between times Ta2 and Ta3, the relative speed is a negative value, and the relative acceleration is a positive value. Then, the damping force is set to be soft by the processing of steps 46 and 47 in FIG.

Next, the relative speed is a positive value during the time Ta3 to Ta4, and the relative acceleration is also a positive value. Therefore, the process of step 45,55,56 in FIG. 11, gradually decreases the control until a hard command signal I _H is performed a damping force command signal I from the soft command signal I _S.

  Further, after time Ta4, the relative speed is a positive value, and the relative acceleration is a negative value. Then, the damping force is set to be hard by the processing of steps 55 and 57 in FIG.

  Next, FIG. 13 shows the damping force calculation processing for a wheel whose wheel load is to be reduced. For example, the calculation of the damping force for a wheel whose wheel load is to be reduced in step 15 in FIG. 4 is embodied as a case where the damping force is smoothly switched. Is. That is, the process from step 61 to step 66 in FIG. 13 is performed in the same manner as the process from step 41 to step 46 shown in FIG.

However, in this case, it is determined as “YES” in Step 66, and when both the relative speed v and the relative acceleration a are negative values, the process proceeds to the next Step 69 and the damping force command signal I is set as the soft command signal. control gradually decreases from I _S to reach the hard command signal I _H is performed. Then, the processing of subsequent steps 70 to 74 is performed in the same manner as the processing of steps 50 to 54 shown in FIG. 11 described above.

  If “NO” is determined in the step 66, the process proceeds to the next step 67 to set the damping force to be hard. If "YES" is determined in the step 75, the damping force is set to be soft.

Further, if it is determined "NO" in step 75, control for gradually increasing a damping force command signal I then proceeds to the next step 76 from the hard command signal I _H until it reaches the soft command signal I _S is executed.

  Here, FIG. 14 shows a comparison of wheel load, relative acceleration, relative speed, and damping force command when the damping force is softly fixed, when the hardware is fixed, and when the wheel is controlled to reduce the wheel load. Data are shown. A characteristic line 71 indicated by a solid line in FIG. 14 indicates a characteristic of the wheel load in an extension stroke and a contraction stroke on the wheel side where it is desired to reduce the wheel load according to the second embodiment, and a characteristic line 72 indicated by an alternate long and short dash line indicates attenuation. The wheel load characteristic when the force is fixed softly is shown, and the characteristic line 73 shown by a two-dot chain line shows the wheel load characteristic when the damping force is fixed hard.

  In addition, a characteristic line 74 indicated by a solid line in FIG. 14 indicates the characteristic of relative acceleration according to the second embodiment, and a characteristic line 75 indicated by an alternate long and short dash line indicates an acceleration characteristic when the damping force is fixed softly. A characteristic line 76 indicated by a two-dot chain line indicates an acceleration characteristic when the damping force is fixed to hardware. Further, a characteristic line 77 shown by a solid line in FIG. 14 shows the characteristic of the damper relative speed according to the second embodiment, and a characteristic line 78 shown by a one-dot chain line shows the characteristic of speed when the damping force is fixed softly. A characteristic line 79 indicated by a two-dot chain line indicates a speed characteristic when the damping force is fixed to hardware.

The relative speed is a positive value during the time Tb1 to Tb2, and the relative acceleration is also a positive value. Therefore, during this time by the process of step 61,65,75,76 in FIG. 13, the control that increases gradually until it reaches the soft command signal _{I S} is performed a damping force command signal I from the hard command signal _{I H.}

  Then, the relative speed is a positive value during the time Tb2 to Tb3 in FIG. 14, and the relative acceleration is a negative value. Then, the damping force is set to be soft by the processing of steps 75 and 77 in FIG.

Next, during the period from time Tb3 to Tb4, the relative speed is a negative value, and the relative acceleration is also a negative value. Therefore, the process of step 65,66,69 in Figure 13, gradually decreases the control until a hard command signal I _H is performed a damping force command signal I from the soft command signal I _S.

  Further, after time Tb4 in FIG. 14, the relative speed becomes a negative value, and the relative acceleration becomes a positive value. Then, the damping force is set to be hard by the processing of steps 66 and 67 in FIG.

  Thus, even in the second embodiment configured as described above, the damper control of the wheel for which the wheel load is to be increased or decreased, as shown in FIGS. By switching the damping force characteristics in the later stages, both hard and soft characteristics are achieved with respect to the responsiveness and maximum amount of wheel load increase and the responsiveness and maximum amount of wheel load loss.

  However, in the first embodiment, if the wheel for which the wheel load is desired to be increased is controlled, the response and the maximum amount of the wheel load can be controlled. For example, the characteristics of the contraction process shown by the solid line in FIG. If the damping force characteristics are switched suddenly as shown by the line 15, the wheel load may suddenly come off and fluctuate. Further, when the damping force characteristic is suddenly switched as shown by the characteristic line 25 of the extension stroke indicated by a solid line in FIG. 8, the wheel load may be suddenly removed.

  Therefore, in the second embodiment, as shown in FIGS. 11 and 12, the damping force of each damping force variable damper 6, 9 is smoothly switched on the wheel side where it is desired to increase the wheel load. Also, as shown in FIGS. 13 and 14, the damping force of each damping force variable damper 6, 9 is smoothly switched even on the wheel side where it is desired to reduce the wheel load.

  That is, in the wheel contraction process in which the wheel load is to be increased, the initial damping force characteristic is made hard as indicated by the characteristic line 70 shown in FIG. 12, and the signal is gradually increased to smoothly switch the damping force. Like the wheel load according to the embodiment of the present invention (characteristic line 15 shown in FIG. 7), the wheel load does not come off suddenly, and the responsiveness of the wheel load increase is fixed to hardware (characteristic line 63). The maximum value of the wheel load is made larger than that when the software is fixed (characteristic line 62), and the characteristics of both responsiveness and maximum value are achieved.

  In addition, even in the wheel extension stroke where it is desired to increase the wheel load, the damping force can be switched smoothly from soft to hard so that the wheel load can be increased rapidly as in the wheel load according to the first embodiment (characteristic line 25 shown in FIG. 8). The wheel load omission is reduced as compared with the case of being fixed to soft (characteristic line 62).

  On the other hand, in the extension stroke of the wheel where it is desired to reduce the wheel load, the initial damping force characteristic is made hard as indicated by the characteristic line 80 shown in FIG. 14, and the signal is gradually increased to smoothly switch the damping force. As in the case of the wheel load according to the embodiment of the present invention (characteristic line 35 shown in FIG. 9), the wheel load does not fluctuate abruptly and the response of the wheel load reduction (disconnection) is fixed to hardware (characteristic line 73). And the maximum value of wheel load loss is larger than when softly fixed (characteristic line 72), and the characteristics of both responsiveness and maximum value are achieved.

  Further, in the contraction process of the wheel where it is desired to reduce the wheel load, the first implementation is achieved by softening the initial damping force characteristic as shown by the characteristic line 80 shown in FIG. 14 and smoothly switching the damping force from soft to hard. Thus, the wheel load does not change abruptly as in the case of the wheel load in the form (characteristic line 45 shown in FIG. 10), and the wheel load increase can be reduced as compared with the case where the wheel load is fixed softly (characteristic line 72).

  In the first embodiment, for example, as shown in FIGS. 5 and 6, when the relative acceleration between the sprung and unsprung portions becomes zero and the value is reversed between positive and negative, the damping force variable damper The case where the damping force characteristics of 6 and 9 are switched between hardware and software has been described as an example. However, the present invention is not limited to this. For example, when the relative speed between the sprung and unsprung parts becomes maximum in the extension stroke and the contraction stroke (maximum in the minus direction in the contraction stroke), the damping force characteristic is hard. It is good also as a structure switched between software.

  In the first embodiment, the case where the relative acceleration and the relative velocity are obtained by calculation using the sprung acceleration sensor 10 and the unsprung acceleration sensor 11 has been described as an example. However, the present invention is not limited to this. For example, the relative acceleration and the relative speed may be obtained by calculation using a signal from a vehicle height sensor that detects the height of the vehicle body 1. This is the same for the second embodiment.

  In the above embodiment, the determination of the stroke and the determination of the damping force characteristic switching time are performed based on the relative speed and the relative acceleration. Displacement, jerk, damping force, etc. can also be used.

Next, the invention included in the above embodiment will be described. That is, the present invention, the wheel load increases during the compression stroke control, in at least one of the control of the extension stroke control at the time of increasing the wheel load, the damping force characteristics of the damping force adjustable shock absorber, late from the initial The characteristic is gradually switched over.

  As a result, the control for switching the damping force characteristic between hardware and software can be performed smoothly, and fluctuations due to a sudden drop or a sudden increase in wheel load can be suppressed.

  According to the present invention, the damping force characteristic is switched when the acceleration of the expansion or contraction of the damping force adjusting shock absorber becomes zero. Thereby, when the relative acceleration between the sprung and unsprung parts becomes zero and the value is reversed between positive and negative, the damping force characteristic of the damping force adjusting shock absorber can be switched between hardware and software. .

  In addition, the switching of the damping force characteristic is performed when the speed of expansion or contraction of the damping force adjusting buffer is maximized. As a result, the damping force characteristics of the damping force adjustable shock absorber can be switched between hard and soft when the relative speed between the sprung and unsprung springs is increased or decreased to a maximum value. Can do.

  Furthermore, a braking force is applied to the wheel that increases the wheel load among the plurality of wheels. As a result, it is possible to suppress the change in the posture of the vehicle accompanying the braking operation by the brake and improve the running stability.

DESCRIPTION OF SYMBOLS 1 Car body 2 Front wheel 3 Rear wheel 4,7 Suspension device 5,8 Spring 6,9 Damping force variable damper (damping force adjustment type shock absorber)
DESCRIPTION OF SYMBOLS 10 Sprung acceleration sensor 11 Unsprung acceleration sensor 12 Braking apparatus 12A Wheel cylinder hydraulic pressure sensor (braking wheel detection means)
13 vehicle stability control device 13A brake fluid pressure control device (braking force control means)
14 Controller (control means)

Claims (5)

A damping force adjustable shock absorber interposed between the vehicle body and the wheel of the vehicle, the damping force characteristic being adjustable between soft and hard;
And a control means for variably controlling the damping force characteristic of the damping force adjusting shock absorber,
A suspension control device used in a vehicle provided with a vehicle stability control device for controlling the braking force of the vehicle to stably control the vehicle,
The control means includes
A wheel that changes the damping force characteristic of the damping force adjusting type shock absorber of the wheel to which the braking force is applied by a signal for controlling the braking force of the wheel from the initial stage during the contracting stroke to the hard side and to the later stage to the soft side. Shrinkage stroke control when load increases,
A wheel that changes the damping force characteristic of the damping force adjusting type shock absorber of the wheel to which the braking force is applied by a signal for controlling the braking force of the wheel to the soft side at the initial stage during the extension stroke and to the hard side at the later stage. Elongation process control when load increases ,
Suspension control apparatus and to execute the control of at least hand of. The wheel load increases during the compression stroke control, in at least one of the control of the extension stroke control at the time of increasing the wheel load, the damping force characteristics of the damping force adjustable shock absorber is gradually characteristics over late from the initial The suspension control device according to claim 1, wherein the suspension control device is configured to be switched.   The suspension control device according to claim 1 or 2, wherein switching of the damping force characteristic is performed when an acceleration of expansion or contraction of the damping force adjustment type shock absorber becomes zero.   4. The suspension control device according to claim 1, wherein the switching of the damping force characteristic is performed when an extension or contraction speed of the damping force adjusting buffer is maximized. 5. A damping force adjustable shock absorber interposed between the vehicle body and the wheel of the vehicle, the damping force characteristic being adjustable between soft and hard;
Control means for variably controlling the damping force characteristic of the damping force adjusting shock absorber;
A braking device provided on each wheel of the vehicle;
Comprising braking force control means for stabilizing the vehicle and controlling the braking force of the braking device,
The control means switches the damping force characteristic of the damping force adjusting type shock absorber of the wheel to which the braking force is applied by the braking force control means from the initial stage during the contracting stroke to the hard side and to the later stage to the soft side. It is characterized by executing at least one of a shrinkage stroke control when the wheel load is increased or an elongation stroke control when the wheel load is increased so that the initial stage during the extension stroke is set to the soft side and the latter stage is switched to the hard side. Vehicle control device .

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