Method for controlling drive of actuator of active vibration isolation support system

A method for controlling the drive of an actuator of an active vibration isolation support system is provided in which one cycle of the actuator moving a movable member out and back is divided into a plurality of micro time regions, a voltage applied to the actuator is duty-controlled in each micro time region, and the duty ratio in at least the last micro time region is set to 0%. As a result, the current passing through the actuator can be made 0 in the final stage of the out and back movement cycle before the movable member moves back to the original position. This can minimize the current passing when the movable member moves back to its original position at the end of the cycle, thus suppressing the needless generation of heat in a coil of the actuator. Therefore, it is possible to prevent an increase in the electrical resistance of the coil which would otherwise hinder the achievement of a required value of current, and to prevent thermal damage to equipment surrounding the coil.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for controlling the drive of an actuator of an active vibration isolation support system that includes an elastic body receiving a load from a vibrating body, a liquid chamber having a wall of which at least a part is formed from the elastic body, a movable member that moves out and back to change the capacity of the liquid chamber in a cycle, and an actuator that receives supply of current to generate an electromagnetic force for moving the movable member out.

2. Description of the Relevant Art

In order to move the movable member of this type of active vibration isolation support system out and back in response to a vibration frequency of an engine, a voltage is cyclically applied to the actuator. As shown inFIG. 6, the movable member moves out due to an electromagnetic force generated by a coil upon applying a rectangular voltage pulse to the actuator in the first half of one cycle of the out and back movement of the movable member, and the movable member moves back due to the elastic force of a return spring by stopping the application of the voltage to the actuator in the second half of the cycle. Therefore, it is possible to reduce the vibration of the engine by alternately switching on and off the voltage applied to the actuator to make the movable member move out and back.

As shown inFIG. 6, even if a rectangular voltage pulse is cyclically applied to the actuator of the active vibration isolation support system, since the current passing through the actuator changes in a sawtooth waveform with a time lag, the current might not become zero within a period when the voltage to the actuator is switched off. This might cause the generation of heat in the coil of the actuator, thus raising its temperature to increase its electrical resistance, so that a required value of current might not be obtained, and equipment surrounding the coil might be thermally damaged.

SUMMARY OF THE INVENTION

The present invention has been achieved in view of the above-mentioned circumstances, and it is an object of the present invention to minimize the generation of heat in an actuator of an active vibration isolation support system.

In order to achieve this object, in accordance with a first aspect of the present invention, there is provided a method for controlling the drive of an actuator of an active vibration isolation support system that includes an elastic body receiving a load from a vibrating body, a liquid chamber having a wall of which at least a part is formed from the elastic body, a movable member that moves out and back to change the capacity of the liquid chamber in a cycle, and an actuator that receives a supply of current to generate an electromagnetic force for moving the movable member out, the method including the step of controlling the current supplied to the actuator such that the current passing through the actuator becomes zero at least when the movable member has moved back.

In accordance with this arrangement, the current passing through the actuator is controlled to become zero when the reciprocally movable member moves back to its original position after being moved out by the electromagnetic force generated by a current supplied to the actuator. Therefore, the current can be minimized when the actuator is stopped and the movable member moves back, thereby suppressing needless generation of heat in the actuator.

Furthermore, in accordance with a second aspect of the present invention, in addition to the first aspect, there is provided a method for controlling the drive of an actuator of an active vibration isolation support system wherein it further includes the steps of: setting a large number of consecutive micro time regions in the cycle; and carrying out duty control of the voltage that is applied to the actuator in each of the micro time regions.

In accordance with this arrangement, since the voltage applied to the actuator is duty-controlled in each of the large number of consecutive micro time regions set in a cycle of out and back movement of the movable member, the current passing through the actuator when the movable member has moved back can reliably be made zero.

An engine E of an embodiment corresponds to the vibrating body of the present invention, a first elastic body14of the embodiment corresponds to the elastic body of the present invention, and a first liquid chamber24of the embodiment corresponds to the liquid chamber of the present invention.

The above-mentioned object, other objects, characteristics, and advantages of the present invention will become apparent from an explanation of a preferred embodiment that will be described in detail below by reference to the attached drawings.

DETAILED DESCRIPTION OF THE INVENTION

An active vibration isolation support system M shown inFIGS. 1 to 4is provided for elastically supporting an engine E on a vehicle body frame F of an automobile. The system is controlled by an electronic control unit U to which are connected an engine rotational speed sensor Sa for detecting the engine rotational speed, a load sensor Sb for detecting the load that is input to the active vibration isolation support system M, an acceleration sensor Sc for detecting the acceleration acting on the engine E, and a lift sensor Sd for detecting the amount of lift of a movable member20of an actuator29, which will be described below.

The active vibration isolation support system M has a structure that is substantially symmetrical with respect to an axis L. The system includes an inner tube12that is welded to a plate-shaped mounting bracket11joined to the engine E, and an outer tube13that is disposed coaxially around the inner tube12. The inner tube12and the outer tube13are bonded by vulcanization bonding to the upper end and lower end respectively of a first elastic body14made of a thick rubber. A disc-shaped first orifice-forming member15having an aperture15bin its center, an annular second orifice-forming member16having a U-shaped cross section open at the top, and a third orifice-forming member17similarly having a U-shaped cross section open at the top, are welded into a single unit. The outer peripheries of the first orifice-forming member15and the second orifice-forming member16are superimposed and fixed in a crimping part13aprovided in a lower part of the outer tube13.

The outer periphery of a second elastic body18made of a rubber membrane is fixed by vulcanization bonding to the inner periphery of the third orifice-forming member17. A cap19that is fixed by vulcanization bonding to the inner periphery of the second elastic body18is press-fitted and fixed onto a movable member20that is disposed on the axis L in a vertically movable manner. A ring21is fixed in the crimping part13aof the outer tube13. The outer periphery of a diaphragm22is fixed to the ring21by vulcanization bonding. A cap23is fixed by vulcanization bonding to the inner periphery of the diaphragm22, and press-fitted and fixed onto the movable member20.

A first liquid chamber24within which a liquid is sealed, is defined between the first elastic body14and the second elastic body18. A second liquid chamber25within which a liquid is sealed, is defined between the second elastic body18and the diaphragm22. The first liquid chamber24and the second liquid chamber25communicate with each other via an upper orifice26and a lower orifice27that are formed from the first to third orifice-forming members15,16and17.

The upper orifice26is an annular passage formed between the first orifice-forming member15and the second orifice-forming member16. A through hole15ais formed in the first orifice-forming member15on one side of a partition26aprovided in a part of the upper orifice26. A through hole16ais formed in the second orifice-forming member16on the other side of the partition26a. The upper orifice26is therefore formed along an almost complete circumference from the through hole15aof the first orifice-forming member15to the through hole16aof the second orifice-forming member16(seeFIG. 2).

The lower orifice27is an annular passage formed between the second orifice-forming member16and the third orifice-forming member17. The through hole16ais formed in the second orifice-forming member16on one side of a partition27aprovided in a part of the lower orifice27. A through hole17ais formed in the third orifice-forming member17on the other side of the partition27a. The lower orifice27is therefore formed along an almost complete circumference from the through hole16aof the second orifice-forming member16to the through hole17aof the third orifice-forming member17(seeFIG. 3).

That is, the first liquid chamber24and the second liquid chamber25communicate with each other via the upper orifice26and the lower orifice27that are connected to each other in tandem.

Fixed in the crimping part13aof the outer tube13is an annular mounting bracket28for fixing the active vibration isolation support system M to the vehicle body frame F. Welded to the lower face of the mounting bracket28is an actuator housing30forming an outer shell of the actuator29for driving the movable member20.

A yoke32is fixed to the actuator housing30. An annular coil34wound around a bobbin33is housed in a space surrounded by the actuator housing30and the yoke32. A bottomed-cylinder-shaped bearing36is inserted from below into a tubular part32aof the yoke32, the tubular part32abeing fitted in the inner periphery of the annular coil34, and is positioned by a retaining part36aat the lower end of the bearing36being engaged with the lower end of the yoke32. A disc-shaped armature38that faces the upper face of the coil34is slidably supported on the inner periphery of the actuator housing30, and a step38aformed on the inner periphery of the armature38engages with the upper end of the bearing36. The armature38is forced upward by a dish spring42that is disposed between the armature38and the upper face of the coil34, and is positioned by being engaged with a retaining part30aprovided on the actuator housing30.

A cylindrical slider43is slidably fitted in the inner periphery of the bearing36. A shaft20aextending downward from the movable member20runs loosely through the upper base of the bearing36and is connected to a boss44that is fixed to the interior of the slider43. A coil spring41is positioned between the upper base of the bearing36and the slider43, whereby the bearing36is forced upward by the coil spring41and the slider43is forced downward.

A lift sensor Sd provided beneath the actuator29includes a sensor housing45that is fixed to the lower end of the actuator housing30. A sensor rod47is slidably supported in a guide member46that is fixed to the interior of the sensor housing45, and forced upward by means of a coil spring48which is disposed between the sensor rod47and the base of the sensor housing45, so as to be in contact with the boss44of the slider43. A contact point50that is fixed to the sensor rod47is in contact with a resistor49that is fixed to the interior of the sensor housing45. The electrical resistance between the lower end of the resistor49and the contact point50is input into the electronic control unit U via a connector51. Since the lift of the movable member20is equal to the travel of the contact point50, the lift of the movable member20can be detected based on the electrical resistance.

When the coil34of the actuator29is in a demagnetized state, the coil spring41applies a downward elastic force to the slider43slidably supported in the bearing36, the coil spring48applies an upward elastic force thereto via the sensor rod47and the boss44, so that the slider43comes to rest at a position where the elastic forces of the two coil springs41and48are in balance. When the coil34is energized in the above-mentioned state so as to draw the armature38downward, the step38apushes and slides the bearing36downward thus compressing the coil spring41. As a result, the elastic force of the coil spring41increases to lower the slider43, and the movable member20that is connected to the slider43via the boss44and the shaft20atherefore descends, so that the second elastic body18connected to the movable member20deforms downward to increase the capacity of the first liquid chamber24. Conversely, when the coil34is demagnetized, the movable member20rises, the second elastic body18deforms upward, and the capacity of the first liquid chamber24decreases.

When a low frequency engine shake vibration occurs while the automobile is traveling, a load that is input from the engine E deforms the first elastic body14thus changing the capacity of the first liquid chamber24, so that the liquid travels to-and-fro between the first liquid chamber24and the second liquid chamber25, which are connected to each other via the upper orifice26and the lower orifice27. When the capacity of the first liquid chamber24increases and decreases, the capacity of the second liquid chamber25decreases and increases accordingly, and this change in the capacity of the second liquid chamber25is absorbed by elastic deformation of the diaphragm22. Since the shapes and dimensions of the upper orifice26and the lower orifice27as well as the spring constant of the first elastic body14are set so that a high spring constant and a high attenuation force can be obtained in a region including the above-mentioned frequency of the engine shake vibration, the vibration that is transmitted from the engine E to the vehicle body frame F can be effectively reduced.

In the above-mentioned frequency region of engine shake vibration, the actuator29is maintained in a non-operational state.

When vibration occurs having a frequency higher than that of the above-mentioned engine shake vibration, that is, when idling vibration or muffled sound vibration due to rotation of a crankshaft of the engine E occurs, since the liquid within the upper orifice26and the lower orifice27that provide communication between the first liquid chamber24and the second liquid chamber25becomes stationary and cannot exhibit the vibration isolation function, the actuator29is operated so as to exhibit the vibration isolation function.

The electronic control unit U controls the application of current to the coil34of the actuator29based on signals from the engine rotational speed sensor Sa, the load sensor Sb, the acceleration sensor Sc and the lift sensor Sd. More specifically, when the engine E is biased downward due to the vibration and thus the capacity of the first liquid chamber24decreases to increase the liquid pressure, the armature38is drawn in by energizing the coil34. As a result, the armature38moves downward together with the movable member20while compressing the coil spring41, thus deforming downward the second elastic body18that is connected along its inner periphery to the movable member20. The capacity of the first liquid chamber24thereby increases to suppress the increase in the liquid pressure, so that the active vibration isolation support system M generates an active support force to prevent transmission of the downward load from the engine E to the vehicle body frame F.

Conversely, when the engine E is biased upward due to the vibration and thus the capacity of the first liquid chamber24increases to decrease the liquid pressure, the drawing-in of the armature38is canceled by demagnetizing the coil34. As a result, the armature38moves upward together with the movable member20due to the elastic force of the coil spring41, thus deforming upward the second elastic body18that is connected along its inner periphery to the movable member20. The capacity of the first liquid chamber24thereby decreases to suppress the decrease in the liquid pressure, so that the active vibration isolation support system M generates an active support force to prevent transmission of the upward load from the engine E to the vehicle body frame F.

The electronic control unit U compares the actual lift of the movable member20that has been detected by the lift sensor Sd with a target lift thereof that has been calculated based on outputs from the engine rotational speed sensor Sa, the load sensor Sb, and the acceleration sensor Sc, and the operation of the actuator29is feedback-controlled so that a deviation converges to 0.

As shown inFIG. 5, when the target lift of the actuator29is in a sinusoidal waveform having a fixed period, a large number of consecutive micro time regions are set in the fixed period, and duty control of the voltage that is applied to the actuator29is carried out in each of the micro time regions. In the present embodiment, 12 micro time regions together form one cycle for the lift of the actuator29, and duty control of the voltage that is applied to the actuator29is carried out individually in each of the 12 micro time regions.

More specifically, the duty ratios of the 12 micro time regions are decreased gradually from 100% such that the duty ratios of the last two micro time regions are set at 0%. As a result, the lift of the actuator29can be obtained as a sinusoidal wave form with 12 micro time regions in one cycle. Decreasing the number of consecutive micro time regions whose duty ratios change with a defined pattern from the above number of12, shortens the cycle of the lift. Conversely, increasing the number of consecutive micro time regions, lengthens the cycle of the lift. Furthermore, changing the pattern of the duty ratios of a plurality of micro time regions forming one cycle in various ways, controls the waveform of the lift of the actuator29as desired.

Unlike the conventional example explained by reference toFIG. 6, in the present embodiment, the current becomes zero at the end of one cycle of the lift of the actuator29(that is, one cycle of moving out and back of the movable member20), and thus generation of heat in the coil34of the actuator29can be minimized, thereby preventing the electrical resistance of the coil34from increasing to hinder the achievement of a required value of current, and preventing thermal damage to equipment surrounding the coil34.

In order to make the current zero in the final stage of moving back of the movable member20that is moved out and back by the actuator29, since the current cannot be made zero instantly by setting the duty ratio of the micro time region to 0%, it is necessary to gradually decrease the duty ratios of a plurality of preceding micro time regions toward 0%. That is, in order to make the current zero in the final stage of moving back of the movable member20, it is necessary to totally control the duty ratios of the plurality of micro time regions in conjunction with each other.

An embodiment of the present invention has been described in detail above, but the present invention can be modified in a variety of ways without departing from the spirit and scope of the invention.

The active vibration isolation support system M supporting the engine E of the automobile is illustrated as one example in the embodiment, but the active vibration isolation support system of the present invention can be applied to the support of other vibrating bodies such as a machine tool.