JP7836166B2 - Suspension system - Google Patents

Description

This invention relates to a suspension system.

Various suspension systems have been proposed for four-wheeled vehicles, equipped with variable damping dampers interposed between the vehicle body and each of the four wheels, and controllers that control the damping force of each variable damper, with the aim of improving ride comfort and achieving a vehicle posture suitable for driving conditions.

In such a suspension system, the variable damping dampers positioned on each of the four wheels allow for adjustment of the damping force during extension and compression, and the controller independently controls the damping force of each variable damping damper (see, for example, Patent Document 1).

Japanese Patent Publication No. 2018-47723

In this type of suspension system, the damping force necessary to suppress vehicle body vibrations is applied to each variable damper using skyhook control. Therefore, the controller is equipped with three acceleration sensors to detect the vertical acceleration of the vehicle body directly above each of the four wheels, and four stroke sensors to detect the stroke of each variable damper. Furthermore, each variable damper is equipped with a solenoid valve that adjusts the valve opening pressure according to the amount of current supplied from the controller.

The controller calculates the vertical velocity of the vehicle body directly above each of the four wheels, obtained from three acceleration sensors, and multiplies this velocity by the skyhook damping coefficient to determine the damping force that each variable damper should exert. Furthermore, since the magnitude of the damping force exerted by each variable damper depends on the stroke speed, the controller differentiates the stroke displacement detected by the four stroke sensors to determine the stroke speed of each variable damper, and then calculates the amount of current to supply to the solenoid valve to output the damping force calculated above at that stroke speed. The controller is equipped with four drive circuits to drive the solenoid valves of each variable damper, and supplies current to the solenoid valves of each variable damper through these drive circuits according to the calculated current amount.

Thus, conventional suspension systems consist of variable damping dampers that allow adjustment of damping force on both the extension and compression sides, and a controller equipped with at least three acceleration sensors, four stroke sensors, and four drive circuits. While this system excels in its ability to precisely control the vehicle's posture by controlling the damping force of the four variable dampers, it is extremely expensive and can only be installed in high-end luxury cars.

Therefore, the present invention aims to provide an inexpensive suspension system capable of controlling the vehicle's posture.

To achieve the above objective, the suspension device of the present invention provides a vehicle having a vehicle body and front left and right wheel rows and rear left and right wheel rows , each having wheels on the left and right sides of the vehicle body, and includes a variable damping force damper interposed between the vehicle body and the wheels of the rear left and right wheel rows, which is capable of adjusting only the damping force on the extension side or the compression side, a passive damper interposed between the vehicle body and the wheels of the front left and right wheel rows, which is not capable of damping force adjustment, and a controller that controls the damping force of the variable damping force damper based on information collected by the vehicle V and obtained from the vehicle V. Furthermore, another suspension device of the present invention is provided for a vehicle having a vehicle body and wheels arranged in multiple rows in the longitudinal direction relative to the vehicle body, including one or more left and right wheel rows with wheels on each of the left and right sides of the vehicle body, and comprises a damping force variable damper interposed between the vehicle body and the wheels of at least one of the left and right wheel rows, and capable of adjusting only the damping force on the extension side or the compression side, and a controller that obtains information collected by the vehicle from the vehicle and controls the damping force of the damping force variable damper based on the information, wherein the damping force variable damper comprises a cylinder, a rod inserted into the cylinder so as to be movable in the axial direction, a piston inserted into the cylinder so as to be movable in the axial direction and connected to the rod, which divides the inside of the cylinder into an extension side chamber and a compression side chamber filled with liquid, and a damping force adjustment valve having a solenoid that can adjust in two stages the resistance to the flow of liquid passing through by turning the solenoid on and off, and each of the solenoids in the damping force variable damper is connected in series, and the controller has only one drive circuit that supplies power to the solenoids.

With this suspension system configuration, the variable damping force damper can only be adjusted for extension or compression. This simplifies and reduces the cost of the variable damping force damper, and since the controller adjusts the damping force of the variable damping force damper using information already collected by the vehicle, the suspension system does not need to possess its own sensors.

Furthermore, the variable damping damper in the suspension system may only allow adjustment of the extension damping force and may be interposed between the vehicle body and the wheels of the left and right rear wheel rows. With a suspension system configured in this way, the extension damping force of the variable damping damper can be made harder, thereby suppressing body roll during cornering and pitching during braking, while lowering the vehicle's center of gravity and stabilizing the vehicle's posture during driving, and suppressing deterioration of ride comfort during compression.

Furthermore, the variable damping damper may allow for two-stage damping force adjustment: a normal damping force and a harder damping force than the normal one. Since the configuration of the damping force adjustment valve of the variable damping damper 2 is simplified, the suspension system can be made even more inexpensive.

Furthermore, the variable damping damper in the suspension system comprises a cylinder, a rod inserted into the cylinder so as to be axially movable, a piston inserted into the cylinder so as to be axially movable and connected to the rod, which divides the cylinder into an extension chamber and a compression chamber filled with liquid, and a damping force adjustment valve having a solenoid that can adjust the resistance to the flow of the liquid passing through it in two stages by switching the power on and off to the solenoid. With a suspension system configured in this way, the configuration of the variable damping damper and controller becomes very simple, making it even more inexpensive.

Furthermore, each solenoid in the variable damping damper may be connected in series, and the controller may have only one drive circuit to supply power to the solenoids. This suspension system configuration offers the advantage of automatically performing a fail-safe mechanism in the event of a failure in one of the variable damping dampers.

Furthermore, the suspension system may include non-adjustable passive dampers interposed between the vehicle body and all wheels except those in the left and right wheel rows where variable damping dampers are installed. With this suspension system configuration, variable damping dampers are installed only in the left and right wheel rows necessary for controlling the vehicle's posture, while the remaining left and right wheel rows are equipped with passive dampers, which are less expensive than variable damping dampers. Therefore, the suspension system 1 can be made even more inexpensive.

Furthermore, the controller in the suspension system may control the damping force of the variable damper based on information that allows the system to determine at least one of the following from the vehicle: braking, acceleration, or cornering. A suspension system configured in this way can suppress pitching, rolling, or squat of the vehicle body.

Therefore, the suspension device of the present invention allows for control of the vehicle's posture and can be implemented at a low cost.

This is a diagram showing the configuration of a suspension system in one embodiment installed in a vehicle. This is a schematic longitudinal cross-section of a variable damping force damper. This is a schematic longitudinal cross-section of a passive damper. This shows an example of a controller configuration. This diagram shows a flowchart illustrating an example of the processing procedure of the arithmetic processing unit in the controller.

The present invention will be described below based on the embodiment shown in the figure. As shown in Figure 1, the suspension device 1 is configured for a vehicle V having a vehicle body B and wheels Wfr, Wfl, Wrr, Wrl arranged in two rows (front and rear) in the front-rear direction, arranged in left-right rows relative to the vehicle body B. It comprises: a variable damping force damper 2 interposed between the vehicle body B and the rear row wheels Wrr, Wrl; a passive damper 3 interposed between the vehicle body B and the front row wheels Wfr, Wfl; and a controller 4 for controlling the damping force of the variable damping force damper 2.

The following describes each part. In this embodiment, vehicle V is a four-wheeled vehicle equipped with wheels Wfl, Wfr, Wrl, and Wrr at four locations on the front, rear, left, and right sides of the vehicle body B. On the left and right sides of the vehicle body B, the wheels Wfl, Wfr and Wrl, Wrr are arranged in the left-right direction, forming left and right wheel rows, and the two left and right wheel rows formed by the wheels Wfl, Wfr and Wrl, Wrr are arranged in the front-rear direction relative to the vehicle body B. In this embodiment, since vehicle V is a four-wheeled vehicle, the wheels Wfl, Wfr of the front left and right wheel rows are referred to as the front wheels, and the wheels Wrl, Wrr of the rear left and right wheel rows are referred to as the rear wheels. Furthermore, when it is necessary to clearly distinguish between the left and right sides of the front and rear wheels, the front left wheel Wfl will be referred to as the front left wheel, the front right wheel Wfr as the front right wheel, the rear left wheel Wrl as the rear left wheel, and the rear right wheel Wrr as the rear right wheel, as needed.

In the suspension system 1 of this embodiment, the variable damping force dampers 2 are interposed between the vehicle body B and the rear row wheels Wrl and Wrr, which form the left and right wheel rows, in a pair in the left-right direction relative to the vehicle body B. Passive dampers 3 are interposed between the front row wheels Wfl and Wfr, which are the left and right wheel rows other than the rear row wheels Wrl and Wrr on which the variable damping force dampers 2 are installed, and the vehicle body B.

Furthermore, the left and right wheel rows, each containing two wheels on the left and right sides relative to the vehicle body B, may be provided in three or more rows per vehicle. The variable damping force damper 2 is interposed between the wheels of one or more left and right wheel rows and the vehicle body, and the passive damper 3 is interposed between the wheels of left and right wheel rows other than those on which the variable damping force damper 2 is provided and the vehicle body. Therefore, the variable damping force damper 2 may be interposed between all the wheels Wfl, Wfr, Wrl, Wrr of each left and right wheel row on the front and rear sides of vehicle V and the vehicle body B, or it may be interposed between the wheels Wfl, Wfr of the left and right wheel rows on the front side of vehicle V and the vehicle body B. Furthermore, if the variable damping force damper 2 is interposed between all the wheels Wfl, Wfr, Wrl, Wrr of each left and right wheel row on the front and rear sides of vehicle V and the vehicle body B, the passive damper 3 is not installed on vehicle V. Thus, the variable damping force dampers 2 are positioned in pairs on the left and right sides of the vehicle body B relative to the vehicle V, and are interposed between the wheels forming the left and right wheel trains and the vehicle body B. Therefore, the number of variable damping force dampers 2 installed on the vehicle V is always a multiple of two.

Vehicle V may have rows of wheels with only one wheel in the lateral direction of vehicle body B, in addition to the left and right wheel rows containing two wheels positioned on each side of vehicle body B. In this case, the variable damping dampers 2 should be installed on the left and right wheel rows with two wheels positioned on each side of vehicle body B. Therefore, if vehicle V is a three-wheeled vehicle with only one wheel in either the front or rear row, the variable damping dampers 2 should be installed on the left and right wheel rows with two wheels on each side of vehicle body B. In other words, with the rows of wheels on each side of vehicle body B being defined as the left and right wheel rows, vehicle V has a vehicle body B and wheels provided in multiple rows including one or more left and right wheel rows in the longitudinal direction relative to vehicle body B, and the variable damping dampers 2 should be interposed between vehicle body B and the wheels of at least one of the left and right wheel rows. In other words, when we say that a vehicle V has multiple rows of wheels, each containing one or more left and right wheel rows with wheels on each side of the vehicle body B, it means that the vehicle V has multiple rows of wheels in the longitudinal direction, and at least one of these rows is a left and right wheel row with wheels on each side of the vehicle body B. As mentioned above, the vehicle V may be a three-wheeled vehicle, a four-wheeled vehicle with wheels on the front, rear, left, and right sides of the vehicle body B, or even a vehicle with six or more wheels, each containing three or more left and right wheel rows in the longitudinal direction relative to the vehicle body B.

Furthermore, the vehicle V is equipped with sensors 51 that detect various information about the vehicle V, such as engine speed, vehicle speed, wheel speed, steering angle, acceleration, yaw rate, throttle opening, and brake on/off signals, and output measurement signals. It also has a CAN (Controller Area Network) bus 53 for exchanging information detected by the sensors 51 and for communication between the ECU (Electronic Control Unit) 52 and the controlled objects (not shown) of the ECU 52. In this way, information about the vehicle V detected by the mounted sensors 51 is transmitted to the CAN bus 53 via the ECU 52, making the information about the vehicle V available to the ECU 52 and the controlled objects (not shown) connected to the CAN bus 53.

Next, the variable damping damper 2, for example as shown in Figure 2, includes a cylinder 11, a rod 12 inserted into the cylinder 11 so as to be movable in the axial direction, a piston 13 inserted into the cylinder 11 so as to be movable in the axial direction and connected to the rod 12, which divides the inside of the cylinder 11 into an extension chamber R1 and a compression chamber R2 filled with liquid, an outer cylinder 14 that covers the outer circumference of the cylinder 11 and forms a reservoir R between itself and the cylinder 11, and an extension damping passage 15 that connects the extension chamber R1 and the compression chamber R2. The system includes a damping force adjustment valve DV provided in the extension damping passage 15, a compression passage 16 connecting the compression chamber R2 and the extension chamber R1, a check valve 17 for opening and closing the compression passage 16, a valve case 18 provided at the end of the cylinder 11 that separates the compression chamber R2 and the reservoir R, a compression damping passage 19 connecting the compression chamber R2 and the reservoir R, a base valve 20 provided in the compression damping passage 19, a suction passage 21 connecting the reservoir R and the compression chamber R2, and a suction check valve 22 provided in the suction passage 21.

The variable damping force damper 2 is installed at two locations between the vehicle body B and the rear wheels Wrl and Wrr, by connecting the rod 12 to the vehicle body B and the outer cylinder 14 to the rear wheels Wrl and Wrr.

As shown in Figure 2, the cylinder 11 is cylindrical, with a rod 12 slidably inserted into its upper inner circumference and an annular rod guide 23 fitted to guide the axial movement of the rod 12 relative to the cylinder 11. A valve case 18 is fitted to its lower inner circumference, and the cylinder 11, rod guide 23, and valve case 18 are housed within a bottomed cylindrical outer cylinder 14. These components—the cylinder 11, rod guide 23, and valve case 18—are fixed within the outer cylinder 14 by crimping the open end of the outer cylinder 14.

The extension damping passage 15 and the compression damping passage 16 are provided in the piston 13, and the check valve 17 and the damping force adjustment valve DV are also provided in the piston 13.

The damping force adjustment valve DV comprises a solenoid Sol and a valve body Vb that opens and closes the extension damping passage 15. More specifically, the damping force adjustment valve DV resists the flow of liquid from the extension chamber R1 to the compression chamber R2 via the extension damping passage 15. When the pressure in the extension chamber R1 exceeds the pressure in the compression chamber R2 and the difference between them reaches the valve opening pressure, the valve body Vb opens the extension damping passage 15, allowing the aforementioned liquid flow while resisting it. The damping force adjustment valve DV also closes the valve to block the flow of liquid attempting to move from the compression chamber R2 to the extension chamber R1 via the extension damping passage 15.

Furthermore, since the solenoid Sol biases the valve body Vb in the closing direction with the thrust it generates when energized, when the solenoid Sol is energized, the damping force adjustment valve DV increases the opening pressure, thereby increasing the resistance to the flow of liquid through the extension damping passage 15 from the extension chamber R1 to the compression chamber R2. Conversely, when the solenoid Sol is not energized, the damping force adjustment valve DV decreases the opening pressure compared to when the solenoid Sol is energized, thereby reducing the resistance to the flow of liquid through the extension damping passage 15 from the extension chamber R1 to the compression chamber R2. In this way, the damping force adjustment valve DV can switch the opening pressure between two levels, high and low, by turning the solenoid Sol on and off. Note that although the damping force adjustment valve DV described above can adjust the opening pressure between two levels, high and low, depending on whether the solenoid Sol is energized or not, it may also be a valve that changes the flow path area between two levels, high and low, depending on whether the solenoid Sol is energized or not. When adjusting resistance by changing the flow path area, the damping force adjustment valve DV may be configured, for example, to include a hole that constitutes part of the extension damping passage 15, a spool that adjusts the opening area of the hole, and a solenoid that drives the spool.

The rod 12 is cylindrical, and wiring 24 for supplying power to the solenoid Sol housed within the piston 13 is routed through the rod 12 to the outside of the variable damping damper 2. Each of the solenoid Sols of the multiple variable damping dampers 2 installed in the vehicle V is connected in series via wiring 24 and connected to the drive circuit 42 of the controller 4.

The check valve 17 opens when the pressure in the compression chamber R2 exceeds the pressure in the expansion chamber R1, allowing only the flow of liquid from the compression chamber R2 to the expansion chamber R1 via the compression passage 16. It closes to block the flow of liquid attempting to move from the expansion chamber R1 to the compression chamber R2 via the compression passage 16.

The pressure-side damping passage 19 and the suction passage 21 are provided in the valve case 18, and the base valve 20 and the suction check valve 22 are also provided in the valve case 18. The base valve 20 is designed to resist the flow of liquid from the pressure-side chamber R2 to the reservoir R via the pressure-side damping passage 19. When the pressure in the pressure-side chamber R2 exceeds the pressure in the reservoir R and the difference between them reaches the opening pressure, the valve opens, allowing the aforementioned liquid flow while resisting it. The base valve 20 also closes to block the flow of liquid attempting to move from the reservoir R to the pressure-side chamber R2 via the pressure-side damping passage 19. The base valve 20 may be a valve other than the one that opens and closes the pressure-side damping passage 19, such as an orifice or a choke.

The suction check valve 22 opens when the pressure in reservoir R exceeds the pressure in pressure chamber R2, allowing only the flow of liquid from reservoir R to pressure chamber R2 via the suction passage 21. It closes to block the flow of liquid attempting to move from pressure chamber R2 to reservoir R via the suction passage 21.

Furthermore, the fluid used in the variable damping force damper 2 can be hydraulic fluid, water, aqueous solution, or other liquids. Also, if the variable damping force damper 2 is filled with electroviscous fluid or magnetoviscous fluid as the liquid in the extension chamber R1, compression chamber R2, and reservoir R, the damping force adjustment valve DV may be equipped with a coil that applies an electric or magnetic field to the extension damping passage 15, and the resistance applied to the flow of the liquid through the extension damping passage 15 may be adjusted by controlling whether or not the coil is energized.

In the variable damping force damper 2 configured in this way, when the piston 13 moves upward relative to the cylinder 11 in the extension operation shown in Figure 2, the pressure in the extension chamber R1, which is compressed by the piston 13, rises and exceeds the pressure in the compression chamber R2, which is expanded. When the pressure difference between the two reaches the valve opening pressure, the damping force adjustment valve DV opens, and the liquid in the extension chamber R1 moves to the compression chamber R2 through the extension damping passage 15. Also, when the variable damping force damper 2 extends, the rod 12 retracts from inside the cylinder 11, so the check valve 22 opens, and liquid equivalent to the volume of the rod 12 retracting from inside the cylinder 11 is supplied from inside the reservoir R to inside the cylinder 11 via the suction passage 21. Therefore, when the variable damping force damper 2 extends, the damping force adjustment valve DV resists the flow of liquid from the extension chamber R1 to the compression chamber R2, increasing the pressure in the extension chamber R1 and generating a damping force that hinders the upward movement of the piston 11. Furthermore, the variable damping force damper 2 supplies fluid from the reservoir R into the cylinder 11 to compensate for the volume of the rod 12 retracting from the cylinder 11. The damping force adjustment valve DV can adjust its opening pressure in two stages (high and low) depending on whether or not the solenoid Sol is energized. Therefore, when the variable damping force damper 2 is in extension operation and the solenoid Sol is not energized, it generates a normal damping force. When the solenoid Sol is energized, it can generate a harder damping force, which is higher than the normal damping force.

On the other hand, when the variable damping force damper 2 is in the contraction operation, where the piston 13 moves downward relative to the cylinder 11 as shown in Figure 2, the liquid in the compression chamber R2, which is compressed by the piston 13, moves through the compression passage 16 to the expansion chamber R1, which is expanded by opening the check valve 17. Also, when the variable damping force damper 2 is in the contraction operation, the rod 12 enters the cylinder 11, causing the base valve 20 to open and the liquid equivalent to the volume of the rod 12 entering the cylinder 11 to be discharged to the reservoir R via the compression damping passage 19. Therefore, during the contraction operation, the variable damping force damper 2 resists the flow of liquid from the compression chamber R2 to the reservoir R via the base valve 20, increasing the pressure inside the cylinder 11 and generating a damping force that hinders the downward movement of the piston 11. Furthermore, the variable damping force damper 2 compensates for the volume of liquid that enters the cylinder 11 when the rod 12 enters the cylinder 11 by discharging liquid from the cylinder 11 to the reservoir R.

As described above, the variable damping force damper 2 generates both a normal damping force and a harder damping force (higher than normal) during extension operation by switching the power supply to the solenoid Sol on and off. During compression operation, it generates damping force, but the damping force cannot be adjusted. In other words, the variable damping force damper 2 is configured as a damper that allows adjustment only of the damping force on the extension side.

In this embodiment, the variable damping force damper 2, as shown in Figure 2, is a so-called twin-cylinder type damper with an outer cylinder 14 forming a reservoir R on the outer circumference of the cylinder 11. However, it may also be a so-called single-cylinder type damper, where the valve case 18, compression damping passage 19, base valve 20, suction passage 21, suction check valve 22, outer cylinder 14, and reservoir R are eliminated, and an air chamber is partitioned below the compression chamber R2 within the cylinder 11 by a free piston, and a compression damping valve that provides resistance to the liquid flow is provided in the compression passage 16 instead of the check valve 17.

Even if the variable damping force damper 2 is a single-tube type damper, the damping force can be adjusted to two levels, high and low, when it extends using the damping force adjustment valve DV. If the variable damping force damper 2 is to only allow adjustment of the damping force on the compression side, the base valve 20 in the configuration shown in Figure 2 can be eliminated and replaced with a damping force adjustment valve DV in the compression side damping passage 19. Alternatively, the damping force adjustment valve DV can be eliminated and a valve that resists the flow of liquid from the extension side chamber R1 to the compression side chamber R2 can be installed in the extension side damping passage 15. With this configuration of the variable damping force damper 2, only the damping force on the compression side can be adjusted to high or low by switching the power supply to the solenoid Sol of the damping force adjustment valve DV on or off. Furthermore, if the variable damping force damper 2 is a single-tube type damper and only the compression damping force is to be adjusted, a damping force adjustment valve DV can be provided in place of the check valve 17 in the compression passage 15. Alternatively, the damping force adjustment valve DV can be eliminated, and a valve that resists the flow of liquid from the extension chamber R1 to the compression chamber R2 can be provided in the extension damping passage 15. With this configuration, the variable damping force damper 2 can be adjusted only on the compression side by switching the power supply to the solenoid Sol of the damping force adjustment valve DV on and off. In this embodiment of the suspension device 1, the variable damping force damper 2 is interposed between the rear wheels Wrl and Wrr of the vehicle V and the vehicle body B. Therefore, the characteristics of the normal extension damping force and the compression damping force of the variable damping force damper 2 are set to be suitable for suppressing vibrations of the vehicle body B directly above each of the front wheels Wrl and Wrr of the vehicle V.

The passive damper 3 is a damper whose damping force cannot be adjusted, and which generates a damping force that prevents expansion and contraction when subjected to external forces. For components of the passive damper 3 that are the same as those of the variable damping damper 2, the same reference numerals are used, and detailed explanations are omitted to avoid duplication of explanation.

The passive damper 3, as shown in Figure 3, for example, includes a cylinder 11, a rod 12 inserted into the cylinder 11 so as to be movable in the axial direction, a piston 13 inserted into the cylinder 11 so as to be movable in the axial direction and connected to the rod 12, which divides the inside of the cylinder 11 into an extension chamber R1 and a compression chamber R2 filled with liquid, an outer cylinder 14 that covers the outer circumference of the cylinder 11 and forms a reservoir R between itself and the cylinder 11, an extension damping passage 15 that connects the extension chamber R1 and the compression chamber R2, and an extension damping passage The passive damper 3 includes an extension damping valve 25 provided in the damping passage 15, a compression passage 16 connecting the compression chamber R2 and the extension chamber R1, a check valve 17 for opening and closing the compression passage 16, a valve case 18 provided at the end of the cylinder 11 that separates the compression chamber R2 and the reservoir R, a compression damping passage 19 connecting the compression chamber R2 and the reservoir R, a base valve 20 provided in the compression damping passage 19, an intake passage 21 connecting the reservoir R and the compression chamber R2, and an intake check valve 22 provided in the intake passage 21. The passive damper 3 differs from the variable damping damper 2 in that, while the variable damping damper 2 had a damping force adjustment valve DV in the extension damping passage 15, the passive damper 3 has an extension damping valve 25 instead of the damping force adjustment valve DV in the extension damping passage 15. The extension damping valve 25 is designed to resist the flow of liquid from the extension chamber R1 to the compression chamber R2 via the extension damping passage 15. When the pressure in the extension chamber R1 exceeds the pressure in the compression chamber R2 and the difference between them reaches the opening pressure, the valve opens, allowing the aforementioned liquid flow while resisting it. The extension damping valve 25 also closes to block the flow of liquid attempting to move from the compression chamber R2 to the extension chamber R1 via the extension damping passage 15. The extension damping valve 25 may be replaced by an orifice or choke instead of a valve that opens and closes the extension damping passage 15.

The passive damper 3 is installed at two locations between the vehicle body B and the front wheels Wfl and Wfr, by connecting the rod 12 to the vehicle body B and the outer cylinder 14 to the front wheels Wfl and Wfr.

In the passive damper 3 configured in this way, when the piston 13 moves upward relative to the cylinder 11 in the extension operation shown in Figure 2, the pressure in the extension chamber R1, which is compressed by the piston 13, rises and exceeds the pressure in the compression chamber R2, which is expanded. When the pressure difference between the two reaches the valve opening pressure, the extension damping valve 25 opens, and the liquid in the extension chamber R1 moves to the compression chamber R2 through the extension damping passage 15. Also, when the variable damping force damper 2 extends, the rod 12 retracts from inside the cylinder 11, so the check valve 22 opens, and liquid equivalent to the volume of the rod 12 retracting from inside the cylinder 11 is supplied from inside the reservoir R to inside the cylinder 11 via the suction passage 21. Therefore, when the passive damper 3 extends, the extension damping valve 25 resists the flow of liquid from the extension chamber R1 to the compression chamber R2, increasing the pressure in the extension chamber R1 and generating a damping force that hinders the upward movement of the piston 11. Furthermore, the passive damper 3 supplies liquid from the reservoir R into the cylinder 11 to compensate for the volume by which the rod 12 exits the cylinder 11.

On the other hand, when the passive damper 3 is in the contraction operation where the piston 13 moves downward relative to the cylinder 11 (Figure 2), the liquid in the compression chamber R2, which is compressed by the piston 13, moves through the compression passage 16 to the expansion chamber R1, which is expanded by opening the check valve 17. Also, when the variable damping force damper 2 is in the contraction operation, the rod 12 enters the cylinder 11, causing the base valve 20 to open and the liquid equivalent to the volume of the rod 12 entering the cylinder 11 to be discharged to the reservoir R via the compression damping passage 19. Therefore, when the variable damping force damper 2 is in the contraction operation, the base valve 20 resists the flow of liquid from the compression chamber R2 to the reservoir R, increasing the pressure inside the cylinder 11 and generating a damping force that hinders the downward movement of the piston 11. Furthermore, the variable damping force damper 2 compensates for the volume of liquid that enters the cylinder 11 when the rod 12 enters the cylinder 11 by discharging liquid from the cylinder 11 to the reservoir R.

As described above, the passive damper 3 generates damping force by the extension-side damping valve 25 during extension operation and by the base valve 20 during contraction operation, but the damping force generated during extension and contraction cannot be adjusted. In other words, the passive damper 3 is configured as a damper whose damping force cannot be adjusted. In this embodiment of the suspension system 1, the passive damper 3 is interposed between the front wheels Wfl and Wfr of the vehicle V and the vehicle body B. Therefore, the extension and contraction damping force characteristics of the passive damper 3 are set to be suitable for suppressing vibrations of the vehicle body B directly above each of the front wheels Wfl and Wfr of the vehicle V.

In this embodiment, the passive damper 3, as shown in Figure 3, is a so-called twin-cylinder type damper with an outer cylinder 14 forming a reservoir R on the outer circumference of the cylinder 11. However, it may also be a so-called single-cylinder type damper, where the valve case 18, compression damping passage 19, base valve 20, suction passage 21, suction check valve 22, outer cylinder 14, and reservoir R are eliminated, and an air chamber is partitioned below the compression chamber R2 within the cylinder 11 by a free piston, and a compression damping valve that provides resistance to the liquid flow is provided in the compression passage 16 instead of the check valve 17.

As described above, the variable damping force damper 2 allows adjustment of the extension damping force only between a normal damping force and a harder damping force (higher than normal). It is installed in pairs, one per wheel, between the vehicle body B and the rear left and right wheels Wrl and Wrr of the two front and rear wheel rows of the vehicle V. The other passive damper 3 does not allow adjustment of the damping force on either the extension or extension side. It is installed in pairs, one per wheel, between the vehicle body B and the front left and right wheels Wfl and Wfr of the two front and rear wheel rows of the vehicle V.

The variable damping damper 2 and passive damper 3 generate damping force by expanding and contracting when the wheels Wfl, Wfr, Wrl, and Wrr are displaced relative to the vehicle body B due to road surface input during vehicle V's operation, thereby suppressing the relative displacement. When the extension damping force of the variable damping damper 2 is switched from normal to hard, the variable damping damper 2 generates a harder damping force than normal during extension operation. Therefore, the vehicle body B is less likely to lift compared to when the variable damping damper 2 generates normal damping force during extension operation.

When vehicle V is in motion and the occupant of vehicle V presses the brake pedal, causing vehicle V to brake, pitching occurs as the front of vehicle body B sinks and the rear of vehicle body B lifts. However, if the extension damping force of the variable damping damper 2 is switched to hard during braking, the lifting of the rear of vehicle body B is suppressed, thus reducing the pitching of vehicle body B, lowering the center of gravity of vehicle body B, and shortening the braking distance.

Furthermore, when vehicle V turns, the centrifugal force acting on the vehicle body B causes a roll, tilting the vehicle body B towards the opposite side of the turning center around the longitudinal axis. When vehicle body B exhibits a roll tilting to either the left or right, either the left wheel Wrl or the right wheel Wrr of the rear wheel row will inevitably exhibit extension action. Therefore, when the extension damping force of the variable damping damper 2 is switched to hard during vehicle V's turn, the variable damping damper 2 exhibiting extension action generates a high hard damping force. This reduces the amount of roll in vehicle body B compared to when the variable damping damper 2 generates normal damping force during extension action. Therefore, switching the extension damping force of the variable damping damper 2 to hard during vehicle V's turn reduces the roll of vehicle body B, suppresses fluctuations in the contact load of the inner rear wheel during turning, and reduces understeer during vehicle V's turn.

Next, as shown in Figure 4, the controller 4 includes a processing unit 41 that determines whether to set the damping force of the variable damping force damper 2 to normal or hard during extension operation and determines whether or not to energize the solenoid Sol; a drive circuit 42 that supplies current to the solenoid Sol of the variable damping force damper 2 based on a command from the processing unit 41; and an interface circuit 43 for acquiring information from sensors 51 installed on the vehicle V via a CAN bus 53 mounted on the vehicle V.

In this embodiment, the arithmetic processing unit 41 receives information collected by the vehicle V via the interface circuit 43 and transmitted onto the CAN bus 53, and determines whether to set the extension damping force of the variable damping force damper 2 to normal or hard. The arithmetic processing unit 41, for example (not shown in the figure), includes an arithmetic processing unit and a storage unit such as a ROM (Read Only Memory) or RAM (Ramdom Access Memory) that stores the program necessary for the processing of the arithmetic processing unit and provides the necessary storage area. It receives the brake on/off signal and steering angle as information from the vehicle V and determines whether to set the extension damping force of the variable damping force damper 2 to normal or hard.

Specifically, as shown in Figure 5, the arithmetic processing unit 41 receives the brake on/off signal (step S1) and determines whether the on/off signal indicates that the brake is on (step S2). If the on/off signal indicates that the brake is on, the arithmetic processing unit 41 determines that the extension damping force of the variable damping force damper 2 should be set to hard because the vehicle V is braking (step S3). The arithmetic processing unit 41 also receives the steering angle (step S1) and determines whether the steering angle is greater than or equal to a predetermined steering angle threshold (step S4). If the steering angle is greater than or equal to the steering angle threshold, the arithmetic processing unit 41 determines that the extension damping force of the variable damping force damper 2 should be set to hard because the vehicle V is turning (step S3). The calculations in steps S2 and S4 of the processing unit 41 are performed in parallel. When either of the following conditions is met—that the brake on/off signal indicates the brake is on, or that the steering angle is greater than or equal to the steering angle threshold—the processing unit 41 determines that the extension damping force of the variable damping force damper 2 should be set to hard.

Then, when the processing unit 41 determines that the extension damping force of the variable damping force damper 2 should be set to hard, it commands the drive circuit 42 to energize each solenoid Sol (step S5). Upon receiving the command, the drive circuit 42 energizes each solenoid Sol and drives them. Therefore, the variable damping force damper 2 generates damping force in accordance with extension and contraction, with the extension damping force set to hard.

The arithmetic processing unit 41 determines that if the signal does not indicate that the brakes are on and the steering angle is less than the steering angle threshold, the extension damping force of the variable damping force damper 2 should be set to normal (step S6). If the arithmetic processing unit 41 determines that the extension damping force of the variable damping force damper 2 should be set to normal, it does not issue a command to the drive circuit 42, and the drive circuit 42 does not supply power to each solenoid Sol. Therefore, the variable damping force damper 2 generates damping force according to extension and contraction with the extension damping force set to normal. The arithmetic processing unit 41 controls the variable damping force damper 2 by repeatedly performing the above procedure at a predetermined calculation cycle.

In this way, the controller 4 switches the extension damping force of the variable damping damper 2 to hard when the vehicle V is braking or turning, so that the suspension system 1 can suppress pitching and rolling of the vehicle body B. The controller 4 may also acquire the longitudinal acceleration of the vehicle body B as information to determine that the vehicle V is in a braking state, and switch the damping force of the variable damping damper 2 to hard if the forward acceleration of the vehicle body B is greater than or equal to a predetermined acceleration threshold. Furthermore, the controller 4 may acquire the yaw rate of the vehicle body B as information to determine that the vehicle V is in a turning state, and switch the damping force of the variable damping damper 2 to hard if the absolute value of the yaw rate of the vehicle body B is greater than or equal to a predetermined yaw rate threshold, or it may acquire the steering angular velocity and switch the damping force of the variable damping damper 2 to hard if the absolute value of the steering angular velocity is greater than or equal to a threshold. Furthermore, the controller 4 may recognize that an emergency avoidance maneuver is being performed based on the characteristics of signals such as brake, steering angle, and steering angular velocity output when the driver of vehicle V performs an emergency avoidance maneuver, and may switch the damping force of the variable damping damper 2 to hard mode.

Furthermore, when a variable damping force damper 2 is interposed between the vehicle body B and the front wheels Wfl and Wfr, and a passive damper 3 is interposed between the vehicle body B and the rear wheels Wrl and Wrr, when the vehicle body B rolls, either the left wheel Wfl or the right wheel Wfr of the front row of left and right wheels will always exhibit extension action. Therefore, when the extension damping force of the variable damping force damper 2 is switched to hard when the vehicle V is turning, the variable damping force damper 2 that exhibits extension action among the pairs of variable damping force dampers 2 arranged in the left and right wheel rows will generate a high hard damping force. As a result, the amount of roll of the vehicle body B will be smaller compared to when the variable damping force damper 2 generates a normal damping force during extension action. Therefore, when the extension damping force of the variable damping force damper 2 is switched to hard when the vehicle V is turning, the roll of the vehicle body B can be reduced. Furthermore, in this case, switching the extension damping force of the variable damping damper 2 to hard suppresses the lifting of the front of the vehicle body B and the sinking of the rear, thereby suppressing squat during vehicle V acceleration. To suppress squat, the controller 4 can obtain information from vehicle V indicating that vehicle V is accelerating and switch the damping force of the variable damping damper 2 to hard. Since the controller 4 only needs to obtain information from vehicle V indicating that vehicle V is accelerating, for example, it can obtain the throttle opening and the longitudinal acceleration of vehicle body B via the CAN bus 53. The controller 4 may switch the damping force of the variable damping damper 2 to hard when the throttle opening exceeds a predetermined throttle opening threshold, or when the rearward acceleration of vehicle body B exceeds a predetermined acceleration threshold.

When a variable damping force damper 2 is interposed between the vehicle body B and the front wheels Wfl and Wfr, and a passive damper 3 is interposed between the vehicle body B and the rear wheels Wrl and Wrr, and it is desired to suppress pitching of the vehicle body B during braking, the damping force of the variable damping force damper 2 on the compression side can be adjusted to two levels: normal and hard. Note that when the vehicle body B rolls, either the left wheel Wfl or the right wheel Wfr in the same left and right wheel row will always exhibit compression action. Therefore, if the variable damping force damper 2 can be switched to hard on the compression side, switching the damping force of the variable damping force damper 2 to hard will reduce the amount of roll of the vehicle body B compared to when the variable damping force damper 2 generates normal damping force on the compression side.

Furthermore, if the variable damping force damper 2 can be switched to a hard setting for compression, then by interposing the variable damping force damper 2 between the vehicle body B and the rear wheels Wrl and Wrr, respectively, and interposing the passive damper 3 between the vehicle body B and the front wheels Wfl and Wfr, respectively, when the compression damping force of the variable damping force damper 2 is switched to a hard setting, it is possible to suppress not only the roll of the vehicle body B during cornering but also the squat of the vehicle body B during acceleration.

Thus, the variable damping force damper 2 may not only allow switching of the damping force on the extension side to two stages (normal and hard), but it may also allow switching of the damping force on the compression side to two stages (normal and hard). Then, depending on whether it is desired to suppress pitching or squat of the vehicle body B, the variable damping force damper 2 can be installed on either the front left and right wheel rows or the rear left and right wheel rows of the vehicle body B.

In the case of dampers used in the suspension of vehicle V, the damping force on the extension side is generally set higher than the damping force on the compression side, generating a higher damping force when the vehicle body B separates from the wheels. By setting the damping force characteristics of the extension and compression sides of the damper in this way, the center of gravity tends to lower as the vehicle body B vibrates repeatedly, stabilizing the vehicle's posture during driving. Furthermore, since the compression damping force does not become too hard, it prevents the ride comfort of vehicle V from deteriorating due to jarring inputs. Therefore, if only the extension damping force of the variable damping force damper 2 can be switched between normal and hard, the hard damping force can be increased compared to the case where only the compression damping force of the variable damping force damper 2 can be switched between normal and hard. This enhances the suppression effect of vehicle body B's roll and pitching or squat, thereby suppressing the deterioration of ride comfort.

Furthermore, the variable damping force dampers 2 may be interposed in all left and right wheel rows of the vehicle V. Therefore, in this embodiment, since the vehicle V is a four-wheeled automobile, the variable damping force dampers 2 may be interposed between the vehicle body B and all the wheels Wfl, Wfr, Wrl, and Wrr of the front and rear left and right wheel rows. In this case, even if the variable damping force dampers 2 can be switched between two stages for extension damping force, or two stages for compression damping force, setting the damping force of all variable damping force dampers 2 to hard will suppress the roll, pitching, and squat of the vehicle body B.

Furthermore, if the suspension system 1 wishes to suppress only the roll, pitching, or squat of the vehicle body B during cornering, the damping force of the variable damping damper 2 may be switched to a harder setting only when the vehicle V is cornering, braking, or accelerating.

As described above, the suspension system 1 of this embodiment comprises a vehicle V having a vehicle body B and multiple rows of wheels Wfl, Wfr, Wrl, Wrr arranged in the longitudinal direction relative to the vehicle body B, each including one or more left and right wheel rows with wheels on each side of the vehicle body B; a variable damping force damper 2 interposed between the vehicle body B and at least one or more left and right wheel rows Wrl, Wrr (Wfl, Wfr), and capable of adjusting only the damping force on the extension or compression side; and a controller 4 that controls the damping force of the variable damping force damper 2 based on information collected by and obtained from the vehicle V.

In the suspension system 1 configured in this way, the variable damping force damper 2 can only be adjusted for extension or compression damping. Therefore, the variable damping force damper 2 is simplified and inexpensive. Furthermore, the controller 4 adjusts the damping force of the variable damping force damper 2 using information originally collected by the vehicle V, eliminating the need for the suspension system 1 to possess its own sensors. Thus, according to the suspension system 1 of this embodiment, since no separate sensors are required and only the structurally simple variable damping force damper 2 is used for damping force adjustment, the entire system can be made inexpensive while controlling the vehicle body B's posture and suppressing roll, pitching, or squat of the vehicle body B by adjusting the damping force of the variable damping force damper 2.

Furthermore, in the suspension system 1 of this embodiment, the controller 4 controls the damping force of the variable damping damper 2 based on information collected by and obtained from the vehicle V. Therefore, when the suspension system 1 is installed on a vehicle V that performs collision avoidance control and driver assistance control in addition to the occupant's operation, the suspension system 1 can quickly detect the braking and turning of the vehicle V from the vehicle V's information and quickly implement attitude control of the vehicle body B in situations where braking and turning are performed by collision avoidance control or driver assistance control prior to the occupant's driving operation of the vehicle V.

In this embodiment of the suspension device 1, the variable damping force damper 2 is configured to allow adjustment of the damping force on the extension or compression side in two stages: normal and harder than normal. However, the damping force on the extension or compression side may be adjustable in multiple stages or steplessly. However, if the variable damping force damper 2 allows adjustment of the damping force in two stages: normal damping force and harder damping force, the configuration of the damping force adjustment valve DV of the variable damping force damper 2 becomes simpler, making the suspension device 1 even cheaper. Furthermore, the controller 4 may supply current from the drive circuit 42 to the solenoid Sol at an on-duty ratio corresponding to the vehicle speed obtained via the CAN bus 53 when the vehicle V is being braked. Alternatively, the controller 4 may supply current from the drive circuit 42 to the solenoid Sol at an on-duty ratio corresponding to the brake pressure via the CAN bus 53 when the vehicle V is being braked. Furthermore, when the vehicle V is turning, the controller 4 may supply current from the drive circuit 42 to the solenoid Sol at an on-duty ratio corresponding to the steering angular velocity obtained by differentiating the steering angle. In this way, even when using a variable damping damper 2 that can switch between normal and hard damping forces, the damping force can be arbitrarily adjusted between normal and hard by changing the on-duty ratio.

Furthermore, in the suspension system 1 of this embodiment, the variable damping force damper 2 can only adjust the damping force on the extension side and is interposed between the vehicle body B and the wheels Wrl, Wrr of the left and right wheel rows on the rear side of the vehicle body B. With the suspension system 1 configured in this way, the extension side damping force of the variable damping force damper 2 can be made harder, thereby suppressing roll during cornering and pitching during braking, while lowering the center of gravity of the vehicle body B to stabilize the vehicle's posture during driving, and suppressing deterioration of ride comfort during compression.

Furthermore, the variable damping force damper 2 in the suspension device 1 of this embodiment includes a cylinder 11, a rod 12 inserted into the cylinder 11 so as to be movable in the axial direction, a piston 13 inserted into the cylinder 11 so as to be movable in the axial direction and connected to the rod 12, which divides the inside of the cylinder 11 into an extension chamber R1 and a compression chamber R2 filled with liquid, and a damping force adjustment valve DV having a solenoid Sol, which can adjust the resistance applied to the flow of liquid passing through in two stages by turning the solenoid Sol on and off. With the suspension device 1 configured in this way, the damping force of the variable damping force damper 2 can be easily switched between normal and hard by turning the solenoid Sol on and off, making power supply control easy and the configuration of the variable damping force damper 2 very simple. Also, since the damping force of the variable damping force damper 2 can be switched between normal and hard by turning the solenoid Sol on and off, the drive circuit configuration in the controller 4 can be made very simple. Furthermore, the controller 4 only needs to set the damping force of the variable damper 2 to either normal or hard, eliminating the need for complex calculations. Therefore, an inexpensive microcomputer can be used for the processing unit 41. This configuration makes the suspension system 1 even more cost-effective.

Furthermore, if only one of the variable damping force dampers 2 on the left or right wheel malfunctions, since the variable damping force dampers 2 are installed in pairs between the vehicle body B and at least one left and right wheel in the left and right wheel rows, if only the damping force of the non-malfunctioning variable damping force damper 2 switches to a harder setting, the vehicle body B may become unstable, prone to rolling and pitching or squating on only one side. However, in the suspension device 1 of this embodiment, each solenoid Sol in the variable damping force damper 2 is connected in series, and the controller 4 has only one drive circuit 42 that energizes the solenoid Sol. With the suspension system 1 configured in this way, regardless of the number of variable damping force dampers 2 installed in the vehicle V, the damping force of the variable damping force dampers 2 can be switched with a single drive circuit 42. Furthermore, if there is a failure in one of the solenoids Sol or the wiring 24 supplying power to the solenoid Sol among the multiple variable damping force dampers 2, the damping force adjustment of all variable damping force dampers 2 is forcibly disabled. This automatically avoids a situation where the vehicle body B becomes prone to rolling, pitching, or squating on only one side. While it is also possible to connect the solenoids Sol of each variable damping force damper 2 in parallel to the drive circuit 42, the suspension system 1, in which the solenoids Sol are connected in series and the controller 4 has only one drive circuit 42 supplying power to the solenoids Sol, is advantageous because, as mentioned above, it automatically performs a fail-safe in the event of a failure in one variable damping force damper 2.

Furthermore, the suspension system 1 of this embodiment includes passive dampers 3, which have no damping force adjustment, interposed between the vehicle body B and all wheels except for the left and right wheel rows where the variable damping force dampers 2 are installed. With this configuration, the suspension system 1 can be made even more inexpensive because the variable damping force dampers 2 are installed only on the left and right wheel rows necessary for controlling the vehicle body B's posture, while the remaining left and right wheel rows are fitted with passive dampers 3, which are less expensive than the variable damping force dampers 2.

Furthermore, in the suspension system 1 of this embodiment, the controller 4 controls the damping force of the variable damping damper 2 based on information that allows the system to grasp at least one of braking, acceleration, and cornering from the vehicle V. With the suspension system 1 configured in this way, pitching, rolling, or squat of the vehicle body B can be suppressed.

Although preferred embodiments of the present invention have been described in detail above, modifications, alterations, and changes are permitted as long as they do not deviate from the scope of the claims.

1...Suspension system, 2...Variable damping force damper, 3...Passive damper, 4...Controller, 11...Cylinder, 12...Rod, 13...Piston, 42...Drive circuit, B...Vehicle body, DV...Damping force adjustment valve, R1...Rebound chamber, R2...Compression chamber, Sol...Solenoid, V...Vehicle, Wfl, Wfr, Wrl, Wrr...Wheels

Claims (5)

A vehicle having a body and wheels arranged in multiple rows in the longitudinal direction relative to the body, including one or more left and right wheel rows, each having wheels on the left and right sides of the body, is provided with a damping force variable damper interposed between the body and the wheels of at least one of the left and right wheel rows, which is capable of adjusting only the damping force on the extension side or the compression side,
The system includes a controller that obtains information collected by the vehicle from the vehicle and controls the damping force of the variable damping damper based on the information,
The aforementioned variable damping force damper is
Cylinder and
A rod is inserted into the cylinder so as to be movable in the axial direction,
A piston is inserted into the cylinder so as to be movable in the axial direction and connected to the rod, dividing the inside of the cylinder into an extension chamber and a compression chamber, both of which are filled with liquid.
It has a solenoid and a damping force adjustment valve that can adjust in two stages the resistance applied to the flow of liquid passing through by turning the solenoid on and off,
Each of the solenoids in the variable damping damper is connected in series.
The suspension device is characterized in that the controller has only one drive circuit that supplies power to the solenoid. The suspension device according to claim 1 , characterized in that the damping force variable damper is capable of adjusting only the damping force on the extension side and is interposed between the vehicle body and the wheels of the left and right rear wheel rows of the vehicle body. The suspension device according to claim 1 , characterized in that the variable damping force damper can be adjusted in two stages: normal damping force and hard damping force which is higher than normal. The suspension device according to claim 1 or 2 , further comprising passive dampers, which cannot be adjusted for damping force, interposed between the vehicle body and all wheels other than the left and right wheel rows on which the variable damping force dampers are interposed. The suspension device according to any one of claims 1 to 4 , characterized in that the controller controls the damping force of the variable damping damper based on information that allows the controller to determine at least one of braking, acceleration, and turning from the vehicle.