buffer

Abstract

To provide a shock absorber which can inhibit occurrence of noise without causing increase in the weight of a vehicle and grasp vibration of an unsprung member without difficult installation work.SOLUTION: A shock absorber 1 includes: a shock absorber body 2 having a cylinder 6 which is connected to a wheel (an unsprung member) W of a vehicle V, and a rod 8 which gets into / out from the cylinder 6 to move relative to the cylinder 6 and is connected to a vehicle body (a sprung member) B of the vehicle V; a solenoid valve (a damping force adjuster) 3 which can adjust a damping force generated during expansion / contraction of the shock absorber body 2 according to an amount of a supplied electric current; and an electric current control unit 5 which is attached to the cylinder 6 and supplies an electric current to the solenoid valve (the damping force adjuster) 3 based on a control command received from an ECU (a control device) 4 mounted on the vehicle V. The electric current control unit 5 includes an unsprung acceleration sensor 5c.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an improvement of a shock absorber.

Background Art

[0002] Conventionally, a shock absorber with adjustable damping force includes a shock absorber body that is interposed between the upper spring member and the lower spring member of a vehicle and expands and contracts, and a damping valve that provides resistance to the flow of fluid filled in the shock absorber body and is driven by a solenoid to adjust the generated damping force. The control of the solenoid is performed by a dedicated ECU (Electronic Control Unit) specialized for controlling the shock absorber mounted on the vehicle.

[0003] The dedicated ECU includes various sensors for obtaining various information for recognizing the running state of the vehicle, such as the vehicle speed, the acceleration above the spring, and the acceleration below the spring, in order to make the damping force of the shock absorber optimal according to the running state of the vehicle, and an arithmetic unit for obtaining the damping force that the shock absorber should generate based on the information from the sensors. The dedicated ECU supplies current to the solenoid of the damping valve so that the shock absorber generates the required damping force.

[0004] In such a system, it is necessary to adjust the damping force of the shock absorbers arranged at various positions of the four wheels of the vehicle. However, if an arithmetic unit is provided for each shock absorber, the cost of the entire system will be high. Therefore, the damping force of each shock absorber is obtained by one arithmetic unit, and the solenoid driver required for driving the solenoid is also held on the dedicated ECU side.

[0005] The solenoid driver includes a drive circuit for driving the solenoid and a current control circuit by current feedback. When receiving a current command indicating the amount of current to be supplied to the solenoid in order to generate the damping force required by the arithmetic unit in the shock absorber, the solenoid driver supplies current to the solenoid according to the current command (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 05-169949 (Figure 1) [Patent Document 2] Japanese Patent Publication No. 2008-62851 (Figure 1) [Overview of the project] [Problems that the invention aims to solve]

[0007] In the aforementioned system, four sets of long harnesses are required to connect the dedicated ECU to the four solenoids of the shock absorbers located at each of the four wheels, thereby increasing the weight of the vehicle.

[0008] Furthermore, the switching current generated by repeatedly switching the solenoids flowing through the harness on and off due to PWM driving could generate noise that could affect other equipment in the vehicle.

[0009] Furthermore, when considering vibrations of the vehicle's unsprung mass when controlling the shock absorber, or when it is necessary to understand the road surface conditions, it is necessary to install unsprung acceleration sensors on the suspension members at each of the four wheels of the vehicle, and to connect these unsprung acceleration sensors to a dedicated ECU with signal wires. Therefore, the installation work of the unsprung acceleration sensors and the wiring work of the signal wires are troublesome.

[0010] Therefore, the present invention aims to provide a shock absorber that does not increase the weight of the vehicle, can suppress the generation of noise, and can detect vibrations of the unsprung mass without requiring troublesome installation work. [Means for solving the problem]

[0011] To achieve the above objectives, the shock absorber of the present invention comprises a shock absorber body having a cylinder connected to the unsprung member of a vehicle and a rod that moves in and out of the cylinder and is movable relative to the cylinder and connected to the sprung member of a vehicle; a damping force adjustment device that can adjust the damping force generated when the shock absorber body expands and contracts according to the amount of current supplied; and a current control unit attached to the cylinder that supplies current to the damping force adjustment device based on a control command received from a control device mounted on the vehicle, the current control unit being equipped with an unsprung acceleration sensor.

[0012] In this type of shock absorber configuration, the current control unit, which receives control commands from the on-board control device, controls the damping force adjustment device. Therefore, the current control unit and the control device only need to be connected via signal lines, eliminating the need to connect the control device and the current control unit with a harness to supply switching current to the damping force adjustment device. Furthermore, since the current control unit is equipped with an unsprung mass acceleration sensor, the installation of the unsprung mass acceleration sensor is completed simply by installing the shock absorber in the vehicle. This eliminates the need to directly connect the unsprung mass acceleration sensor and the control device, and allows for the detection of vibrations in the unsprung mass components, thus simplifying the installation of the unsprung mass acceleration sensor.

[0013] Furthermore, the current control unit in the buffer may be equipped with a CAN (Controller Area Network) interface. With a buffer configured in this way, control commands can be received from the control device via the CAN bus, and since the signal lines can be shortened by using the CAN bus, the weight in the vehicle can be further reduced.

[0014] Furthermore, when the current control unit receives control commands via the CAN bus, it is ideal when the control device is an integrated ECU used for controlling the vehicle's engine and other systems. In addition, when the current control unit transmits the acceleration detected by the unsprung acceleration sensor to the CAN bus via the CAN interface, the acceleration information can be used by control devices and other equipment installed in the vehicle, and this acceleration information can be used for controlling the shock absorber and understanding the road surface conditions.

[0015] Furthermore, the current control unit in the shock absorber may correct the damping force instructed by the control command based on the acceleration detected by the unsprung acceleration sensor to determine the target damping force, and then supply current to the damping force adjustment device based on the target damping force. In a shock absorber configured in this way, the vibrations input from the road surface on which the vehicle is traveling can be detected as quickly as possible using the unsprung acceleration sensor, so the damping force of the shock absorber can be optimally corrected according to the input from the road surface, thereby improving the ride comfort and wheel contact of the vehicle.

[0016] Furthermore, the current control unit in the shock absorber may detect abnormalities based on the acceleration detected by the unsprung acceleration sensor. With a shock absorber configured in this way, abnormalities can be detected using the acceleration detected by the unsprung acceleration sensor, making it possible to detect abnormalities due to deterioration of the shock absorber body or mechanical abnormalities of the shock absorber body.

[0017] Furthermore, the current control unit in the buffer may be equipped with a wireless communication device. With a buffer configured in this way, communication with the control device is done wirelessly only, and the signal lines connecting the current control unit and the control device can be completely eliminated, thus further reducing the weight of the vehicle.

[0018] Also, when the current control unit includes a communication device, it may be communicable with a pneumatic pressure sensor that detects the pneumatic pressure in the vehicle wheels via the communication device, and transfer the information on the pneumatic pressure detected by the pneumatic pressure sensor received via the communication device to the control device. In the shock absorber configured as described above, even if the electric field strength of the radio wave output by the pneumatic pressure sensor is reduced, since the current control unit is disposed near the pneumatic pressure sensor, the current control unit can receive the information on the pneumatic pressure detected by the pneumatic pressure sensor and transfer it to the control device. Therefore, according to the shock absorber configured as described above, it is possible to reduce the power consumption of the pneumatic pressure sensor and extend the time during which the pneumatic pressure sensor can continuously transmit the pneumatic pressure.

Effects of the Invention

[0019] As described above, according to the shock absorber of the present invention, it is possible to suppress the generation of noise without causing an increase in the weight of the vehicle, and to grasp the vibration of the spring lower member without troublesome installation work.

Brief Description of the Drawings

[0020] [Figure 1] It is a diagram showing a vehicle equipped with a shock absorber in one embodiment. [Figure 2] It is a schematic cross-sectional view of a shock absorber body of a shock absorber in one embodiment. [Figure 3] It is a configuration diagram of a current control unit of a shock absorber in one embodiment. [Figure 4] It is a configuration diagram of a control unit of a shock absorber of a modification of one embodiment. [Figure 5] It is a diagram showing a vehicle equipped with a shock absorber of a modification of one embodiment.

Modes for Carrying Out the Invention

[0021] Hereinafter, the present invention will be described based on the embodiments shown in the drawings. FIG. 1 ,2As shown, in one embodiment, the shock absorber 1 comprises a shock absorber body 2 interposed between the vehicle body B, which is the sprung mass member of the vehicle V, and the wheel W, which is the unsprung mass member, and which expands and contracts; a solenoid valve 3, which is a damping force adjustment device that can adjust the damping force generated by the shock absorber body 2; and a current control unit 5 that supplies current to the solenoid valve 3 based on control commands received from an ECU 4, which is a control device mounted on the vehicle.

[0022] The shock absorbers 1 are interposed between the vehicle body B, which is the sprung mass, and the wheels W, which are the unsprung mass, at each of the four wheels of the vehicle V. The current control units 5 in these four shock absorbers 1 each receive control commands from a single ECU 4 and control the solenoid valves 3.

[0023] As shown in Figure 2, the shock absorber body 2 comprises a cylindrical cylinder 6, a piston 7 slidably inserted into the cylinder 6, a rod 8 inserted into the cylinder 6 so as to be movable in the axial direction and connected to the piston 7, an extension chamber R1 and a compression chamber R2 within the cylinder 6, separated by the piston 7 and filled with a liquid such as hydraulic fluid, an intermediate cylinder 9 covering the outer circumference of the cylinder 6 and forming an annular gap between it and the cylinder 6, and a component covering the outer circumference of the intermediate cylinder 9 and filled between it and the intermediate cylinder 9 with gas and liquid. The device is configured with an outer cylinder 10 that forms an annular reservoir R, a flow straightening passage 11 that connects the extension chamber R1 and the compression chamber R2 and allows liquid flow from the compression chamber R2 to the extension chamber R1 with almost no resistance, a suction passage 12 that connects the compression chamber R2 and the reservoir R and allows liquid flow from the reservoir R to the compression chamber R2 with almost no resistance, and a damping passage 13 that connects the extension chamber R1 and the reservoir R through the gap between the cylinder 6 and the intermediate cylinder 9.

[0024] The solenoid valve 3, acting as a damping force control device, is installed in the middle of the damping passage 13. The solenoid valve 3 is configured, for example, with a valve body 3a installed in the middle of the damping passage 13, a spring 3b that biases the valve body 3a to block the damping passage 13, and a solenoid 3c that generates a thrust force that opposes the spring 3b when energized. The solenoid valve 3 can change its opening pressure according to the amount of current flowing through the solenoid 3c.

[0025] Then, when the pressure in the extension chamber R1 upstream of the damping passage 13 acting on the valve body 3a exceeds the relief pressure (opening pressure) of the solenoid valve 3, the force of this pressure and the solenoid 3c pushing on the valve body 3a overcomes the force of the spring 3b that biases the valve body 3a, causing the valve body 3a to compress the spring 3b and the solenoid valve 3 to open the damping passage 13.

[0026] Furthermore, in the case of the solenoid valve 3, increasing the amount of current supplied to the solenoid 3c increases the thrust generated by the solenoid 3c. Therefore, when the amount of current supplied to the solenoid 3c is maximized, the opening pressure of the solenoid valve 3 is minimized, and conversely, when no current is supplied to the solenoid 3c, the opening pressure of the solenoid valve 3 is maximized. Note that the solenoid valve 3 may also be configured such that the opening pressure is maximized when the amount of current supplied to the solenoid 3c is maximized.

[0027] As mentioned above, the solenoid valve 3 allows for adjustment of the valve opening pressure, but it may also allow for adjustment of the flow path area by applying the thrust generated by the solenoid 3c to the valve body 3a. Thus, the damping force adjustment device only needs to be a device that can change the resistance applied to the flow of liquid passing through the damping passage 13 according to the amount of current supplied. In addition to the solenoid valve 3, if the liquid filled in the buffer body 2 is an electroviscous fluid, magnetoviscous fluid, or electromagnetic viscous fluid, it may also be a device that can adjust the resistance applied to the flow of liquid passing through the damping passage 13 by applying an electric field or magnetic field to the liquid passing through the damping passage 13. Furthermore, the damping force adjustment device may allow for adjustment of the damping force when the buffer body 2 is extended and when it is contracted, or it may allow for adjustment of the damping force when either the extended or contracted state is used.

[0028] In the shock absorber body 2 configured in this way, when the shock absorber body 2 extends as the rod 8 moves upward relative to the cylinder 6 in Figure 2, liquid moves from the extension chamber R1, which is compressed by the piston 7 rising inside the cylinder 6, to the reservoir R via the damping passage 13 and the solenoid valve 3. Therefore, the pressure in the extension chamber R1 rises to equal the opening pressure of the solenoid valve 3. Also, when the shock absorber body 2 extends, liquid is supplied from the reservoir R to the compression chamber R2, whose volume is expanded by the piston 7 rising inside the cylinder 6, via the suction passage 12, so the pressure in the compression chamber R2 becomes approximately equal to the pressure in the reservoir R. Therefore, the pressure in the extension chamber R1 becomes higher than the pressure in the compression chamber R2 by the opening pressure of the solenoid valve 3, and the shock absorber body 2 generates a damping force that hinders the extension operation. Furthermore, since the opening pressure of the solenoid valve 3 changes depending on the amount of current supplied to the solenoid 3c, the damping force during the extension operation of the shock absorber body 2 can be adjusted to a higher or lower level according to the amount of current supplied to the solenoid 3c.

[0029] On the other hand, when the shock absorber body 2 contracts as the rod 8 moves downward in Figure 2 relative to the cylinder 6, liquid moves from the compression chamber R2, which is compressed by the piston 7 descending within the cylinder 6, to the expansion chamber R1, which expands via the rectifying passage 11. When the shock absorber body 2 contracts, the volume of liquid equivalent to the volume of the rod 8 entering the cylinder 6 becomes excess liquid within the cylinder 6, and this excess liquid is discharged from the cylinder 6 to the reservoir R via the damping passage 13 and the solenoid valve 3. Therefore, the pressure in both the expansion chamber R1 and the compression chamber R2 within the cylinder 6 rises to equal the opening pressure of the solenoid valve 3. However, since the pressure-receiving area of ​​the piston 7 facing the compression chamber R2 is larger than the pressure-receiving area of ​​the piston 7 facing the expansion chamber R1 by the cross-sectional integral of the rod 8, the shock absorber body 2 generates a damping force that suppresses contraction. Furthermore, since the opening pressure of the solenoid valve 3 changes depending on the amount of current supplied to the solenoid 3c, the damping force of the shock absorber body 2 during contraction can be adjusted to a higher or lower level according to the amount of current supplied to the solenoid 3c.

[0030] The configuration of the shock absorber body 2 is merely an example and is not limited to the above configuration. Any configuration that can generate a damping force that resists the flow of liquid using a damping force adjustment device, thereby preventing the expansion and contraction of the shock absorber body 2, is acceptable. Therefore, in the shock absorber 1 of this embodiment, the shock absorber body 2 is equipped with a reservoir R and is set to a uniflow type in which the liquid circulates sequentially in one direction through the expansion chamber R1, the compression chamber R2, and the reservoir R. However, the shock absorber body 2 may also be set to a biflow type in which the liquid moves back and forth between the expansion chamber R1 and the compression chamber R2 during expansion and contraction. When the shock absorber body 2 is set to a biflow type, if the damping passage connecting the expansion chamber R1 and the compression chamber R2 allows liquid flow from the expansion chamber R1 to the compression chamber R2 and liquid flow from the compression chamber R2 to the expansion chamber R1, a damping force adjustment device should be provided in the damping passage. Furthermore, if the shock absorber body 2 is set to a biflow type, and the shock absorber body 2 is provided with an extension damping passage that allows only liquid flow from the extension chamber R1 to the compression chamber R2 and a compression damping passage that allows only liquid flow from the compression chamber R2 to the extension chamber R1, then damping force adjustment devices may be provided in both the extension damping passage and the compression damping passage, or damping force adjustment devices may be provided in only one of the extension damping passage or the compression damping passage.

[0031] The shock absorber body 2, equipped with the solenoid valve 3 configured in this way, has a cylinder 6 attached to the knuckle or suspension arm that holds the wheel W, connecting it to the wheel W as an unsprung member, and a rod 8 connected to the vehicle body B as an sprung member, and is interposed between the vehicle body B and the wheel W of the vehicle V. The shock absorber body 2 expands and contracts in response to vibrations input from the road surface while the vehicle V is running, generating a damping force that suppresses vibrations of the vehicle body B.

[0032] Next, the ECU4, acting as a control device, is an integrated ECU mounted on the vehicle V that controls not only the shock absorber 1 but also other components of the vehicle V, such as the engine, power steering, anti-lock braking system, airbags, and air conditioner. The ECU4 is connected to the CAN bus 10 mounted on the vehicle V, and via CAN communication, it can obtain information on the vertical acceleration of the vehicle body B at the installation location from the sprung mass acceleration sensors 21, 22, and 23, which are installed so as not to be aligned in the same line with respect to the vehicle body B.

[0033] Although not shown in the diagram, the CAN bus 10 is spread throughout the vehicle V and is connected not only to the sprung mass acceleration sensors 21, 22, and 23, but also to a vehicle speed sensor that detects vehicle speed, a steering angle sensor, and the brakes and accelerator, etc., so that the ECU 4 can obtain various information about the vehicle V through the CAN bus 10.

[0034] ECU4, although not shown in detail, consists of, for example, an arithmetic processing unit and an arithmetic processing unit. of It includes a memory that provides the program necessary for processing and the storage area necessary for executing the program, and a CAN interface that communicates with each device via the CAN bus 10.

[0035] In this embodiment, ECU4 performs the well-known skyhook control for controlling the attitude of the vehicle body B. If vehicle body B is considered a rigid body, the installation positions of the sprung mass acceleration sensors 21, 22, and 23 and the positions directly above the four wheels of vehicle body B are known. Therefore, the vertical acceleration at any position on vehicle body B can be determined from the vertical accelerations of three different points on vehicle body B detected by the sprung mass acceleration sensors 21, 22, and 23. Accordingly, ECU4 calculates the vertical acceleration of vehicle body B directly above each of the four wheels from the vertical accelerations of vehicle body B detected by the sprung mass acceleration sensors 21, 22, and 23, determines the damping force to be generated by the shock absorber 1, and generates a control command to be given to the current control unit 5 to generate this determined damping force in the shock absorber 1, and outputs it to the CAN bus 10.

[0036] More specifically, the ECU4 calculates the vertical velocity of the vehicle body B directly above the four wheels by integrating or filtering the vertical acceleration of the vehicle body B directly above the four wheels, which is obtained from the acceleration detected by the sprung mass acceleration sensors 21, 22, and 23. It then multiplies each of these vertical velocities by a skyhook damping coefficient to determine the damping force that the shock absorbers 1 at each of the four wheels should generate. Furthermore, the ECU4 generates a control command to instruct the current control unit 5 to generate the damping force at each of the four wheels that it has calculated, and outputs this control command to the CAN bus 10. Upon receiving the control command via the CAN bus 10, the current control unit 5 supplies current to the solenoid valve 3 according to the control command.

[0037] In this embodiment, the ECU4 performs skyhook control, but it may also determine the damping force that the shock absorber 1 should generate according to a control law other than skyhook control and generate a control command. Furthermore, if a three-axis gyro sensor is installed on the vehicle body B and the angular velocity of the three axes at the center of gravity of the vehicle body B can be obtained from the CAN bus 10, the ECU4 may determine the vertical velocity directly above the four wheels of the vehicle body B from the angular velocity of the three axes at the center of gravity of the vehicle body B.

[0038] Next, in this embodiment, the current control unit 5, as shown in Figure 3, is configured to include a CAN interface 5a for exchanging information via the CAN bus 10, a control calculation unit 5b for generating current commands to control the solenoid valve 3, an unsprung acceleration sensor 5c, and a drive circuit 5d that supplies current to the solenoid 3c according to the current commands generated by the control calculation unit 5b. The current control unit 5 is installed in the shock absorber body 2. The current control unit 5 receives power through a power line connected to a battery (not shown) of the vehicle V.

[0039] The CAN interface 5a is connected to the CAN bus 10 via a connector 50 through a signal line S, and communicates via the CAN bus 10 through CAN communication. ECUInformation can be exchanged with 4. In Figure 1, the connector 50 connecting the CAN bus 10 and the signal line S is shown as a black circle. The current control unit 5 only needs to be able to receive control commands from the ECU 4, so it may receive control commands via a signal line directly connected to the ECU 4, or it may receive control commands from the ECU 4 via wireless communication, in addition to the CAN bus 10.

[0040] In this embodiment, the unsprung acceleration sensor 5c is an acceleration sensor capable of detecting acceleration in three mutually orthogonal axes, and since the current control unit 5 is installed in the shock absorber body 2 connected to the wheel W, it can detect the acceleration of the wheel W.

[0041] The control calculation unit 5b determines the target current based on the control command received from the ECU 4 via the CAN bus 10 and the acceleration detected by the unsprung acceleration sensor 5c. Specifically, the control calculation unit 5b includes an acceleration calculation unit 5b1 that determines the vertical acceleration of the wheel W from the three-axis acceleration detected by the unsprung acceleration sensor 5c, a damping force calculation unit 5b2 that determines the target damping force from the damping force instructed by the control command and the vertical acceleration of the wheel W determined by the acceleration calculation unit 5b1, a current command calculation unit 5b3 that generates a current command that instructs the amount of current to be supplied to the solenoid 3c of the solenoid valve 3 from the target damping force, a current control unit 5b4 that outputs a PWM signal to the drive circuit 5d when it receives a current command from the current command calculation unit 5b3, and an abnormality diagnosis unit 5b5.

[0042] The acceleration calculation unit 5b1 determines the vertical acceleration of the wheel W from the three-axis accelerations detected by the unsprung acceleration sensor 5c. Since the shock absorber body 2 is rarely mounted perpendicular to the vehicle V and is often installed at an angle, even if the current control unit 5 is installed so that one of the three detection axes of the unsprung acceleration sensor 5c is aligned with the axis of the cylinder 6, it is difficult to accurately detect the vertical acceleration of the wheel W. Therefore, the acceleration calculation unit 5b1 uses a rotation matrix to determine the vertical acceleration of the wheel W from the three accelerations detected by the unsprung acceleration sensor 5c. The rotation matrix is ​​a matrix used to convert the three-axis accelerations of the unsprung acceleration sensor 5c into accelerations in the front, rear, left, right, up, and down directions of the vehicle V.

[0043] Each component of the rotation matrix can be determined using the pitch angle, roll angle, and yaw angle of the three detection axes of the unsprung acceleration sensor 5c with respect to the vehicle V in the up, down, left, right, front, and rear directions as parameters. The acceleration calculation unit 5b1 can accurately determine the vertical acceleration of the wheel W from the acceleration detected by the unsprung acceleration sensor 5c by using the rotation matrix.

[0044] The pitch angle, roll angle, and yaw angle of the three detection axes of the unsprung acceleration sensor 5c are aligned with the orientation of one of the detection axes of the unsprung acceleration sensor 5c relative to the vehicle V. forceIf the direction of acceleration is known, it can be determined. For example, if the current control unit 5 is attached to the cylinder 6 so that one of the three detection axes of the unsprung acceleration sensor 5c is pointed towards the front of the vehicle V, the direction of one detection axis can be determined, and the direction of gravitational acceleration can be determined from the direction of acceleration detected by the unsprung acceleration sensor 5c when the vehicle V is stationary, so the pitch angle, roll angle and yaw angle can be determined. The rotation matrix parameters can be determined from the pitch angle, roll angle and yaw angle of the three detection axes of the unsprung acceleration sensor 5c determined in this way, so the acceleration calculation unit 5b1 uses this rotation matrix to determine the vertical acceleration of the wheel W from the three accelerations detected by the unsprung acceleration sensor 5c. The method for determining the pitch angle, roll angle and yaw angle is just one example, and other methods may be used.

[0045] In this embodiment, the acceleration calculation unit 5b1 performs calculations to determine the pitch angle, roll angle, and yaw angle to obtain a rotation matrix, and the acceleration of the three axes detected by the unsprung acceleration sensor 5c is acquired at a predetermined sampling rate to determine the vertical acceleration of the wheel W. The calculations to determine the pitch angle, roll angle, and yaw angle can be computationally intensive, so these calculations are performed by the acceleration calculation unit 5b1. However, once the components of the rotation matrix are determined, the calculation to determine the vertical acceleration of the wheel W from the acceleration of the three axes detected by the unsprung acceleration sensor 5c is computationally intensive. Therefore, after determining the components of the rotation matrix, the unsprung acceleration sensor 5c may calculate the vertical acceleration of the wheel W from the acceleration of the three axes it detects and output it to the damping force calculation unit 5b2, etc. Alternatively, the acceleration calculation unit 5b1 may be abolished, and the unsprung acceleration sensor 5c may calculate the rotation matrix and determine the vertical acceleration of the wheel W.

[0046] Furthermore, the vertical acceleration of the wheel W determined by the acceleration calculation unit 5b1 or the unsprung acceleration sensor 5c may be transmitted to the ECU4 via the CAN bus 10 from the CAN interface 5a. In this way, the ECU4 can obtain information on the vertical acceleration of the wheel W, which is an unsprung member, and can control the shock absorber 1 taking into account the vertical acceleration of the wheel W. Since the information on the vertical acceleration of the wheel W is useful for understanding the condition of the road surface on which the vehicle V has traveled, the acceleration information may also be stored in a storage device (not shown) connected to the CAN bus 10 in addition to the ECU4. Note that the 3-axis acceleration information detected by the unsprung acceleration sensor 5c may also be transmitted to the ECU4 via the CAN interface 5a.

[0047] The damping force calculation unit 5b2 determines the target damping force based on the damping force instructed by the control command and the vertical acceleration of the wheel W obtained by the acceleration calculation unit 5b1. Specifically, in this embodiment, the damping force calculation unit 5b2 processes the vertical acceleration of the wheel W with a low-pass filter to average it, determines the road surface conditions on which the vehicle V is traveling, and multiplies the damping force instructed by the control command by a gain corresponding to the road surface conditions to determine the target damping force. The average value of the vertical acceleration of the wheel W changes according to the unevenness of the road surface on which the vehicle V is traveling, and serves as an indicator for understanding the road surface conditions. It takes a small value on good roads with few bumps, a medium value on rough roads with relatively many bumps, and a large value on extremely rough roads with many bumps and high bumps.

[0048] In this embodiment, the ECU4 determines the damping force that the shock absorber 1 should generate according to the vertical speed of the vehicle body B, which acts as a sprung mass member, regardless of the road surface conditions. Therefore, on rough or extremely rough roads, it may be better to lower the damping force generated by the shock absorber 1 to suppress the transmission of vibration input from the road surface to the vehicle body B. Accordingly, the damping force calculation unit 5b2 sets threshold values ​​for determining rough roads and extremely rough roads based on the average value of the vertical acceleration of the wheels W, and determines whether the road surface on which the vehicle V is currently traveling corresponds to a good road, a rough road, or an extremely rough road by comparing the average value with each threshold value. Gains to be used when driving on a good road, a rough road, and an extremely rough road are prepared in advance, and the damping force calculation unit 5b2 selects a gain according to the determined road surface conditions based on the road surface determination result, and corrects the damping force instructed by the control command by multiplying the damping force instructed by the control command by the selected gain to obtain the target damping force.

[0049] Furthermore, when the wheel W crosses over a large bump, a large vertical acceleration acts on the wheel W. If the damping force generated by the shock absorber 1 is high when crossing such bumps, the vibration of the wheel W is transmitted to the vehicle body B, worsening the ride comfort in the vehicle V. Therefore, in parallel with the control that selects a gain according to the road surface condition determined by the average value of the vertical acceleration of the wheel W, the damping force calculation unit 5b2 performs vibration reduction control to reduce the impact shock when the wheel W suddenly crosses over a large bump. For this control, a vibration reduction gain to be used for vibration reduction control is prepared in advance, and when the absolute value of the vertical acceleration of the wheel W exceeds a predetermined threshold, the damping force calculation unit 5b2 compares the vibration reduction gain and the gain selected according to the road surface condition, selects the lower of the two gains, and multiplies the damping force instructed by the control command by the lower gain to obtain the target damping force. Furthermore, if the vibration reduction gain is set to a lower value than other gains, the damping force calculation unit 5b2 may calculate the target damping force by multiplying the vibration reduction gain by the damping force instructed by the control command when the absolute value of the vertical acceleration of the wheel W exceeds a predetermined threshold.

[0050] The process of determining the target damping force in the damping force calculation unit 5b2 described above is merely an example and is not limited to the example described above. Therefore, the damping force calculation unit 5b2 may only perform control that determines the road surface conditions and selects the optimal gain to determine the target damping force, or it may only perform vibration reduction control, or it may use the vertical acceleration of the vehicle W to perform control other than the control described above.

[0051] Furthermore, when the vertical acceleration of the wheel W obtained by the acceleration calculation unit 5b1 or the unsprung acceleration sensor 5c is transmitted to the ECU4 via the CAN bus 10, the ECU4 may, instead of the damping force calculation unit 5b2, take into account the vibration conditions of the wheel W to determine the target damping force, and input a control command to the current control unit 5 via the CAN bus 10 from the ECU4 to indicate the target damping force. In this case, the damping force calculation unit 5b2 in the control calculation unit 5b may be abolished. Note that if the vertical acceleration of the wheel W is obtained, the ECU4 may integrate the vertical acceleration of the wheel W at each of the four wheels transmitted from the current control unit 5 of the shock absorbers 1 located at each of the four wheels to determine the vertical velocity of each wheel W. When the difference between the vertical velocity of the vehicle body B directly above the four wheels, calculated from the acceleration detected by the sprung acceleration sensors 21, 22, and 23, and the corresponding vertical velocity of each wheel W is calculated, each of the four differences will approximately coincide with the stroke velocity of the shock absorbers 1 at each of the four wheels. The ECU4 can determine the direction of the stroke of the shock absorber 1 by calculating the difference, and then, after determining the damping force that each shock absorber 1 should generate according to the Skyhook control law, it can determine, based on the difference, whether each shock absorber 1 is in a position to generate the determined damping force. When the shock absorber 1 is extended, it can generate a damping force in the direction that hinders extension, but cannot generate a damping force in the direction that promotes extension, and conversely, when it is compressed, it can generate a damping force in the direction that hinders compression, but cannot generate a damping force in the direction that promotes compression. In this way, the ECU4 can determine the direction of the stroke of the shock absorber 1, and if the direction of the damping force determined using the Skyhook control law is the direction in which the shock absorber 1 can generate a damping force according to the stroke state of the shock absorber 1, then the damping force determined using the Skyhook control law is used as is. instructionsThe ECU generates a control command. On the other hand, if the direction of the damping force determined using the Skyhook control law is in a direction in which the shock absorber 1 cannot generate damping force due to the stroke condition of the shock absorber 1, the ECU generates a control command that minimizes the damping force regardless of the damping force determined using the Skyhook control law. In other words, if the vertical acceleration of the wheel W can be obtained from the current control unit 5, the ECU can execute control that instructs the damping force of the shock absorber 1 in accordance with Carnopp's law. Note that the ECU may also generate control commands using control laws other than Carnopp's law.

[0052] Next, the current command calculation unit 5b3 has a map in which it has a relationship between the damping force generated by the buffer 1 and the amount of current supplied to the solenoid valve 3. Using the target damping force determined by the damping force calculation unit 5b2, it calculates the amount of current to be supplied to the solenoid 3c of the solenoid valve 3 using the map. Although the current command calculation unit 5b3 uses a map to determine the amount of current, it may also use a function to determine the amount of current if the relationship between the damping force and the amount of current can be expressed as a function. In this way, the current command calculation unit 5b3 generates a current command that indicates the determined amount of current.

[0053] The map used in the current command calculation unit 5b3 is set based on design values. However, after assembling the shock absorber 1 and before shipping, the damping force actually generated by the shock absorber 1 is measured in relation to the amount of current supplied to the solenoid valve 3. The map parameters are then corrected so that the actual damping force of the shock absorber 1 accurately matches the amount of current supplied to the solenoid valve 3. This process is performed for each product before the shock absorber 1 is shipped, thus suppressing variations in the damping force generated by the shock absorber 1 in relation to the amount of current supplied to the solenoid valve 3 between products. Therefore, the ECU 4 does not need to correct the damping force for each shock absorber 1 located at each of the four wheels of the vehicle V to suit the shock absorber 1 being controlled, and there is no need to perform the damping force correction work between the ECU 4 and the four shock absorbers 1. Furthermore, even if the ECU 4 and the shock absorber 1 are manufactured by different companies, product-to-product variations in damping force can be suppressed by correcting only the shock absorber 1. Therefore, the correction work can be performed without connecting the shock absorber 1 to the ECU 4.

[0054] The current control unit 5b4 calculates the difference between the current command calculated by the current command calculation unit 5b3 and the actual amount of current supplied to the solenoid 3c. It then performs PI compensation and PID compensation on the difference to determine the target current, and outputs a PWM signal to the drive circuit 5d to supply current to the solenoid 3c of the solenoid valve 3 according to the target current. In other words, the current control unit 5b4 controls the solenoid valve 3 by current feed control. The current control unit 5b4 obtains information about the current flowing through the solenoid 3c from the current sensor provided by the drive circuit 5d.

[0055] The abnormality detection unit 5b5 monitors the vertical acceleration of the wheel W obtained by the acceleration calculation unit 5b1 and determines an abnormality in the shock absorber 1. Specifically, for example, if the shock absorber 1 is unable to generate damping force according to the target damping force, the vibration level (peak value) of the wheel W will increase. Therefore, the abnormality detection unit 5b5 calculates the moving average of the absolute values ​​of the sequentially sampled accelerations of the wheel W, and if this moving average exceeds a preset abnormality threshold, it determines that there is an abnormality in the shock absorber 1 and generates an abnormality signal. The abnormality signal is transmitted from the CAN interface 5a to the CAN bus 10 and then to the ECU 4. When the ECU 4 receives the abnormality signal, it stops controlling the shock absorber 1 and, in order to make the vehicle occupants aware of the abnormality, for example, by illuminating a warning light installed on the instrument panel (not shown) or outputting a warning sound from a speaker (not shown). In this way, the abnormality detection unit 5b5 detects abnormalities based on the acceleration detected by the unsprung acceleration sensor 5c, so it can detect abnormalities due to deterioration of the shock absorber body 1 or mechanical abnormalities of the shock absorber body 1.

[0056] Furthermore, the abnormality detection unit 5b5 may, in addition to making abnormality judgments based on the vertical acceleration of the wheel W, or alternatively, detect electrical abnormalities in the current control unit 5 or solenoid valve 3, such as overvoltage, overheating, or open circuits in the drive circuit 5d, and output an abnormality signal.

[0057] The control calculation unit 5b, configured as described above, includes, as hardware, an arithmetic processing unit such as an MPU (Micro Processor Unit), a memory that provides a program for executing processing in the control calculation unit 5b and a storage area necessary for processing by the arithmetic processing unit, and a bus line for exchanging signals with the CAN interface 5a, the unsprung acceleration sensor 5c, and the drive circuit 5d. The control calculation unit 5b realizes the acceleration calculation unit 5b1, the damping force calculation unit 5b2, the current command calculation unit 5b3, the current control unit 5b4, and the abnormality diagnosis unit 5b5 by having the arithmetic processing unit execute the program.

[0058] Next, the drive circuit 5d includes a switching element (not shown) for adjusting the amount of current supplied to the solenoid 3c. The switching element is turned on and off according to the duty cycle indicated by the PWM signal received from the current control unit 5b4, thereby adjusting the amount of current supplied to the solenoid 3c to the target current.

[0059] In the buffer 1 configured as described above, the current control unit 5 receives control commands from the ECU 4 and controls the solenoid valve 3. Therefore, the current control unit 5 and the ECU 4 only need to be connected by a signal line that exchanges signals. Furthermore, since the current amount of the solenoid valve 3 is controlled by the current control unit 5, no switching current flows between the battery (not shown) and the current control unit 5. Switching current flows only in the wiring between the current control unit 5 and the solenoid valve 3.

[0060] Furthermore, since the current control unit 5 in the shock absorber 1 is equipped with an unsprung acceleration sensor 5c, there is no need to install an unsprung acceleration sensor on the suspension member or the like to detect the acceleration of the wheels W, which are unsprung components of the vehicle V, and the ECU 4 and unsprung weight It does not require a dedicated signal line for the unsprung acceleration sensor 5c to directly connect to the acceleration sensor 5c.

[0061] Furthermore, in the buffer 1 of this embodiment, the current control unit 5 is equipped with a CAN interface 5a, so control commands can be sent from the ECU 4 via the CAN bus 10. ra This can be done. Since the CAN bus 10 is spread throughout the vehicle body B, the current control unit 5 in the buffer 1 can be connected to the wiring of the CAN bus 10 which is located very close to the buffer 1, so the signal line S connecting the buffer 1 and the CAN bus 10 can be very short.

[0062] As described above, the shock absorber 1 of this embodiment includes a shock absorber body 2 having a cylinder 6 connected to the wheel (unsprung member) W of the vehicle V and a rod 8 that moves in and out of the cylinder 6 and is movable relative to the cylinder 6 and is connected to the vehicle body (sprung member) B of the vehicle V; a solenoid valve (damping force adjustment device) 3 that can adjust the damping force generated when the shock absorber body 2 expands and contracts according to the amount of current supplied; and a current control unit 5 attached to the cylinder 6 that supplies current to the solenoid valve (damping force adjustment device) 3 based on control commands received from an ECU (control unit) 4 mounted on the vehicle V, and the current control unit 5 is equipped with an unsprung acceleration sensor 5c.

[0063] In the buffer 1 configured in this way, the current control unit 5, which receives control commands from the onboard ECU (control unit) 4, controls the solenoid valve (damping force adjustment device) 3. Therefore, the current control unit 5 and the ECU (control unit) 4 only need to be connected via signal lines, eliminating the need to connect the ECU (control unit) 4 and the current control unit 5 with a harness to supply switching current to the solenoid valve (damping force adjustment device) 3.

[0064] Therefore, according to the shock absorber 1 of this embodiment, a harness for switching current to connect to the ECU (control unit) 4 is not required, so at least 4 sets of harnesses can be reduced in total for the vehicle V, thereby reducing the weight of the vehicle V. Furthermore, according to the shock absorber 1 of this embodiment, a harness for switching current, which is a source of noise, is not required between the ECU (control unit) 4 and the current control unit 5, so other equipment in the vehicle V will not be affected by noise. Moreover, since the current control unit 5 is equipped with an unsprung mass acceleration sensor 5c, the installation of the unsprung mass acceleration sensor 5c is completed simply by installing the shock absorber 1 in the vehicle V, and there is no need to directly connect the unsprung mass acceleration sensor 5c to the ECU (control unit) 4, and vibration of the wheel (unsprung mass member) W can be detected, thus simplifying the installation work of the unsprung mass acceleration sensor 5c.

[0065] Based on the above, the shock absorber 1 of this embodiment does not increase the weight of the vehicle, can suppress the generation of noise, and can detect vibrations of the wheels (unsprung mass) W without requiring troublesome installation work.

[0066] Furthermore, according to the shock absorber 1 of this embodiment, the current control unit 5 is equipped with an unsprung acceleration sensor 5c, so the acceleration of the wheel (unsprung member) W can be transmitted to the ECU (control unit) 4, and the acceleration of the wheel (unsprung member) W can be used for control or to understand the condition of the road surface on which the vehicle V has traveled.

[0067] Furthermore, in the shock absorber 1 of this embodiment, the current control unit 5 is equipped with a CAN interface 5a. With the shock absorber 1 configured in this way, it is possible to receive control commands from the ECU (control unit) 4 via the CAN bus 10, and the current control unit 5 can also transmit information on the acceleration of the wheels (unsprung mass) W to the ECU (control unit) 4 via the CAN bus 10. Since the CAN bus 10 is spread throughout the vehicle body B, the current control unit 5 in the shock absorber 1 can be connected to the wiring of the CAN bus 10 which is located very close to the shock absorber 1, so the signal line S connecting the shock absorber 1 and the CAN bus 10 can be very short. Furthermore, there is no need to install a dedicated connector in the ECU (control unit) 4 for connecting to the signal line S of the current control unit 5, so the ECU (control unit) 4 can be made smaller and lighter.Therefore, with the shock absorber 1 configured in this way, the signal line S can be shortened by utilizing the CAN bus 10, so the weight of the vehicle V can be further reduced.

[0068] Furthermore, when the current control unit 5 receives control commands via the CAN bus 10, it is optimal when the ECU (control unit) 4 is an integrated ECU used for controlling the engine and other functions of the vehicle V.

[0069] Furthermore, when the current control unit 5 transmits the acceleration detected by the unsprung acceleration sensor 5c to the CAN bus 10 via the CAN interface 5a, the acceleration information becomes available to the ECU (control unit) 4 and other devices mounted on the vehicle V, and this acceleration information can be used to control the shock absorber 1 and to understand the road surface conditions.

[0070] Furthermore, in the shock absorber 1 of this embodiment, the current control unit 5 corrects the damping force instructed by the control command based on the acceleration detected by the unsprung acceleration sensor 5c to determine the target damping force, and supplies current to the solenoid valve (damping force adjustment device) 3 based on the target damping force. With the shock absorber 1 configured in this way, vibrations input from the road surface on which the vehicle V is traveling can be detected as quickly as possible using the unsprung acceleration sensor 5c, so the damping force of the shock absorber 1 can be optimally corrected according to the input from the road surface. Therefore, with the shock absorber 1 configured in this way, the ride comfort and wheel contact performance of the vehicle V can be improved.

[0071] Furthermore, the current control unit 5 in the shock absorber 1 of this embodiment detects abnormalities based on the acceleration detected by the unsprung acceleration sensor 5c. With the shock absorber 1 configured in this way, abnormalities are detected by utilizing the acceleration detected by the unsprung acceleration sensor 5c, so abnormalities due to deterioration of the shock absorber body 1 or mechanical abnormalities of the shock absorber body 1 can be detected.

[0072] As mentioned above, the current control unit 5 is equipped with a CAN interface 5a and is capable of CAN communication with the ECU 4. However, as shown in the modified example buffer 1 in Figure 4, it may be equipped with a wireless communication device 30 instead of the CAN interface 5a.

[0073] If the current control unit 5 is equipped with a communication device 30 but does not have a CAN interface 5a, the onboard ECU (control unit) 4 should also be equipped with a communication device 31 that can communicate wirelessly with the current control unit 5, enabling the exchange of control commands, information on the acceleration of the wheels (unsprung mass) W, and abnormal signals via the communication devices 30 and 31. With the shock absorber 1 configured in this way, if the current control unit 5 is equipped with a communication device 30, communication with the ECU (control unit) 4 can be done wirelessly only, eliminating the need for signal lines altogether, thus further reducing the weight of the vehicle V.

[0074] Furthermore, if the current control unit 5 is equipped with a communication device 30, as shown in Figure 5, it may be configured to communicate with an air pressure sensor 40 that detects air pressure in the wheels W of the vehicle V via the communication device 30, and to transfer the air pressure information detected by the air pressure sensor 40 received via the communication device 30 to the ECU (control unit) 4.

[0075] The current control unit 5 receives constant power from a battery (not shown), and can reliably communicate wirelessly using the communication device 30. Meanwhile, the air pressure sensor 40 is attached to the wheel W, operates on its own battery, and transmits the air pressure inside the tire of the wheel W detected via wireless communication to the outside. When the communication device 31 on the ECU 4 directly communicates wirelessly with the air pressure sensors 40 on the four wheels W of the vehicle V, the distance between the communication device 31 and all the air pressure sensors 40 may be large. Therefore, unless the electric field strength of the radio waves transmitted from the air pressure sensor 40 is increased to a certain extent, the ECU 4 and the air pressure sensors 40 will not be able to communicate. However, increasing the electric field strength on the air pressure sensor 40 side increases power consumption, which shortens the time that the air pressure sensor 40 can continuously transmit air pressure with a fully charged battery.

[0076] In contrast, in this embodiment, the current control unit 5 is installed in the shock absorber body 2, which is located in close proximity to the wheel W. Since the wireless device 30 can be placed in close proximity to the pneumatic sensor 40 on the wheel W, the current control unit 5 can receive the pneumatic pressure signal transmitted from the pneumatic sensor 40 even if the electric field strength of the radio waves transmitted from the pneumatic sensor 40 is lower than in the conventional design. When the current control unit 5 receives the pneumatic pressure signal from the pneumatic sensor 40, it transmits the pneumatic pressure information received from the pneumatic sensor 40 to the ECU 4 via the wireless device 30. The current control unit 5 is powered by a battery (not shown) in the vehicle V, enabling stable wireless communication with the ECU 4. The buffer 1 configured in this way can communicate with the air pressure sensor 40, which detects the air pressure in the wheels W of the vehicle V, via the communication device 30. The air pressure information detected by the air pressure sensor 40, received via the communication device 30, is transferred to the ECU (control unit) 4. Therefore, even if the electric field strength of the radio waves output by the air pressure sensor 40 is reduced, the current control unit 5 is positioned close to the air pressure sensor 40, allowing the current control unit 5 to receive the air pressure information detected by the air pressure sensor 40 and transfer it to the ECU (control unit) 4. Thus, the buffer 1 configured in this way can reduce the power consumption of the air pressure sensor 40 and extend the time that the air pressure sensor 40 can continuously transmit.

[0077] In one modified example of the buffer 1, the current control unit 5 is equipped with a communication device 30 instead of a CAN interface 5a, but the current control unit 5 may also be equipped with both a CAN interface 5a and a communication device 30.

[0078] 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. [Explanation of Symbols]

[0079] 1... Shock absorber, 2... Shock absorber body, 3... Solenoid valve (damping force adjustment device), 4... ECU (control unit), 5... Current control unit, 5a... CAN interface, 5c... Unsprung acceleration sensor, 6... Cylinder, 8... Rod, 10... CAN bus, 30... Communication device, 40... Pneumatic sensor, 50... Connector, V... Vehicle, W... Wheel (unsprung component)

Claims

1. A shock absorber body having a cylinder connected to the unsprung member of the vehicle and a rod that moves in and out of the cylinder and is movable relative to the cylinder and is connected to the sprung member of the vehicle, A damping force adjustment device capable of adjusting the damping force generated by the shock absorber body according to the amount of current supplied, The cylinder is fitted with a current control unit that supplies current to the damping force adjustment device based on a control command received from a control device mounted on the vehicle, The current control unit has an unsprung acceleration sensor and corrects the damping force instructed by the control command based on the acceleration detected by the unsprung acceleration sensor to determine a target damping force, and supplies current to the damping force adjustment device based on the target damping force. A buffer characterized by the following features.

2. A shock absorber body having a cylinder connected to the unsprung member of the vehicle and a rod that moves in and out of the cylinder and is movable relative to the cylinder and is connected to the sprung member of the vehicle, A damping force adjustment device capable of adjusting the damping force generated by the shock absorber body according to the amount of current supplied, The cylinder is fitted with a current control unit that supplies current to the damping force adjustment device based on a control command received from a control device mounted on the vehicle, The current control unit has an unsprung acceleration sensor and a communication device capable of wireless communication, and is capable of communicating with an air pressure sensor that detects the air pressure in the vehicle's wheels via the communication device, and transfers the air pressure information detected by the air pressure sensor received via the communication device to the control device. A buffer characterized by the following features.

3. The current control unit has a CAN interface. The shock absorber according to feature 1 or 2.

4. The current control unit receives the control command via the vehicle's CAN bus. The shock absorber according to feature 3.

5. The current control unit transmits the acceleration detected by the unsprung acceleration sensor to the CAN bus via the CAN interface. The shock absorber according to feature 4.

6. The current control unit detects an abnormality based on the acceleration detected by the unsprung acceleration sensor. The shock absorber according to feature 1 or 2.

7. The current control unit has a communication device capable of wireless communication. The shock absorber according to feature 1.

Images