JP2013116641A - Device for controlling suspension - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change characteristics of a suspension mechanism according to a traveling condition of a vehicle.SOLUTION: The suspension mechanism connects a wheel to a vehicle body using an air suspension having an air spring which has a variable spring constant and a liquid-sealed bush having a variable stiffness. A vehicle state obtaining part 102 obtains an on/off state of an auto-cruise switch 24 or a position of a shift lever 26, as a traveling condition of a vehicle. A setting part 106 sets characteristics of the air suspension and the liquid-sealed bush to the characteristics focusing on driving stability or straight-traveling stability according to the traveling condition of the vehicle.

Description

  The present invention relates to a suspension control device that adjusts characteristics of a suspension mechanism of a vehicle.

  2. Description of the Related Art Conventionally, there is known an air suspension device that controls the vehicle height of a vehicle by compressing air with a compressor and supplying the compressed air to an air spring. In such an air suspension device, the spring constant of the air spring can be controlled by controlling the air pressure inside the air chamber.

  It is also known to adjust suspension characteristics in a vehicle having such an air suspension device in accordance with the state of the vehicle. For example, Patent Document 1 discloses a suspension characteristic control device that prioritizes riding comfort over steering stability during automatic traveling and automatically changes suspension characteristics so that the vehicle posture is stabilized when the occupant moves. It is disclosed. Patent Document 2 discloses an automatic transmission control device that performs suspension deceleration control based on information on a damping force selected by a suspension mode selection unit.

JP 2002-331816 A JP-A-5-215227

  In general, the characteristics required for the suspension mechanism differ depending on the running state of the vehicle. For example, it is desirable to set the characteristic with an emphasis on straight running stability during straight traveling of the vehicle, and it is desirable to set the characteristic with an emphasis on steering stability when steering the vehicle.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a control device for a suspension mechanism that selectively uses characteristics that emphasize steering stability and characteristics that emphasize straight running stability in accordance with the traveling state of the vehicle. It is to provide.

  One aspect of the present invention is an air suspension having an air spring that can change a spring constant, a liquid seal bush that can change rigidity, and a suspension that connects a wheel and a vehicle body via the air suspension and the liquid seal bush. A mechanism, a state acquisition means for acquiring the traveling state of the vehicle, and a setting for setting the air suspension and the liquid seal bush to characteristics that emphasize steering stability or straight-running stability according to the acquired traveling state of the vehicle Means for controlling the suspension.

  According to this aspect, the liquid seal bush that can change the rigidity and the air suspension that can change the spring constant are employed in the suspension mechanism of the vehicle. Therefore, by appropriately changing the spring constant of the air suspension and the rigidity of the liquid seal bush, it is possible to select a characteristic that emphasizes either steering stability or straight running stability according to the driving situation.

  The state acquisition means acquires an on / off state of an auto cruise switch, and the setting means sets the air suspension and the liquid seal bush to characteristics that emphasize steering stability when the auto cruise switch is off, When the switch is on, the air suspension and the liquid seal bush may be set to a characteristic that places importance on straight running stability.

  The state acquisition means acquires whether a shift lever of an automatic transmission is in an automatic mode drive range or a manual mode, and the setting means, when the shift lever is in a drive range, the air suspension and the The liquid seal bush may be set to a characteristic that emphasizes straight running stability, and when the shift lever is in the manual mode, the air suspension and the liquid seal bush may be set to a characteristic that emphasizes steering stability.

  According to the present invention, it is possible to selectively use a characteristic that emphasizes steering stability and a characteristic that emphasizes straight running stability in accordance with the traveling state of the vehicle.

1 is a schematic diagram of a four-wheel vehicle including a suspension control device according to an embodiment of the present invention. It is a functional block diagram which shows the structure of ECU. It is a figure explaining the characteristic of an air suspension. It is a figure explaining the characteristic of a liquid seal bush. It is a figure explaining the vehicle behavior when it is set as the steering stability emphasis setting. It is a figure explaining the vehicle behavior when it is set as the straight-running stability emphasis setting. It is a flowchart at the time of control based on an auto cruise switch. It is a flowchart at the time of control based on a shift lever position.

  FIG. 1 is a schematic diagram of a four-wheel vehicle 10 including a suspension control device according to an embodiment of the present invention. In FIG. 1, the suspension mechanism of the vehicle is shown in a simplified manner for the sake of simplicity of description. However, in an actual vehicle, for example, a knuckle, It is configured by combining with other parts such as a tie rod, upper arm, and lower arm in a known manner.

  An air suspension 16 configured by combining an air spring and an absorber is mounted between the vehicle body of the vehicle 10 and each wheel 14. The air spring is realized by filling compressed air in an air chamber formed so as to surround the absorber. The compressed air in the air chamber acts as a spring and elastically supports the wheel 14 to prevent the impact of the wheel 14 from being directly transmitted to the vehicle body. The absorber generates a damping force between the sprung and unsprung parts of the vehicle. In the present specification, the position of the member supported by the air spring is referred to as “sprung”, and the position of the member not supported by the air spring is referred to as “unsprung”. That is, the unsprung portion is on the vehicle body side, and the unsprung portion is on the wheel 14 side. Since such an air suspension is well known, detailed description thereof is omitted in this specification.

  The hub of the wheel 14 is attached to the vehicle body via an upper arm and a lower arm (not shown). As will be described later with reference to FIGS. 7 and 8, the vehicle body side of the lower arm is divided into two forks, and is connected to the vehicle body via a bush. In the present embodiment, the liquid seal bush 20 is adopted as the rear bush among the two bushes.

  The liquid seal bush 20 is a bush type liquid seal vibration isolator that exhibits a vibration isolation function based on the flow of the sealed fluid against vibrations input in the central axis direction and in a direction orthogonal to the central axis line. The liquid sealing bush 20 has a plurality of fluid chambers as an example, and has a structure that can change the rigidity of the liquid sealing bush by adjusting the pressure of the fluid flowing into the fluid chamber. The structure of such a liquid seal bush is well known to those skilled in the art as disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-120760, Japanese Patent Application Laid-Open No. 2011-38612, and the like. Is omitted.

  The pressure adjustment valve 22 is a valve for adjusting the pressure of the fluid in the liquid seal bush 20 to change the rigidity, and is electrically connected to the electronic control unit 100 (hereinafter referred to as “ECU 100”). .

  The vehicle body is provided with a compressor (not shown) for supplying compressed air to the air supply line 40 and a high-pressure tank 30 capable of storing the compressed air supplied from the compressor. The high-pressure tank 30 is maintained at 700 to 800 kPa, for example, by sending compressed air from the compressor.

  The air chamber of the air suspension 16 communicates with the air supply line 40. In the middle of the air supply line 40, air pressure control valves 32 are provided corresponding to the respective wheels 14. The pneumatic control valve 32 is electrically connected to the ECU 100 and is switched between a valve open state and a valve closed state in accordance with a signal from the ECU 100. As a result, air can be supplied from the high-pressure tank 30 to the inside of the air chamber via the air supply line 40, and air can be discharged from the inside. In this way, the spring constant of the air spring of the air suspension 16 can be changed.

  The vehicle 10 has a front wheel as a steering wheel and an electric power steering mechanism (not shown). The electric power steering mechanism detects the steering angle of the steering shaft 35 with the steering angle sensor 28, and assists the steering force with a motor (not shown). Since the electric power steering mechanism is well known, detailed description thereof is omitted in this specification.

  The vehicle 10 is equipped with an auto-cruise function that controls the opening of the engine throttle so that a preset speed is maintained even if the driver does not continue to step on the accelerator pedal. An auto cruise switch 24 for instructing the ECU 100 whether or not to execute the auto cruise function is provided in the passenger compartment.

  A shift lever 26 of an automatic transmission is provided in the vehicle interior. In this embodiment, the automatic mode and the manual mode can be switched by the shift lever 26. The position information of the shift lever 26 is given to the ECU 100.

  The ECU 100 sets the air suspension 16 and the liquid seal bush 20 to either a straight-running stability-oriented characteristic or a steering stability-oriented characteristic based on the traveling state of the vehicle. More specifically, the ECU 100 emphasizes straight-running stability-oriented characteristics or steering stability-oriented characteristics based on whether the auto-cruise switch 24 is on or off, or whether the shift lever 26 is in the automatic mode drive range or the manual mode. Any one of the characteristics is selected, and the air suspension 16 and the liquid seal bush 20 are set to predetermined characteristics.

  In general, when improving the steering stability of a vehicle, the suspension characteristics are set to increase lateral force compliance and roll steer understeer. In order to increase the lateral force compliance, the lateral rigidity of the rear side arm bush may be lowered, and in order to increase the roll steer, the spring constant of the air suspension may be increased. However, if the suspension is made to have characteristics that emphasize steering stability, there is a problem that the straight running stability is deteriorated due to, for example, an increase in the steering angle when subjected to road surface disturbance. As described above, in general, steering stability and straight-line stability are contradictory characteristics, and it is difficult to set a suspension characteristic that satisfies both of them with a suspension mechanism that uses a normal coil spring or bush that does not have an adjustment function. .

  Therefore, in the present embodiment, an air suspension with a variable spring constant and a liquid seal bush with a variable rigidity are employed in the suspension mechanism, and emphasis is placed on either steering stability or straight running stability depending on the state of the vehicle. Provided is a suspension control device which can be changed in characteristics.

  FIG. 2 is a functional block diagram showing the configuration of the ECU 100. Each block shown here can be realized in hardware by an element and a mechanical device including a computer CPU and memory, and in software by a computer program or the like. It is drawn as a functional block to be realized. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms by a combination of hardware and software.

  The vehicle state acquisition unit 102 acquires on / off information of the auto cruise switch 24 and position information of the shift lever 26. The steering input acquisition unit 104 acquires the steering angle of the steering wheel from the steering angle sensor 28.

  Based on the information acquired by the vehicle state acquisition unit 102 and the steering input acquisition unit 104, the setting unit 106 selects either a straight-running stability-oriented characteristic or a steering stability-oriented characteristic. Then, the air pressure control valve 32 and the pressure adjustment valve 22 are controlled so that the spring constant of the air suspension 16 and the rigidity of the liquid seal bush 20 have predetermined values according to the selected characteristics.

  FIG. 3 is a diagram for explaining the characteristics of the air suspension 16. In the figure, the vertical axis represents the input load from the road surface, and the horizontal axis represents the suspension stroke with respect to the input load. The solid line represents the characteristics when the spring constant of the air suspension 16 is lowered (characteristics that emphasize straight running stability), and the dotted line represents the characteristics when the spring constant of the air suspension 16 is increased (characteristics that emphasize steering stability). Represent.

  As can be seen from FIG. 3, for the same input load, the suspension stroke amount increases with respect to the steering stability-oriented characteristic than with the straight-running stability-oriented characteristic. Since the suspension stroke amount and the steering angle are in a proportional relationship, the roll steer increases as the stroke amount increases.

  FIG. 4 is a diagram for explaining the characteristics of the liquid seal bush 20. In the figure, the vertical axis represents the input load from the road surface, and the horizontal axis represents the amount of deflection of the liquid seal bush 20. The solid line represents the characteristic when the rigidity of the liquid seal bush 20 is lowered (characteristic focusing on straight running stability), and the dotted line is the characteristic when the rigidity of the liquid seal bush 20 is increased (characteristic emphasizing steering stability). Represent.

  As can be seen from FIG. 4, for the same input load, the amount of bending of the bush (displacement amount) is greater in the characteristic that emphasizes steering stability than in the characteristic that emphasizes straight running stability. Will increase.

  Next, changes in vehicle behavior due to changes in the characteristics of the air suspension 16 and the liquid seal bush 20 will be described.

  FIG. 5 is a conceptual diagram illustrating the vehicle behavior when the steering stability is emphasized. FIG. 5 schematically shows the right wheel 56 when the vehicle is viewed in plan. The hub of the right wheel 56 is connected to the lower arm 54, and the bifurcated tip of the lower arm 54 is connected to the vehicle body via the front arm bush 52 and the rear arm bush 20. In this embodiment, the front arm bush 52 is a normal bush, and the rear arm bush 20 is a liquid seal bush. Therefore, the lateral rigidity of the rear side arm bush 20 can be adjusted.

  When setting the steering stability as important, the setting unit 106 sets the spring constant of the air suspension 16 to a relatively high predetermined value (as compared with the case where the straightness is emphasized). In addition, the setting unit 106 sets the lateral rigidity of the liquid seal bush 20 to a relatively small value (as compared with the case where the straight running stability is emphasized). As a result, as shown in FIG. 5, the lateral force compliance of the vehicle body and the understeer of the roll steer are increased, so that the steering stability of the vehicle is improved.

  FIG. 6 is a conceptual diagram for explaining the vehicle behavior when the straight-running stability is emphasized. As in FIG. 5, the front arm bush 52 is a normal bush, and the rear arm bush 20 is a liquid seal bush.

  When setting the emphasis on straight running stability, the setting unit 106 sets the lateral rigidity of the liquid seal bush 20 on the rear side to a predetermined value that is relatively higher (than when emphasizing steering stability). Thereby, the displacement amount A of the rear side arm bush 20 with respect to the input load becomes smaller than that in the case of FIG. 7, and therefore the lateral force compliance is reduced. In addition, the setting unit 106 sets the spring constant of the air suspension 16 to a relatively low predetermined value (as compared with a case where steering stability is important). By reducing the spring constant, the roll steer of the vehicle is also reduced.

  Subsequently, a flowchart of the suspension control device according to the present embodiment will be described. In the present embodiment, the suspension control device switches suspension characteristics based on either the auto cruise switch or the shift lever position.

  FIG. 7 is a flowchart at the time of control based on the auto cruise switch. This flow is repeatedly executed at predetermined intervals by the ECU 100 while the vehicle is traveling.

  At the time of control based on the auto cruise switch, the spring constant of the air suspension 16 and the rigidity of the liquid seal bush 20 are set to predetermined values which are characteristics that emphasize steering stability as an initial state. First, the vehicle state acquisition unit 102 determines whether the auto cruise switch 24 is on / off (S10). When the auto cruise switch is turned on (Y in S10), the steering input acquisition unit 104 determines whether the steering input is equal to or less than a predetermined threshold (S12). When the steering input is equal to or less than the predetermined threshold value (Y in S12), it is determined that the vehicle is traveling straight ahead, and the setting unit 106 sets the air suspension 16 to emphasize the straight traveling stability (or ride comfort). In addition, the liquid seal bush 20 is set to a characteristic that emphasizes straight running stability (S16). When the auto-cruise switch is turned off again (N in S10), the air suspension 16 and the liquid seal bush 20 are returned to characteristics that emphasize steering stability (S14). If the steering input is greater than the predetermined threshold value in S12 (N in S12), it is determined that the vehicle is not traveling straight, and the air suspension 16 and the liquid seal bush 20 are left with characteristics that emphasize steering stability (S14).

  According to the above flow, only when the auto cruise switch is on and the vehicle is traveling straight ahead, the air suspension and the liquid seal bush are set so as to emphasize straight travel.

  FIG. 8 is a flowchart at the time of control based on the shift lever position. This flow is repeatedly executed at predetermined intervals by the ECU 100 while the vehicle is traveling.

  At the time of control based on the shift lever position, as an initial state, the spring constant of the air suspension 16 and the rigidity of the liquid seal bush 20 are set to predetermined values that are characteristics that emphasize straight running stability. First, the vehicle state acquisition unit 102 determines whether the shift lever position is in the manual mode or the automatic mode drive range (S20). If it is in the manual mode, it is determined that the driver intends to perform aggressive maneuvering. Therefore, the setting unit 106 sets the air suspension 16 and the liquid seal bush 20 to characteristics that emphasize maneuvering stability (S24). When the shift lever position is returned to the automatic mode drive range again, the air suspension 16 and the liquid seal bush 20 are returned to the characteristics that place importance on straight running stability (S22).

  Only when it is determined that the shift lever position is in the manual mode and the driver intends to perform aggressive maneuvering according to the above flow, the air suspension and the liquid seal bushing are set to emphasize maneuvering stability.

  As described above, according to the present embodiment, it is possible to selectively use the characteristics that place importance on steering stability and the characteristics that place importance on straight running stability in accordance with the traveling state of the vehicle.

  In the normal bush structure, the rigidity is constant, and in the normal coil spring, the spring constant is constant. Therefore, it is difficult to achieve both the steering stability and the straight running stability of the suspension structure. On the other hand, in the present embodiment, a liquid seal bush whose rigidity can be changed is adopted as a rear arm bush, and an air suspension whose spring constant can be changed is adopted. Therefore, by appropriately changing the spring constant of the air suspension and the rigidity of the bush, it is possible to select a characteristic that emphasizes either the steering stability or the straight running stability according to the traveling situation.

  The present invention has been described based on the embodiments. These embodiments are merely examples, and modifications such as any combination of the embodiments, each component of the embodiment, and any combination of each processing process are also within the scope of the present invention. It will be understood by those skilled in the art.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. The configuration shown in each drawing is for explaining an example, and can be appropriately changed as long as the configuration can achieve the same function.

  In the embodiment, the liquid seal bush is used for the rear arm bush. However, the liquid seal bush may be used for the front arm bush.

  In the embodiment, it has been described that the suspension characteristics of all the front and rear wheels of the vehicle are controlled. However, the suspension characteristics of one of the front wheels and the rear wheels may be controlled.

  DESCRIPTION OF SYMBOLS 10 Vehicle, 14 Wheel, 16 Air suspension, 20 Liquid seal bush, 22 Pressure adjustment valve, 24 Auto cruise switch, 26 Shift lever, 28 Steering angle sensor, 32 Pneumatic control valve, 100 ECU, 102 Vehicle state acquisition part, 104 Steering An input acquisition unit, 106 a setting unit.

Claims (5)

An air suspension having an air spring capable of changing a spring constant;
A liquid-sealed bush with variable stiffness,
A suspension mechanism for connecting a wheel and a vehicle body using the air suspension and the liquid seal bush;
State acquisition means for acquiring the traveling state of the vehicle;
Setting means for setting the air suspension and the liquid seal bush to characteristics that emphasize steering stability or straight-running stability according to the acquired traveling state of the vehicle;
A suspension control device comprising: The state acquisition means acquires an on / off state of the auto cruise switch,
The setting means sets the air suspension and the liquid seal bush to characteristics that emphasize steering stability when the auto cruise switch is off, and sets the air suspension and the liquid seal bush when the auto cruise switch is on. The suspension control device according to claim 1, wherein the characteristic is set so as to emphasize straight running stability. The state acquisition means acquires whether the shift lever of the automatic transmission is in the automatic mode drive range or the manual mode,
The setting means sets the air suspension and the liquid seal bush to a characteristic that emphasizes straight running stability when the shift lever is in a drive range, and sets the air suspension and the liquid when the shift lever is in a manual mode. The suspension control device according to claim 1, wherein the sealing bush is set to a characteristic that emphasizes steering stability.   4. The air suspension according to any one of claims 1 to 3, wherein the air suspension has a characteristic that emphasizes direct vision stability when the spring constant is reduced, and a characteristic that emphasizes steering stability when the spring constant is increased. The suspension control device described in 1.   5. The liquid seal bushing according to claim 1, wherein the liquid seal bushing is configured to have a characteristic of emphasizing direct vision stability when the rigidity is reduced and a characteristic of emphasizing steering stability when the rigidity is increased. The suspension control device described.

Images