Damper control device

A damper control device feeds back a pressure within an extension-side chamber to control an extension-side solenoid valve that adjusts the pressure within the extension-side chamber, and feeds back a pressure within a compression-side chamber to control a compression-side solenoid valve that adjusts the pressure within the compression-side chamber. The damper control device performs a compression-side reduction correction which reduces a compression-side current supplied to the compression-side solenoid valve during extension of a damper, and performs an extension-side reduction correction which reduces an extension-side current supplied to the extension-side solenoid valve during contraction of the damper.

TECHNICAL FIELD

The present invention relates to a damper control device.

BACKGROUND ART

A damper for a vehicle is interposed between a vehicle body and a vehicle wheel of the vehicle and suppresses vibrations of the vehicle body and the vehicle wheel by exerting a damping force when extending/contracting. Among such dampers, there are passive dampers that exert a damping force with preset damping force characteristics (characteristics of the damping force generated by the damper relative to an extension/contraction speed of the damper), as well as dampers that vary the damping force in order to enhance the riding comfort in the vehicle and control the vehicle body posture.

As disclosed in JP6-173996A, dampers that vary the damping force are provided with an extension-side solenoid valve that controls the pressure within an extension-side chamber, and a compression-side solenoid valve that controls the pressure within a compression-side chamber. The opening of the extension-side solenoid valve and the opening of the compression-side solenoid valve are regulated by a damper control device, and the damping force exerted by the damper is controlled by the damper control device.

SUMMARY OF INVENTION

As a method for controlling the damping force of a damper like that disclosed in JP6-173996A, there is a method in which the pressures of the extension-side chamber and the compression-side chamber are detected, and these pressures are fed back to regulate currents supplied to the extension-side solenoid valve and the compression-side solenoid valve, thereby adjusting the pressures of the extension-side chamber and the compression-side chamber to a target pressure.

In this method, an extension-side feedback loop for feeding back the pressure of the extension-side chamber in order to control the extension-side solenoid valve and a compression-side feedback loop for feeding back the pressure of the compression-side chamber in order to control the compression-side solenoid valve are necessary.

The damping force during the extension stroke of the damper is controlled by regulating a current supplied to the extension-side solenoid valve to adjust the pressure of the extension-side chamber. In contrast, in the contraction stroke of the damper, the extension-side solenoid valve does not affect a change in the damping force, but a target pressure during the extension stroke is continuously input into the extension-side feedback loop. Therefore, as shown inFIG. 6, a current command which indicates the magnitude of the current supplied to the extension-side solenoid valve reaches a maximum during the contraction stroke of the damper.

This occurs because a pressure that is decreased due to expansion of the extension-side chamber during the contraction stroke of the damper is input, as the actual pressure of the extension-side chamber into the extension-side feedback loop together with the target pressure during the extension stroke, and thus a deviation between the target pressure and the actual pressure increases. On the other hand, during the extension stroke of the damper, a current command to the compression-side solenoid valve reaches a maximum due to the same phenomenon.

In this way, a current is supplied to the extension-side solenoid valve and the compression-side solenoid valve even while they are not affecting the change in the damping force, and this leads to an increase in power consumption. Further, since a large current is continuously supplied, the amount of heat generated in the solenoid valves increases, and thus it becomes difficult to increase the thrust of the solenoid valves.

The present invention has an object to provide a damper control device that saves power and has solenoid valves capable of generating a larger thrust.

According to one aspect of the present invention, a damper control device for controlling a damping force of a damper having an extension-side chamber and a compression-side chamber which are filled with a working fluid is provided. The damper control device feeds back a pressure within the extension-side chamber to control an extension-side solenoid valve that adjusts the pressure within the extension-side chamber, and feeds back a pressure within the compression-side chamber to control a compression-side solenoid valve that adjusts the pressure within the compression-side chamber. The damper control device performs a compression-side reduction correction which reduces a compression-side current supplied to the compression-side solenoid valve during extension of the damper. The damper control device performs an extension-side reduction correction which reduces an extension-side current supplied to the extension-side solenoid valve during contraction of the damper.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will now be explained below referring to the drawings.

A damper control device1controls a damping force of a damper100interposed between a sprung member110and an unsprung member120of a vehicle. As shown inFIGS. 1 and 2, the damper control device1includes an extension-side pressure sensor2that detects a pressure of an extension-side chamber R1within the damper100; a compression-side pressure sensor3that detects a pressure of a compression-side chamber R2within the damper100; a speed sensor4that detects an extension/contraction speed Vd of the damper100; and a control unit200that controls an extension-side solenoid valve S1and a compression-side solenoid valve S2provided in the damper100on the basis of the pressure detected by the extension-side pressure sensor2, the pressure detected by the compression-side pressure sensor3, and the extension/contraction speed Vd detected by the speed sensor4.

As shown inFIG. 2, the damper100includes the following: a cylinder11; a piston12that is slidably inserted into the cylinder11; a piston rod13that is moveably inserted into the cylinder11and connected to the piston12; the extension-side chamber R1and the compression-side chamber R2that are partitioned by the piston12within the cylinder11and are filled with a working fluid; a reservoir50that pressurizes and stores the working fluid; passages14and15that establish communication between the extension-side chamber R1and the compression-side chamber R2; passages16and17that establish communication between the extension-side chamber R1and the reservoir50; passages18,19, and20that establish communication between the extension-side chamber R2and the reservoir50; an extension-side damping valve21that is provided in the passage14and applies resistance to the flow of working fluid from the extension-side chamber R1toward the compression-side chamber R2; a compression-side auxiliary damping valve22that is provided in the passage15and applies resistance to the flow of working fluid from the compression-side chamber R2toward the extension-side chamber R1; an extension-side check valve23that is provided in the passage16and permits only the flow of working fluid from the reservoir50toward the extension-side chamber R1; the extension-side solenoid valve S1that is provided in the passage17and applies resistance to the flow of working fluid from the extension-side chamber R1toward the reservoir50; a compression-side check valve24that is provided in the passage18and permits only the flow of working fluid from the reservoir50toward the compression-side chamber R2; a compression-side damping valve25that is provided in the passage19and applies resistance to the flow of working fluid from the compression-side chamber R2toward the reservoir50; and the compression-side solenoid valve S2that is provided in the passage20and applies resistance to the flow of working fluid from the compression-side chamber R2toward the reservoir50. For the working fluid, in addition to hydraulic oil, water, an aqueous solution, and a gas can be used.

During the extension stroke of the damper100, the pressure of the extension-side chamber R1that is compressed by the piston12rises, and working fluid moves from the extension-side chamber R1to the compression-side chamber R2via the extension-side damping valve21and is discharged to the reservoir50via the extension-side solenoid valve S1. The volume of the compression-side chamber R2expands due to the movement of the piston12, and working fluid flows into the compression-side chamber R2from the extension-side chamber R1and the compression-side check valve24opens so that insufficient working fluid is supplied into the compression-side chamber R2from the reservoir50. Therefore, the pressure within the compression-side chamber R2becomes a reservoir pressure, and the damper100exerts an extension-side damping force corresponding to the differential pressure between the extension-side chamber R1and the compression-side chamber R2, thereby suppressing the extension of the damper100itself. Therein, by regulating the valve opening pressure of the extension-side solenoid valve S1, the pressure within the extension-side chamber R1can be regulated. Thereby, the extension-side damping force of the damper100can be controlled.

During the contraction stroke of the damper100, the pressure of the compression-side chamber R2that is compressed by the piston12rises, and working fluid moves from the compression-side chamber R2to the extension-side chamber R1via the compression-side auxiliary damping valve22and is discharged to the reservoir50via the compression-side solenoid valve S2and the compression-side damping valve25. The volume of the extension-side chamber R1expands due to the movement of the piston12, and working fluid flows into the extension-side chamber R1from the compression-side chamber R2and the extension-side check valve23opens so that working fluid is supplied into the extension-side chamber R1also from the reservoir50. In this case, the pressure within the extension-side chamber R1becomes a reservoir pressure, and the damper100exerts a compression-side damping force corresponding to the differential pressure between the compression-side chamber R2and the extension-side chamber R1, thereby suppressing the contraction of the damper100itself. Therein, by regulating the valve opening pressure of the compression-side solenoid valve S2, the pressure within the compression-side chamber R2can be regulated. Thereby, the compression-side damping force of the damper100can be controlled.

The extension-side pressure sensor2is provided in the passage17more toward the extension-side chamber R1than the extension-side solenoid valve S1, and detects the pressure within the extension-side chamber R1. The location for installing the extension-side pressure sensor2is not limited to the location mentioned above, and the extension-side pressure sensor2can be directly attached to the cylinder11to detect the pressure within the extension-side chamber R1.

The compression-side pressure sensor3is provided in the passage20more toward the compression-side chamber R2than the compression-side solenoid valve S2, and detects the pressure within the compression-side chamber R2. The location for installing the compression-side pressure sensor3is not limited to the location mentioned above, and the compression-side pressure sensor3can be directly attached to the cylinder11to detect the pressure within the compression-side chamber R2.

The speed sensor4is constituted by a stroke sensor27that detects an extension/contraction displacement of the damper100, and a differentiator28that differentiates the extension/contraction displacement of the damper100detected by the stroke sensor27to calculate an extension/contraction speed Vd of the damper100. The speed sensor4is not limited to the above-described constitution, and can also calculate the extension/contraction speed Vd of the damper100from an acceleration acting on the sprung member no and the unsprung member120. For example, the speed sensor4can also calculate the extension/contraction speed Vd of the damper100by detecting the accelerations in the up-down direction of the sprung member no and the unsprung member120, integrating the detected accelerations to calculate the up-down direction speed of the sprung member no and the up-down direction speed of the unsprung member120, and subtracting the up-down direction speed of the unsprung member120from the up-down direction speed of the sprung member110.

The extension-side solenoid valve S1is an electromagnetic valve device having a valve body (not illustrated) in which pressure of the working fluid from the upstream side acts in a valve opening direction, and a solenoid (not illustrated) that drives the valve body in a valve closing direction. The valve body of the extension-side solenoid valve S1opens when a force in the valve opening direction generated by the pressure of the working fluid exceeds a thrust in the valve closing direction generated by the solenoid, thereby opening the passage17. In other words, the valve opening pressure of the extension-side solenoid valve S1is determined by the magnitude of a current supplied to the solenoid, and the valve opening pressure also increases when the current is increased. In the passage17in which the extension-side solenoid valve S1is provided, a check valve17athat permits only the flow of working fluid from the extension-side chamber R1toward the reservoir50is provided. If the extension-side solenoid valve S1functions as a check valve, the check valve17amay be eliminated.

Similar to the extension-side solenoid valve S1, the compression-side solenoid valve S2is an electromagnetic valve device having a valve body (not illustrated) in which pressure of the working fluid from the upstream side acts in the valve opening direction, and a solenoid (not illustrated) that drives the valve body in the valve closing direction. The valve body of the compression-side solenoid valve S2opens when a force in the valve opening direction generated by the pressure of the working fluid exceeds a thrust in the valve closing direction generated by the solenoid, thereby opening the passage20. In other words, the valve opening pressure of the compression-side solenoid valve S2is determined by the magnitude of a current supplied to the solenoid, and the valve opening pressure also increases when the current is increased. In the passage20in which the compression-side solenoid valve S2is provided, a check valve20athat permits only the flow of working fluid from the compression-side chamber R2toward the reservoir50is provided. If the compression-side solenoid valve S2functions as a check valve, the check valve20amay be eliminated.

The circuit constitution of the damper100is not limited to that described above, and the circuit can have any constitution as long as the pressure of the extension-side chamber R1can be controlled by the extension-side solenoid valve S1and the pressure of the compression-side chamber R2can be controlled by the compression-side solenoid valve S2.

As shown inFIG. 3, the control unit200includes the following: a pressure command calculation unit31that calculates target pressures within the extension-side chamber R1and within the compression-side chamber R2based on a damping force command input from a vehicle control device (not illustrated) that controls the posture of the vehicle; an extension-side deviation calculation unit32that calculates an extension-side deviation εe between a target pressure P1of the extension-side chamber R1calculated by the pressure command calculation unit31and a pressure Pe detected by the extension-side pressure sensor2; an extension-side compensation unit33that calculates an extension-side current command Ie as an extension-side current based on the extension-side deviation εe calculated by the extension-side deviation calculation unit32; a compression-side deviation calculation unit34that calculates a compression-side deviation εc between a target pressure P2of the compression-side chamber R2calculated by the pressure command calculation unit31and a pressure Pc detected by the compression-side pressure sensor3; a compression-side compensation unit35that calculates a compression-side current command Ic as a compression-side current based on the compression-side deviation εc calculated by the compression-side deviation calculation unit34; an extension-side reduction correction unit36that corrects the extension-side current command Ie calculated by the extension-side compensation unit33to calculate a final extension-side final current command Ie*; an extension-side driver37that supplies a current based on the extension-side final current command Ie* to the solenoid of the extension-side solenoid valve S1; a compression-side reduction correction unit38that corrects the compression-side current command Ic calculated by the compression-side compensation unit35to calculate a final compression-side final current command Ic*; and a compression-side driver39that supplies a current based on the compression-side final current command Ic* to the solenoid of the compression-side solenoid valve S2.

The pressure command calculation unit31calculates the target pressures P1and P2within the extension-side chamber R1and within the compression-side chamber R2based on a damping force command input from the vehicle control device (not illustrated). The vehicle control device calculates a damping force to be output by the damper100from, for example, vibration information or the like such as the speed or acceleration of a sprung member of the vehicle. The pressure command calculation unit31outputs the target pressure P1of the extension-side chamber R1calculated based on the damping force command to the extension-side deviation calculation unit32, and outputs the target pressure P2of the compression-side chamber R2to the compression-side deviation calculation unit34.

The extension-side deviation calculation unit32calculates the extension-side deviation εe between the target pressure P1of the extension-side chamber R1calculated by the pressure command calculation unit31and the pressure Pe detected by the extension-side pressure sensor2, and outputs the calculated extension-side deviation εe to the extension-side compensation unit33.

The extension-side compensation unit33calculates the extension-side current command Ie based on the extension-side deviation εe calculated by the extension-side deviation calculation unit32. Specifically, the extension-side compensation unit33calculates the extension-side current command Ie by adding the result obtained by multiplying the extension-side deviation εe by a proportional gain and the result obtained by multiplying a value resulting from integrating the extension-side deviation εe by an integral gain. In other words, the extension-side compensation unit33is a proportional-integral compensator that performs a proportional-integral operation on the extension-side deviation εe. The extension-side compensation unit33can be a proportional-integral-derivative compensator that performs not only a proportional-integral operation but also a derivative operation.

The compression-side deviation calculation unit34calculates the compression-side deviation εc between the target pressure P2of the compression-side chamber R2calculated by the pressure command calculation unit31and the pressure Pc detected by the compression-side pressure sensor3, and outputs the calculated compression-side deviation εc to the compression-side compensation unit35.

The compression-side compensation unit35calculates the compression-side current command Ic based on the compression-side deviation εc calculated by the compression-side deviation calculation unit34. Specifically, the compression-side compensation unit35calculates the compression-side current command Ic by adding the result obtained by multiplying the compression-side deviation εc by a proportional gain and the result obtained by multiplying a value resulting from integrating the compression-side deviation εc by an integral gain. In other words, similar to the extension-side compensation unit33, the compression-side compensation unit35is a proportional-integral compensator that performs a proportional-integral operation on the compression-side deviation εc. The compression-side compensation unit35can be a proportional-integral-derivative compensator that performs not only a proportional-integral operation but also a derivative operation. The proportional gain and the integral gain in the extension-side compensation unit33and the compression-side compensation unit35are set in consideration of the compressibility of the hydraulic oil and the mass of each unit.

The extension-side reduction correction unit36corrects the extension-side current command Ie based on the extension/contraction speed Vd of the damper100input from the speed sensor4. Specifically, the extension-side reduction correction unit36calculates an extension-side reduction amount Me according to the extension/contraction speed Vd of the damper100, and then calculates the extension-side final current command Ie*, which is a final current command, by subtracting the extension-side reduction amount Me from the extension-side current command Ie.

The extension-side reduction amount Me is set to 0 in the case that the extension/contraction speed Vd is a negative value indicating that the damper100is in the extension stroke, and in the case that the extension/contraction speed Vd is a positive value indicating that the damper100is in the contraction stroke and is less than an extension-side speed threshold value αe. On the other hand, in the case that the extension/contraction speed Vd is a positive value and is equal to or greater than the extension-side speed threshold value αe, the extension-side reduction amount Me is calculated by multiplying the absolute value |Vd| of the extension/contraction speed Vd by a gain βe. In other words, in the case that the extension/contraction speed Vd is a positive value and is equal to or greater than the extension-side speed threshold value αe, the extension-side reduction amount Me is calculated by Me=|Vd|·βe, and in all other cases, the extension-side reduction amount Me is set to 0.

The extension-side reduction correction unit36uses the extension-side reduction amount Me obtained as described above to calculate the extension-side final current command Ie*=Ie−Me, and then outputs the extension-side final current command Ie* to the extension-side driver37.

Therefore, the extension-side reduction correction unit36substantially performs a correction to reduce the extension-side current command Ie in the case that the damper100is contracting at a speed that is equal to or greater than the predetermined extension-side speed threshold value αe. In other words, if the damper100is contracting and the absolute value of the extension/contraction speed Vd is equal to or greater than the absolute value of the extension-side speed threshold value αe, a correction for reducing the extension-side current command Ie is performed by the extension-side reduction correction unit36. On the other hand, if the damper100is contracting and the absolute value of the extension/contraction speed Vd is less than the absolute value of the extension-side speed threshold value αe, the reduction correction is not performed.

Basically, when there is a situation in which the pressure within the extension-side chamber R1cannot be controlled to the target pressure P1because the volume of the extension-side chamber R1is expanded, the extension-side reduction correction unit36performs a correction to reduce the extension-side current command Ie. The extension-side reduction correction unit36should perform the correction to reduce the extension-side current command Ie only in the above-described situation. Therefore, rather than always calculating the extension-side reduction amount Me, the extension-side reduction correction unit36can be configured to calculate the extension-side reduction amount Me and correct the extension-side current command Ie only when the reduction correction is necessary.

The extension-side reduction correction unit36can prepare in advance a map for calculating the extension-side reduction amount Me using the extension/contraction speed Vd of the damper100as a parameter, and calculate the extension-side reduction amount Me by map calculation.

The extension-side driver37has a PWM drive circuit and a current loop (not illustrated). The extension-side driver37detects a current flowing to the solenoid of the extension-side solenoid valve S1, feeds back the detected current to the extension-side final current command Ie* that was input, and performs control so that the current flowing to the solenoid becomes the extension-side final current command Ie*.

The compression-side reduction correction unit38corrects the compression-side current command Ic based on the extension/contraction speed Vd of the damper100input from the speed sensor4. Specifically, the compression-side reduction correction unit38calculates a compression-side reduction amount Mc according to the extension/contraction speed Vd of the damper100, and then calculates the compression-side final current command Ic*, which is a final current command, by subtracting the compression-side reduction amount Mc from the compression-side current command Ic.

The compression-side reduction amount Mc is set to 0 in the case that the extension/contraction speed Vd is a positive value indicating that the damper100is in the contraction stroke, and in the case that the extension/contraction speed Vd is a negative value indicating that the damper100is in the extension stroke and is greater than a compression-side speed threshold value αc. On the other hand, in the case that the extension/contraction speed Vd is a negative value and is equal to or less than the compression-side speed threshold value αc, the compression-side reduction amount Mc is calculated by multiplying the absolute value of the extension/contraction speed Vd by a gain βc. In other words, in the case that the extension/contraction speed Vd is a negative value and is equal to or less than the compression-side speed threshold value αc, the compression-side reduction amount Mc is calculated by Mc=|Vd|·βc, and in all other cases, the compression-side reduction amount Mc is set to 0.

The extension-side speed threshold value αe and the compression-side speed threshold value ac can be arbitrarily set, and these values can be set to the same value or different values. The extension-side speed threshold value αe and the compression-side speed threshold value αc are preferably set to a value near 0, for example, an absolute value of 0.5 m/s or less when the vehicle is a two-wheeled vehicle.

The compression-side reduction correction unit38uses the compression-side reduction amount Mc obtained as described above to calculate the compression-side final current command Ic*=Ic−Mc, and then outputs the compression-side final current command Ic* to the compression-side driver39.

Therefore, the compression-side reduction correction unit38substantially performs a correction to reduce the compression-side current command Ic in the case that the damper100is extending at a speed that is equal to or less than the predetermined compression-side speed threshold value αc. In other words, if the damper100is extending and the absolute value of the extension/contraction speed Vd is equal to or greater than the absolute value of the compression-side speed threshold value αc, a correction for reducing the compression-side current command Ic is performed by the compression-side reduction correction unit38. On the other hand, if the damper100is extending and the absolute value of the extension/contraction speed Vd is less than the absolute value of the compression-side speed threshold value αc, the reduction correction is not performed.

Basically, when there is a situation in which the pressure within the compression-side chamber R2cannot be controlled to the target pressure P2because the volume of the compression-side chamber R2is expanded, the compression-side reduction correction unit38performs a correction to reduce the compression-side current command Ic. The compression-side reduction correction unit38should perform the correction to reduce the compression-side current command Ic only in the above-described situation. Therefore, rather than always calculating the compression-side reduction amount Mc, the compression-side reduction correction unit38can be configured to calculate the compression-side reduction amount Mc and correct the compression-side current command Ic only when the reduction correction is necessary.

The compression-side reduction correction unit38can prepare in advance a map for calculating the compression-side reduction amount Mc using the extension/contraction speed Vd of the damper100as a parameter, and calculate the compression-side reduction amount Mc by map calculation.

The compression-side driver39has a PWM drive circuit and a current loop (not illustrated). The compression-side driver39detects a current flowing to the solenoid of the compression-side solenoid valve S2, feeds back the detected current to the compression-side final current command Ic* that was input, and performs control so that the current flowing to the solenoid becomes the compression-side final current command Ic*.

The calculation of the final current commands Ie* and Ic* in the control unit200is executed according to the flowchart shown inFIG. 4. First, the control unit200reads the extension/contraction speed Vd of the damper100and a damping force command input from the vehicle control device (step S1). Next, the control unit200calculates the target pressures P1and P2within the extension-side chamber R1and within the compression-side chamber R2from the damping force command (step S2). Next, the control unit200calculates the deviations εe and εc between the target pressures P1and P2and the pressures Pe and Pc detected by the pressure sensors2and3(step S3). The control unit200then calculates the current commands Ie and Ic from the deviations εe and εc (step S4). Subsequently, the control unit200calculates the reduction amounts Me and Mc from the extension/contraction speed Vd of the damper100(step S5). Next, the control unit200calculates the final current commands Ie* and Ic* by subtracting the reduction amounts Me and Mc from the current commands Ie and Ic (step S6). Finally, the control unit200outputs the final current commands Ie* and Ic* to the drivers37and39that drive the solenoid valves S1and S2(step S7). The control unit200controls the extension-side solenoid valve S1and the compression-side solenoid valve S2by repeatedly executing the above processing procedure.

As explained above, the damper control device1calculates the final current commands Ie* and Ic* based on the pressures Pe and Pc and the extension/contraction speed Vd detected respectively by the extension-side pressure sensor2, the compression-side pressure sensor3, and the speed sensor4, and controls the extension-side solenoid valve S1and the compression-side solenoid valve S2by the final current commands Ie* and Ic*.

As hardware of the damper control device1, the following can be provided: an A/D converter (not illustrated) that takes in signals output by the extension-side pressure sensor2, the compression-side pressure sensor3, and the speed sensor4; a storage device such as a ROM (Read Only Memory) in which programs necessary for executing the above-described control are stored; a computation device such as a CPU (Central Processing Unit) that executes processes based on the programs; and a storage device such as a RAM (Random Access Memory) that provides a storage region to the CPU. The processes in each unit of the control unit200are executed when the CPU executes the programs. The differentiator28of the speed sensor4can be integrated into the control unit200. The vehicle control device and the control unit200can also be integrated.

When the damper100is extending, the extension-side current command Ie becomes the extension-side final current command Ie* without undergoing reduction correction, and a current based on the extension-side final current command Ie* is supplied to the extension-side solenoid valve S1. As a result, the pressure Pe of the extension-side chamber R1is controlled to become the target pressure P1, and the extension-side damping force generated by the damper100can be set to the target damping force. On the other hand, the compression-side final current command Ic* undergoes reduction correction. Thus, as shown inFIG. 5, the current supplied to the compression-side solenoid valve S2, which does not affect the extension-side damping force when the damper100is extending, can be reduced.

When the damper100is contracting, the compression-side current command Ic becomes the compression-side final current command Ic* without undergoing reduction correction, and a current based on the compression-side final current command Ic* is supplied to the compression-side solenoid valve S2. As a result, the pressure Pc of the compression-side chamber R2is controlled to become the target pressure P2, and the compression-side damping force generated by the damper100can be set to the target damping force. On the other hand, the extension-side final current command Ie* undergoes reduction correction. Thus, as shown inFIG. 5, the current supplied to the extension-side solenoid valve S1, which does not affect the compression-side damping force when the damper100is contracting, can be reduced.

In this way, in the damper control device1, the current supplied to the solenoid valve which does not affect the damping force generated by the damper100among the extension-side solenoid valve S1and the compression-side solenoid valve S2can be reduced, and thus the power consumption can be reduced. Further, the currents supplied to the extension-side solenoid valve S1and the compression-side solenoid valve S2can be decreased compared to a conventional damper control device, and thus the amount of heat generated by the solenoids in the extension-side solenoid valve S1and the compression-side solenoid valve S2can be decreased. As a result, the thrust of the extension-side solenoid valve S1and the compression-side solenoid valve S2can be increased. As explained above, according to the damper control device1, the power consumption of the solenoid valves S1and S2can be reduced, and the thrust of the solenoid valves S1and S2can be improved.

The reduction amounts Me and Mc in the reduction correction increase as the extension/contraction speed of the damper100increases, and decrease in the case that the extension/contraction speed Vd of the damper100is slow and switching between extension and contraction is repeated in a short duration of time. Therefore, during switching between extension/contraction of the damper100, the currents supplied to the solenoid valves S1and S2become large, and thus the damping force can be generated with good responsiveness. As a result, good riding comfort of the vehicle can be maintained.

In addition, in the damper control device1, the extension-side reduction correction is not performed when the absolute value |Vd| of the extension/contraction speed is less than the predetermined extension-side speed threshold value αe, and the compression-side reduction correction is not performed when the absolute value |Vd| of the extension/contraction speed is less than the predetermined compression-side speed threshold value αc. Therefore, when the extension/contraction speed Vd of the damper100is low and a switch between extension and contraction is anticipated, the reduction amounts Me and Mc decrease. Thus, during switching between extension/contraction of the damper100, the currents supplied to the solenoid valves S1and S2are maintained high, and therefore the damping force can be generated with good responsiveness. As a result, good riding comfort of the vehicle can be maintained. In this way, good riding comfort of the vehicle can be maintained by providing a dead zone in which extension-side reduction correction and compression-side reduction correction are not performed in accordance with the extension/contraction speed Vd of the damper100.

Next, a case in which the reduction correction is performed based on the extension/contraction state of the damper100will be explained.

Herein, as shown inFIG. 6, if an attempt is made to control the pressure within the extension-side chamber R1to a constant level when the damper100is in the extension stroke, the current supplied to the extension-side solenoid valve S1will increase as the absolute value |Vd| of the extension/contraction speed of the damper100decreases, and the current will decrease as the absolute value |Vd| of the extension/contraction speed increases. When the damper100is in the contraction stroke, if the current command is not reduced, the current supplied to the extension-side solenoid valve S1will be maintained at a maximum level. Further, as shown inFIG. 7, when the damper100is in the contraction stroke, the pressure within the extension-side chamber R1becomes the same as the pressure of the reservoir50regardless of the current that is supplied to the extension-side solenoid valve S1.

In this way, in the damper control device1, when the damper100is in the contraction stroke, the pressure within the extension-side chamber R1is the same as the pressure of the reservoir50. However, the target pressure of the extension-side chamber R1, or in other words the pressure of the extension-side chamber R1that is necessary for generating a predetermined damping force on the extension-side, is larger than the pressure of the reservoir50. Therefore, when the damper100is in the contraction stroke, the extension-side deviation εe, which is the difference between the target pressure of the extension-side chamber R1and the actual pressure within the extension-side chamber R1(the reservoir pressure), increases, and the extension-side current command Ie before performing extension-side reduction correction becomes an extremely large value. Basically, the extension-side current command Ie before performing extension-side reduction correction reaches a value near the maximum value, and if the pressure Pe within the extension-side chamber R1has reached the reservoir pressure, it can be determined that the damper100is in the contraction stroke. Whether or not the extension-side current command Ie has reached a value near the maximum value can be determined by, for example, providing a predetermined first extension-side current threshold value Ieref1and determining whether the extension-side current command Ie is at or above the first extension-side current threshold value Ieref1. Whether or not the pressure Pe within the extension-side chamber R1has reached the reservoir pressure can be determined by, for example, providing a predetermined extension-side pressure threshold value and determining whether the pressure Pe within the extension-side chamber R1is at or below the extension-side pressure threshold value.

Similarly, in the damper control device1, when the damper100is in the extension stroke, the pressure within the compression-side chamber R2is the same as the pressure of the reservoir50. However, the target pressure of the compression-side chamber R2, or in other words the pressure of the compression-side chamber R2that is necessary for generating a predetermined damping force on the compression-side, is larger than the pressure of the reservoir50. Therefore, when the damper100is in the extension stroke, the compression-side deviation εc, which is the difference between the target pressure of the compression-side chamber R2and the actual pressure within the compression-side chamber R2(the reservoir pressure), increases, and the compression-side current command Ic before performing compression-side reduction correction becomes an extremely large value. Basically, the compression-side current command Ic before performing compression-side reduction correction reaches a value near the maximum value, and if the pressure Pc within the compression-side chamber R2has reached the reservoir pressure, it can be determined that the damper100is in the extension stroke. Whether or not the compression-side current command Ic has reached a value near the maximum value can be determined by, for example, providing a predetermined first compression-side current threshold value Icref1and determining whether the compression-side current command Ic is at or above the first compression-side current threshold value Icref1. Whether or not the pressure Pc within the compression-side chamber R2has reached the reservoir pressure can be determined by, for example, providing a predetermined compression-side pressure threshold value and determining whether the pressure Pc within the compression-side chamber R2is at or below the compression-side pressure threshold value.

In this way, in the damper control device1, the extension/contraction state of the damper100can be understood without using the speed sensor4. Therefore, the necessity of the extension-side reduction correction and the compression-side reduction correction can be determined based on the extension/contraction state of the damper100instead of the extension/contraction speed Vd of the damper100.

When it has been determined that the damper100is in the extension stroke, instead of calculating the compression-side reduction amount Mc based on the extension/contraction speed Vd of the damper100to calculate the compression-side final current command Ic*, the compression-side final current command Ic* of the compression-side solenoid valve S2can be set to be equal to the extension-side final current command Ie* of the extension-side solenoid valve S1. Alternatively, the compression-side final current command Ic* can be set to the result of multiplying the extension-side final current command Ie* by a predetermined gain k1. In other words, if the final compression-side final current command Ic* of the compression-side solenoid valve S2is calculated using an equation in which the compression-side final current command Ic*=Ie* or the compression-side final current command Ic*=Ie*·k1, the current supplied to the compression-side solenoid valve S2can be reduced similar to the case in which the compression-side reduction amount Mc is calculated using the extension/contraction speed Vd.

Similarly, when it has been determined that the damper100is in the contraction stroke, instead of calculating the extension-side reduction amount Me based on the extension/contraction speed Vd of the damper100to calculate the extension-side final current command Ie*, the extension-side final current command Ie* of the extension-side solenoid valve S1can be set to be equal to the compression-side final current command Ic* of the compression-side solenoid valve S2. Alternatively, the extension-side final current command Ie* can be set to the result of multiplying the compression-side final current command Ic* by a predetermined gain k2. In other words, if the final extension-side final current command Ie* of the extension-side solenoid valve S1is calculated using an equation in which the extension-side final current command Ie*=Ic* or the extension-side final current command Ie*=Ic*·k2, the current supplied to the extension-side solenoid valve S1can be reduced similar to the case in which the extension-side reduction amount Me is calculated using the extension/contraction speed Vd.

The extension-side final current command Ie* decreases as the damper100switches from the contraction stroke to the extension stroke and the absolute value |Vd| of the extension/contraction speed increases. Therefore, a condition in which the extension-side final current command Ie* is at or below a predetermined second extension-side current threshold value Ieref2can be added as a further condition for performing compression-side reduction correction. In this way, by providing a dead zone in which compression-side reduction correction is not performed, good riding comfort of the vehicle can be maintained. The value of the extension-side final current command Ie* at this time is the same as the value of the extension-side current command Ie, and thus a condition in which the extension-side current command Ie is at or below the second extension-side current threshold value Ieref2can be set as a condition for performing compression-side reduction correction.

Similarly, the compression-side final current command Ic* decreases as the damper100switches from the extension stroke to the contraction stroke and the absolute value |Vd| of the extension/contraction speed increases. Therefore, a condition in which the compression-side final current command Ic* is at or below a predetermined second compression-side current threshold value Icref2can be added as a further condition for performing extension-side reduction correction. In this way, by providing a dead zone in which extension-side reduction correction is not performed, good riding comfort of the vehicle can be maintained. The value of the compression-side final current command Ic* at this time is the same as the value of the compression-side current command Ic, and thus a condition in which the compression-side current command Ic is at or below the second compression-side current threshold value Icref2can be set as a condition for performing extension-side reduction correction.

Next, a case in which reduction correction is performed based on the pressure Pe of the extension-side chamber R1and the pressure Pc of the compression-side chamber R2will be explained.

There are cases in which the extension-side solenoid valve S1and the compression-side solenoid valve S2have override characteristics that a control pressure rises along with an increase in the extension/contraction speed, or in other words an increase in a flow amount. There are also cases in which an overall valve, in which the extension-side damping valve21or the compression-side damping valve25and the compression-side auxiliary damping valve22are included in the extension-side solenoid valve S1and the compression-side solenoid valve S2, has override characteristics that a control pressure rises along with an increase in the extension/contraction speed, or in other words an increase in a flow amount. In such cases, even if an attempt is made to control the pressures within the extension-side chamber R1and the compression-side chamber R2to a constant level, the pressure Pe of the extension-side chamber R1or the pressure Pc of the compression-side chamber R2exhibits a tendency to rise as the absolute value |Vd| of the extension/contraction speed increases as shown inFIG. 7. In other words, it can be determined whether the absolute value |Vd| of the extension/contraction speed is in a large state from a change in the pressure Pe of the extension-side chamber R1and a change in the pressure Pc of the compression-side chamber R2. Therefore, predetermined threshold values can be provided for the pressure Pe of the extension-side chamber R1and the pressure Pc of the compression-side chamber R2, and compression-side reduction correction can be performed when the pressure Pe exceeds the threshold value and extension-side reduction correction can be performed when the pressure Pc exceeds the threshold value. Further, as shown inFIG. 7, the pressure Pe of the extension-side chamber R1and the pressure Pc of the compression-side chamber R2exhibit a correlation with the extension/contraction speed Vd. Therefore, the compression-side reduction amount Mc can be calculated based on a pressure change of the pressure Pe of the extension-side chamber R1when the damper100is in the extension stroke, or based on the extension-side current command Ie which exhibits a change tendency similar to that of the pressure change, without using the output of the speed sensor4. Similarly, the extension-side reduction amount Me can be calculated based on a pressure change of the pressure Pc of the compression-side chamber R2when the damper100is in the contraction stroke, or based on the compression-side current command Ic which exhibits a change tendency similar to that of the pressure change.

There are cases in which the extension-side solenoid valve S1and the compression-side solenoid valve S2are pressure control valves capable of performing pressure control that is proportional to a supplied current without the need to adjust the supplied current or the like. In such a case, the pressure Pe of the extension-side chamber R1and the pressure Pc of the compression-side chamber R2change proportional to the currents supplied to the extension-side solenoid valve S1and the compression-side solenoid valve S2. Therefore, the extension-side pressure sensor2and the compression-side pressure sensor3can be eliminated, and the extension-side solenoid valve S1and the compression-side solenoid valve S2can be controlled based on only the extension/contraction speed Vd detected by the speed sensor4.

The embodiments of the present invention described above are merely illustration of some application examples of the present invention and not of the nature to limit the technical scope of the present invention to the specific constructions of the above embodiments.

The present application claims a priority based on Japanese Patent Application No. 2014-148447 filed with the Japan Patent Office on Jul. 22, 2014, all the contents of which are hereby incorporated by reference.