JPH08258527A - Suspension controller - Google Patents

Abstract

PURPOSE: To save electric power by preventing the loss of synchronism of an actuator in traveling on the bad road, and decreasing the holding current except in traveling on the bad road. CONSTITUTION: A controller 6 judges the irregular state of the traveling road on the basis of the detected signal of an acceleration sensor 5, switches and holds the damping coefficient of a shock absorber 4 by supplying the specified current to a stepping motor provided on the shock absorber 4. When the controller judges that the traveling road is the bad road, it prevents the loss of synchronism by increasing the holding current of the stepping motor for holding the damping coefficient of the shock absorber 4 larger than that in the normal state, on the other hand, it judges that the traveling road is not the bad road, it saves electric power by setting the holding current of the stepping motor to a smaller value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension control device provided between a vehicle body and an axle, and more particularly to a semi-active suspension control device for continuously changing a damping coefficient according to a vibration state.

[0002]

2. Description of the Related Art As an example of a conventional suspension control device, there is a suspension control device disclosed in Japanese Unexamined Patent Publication No. 5-330325. This suspension controller
A damping coefficient variable shock absorber, which is interposed between the vehicle body and the axle, adjusts the damping coefficient by displacing the damping coefficient adjusting body to change the passage area of the oil passage, and is connected to the damping coefficient adjusting body. It has a stepping motor having a rotor, and control means for rotating the rotor of the stepping motor to displace the damping coefficient adjusting body and controlling its position.

As an example of control for adjusting the damping coefficient, a plurality of stator coils provided in the stepping motor are sequentially switched to be energized to rotate the rotor to control the position of the damping coefficient adjusting body. However, there is one in which one or more of the plurality of stator coils are energized by PWM (pulse width modulation) to hold the rotor at a stop position. The current control by PWM energization when holding the rotor in the stop position was performed by supplying a pulse signal with a constant duty ratio to the stepping motor.

[0004]

However, in the above-mentioned prior art, the pulse signal having a constant duty ratio is supplied to the stepping motor to keep the rotor at the stop position regardless of the condition of the road. Especially, there is a possibility that the stepping motor may get out of step during traveling on a rough road or at a high speed (hereinafter, referred to as traveling on a rough road). That is, when traveling on rough roads, oil frequently passes through the oil passage in the variable damping coefficient type shock absorber with a large pressure. In this case, the damping area adjustment is performed by changing the passage area to adjust the damping coefficient. A large force acts on the body. Therefore, there is a problem that the load for displacing the damping coefficient adjusting body becomes excessive during traveling on a bad road and the stepping motor loses synchronization. Then, in order to prevent step-out of the stepping motor, it is conceivable to increase the holding current supplied to the stator coil, but in this case, there were problems such as the stepping motor generating heat and increasing the power consumption.

The present invention has been made in view of the above circumstances, and sets the holding current of the stepping motor according to the situation of the traveling road to prevent the stepping motor from being out of step during traveling on a bad road and to An object of the present invention is to provide a suspension control device capable of reducing the holding current of a stepping motor to save power when the vehicle is not traveling on a road or the like.

[0006]

In order to achieve the above object, a suspension control device according to the present invention is provided between a vehicle body and an axle and has a variable damping coefficient type shock absorber having a variable damping coefficient. , A stepping motor for switching the damping coefficient of the shock absorber by rotating the rotor, a vertical vibration detecting means for detecting the vertical vibration of the vehicle body, and an absolute vertical speed from the vertical vibration detected by the vertical vibration detecting means. And a controller that optimally controls the damping coefficient of the shock absorber for vehicle damping by energizing a stepping motor and rotating the rotor or holding the rotor at that position based on the vertical absolute speed. The controller determines the magnitude of the holding current of the stepping motor and the determination means for determining the road surface condition during traveling. And it is characterized in that it has a holding current setting means for setting in response to surface conditions.

[0007]

With the above arrangement, the controller applies the predetermined current to the stepping motor to switch it to the predetermined damping coefficient based on the vertical vibration detected by the vertical vibration detecting means to switch the damping coefficient of the shock absorber to the vehicle damping. In addition to optimal control, the unevenness of the road surface on which the vehicle is running is determined by a predetermined calculation, and the magnitude of the holding current of the stepping motor is set according to the determination result. When it is determined that the vehicle is running on a rough road, the stepping motor holding current is set to a large value to prevent stepping of the stepping motor. It can be set to save power.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the suspension control device according to the present invention will be described below with reference to the drawings. In FIG. 1, a spring 3 and an extension / contraction reversal type are provided between a vehicle body 1 (on a spring) and four wheels (only one is shown in the figure) 2 that form a vehicle. Variable damping coefficient shock absorber 4
Are installed in parallel and support the vehicle body 1. An acceleration sensor 5 that detects vertical acceleration of the vehicle body 1 is mounted on the vehicle body 1 as vibration detection means for detecting vertical vibration of the vehicle body 1. The acceleration signal of the acceleration sensor 5 is supplied to the controller 6. In addition,
Although four damping coefficient variable type shock absorbers 4 and four springs 3 are provided for each of the four wheels 2, only one of them is shown for convenience.

The variable damping coefficient type shock absorber 4 is
As shown in FIG. 2, the free piston 12 is slidably housed in the cylinder 11, and the free piston 12 allows the gas chamber to move.
It is divided into two chambers, 13 and 14. The gas chamber 13 is filled with high-pressure gas, and the oil chamber 14 is filled with oil liquid. A piston 15 is slidably accommodated in the oil chamber 14. The oil chamber 14 is defined by a piston 15 into a lower chamber R ₁ and an upper chamber R ₂ . A piston rod 16 is connected to the piston 15. The piston rod 16 passes through the upper chamber R ₂ and
11 extends out.

The piston 15 is formed with first and second communication passages 17 and 18 for communicating the lower chamber R ₁ and the upper chamber R ₂ , respectively. A normally closed first damping valve 19 is attached to the upper portion of the piston 15. The first damping valve 19 is a piston rod
Opening differential pressure of the upper chamber R ₂ becomes high pressure in the lower chamber R ₁ in 16 shortening reaches a predetermined value, thereby the lower chamber through the first communication path 17 R ₁ and the upper chamber R ₂ I am trying to communicate with. A normally closed second damping valve 20 is attached to the lower portion of the piston 15. The second damping valve 20 is a piston rod
When 16 is extended, the pressure in the upper chamber R ₂ increases and the lower chamber R ₁ and the upper chamber R ₂
The pressure difference is so attained the communication between the lower chamber R ₁ and the upper chamber R ₂ through the opening and a predetermined value, whereby the second communication passage 18 of the. The piston 15 is formed with third and fourth communication passages 21 and 22 that face each other with the axis of the piston rod 16 in between. The third and fourth communication passages 21 and 22 are respectively upper chambers.
It communicates with R ₂ and lower chamber R ₁ .

Check valves 23 and 24 are provided in the third and fourth communication passages 21 and 22, respectively. The check valve 23 allows only the flow of oil liquid from the lower chamber R ₁ to the upper chamber R ₂ , and the check valve 24 allows only the flow of oil liquid from the upper chamber R ₂ to the lower chamber R ₁ . A disk-shaped movable plate (damping coefficient adjusting body) 25 is rotatably held inside the piston 15 about the axis of the piston rod 16, and the plate surfaces of the movable plate 25 are third and fourth. Across the communication passages 21 and 22, respectively. As shown in FIG. 3, the movable plate 25 has a pair of elongated holes 2 extending in an arc shape along the circumferential direction.
6 and 27 are formed. The long holes 26 and 27 are formed concentrically with the center of the movable plate 25 so as to face each other. Long hole 26
3 has a smaller opening area in the direction of arrow R in FIG. 3, and the elongated hole 27 has a larger opening area in the direction of arrow R.

When the movable plate 25 is rotated in the direction of the arrow R or the arrow L, the portions of the elongated holes 26 and 27 facing the third and fourth communication passages 21 and 22 are continuously changed to the third and fourth portions. The opening areas of the communication passages 21 and 22 gradually increase or decrease, whereby the variable damping coefficient shock absorber 4 can obtain the damping characteristics shown by the solid line in FIG.

In FIG. 2, 28 is a piston rod.
The lower end of the movable plate 25
Is an operation rod connected to. A stepping motor 29 for rotating the movable plate 25 in the arrow R direction or the arrow L direction in FIG. 3 is connected to the upper end portion of the operating rod 28 via the operating rod 28. This stepping motor 29
Magnet rotor (rotor) 29 connected to operating rod 28
a and a plurality of magnets located at a predetermined interval around the magnet rotor 29a (four for convenience of explanation, but actually 15 °
It is provided at intervals. ) Protrusion M ₁ , M ₂ , M ₃ , M
A stator 29b having ₄ and the protrusions M ₁ , M ₂ , M ₃ ,
A phase, B phase, A'phase, B'wound around each of M ₄
Phase excitation coil (stator coil) L ₁ , L ₂ , L ₃ , L
₄ and, as shown in FIG. 5, exciting coils L ₁ , L
₂ , L ₃ and L ₄ are connected to the power supply 41 via transistors T ₁ , T ₂ , T ₃ and T ₄ connected to the controller 6. This stepping motor 29 includes an exciting coil L ₁ ,
L _2, L _3, by being sequentially switched in energizing the L _4, and rotates by one step angle.

Next, the third and fourth communication passages of the long holes 26 and 27.
The relationship between the parts facing 21 and 22 (a2 to b2 to c2, a1 to b1 to c1) and the damping coefficient will be described. Here, the positions of the elongated holes 26, 27 facing the third and fourth communication passages 21, 22 are represented by the rotation angle θ of the movable plate 25. When the positions b2 and b1 which are the centers of the long holes 26 and 27 face the third and fourth communication passages 21 and 22, this position is set as the reference position (θ = 0) of the movable plate 25.

When the movable plate 25 is rotated from the reference position in the direction of arrow R, that is, when the movable plate 25 is rotated in the forward direction (θ> 0), the position a2 of the slot 26 faces the third communication passage 21. , And long hole
The position a1 of 27 faces the fourth communication passage 22. This allows the lower chamber
The oil liquid easily flows from R ₁ to the upper chamber R _2, and it becomes difficult for the oil liquid to flow from the upper chamber R ₂ to the lower chamber R ₁ , so that the expansion-side damping coefficient is large and the contraction-side damping coefficient is small.

When the movable plate 25 is rotated in the direction of arrow L from the reference position, that is, when the movable plate 25 is rotated in the negative direction (θ <0), the position c2 of the elongated hole 26 faces the third communication passage 21. , And long hole
The position c1 of 27 faces the fourth communication passage 22. This allows the lower chamber
The oil liquid hardly flows from R ₁ to the upper chamber R _2, and the oil liquid easily flows from the upper chamber R ₂ to the lower chamber R ₁ , so that the expansion-side damping coefficient is small and the contraction-side damping coefficient is large.

As shown in FIG. 5, the controller 6 is roughly composed of a calculation section 42 having a storage section, a theoretical circuit section 43, and a PWM signal output section 44. The logic circuit section 43 has first to fourth AND circuits P ₁ , P ₂ , P ₃ , P ₄ , and the respective output sides thereof are transistors T ₁ , T ₂ , T 4.
It is connected to the bases of ₃ and T ₄ . The calculation unit 42 uses the A-phase, B-phase, A′-phase, and B′-phase exciting coils L so that the acceleration sensor 5 also obtains a desired damping coefficient based on the acceleration signal α.
_One or two-phase exciting coils are sequentially selected from ₁ , L ₂ , L ₃ , and L ₄ , and the first to fourth AND circuits P ₁ , P ₂ ,
The drive angle signal J of H level is output to the first input terminal IN ₁ of the AND circuit corresponding to the selected exciting coil of P ₃ and P ₄ . If there is a selective output of this control signal J,
On condition that the PWM signal, which will be described later, is at the H level, the corresponding exciting coils L ₁ , L ₂ , L ₃ and L ₄ are sequentially switched to be energized, and the magnet rotor 29a, and hence the movable plate 25 are set to 1 Although it rotates in step angles, selective output of the control signal J is sequentially performed until the magnet rotor 29a reaches a position where a desired damping coefficient can be obtained.

When the magnet rotor 29a is held at the stop position so as not to rotate, the magnet rotor 29a
Exciting coils L ₁ , L ₂ , L corresponding to the stop position of 29a
_3, PWM signal described later by selecting one or two sets of exciting coils of the L ₄ is by PWM current continuously on condition that has become H level, the holding of the magnet rotor 29a is performed.

The PWM signal output section 44 has a second input terminal IN _{2 of the first to} fourth AND circuits P ₁ , P ₂ , P ₃ and P ₄ .
Then, the PWM signal (pulse signal) with the duty ratio set as follows is output. That is, in a normal state where the magnet rotor 29a is held when the road surface on which the vehicle is traveling is a good road,
A PWM signal with a duty ratio for a good road (for example, 50%) is output, and a PWM with a duty ratio for a bad road (for example, 80%) that is larger than the duty ratio for a good road when the traveling road is a bad road.
Output a signal. In addition, as will be described later, the position of the magnet rotor 29a in the control cycles that are forward and backward (the current control cycle and the control cycle before that) is different. That is, when the magnet rotor 29a is rotated, the duty ratio is preferentially applied.
It is designed to output 100% PWM signal.

While the vehicle is traveling, various vibration components due to the roughness of the road surface are transmitted from the wheel 2 to the vehicle body 1 via the spring 3 and the shock absorber 4. When the vibration is transmitted to the vehicle body 1, the acceleration sensor 5 attached to the vehicle body 1 detects the vertical acceleration of the vehicle body. The detected vertical acceleration is sent to the controller 6 in real time.

As shown in the flow chart of FIG. 6, the controller 6 has a function of calculating a target angle θ _t for instructing the shock absorber 4 based on the acceleration signal from the acceleration sensor 5. That is, the controller 6 is supplied with power by starting the engine of the vehicle (step
S11) and initializing the controller (step S12) and determining whether or not the control cycle has been reached (step S12).
S13). In step S13, the control cycle is repeated until it is determined that the control cycle is reached.

When it is determined in step S13 that the control period has been reached, a signal is output to a portion other than the stepping motor 29 such as an indicator (LED) in step S14. Next, the acceleration signal is read from the acceleration sensor 5 (step
S15). Then, based on the read acceleration signal, the road surface condition is judged whether the road surface on which the vehicle is running is a bad road (judgment means, step S16). Based on the determination result of step S16, when the traveling road is determined to be a bad road in step S17, the duty ratio for bad road is stored (step S18). As described above, the duty ratio for bad roads is set to a value larger than the duty ratio for good roads that is normally used, and the holding torque on bad roads is strengthened to prevent step-out. When it is determined that the traveling road is not a bad road, the duty ratio for good road is stored and controlled by the normal holding current (step S19).
). Subsequently, a control calculation is executed (step S20), the acceleration signal from the acceleration sensor 5 is integrated to calculate the vertical absolute speed, and based on this absolute speed, the target angle θ _{t of} the stepping motor instructing the shock absorber is given. Is calculated and the process returns to step S13.

Next, the driving subroutine of the stepping motor will be described with reference to the flowchart shown in FIG. The drive flow of the stepping motor is step S20.
Driving is performed so that the target angle θ _t and the actual angle θ _R calculated by the control calculation execution result performed in step S1 are equal to each other. If the target angle θ _t and the actual angle θ _R are different, the actual angle θ _{t The R} is driven step by step so as to approach the target angle θ _t .

[0024] First, actual angle theta _R stored in the storage unit of the operation unit 42 determines whether or not equal to the target angle theta _t (step S21), and to the target angle theta _t if it is determined that the NO Then, it is determined whether the actual angle θ _R is small or large (step S22). In step S22, NO (that is, the target angle θ _t
<Actual angle θ _R ), the drive angle θ _{m is changed} to the actual angle θ
_The value is made smaller than _R by "1" (step S23). YES in step S22 (that is, target angle θ> actual angle θ _R )
If it is determined that the drive angle θ _m is “1” rather than the actual angle θ _R
Increase the value (step S24).

Based on steps S23 and S24, the movable plate 25
Is output to the stepping motor 29 from the controller 6 by rotating the movable plate 25 for one step by rotating the movable plate 25 by one step angle and the actual angle θ _{R is changed} to the target angle θ. _Get closer to _t . next,
Movable plate 25 is to update the actual angle theta _R of the storage unit sets the driving angle theta corresponds as actual angle theta _R that has rotated by one step angle amount (step S26), the flow returns to step 21.

The process of steps S21 to S26 is repeated until the actual angle theta _R = target angle theta _t, in step S21 YES (i.e. actual angle theta _R = target angle theta
_t )), the holding current is set by PWM-energizing the pulse signal having the duty ratio set in step S18 or step S19 (step S27), and the position is held. Then, in process step S28, the interrupt process for positioning the movable plate 25 at the target angle θ _t is completed. The steps S18, S19 and S27 constitute a holding current setting means. In the above-described embodiment, the road surface determination is performed based on the acceleration signal from the acceleration sensor 5, but the present invention is not limited to this, and a vehicle height sensor is separately provided, and a good road is determined based on vertical vibration detected by the vehicle height sensor. Alternatively, a rough road may be determined, or a radar such as an ultrasonic wave may be provided and the determination may be performed based on a signal from this radar. Although the PWM control is used as the holding current control, the holding current is not limited to this, and the holding current may be controlled by changing the voltage. Further, in the above-described embodiment, an example in which the road surface on which the vehicle is traveling is judged to be a good road and a bad road and the magnitude of the holding current of the stepping motor is set to two levels according to the judgment result has been described.
Without being limited to this, the road surface determination is further subdivided into three stages or more such as good road, parallel road, bad road, etc.,
It is also possible to set the magnitude of the holding current of the stepping motor corresponding to the stage of the road surface determination and select the holding current of the magnitude more accurately according to the road surface determination result.

[0027]

Since the present invention is the suspension control device constructed as described above, the holding current of the stepping motor is set according to the condition of the traveling road, and the holding current is increased when traveling on a rough road. It is possible to prevent out-of-step of the stepping motor and reduce the holding current of the stepping motor to save power when the vehicle is not traveling on a bad road.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a suspension control device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a variable damping coefficient type shock absorber used in the suspension control device.

FIG. 3 is a plan view showing a movable plate 25 assembled to the variable damping coefficient type shock absorber.

FIG. 4 is a diagram showing a relationship between a rotation angle of the movable plate and a damping coefficient.

FIG. 5 is a diagram schematically showing a stepping motor of the suspension control device.

FIG. 6 is a flowchart showing a routine of a controller of the suspension control device.

FIG. 7 is a flowchart showing a stepping motor driving subroutine of the suspension control device.

[Explanation of symbols]

 1 Vehicle Body 2 Wheels 4 Variable Damping Coefficient Shock Absorber 5 Accelerometer 6 Controller 29 Stepping Motor

Claims (1)

[Claims] 1. A shock absorber having a variable damping coefficient, which is interposed between a vehicle body and an axle and has a variable damping coefficient, a stepping motor which switches a damping coefficient of the shock absorber by rotating a rotor, and a vehicle body. Vertical vibration detecting means for detecting vertical vibration of the motor and absolute vertical speed is obtained from the vertical vibration detected by the vertical vibration detecting means, and the stepping motor is energized to rotate the rotor based on the vertical absolute speed. Or a controller for optimally controlling the damping coefficient of the shock absorber for vehicle vibration damping by holding it at that position is provided, wherein the controller is a determination means for determining the road surface condition during traveling, and a holding current of the stepping motor. Suspension characterized by having holding current setting means for setting the magnitude according to the road surface condition ® emission control device.