JPH0462886B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention adjusts the spring constant of an air spring according to the magnitude of the load (spring mass) applied by the occupant, etc. to obtain a stable ride. , relates to a hydroneumatic suspension system for a vehicle.

[Prior art] Conventional hydraulic suspension systems include, for example, the
As seen in Publication No. 14005, it has been proposed to suppress the tilt of the vehicle body in response to changes in driving conditions, but it has been proposed that the spring constant of the air spring be adjusted in response to the load. Not blooming. In other words, the spring constant of the air spring and the damping force of the hydraulic cylinder unit, which affect the ride comfort of the vehicle, are preset to characteristics corresponding to the average load, so the optimum ride comfort can be achieved regardless of changes in the load. Can't keep it.

In particular, suspension systems using air springs have the characteristic that the spring constant increases rapidly with respect to the deflection of the air spring, so if the applied load increases, the riding comfort deteriorates, and if the applied load decreases, the spring constant increases rapidly. The disadvantage is that the constant becomes too small and the roll rigidity decreases too much.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, an object of the present invention is to increase or decrease the number of air springs connected to the oil chamber of a hydraulic cylinder unit according to the applied load (spring mass load), and to increase or decrease the number of air springs connected to the oil chamber of a hydraulic cylinder unit. An object of the present invention is to provide a hydroneumatic suspension system that provides stable riding comfort by correcting the spring constant of a spring.

[Means for Solving the Problem] In order to achieve the above object, the configuration of the present invention connects the oil chambers of a plurality of air springs, each of which is partitioned into an air chamber and an oil chamber by a diaphragm, to the oil chamber of each suspension cylinder. , an electromagnetic on-off valve is inserted and connected to the passage connecting the oil chamber of each air spring and the oil chamber of the suspension cylinder, and the signal value of the load sensor that detects the sprung mass load and the standard load from the signal generator are Based on the output of the control device based on the corresponding reference value, the number of electromagnetic on-off valves to be closed when the signal value of the load sensor is greater than the reference value is determined according to the difference between the signal value of the load sensor and the reference value. This will increase the number of people.

[Operation] According to the present invention, the number of air springs connected to the suspension cylinders of the hydropneumatic suspension system is adjusted according to the applied load on the vehicle body detected by the load sensor, so that the spring constant of the air springs is adjusted. For example, in a passenger car, it is adjusted to suit the number of passengers.

[Embodiments of the Invention] As shown in FIG. 1, the present invention provides a suspension cylinder 7 of a hydraulic cylinder unit that supports each wheel 14.
is connected to a pressure accumulator 36 or an oil tank 31 as a hydraulic pressure source by an electromagnetic directional switching valve 37 to adjust the amount of oil, and the suspension cylinder 7 is connected to the oil chamber 5 of the air spring 2 via a throttle 30. One or more air springs 2A are connected in parallel with the air spring 2 via an electromagnetic on-off valve 21.

Suspension cylinder 7 of left and right hydraulic cylinder units
The load sensor 16 detects the applied load from the oil pressure at the throttle 38 that connects the
6 and a signal corresponding to the set load from the signal generator 20 are compared in the control device 27,
The electromagnetic on-off valve 21 is opened and closed according to the applied load, and the spring constant of the air spring is made suitable for the applied load, thereby improving riding comfort. Specifically, when the signal value of the load sensor that detects the sprung load is larger than the reference value corresponding to the standard load from the signal generator, the number of electromagnetic on-off valves that close is determined by the signal value of the load sensor. and the reference value.

The configuration of the present invention will be explained based on an example.
As shown in FIG. 2, the hydroneumatic suspension system 1 includes a hydraulic cylinder unit consisting of a suspension cylinder 7 and a piston 8. As shown in FIG. The upper end of the suspension cylinder 7 is supported by a suitable means on the vehicle body, while the lower end of a rod 10 connected to the piston 8 is connected to the lower arm 13 by a ball joint.
The lower arm 13 has a pin 2 whose base end extends in the front-rear direction.
9 is supported by the vehicle body, while the tip side supports a wheel 14 via a known knuckle.

The air spring 2 for elastically supporting the piston 8 with respect to the vehicle body has a box whose inside is partitioned into an oil chamber 5 and an air chamber 3 by a diaphragm 4. The oil chamber 9 of the suspension cylinder 7 is throttled 3 into the oil chamber 5 of the air spring 2.
0.

According to the present invention, the normally closed electromagnetic on-off valves 21 and 22 are inserted and connected to the passages connecting the oil chambers 5 of the air springs 2A and 2B and the oil chambers 5 of the air springs 2, and the solenoid valves 21a and 22a are connected to each other. When energized, the spool moves and the air spring 2 is connected to each of the air springs 2A and 2B.

Although only the suspension system 1 for the left front wheel 14 is shown in FIG. 2, the right front wheel has a similar configuration, and the oil chambers 9 of both suspension cylinders 7 communicate with each other through a conduit 17 and a throttle 38. This is designed to maintain a balance between the left and right heights and to suppress body roll when turning.

The conduit 17 is connected to the pressure accumulator 3 by the electromagnetic directional valve 37.
6 or oil tank 31. The electromagnetic directional switching valve 37 is a neutral position port block type, and is normally set to the neutral position by a return spring 39. When the solenoid 37a is energized, the conduit 17 is connected to the pressure accumulator 36, and when the solenoid 37b is energized, the conduit 17 is connected to the pressure accumulator 36. 17 are connected to the oil tank 31, respectively.

The pressure accumulator 36 is filled with pressure oil from the hydraulic pump 32 via the check valve 34. When the pressure in the pressure accumulator 36 exceeds a predetermined value, the pressure oil discharged from the hydraulic pump 32 is returned to the oil tank 31 via the relief valve 33.

Although not shown, for the left and right rear wheels, a conduit 18 connected to the pressure accumulator 36 and a conduit 1 connected to the oil tank 31
9 is selectively connected to the oil chamber of the suspension cylinder of the hydraulic cylinder unit via an electromagnetic directional control valve similar to the electromagnetic directional control valve 37.

The connecting member 41 and pin 4 are attached to the left and right lower arms 13.
A stabilizer 45 consisting of a rod bent into a U-shape is connected via 2. The center portion of the stabilizer 45 is supported by the vehicle body by a rubber bushing or the like. Stabilizer 45 is for left and right wheels 1
It functions to balance the vertical vibrations of 4 and also rotates as the vehicle height changes. A rod 43 is connected to the tip of an arm 44 connected to the stabilizer 45, and vertical displacement of the rod 43 as the stabilizer 45 rotates is detected by a vehicle height sensor 12 comprising a potentiometer or the like.

In order to detect the load of the vehicle from the oil pressure in the oil chamber 9 of each suspension cylinder 7, a load sensor 16 is preferably installed at the throttle 38.

In the embodiment of the present invention, the air spring 2 is connected to the oil chamber 9 of the suspension cylinder 7 via the throttle 30 for medium loads, and is preset to obtain the optimum spring constant. Based on the signal from the load sensor 16, the electromagnetic on-off valves 21 and 22
connects one or both of the air springs 2A and 2B to the air spring 2 to correct the spring constant, and further drives the electromagnetic directional control valve 37 based on the signal from the vehicle height sensor 12 to adjust the vehicle height to a predetermined value. It is to be maintained at a height of .

The above-mentioned control device is performed by, for example, a microcomputer 65. microcomputer 65
is composed of a microprocessor 66, a memory 67, and an interface 68. In the interface 68, the load detected by the load sensor 16 is inputted as a digital signal by the AD converter 26, and the vehicle height detected by the vehicle height sensor 12 is inputted as a digital signal by the AD converter 25.

The ROM of the memory 67 stores in advance a signal from the outside to set the vehicle height to an arbitrary height, for example, three levels: high, medium, and low. Also, the memory 67
ROM has a first signal corresponding to a reference oil pressure P1 that is somewhat larger than the medium applied load, and a second signal that corresponds to a standard oil pressure P2 that is somewhat smaller than the medium applied load.
The signal is memorized and set. Signals corresponding to the first and second reference oil pressures P1 and P2 and the load sensor 1
6, each electromagnetic on-off valve 21, 22 is operated.

FIG. 3 shows a flowchart of the program described above. In the figure, p12 to p28 indicate each step of the flowchart. At the same time as the engine starts, the calculation part is set to p12,
The control program is repeatedly executed at predetermined time intervals. On page 13, use the operation button on the driver's seat to set the standard vehicle height to high, medium, or low depending on the road conditions. At p14, the signal from the vehicle height sensor 12 is read continuously. At p15, the change in vehicle height detected by the vehicle height sensor 12 is integrated over a predetermined period of time to obtain the average vehicle height h.

In p16, compare the average vehicle height h with the reference vehicle height selected in p13. If the average vehicle height h is higher than the reference vehicle height, the solenoid 37b of the electromagnetic directional control valve 37 is energized in p17, and the hydraulic oil in the oil chamber 9 of the suspension cylinder 7 is returned to the oil tank 31 to lower the vehicle height. Return to p14 and read the signal of the vehicle height sensor 12 repeatedly.
Hereinafter, the average vehicle height h and the reference vehicle height are compared in the same way as in the case described above.

If the average vehicle height h is lower than the standard vehicle height in p16, the solenoid 37 of the electromagnetic directional control valve 37 in p18
a is excited, pressure oil is supplied from the pressure accumulator 36 to the oil chamber 9 of the suspension cylinder 7 through the electromagnetic directional control valve 37 to raise the vehicle height, and the process returns to p14. Thereafter, the signal from the vehicle height sensor 12 is repeatedly read, and the average vehicle height h is compared with the reference vehicle height as in the case described above.

If the average vehicle height h and the reference vehicle height are almost equal in p16, each solenoid 3 of the electromagnetic directional control valve 37 is set in p19.
7a and 37b to maintain the vehicle height at that height.

Next, at p20, the signal from the load sensor 16 is read, and at p21, it is integrated for a predetermined time to determine the average oil pressure P. At p22, it is determined whether the average oil pressure P is higher than the first reference oil pressure P1. When the average oil pressure P is higher than the first reference oil pressure P1 (including when it is equal to it), the solenoids 21a and 22a of the electromagnetic on-off valves 21 and 22 are energized in p23, and the air springs 2A and 2B are connected to the air springs 2. Connect and reduce the spring constant of the air spring, then proceed to page 27.

If the average oil pressure P is lower than the first reference oil pressure P1 at p23, it is determined at p24 whether the average oil pressure P is higher than the second reference oil pressure P2. When the average oil pressure P is higher than the second reference oil pressure P2 (including when it is equal to it), the solenoid 21a of the electromagnetic on-off valve 21 is energized at p25, the solenoid 22a of the electromagnetic on-off valve 22 is deenergized, and the air spring 2 Connect only air spring 2A to , increase the spring constant, and proceed to page 27.

If the average oil pressure P is lower than the second reference oil pressure P2 at p23, the solenoids 21a and 22a of the electromagnetic on-off valves 21 and 22 are demagnetized, only the air spring 2 is used, and the spring constant is further increased, and the process proceeds to p27.

At p27, it is determined whether a predetermined period of time has elapsed. If the predetermined time has not elapsed, wait for the time to elapse, and if the predetermined time has elapsed, end at p28. The above-described program is repeated.

In the above embodiment, if the hydraulic cylinder unit is of a type in which the oil chambers are partitioned by pistons at both ends of the suspended cylinder, a throttle is provided in the passage connecting the oil chambers at both ends, and the oil at the upper end of the suspended cylinder is separated. The chamber and the oil chamber of the air spring shall be in direct communication.

In addition, although the load sensor is used to detect the oil pressure at the restrictor that connects the suspended cylinders of the left and right hydraulic cylinder units, the applied load is also detected by means such as a resistance strain gauge interposed between the piston rod and the lower arm. It's okay.

[Effects of the Invention] As described above, the present invention connects the oil chambers of a plurality of air springs partitioned into air chambers and oil chambers by a diaphragm to the oil chamber of each suspension cylinder, and connects the oil chambers of each air spring and the suspension cylinder. A control device in which an electromagnetic on-off valve is inserted and connected to each passage connecting the oil chamber of the cylinder, and is based on the signal value of the load sensor that detects the spring load and the reference value corresponding to the standard load from the signal generator. The output increases the number of electromagnetic valves that close when the load sensor signal value is greater than the reference value in accordance with the difference between the load sensor signal value and the reference value. The effect of this can be obtained.

According to the present invention, the number of air springs connected to the suspension cylinders of the hydroneumatic suspension system is selected according to the increase or decrease in the applied load on the vehicle body detected by the load sensor, so that the spring constant of the air springs is For example, in a passenger car, it is adjusted to suit the number of passengers.

Regardless of changes in the load applied to the vehicle body, the natural frequency of the vehicle body remains almost constant, providing a stable ride at all times. Furthermore, since the roll rigidity of the vehicle body is obtained commensurate with the load applied to the vehicle body, stable maneuverability is obtained.

In other words, for example, if there are a small number of passengers, the air springs may be stiff and the ride may be uncomfortable, or if there are many passengers, the air springs may be too soft, resulting in a bumpy feeling in response to large amplitude road inputs. There are no defects.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a hydroneumatic suspension system according to the present invention, FIG. 2 is a configuration diagram of the same system, and FIG. 3 is a flowchart of a program for controlling the system. 1... Suspension device, 2... Air spring, 5, 9...
Oil chamber, 7...Suspension cylinder, 12...Vehicle height sensor, 16...Load sensor, 21, 22...Solenoid on-off valve, 21a, 21b, 37a, 37b...Solenoid, 31...Oil tank, 32... Hydraulic pump, 3
6...Pressure accumulator, 37...Solenoid directional control valve, 38...
...Aperture.

Claims (1)

[Claims] 1 Connect the oil chambers of multiple air springs, which are partitioned into air chambers and oil chambers by diaphragms, to the oil chambers of each suspension cylinder, and connect electromagnetic wires to the passages connecting the oil chambers of each air spring and the oil chamber of the suspension cylinder. An on-off valve is inserted and connected, and the signal value of the load sensor is set to the reference value by the output of the control device based on the signal value of the load sensor that detects the spring load and the reference value equivalent to the standard load from the signal generator. 1. A hydroneumatic suspension system characterized in that the number of electromagnetic on-off valves that are closed when the load is larger than the load sensor is increased in accordance with the difference between a signal value of a load sensor and a reference value.