JPS6341217Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a suspension device used in vehicles such as automobiles.

In recent years, in addition to coil springs that absorb shocks caused by the vertical movement of wheels and shock absorbers that quickly remove bounce caused by expansion and contraction of the coil springs and stabilize the vehicle body by applying damping force, suspension devices that have air springs have been developed. The main purpose of air springs is to maintain a constant vehicle height regardless of the load by increasing or decreasing the internal air pressure depending on the number of occupants or the load.

FIG. 1 is a side view schematically showing a mechanical part (hereinafter referred to as a suspension body) of a conventional suspension device. The illustrated suspension device includes a strut-type damping force switching type shock absorber 11, a coil spring 12, and a rolling diaphragm type air spring 13. 15, the amount of compressed air in the air chamber 16 can be adjusted. Through this adjustment, the internal pressure of the air chamber 16 can be adjusted, and the vehicle height can be kept constant.

Coil spring 12 and air spring 13 as described above
In the case of a suspension device with
In addition to the spring constant of the air spring 13, the spring constant of the air spring 13 is also relevant.

According to the conventional suspension -wine device, two springs 12, such as extending air springs 13 when coil springs 12 extends to shocks due to the up and down movement of the wheels, and shrinking air springs 13 when the coil spring 12 shrinks. The expansion and contraction operations of No. 13 are the same. Therefore, there was a problem in that the composite spring constant of the two springs 12 and 13 could not be made smaller than the spring constant of the coil spring 12 alone.

This invention was made in order to deal with the above-mentioned circumstances, and it is an object of the present invention to provide a suspension device in which the composite spring constant of two springs, a coil spring and an air spring, can be made equal to or less than the spring constant of the coil spring alone. With the goal.

Hereinafter, one embodiment of this invention will be described in detail with reference to the drawings.

FIG. 2 is a side view showing the suspension main body portion of one embodiment. . In the figure, 21 is a cross member on the vehicle body side, and 22 is the vehicle body frame. 23 is a lower arm. One end of the lower arm 23 is rotatably supported by the cross member 21, and the other end is connected to a bearing 242 of a king pin (rotating shaft) 241 of the wheel 24 via a joint mechanism 25. The lower arm 23 rotates about a pivot point on the cross member 21 in accordance with changes in load such as changes in static load and load fluctuations during running.

26 is a shock absorber whose cylinder 2
A base end portion of 61 is connected to the bearing 242. 27 is a coil spring, one end of which is fixed to a spring receiver 28 provided on the cylinder 261 of the shock absorber 26, and the other end of which is fixed to the spring receiver 28 provided on the cylinder 261 of the shock absorber 26.
It is fixed to a spring receiver 30 provided on a piston rod 29 connected to the piston. The upper end of the piston rod 29 is connected to the vehicle body frame 22 via a mount rubber 31.

32 is a bellows type air spring. The upper end of the air spring 32 in the figure is connected to the lower arm 23, and the lower end is connected to the spring receiver 33. This spring receiver 33 is fixed to the cross member 21 so as to be located below the lower arm 23.

By adjusting the amount of air in the air chamber of the air spring 32 to increase or decrease its internal pressure, the cylinder 261 can be moved up and down to adjust the vehicle height. In this case, the expansion and contraction movement of the air spring 32 with respect to the vertical movement of the cylinder 261 is opposite to that of the coil spring 27. That is, when the cylinder 261 moves upward in the figure relative to the piston rod 29,
The air spring 32 expands while the coil spring 27 contracts. Conversely, if it moves downward in the figure, coil spring 2
7 expands, while air spring 32 contracts. Therefore, when increasing the vehicle height, compressed air is discharged from the air chamber to lower the internal pressure, and when decreasing the vehicle height, compressed air is supplied to the air chamber to increase the internal pressure.

According to the above configuration, the coil spring 27 responds to changes in load such as changes in static load and load fluctuations during running.
The expansion and contraction operations of the air spring 32 and the expansion and contraction operations of the air spring 32 are reversed. Therefore, the combined spring constant of the coil spring 27 and the air spring 32 can be set to a value equal to or smaller than the spring constant of the coil spring 27 alone. In other words, making the composite spring constant equal to the spring constant of the coil spring 27 alone is as follows:
This is possible by keeping the internal pressure of the air spring 32 at a constant value regardless of the load applied to the suspension body. That is, by doing so, the spring constant of the air spring 32 can be made zero. The reason why the composite spring constant can be made smaller than the spring constant of the coil spring 27 alone is as follows. That is, in response to a contraction displacement of the coil spring 27, the compression stroke of the coil spring 27 can be assisted by increasing the internal pressure of the air spring 32 and stretching the air spring 32, and in response to an expansion displacement, the air spring 32 By lowering the internal pressure of the air spring 30 and compressing the air spring 30, the extension stroke of the coil spring 27 can be assisted.

Further, according to the above configuration, even if the compressed air in the air spring 32 escapes for some reason and the air spring 32 contracts, the vehicle height will not be lowered, so safety can be improved.

Here, a method of setting the internal pressure of the air spring 32 when the composite spring constant is made smaller than the spring constant of the coil spring 27 alone will be explained. In Figure 3a,
The characteristic curve Ca shows the spring characteristics of the coil spring 27 alone. If it is desired to change this spring characteristic to a spring characteristic having a spring constant (inclination) as shown by the characteristic curve Cb, it is sufficient to cause the air spring 32 to bear the load shown by diagonal lines.

Now, if the load W is _W1 on the characteristic curve Cb, the stroke S is _S1 . This stroke S ₁
The load borne by the air spring 32 to obtain W is W _A.
If this burden load W _A is converted into load/pressure, the internal pressure P ₁ of the air spring 32 for obtaining the stroke S ₁ can be obtained. By performing such conversion for each load W, it is possible to determine the spring characteristics of the air spring 32 to obtain the composite spring characteristics shown by the characteristic curve Cb. This is shown in FIG. 3b as a characteristic curve Cc. From FIGS. 3a and 3b, the relationship between the load W and the internal pressure P for obtaining preset composite spring characteristics can be determined, and the characteristics shown in FIG. 4 can be obtained.

Therefore, if the internal pressure P is memorized in accordance with the characteristics shown in FIG. 4, the composite spring characteristics having a predetermined spring constant can be reproduced by simply detecting the load W. In this case, by appropriately setting the load borne by the air spring 32 for each stroke, a composite spring constant having a value smaller than the spring constant of the coil spring 27 alone can be set in various ways.

In addition, in Fig. 3a, W ₀ is coil spring 2
When the coil spring 27 receives the load W alone, the coil spring 27
This is the load for setting the to the neutral position. Also,
X ₁ is a stop point that restricts the position of the coil spring 27 in the direction of contraction, and X ₂ is a full bound point in the direction of extension.

FIG. 5 is a diagram showing the configuration of the control system of the suspension main body described above.

In the figure, 42 is an actuator for switching the shock absorber 26 between hardware and software. . 43 is the vehicle height sensor,
44 is an internal pressure sensor that detects the internal pressure of the air spring 32, and 45 is a load sensor that detects the load W applied to the suspension body. This load sensor 45
is provided, for example, at the upper end of the piston rod 29. Since this portion is not easily affected by the impact caused by the vertical movement of the wheels 24, a substantially stationary load can be detected as long as the vehicle body does not move vertically.

Here, a configuration for obtaining a composite spring constant smaller than the spring constant of the coil spring 27 alone will be described.

51 indicates the air spring 3 from the load/internal pressure map 52 according to the load W detected by the load sensor 45.
This is an internal pressure setting circuit that reads data indicating the set internal pressure P of No. 2. The load/internal pressure map 52 includes the fourth
Data indicating the set internal pressure P according to the characteristic diagram shown in the figure is stored corresponding to each load W. 53 is a solenoid valve drive circuit that outputs the set internal pressure P read out by the internal pressure setting circuit 51 and the internal pressure sensor 44.
Compare the magnitude with the internal pressure Pa detected by
According to the comparison result, the air supply solenoid valve 54
and controls the opening and closing of the exhaust solenoid valve 55.
The air supply solenoid valve 54 is inserted into a communication path that communicates and connects a reserve tank 56 in which compressed air is stored and an air inlet of the air spring 32. The exhaust solenoid valve 55 is inserted into a communication path that connects an exhaust pipe 57 for discharging compressed air from the air chamber of the air spring 32 and an air inlet of the air spring 32 . Note that 58 is an internal pressure detection circuit that converts the internal pressure detected by the internal pressure sensor 44 into a signal that can be supplied to the solenoid valve drive circuit 53. Further, 59 is a pressure switch for detecting the internal pressure of the reserve tank 56 and maintaining it at a predetermined internal pressure, 60 is an engine, 61 is a compressor, and 62 is a dryer.

The operation of the above configuration will be explained with reference to the flowchart of FIG. In step _S1 , the internal pressure setting circuit 51 sets the load/internal pressure map 52 according to the load W detected by the load sensor 45.
Data indicating the set internal pressure P is read out from. (See step _S2 ) The internal pressure setting circuit 51 further converts this read data into a signal that can be supplied to the solenoid valve drive circuit 53. The solenoid valve drive circuit 53 compares the set internal pressure P and the actual internal pressure Pa of the air spring 32 based on the set internal pressure signal supplied from the internal pressure setting circuit 51 and the internal pressure signal supplied from the internal pressure detection circuit 58. (See step _S3 ) If the internal pressure Pa is smaller than the set internal pressure P, only the air supply solenoid valve 54 is opened. As a result, compressed air is sent from the reserve tank 56 to the air spring 32, and the internal pressure Pa of the air spring 32 is increased. (See step _S4 ) If the internal pressure Pa is greater than the set internal pressure P, only the exhaust solenoid valve 55 is opened. As a result, the compressed air of the air spring 32 is discharged from the exhaust pipe 57, and the internal pressure of the air spring 32 is
Pa is reduced. (See step _S5 ) Then, when the internal pressure Pa becomes equal to the set internal pressure P, the air supply solenoid valve 54 and the exhaust solenoid valve 5
Close all of 5. (Refer to step S ₆ ) After this, if the set internal pressure P does not change, the internal pressure sensor 4
4, the internal pressure Pa is maintained at the set internal pressure P. When the static load changes or the detected load W changes due to load fluctuations during driving, the new load W is calculated from the load/internal pressure map 52 according to the above-mentioned operation.
The set internal pressure P corresponding to the new set internal pressure P is read out, and control is performed to make the internal pressure Pa equal to the new set internal pressure P. . Therefore, the suspension body exerts a damping force in accordance with the spring characteristics having a preset spring constant.

Note that regardless of the load W, the solenoid valve drive circuit 53 always sends a signal indicating the same set internal pressure P.
, the spring constant of the air spring 32 becomes zero, and the same composite spring constant as the spring constant of the coil spring 27 can be obtained. However, in this case, the spring characteristics are obtained by translating the spring characteristics of the coil spring 27 along the vertical axis (the axis indicating the load W).

Next, the configuration of the part that adjusts the vehicle height to obtain the target vehicle height will be explained.

71 is a vehicle height manual switch for selecting the vehicle height: "LOW", "MIDDLE", "HIGH",
You can select from four modes: ``AUTO.'' 72 is the target vehicle height setting circuit, "LOW",
When either "MIDDLE" or "HIGH" mode is selected, a vehicle height signal indicating the target vehicle height corresponding to that mode is output. A vehicle height signal comparison circuit 73 compares the target vehicle height with the actual vehicle height based on the target vehicle height signal and the vehicle height signal indicating the actual vehicle height supplied from the vehicle height sensor 43. 74 is an internal pressure correction signal generation circuit. This internal pressure correction signal generation circuit 74 generates a signal indicating a correction internal pressure for correcting the difference between the vehicle height set by the set internal pressure P and the target vehicle height according to the comparison result of the vehicle height signal comparison circuit 73. This is generated and supplied to the informal offer setting circuit 51.
The internal pressure setting circuit 51 synthesizes this internal pressure correction signal and the set internal pressure signal and supplies it to the solenoid valve drive circuit 53 as a target internal pressure signal indicating the target internal pressure for obtaining the target vehicle height.

The operation in the above configuration will be explained. Set vehicle height manual switch 71 to ``LOW'', ``MIDDLE'',
When one of the “HIGH” modes is selected,
A target vehicle height signal corresponding to the selected mode is output from the target vehicle height setting circuit 72, and a vehicle height signal comparison circuit 73 compares the target vehicle height with the actual vehicle height. Then, according to the comparison result, an internal pressure correction signal is output from the internal pressure correction signal generation circuit 74,
A target internal pressure signal obtained by combining the internal pressure correction signal and the set internal pressure signal is supplied from the internal pressure setting circuit 51 to the solenoid valve drive circuit 53. Thereby, the internal pressure Pa of the air spring 32 is set to the target internal pressure, and the target vehicle height is obtained.

Even in this case, if the detected load W fluctuates due to load fluctuations during driving, for example, the load/internal pressure map 5
Since the set internal pressure P read from 2 is changed, the target internal pressure is changed. Therefore, the suspension body has a spring constant according to the characteristic curve Cb shown in FIG. 3a. However, in this case, since the load borne by the air spring 32 changes by the corrected internal pressure indicated by the internal pressure correction signal, the spring characteristics are obtained by translating the characteristic curve Cb along the vertical axis (the axis indicating the load W).

Set vehicle height manual switch 71 to “AUTO”
When mode is selected, the target vehicle height setting circuit 72 does not output a target vehicle height signal, so the internal pressure correction signal generating circuit 74 also does not output an internal pressure correction signal. Therefore, in this case, the set internal pressure P
A vehicle height determined according to the characteristic curve Cb of FIG. 3a is obtained.

Note that the corrected internal pressure may be determined in the following manner instead of by comparing the vehicle height determined by the set internal pressure P with the target vehicle height. In other words, the set internal pressure when the detected load W is _W2
For P ₂ (see Figure 3 a and b), set the vehicle height to "MIDDLE". Therefore, the vehicle height manual switch 7
When one of the modes "LOW", "MIDDLE", and "HIGH" is selected in step 1, the internal pressure correction signal generation circuit 74 first outputs the target vehicle height and "MIDDLE".
The corrected internal pressure is output according to the difference between the vehicle height and the vehicle height. Thereafter, the vehicle height determined by the composite internal pressure of this corrected internal pressure and the set internal pressure P is detected by the vehicle height sensor 43, and a correction is output in advance according to the difference between this vehicle height and the target vehicle height. Change the internal pressure value. That is, when the load W is _W2 in advance, the grain correction internal pressure is generated, and then the value of the correction internal pressure is changed according to the actual load.

In this way, the time required to obtain the target vehicle height can be shortened. That is, air spring 3
Due to its nature, it takes a certain amount of time to take in and out the compressed air in step 2. Therefore, in the former method, in which the vehicle height cannot be adjusted until the vehicle height is determined by the set internal pressure P, it takes a considerable amount of time to obtain the target vehicle height. On the other hand, in the latter method, when the vehicle height manual switch 71 is operated, the vehicle height is adjusted directly, so the actual load W is the load
As long as it does not deviate significantly from W ₂ , it is possible to directly obtain a vehicle height close to the target vehicle height.

Next, the configuration of the portion of the shock absorber 26 that performs hardware/software switching will be explained.

81 is shock absorber 26 “HARD”,
This is a suspension manual switch for selecting three modes: ``SOFT'' and ``AUTO.''
When each mode is selected, “H” is output from the corresponding terminal.
A level signal is output.

82 is a speed sensor that detects vehicle speed. The output signal of this speed sensor 82 is supplied to a threshold value determination circuit 83 which outputs an "H" level signal when the vehicle speed exceeds a certain speed.

A handle angle sensor 84 detects the rotation angle and angular velocity of the handle. The output signal of the steering wheel angle sensor 84 is supplied to a threshold value determining circuit 85 which outputs an "H" level signal when the rotation angle or angular velocity of the steering wheel exceeds a certain angle or a certain angular velocity.

Reference numeral 86 denotes an acceleration sensor as a vehicle body attitude sensor that detects changes in the attitude of the vehicle body. This acceleration sensor 86 is designed to detect changes in pitch, roll, and yaw of the vehicle body posture on the automobile springs using a weight or the like. When acceleration acts in the front and back, left and right, or up and down directions, the weight tilts or moves, which is used to detect the acceleration of the vehicle body. The output signal of the acceleration sensor 86 is supplied to a threshold value determination circuit 87 which outputs an "H" level signal when the acceleration of the vehicle body exceeds a certain value.

88 is an accelerator opening/closing speed sensor that detects the opening/closing speed of the accelerator. The output signal of the accelerator opening/closing speed sensor 88 is supplied to a threshold value determination circuit 89 which outputs an "H" level signal when the accelerator opening/closing speed exceeds a certain value.

90 is a brake pressure sensor that detects the degree of depression of the brake. The output signal of this brake pressure sensor 90 is supplied to a threshold value determination circuit 91 which outputs an "H" level signal when the degree of depression of the brake exceeds a certain value.

The threshold value determination circuits 83, 85, 87, 8
The output signals of 9 and 91 are each supplied to one input terminal of an AND circuit 93 via an OR circuit 92. The other input terminal of this AND circuit 93 has
An "H" level signal that is output when the "SOFT" mode is selected in the suspension manual switch 81 is supplied via an inverter circuit 94. The output signal of the AND circuit 93 and the "H" level signal that is output when the "HARD" mode is selected in the suspension manual switch 81 are passed through the OR circuit 95 to a solenoid valve for damping force switching. Drive circuit 9
6.

The output signal of the solenoid valve drive circuit 96 is supplied to an air supply/exhaust solenoid valve 97 for switching damping force. This supply/exhaust solenoid valve 9
7 is the actuator 42 and the reserve tank 5
6 and an exhaust pipe 98.

The operation in the above configuration will be explained. When the "HARD" mode is selected by the suspension manual switch 81, an "H" level signal is supplied to the solenoid valve drive circuit 96 via the OR circuit 65. Thereby, the solenoid valve drive circuit 96 drives the air supply/exhaust solenoid valve 97 so that compressed air is supplied from the reserve tank 56 to the actuator 42 . This sets the hard state.

In addition, the shock absorber 26 is operated by various sensors 8 when the suspension manual switch 81 selects the "AUTO" mode.
Threshold determination circuits 83, 85, 87, to which the levels of the output signals of 2, 84, 86, 88, 90 correspond.
Even when the thresholds 89 and 91 are exceeded, "H" level signals are output from these circuits 83, 85, 87, 89, and 91, so that the hard state is set.

On the other hand, suspension manual switch 81
When the "SOFT" mode is selected, the AND circuit 93 closes the gate. Therefore, the input signal to the solenoid valve drive circuit 96 is at the "L" level regardless of the driving state. The solenoid valve drive circuit 96 drives the solenoid valve 97 so that the compressed air of the actuator 42 is discharged from the exhaust pipe 98 when the input signal is at the "L" level. As a result, the shock absorber 26 is set to a soft state. .

Note that the air spring is not limited to the bellows type air spring, and of course, for example, a rolling diaphragm type air spring may be used.

Further, to control the amount of air in the air spring 32, an electropneumatic proportional valve 101 may be used instead of the solenoid valve, as shown in FIG. In this case, an electropneumatic proportional valve drive circuit 102 is provided in place of the solenoid valve drive circuit 53, and the internal pressure sensor 44 and internal pressure detection circuit 58 are not required. 8th
The figure shows a flowchart of the control operation. step
The load W is detected in step S ₁ , and the set internal pressure P is set in step S ₂ .
is loaded. Then, in step _S3 , a control voltage V corresponding to the set internal pressure P is output from the electro-pneumatic proportional valve drive circuit 102 and supplied to the control terminal of the electro-pneumatic proportional valve 101. As a result, the internal pressure of the air spring 32
Pa is made equal to the set internal pressure P.

As described above, according to this invention, it is possible to provide a suspension device in which the composite spring constant of the coil spring and the air spring can be set to a value equal to or less than the composite spring constant of the coil spring alone.

[Brief explanation of the drawing]

FIG. 1 is a side view showing the suspension body of a conventional suspension device, FIG. 2 is a side view showing the suspension body of an embodiment of the suspension device according to this invention, and FIGS. 3 and 4 are Figure 5 is a characteristic diagram to explain how to determine the set internal pressure of the air spring in order to obtain preset composite spring characteristics. FIG. 6 is a flowchart for explaining the operation for obtaining preset composite spring characteristics, FIG. 7 is a diagram showing the configuration of the main part of another embodiment of this invention, and FIG. This is a flowchart for explaining the operation of FIG. 7. 21...Cross member, 22...Vehicle frame, 23...Lower arm, 24...Wheel, 25...
...Joint mechanism, 26...Shock absorber, 27...Coil spring, 28...Spring receiver, 2
9...Piston rod, 30...Spring receiver, 31
...Mount rubber, 32...Air spring, 33...
Spring receiver, 44...Internal pressure sensor, 45...Load sensor, 51...Internal pressure setting circuit, 52...Load/internal pressure map, 53...Solenoid valve drive circuit,
54... Air supply solenoid valve, 55... Exhaust solenoid valve, 56... Reserve tank, 57
... Exhaust pipe, 58 ... Internal pressure setting circuit, 101 ...
Electro-pneumatic proportional valve, 102...Electro-pneumatic proportional valve drive circuit.

Claims (1)

[Scope of utility model registration request] A coil spring that expands and contracts according to changes in load; a rotating member that has one end rotatably supported on a vehicle body and the other end connected to a wheel and that rotates according to changes in load; On the other hand, a suspension device comprising an air spring that is connected to the rotating member and the vehicle body and whose air amount can be adjusted so as to obtain an expansion and contraction operation opposite to that of the coil spring.