JP4648125B2 - Control device for variable damping force damper - Google Patents

Description

  The present invention relates to a control device for a variable damping force damper provided with control means capable of switching a damping force of a suspension damper for suspending a wheel on a vehicle body to at least two stages of high damping and low damping by operating a damping force changeover switch. .

The damping force of a vehicle damper (shock absorber) can be switched between a high-attenuation state that emphasizes handling and a low-attenuation state that emphasizes riding comfort, thereby achieving both handling and riding comfort. Is known from the following Patent Document 1.
JP-A-4-183625

  By the way, when the damping force of the damper can be switched between high damping and low damping by switch operation, the damping of the damper is performed in a state in which the vehicle body exhibits a roll behavior or a pitch behavior exceeding a predetermined value due to lateral acceleration or longitudinal acceleration acting on the vehicle. When the force is switched, the change in the damping force changes the characteristics of the vehicle behavior, which may cause the driver to feel uncomfortable.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a driver from feeling uncomfortable due to a change in vehicle behavior characteristics when switching a damping force of a variable damping force damper.

In order to achieve the above object, according to the invention described in claim 1, the damping force of the suspension damper for suspending the wheel on the vehicle body is at least in two stages of high damping and low damping by operating the damping force changeover switch. In the control apparatus for a variable damping force damper having switchable control means, the control means includes a vehicle behavior determination unit that determines whether or not the vehicle behavior is in a stable state, and the vehicle behavior determination unit If the damping force changeover switch is operated in the direction in which the vehicle behavior is stable, the damper damping force is switched simultaneously with the operation, but the vehicle behavior is stable. state the damping force change-over switch in direction of easy will not temporarily prohibit the switching of the damping force when being operated, also the vehicle behavior by said vehicle behavior determination unit is stabilized If it is determined it has been restored and the control device of the variable damping force damper, characterized in that for switching the damping force said has been temporarily disabled have been proposed, and in accordance with the invention described in claim 2 In addition to the feature of the invention described in claim 1, the vehicle behavior determination unit includes a lateral acceleration sensor that detects a lateral acceleration of the vehicle and a longitudinal acceleration sensor that detects a longitudinal acceleration of the vehicle. A control device for a variable damping force damper, wherein when at least one of detection values of a lateral acceleration sensor and a longitudinal acceleration sensor exceeds a threshold value, it is determined that the vehicle behavior is not likely to be in a stable state. Is proposed.

  The electronic control unit U of the embodiment corresponds to the control means of the present invention.

According to the present invention, the vehicle behavior determination unit that determines whether or not the vehicle behavior is in a stable state is provided, and when the vehicle behavior determination unit determines that the vehicle behavior is likely to be unstable, the damping force switching is performed. Even if the switch is operated , if the damping force changeover switch is operated in a direction in which the vehicle behavior is stable, the damping force changeover switch is switched at the same time as the operation. When the vehicle is operated, the switching of the damping force is temporarily prohibited, and when the vehicle behavior determining unit determines that the vehicle behavior has returned to a stable state, the temporarily prohibited damping force is changed. Since the switching is performed, the switching timing of the damping force from when the damping force changeover switch is operated until the damper damping force changes depends on the vehicle behavior when the damping force changeover switch is operated. This makes it possible to prevent the damper's damping force from changing when strong lateral acceleration or strong longitudinal acceleration is applied to the vehicle. This can prevent the driver from feeling uncomfortable.

  Embodiments of the present invention will be described below based on the embodiments of the present invention shown in the accompanying drawings.

  1 to 9 show an embodiment of the present invention. FIG. 1 is a front view of a vehicle suspension apparatus, FIG. 2 is a block diagram of an actuator control system for changing a damping force of a damper, and FIG. 3 is a suspension. FIG. 4 is an explanatory diagram of the skyhook control, FIG. 5 is a flowchart showing the action of the roll attitude control, FIG. 6 is a diagram showing a map for searching for the target current of the actuator, and FIG. 8 is a graph showing the lateral acceleration and the differential value of the lateral acceleration, FIG. 8 is a diagram showing the vehicle behavior when the lane change is performed, and FIG. 9 is a graph showing the vibration transmissibility in the skyhook control.

  As shown in FIG. 1, a suspension S that suspends wheels W of a four-wheel automobile is connected in series so that a suspension arm 3 that supports a knuckle 2 in a vertically movable manner is connected to a vehicle body 1, and the suspension arm 3 and the vehicle body 1 are connected. Are provided with a damper 4, an actuator 5, and a damper mount rubber 6, and a coil spring 7 that connects the suspension arm 3 and the vehicle body 1. The damper 4 includes a cylinder 8 having a lower end supported by the suspension arm 3, a piston 9 slidably fitted into the cylinder 8, and a piston rod 10 extending upward from the piston 9, and the actuator 5 includes a piston It is comprised from the core 11 which connects the upper end of the rod 10, and the lower end of the damper mount rubber 6, and the coil 12 arrange | positioned so that the outer periphery of the core 11 may be enclosed. The damper 4 is a well-known hydraulic type, and generates a load (damping force) corresponding to the moving speed when the piston 9 moves inside the cylinder 8 filled with oil.

  The electronic control unit U that controls the operation of the actuator 5 includes a signal from the sprung acceleration sensor 13 that detects the sprung acceleration, a signal from the damper displacement sensor 14 that detects the displacement (stroke) of the damper 4, and the vehicle. A signal from the lateral acceleration sensor 15 for detecting the lateral acceleration of the vehicle, a signal from the longitudinal acceleration sensor 16 for detecting the longitudinal acceleration of the vehicle, and an attenuation capable of switching the damping force of the damper 4 to two stages of high attenuation and low attenuation. Signals from the force changeover switch 20 are input, and based on these signals, the electronic control unit U can control the current supplied to the damper 4 to arbitrarily change the damping force.

  As shown in FIG. 2, the electronic control unit U includes a skyhook ride control unit M1, a roll posture control unit M2, a pitch posture control unit M3, a target current calculation unit M4, an unsprung control unit M5, A vehicle behavior determination unit M6 and a damping force switching unit M7 are provided. The sprung acceleration output from the sprung acceleration sensor 13 is integrated by the integrating means 21 to become a sprung vertical speed and is input to the skyhook riding comfort control unit M1. The damper displacement output from the damper displacement sensor 14 is directly input to the unsprung control unit M5, and is differentiated by the differentiating means 22 to become the damper speed, and is input to the skyhook riding comfort control unit M1 and the unsprung control unit M5. . The lateral acceleration output from the lateral acceleration sensor 15 is differentiated by the differentiating means 23 to become a lateral acceleration differential value, which is input to the roll posture control unit M2. The longitudinal acceleration output by the longitudinal acceleration sensor 16 is differentiated by the differentiating means 24 to become a longitudinal acceleration differential value, which is input to the pitch attitude control unit M3.

  The damper speed calculated by the differentiating means 22, the roll control target load output by the roll attitude control unit M2 (target damping force to be generated by the damper 4 to perform roll control), and the pitch output by the pitch attitude control unit M3 The target current calculation unit M4 to which the control target load (the target damping force to be generated in the damper 4 to perform pitch control) is input outputs the roll control current and the pitch control current supplied to the actuator 5 of the damper 4. The roll control current and the pitch control current are added by the adding means 25 to become a roll / pitch control current, and input to the high select means 26. In addition to the roll / pitch control current, the high-select means 26, to which the skyhook control current (target current for performing the skyhook control) from the skyhook ride control unit M1, is input, The larger of the hook control currents is output. Then, the high selection value output from the high selection means 26 and the unsprung control current output from the unsprung control unit M5 (target current for performing unsprung control) are added by the adding means 27.

  On the other hand, the vehicle behavior determination unit M6 to which the lateral acceleration detected by the lateral acceleration sensor 15 and the longitudinal acceleration detected by the longitudinal acceleration sensor 16 are input indicates whether the vehicle behavior is stable based on the lateral acceleration and the longitudinal acceleration. Determine whether. For example, when at least one of the lateral acceleration and the longitudinal acceleration exceeds a threshold value, it is determined that the vehicle behavior is not likely to be stable.

  The damping force switching unit M7 to which the target current from the adding means 27 is input switches the target current between a large current corresponding to high damping and a small current corresponding to low damping depending on the state of the damping force switching switch 20. One of them is output to the actuator 5 of the damper 4. In other words, the damping force changeover switch 20 is switched to a high attenuation when the vehicle maneuverability is emphasized, so that the damping force of the damper 4 is set higher. Is switched to low damping, the damping force of the damper 4 can be set low.

  By the way, if the damping force of the damper 4 changes while the vehicle is turning or accelerating / decelerating, the vehicle behavior may be disturbed and the driver may feel uncomfortable. Therefore, in this embodiment, when the vehicle behavior determining unit M6 determines that the vehicle behavior is likely to be unstable, the damping force switching unit M7 temporarily prohibits switching of the damping force even when the damping force switching switch 20 is operated. When the vehicle behavior determination unit M6 determines that the vehicle behavior has returned to a stable state, switching of the prohibited damping force is executed. Thus, since the switching timing of the damping force is changed according to the vehicle behavior determined by the vehicle behavior determination unit M6, the change in the vehicle behavior associated with the switching of the damping force can be prevented and the driver's uncomfortable feeling can be eliminated. .

Even when the vehicle behavior determination unit M6 determines that the vehicle behavior is likely to be unstable, if the damping force switch 20 is operated in a direction in which the vehicle behavior is stabilized, the damping force switch 20 operation of at the same time as Ru switching the damping force of the damper 4.

  Next, the function of the skyhook riding comfort control unit M1 will be described based on FIG. 3 and FIG.

  As is apparent from the suspension model shown in FIG. 3, an unsprung mass 18 is connected to the road surface via a virtual spring 17 of the tire, and the unsprung mass 18 is spring-loaded via the damper 4, the actuator 5 and the coil spring 7. An upper mass 19 is connected. The damping force of the damper 4 is variable by the actuator 5. The rate of change dX2 / dt of the displacement X2 of the sprung mass 19 corresponds to the sprung vertical speed output by the integrating means 21 in FIG. Further, the rate of change d (X2-X1) / dt of the difference between the displacement X2 of the sprung mass 19 and the displacement X1 of the unsprung mass 18 corresponds to the damper speed output by the differentiating means 22 of FIG.

dX2 / dt × d (X2−X1) / dt> 0
In this case, that is, when the sprung vertical speed and the damper speed are in the same direction (same sign), the actuator 5 of the damper 4 is controlled to increase the damping force. on the other hand,
dX2 / dt × d (X2−X1) / dt ≦ 0
In this case, that is, when the sprung vertical speed and the damper speed are in opposite directions (reverse signs), the actuator 5 of the damper 4 is controlled in a direction to decrease the damping force.

  Therefore, considering the case where the wheel W passes over the protrusion on the road surface as shown in FIG. 4, the vehicle body 1 moves upward while the wheel W ascends along the first half of the protrusion as shown in (1). The sprung vertical speed (dX2 / dt) becomes a positive value, the damper 4 is compressed, and the damper speed d (X2-X1) / dt becomes a negative value. Is controlled to reduce the damping force in the compression direction.

  Further, as shown in (2), immediately after the wheel W passes over the top of the protrusion, the vehicle body 1 still moves upward due to inertia and the sprung vertical speed (dX2 / dt) becomes a positive value, and the vehicle body 1 is lifted. As a result, the damper 4 is extended and the damper speed d (X2−X1) / dt becomes a positive value, so that both have the same sign and the actuator 5 of the damper 4 is controlled to increase the damping force in the extension direction. .

  Further, as shown in (3), while the wheel W descends along the latter half of the protrusion, the vehicle body 1 moves downward, the sprung vertical speed (dX2 / dt) becomes a negative value, and the wheel W moves to the vehicle body 1. Since the damper 4 is extended faster and the damper speed d (X2-X1) / dt becomes a positive value, the actuator 5 of the damper 4 reduces the damping force in the extension direction. It is controlled to let you.

  Also, as shown in (4), immediately after the wheel W has completely passed over the protrusion, the vehicle body 1 still moves downward due to inertia, and the sprung vertical speed (dX2 / dt) becomes negative, and the wheel W is lowered. Since the damper 4 is compressed and the damper speed d (X2-X1) / dt becomes a negative value, the actuator 5 of the damper 4 has the same sign so as to increase the damping force in the compression direction. Controlled.

  When performing such skyhook control to increase the riding comfort of the vehicle, the damping force, that is, the sky, is a region where the damping force of the actuator 5 of the damper 4 is increased as shown in (2) and (4) of FIG. By calculating the hook control current by (proportional constant) × (sprung vertical speed), it is possible to reduce the switching sound and the uncomfortable feeling.

  Next, operations of the roll posture control unit M2 and the target current calculation unit M4 will be described with reference to FIGS.

  In step S1 of the flowchart of FIG. 5, the lateral acceleration is detected by the lateral acceleration sensor 15, the lateral acceleration is differentiated by the differentiating means 23 in step S2, and the rate of change in lateral acceleration is calculated. In step S3, the roll posture control unit M2 is calculated. The roll control target load is calculated by (proportional constant) × (lateral acceleration differential value). In step S4, the damper displacement sensor 14 detects the damper displacement, and in step S5, the damper displacement is differentiated by the differentiating means 22 to calculate the damper speed. In subsequent step S6, the target current calculation unit M4 to which the roll control target load and the damper speed are input retrieves the roll control current from the map shown in FIG. 6, and outputs the roll control current to the adding means 25 in step S7. .

  FIG. 6 shows a map for retrieving the roll control current from the roll control target load and the damper speed. The roll control current is basically proportional to the roll control target load on the vertical axis, but the roll control current is corrected by the damper speed. For example, when the roll control target load is Ft and the damper speed is Vpt, the roll control current is It. When the damper speed increases from Vpt to Vpt1, the roll control current decreases from It to It1, and conversely when the damper speed decreases from Vpt to Vpt2, the roll control current increases from It to It2.

  FIG. 7 shows the lateral acceleration when the vehicle is lane-changed from the left lane to the right lane, and the lateral acceleration differential value obtained by differentiating the lateral acceleration. (1) to (5) on the time axis are shown in FIG. This corresponds to (1) to (5) of the behavior of the vehicle that changes lanes.

  In (1), (3), (5) where the lateral acceleration is zero, the vehicle body 1 is not rolled. In (2) during a right turn, the vehicle body 1 rolls to the left by centrifugal force and is turning left. In (4), the vehicle body 1 rolls to the right side due to centrifugal force. At this time, by generating a roll control target load Ft in the damper 4, the roll of the vehicle body 1 to the outside in the turning direction is suppressed and the posture of the vehicle is changed. It can be stabilized.

  At this time, if the roll control target load Ft of the damper 4 is determined based on the lateral acceleration so as to control the roll angle of the vehicle body 1, the lateral acceleration changes in substantially the same phase as the roll angle. There may be a delay in control. When attention is paid to the graph of FIG. 7, the absolute value of the lateral acceleration differential value is maximized at point a prior to the timing at which the leftward lateral acceleration is maximized in (2), and the rightward lateral acceleration is maximized in (4). The absolute value of the lateral acceleration differential value is maximized at point b prior to timing. In this way, focusing on the fact that the phase in which the lateral acceleration differential value changes precedes the phase in which the lateral acceleration changes, the roll control target load Ft of the damper 4 proportional to the lateral acceleration differential value is set. By doing so, the damping force of the damper 4 can be controlled without a time delay to further stabilize the posture of the vehicle, thereby achieving both accurate posture control and riding comfort.

  Moreover, when the target current calculation unit M4 searches for a map of the roll control current from the roll control target load, correction is performed by the damper speed, so even if there is a large input from road surface unevenness, an appropriate roll control target load is set. As a result, it is possible to avoid a deterioration in riding comfort.

  Similarly to the calculation of the roll control current described above, the pitch attitude control unit M3 uses the longitudinal acceleration detected by the longitudinal acceleration sensor 16 to suppress nose up during sudden acceleration of the vehicle and nose down during sudden braking. The pitch control target load is calculated from the longitudinal acceleration differential value obtained by differentiating with the differentiating means 24, and the target current calculation hand M4 calculates the pitch based on the damper speed when searching the map of the pitch control current from the pitch control target load. Correct the control current.

  Thus, the roll control current and the pitch control current output from the target current calculation hand M4 are added by the adding means 25, and the roll / pitch control current as the added value is input to the high select means 26, where the skyhook control is performed. As a result of the comparison with the current, the larger current is output to the adding means 27. Then, the adding means 27 adds the unsprung control current output from the unsprung control unit M5, and the damping force of the actuator 5 of the damper 4 is controlled based on the added value.

  As described above, the higher one of the roll / pitch control current and the skyhook control current is selected by the high-select means 26 and output to the actuator 5, so the high-select means 26 selects the roll / pitch control current. At the moment when the skyhook control current increases and exceeds the roll / pitch control current, the roll / pitch control current is switched to the skyhook control current. On the contrary, the high select means 26 changes the skyhook control current. At the moment when the roll / pitch control current increases and exceeds the skyhook control current during the selection, the skyhook control current is switched to the roll / pitch control current. In any case, since the high-select current output from the high-select means 26 at the time of switching does not change discontinuously, the operation of the actuator 5 of the damper 4 is avoided from giving the driver a sense of incongruity.

  Incidentally, as shown in FIG. 9, in the above-described skyhook control, even if the control gain is changed, only the vibration transmissibility in the vicinity of 1 Hz, which is the sprung resonance frequency, changes, and in the vicinity of 10 Hz, which is the unsprung resonance frequency. There is a problem that the vibration transmissibility of the can not be controlled.

  The unsprung control unit M5 is provided to solve this problem, and pays attention to the product of the damper speed and the damper displacement as an index for grasping and controlling the vibration in the unsprung resonance region. The unsprung control current is calculated by x (damper speed) x (damper displacement), and this unsprung control current is added to the high select current output from the high select means 26 in the adding means 27. As a result, vibration in the unsprung resonance region in the vicinity of 10 Hz can be suppressed independently of the skyhook control, particularly when the damper speed and the damper displacement are large.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, in the embodiment, the damping force changeover switch 20 switches the damping force of the damper 4 to two stages, but it may be switched to three or more stages.

  In the embodiment, the vehicle behavior determination means M6 determines the vehicle behavior based on the lateral acceleration and the longitudinal acceleration. However, in addition to the lateral acceleration and the longitudinal acceleration, any one of the vertical acceleration, the yaw rate, the vehicle speed, and the steering angle is used. The vehicle behavior may be determined.

Front view of vehicle suspension system Block diagram of the actuator control system that changes the damping force of the damper Diagram showing suspension model Illustration of skyhook control Flow chart showing the action of roll posture control The figure which shows the map which searches the target electric current of the actuator Graph showing lateral acceleration and lateral acceleration differential value when performing lane change Diagram showing vehicle behavior when performing a lane change Graph showing vibration transmissibility in skyhook control

DESCRIPTION OF SYMBOLS 1 Car body 4 Damper 15 Lateral acceleration sensor 16 Longitudinal acceleration sensor 20 Damping force changeover switch M6 Vehicle behavior determination part S Suspension U Electronic control unit (control means)
W wheel

Claims (2)

Control means capable of switching the damping force of the damper (4) of the suspension (S) that suspends the wheel (W) from the vehicle body (1) to at least two stages of high damping and low damping by operating the damping force changeover switch (20). (U) In the control device for the variable damping force damper,
The control means (U) includes a vehicle behavior determination unit (M6) that determines whether the vehicle behavior is in a stable state, and the vehicle behavior determination unit (M6) tends to make the vehicle behavior unstable. If the damping force changeover switch (20) is operated in a direction in which the vehicle behavior is stable, the damping force of the damper (4) is switched simultaneously with the operation, but the vehicle behavior becomes unstable. When the damping force changeover switch (20) is operated in an easy direction, the switching of the damping force is temporarily prohibited, and the vehicle behavior determination unit (M6) determines that the vehicle behavior has returned to a stable state. Then, the control device for the variable damping force damper is configured to switch the damping force temporarily prohibited. A lateral acceleration sensor (15) for detecting the lateral acceleration of the vehicle;
A longitudinal acceleration sensor (16) for detecting longitudinal acceleration of the vehicle,
The vehicle behavior determination unit (M6) is not in a stable vehicle behavior when at least one of the detection values of the lateral acceleration sensor (15) and the longitudinal acceleration sensor (16) exceeds a threshold value. 2. The variable damping force damper control device according to claim 1, wherein the control device is determined to be in an easy state.

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