JPH04325304A - Control method and device for car suspension - Google Patents

Abstract

PURPOSE:To improve the durability of a damper by switching the damping force characteristic of the damper based on only the information of the vertical displacement speed of a car body on a spring, and reducing the number of switching to a half as compared with the conventional one in a vehicle having a suspension device including the suspension spring and the damper between wheels and the car body above them. CONSTITUTION:A damping force-variable damper capable of switching the first mode (a) having the soft characteristic on the expansion side and the hard characteristic on the compression side and the second mode (b) having the hard characteristic on the expansion side and the soft characteristic on the compression side is provided, and it is switched to the second mode (b) when the vertical displacement speed of a car body on a spring is upward and to the first mode (a) when the vertical displacement speed is downward.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling a vehicle suspension.

0002

[Prior Art] Research has been conducted to further improve riding comfort by changing the damping force of a damper in real time according to the vibration situation of a vehicle.
It is published in Publication No.-163011.

As shown in FIG. 7A, this prior art has hard characteristics on both the elongation and compression sides (shown by solid lines) and soft characteristics on both the elongation and compression sides (dotted lines). Using a switchable damping force variable damper (shock absorber), the vertical displacement speed of the sprung mass (i.e. the vehicle body) and the vertical relative displacement velocity between the sprung mass and the unsprung mass (suspension stroke speed) are detected and is upward (e.g. +) or downward (e.g. -), and if both are upward or downward, it becomes a hard characteristic; one is upward and the other is downward. In this case, the characteristics of the damper described above are switched to soft characteristics, and the phase difference between the vertical displacement speed on the spring and the suspension stroke speed is 90°.
The damper characteristics are switched as shown in FIG. 7(B) when the angle is .

0004

[Problem to be solved by the invention] The above method applies the theory of the skyhook damper (a virtual model that considers the suspension of one wheel as one degree of freedom and applies damping to absolute space) to the actual suspension position of a vehicle. This is approximated by the installed variable damping force damper, and has the effect of optimizing vehicle body vibration and improving ride comfort.

However, in the conventional device described above, since the damper characteristics are switched based on the vertical displacement speed of the spring and the suspension stroke speed, it is necessary to detect the vertical displacement speed and the suspension stroke speed of the spring for each suspension. Two sensors are required for (calculation), which is disadvantageous in terms of space and cost.Moreover, if control using these is implemented, the damper will have to be switched frequently, which may affect the durability of the damper.
The problem is that various problems arise due to increased drive power consumption.

The main object of the present invention is to solve the above problems.

[0007]

[Means for Solving the Problems] The present invention provides a damper, which is a component of a vehicle suspension device, with a first damper having a low damping force (soft) on the extension side and a high damping force (hard) on the compression side.
mode, and a second mode with high damping force (hard) on the extension side and low damping force (soft) on the compression side.
The damping force variable damper has a mode switching means that electrically switches between these two modes, and the controller determines whether the direction of the vertical displacement speed on the spring is upward or downward, and changes from upward to downward. When the time changes from the second mode to the first mode, when the direction changes from downward to upward, the first mode changes.
A signal to switch the mode of the variable damping force damper from the first mode to the second mode is issued, and the mode of the variable damping force damper is switched.

[0008]

[Operation] According to the above, when the sprung mass (vehicle body) is displaced upward, it is in the second mode, so the damping force characteristics are soft on the compression side and hard on the expansion side, and the sprung mass is displaced downward. Since it is in the first mode when the damping force is in the first mode, the damping force characteristics are hard on the compression side and soft on the expansion side.Therefore, there is no need for a means to detect the vertical relative displacement speed between the sprung mass and the unsprung mass, and the damping force of the variable damping force damper is By reducing the number of switching operations by half, it is possible to achieve the same effect as the conventional device in optimizing vehicle body vibration and improving riding comfort.

[0009]

[Examples] Examples of the present invention will be described below.

FIG. 1 is a diagram showing an example of the installation arrangement of the device of the present invention on a vehicle.
Suspension spring 1 (1a to 1d) and damper 2
(2a-2d) Suspension device 5 (5a-2d)
5d) is interposed.

As shown in FIG. 2A, the damper 2 has a first mode a (shown by a solid line) in which the extension side is soft (low damping force) and the compression side is hard (high damping force), and the extension side is soft (low damping force). is hard (
The compression side has two modes: a soft (low damping force) second mode b (indicated by a dotted line), and as shown in Figure 2 (B), the electric current is generated based on the vertical displacement speed on the spring. The damper 2 is designed to be switched between these modes, and specific structural examples of the damper 2 are shown in FIGS. 3 and 4.

As shown in FIGS. 3 and 4, the damper 2 consists of a rod 3 having a piston 31 fixed to its lower end and attached to the vehicle body at its upper end, and a cylinder 4 having its lower end attached to the wheel side. 31 is provided with an expansion side main passage 31a and a compression side main passage 31b, and the expansion side main passage 31a is provided with an expansion side main valve 31a',
A compression side main valve 31b is provided in the compression side main passage 31b.
The piston 31 is slidably fitted into the cylinder 4, and the upper chamber 41 and lower chamber 42 of the cylinder 4, which are partitioned by the piston 31, are filled with oil. From the upper chamber 41 to the lower chamber 42 (during expansion),
Also, by flowing from the lower chamber 42 to the upper chamber 41 (during compression) through the expansion side main passage 31a or the compression side main passage 31b, the rod 3 can move up and down relative to the cylinder 4, and the oil at that time can be moved up and down. The damping force is generated by the flow resistance.

A communication hole 32 is provided in the center of the rod 3, the lower end of which communicates with the lower chamber 42, and the upper part of the communication hole 32 communicates with the upper chamber 41 through an extension sub-passage 33 and a compression sub-passage 34. However, the expansion side sub-valve 33a and the compression side sub-valve 3 are provided in the expansion side sub-passage 33 and the compression side sub-passage 34.
4a are provided respectively.

Inside the rod 3, a plunger 35, a shaft 35a integrally fixed to the plunger 35, and a cylindrical shutter 35b integrally fixed to the lower end of the shaft 35a slide up and down by a predetermined stroke. A core bar 36 facing the upper part of the plunger 35, a magnet 37 for magnetizing the core bar 36, and a switching coil 38 are fixed to the inner peripheral wall of the rod 3 so as to be movable. At the same time, a spring 39 is provided that urges the shutter 35b downward. The plunger 35, shaft 35a, shutter 35b, core metal 36, magnet 37
, the coil 38, and the spring 39 constitute a mode switching means.

In the above, in the state shown in FIG. 3, the plunger 35, the shaft 35a integrally fixed thereto, and the shutter 35b are held in the lowered position by the biasing force of the spring 39, and the shutter 35b closes the compression side sub passage 34. In this state, when the rod 3 descends (compresses) with respect to the cylinder 4, the oil in the lower chamber 42 flows only through the compression side main passage 31b as shown by the solid line arrow. and flows into the upper chamber 41 through the rod 3
If it rises (extends) with respect to the cylinder 4, the upper chamber 41
The oil flows to the lower chamber 42 through the extension side main passage 31a and the extension side sub passage 33 as indicated by the dotted line arrow.
The damping force characteristics are hard on the compression side and soft on the extension side, which is the first mode a as shown by the solid line in FIG.

From this state, the magnet 3 is connected to the coil 38.
A current is passed that generates a magnetic field in the same direction as 7. Then, the plunger 35 is attracted to the core metal 36 and moves to the raised position against the urging force of the spring 39, and after the coil 38 is energized, the core metal 36, which has been magnetized by the magnetic field of the magnet 37, is moved to the upper position.
As shown in FIG. 4, the shutter 35b closes the extension sub-passage 33 and keeps the compression sub-passage 34 open.

In the state shown in FIG. 4, when the rod 3 descends (compresses) with respect to the cylinder 4, the oil in the lower chamber 42 passes through the compression side main passage 31b and the compression side sub passage 34 as shown by the solid line arrow. When the rod 3 rises (extends) relative to the cylinder 4, the oil in the upper chamber 41 flows only through the extension side main passage 31a as shown by the dotted line arrow and flows to the lower chamber 42, resulting in attenuation. The force characteristics are soft on the compression side and hard on the extension side, the second mode b as shown by the dotted line in Figure 2.
becomes.

From the state shown in FIG. 4, by passing a current through the coil 38 so as to generate a magnetic field opposite to that of the magnet 37, the magnetic field of the magnet is canceled out, and the plunger 3
5, the shaft 35a and the shutter 35b are lowered together by the biasing force of the spring 38, resulting in the state shown in FIG.

The energization time for transitioning from the state shown in FIG. 3 to the state shown in FIG. 4, and from the state shown in FIG. 4 to the state shown in FIG. The respective states are maintained by the suction force of the core metal 36 and the urging force of the spring 39.

With the configuration shown in FIGS. 3 and 4, the first mode a and the second mode b shown in FIG.
In a vehicle equipped with a suspension device 5 including this damper 2, a damper 2 that can be switched between the A vertical acceleration sensor 6 (6a to 6d) is attached to detect the vertical acceleration, and a detection signal of the vertical acceleration detected by the vertical acceleration sensor 6 is input to a controller 7, which issues a control signal for switching each damper 2. It is something.

FIG. 5 is a block diagram of the controller 7.

That is, the detection signals detected by each vertical acceleration sensor 6 are integrated by an integrating circuit 71 (71a to 71d) to produce a signal (voltage signal) corresponding to the vertical displacement speed, and the signal is sent via a multiplexer 72. The signal is input to the A/D converter 73, where it is converted into a digital signal, and the signal is input to the microcomputer 74. microcomputer 7
4 basically consists of an interface circuit 74a, an arithmetic processing circuit 74b, and a storage device 74c, and when a digital signal corresponding to the vertical displacement speed output from the A/D converter 73 is input to the interface circuit 74a, The arithmetic processing circuit 74b determines whether the direction of the vertical displacement speed is upward (for example, + sign) or downward (for example, - sign), and stores the determination result in the storage device 74c, so that the vertical displacement speed is When the direction changes from upward to downward (when it changes from + to -), the drive circuit 8
(8a to 8d), a switching signal from the second mode to the first mode in FIG.
When a switching current is applied to switch the damper 2 from the second mode in FIG. 4 to the first mode in FIG. 3, and the vertical displacement speed changes from downward to upward (changes from - to +),
A switching signal from the first mode to the second mode is issued from the interface circuit 74a to the drive circuit 8, and a switching current in the opposite direction to that described above is caused to flow through the coil 38, thereby switching the damper 2 from the first mode in FIG. 3 to the mode in FIG. 2 modes. Note that when the vertical displacement speed is 0, the first mode or the second mode may be set.

The above control is shown in a flowchart as shown in FIG.

When the control of the present invention is applied to the vertical displacement speed of the spring that changes sinusoidally, the result is as shown in FIG. 2(B). In this figure, the dotted line represents the vertical relative displacement speed (suspension stroke speed) between the sprung mass and the sprung mass, and the phase difference between this suspension stroke speed and the sprung mass vertical displacement speed is in the range of 0° to -90°. However, FIG. 2B shows a case where the phase difference is -90°.

As shown in FIG. 2(B),
Mode switching of damper 2 is performed when the vertical displacement speed on the spring is +
It is performed only when changing from - to + and when changing from - to +,
The number of switching is half compared to the conventional one shown in FIG. 7(B), but while the vertical displacement speed on the spring is + and the second mode is, the suspension stroke speed is - (i.e., compression side). When the suspension stroke speed is + (that is, on the extension side), the characteristics are soft, and when the vertical displacement speed on the spring is - and the first mode is, the suspension stroke speed is + ( In other words, the characteristics are soft when the suspension stroke speed is - (i.e., on the compression side), and the characteristics are hard when the suspension stroke speed is - (i.e., on the compression side). Therefore, a vehicle structure similar to the conventional one shown in Fig. 7 can be used without means for detecting (calculating) the suspension stroke speed. This can bring about an excellent effect of optimizing vibration and improving riding comfort.

[0026] In the above, hard (high damping force) and soft (low damping force) are not defined by specific numerical values, but are relative terms.

Furthermore, the configuration of the variable damping force damper 2 used in the present invention is not limited to that shown in FIGS. 3 and 4, but may have an extension side and a compression side as shown in FIG. It is possible to employ a variable damping force damper having an arbitrary configuration capable of switching between a first mode and a second mode, each of which has asymmetric damping characteristics.

[0028]

As described above, according to the present invention, by using a variable damping force damper and switching the damping characteristics of the variable damping force damper, the direction of the vertical displacement speed of the sprung mass (vehicle body) and the direction of the suspension stroke speed can be changed. When the characteristics are the same, the characteristic is hard, and when the direction of the vertical displacement speed on the spring and the direction of the suspension stroke speed are different, the characteristic is soft.This is the characteristic that optimizes vehicle body vibration and improves ride comfort. This eliminates the need for a means to detect suspension stroke speed, and can accurately achieve the above-mentioned effect of optimizing vehicle body vibration by simply switching the variable damping force damper based on the vertical displacement speed of the spring, eliminating the need for means for detecting suspension stroke speed. In addition to cost and space benefits, the number of switching times of the variable damping force damper is halved compared to conventional dampers, and the durability of the damper can be improved, which has a great practical effect. It is possible to bring about

[Brief explanation of drawings]

FIG. 1 is a perspective explanatory view showing an example of how the device of the present invention is mounted on a vehicle.

FIG. 2 shows an embodiment of the present invention, in which (A) is a damping force characteristic diagram of the first mode and second mode of the variable damping force damper used in the present invention, and (B) is the vertical displacement on the spring. 5 is a time chart showing a mode switching manner with respect to a change in speed.

FIG. 3 is a sectional view of a main part of a specific example of a variable damping force damper used in the present invention, showing a first mode.

4 is a sectional view of a main part of the variable damping force damper of FIG. 3 in a second mode; FIG.

FIG. 5 is a block diagram of a controller.

FIG. 6 is a flowchart showing a control mode of the controller.

FIG. 7 shows an example of a conventional device, in which (A) is a damping force characteristic diagram of a variable damping force damper, and (B) is damping with respect to the vertical displacement speed of the sprung mass and the vertical relative displacement velocity of the sprung mass and the unsprung mass. 5 is a time chart showing a force characteristic switching mode.

[Explanation of symbols]

1 Suspension spring 2
Variable damping force damper 3 Rod 4 Cylinder 5 Suspension device 6 Vertical acceleration sensor 7 Controller 31 Piston

Claims (2)

[Claims] Claim 1: In a vehicle in which a suspension device including a suspension spring and a damper is interposed between each of the front, rear, left and right wheels and the vehicle body above the wheel, the damper has a low damping force on the extension side and a low damping force on the compression side. is a variable damping force damper that can switch between a first mode with a high damping force characteristic and a second mode with a high damping force characteristic on the extension side and a low damping force characteristic on the compression side. Detects whether the vertical displacement speed on the spring is upward or downward,
A method for controlling a vehicle suspension, characterized in that the variable damping force damper is switched and controlled so that the damping force variable damper is in the second mode when the damping force is upward, and the first mode is when the damping force is downward. [Claim 2] In a vehicle in which a suspension device including a suspension spring and a damper is interposed between each of the front, rear, left, and right wheels and the vehicle body above the wheel, the damper is compressed with a low damping force on the rebound side. The side is the first with high damping force.
mode, and a second mode with high damping force on the extension side and low damping force on the compression side.
The variable damping force damper is equipped with a mode switching means for electrically switching between the two modes, and a vertical acceleration sensor is attached to each suspension device mounting part to detect vertical acceleration on the spring. The vertical displacement speed on the spring is determined from the detection signal of the vertical acceleration sensor, it is determined whether the vertical displacement speed is upward or downward, and when the direction of the vertical displacement speed changes from upward to downward, the second mode is activated. The variable damping force damper is characterized by being provided with a controller that generates an electrical signal to switch the mode of the variable damping force damper from the first mode to the second mode when the direction of the vertical displacement speed changes from downward to upward. Vehicle suspension control device.