JPH0474207B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydroneumatic suspension system for a vehicle.

[Prior art] Hydropneumatic suspension systems provide good ride comfort due to the softness of air springs, but on the other hand, when turning, the vehicle body tilts significantly due to the roll moment generated in the vehicle body, resulting in poor handling stability. The problem is that it is damaged.

Therefore, in the suspension system disclosed in Japanese Patent Application Laid-Open No. 51-60320, the spring constant of the air spring is changed based on the lateral acceleration and longitudinal acceleration acting on the vehicle body. At present, the electronic control device for obtaining the optimum spring constant is far from perfect.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, the purpose of the present invention is to take advantage of the soft riding comfort of air springs during normal driving, and to obtain roll rigidity that matches the vehicle body load conditions during cornering. An object of the present invention is to provide a hydroneumatic suspension system that suppresses a roll angle within a predetermined range.

[Means for Solving the Problems] In order to achieve the above object, the configuration of the present invention includes an air spring that is divided into an air chamber and an oil chamber by a diaphragm in the oil chamber of the hydraulic cylinder of the suspension system for each wheel. The oil chamber is connected to the air chamber of the air spring, and multiple air tanks are connected in series to each other and are disconnected from each other by electromagnetic on-off valves, and the load sensor and steering mechanism are installed to detect the oil pressure in the oil chamber of each hydraulic cylinder. Based on the output of the electronic control device based on the signal from the steering angle sensor, the number of electromagnetic on-off valves proportional to the steering angle and the load are closed in the order of distance from the air spring.

[Function] As the steering angle increases and the load increases, the air The electromagnetic on-off valves farthest from the spring are closed in sequence. Therefore, when the vehicle is turning, the spring constant of the air spring of the suspension system for each wheel gradually increases, and roll of the vehicle body is suppressed.

During normal driving, all electromagnetic on-off valves are open and the spring constant of the air spring is small, providing the soft ride characteristic of air springs.

[Embodiments of the Invention] As shown in FIG. 1, a hydropneumatic suspension system 1 includes a hydraulic cylinder in which a piston 8 is fitted into a cylinder 7, and a diaphragm 3 to partition an oil chamber 9 and an air chamber 11. It is equipped with an air spring. A rod 10 connected to the piston 8 is connected to a control arm 13. The control arm 13 has its base end connected to the vehicle body 20 with a support shaft 28.
The wheel 6 is swingably supported by the wheel 6, and the tip supports the wheel 6 via a known knuckle. The oil chamber 9 is connected by a conduit 21 to a hydraulic pressure regulator 19 . From the oil pressure in the conduit 21, the load sensor 18 detects the vehicle body load that each wheel is responsible for.

In order to change the volume of the air chamber 11 and adjust the spring constant, a first air tank 2 is connected to the air chamber 11 via an electromagnetic on-off valve 14, and a second air tank is connected via an electromagnetic on-off valve 15 to the air chamber 11.
The third air tank 2a is further connected in series with a third air tank 2b via an electromagnetic on-off valve 16.
The electromagnetic on-off valves 14, 15, and 16 are opened and closed by an output signal from an electronic control device 30 that receives a signal from a load sensor 18 as an input.

Although only the suspension system for the front wheels of the vehicle body is shown in FIG. 1, the suspension system for the rear wheels is similarly constructed, and the electromagnetic on-off valves 14, 15, 16 are controlled by a common electronic control unit 30.

As shown in FIG. 2, the electronic control unit 30 is composed of a microprocessor 32, a memory 33, and an interface 31. The interface 31 detects the vehicle body load of each wheel detected by the load sensor 18 of each suspension system 1 of the front wheel and rear wheel.
The signal is input as a digital signal by the converter 34. The interface 31 also includes a steering angle sensor 37.
The steering angle (turning angle) of the steering wheel 36 detected by
is input as a digital signal by the AD converter 38.

As shown by lines 42 and 41 in FIG. 3, respectively,
The ROM of the memory 33 stores the roll stiffness during straight running and the roll stiffness required during turning with respect to the vehicle body load carried by each wheel as a control map. Further, as shown by a line 43 in FIG. 4, the ROM of the memory 33 stores a control map of the roll rigidity R (see FIG. 3) that should be controlled during cornering with respect to the vehicle body load that each wheel is responsible for.
Appropriate roll stiffness is determined based on the signal from the load sensor 18 corresponding to the vehicle body load carried by each wheel from the above-mentioned control map, and one or more of the electromagnetic on-off valves 14, 15, 16 are opened and closed for each wheel. configured to do so. In other words, when the car body load is the minimum (empty car), the electromagnetic on-off valve 16 is closed, when it is medium, the electromagnetic on-off valve 15 is closed, and when it is the maximum, the electromagnetic on-off valve 14 is closed, and the spring constant of the air spring is increased. Increase roll rigidity.

FIG. 5 shows a flowchart of the control program described above. In the figure, p11 to p23 indicate each step of the flowchart. At the same time as the engine starts, the calculation part is p11, p12 opens the electromagnetic on-off valve 16, p13 opens the electromagnetic on-off valve 15, p14 opens the electromagnetic on-off valve 14, and the soft ride of the air spring is maintained during normal running. Stay comfortable.

At p15, it is determined whether the steering angle of the steering wheel is greater than or equal to a predetermined value (for example, 20°). If the steering angle of the steering wheel is less than the predetermined value, return to p12. If the steering wheel angle is equal to or greater than a predetermined value in p15, it is determined in p16 whether the vehicle body load shared by the front, rear, left, and right wheels is the minimum (empty vehicle). When the vehicle body load is minimum, use p17 to turn on solenoid valve 1.
Close 6 and return to p15.

If the vehicle body load handled by each wheel is not the minimum in p16, it is determined in p18 whether the vehicle body load handled by each wheel is medium. If the vehicle body load carried by each wheel is moderate, the electromagnetic on-off valve 16 is closed at p19, the electromagnetic on-off valve 15 is closed at p20, and the process returns to p15.

If the vehicle body load carried by each wheel is more than medium in p18, close the electromagnetic on-off valve 16 on p21, close the electromagnetic on-off valve 15 on p22, close the electromagnetic on-off valve 14 on p23, and return to p15. In this way, the steering angle of the steering wheel is detected at predetermined time intervals, and the roll stiffness is obtained in accordance with the steering angle of the steering wheel.

In the above embodiment, the roll stiffness is controlled based on the steering angle of the steering wheel, but if the roll stiffness is calculated based on the vehicle speed signal and the steering angle of the steering wheel, the time lag in control with respect to the steering wheel operation can be reduced. can be eliminated.

[Effects of the Invention] As described above, the present invention allows the oil chamber of the air spring, which is divided into an air chamber and an oil chamber by a diaphragm, to communicate with the oil chamber of the hydraulic cylinder of the suspension system for each wheel,
A plurality of air tanks are connected in series to the air chamber of the air spring, and the communication is cut off by electromagnetic on-off valves.A load sensor that detects the oil pressure in the oil chamber of each hydraulic cylinder and a steering angle sensor installed in the steering mechanism are connected in series to the air chamber of the air spring. The number of electromagnetic on-off valves proportional to the steering angle and load are closed in the order of distance from the air spring by the output of the electronic control device based on the signal.

Therefore, even when turning on the same road, the roll angle changes depending on load conditions such as the number of passengers, but the electromagnetic on-off valves close in sequence depending on the load conditions, and the spring constant of the air spring in the suspension system of each wheel increases. As a result, the tilt of the vehicle body is suppressed and stable handling performance is achieved. On the other hand, when driving straight, the electromagnetic on-off valves open in sequence and the spring constant of the air spring becomes smaller.
Provides a soft and comfortable ride unique to air springs.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a schematic structure of a hydroneumatic suspension system according to the present invention, FIG. 2 is a block diagram showing a schematic structure of the same suspension system, and FIGS. 3 and 4 are electronic diagrams of the same suspension system. A diagram representing a control map stored in the memory of the control device, and FIG. 5 is a flowchart of a program for controlling the same suspension system. 1... Suspension device, 2, 2a, 2b... Air tank,
7...Cylinder, 8...Piston, 13...Control rod, 14, 15, 16...Solenoid on-off valve, 18...Load sensor, 19...Hydraulic pressure adjustment device, 30...Electronic control device, 37... ...Rudder angle sensor.

Claims (1)

[Claims] 1 In the oil chamber of the hydraulic cylinder of the suspension system of each wheel,
The oil chamber of the air spring, which is divided into an air chamber and an oil chamber, is communicated with each other by a diaphragm, and a plurality of air tanks, which are communicated with each other by electromagnetic on-off valves, are connected in series to the air chamber of the air spring. Based on the output of an electronic control device based on signals from a load sensor that detects oil pressure in the oil chamber and a steering angle sensor installed in the steering mechanism, a number of electromagnetic on-off valves proportional to the steering angle and load are activated in the order of distance from the air spring. A hydroneumatic suspension system characterized by a closing feature.