JPH0357529Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention is for a vehicle equipped with a variable spring constant spring device that can change the spring constant in multiple stages and a variable spring constant spring device that can change the damping force. The present invention relates to a suspension control device.

[Conventional technology]

Examples of conventional vehicle suspension control devices include "Service Bulletin No. 516 Bluebird", October 1980, published by Nissan Motor Co., Ltd.
The ones disclosed on pages 6 to 12 are known.

This conventional device uses a coil spring with an integral spring constant and a variable damping force shock absorber that can change the damping force to three levels: soft, medium, and hard.

Another conventional vehicle suspension control device is described in Japanese Patent Laid-Open No. 110311/1983.

This conventional example includes an air spring whose spring constant is variable and a shock absorber whose damping force is variable, and the spring constant of these air springs and the damping force of the shock absorber are controlled by a computer. It is preprogrammed to provide desired ride comfort and operability, and the optimum spring constant and damping force are determined depending on the vehicle's behavior at that time.

[Problem that the invention attempts to solve]

However, in the case of the former conventional device, the spring constant is constant, so if the damping force is set to soft, the damping ratio is too low to suppress vehicle vibrations, and the ride comfort may not be sufficiently suppressed depending on the road surface condition. The problem was that it was difficult to improve.

Furthermore, in the case of the latter conventional device, the optimum spring constant and damping force are simply determined according to the behavior of the vehicle, and the damping ratio determined by the spring constant and damping force is Since it is not taken into account,
It is not possible to satisfy the conflicting requirements of vehicle ride comfort and vibration damping effect at the same time, and there is a problem in that if emphasis is placed on vibration damping effect, ride comfort will be reduced, and if ride comfort is emphasized, vibration damping effect will be reduced. Ta.

This idea was made by focusing on these conventional problems, and it allows for any combination of spring constant and damping force, and also makes it possible to set the damping ratio determined by the spring constant and damping force of the suspension device in that combination. The purpose of the present invention is to provide a vehicle suspension control device that can improve maneuverability and stability by satisfactorily suppressing changes in the vehicle's attitude, as well as improving riding comfort. .

[Means for solving problems]

Therefore, as shown in FIG. 1, the vehicle suspension control device according to this invention includes a variable spring constant spring device that can change the spring constant and a variable damping force shock absorber that can change the damping force. a vehicle state detection means for detecting the state of the vehicle; a spring constant setting means for setting the spring constant to a predetermined value according to the vehicle state detected by the vehicle state detection means; damping force setting means for setting the damping force to a predetermined value according to a detected vehicle state, the spring of the suspension device when both the spring constant and the damping force are set to a minimum value. The damping ratio determined by the constant and damping force is
The damping ratio is set to be the minimum among possible damping ratio values of the suspension device, and the vehicle state detection means detects that the vehicle state is in a predetermined condition for achieving the best ride comfort. Time,
The spring constant setting means and the damping force setting means control the spring constant, damping force, and damping ratio so that they are all at their minimum values.

[Effect]

The function of the vehicle suspension control device according to this invention is to set the spring constant of the variable spring constant spring device to a predetermined level by the spring constant setting means in accordance with the vehicle state detected by the vehicle state detection means. At the same time, the damping force of the variable damping force shock absorber is set to a predetermined level by the damping force setting means, and the combination of spring constant and damping force is appropriately adjusted according to the vehicle condition, thereby improving the maneuverability and stability of the vehicle. Improve riding comfort. In particular, when the vehicle is in a predetermined condition to achieve the best ride comfort, such as when driving straight at low speed on a general road, the spring constant, damping force, and damping ratio are all controlled to their minimum values. Therefore, at this time, the suspension device can exhibit its best ride comfort performance.

〔Example〕

Hereinafter, embodiments of this invention will be described with reference to the drawings.

First, the configuration will be explained.

In FIG. 2, for example, there is a suspension device 2 between the front left wheel 1a and the vehicle body (not shown).
The suspension device 2 includes a suspension member such as a suspension arm 3, a variable spring constant spring device 4, and a variable damping force shock absorber 5. And this spring constant variable spring device 4
The variable damping force shock absorber 5 is mounted on four wheels, front, rear, left and right.

Spring constant variable spring device 4 shown in FIG.
The spring constant can be changed into two stages, soft and hard, and the main air chamber A is formed inside by vertically extending and contracting the space between the vehicle body and the variable damping force shock absorber 5. A rolling diaphragm 7 made of rubber or the like that rolls on the outer periphery of the shell of the variable damping force shock absorber 5 to increase or decrease the volume of the main air chamber A, and a sub-tank 8 that forms a sub-air chamber B with a fixed volume inside. A pipe line 9 that communicates between the main air chamber A and the sub air chamber B, and a pipe line 9 that is installed in the middle of the pipe line 9 to open and close the pipe line 9, thereby communicating the main air chamber A and the sub air chamber B. or a switching valve 10 that can be switched to either a cutoff state or a cutoff state.

When no excitation current is supplied to the switching valve 10, the switching valve 10 is open, and in this case,
The main air chamber A and the auxiliary air chamber B are in communication, and the spring constant is determined by the volume of the main air chamber A and the volume of the auxiliary air chamber B. Therefore, the spring constant becomes soft.

In addition, when a predetermined value of excitation current is supplied to the switching valve 10, the switching valve 10 is closed, and in this case, the main air chamber A and the sub air chamber B are cut off, and the main air chamber A is closed. The spring constant is determined only by the volume, and therefore the spring constant is hard.

Therefore, the spring constant of the variable spring constant spring device 4 is soft when no excitation current is supplied to the switching valve 10, and hard when an excitation current is supplied to the switching valve 10.

FIG. 3 shows an example of a variable damping force shock absorber 5 in which the damping force can be changed to three levels: soft, medium, and hard.

In the figure, the variable damping force shock absorber 5 is of a twin tube type having a double structure of a shell 11 and a tube 12.
The lower end of the piston rod 13 is fixed to the wheel 1 side, while a piston rod 13 formed by connecting an upper rod 14 and a lower rod 15 moves up and down inside the tube 12, and the upper end of the piston rod 13 is fixed to the vehicle body side. A piston 16 that slides along the inner peripheral surface of the tube 12 is fixed to the lower end of the piston rod 13. Inside the tube 12, an upper piston chamber C is provided above the piston 16, and a lower piston chamber is provided below the piston 16. D is formed.

The piston 16 is formed with an extension side orifice 17 and a contraction side orifice 18 which communicate the piston upper chamber C and the piston lower chamber D. The expansion side orifice 17 is connected to the expansion side valve 19 and the contraction side orifice 18 is connected to the contraction side. They are opened and closed by valves 20, respectively.

In the extension stroke, the extension side valve 19 opens, the piston upper chamber C and the piston lower chamber D communicate through the extension side orifice 17, and the compression side valve 2
0, the contraction side orifice 18 is closed.
In addition, in the contraction stroke, the contraction side valve 20 opens, the piston upper chamber C and the piston lower chamber D communicate through the contraction side orifice 18, and the expansion side orifice 17 is closed by the expansion side valve 19. be done.

The upper rod 14 has a hollow cylindrical shape, and a hollow cylindrical body 21 is fixed to the upper part of the lower rod 15 in the lower part of the inside thereof. It is arranged so that it can rotate freely. Furthermore, Atsuparotsudo 1
Above the cylindrical body 21 and shutter 22 in the interior of It is rotatable, and the rotational position of the shutter 22 can be detected by a rotational position sensor 25.

In the vicinity of the shutter 22, the atsparod 1
4 is formed with an opening 27 that communicates the piston upper chamber C with the inside of the top rod 14, and the inside of the shutter 22 has a passage 28 formed in the lower part of the shutter 22 and a passage formed in the lower part of the cylindrical body 21. 29 and a passage 30 formed in the center of the lower rod 15 to communicate with the lower piston chamber D.

Two orifice groups E and F are formed in the cylindrical body 21 in its axial direction (up and down direction in the drawing), the orifice group E is along the a-a line as shown in FIG. 4a, and the orifice group F is It is formed along line bb as shown in FIG. 4b.

In Figures 3 and 4a, orifice group E
The first large orifice 31s has a large opening area at the position Rs, and the first large orifice 31s has a medium opening area at the position Rm.
A medium orifice 31m and a first small orifice 31h having a small opening area at a position Rh are arranged in a plane perpendicular to the axial direction of the cylindrical body 21 at equal intervals of, for example, 120°. An opening 32 is formed in the shutter 22 facing these orifice groups E, and by rotating the shutter 22, the opening 32 is opened.
2 can be placed facing each of the orifices 31s, 31m, and 31h.

In addition, in FIG. 3 and FIG. 4b, the orifice group F includes a second large orifice 33s with a large opening area at position Rs, and a second medium orifice 33m with a medium opening area at position Rm. The second large orifice 33s is located at an interval of, for example, 120° in a plane perpendicular to the axial direction of the cylindrical body 21, and in the axial direction of the cylindrical body 21.
A second medium orifice 33m is arranged to correspond to the large orifice 31s, and a second medium orifice 33m is arranged to correspond to the first medium orifice 31m. An opening 34 is formed in the shutter 22 facing these orifice groups F and coinciding with the opening 32 in the axial direction of the shutter 22. By rotating the shutter 22, the opening 34 is connected to each orifice 33s. , 33m. In addition, orifice group F
The position coincides with the first small orifice 31h.
No orifice is formed in Rh.

In FIG. 3, a step is formed inside the shutter 22, and a check valve 35 is constantly pressed against this step by a return spring 36.

When the electric motor 23 is rotated and the openings 32 and 34 of the shutter 22 are aligned with the position Rs, the opening 32 faces the first large orifice 31s and the opening 3
4 faces the second large orifice 33s. In this state, during the extension stroke of the variable damping force shock absorber 5, the check valve 35 closes, so the piston upper chamber C
is connected to the piston lower chamber D through the opening 27 of the atsuparo rod 14 - the second large orifice 33s with a large opening area - the passage 28 of the shutter 22 - the passage 29 of the cylindrical body 21 - the passage 30 of the lower rod 15, and the damping force becomes soft. Become. Also, in the retraction stroke, the check valve 3
5 opens, the upper chamber C of the piston is opened
4 opening 27 - first large orifice 31s and second large orifice 33s with a large opening area - passage 28 of shutter 22 - passage 29 of cylindrical body 21 - passage 30 of lower rod 15 to communicate with piston lower chamber D, damping. The force becomes soft.

Also, the electric motor 23 is rotated, and the shutter 2
When the openings 32 and 34 of No. 2 are aligned with the position Rm, the opening 32 faces the first middle orifice 31m, and the opening 34 faces the second middle orifice 33m. In this state, during the extension stroke of the variable damping force shock absorber 5, the check valve 35 closes, so that the piston upper chamber C is opened 27 - second middle orifice 33m with a medium opening area - passage 28 - passage 29 - passage 30
It communicates with the piston lower chamber D through , and the damping force becomes medium. Also, in the retraction stroke, the check valve 35 opens, so that the piston upper chamber C has an opening 27 - a first middle orifice 31m and a second middle orifice 33m with medium opening areas - passage 28 - passage 29 - passage 30.
It communicates with the piston lower chamber D through , and the damping force becomes medium.

Furthermore, when the electric motor 23 is rotated to align the openings 32 and 34 of the shutter 22 with the position Rh, the opening 32 faces the first small orifice 31h.
In this state, during the extension stroke of the variable damping force shock absorber 5, the check valve 35 closes, so the piston upper chamber C and the piston lower chamber D are in a disconnected state.
The damping force becomes hard. Also, in the retraction stroke, the check valve 35 opens, so the piston upper chamber C opens at the opening 27.
- The first small orifice 31h with a small opening area - communicates with the piston lower chamber D through the passage 28 - passage 29 - passage 30, and the damping force becomes hard.

Returning to FIG. 2, numeral 38 is a vehicle speed sensor that generates a vehicle speed pulse signal for detecting vehicle speed, and this vehicle speed sensor 38 detects, for example, the rotation of the output shaft of a transmission or the propeller shaft.
39 is a steering angle sensor, and this steering angle sensor 3
9 is, for example, a potentiometer type that detects the rotational position of the steering wheel relative to the steering column as a voltage value, or a photoelectric type that detects the rotational movement of the steering wheel as two voltage pulse signals with a phase shift. used. 40 is a fuel pulse sensor, and this fuel pulse sensor 40 detects a fuel pulse signal for operating the fuel injection valve of the engine. Reference numeral 41 denotes a vehicle height sensor that uses ultrasonic waves to detect road surface conditions, and this vehicle height sensor 41 emits ultrasonic waves from a transmitter and then receives the ultrasonic waves reflected by the road surface using a receiver. The vehicle height value is detected by converting the time it takes to reach the vehicle into a distance, and the road surface condition can be detected based on this detection signal.

43 is a controller, and this controller 43 drives a microcomputer 44, a drive circuit 45 that drives the switching valve 10 of the variable spring constant spring device 4, and an electric motor 23 of the variable damping force shock absorber 5 on the front wheel side. A drive circuit 46a and a drive circuit 4 that drives the electric motor 23 of the variable damping force shock absorber 5 on the rear wheel side.
6b.

The microcomputer 44 includes at least an interface circuit 47 and an arithmetic processing unit 48.
The input port side of the interface circuit 47 includes a vehicle speed sensor 38, a steering angle sensor 39, a fuel pulse sensor 40, a vehicle height sensor 41, and a variable damping force shock absorber. 5 is connected to the rotational position sensor 25, and a drive circuit 4 is connected to the output port side.
5, 46a, and 46b are connected.

The arithmetic processing unit 48 includes an interface circuit 47
Detection signals from the sensors 38 to 41 are read in, and calculations and other processes described later are performed based on these signals. Further, the storage device 49 stores a predetermined program necessary for executing the processing, and also stores processing results of the arithmetic processing device 48 and the like.

In addition, each switching valve 10 of the spring constant variable spring device 4 attached to the front, rear, left, and right four wheels is connected to a drive circuit 45, and the four-wheel switching valves 10 are simultaneously driven by the drive circuit 45, so that the spring constant of the four wheels is adjusted. At the same time, it is set to soft or hard.

In addition, the variable damping force shock absorber 5 installed on the front, rear, left, and right four wheels has a drive circuit 46a on the front wheel side.
The rear wheel side is connected to the drive circuit 46b, the front wheel side and the rear wheel side are driven independently of each other, and the damping force is set separately for the front and rear wheels. However, it is also possible to set the same damping force to the front and rear wheels at the same time.

As explained above, in this embodiment, the spring constant can be changed to two types, soft S and hard H, and the damping force can be changed to three types, soft S, medium M, and hard H. There are six possible combinations, but in this example, the combinations actually used are as shown in FIG.
Five types of combinations are used: spring constant soft - damping force soft, spring constant soft - damping force medium, spring constant soft - damping force hard, spring constant hard - damping force medium, and spring constant hard - damping force hard. At this time, the spring constants are soft- _k1 , hard- _k2 (> _k1 ), and the damping forces are soft- _F1 , medium- _F2 , hard- _F3 ( _F1 < _F2 <
F ₃ ), or the damping coefficients are soft-c ₁ , medium-c ₂ , hard-c ₃ (c ₁ <c ₂ <c ₃ ).

Then, if the sprung mass is m, the spring constant of the suspension device is k, and the damping coefficient is c, then the critical damping coefficient Cc = 2π・√ in the boundary state between over-damping and under-damping of the vertical vibration of the vehicle body.・The ratio between the damping coefficient c and this critical damping coefficient Cc is expressed as the damping ratio ζ=c/Cc, but ζ ₁ to ζ ₅ in the above combinations are as follows: ζ ₁ < ζ ₂ < ζ ₄ Each damping coefficient c and spring constant k are selected so that <ζ ₃ <ζ ₅ .

Also, using the sprung natural frequency as a parameter,
RMS of sprung mass acceleration when changing damping ratio ζ
(Root Mean Square) value is measured as shown in Figure 6, and as is clear from the figure, the RMS value of sprung mass acceleration is minimum at sprung mass natural frequencies of 1.8, 1.4, 1.0, and 0.6Hz, respectively. The damping ratio that minimizes the RMS value of the sprung mass acceleration can be said to be the optimal damping ratio for the sprung mass natural frequency.

The relationship between this sprung natural frequency and the optimum damping ratio is approximately a straight line as shown in FIG.

On the other hand, the size of the sub-tank 8 is inevitably determined by the layout of the vehicle, and therefore the lower limit value of the spring constant is determined, so the lower limit value of the natural frequency of the sprung mass is usually
Generally, it is about 0.8Hz, and from Fig. 7, when the natural frequency of the sprung mass is 0.8Hz, the optimum damping ratio is about 0.1. Therefore, in consideration of variations in the spring constant and damping force, the damping ratio ζ when both the spring constant and the damping force are soft is preferably set to about 0.075 to 0.125.

Furthermore, the five combinations of spring constant and damping force described above are used for various controls, as shown in FIG. 8, for example.

Next, the operation of this embodiment will be explained.

The spring constant of the variable spring constant spring device 4 is set to the same level for the front, rear, left and right wheels at the same time. Also, variable damping force shock absorber 5
It is possible to set the damping force of the front and rear wheels to separate stages, and it is also possible to set the four wheels to the same stage at the same time. In the explanation of the operation below, unless otherwise specified, damping force will be referred to as 4.
The rings shall be set to the same stage at the same time.

When the ignition switch is turned on, the controller 43 is powered on and the vehicle speed sensor 3 is turned on.
8, steering angle sensor 39, fuel pulse sensor 40,
Detection signals from the vehicle height sensor 41 and the rotational position sensor 25 of the variable damping force shock absorber 5 are supplied to an interface circuit 47 of the microcomputer 44 .

FIG. 9 shows the procedure of processing executed by the microcomputer 44.

In the figure, first, in step, it is determined whether the vehicle is running or not (that is, stopped) based on the vehicle speed pulse signal from the vehicle speed sensor 38. If the vehicle is stopped, the process moves to step and the combination is determined. A hard spring constant and hard damping force are set to control the shaking of the vehicle body when passengers get on and off the vehicle or when loading and unloading luggage while the vehicle is stopped.

When the spring constant is set to a hard value, a control signal of "H (high level or rotational value "1")" is supplied from the interface circuit 47 of the microcomputer 44 to the drive circuit 45 in FIG.
In this way, the switching valve 10 is removed from the drive circuit 45.
An excitation current of a predetermined value is supplied to the spring constant, and the spring constant is hard set as described above.

When the damping force is set to hard, a command value corresponding to the hard position is stored in the register of the microcomputer 44, and the shutter 22 is adjusted based on the detection signal of the rotational position sensor 25, as shown in FIGS. 2 and 3. The rotational position is read, and the drive circuits 46a and 46b supply drive current to the electric motor 23 to rotate the electric motor 23 until the command value matches the detected rotational position, and the shutter 2 is rotated.
By locating the openings 32 and 34 of No. 2 at the position Rh, the damping ratio is set hard.

Returning to FIG. 9, after setting the spring constant and damping force to hard in step, return.

If it is determined in step that the vehicle is running, the process moves to the next step to determine whether or not the vehicle is in a rolling state.

To determine whether or not the roll state is present, for example, a steering angle change rate determination level for determining the rate of change of the steering angle per unit time is set based on the vehicle speed value read in the step. The change rate per unit time is calculated from the steering angle value obtained from the detection signal of the sensor 39, and the steering angle change rate is compared with the steering angle change rate judgment level, and the steering angle change rate is determined as the steering angle change rate judgment level. If it is above, it is determined that the vehicle is in a roll state, and if it is smaller, it is determined that the vehicle is not in a roll state.

If it is determined in step that the vehicle is in a roll state, the process moves to step and sets the combination of spring constant hard and damping force medium to suppress the roll of the vehicle.

The case where the spring constant is set hard is as described above.

Also, when setting the damping force to medium,
2 and 3, the command value corresponding to the medium position is stored in the register of the microcomputer 44, the rotational position of the shutter 22 is read from the detection signal of the rotational position sensor 25, and the command value and the detected rotation By supplying drive current to the electric motor 23 from the drive circuits 46a and 46b to rotate the electric motor 23 until the two positions match, and by positioning the openings 32 and 34 of the shutter 22 at the position Rm, the damping force is set to medium. Set to .

Returning to Fig. 9, after setting the spring constant to hard and the damping force to medium in the step, return.

If it is determined in step that the vehicle is not in a roll state, the process proceeds to the next step, in which it is determined whether the vehicle is in an acceleration state or a deceleration state.

To determine whether or not the vehicle is in the acceleration/deceleration state, for example, the engine speed is calculated based on the period of the fuel pulse signal from the fuel pulse sensor 40, and the transmission is adjusted based on the engine speed and the vehicle speed value obtained in the step. A gear ratio is determined, and a judgment level for the amount of acceleration and a judgment level for the amount of deceleration are set according to this gear ratio. On the other hand, a fuel pulse width change rate is calculated based on the pulse width of the fuel pulse signal, and if this fuel pulse width change rate is equal to or higher than the acceleration amount judgment level, the vehicle is in an acceleration state, and the fuel pulse width change rate is If it is equal to or higher than the deceleration amount determination level, the vehicle is in a deceleration state, and if the fuel pulse width change rate is smaller than the acceleration amount determination level and smaller than the deceleration amount determination level, it is determined that the vehicle is not in an acceleration or deceleration state.

If it is determined in step that the vehicle is in an acceleration state or deceleration state, proceed to step and set the combination of spring constant hard and damping force medium, and if the vehicle is in an acceleration state, the skirt of the vehicle is If the vehicle is in a deceleration state, nose dive of the vehicle is suppressed.

If it is determined in this step that the vehicle is not in an acceleration or deceleration state, the next step is to determine whether or not the road the vehicle is traveling on is a good road (i.e., a bad road).
Determine whether

To determine whether or not the road is good, for example, the method described in Japanese Patent Application No. 160984/1984, which is an earlier application filed by the present applicant, is used. To briefly explain this method, a vehicle height value is obtained from the detection signal of the ultrasonic vehicle height sensor 41, and three vehicle height values, for example, this time, the previous time, and the time before the previous time, are stored in a predetermined storage area of the storage device 49. Digital filter processing is performed using three vehicle height values, and high frequency components of, for example, 1.8 to 3 Hz are detected.
Extract low frequency components between 0.2 and 1.8Hz. Then, the high frequency component and low frequency component are compared with a predetermined high frequency component determination level and low frequency component determination level, respectively, and the high frequency component of the vehicle height value is equal to or higher than the high frequency component determination level and the low frequency component is the low frequency component. If it is above the judgment level, it is determined that the road surface is bad, and if the high frequency component is smaller than the high frequency component judgment level and the low frequency component is smaller than the low frequency component judgment level, it is judged that the road surface is good.

If it is determined in step that the road surface is rough, the step moves on and sets the combination of spring constant hard and damping force hard to prevent pitching, roll, bottoming, and bouncing of the vehicle when driving on a rough road. etc. will be suppressed.

If it is determined in step that the road surface on which the vehicle is traveling is a good road, the process proceeds to the next step, in which it is determined whether the vehicle is traveling at high speed or not.

The determination as to whether or not the vehicle is traveling at high speed is made by, for example, comparing the vehicle speed value read in step with a predetermined high speed determination level, and if the vehicle speed value is equal to or higher than the high speed determination level, the vehicle is traveling at high speed. If it is smaller, it is determined that the vehicle is not traveling at high speed.

If it is determined in step that the vehicle is traveling at high speed, the step moves on to the step where the combination of spring constant soft - damping force hard (however, the damping force on the front wheel side is hard and the damping force on the rear wheel side is hard). The system is set to soft) to suppress pitching and roll of the vehicle while driving at high speeds, and to ensure a comfortable ride.

When setting the spring constant in a soft manner, in FIG. 2, a control signal of "L (roll bell, or logical value "0")" is supplied from the interface circuit 47 of the microcomputer 44 to the drive circuit 45.
In this way, the switching valve 10 is removed from the drive circuit 45.
No excitation current is supplied to the spring, and the spring constant is set to a soft value as described above.

Further, when setting the damping force on the front wheel side to be hard, the above-mentioned method of setting the four wheels to be hard at the same time may be performed only on the front wheel side.

When setting the damping force on the rear wheel side to a soft setting, as shown in FIGS. 2 and 3, a command value corresponding to the soft position is stored in the register of the microcomputer 44, and a rotational position sensor The rotational position of the rear wheel shutter 22 is read from the detection signal of 25, and the drive current is applied from the rear wheel drive circuit 46b to the rear wheel electric motor 23 until the command value and the detected rotational position match. supply to rotate the electric motor 23 and open the opening 32 of the shutter 22.
and 34 at position Rs, the damping force is set to be soft.

Returning to FIG. 9, after setting the spring constant to soft, the damping force on the front wheel side to hard, and the damping force on the rear wheel side to soft in step, return.

If it is determined that the vehicle is not traveling at a high speed, the process proceeds to the next step, in which it is determined whether the vehicle is traveling at a medium speed.

To determine whether or not the vehicle is running at medium speed, for example, the vehicle speed value read in step is compared with a predetermined medium speed judgment level, and if the vehicle speed value is equal to or higher than the medium speed judgment level, the vehicle is running at medium speed. If it is smaller, it is determined that the vehicle is running at a low speed.

If it is determined in step that the vehicle is running at medium speed, the step moves on to the step where the combination of spring constant soft and damping force is medium (however, the front wheel damping force is medium and the rear wheel damping force is medium). is set to soft) to suppress pitching and roll of the vehicle while driving at medium speeds, and to ensure ride comfort.

Further, when setting the damping force on the front wheel side to medium, it is sufficient to perform the method of setting the four wheels to medium at the same time only on the front wheel side.

The case where the damping force on the rear wheel side is set to be soft is as described above.

In step, the spring constant is set to soft, the damping force on the front wheel side is set to medium, and the damping force on the rear wheel side is set to soft, and then the process returns.

Additionally, if the step determines that the vehicle is traveling at low speed, the step moves to the next step.
The combination of soft spring constant and soft damping force ensures good ride comfort when driving on normal roads.

The case where the spring constant is set soft is as described above.

If you want to set the damping force to soft, use the method described above to set only the rear wheel side to soft.
You can do this for the ring. In this way, when the vehicle condition such as driving straight at low speed on a general good road becomes a predetermined condition for achieving the best ride comfort, both the spring constant and the damping force are set to the soft side, and in this condition. Since the damping ratio ζ ₁ is set to the minimum value as described above, the best ride quality of the suspension device can be exhibited.

In other words, Fig. 10 shows the spring constant soft - damping force soft, the spring constant soft - damping force hard, and the spring not used in the above example when actually driving on a general concrete road at a vehicle speed of 40 km/h. This is an actual measurement of the power spectrum (G ² /Hz) of the vertical acceleration on the spring in the frequency range of 0 to 30 Hz when set to constant hard - damping force soft. At this time, frequency 0~50Hz
The overall power (total amount of excitation energy given to the vehicle body: unit G ² /Hz) in the range of is
0.017 is 0.033, the combination of hard spring constant and soft damping force is 0.035, and the combination of is,
This is a 48% reduction in the case of the combination of , and a 51% reduction in the case of the combination of hard spring constant and soft damping force, indicating that the ride comfort is good in the case of the combination of .

In addition, in FIGS. 1 to 4 and 9,
The vehicle speed sensor 38, the steering angle sensor 39, the fuel pulse sensor 40, and the vehicle height sensor 41 are specific examples of vehicle state detection means.
A specific example of the spring constant setting means is provided by the drive circuits 46a and 46 with the processing of steps 0 and .
Specific examples of the damping force setting means are shown using the shutter 22, the electric motor 23, the rotational position sensor 25, and the processing in steps .

Further, in the above-described embodiment, the spring constant can be changed in two stages and the damping force can be changed in three stages, but the number of stages is not particularly limited, and any number of stages may be used.

Furthermore, although the configuration shown uses a microcomputer as a controller, it is also possible to use a combination of electronic circuits such as a counting circuit, a subtraction circuit, a division circuit, a command value setting circuit, a comparison circuit, and a logic circuit. It is also possible to configure a controller.

[Effect of idea]

As explained above, the vehicle suspension control device according to the present invention includes a suspension device including a variable spring constant spring device that can change the spring constant and a variable damping force shock absorber that can change the damping force; a vehicle state detection means for detecting the state of the vehicle; a spring constant setting means for setting the spring constant to a predetermined value according to the vehicle state detected by the vehicle state detection means; damping force setting means for setting the damping force to a predetermined value according to the vehicle state, the spring constant and the damping force of the suspension device when both the spring constant and the damping force are set to a minimum value; The damping ratio determined by the damping force is set to be the minimum compared to the damping ratio of the suspension device when the spring constant and damping force are set to other values, and the vehicle state detecting means When it is detected that the vehicle state is in a predetermined condition for realizing the best riding comfort, the spring constant setting means and the damping force setting means set the spring constant, damping force, and damping ratio to a state where all of them become minimum values. Since the configuration is controlled, it is possible to appropriately adjust the combination of spring constant and damping force according to the vehicle condition, improving the vehicle's maneuverability, stability, and ride comfort. When it is detected that the predetermined conditions for achieving comfort are met, the suspension device can exhibit the best riding comfort characteristics.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the basic configuration of a vehicle suspension control device according to this invention, Figure 2 is a diagram showing the configuration of an embodiment of this invention, and Figure 3 is a diagram showing the damping force used in this invention. A vertical cross-sectional view of an example of a variable shock absorber, FIGS. 4a and 4b are cross-sectional views taken along lines aa and b-b in FIG. 3, respectively, and FIG. 5 is a diagram showing a combination of spring constant and damping force. , Figure 6 is a diagram showing the relationship between the sprung mass natural frequency, damping ratio, and RMS value of sprung mass acceleration.
Figure 8 shows the relationship between the natural frequency of the sprung mass and the optimum damping ratio, Figure 8 shows the combination of spring constant and damping force, and the control in which that combination is used. Figure 9 shows the relationship between the spring constant and damping force. FIG. 10 is a flowchart illustrating the processing procedure, and is a diagram in which power spectra of sprung mass acceleration were actually measured for various combinations of spring constant and damping force. 2... Suspension device, 4... Variable spring constant spring device, 5... Variable damping force shock absorber, 7... Rolling diaphragm, 8...
...Subtank, 9...Pipe line, 10...Switching valve, 12...Tube, 13...Piston rod, 16...Piston, 21...Cylindrical body, 22...
...Shutter, 23...Electric motor, 25...Rotational position sensor, 31s...First large orifice, 31
m...First medium orifice, 31h...First small orifice, 32, 34...Opening, 33s...Second large orifice, 33m...Second medium orifice, 35
...Check valve, 36...Return spring, 38
...Vehicle speed sensor, 39...Steering angle sensor, 40...
... Fuel pulse sensor, 41 ... Vehicle height sensor, 43
...Controller, 44...Microcomputer, 45, 46a, 46b...Drive circuit, 47...
...Interface circuit, 48...Arithmetic processing unit,
49... Storage device, A... Main air chamber, B... Sub-air chamber, C... Piston upper chamber, D... Piston lower chamber, E, F... Orifice group.

Claims (1)

[Scope of utility model registration request] a suspension device including a variable spring constant spring device capable of changing a spring constant and a variable damping force shock absorber capable of changing a damping force; a vehicle condition detecting means for detecting a condition of the vehicle; spring constant setting means for setting the spring constant to a predetermined value according to the vehicle state detected by the vehicle state detection means; and damping force setting means for setting the damping force to a predetermined value according to the vehicle state detected by the vehicle state detection means. and a damping ratio determined by the spring constant and damping force of the suspension device when both the spring constant and damping force are set to a minimum value is one of the possible damping ratio values of the suspension device. the spring constant setting means and the damping force setting means when the vehicle state detecting means detects that the vehicle state is in a predetermined condition for realizing the best ride comfort. 1. A suspension control device for a vehicle, wherein a spring constant, damping force, and damping ratio are all controlled to a minimum value.