Damping force control device and damping force control method

Abstract

To accurately estimate oil temperature of a shock absorber (damper).SOLUTION: A damping force control device (suspension ECU 21) controlling damping force of a damper of a vehicle comprises: an operation value calculation part 211 which calculates operation amount of the damper, operation time of the damper, operation speed of the damper and input frequency into unsprung mass of the vehicle; an operation frequency calculation part 212 which calculates operation frequency of the damper based on the input frequency; an oil temperature estimation part 213 which estimates oil temperature of the damper at least based on the operation amount of the damper, the operation time, the operation speed, and the operation frequency; and a control value calculation part 214 which calculates a control value to adjust the damping force at least according to the oil temperature.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a damping force control device and a damping force control method. [Background technology]

[0002] Shock absorbers (hereafter referred to as dampers) generate heat when damping vibrations, causing the temperature of the hydraulic oil inside to rise. If the temperature of the hydraulic oil (hereafter referred to as oil temperature) exceeds a certain temperature, the damping force of the damper will decrease, so this is prevented by detecting the oil temperature. However, installing a sensor to directly detect the oil temperature is difficult in terms of cost and manufacturing efficiency, and for this reason, the oil temperature is currently estimated based on other detected values.

[0003] Patent Document 1 introduces an oil temperature estimation device that estimates the oil temperature of a damper using variables such as the sprung weight, the vertical acceleration of the sprung mass, and the relative velocity calculated from the differential value of the relative displacement between the sprung and unsprung mass. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-274138 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the oil temperature detection device introduced in Patent Document 1, due to the nature of the damper, which converts kinetic energy into heat, the oil temperature rises as the number of times it operates increases, even for the same sprung mass, relative velocity between the sprung and unsprung mass, and vertical acceleration of the sprung mass. Conventionally, the frequency of damper operation, which is affected by oil temperature, has not been taken into consideration, and there was room for improvement in the method of estimating oil temperature, which is performed continuously while the vehicle is running.

[0006] One object of the present invention is to provide a damping force control device and a damping force control method that are capable of more accurately estimating the oil temperature inside the damper. Other objects of the present invention will become apparent to those skilled in the art by referring to the following exemplary aspects and best modes, as well as the accompanying drawings. [Means for solving the problem]

[0007] In order to facilitate an understanding of the outline of the present invention, the following examples are given of embodiments according to the present invention.

[0008] In an aspect according to the present invention, a damping force control device that controls the damping force of a damper provided in a vehicle includes an operation value calculation unit that calculates the operation amount of the damper, the operation time of the damper, the operation speed of the damper, and an input frequency to the unsprung mass of the vehicle; an operation frequency calculation unit that calculates the operation frequency of the damper from the input frequency; an oil temperature estimation unit that estimates the oil temperature of the damper using at least the operation amount, the operation time, the operation speed, and the operation frequency; and a control value calculation unit that adjusts the damping force in accordance with at least the oil temperature.

[0009] According to the first aspect, it is possible to provide a damping force control device that is capable of more accurately estimating the oil temperature inside the damper.

[0010] Those skilled in the art will easily understand that the exemplified embodiments according to the present invention can be further modified without departing from the spirit of the present invention. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram schematically illustrating an example of the configuration of a vehicle to which a damping force control device and a damping force control method according to a first embodiment of the present invention are applied. [Figure 2] 1 is a side view showing the configuration of a suspension device according to a first embodiment of the present invention. [Figure 3] 1 is a cross-sectional view showing the configuration of a hydraulic shock absorber according to a first embodiment of the present invention. [Figure 4] 1 is a cross-sectional view showing the configuration of a solenoid valve according to a first embodiment of the present invention. [Figure 5] 1 is a block diagram showing an example of a functional configuration of a damping force control device according to a first embodiment of the present invention. [Figure 6] FIG. 4 is a diagram illustrating an example of a map showing the correlation between oil temperature and a damping force adjustment coefficient. [Figure 7] FIG. 10 is a diagram showing an example of a map for searching a target current from a damper speed and a target damping force. [Figure 8] 4 is a flowchart showing the operation of the damping force control device according to the first embodiment of the present invention. [Figure 9] FIG. 6 is a block diagram showing an example of the functional configuration of a damping force control device according to a second embodiment of the present invention. [Figure 10] 6 is a flowchart showing the operation of the damping force control device according to the second embodiment of the present invention. [Figure 11] 10 is a graph showing the relationship between the temperature of the electromagnetic coil and time for each value of current flowing through the electromagnetic coil. DETAILED DESCRIPTION OF THE INVENTION

[0012] The best mode described below is used to facilitate understanding of the present invention, and therefore, those skilled in the art should be aware that the present invention is not unduly limited by the embodiments described below.

[0013] [Embodiment 1] Hereinafter, a first embodiment of the present invention (hereinafter referred to as the first embodiment) will be described in detail.

[0014] FIG. 1 is a diagram showing a schematic example of the configuration of a vehicle 1 to which the damping force control device and damping force control method of the first embodiment are applied.

[0015] (Vehicle configuration) 1, a total of four wheels 3, 4, for example, left and right front wheels 3 and left and right rear wheels 4 (only one shown), are provided on the underside of a vehicle body that constitutes the body of a vehicle 1. Front-wheel suspension devices 5, 5 (hereinafter referred to as front wheel suspensions 5) are provided between the left and right front wheels 3 and the vehicle body, respectively. The front wheel suspensions 5 include suspension springs 6 (hereinafter referred to as springs 6) and adjustable damping shock absorbers (dampers 7) provided in parallel with the springs 6.

[0016] Rear-wheel suspension devices 8, 8 (hereinafter referred to as rear wheel suspensions 8) are provided between the left and right rear wheels 4 and the vehicle body. The rear wheel suspensions 8 include suspension springs 9 (hereinafter referred to as springs 9) and adjustable damping shock absorbers (dampers 10) provided in parallel with the springs 9. The dampers 7, 10 are configured, for example, by semi-active dampers that are hydraulic cylinder devices (variable damping shock absorbers) that allow for adjustable damping force. In other words, the vehicle 1 is equipped with a semi-active suspension system that uses variable damping shock absorbers.

[0017] Here, the dampers 7, 10 are variable damping force generating devices (variable damping force shock absorbers) provided between the body and the wheels 3, 4 of the vehicle 1. The dampers 7, 10 have their generated damping force characteristics (damping force characteristics) variably controlled by an ECU (typically, a suspension ECU 21) as a damping force control device. For this purpose, the dampers 7, 10 are provided with actuators (215 in FIG. 5, described later) including a damping force adjustment valve and a solenoid, etc., to continuously (or in multiple stages) adjust the damping force characteristics from hard characteristics (hard characteristics) to soft characteristics (soft characteristics). The dampers 7, 10 have their damping force characteristics variably adjusted in accordance with a control command value (current) supplied from the suspension ECU 21 to the actuator 215 (FIG. 5).

[0018] The damping force adjustment valve may employ a conventionally known structure, such as a pressure control system that controls the pilot pressure of a damping force generating valve or a flow control system that controls the passage area. The dampers 7 and 10 may be any type capable of continuously (or multi-stagely) adjusting the damping force, such as a pneumatic damper, an electromagnetic damper, an electrorheological fluid damper, or a magnetic fluid damper. The dampers 7 and 10 may also be air dampers (air suspensions) using air springs, hydraulic dampers (height control devices) in which front, rear, left, and right hydraulic cylinders are connected by piping, or stabilizers that apply force to the movement of the left and right wheels. Furthermore, the dampers 7 and 10 may be fully active dampers composed of hydraulic, electric, or pneumatic actuators capable of generating thrust. In other words, the vehicle 1 may be equipped with a fully active suspension system using a fully active damper.

[0019] Next, various sensors S for detecting the state of the vehicle 1 11 ,S 12 ,S 13 ,S 14 ,S 15 , S 16 We will explain about this.

[0020] As shown in FIG. 1, the vehicle 1 is equipped with a vehicle speed sensor S 11 , wheel speed sensor S 12 , Front and rear acceleration sensor S 13 , lateral acceleration sensor S 14 , steering angle sensor S 15 , and displacement sensor S 16 Each of these sensors S 11 ,S 12 ,S 13 ,S 14 ,S 15 ,S 16 is a sensor mounted on the vehicle 1 as an example of the behavior sensor S shown in FIG. 5. More specifically, it is a sensor mainly used to control the braking, driving, and steering of the vehicle 1.

[0021] Vehicle speed sensor S 11is provided, for example, on an output shaft (not shown) of a transmission mounted on the vehicle 1. 11 The vehicle speed sensor S detects the vehicle speed of the vehicle 1 (vehicle body). 11 The detected information (signal corresponding to the vehicle speed) is output to a vehicle control ECU (other vehicle control ECUs (accelerator ECU, brake ECU, steering ECU, etc.) other than the suspension ECU 21) mounted on the vehicle 1 (vehicle body) via, for example, a CAN (Control Area Network) which is an in-vehicle LAN communication. Note that the vehicle control ECU is not shown in the figure.

[0022] Wheel speed sensor S 12 The wheel speed sensor S is provided, for example, on a wheel support hub unit (not shown) that supports the wheels 3 and 4. 12 are provided corresponding to the respective wheels 3 and 4. 12 detects the rotation speed of the wheels 3 and 4. Wheel speed sensor S 12 The information (wheel speed) is output to the vehicle control ECUs (accelerator ECU, brake ECU, steering ECU) and suspension ECU 21 via the CAN. 11 The wheel speed sensor S 12 The vehicle speed may be obtained from the wheel speed.

[0023] Front and rear acceleration sensor S 13 and lateral acceleration sensor S 14 is provided on the vehicle body, for example, on the sprung side of the vehicle 1. 13 The lateral acceleration sensor S detects the acceleration of the vehicle 1 (vehicle body) in the longitudinal direction. 14 detects the acceleration (lateral acceleration) in the left and right direction of the vehicle 1 (vehicle body). 13 The detection data (signal corresponding to the longitudinal acceleration) and the lateral acceleration sensor S 14 The detected data (signals corresponding to the lateral acceleration) is output to the vehicle control ECUs (accelerator ECU, brake ECU, steering ECU) and suspension ECU 21 via the CAN.

[0024] Steering angle sensor S 15 is provided, for example, on a steering wheel (not shown) of the vehicle 1. 15 The steering angle sensor S detects the steering angle (rotation angle) generated by the steering operation of the driver of the vehicle 1 or the steering angle of the wheels (front wheels 3). 15 The detected data (signal corresponding to the steering angle) is output to the vehicle control ECU (steering ECU) via the CAN.

[0025] Displacement Sensor S 16 For example, the displacement sensor S is attached to the sprung part to detect the relative displacement (stroke) of the unsprung part relative to the sprung part, and the tip of the arm extending from this is attached to the unsprung part or to a part that moves up and down together with the unsprung part. 16 The detected data of the displacement sensor S is output to the suspension ECU 21. 16 The displacement sensor S detects the relative displacement of the lower side of the spring relative to the upper side of the spring by detecting the inclination of the arm relative to the main body using a potentiometer or the like. 16 The vehicle height can also be calculated from the detection result. Furthermore, the displacement sensor may be of a type that directly measures the amount of expansion and contraction of the shock absorber itself, instead of the type described above.

[0026] In addition, the displacement sensor S 16 These behavior sensors (S 11 ~S 15 ) are typically not sensors dedicated to the suspensions 5, 8. That is, they are sensors mounted on the vehicle for purposes other than controlling the dampers 7, 10, in other words, sensors mounted on the vehicle to mainly control on-board devices other than the dampers 7, 10. Specifically, they are mounted on the vehicle 1 as sensors mainly for controlling the engine that drives and / or brakes the vehicle 1, the driving motor for driving, the vehicle braking / driving devices (accelerator, brake) such as hydraulic brakes and electric brakes, and the steering device such as the electric power steering device that steers the vehicle 1.

[0027] (Suspension 5, 8 configuration) FIG. 2 is a side view showing the configuration of the suspensions 5 and 8 in FIG. 1. The suspensions 5 and 8 have the same configuration, as an example. As shown in FIG. 2, the suspensions 5 and 8 include a hydraulic damper 101 (damper 7 and 10 in FIG. 1) and a coil spring 102 (spring 6 and 9 in FIG. 1) arranged on the outside of the hydraulic damper 101. The coil spring 102 is held between a spring seat 103 and a spring seat 104. One end of the suspension 5 is fixed to the vehicle body by a bolt 105, and the other end is attached to the axle of the wheels 3 and 4 via an axle-side mounting portion 106.

[0028] The shock that the vehicle 1 receives from the road surface is absorbed by the compression of the coil spring 102. The hydraulic damper 101 generates a force (damping force) that damps the kinetic energy of the coil spring 102.

[0029] Fig. 3 is a cross-sectional view showing the configuration of the hydraulic damper 101. As indicated by the arrows in the figure, Fig. 3(a) shows a compression-side stroke in which the piston rod 20 enters the first cylinder 11, and Fig. 3(b) shows an extension-side stroke in which the piston rod 20 retracts from the first cylinder. 3(a) and 3(b), the hydraulic damper 101 has a triple-tube structure in which a second cylinder 12 is disposed outside a first cylinder 11, and a damper case 13 is disposed further outside that. The first cylinder 11, the second cylinder 12, and the damper case 13 are arranged coaxially.

[0030] A piston rod 20 is inserted into the first cylinder 11, and a piston 30 disposed at the tip of the piston rod 20 slides against the inner wall surface of the first cylinder 11. Hydraulic oil is stored in the internal space of the first cylinder 11, and the internal space is divided by the piston 30 into a piston-side oil chamber A1 and a rod-side oil chamber A2.

[0031] A bottom unit 40 is provided at the axle side ends of the first cylinder 11 and the second cylinder 12, and a rod guide 15 is provided at the vehicle body side ends of the first cylinder 11 and the second cylinder 12. The bottom unit 40 and the rod guide 15 define both ends of the oil chamber formed inside the first cylinder 11 and the second cylinder 12.

[0032] The rod guide 15 has an opening 16 formed therein, into which a piston rod 20 is inserted.

[0033] An annular oil chamber A3 is formed between the outer wall surface of the first cylinder 11 and the inner wall surface of the second cylinder 12. A shared flow path 17 is formed between the rod guide 15 and the vehicle body side end of the first cylinder 11, and the annular oil chamber A3 and the rod side oil chamber A2 are in communication with each other via the shared flow path 17.

[0034] A reservoir chamber A4 is formed between the outer wall surface of the second cylinder 12 and the inner wall surface of the damper case 13. The reservoir chamber A4 stores hydraulic oil to compensate for the volume of the piston rod 20 moving in and out of the first cylinder 11.

[0035] A solenoid valve 50, which is an electromagnetic valve that adjusts the damping force generated in the hydraulic damper 101, is provided on the side of the damper case 13. The solenoid valve 50 is fixed by a valve stopper 551 to a side flow passage 57 that penetrates the wall surface of the second cylinder 12 and the wall surface of the damper case 13.

[0036] Hydraulic oil flows from the annular oil chamber A3 into the solenoid valve 50 through one opening of the side flow passage 57. A valve element 531 having a protrusion 531a is disposed in the other opening of the side flow passage 57. The valve element 531 adjusts the opening area of ​​a damping flow passage 561 that penetrates the wall surface of the side flow passage 57 and the valve stopper 551. Specifically, the protrusion 531a fits into the inner wall surface of the side flow passage 57, and the relative position of the protrusion 531a with respect to the opening of the damping flow passage 561 changes, thereby adjusting the opening area of ​​the damping flow passage 561. In the example shown in FIG. 3, a plurality of damping flow passages 561 are formed, but it is sufficient that at least one damping flow passage 561 is formed.

[0037] The hydraulic oil that has passed through the damping flow path 561 flows into a cylindrical oil chamber 50b defined by the housing of the solenoid valve 50, and then flows through the discharge port 58 into the reservoir chamber A4.

[0038] The solenoid valve 50 includes a solenoid mechanism including an electromagnetic coil 511 and a core 521. When current is applied to the electromagnetic coil 511, an electromagnetic force is generated that moves the valve element 531 away from the core 521. The coil 511 and the core 521 are housed in a control chamber 50a that is partitioned from the cylindrical oil chamber 50b in which the valve element 531 is disposed.

[0039] It should be noted that a solenoid valve other than a solenoid valve may be used as the solenoid valve that adjusts the damping force of the hydraulic damper 101. For example, a solenoid valve that uses an electromagnetic fluid (magnetic fluid) may be used as the solenoid valve.

[0040] Spring 541 is provided between valve stopper 551 and valve body 531, and exerts a spring force in a direction that widens the gap between valve stopper 551 and valve body 531. Providing spring 541 makes it possible to prevent valve body 531 from colliding with valve stopper 551 when it moves in a direction approaching valve stopper 551.

[0041] The piston 30 is formed with a pressure side flow passage 31 that allows hydraulic oil to flow from the piston side oil chamber A1 to the rod side oil chamber A2, and a pressure side check valve 32 is arranged at the opening of the pressure side flow passage 31 on the vehicle body side.

[0042] The bottom unit 40 is formed with an extension-side flow passage 41 that allows hydraulic oil to flow from the reservoir chamber A4 to the piston-side oil chamber, and an extension-side check valve 42 is disposed at the vehicle-body side opening of the extension-side flow passage 41. An annular protrusion 43 that protrudes toward and comes into contact with the bottom portion 14 of the damper case 13 is formed on the axle-side surface of the bottom unit 40. A bottom flow passage 44 is formed in this annular protrusion 43, and hydraulic oil in the reservoir chamber A4 flows through the bottom flow passage 44 toward the extension-side flow passage 41.

[0043] (Flow of hydraulic oil during compression stroke) When the vehicle 1 receives an impact force from the road surface, the piston rod 20 enters the first cylinder 11 (Fig. 3(a): compression stroke). With this movement, the piston 30 compresses the hydraulic oil in the piston-side oil chamber A1, and the compressed hydraulic oil passes through the compression-side flow path 31, opens the compression-side check valve 32, and flows into the rod-side oil chamber A2.

[0044] On the other hand, as the piston rod 20 enters the inside of the first cylinder 11, the volume of the first cylinder 11 decreases, and the hydraulic oil in the rod-side oil chamber A2 flows into the annular oil chamber A3 through the shared flow path 17. The hydraulic oil that has flowed into the annular oil chamber A3 flows into the inside of the solenoid valve 50 through the side flow path 57 and passes through the damping flow path 561. Because the opening area of ​​the damping flow path 561 is narrowed by the protrusion 531a of the valve body 531, the hydraulic oil passing through the damping flow path 561 generates a damping force.

[0045] The hydraulic oil that has flowed into the cylindrical oil chamber 50b through the damping flow passage 561 flows through the discharge port 58 into the reservoir chamber A4.

[0046] (Flow of hydraulic oil during extension stroke) During the stroke in which the piston rod 20 retracts from the first cylinder 11 (FIG. 3(b): extension stroke), the piston 30 pushes out the hydraulic oil from the rod-side oil chamber A2 and flows into the annular oil chamber A3 through the shared flow path 17. The hydraulic oil that has flowed into the annular oil chamber A3 passes through the side flow path 57 and the damping flow path 561, similar to the compression stroke, and generates a damping force.

[0047] The hydraulic oil that has flowed into the cylindrical oil chamber 50b through the damping flow passage 561 flows through the discharge port 58 into the reservoir chamber A4.

[0048] As the piston rod 20 moves out of the first cylinder 11, negative pressure is created in the piston-side oil chamber A1. As a result, the hydraulic oil in the reservoir chamber A4 passes through the bottom flow path 44 and the extension-side flow path 41, opens the extension-side check valve 42, and flows into the piston-side oil chamber A1.

[0049] 4 is a cross-sectional view showing the configuration of the solenoid valve 50 according to the embodiment 1. The solenoid valve 50 is provided on the side of the damper case 13. As shown in FIG. 4, the solenoid valve 50 includes a solenoid cylinder 50S, a solenoid mechanism 51, an intake port 52, a valve stopper 53, a valve body 54, a spring 55, and a discharge ring 56.

[0050] The solenoid cylinder 50S is a cylindrical member and is provided so that one opening in the axial direction faces the case opening 13H of the damper case 13. In this embodiment, the solenoid cylinder 50S is provided on the side of the damper case 13, facing in a direction intersecting the axial direction.

[0051] The solenoid mechanism 51 includes a coil 511 , a housing 511 H, a plunger 512 , a magnetic body 513 , and a fixed core 514 .

[0052] Electromagnetic coil 511 is provided along the axial direction of plunger 512 and is held in housing 511H. A conductor (not shown) is connected to coil 511, and a magnetic field is generated when electricity is supplied through the conductor. The supply of electricity to coil 511 is controlled by solenoid control units A to D, which will be described later.

[0053] Plunger 512 is supported by housing 511H via a bearing so as to be axially movable. A magnetic body 513 such as a magnet is fixedly attached to plunger 512. One end of plunger 512 contacts valve body 54.

[0054] The fixed core 514 is disposed closer to the valve element 54 than the magnetic body 513 in the axial direction of the plunger 512. The fixed core 514 is configured to be excited by receiving a magnetic field generated when the coil 511 is energized.

[0055] The suction port 52 is a generally cylindrical member. In this embodiment, the suction port 52 has a one-end opening 5211 and a other-end opening 5212 that has a larger diameter than the one-end opening 5211. The one-end opening 5211 is fitted into the inside of the joint member 12G of the outer cylinder body 121 via a seal member. The other-end opening 5212 faces the solenoid mechanism 51 with the discharge ring 56 sandwiched therebetween.

[0056] The valve stopper 53 is a thick-walled cylindrical member having an annular oil flow path 53r formed therein. The valve stopper 53 is attached to the inside of the opening 5212 on the other end side of the suction port 52.

[0057] The valve element 54 is a cylindrical member having a cylindrical tip 54p that protrudes from the center in the axial direction. The valve element 54 is configured so that the tip 54p faces the valve stopper 53 and fits into the annular flow path 53r. The valve element 54 receives force from the plunger 512 on the side opposite the valve stopper 53 and moves in the axial direction.

[0058] The spring 55 is provided between the valve stopper 53 and the valve body 54. The spring 55 exerts a spring force in a direction that widens the gap between the valve stopper 53 and the valve body 54.

[0059] Discharge ring 56 is a cylindrical member with multiple circular openings in the circumferential direction on its outer circumferential surface. Discharge ring 56 is positioned around valve stopper 53, valve element 54, and spring 55, and discharges oil that has passed through throttle section V (described below) into cylinder inner chamber 50R.

[0060] In the first embodiment, the annular flow path 53r of the valve stopper 53 and the tip 54p of the valve body 54 form an oil throttle section V in the solenoid valve 50. That is, in the solenoid valve 50 of the present embodiment, the throttle section V narrows the oil flow path cross section, thereby generating a damping force. Furthermore, by changing the distance of the valve body 54 from the valve stopper 53 using the plunger 512 of the solenoid mechanism 51, the cross-sectional area of ​​the oil flow path is changed, thereby adjusting the damping force.

[0061] Note that an electromagnetic fluid may be used as the oil in the suspension. A proportional solenoid may be used for the solenoid mechanism 51. A proportional solenoid is a solenoid in which the protruding position of the plunger 512 changes depending on the magnitude of the current supplied to it. If a proportional solenoid is used, the protruding position of the plunger 512 can be freely adjusted, for example, by appropriately changing the duty ratio.

[0062] (Configuration of Suspension ECU 21) Next, the suspension ECU 21 that controls the hydraulic damper 101 will be described.

[0063] The suspension ECU 21 is a damping force control device that controls the damping force of the hydraulic damper 101, and includes an operation value calculation unit 211, an operation frequency calculation unit 212, an oil temperature estimation unit 213, and a control value calculation unit 214, as shown in the functional block diagram of FIG. 5.

[0064] The operation value calculation unit 211 has a function of acquiring vehicle information from the behavior sensor S and calculating the operation amount, operation time, operation speed of the hydraulic damper 101, and the input frequency to the unsprung mass of the vehicle 1.

[0065] The operation value calculation unit 211 calculates the wheel speed sensor S 12 The wheel speed, which is the rotational speed of the wheels 3 and 4 of the vehicle 1, is acquired from the signal, and the actuation amount, actuation time, actuation speed, and input frequency are calculated using a function that uses at least this wheel speed as an input. That is, the unsprung resonance frequency of the vehicle 1 is calculated from the vibration component contained in the wheel speed signal, which is the rotational speed signal of the wheels 3 and 4, and the load fluctuation is calculated from this unsprung resonance frequency. Then, by analyzing this load fluctuation, the actuation amount, actuation time, actuation speed, and input frequency of the hydraulic damper 101 are determined.

[0066] The method for extracting the resonant frequency, which is the peak frequency, from the vibration signal can be performed using digital signal processing such as the FFT (Fast Fourier Transform) method disclosed in Japanese Patent No. 2836652, the LPC (Linear Predictive Coding) method disclosed in Japanese Patent No. 3152151, or the zero cross count method disclosed in Japanese Patent Laid-Open No. 2001-91390.

[0067] As mentioned above, the wheel speed sensor S 12 is not a sensor provided exclusively for calculating the operation value of the hydraulic damper 101, but is a sensor used for controlling the running of the vehicle 1, and is preferable because the operation amount, operation time, operation speed, and input frequency are calculated based on the information obtained from this wheel speed sensor.

[0068] There are no particular limitations on how to calculate the operation amount, operation time, operation speed, and input frequency of the hydraulic damper 101. For example, the operation amount of the hydraulic damper 101 can be calculated by a displacement sensor S 16The operating speed of the hydraulic damper 101 is, for example, the relative displacement value (damper displacement) of the unsprung part with respect to the sprung part connected to the vehicle body, detected by a displacement sensor S 16 The operating time of the hydraulic damper 101 will be described as a value obtained by time-differentiating the damper displacement detected by the longitudinal acceleration sensor S, and the operating time of the hydraulic damper 101 will be described as a value obtained by dividing by the operating speed. The input frequency to the unsprung part of the vehicle 1 is the frequency of a load change acting on the vehicle 1 in the vertical direction or the frequency of a load change acting on the vehicle 1 in the longitudinal and lateral directions, and is detected by the longitudinal acceleration sensor S provided on the spring. 13 Spring vertical acceleration signal or wheel speed sensor S 12 Alternatively, the amplitude of the wheel speed detected by the equation (1) may be calculated.

[0069] The method for extracting the resonant frequency, which is the peak frequency, from the vibration signal can be performed using digital signal processing such as the FFT (Fast Fourier Transform) method disclosed in Japanese Patent No. 2836652, the LPC (Linear Predictive Coding) method disclosed in Japanese Patent No. 3152151, or the zero cross count method disclosed in Japanese Patent Laid-Open No. 2001-91390.

[0070] The operation amount of the hydraulic damper 101, the operation time of the hydraulic damper 101, the operation speed of the hydraulic damper 101, and the input frequency to the unsprung mass of the vehicle 1 calculated by the operation value calculation unit 211 are supplied as state estimation values ​​to an oil temperature estimation unit 213 and a control value calculation unit 214. In addition, the input frequency calculated by the operation value calculation unit 211 is supplied to an operation frequency calculation unit 212.

[0071] The operation frequency calculation unit 212 has a function of calculating the operation frequency of the hydraulic damper 101 from the input frequency output from the operation value calculation unit 211 and outputting the calculated frequency to the oil temperature estimation unit 213. The operation frequency calculation unit 212 can output the operation frequency by, for example, performing random vibration analysis on the input frequency. Details will be described later.

[0072] The oil temperature estimation unit 213 has a function of estimating the oil temperature of the hydraulic damper 101 using at least the estimated state values ​​(actuation amount, actuation time, actuation speed) of the hydraulic damper 101 output from the actuation value calculation unit 211 and the actuation frequency output from the actuation frequency calculation unit 212. The oil temperature estimation unit 213 uses a "damper oil temperature model" when estimating the oil temperature.

[0073] Here, the "damper oil temperature model" is a temperature characteristic map that models an optimal oil temperature by, for example, investigating in advance how much the actual oil temperature measurement value for each operation frequency output from operation frequency calculation unit 212 deviates from the estimated state value (operation amount, operation time, operation speed, input frequency) of hydraulic damper 101 output from operation value calculation unit 211, and setting a coefficient for each actual measurement frequency that can eliminate or reduce this deviation. This temperature characteristic map is stored in advance in a RAM built into suspension ECU 21.

[0074] The oil temperature estimation unit 213 estimates the oil temperature by searching the temperature characteristic map, and supplies the estimated state value (actuation amount, actuation time, actuation speed) of the hydraulic damper 101 calculated by the actuation value calculation unit 211 to the control value calculation unit 214.

[0075] Control value calculation unit 214 has a function of calculating a control value for adjusting the damping force in accordance with at least the oil temperature output from oil temperature estimation unit 213. The correlation between ideal vehicle state values ​​and current values ​​in a plurality of situations obtained in advance by tests or the like is mapped, and control value calculation unit 214 calls up a corresponding value from the map as necessary to perform control.

[0076] 8 is a flowchart showing the operation of embodiment 1. Hereinafter, the operation of the suspension ECU 21 shown in FIG. 5 will be described in detail with reference to the flowchart of FIG.

[0077] (Acquisition of vehicle information) First, the suspension ECU 21 acquires vehicle information detected by the behavior sensor S (step S101).12 The wheel speed, which is the rotation speed of the wheel, is acquired from the wheel speed calculator 211 and supplied to the operation value calculator 211.

[0078] The suspension ECU 21 also uses the damper displacement sensor S 16 The displacement signal is sent from the longitudinal acceleration sensor S 13 The longitudinal acceleration signal is received from the lateral acceleration sensor S 14 Transverse acceleration signal from wheel speed sensor S 12 These signals can also be obtained by applying known mathematical processing to information acquired along a target route by an imaging device or a GPS (Global Positioning System) mounted on the vehicle 1 for navigation or automatic driving, instead of by the behavior sensor S.

[0079] For example, the lateral acceleration signal used for rolling suppression is first calculated based on the vehicle's course direction recognized from images captured in time series by the imaging unit and the travel course (Xt, Yt) which is the current position information of the vehicle 1 updated every time t by a GPS or the like, by calculating the following equation (1): · t,Y · t) is calculated.

[0080]

number

[0081] where X · is the target path change speed in the forward / backward direction [m / s], Y · is the target path change speed in the lateral direction [m / s], dt is the sampling time, X is the target path value in the longitudinal direction [m], Y is the target path value in the lateral direction [m], and dt is the sampling time.

[0082] Next, by calculating the following equation (2), that is, (the target change speed in the longitudinal direction X · t [m / s] / lateral target path change speed Y · t [m / s]) to the inverse tangent (tan -1) to calculate the path angle ψ.

[0083]

number

[0084] And the target route change speed Y · To convert t [m / s] from the absolute coordinate system to the vehicle coordinate system, the following equation (3) is calculated. Here, the target course change velocity is the lateral velocity of the vehicle, which is the value obtained by first differentiating the lateral displacement component of the future course. Note that the absolute coordinate system is a coordinate system fixed to the ground, while the vehicle coordinate system is a Cartesian coordinate system fixed to the road surface.

[0085]

number

[0086] Here, ut denotes the target path change speed [m / s] of vehicle 1 in the longitudinal direction, vt denotes the target path change speed [m / s] of vehicle 1 in the lateral direction, and ψ denotes the path angle [rad] of vehicle 1.

[0087] Next, the lateral acceleration ay is calculated from the target route by calculating the following equation (4): t [m / s 2 ]) where ψ · is the time derivative [rad / s] of the path angle ψ [rad]. In other words, the lateral acceleration ay t [m / s 2 ]) is the lateral acceleration of the vehicle 1, which is the second derivative of the lateral displacement component of the target path.

[0088]

number

[0089] In this way, the lateral acceleration can be obtained by mathematical processing. In this case, the behavior of the vehicle 1 can be obtained without using a sensor, which solves problems such as noise superimposition on the sensor and time delays that occur when using a filter on the sensor output to increase accuracy.

[0090] (Generating State Estimates) The suspension ECU 21 acquires vehicle information from the behavior sensor S or through mathematical processing, and the operation value calculation unit 211 calculates the operation amount, operation time, operation speed, and input frequency to the unsprung mass of the vehicle 1 of the hydraulic damper 101 (step S102).

[0091] That is, the operation value calculation unit 211 calculates the displacement sensor S 16 The actuation amount of the hydraulic damper 101 is calculated from the relative displacement between the sprung and unsprung parts detected by the actuation amount calculation unit 211, the actuation speed is calculated by time-differentiating the actuation amount of the hydraulic damper 201, and the actuation time is calculated by dividing the actuation amount of the hydraulic damper 101 by the actuation speed. 13 The input frequency is calculated based on the spring vertical acceleration signal detected by the wheel speed sensor S12. The operation amount, operation time, operation speed, and input frequency of the hydraulic damper 101 may be calculated by frequency analysis based on the wheel speed, which is the rotational speed of the wheel, detected by the wheel speed sensor S12.

[0092] The operation amount of the hydraulic damper 101, the operation time of the hydraulic damper 101, the operation speed of the hydraulic damper 101, and the input frequency to the unsprung mass of the vehicle 1 calculated by the operation value calculation unit 211 are supplied as state estimation values ​​to an oil temperature estimation unit 213 and a control value calculation unit 214. In addition, the input frequency calculated by the operation value calculation unit 211 is supplied to an operation frequency calculation unit 212.

[0093] (Calculation of operation frequency) The operation frequency calculation unit 212 calculates the operation frequency of the hydraulic damper 101 from the input frequency output from the operation value calculation unit 211 and outputs the calculated frequency to the oil temperature estimation unit 213 (step S103). The operation frequency calculation unit 212 converts the waveform of the input frequency into a power spectral density (PSD) indicating the occurrence frequency for each frequency using a statistical method, treats it as a spectrum value of the load (acceleration), and can output the occurrence probability (operation frequency) of the load using random vibration analysis.

[0094] (oil temperature estimation) The oil temperature estimation unit 213 estimates the oil temperature of the hydraulic damper 101 using at least the estimated state values ​​(actuation amount, actuation time, actuation speed) of the hydraulic damper 101 output from the actuation value calculation unit 211 and the actuation frequency output from the actuation frequency calculation unit 212 (step S104).

[0095] The oil temperature estimation unit 213 uses a damper oil temperature model when estimating the oil temperature. Here, the damper oil temperature model is a model that, for example, examines in advance how much the actual measured value for each operation frequency output from the operation frequency calculation unit 212 deviates from the estimated result of the state estimate value (operation amount, operation time, operation speed) of the hydraulic damper 101 output from the operation value calculation unit 211, and sets a coefficient for each actual measurement frequency that can eliminate or reduce this deviation, thereby modeling the optimal oil temperature. In other words, the damper oil temperature model reflects the operation frequency of the hydraulic damper 101 for oil temperature estimation.

[0096] The oil temperature estimation unit 213 supplies the oil temperature estimated according to the damper oil temperature model to the control value calculation unit 214 together with the estimated state values ​​(actuation amount, actuation time, actuation speed) of the hydraulic damper 101 calculated by the actuation value calculation unit 211.

[0097] (Control value calculation) There is a correlation between oil temperature and the control value (current), and as the oil temperature increases, the damping force decreases. However, if the damping force is increased to compensate for the decreased damping force, the oil temperature will rise further, and there is a concern that the damping force will decrease again. Therefore, in this embodiment, as shown in Figure 6, for example, as the oil temperature increases (T1 > T2), the damping force adjustment coefficient is set to a smaller value (C1 > C2) to control the damping force in a direction that decreases it, thereby suppressing the increase in oil temperature and allowing the oil temperature to decrease quickly. This relationship is stored in advance as a temperature characteristic map in the RAM built into the suspension ECU 21.

[0098] The RAM also stores in advance an Ft-It map used to search for a target current from, for example, the operation speed (damper speed Vp [m / s]), which is one of the estimated state values ​​of the hydraulic damper 101, and the target damping force Ft (N) reflecting the control value calculated by the control value calculation unit 214, as shown in Fig. 7. The target damping force in this Ft-It map reflects the damping force adjustment coefficient C of the temperature characteristic map shown in Fig. 6. Note that the estimated state value is not limited to the damper speed, and may be replaced by, for example, the operation amount (required load) of the hydraulic damper 101.

[0099] 7, the Ft-It map is a map that searches for the target current It from the target damping force Ft and the damper speed Vp, and is appropriately adjusted by multiplying the damper speed or the required load by a gain in PID (Proportional Integral Differential) control so that the target current It increases as the target damping force Ft increases when the damper speed Vp is constant, and the target current It decreases as the damper speed Vp increases when the target damping force Ft is constant. The gain in PID control can be obtained by an appropriate method such as testing.

[0100] The control value calculation unit 214 obtains the target current It as a control command value by searching the Ft-It map shown in Fig. 7, and supplies it to the actuator 217 (step S105). In the Ft-It map shown in Fig. 7, when the target damping force Ft is Ft1 and the damper speed Vp is Vpt, the target current is It5, but when the damper speed Vp increases to Vpt1, the target current decreases to It4, and when the damper speed Vp decreases to Vpt2, the target current increases to It6.

[0101] The actuator 215 controls the damping force of the hydraulic damper 101 by passing a current through the electromagnetic coil 511 (FIG. 3) in accordance with the control command value supplied by the control value calculation unit 214 (step S106). That is, the damping force can be controlled in accordance with the oil temperature estimated in accordance with the operation frequency of the hydraulic damper 101, in addition to the operation amount, operation time, and operation speed of the hydraulic damper 101. The gain in the PID control can be found by an appropriate method such as testing.

[0102] (Effects of the First Embodiment) As explained above, according to the first embodiment, by using the operation frequency of the hydraulic damper 101 to estimate the oil temperature, it is possible to more accurately estimate the oil temperature inside the hydraulic damper 101, and as a result, optimal damping force control becomes possible. Note that the oil temperature is one of the causes of changes in the viscosity of the hydraulic oil, but in the hydraulic damper 101, in the low-frequency range where changes in expansion and contraction are slow (particularly in the sprung resonance frequency of 1 to 2 Hz), a decrease in viscosity due to an increase in oil temperature leads to a longer stroke than necessary. Therefore, by performing the above-mentioned damping force control taking this timing into consideration, it is possible to reduce the calculation load and to expect a greater effect.

[0103] Furthermore, by estimating the state estimation value output by the actuation value calculation unit 211 through calculation without using a sensor, a sensor on which noise is superimposed is not required, and the use of a filter that is required to improve the accuracy of the sensor output is not required, thereby realizing smooth anti-roll control without control delay.

[0104] Dampers, which generate damping force using oil viscosity, are temperature-dependent, and the oil temperature of the damper is constantly changing depending on the environment and driving conditions, making it difficult to maintain ideal behavior. In other words, as the oil temperature of the damper rises, the damping force decreases, and as the oil temperature decreases, the damping force increases. If the damping force decreases, the required amount of damping will be insufficient, causing significant spring height at high inputs and rebound shock noise. On the other hand, if the damping force increases, ride comfort will deteriorate on rough roads and damper slapping noise will be more likely to occur.

[0105] In contrast, in the first embodiment, information related to damper operation (damper operation amount, operation time, operation speed, input frequency) is obtained by calculation and used as a state estimate, and the input frequency is added as a variable to use an oil temperature damper model to obtain the optimal oil temperature, and further, a gain for obtaining the optimal damping force is calculated from a temperature characteristics map that shows the correlation between oil temperature and damping force. As a result, it is possible to obtain effects such as preventing rebound shock noise and reducing the bouncy feeling on the sprung mass at high temperatures, and improving ride comfort on rough roads and reducing or preventing damper slapping noise at low temperatures.

[0106] Note that the term "gain" is used here to refer to the function of converting one value into another. This "conversion" may involve different units before and after the conversion, or may involve adding or removing units.

[0107] [Embodiment 2] Next, a damping force control device that sets the control target to "viscous damping force at an oil temperature of 20°C" and reproduces the viscous damping force at the initial value (oil temperature of 20°C) at each temperature range of outside air temperature or coil temperature will be described below as embodiment 2.

[0108] Fig. 9 is a block diagram showing the functional configuration of a suspension ECU 21 as a damping force control device of embodiment 2. The difference between embodiment 2 shown in Fig. 9 and embodiment 1 shown in Fig. 5 is that in addition to the behavior sensor S, a temperature sensor S is provided that measures the temperature (coil temperature) of the electromagnetic coil 511 (Fig. 3) that measures the outside air temperature or controls the damping force in response to the current. 20Alternatively, an outside air temperature estimating unit (coil temperature estimating unit) 216 is added to the suspension ECU 21. That is, in the second embodiment, the outside air temperature sensor (coil temperature sensor) S 20 If either one of the outside air temperature (coil temperature) estimation unit 216 is provided, the other is not required.

[0109] Another operational difference is that the control value calculation unit 214 has a built-in map containing the control amounts required to reproduce an oil temperature of 20°C in each temperature range of the outside air temperature (coil temperature) detected by the outside air temperature (coil temperature) sensor S20 or the outside air temperature (coil temperature) estimated by the outside air temperature (coil temperature) estimation unit 216, and calculates the control value by searching this map.

[0110] The outside air temperature (coil temperature) estimation unit 216 has a function of estimating the oil temperature by further using the outside air temperature or the coil temperature. The outside air temperature (coil temperature) estimation unit 216 is, for example, 12 The unsprung resonance frequency is extracted from the rotation speed of the wheels 3, 4 detected by the above equation, and the amount of change in the outside air temperature can be calculated based on the amount of change in the unsprung resonance frequency.

[0111] The operation of the second embodiment is shown in a flowchart in Figure 10. The difference from the first embodiment shown in Figure 8 is that an "outside air temperature (coil temperature) estimation process" in step S200 is added between the "oil temperature estimation process" in step S104 and the "target current search process" in step S105. The rest is the same as the first embodiment.

[0112] (Outside temperature estimate) When a vehicle 1 travels on a road, the tires vibrate due to vertical and longitudinal forces caused by the unevenness of the road surface. It is known that this vibration appears near the resonance frequency of the vibration component of the wheel speed extracted from the wheel speed signal.

[0113] The outside temperature (coil temperature) is used to estimate the outside temperature. 12The power spectrum density (PSD), which is the result of frequency analysis of the wheel rotation speed signal, is used to obtain the resonance frequency from this PSD, and the amount of change in outside air temperature is estimated from the temperature characteristic diagram of the resonance frequency (step S200).

[0114] A method of extracting the resonant frequency using the PSD described above and estimating the amount of change in outside air temperature from a temperature characteristic diagram of the resonant frequency is disclosed in Figures 3 to 5, paragraphs

[0053] to

[0057] of Patent No. 3952927.

[0115] (Electromagnetic coil temperature estimation) The temperature of electromagnetic coil 511 may be estimated from the value of the current flowing through electromagnetic coil 511. For example, as shown in Fig. 11, a graph is prepared in advance showing the relationship between the temperature of electromagnetic coil 511 and time for each value of current flowing through electromagnetic coil 511. In the graph of Fig. 11, the vertical axis represents the integrated temperature value (in other words, the temperature of the electromagnetic coil) calculated by integrating the heat generation amount of electromagnetic coil 511, and the vertical axis represents time.

[0116] After a time T has elapsed since current was passed through the electromagnetic coil 511, the temperature of the electromagnetic coil 511 changes depending on the value of the current flowing through the electromagnetic coil 511. The outside air temperature (coil temperature) estimation unit 216 estimates the coil temperature by linearly approximating the heat generation amount of the electromagnetic coil 511 relative to the value of the current flowing through the electromagnetic coil 511. Here, "linearly approximating" means that, within a certain range of current values, when the current value is x and the heat generation amount is y, the heat generation amount is calculated using the relationship y = ax + b. Here, the temperature of the electromagnetic coil 511 can be estimated by approximating the heat generation amount according to the current value detected by the current sensor using a slope a for each of a plurality of current ranges.

[0117] Note that the process (steps S101, S102) in which the operation value calculation unit 211 generates a state estimation value (operation amount, operation time, operation speed, input frequency) of the hydraulic damper 101 based on the output of the behavior sensor S or an estimation of the behavior of the vehicle 1, the process (step S103) in which the operation frequency calculation unit 212 calculates the operation frequency of the hydraulic damper 101 by analyzing the input frequency from the state estimation value, and the process (step S104) in which the oil temperature estimation unit 213 estimates the oil temperature using a damper oil temperature model that reflects the operation frequency of the hydraulic damper 101 are the same as in the first embodiment, and therefore will not be described here to avoid duplication.

[0118] (Calculation of control value) The outside air temperature (coil temperature) estimated by outside air temperature (coil temperature) estimation unit 216 is supplied to control value calculation unit 214. Control value calculation unit 214 searches a map having a control amount required to reproduce an oil temperature of 20°C in each temperature range of the outside air temperature (coil temperature) detected by outside air temperature (coil temperature) sensor S20 or the outside air temperature (coil temperature) estimated by outside air temperature (coil temperature) estimation unit 216, thereby calculating a control command value (current) whose control target is the viscous damping force at an oil temperature of 20°C and supplying the control command value to actuator 215 (step S105).

[0119] The actuator 215 controls the damping force of the hydraulic damper 101 by passing a current through the electromagnetic coil 511 (FIG. 3) in accordance with the control command value supplied by the control value calculation unit 214 (step S106). That is, the damping force can be controlled in accordance with the oil temperature estimated in accordance with the operation frequency of the hydraulic damper 101, in addition to the operation amount, operation time, and operation speed of the hydraulic damper 101 (step S106).

[0120] (Effects of the second embodiment) According to the second embodiment, similar to the first embodiment, the oil temperature in the hydraulic damper 101 can be estimated more accurately by using the operation frequency of the hydraulic damper 101 to estimate the oil temperature, and as a result, optimal damping force control of the hydraulic damper 101 becomes possible. In particular, in order to realize the control target of "viscous damping force at an oil temperature of 20°C", the outside air temperature or the coil temperature sensor S 20By reproducing the viscous damping force at an oil temperature of 20°C in each temperature range of the outside air temperature or electromagnetic coil temperature detected or estimated by the above method, it is possible to achieve a high level of effectiveness in correcting for external disturbances.

[0121] Furthermore, by controlling the damper damping force as described above with the goal of always ensuring a damping force equivalent to 20°C, it is possible to achieve smooth anti-roll control without control delay, as in the first embodiment, and it is also possible to achieve other effects, such as preventing rebound shock noise and reducing the bouncy feeling on the sprung mass at high temperatures, improving ride comfort on rough roads at low temperatures, and reducing or preventing damper hitting noise.

[0122] (Damping force control method) The damping force control method of the present invention is, for example, a damping force control method for controlling the damping force of the dampers 7, 10 provided in the vehicle 1 of Fig. 1. For example, as shown in the flowchart of Fig. 8, the method includes operation value calculation steps (S101, S102) for calculating the operation amount of the dampers 7, 10, the operation time of the dampers 7, 10, the operation speed of the dampers 7, 10, and the input frequency to the unsprung part of the vehicle 1, an operation frequency calculation step (S103) for calculating the operation frequency of the dampers 7, 10 from the input frequency, an oil temperature estimation step (S104) for estimating the oil temperature of the damper from the operation amount, operation time, operation speed, and operation frequency, and a control value calculation step (S105) for calculating a control value for adjusting the damping force in accordance with at least the oil temperature.

[0123] According to the damping force control method of the present invention, by using the operation frequency of the hydraulic damper 101 to estimate the oil temperature, it is possible to more accurately estimate the oil temperature inside the hydraulic damper 101, and as a result, optimal damping force control is possible. Also, by calculating the estimated state values ​​of the hydraulic damper 101 (operation amount, operation time, operation speed, input frequency) by calculation rather than using a sensor, the problem of noise superimposed on the sensor is resolved, and a filter required to improve the accuracy of the sensor output is no longer necessary, thereby eliminating control delays and achieving smooth anti-roll control.

[0124] The present invention is not limited to the above-described exemplary embodiments, and those skilled in the art will be able to easily modify the above-described exemplary embodiments to the extent that they fall within the scope of the claims. [Explanation of symbols]

[0125] 1 Vehicle, 6,9 Spring, 7,10 Damper, S Motion sensor, S 12 Wheel speed sensor, S 13 Vertical acceleration sensor, S 14 Lateral acceleration sensor, S 16 Displacement sensor, S 20 ···Outside air temperature (coil temperature) sensor, 21···Damping force control device (suspension ECU), 101···Hydraulic damper, 211···Operation value calculation unit, 212···Operation frequency calculation unit, 213···Oil temperature estimation unit, 214···Control value calculation unit, 215···Actuator, 216···Outside air temperature (coil temperature) estimation unit, 511···Electromagnetic coil.

Claims

1. A damping force control device that controls the damping force of a damper provided in a vehicle, an operation value calculation unit that calculates an operation amount of the damper, an operation time of the damper, an operation speed of the damper, and an input frequency to an unsprung part of the vehicle; an operation frequency calculation unit that calculates an operation frequency of the damper from the input frequency; an oil temperature estimation unit that estimates an oil temperature of the damper using at least the actuation amount, the actuation time, the actuation speed, and the actuation frequency; a control value calculation unit that calculates a control value for adjusting the damping force in accordance with at least the oil temperature; A damping force control device comprising:

2. The actuation value calculation unit 2. The damping force control device according to claim 1, wherein a wheel speed, which is the rotational speed of a wheel of the vehicle, is acquired, and the actuation amount, actuation time, actuation speed, and input frequency are calculated using a function that uses at least the wheel speed as an input.

3. The vehicle further includes at least one of an outside air temperature sensor that acquires an outside air temperature of the vehicle and an outside air temperature estimation unit that estimates the outside air temperature of the vehicle, The oil temperature estimation unit 3. The damping force control device according to claim 1, wherein the oil temperature is estimated using the outside air temperature.

4. The damping force control device includes: an electromagnetic coil that controls the damping force in response to a current; The electromagnetic coil temperature sensor further includes at least one of a coil temperature sensor that acquires the coil temperature and a coil temperature estimation unit that estimates the coil temperature, The oil temperature estimation unit 3. The damping force control device according to claim 1, wherein the oil temperature is estimated further using the coil temperature.

5. A damping force control method for controlling a damping force of a damper provided in a vehicle, comprising: an operation value calculation step of calculating an operation amount of the damper, an operation time of the damper, an operation speed of the damper, and an input frequency to an unsprung part of the vehicle; an operation frequency calculation step of calculating an operation frequency of the damper from the input frequency; an oil temperature estimating step of estimating an oil temperature of the damper from the actuation amount, the actuation time, the actuation speed, and the actuation frequency; a control value calculation step of calculating a control value for adjusting the damping force in accordance with at least the oil temperature; A damping force control method comprising:

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