JPS6050010A - Suspension system for automobile - Google Patents

Abstract

PURPOSE:To stabilize the switching characteristics and to improve the responsiveness in a suspension system capable of variable damping force and spring characteristics by switching the damping force and spring characteristics of the suspension system based on the reference rate of steering input relative to the vehicle speed and the detected rate of steering input. CONSTITUTION:Steering angle 2, vehicle speed 3 and other inputs are inputted to a CPU16 via an input circuit 15. The CPU computes the average shift of the pulse frequency based on the latest N pulses in the vehicle pulse signal 3 in accordance with the predetermined program. Next, based on the information from the steering sensor 2, the change in the pulse edge and the sequence of the change are checked to determine the presence or non-presence of the change in the turning direction. If it is a positive turning, one cycle of the pulse is measured and the aggregate of the rate of steering input is computed. When it is greater than the reference value, an actuator 6 and a pneumatic spring 10 are set ''hard'', and is set ''soft'' when it is smaller. If turning in the negative direction, the ''soft'' setting is selected. In this manner, the switching characteristics are stabilized, and the responsiveness can be improved.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a suspension system for an automobile, and more particularly to a device for switching the damping force of a shock absorber of a suspension system and the spring characteristics of a suspension spring in accordance with a driver's steering wheel operation. It is something.

[Prior art]

Conventionally, this type of device calculates the centrifugal force of the car from the steering angle and vehicle speed, and controls only the damping force of the shock absorber. One that controls only the damping force of the absorber has been proposed.

By the way, changing only the damping force of the shock absorber is not very effective in improving rolling during steady turning. On the other hand, switching the damping force alone can have some effect on rolling that occurs suddenly, but the detection of vehicle speed and steering angle must be accurate and high-speed to achieve the desired effect.

A typical vehicle speed sensor uses a lead switch or Hall IC to detect the rotation of a magnet, which is proportional to the rotation of the wheel, and outputs a pulse number. Although the responsiveness of vehicle speed determination cannot be faster than this, it has the drawback that the error in the pulse period for each period is inaccurate for the following reason. The first cause of error is due to variations in the shape of the rotating magnet and eccentricity of the center of the rotating shaft, and this can be improved with machining accuracy and assembly accuracy, but the second cause of error is due to the wheel and vehicle speed. This is due to the jump rope phenomenon of the relay cable between the meter (when rotation is transmitted through the wire harness, uneven rotation occurs due to friction between the wire harness and the clothing), and this occurs over time as it is used. It progresses to

For these reasons, the vehicle speed is calculated from one period of the pulse width of the vehicle speed pulse, and the damping force of the shock absorber and the spring characteristics of the suspension spring are changed based on the steering angle information corresponding to that value. The disadvantage is that stable switching characteristics cannot be obtained.

Next, when using a steering angle sensor that outputs a pulse signal every time the steering wheel rotates by a predetermined angle, it has the disadvantage that it cannot accurately detect the steering angle or steering angle speed when the direction of rotation changes. However, depending on the pulse signal processing method, there is a drawback that the responsiveness of steering angle detection is impaired.

[Summary of the invention]

This invention is intended to eliminate the above-mentioned drawbacks by changing not only the damping force of the shock absorber but also the spring characteristics of the suspension spring according to the driver's steering wheel operation.
The objective is to realize a suspension system that suppresses posture changes such as rolling of the vehicle body, and to improve calculation accuracy without sacrificing responsiveness when calculating vehicle speed using pulse signals from a vehicle speed sensor. The purpose of this invention is to improve responsiveness when detecting a steering angle or a steering angular velocity using a pulse signal from a steering wheel, prevent malfunctions during reverse rotation, and improve calculation accuracy.

[Embodiments of the invention]

FIG. 1 is a block diagram of a suspension system according to an embodiment of the present invention. In the figure, (1) is a control device composed of a microcomputer, which receives signals from a steering angle sensor (2), a vehicle speed sensor (3), Depending on other input information INPUT, an actuator (6) that changes the variable orifice diameter in the shock absorber (5) and a connecting passage (10) between the air spring (9) are opened and closed.

(4) is the vehicle body, and (5) is the shock absorber. When the orifice diameter of the oil passage in the shock absorber is changed to a large one by the actuator (6), the damping rate becomes small, and conversely, when the orifice diameter is changed to a small one, the attenuation rate is reduced. Rates vary widely. (7) is a wheel, (8) is an arm, and (9) is an air splash chamber, consisting of chamber A (9a) and chamber B (9b), and a connecting passage (
10) When opened, chamber A (9a) and chamber B (9b) are connected, and the spring constant becomes small and soft. On the other hand, the connecting passage (
10) When closed, the spring constant increases and becomes stiffer. (
11) is an auxiliary spring. (12) is the steering, (
13) is the steering shaft. The rotation of the wheel is coupled into the speedometer by a wire (3c), causing the magnet (3b) to rotate. By rotating the magnet (3b),
The lead SW (3a) is turned on and off. This lead S
The vehicle speed is calculated from the ON-OFF pulse signal of W(3a).

In the suspension system configured as described above, the vehicle speed sensor (
An embodiment of the method of calculating the vehicle speed from the output of 3) will be described.

Figure 2 shows the output waveform of the vehicle speed sensor (3).

The ON-OFF signal of the lead SW (3a) or the pulse signal after waveform shaping after filtering chattering, noise, etc. has the following characteristics. First of all, the magnet (3
b) is a component due to machining errors such as eccentricity, and if 4 pulses are output per rotation as in this embodiment, t1
, t2, t3, and t4. The second error is due to the jump rope phenomenon of the wire (3c), which changes with time, but still tl, t2
, t3...tn causes fluctuations in the period.

However, these errors and fluctuation components are caused by one rotation of the wire (3c) or one rotation of the magnet (3b).
It outputs accurate rotation speed information for each rotation, and in Figure 2, tl≠t2≠t3≠t4≠, t1≒t5, t2≒t6,
tn=tn+4 holds true, and t10≒t11≒t12 holds true.

Therefore, the best way to calculate the vehicle speed accurately and with the most responsiveness is to use the magnets (
3b) Calculate the vehicle speed from the reciprocal of t10, t11, t12, which is the sum of the four pulse intervals output per rotation. Alternatively, store t1, t2, t3, and t4 in memory, calculate the average value of the four values, and calculate the vehicle speed from the average value. After that, t2, t3, t4, and t5
Find the average value of the four values and calculate the vehicle speed from that average value. In this way, the vehicle speed is determined by successively taking the moving average value in the t1O section, then the tll section, and then the tl2 section. In this way, accurate and responsive calculation and determination of vehicle speed can be realized. Such averaging processing and calculations can be easily performed by using a microcomputer in the control device (1) and counting each period t1...tn and storing t1...tn in the memory every time a pulse edge is input. It goes without saying that this can be achieved. Also, the calculation of the vehicle speed itself is not directly necessary for the determination; the average value of the period itself may be used for determination, and it can be used as a coordinate table for a map for determination or a coordinate table for map interpolation calculations. Needless to say.

The configuration and flowchart of the control device (1) for calculating the vehicle speed from the output of the vehicle speed sensor (2) will be described later.

Figures 3 and 4 are configuration diagrams of a steering angle sensor according to an embodiment of the present invention. In the figures, (21) and (22) are cases that house a phototransistor (25) and a photodiode (26). , constitutes two optical switches SW1 and SW2 called photointerrupters. This optical switch SW1
, when the slit (27) is rotated in SW2, the optical switch is turned ON when the slit hole (24) passes through.
, when the light is blocked by the mask (23), the optical switch turns to O.
Becomes FF. The slit (27) is attached to the shaft (13) of the steering wheel (12) shown in FIG. 1, and rotates in accordance with the rotation of the steering wheel. If the width T of the slit mask (23) or hole (24) and the distance D between the phototransistors (25) are set so that the relationship 3/2T=D holds, the outputs of the two optical switches SW1 and SW2 will be , output pulse signals with a phase difference of 90° in electrical angle.

Next, an embodiment of the steering angle detection method will be described.

FIG. 5 shows the detection waveforms of the steering angle sensor (2) shown in FIGS. 2 and 3, which is an embodiment of the present invention, that is, the operating waveforms of the optical switches SW1 and SW2.

Optical switches SW1 and SW2 each output a pulse signal at a rate of one pulse for every 30° rotation of the steering wheel (12), and during forward rotation, SW1 outputs a pulse signal from a→c→a→c and SW2.
outputs pulse edge output in the order b→d→b→d. The period of this pulse is each steering (12)
Needless to say, this corresponds to the rotational speed of . In the embodiment shown in Fig. 5, the steering wheel (12) is first rotated in the forward direction at a constant speed, and then immediately after the edge a of SW1 rises and remains in that state for a while, it is then rotated in the opposite direction at a constant speed. This is a time chart when the situation is reversed.

In the case of forward rotation, the pulse edge of SW1 and SW2 is a→b→
By checking the order of c→d, a reversal of the rotation direction can be detected. Furthermore, the edge spacing from a to the next a, from b to the next b, as shown in Figure 5, is 1, 2.3.4,...
By measuring in the order of
By integrating the four angles, the total steering angle can be detected.

If the steering wheel (12) reverses from normal rotation to reverse rotation, a→
Since the order of edges b→c→d continues, the detection of the steering angle velocity from the edge interval and the calculation of the total steering angle are once stopped.

Next, check the order of the pulse edges after reversal, and a → d
If you check whether the order of →c→b→a is correct and calculate the steering angle velocity or the sum of the steering angles from time to time from cycles 11, 12, 13, and 14 in the figure,
Even during reverse rotation, the steering angle speed and the steering angle itself can be detected in the same way as during normal rotation.

Such detection methods and calculations also use a microcomputer in the control device (1), and each time the pulse edges of SW1 and SW2 are input, the period of the pulse edge interval is counted, the number of times the edge passes is counted, and the data is stored in the memory. Needless to say, depending on the situation, it can be realized within the valley.

Next, based on the basic configuration of the control device (1) of the present invention shown in FIG. 6, the operation will be explained with reference to flowcharts shown in FIGS. 7 and 8.

FIG. 6 is a basic configuration diagram of a control device (1) according to an embodiment of the present invention. In the figure, (15) is an input circuit including a steering angle sensor (2),
The vehicle speed sensor (3) and other input information INPUT are waveform-shaped and sent to the CPU (16). (17) is a memory, which has memories A to E such as ROMPRAM, and stores calculation processing procedures, input information, calculation results, and the like. (
18) is an output circuit that controls the actuator (6) of the shock absorber (5) and the connecting passage (10) of the air spring (9).

In Fig. 7, step (1) is the electronically controlled suspension main routine, which is a control that switches the spring characteristics and suspension characteristics to hard or soft depending on other driving information other than vehicle speed and steering angle. It is to control.

In step (2), a moving average of the latest N pulse periods (four in the embodiment) is calculated from the vehicle speed pulse signal shown in FIG. 2, which is similar to the main routine shown in FIG. Separately, an interrupt request is generated for each pulse edge of the vehicle speed pulse, and this calculation is performed in the interrupt routine. FIG. 8 shows a flowchart of one embodiment of this interrupt routine.

FIG. 8 is a flowchart showing the flow of a vehicle speed calculation interrupt program according to one embodiment of the present invention.

In STEP 1, the rising edge of the vehicle speed pulse is connected to the control device (
When input to the input circuit (15) of 1), vehicle speed calculation is started. As STEP 2, the edge period of the vehicle speed pulse (Fig. 2, t1, t2, ...) is measured by storing the value of the free running counter in memory A when the edge is input, and then when the previous edge is input. The time t between pulses, that is, the pulse period, can be determined by subtracting the value of the free running counter stored in memory B and multiplying by the time it takes for the free running counter to increase by 1. At this time, the contents of memory A are roughed into memory B and used for calculating the pulse period when the next edge is input. Further, the calculated pulse period is stored in one of the four memories C to F, and the memory stored is the memory that stores the oldest pulse period among the four. In this embodiment, the vehicle speed is increased by adding one revolution of the vehicle speed sensor, that is, four vehicle speed pulse periods, so four memories are prepared to store the pulse periods, and the newly calculated pulse periods are sequentially added. This is to always store the latest four vehicle speed pulse cycles by replacing them with the old ones.

Next, in STEP 3, these four memories C, D, E,
F is added and stored in the memory G in STEP 4. this,
The value in the memory G is rewritten every time an edge of the vehicle speed pulse is input, so that the latest vehicle speed is always stored. Also, the vehicle speed cycle of this memory G is the vehicle speed sensor 1.
It corresponds to rotation, and is highly reliable as it eliminates errors such as magnet variations and cable harness jump rope phenomena. The vehicle speed can be easily determined in STEP 5 by comparing the contents of the memory G with a threshold value for vehicle speed determination stored in another memory, for example, the memory H.

In addition, it is not necessary to add the values in memories C to F each time an edge is entered and memories C to F are rewritten; instead, the contents of memories C to F are added only when it is necessary to determine the vehicle speed. You may.

Returning to FIG. 7, in step (3), the determination value of the steering angle or steering angular velocity is calculated or memory mapped, corresponding to the moving average value of the vehicle speed calculated in step (2) or in the interrupt routine. It is calculated and stored in the rudder angle storage memory.

In step (4), the information of the output signals SW1 and SW2 of the steering angle sensor (2) shown in FIG. 5 is read, and the forward/reverse rotation of the steering angle, the steering angle speed, the total sum of the steering angles, etc. are calculated.

For example, edge a can be detected by changing SW2 to O and SW1 to 0-1. Other edges b, c, and d can be similarly detected by monitoring the levels of both SW1 and SW2.

To detect the rotation direction, by memorizing the order in which the past edges arrived, you can predict the next edge in the case of forward rotation, and if it differs from the predicted value, you can know that it is a reverse rotation.

In step (5), the next pulse edge predicted in step (4) is compared with the actual pulse edge to determine whether forward rotation continues or reverse rotation occurs. If the rotation is forward, proceed to step (6); if the rotation is reverse, the suspension is softened and return to step (1).

If it is a forward rotation, check the order of past edges, check whether the same edge as the edge that arrived this time is stored in the edge 4 times ago, and if so, check the time between that edge and the edge. The latest value of the steering angular velocity can be detected by measuring the interval or period. This steering angular velocity value is updated to the latest value as soon as the next edge arrives as long as the steering continues to rotate in the normal direction, so it is characterized by good responsiveness and can be used to control mounts, suspension, and spring characteristics. It is perfect for.

For example, in Figure 5, if the edge (b) of SW2 arrives, the edges have already arrived as a → b → c → d → a → (b) and are still rotating in the normal direction. The edge 4 times before is b. If you measure the interval between the edges from b four times before to (b) this time, that is, period 3, with a timer, the latest value of the steering angular velocity will be calculated. When the edge C of the grammar arrives, period 4 is calculated, and then the steering angle velocity is calculated in period 4, so the steering angle can always be determined using the latest value, so excellent responsiveness can be expected. There is. Moreover, by integrating the value of 30°/4 at the same time as the arrival of the edge, the total sum of the steering angle can also be detected. It goes without saying that when detecting the sum of the steering angles, the sum of the steering angles from the reference position can also be easily detected by using another reference position detection pulse signal (not shown).

The total steering angular velocity or steering angle obtained in this way and the judgment value corresponding to the vehicle speed are read from the memory, and step (7)
) and if the steering angular speed or steering angle is greater than the judgment value, the suspension etc. are made harder and the process returns to step (1). If not, soften the suspension etc. and return to step (1).

Note that in this invention, the edge spacing is 1, then 2, then 3, and so on.
As mentioned above, in this embodiment, since the information on the new steering angle speed and the total steering angle can be updated every 30°/4, the steering angle can be detected with high precision and good responsiveness. In this embodiment, the steering angle sensor (2) outputs one pulse every 30° rotation of the steering wheel (12).
It goes without saying that similar effects can be obtained even with a steering angle sensor (2) of a type that outputs one pulse for every predetermined angle such as .degree.

Based on the information corresponding to the vehicle speed obtained in this way and the information corresponding to the steering angle or steering angle speed, sudden or abnormal changes in the vehicle's attitude can be predicted, and the shock absorber (
The damping force can be changed by switching the orifice (6) of 5), or the chamber A (9a) and chamber B (9B) of the air spring (9).
By opening and closing the connecting passageway (10) and switching the spring constant, switching control can be performed with good reproducibility and very quick response characteristics because the switching point is accurate.

Moreover, since not only the damping force of the shock absorber (5) but also the spring characteristics are changed at the same time, it is possible to expect the effect of suppressing not only sudden changes in the attitude of the vehicle body but also rolling during steady turning.

In addition, in the present invention, a method of detecting the vehicle speed using a lead SW has been described, but any method such as an optical method, a magnetic method, an electromagnetic pickup method, etc. can be used as long as it is composed of a rotating body and a sensor. Needless to say, similar effects can be expected.

Although an optical type steering sensor has been described, it goes without saying that the same effect can be expected even if a magnetic type or other type is used. The method of switching the damping force of the shock absorber is not the method of switching the orifice, but may be any other method, and the spring constant can be changed not only by changing the volume of the air spring, but also by changing the spring constant of a leaf spring, Macintosh rubber, etc. It goes without saying that similar effects can be expected even with a switching method.

〔Effect of the invention〕

As explained above, according to the present invention, a sudden change in the posture of the car caused by the steering wheel operation is suppressed by changing the damping rate and spring constant of the shock absorber of the suspension system. This has the effect of suppressing not only posture changes but also gradual rolling caused by steady turning.

In addition, when detecting the vehicle speed from the vehicle speed pulse, the vehicle speed sensor 1
With a simple configuration that uses the sum or moving average of the period for each number of pulses generated per revolution and updates that value for each pulse of vehicle speed, it is possible to detect vehicle speed accurately and with good responsiveness. Yes, to detect the steering angle or steering angle speed, a sensor is used that generates one pulse per predetermined rotation of the steering wheel in two pulse trains with a phase difference of approximately 90°, and the direction of rotation is detected in the order of the pulse edges. However, with a simple configuration in which the steering angular velocity or steering angle of rotation in the same direction is updated every edge of two pulse trains, it is possible to detect the steering angle and steering angle speed accurately and with good responsiveness. effective.

Based on the accurate and responsive vehicle speed, steering angle, and steering angle speed obtained in this way, the characteristics of the suspension system can be changed to create a suspension system that provides optimal ride comfort and handling. There is an effect that can be provided.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of an embodiment of the present invention, Fig. 2 is a waveform diagram showing input pulses from a vehicle speed sensor, Fig. 3 is a perspective view showing an embodiment of the steering angle sensor, and Fig. 4 ( a) and (b) are front and side views of the steering angle sensor, FIG. 5 is a waveform diagram showing input pulses from the steering angle sensor, FIG. 6 is a basic configuration diagram of the control device used in this invention, and FIG. FIG. 7 is a flowchart for explaining the operation of an embodiment of the present invention, and FIG. 8 is a flowchart for calculating and determining vehicle speed. In the figure, (1) is the control device, (2) is the steering angle sensor, (
3) is a vehicle speed sensor, (4) is a vehicle body, (5) is a shock absorber, (6) is an actuator, (7) is a wheel, (8) is a
) is the arm, and (9) is the air spring. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa Figure 6 Figure 7 Figure 8 Procedure amendment (voluntary) 1.91 magazine ~ 1130 41121. Moon El-? Commissioner of the Japan Patent Office 1, Indication of the case No. 58-159198 2, Name of the invention Suspension system for automobiles 3, Representative of the person making the amendment 5, Details of the invention in the specification subject to the amendment Explanation Column 6, Contents of Amendment (1) In the 5th line of page 14 of the specification, the phrase ``1 rough cut,'' is corrected to ``transfer,''. that's all

Claims (2)

[Claims] (1) In a suspension system having a shock absorber with switchable damping force and a suspension spring with switchable spring characteristics, a vehicle speed sensor that generates a pulse signal proportional to the rotational speed of the wheel; Assuming that the vehicle speed sensor outputs N pulse signals per rotation, the vehicle speed is calculated based on the moving average of at least the latest N pulse periods of the pulse signals or the sum of at least the latest N pulse periods. a steering angle sensor that outputs a pulse signal at every fixed angle according to the rotation of the steering wheel, and outputs two pulse train signals having an electrical angle phase difference of approximately 90 degrees; and this steering angle sensor. and a second means for detecting the steering angular velocity from the pulse interval of the latest pulse signal when the steering wheel rotates by a certain angle in the same direction among the two pulse train signals from the steering wheel, and the steering angular velocity is determined by the first means. A suspension system for an automobile, wherein the damping force and spring characteristics of the shock absorber are switched by comparing a determination value of the steering angular velocity according to the vehicle speed with the steering angular velocity detected by the second means. (2) In a suspension system having a shock absorber with switchable damping force and a suspension spring with switchable spring characteristics, a vehicle speed sensor that generates a pulse signal proportional to the rotational speed of the wheel, and a vehicle speed sensor that generates a pulse signal proportional to the rotational speed of the wheel, and a Assuming that N pulse signals are output per sensor rotation, the vehicle speed is calculated from the moving average value of at least the latest N pulse periods of the pulse signals or the sum of at least the latest N pulse periods. A first means, a steering angle sensor that outputs a pulse signal at every fixed angle according to the rotation of the steering wheel, and outputs two pulse train signals with an electrical angle phase difference of about 90 degrees; a second means for calculating the sum of the steering angles at which the steering wheel rotates in the same direction based on the two pulse train signals and detecting the absolute value of the steering angle, the steering angle being determined according to the vehicle speed determined by the first means; A suspension system for an automobile, wherein the damping force and spring characteristics of the shock absorber are switched by comparing the absolute value of the steering angle detected by the second means.