Patent Application
20080149412
The present invention relates to a vehicle steering system, and specifically to a steer-by-wire (SBW) vehicle steering system in which a driver-applied steering movement is converted into an electric information signal under a condition where a steering mechanism (a rotary-to-linear motion converter) and a steering wheel are mechanically uncoupled from each other and then the steering mechanism is operated in response to the electric information signal for steering.
In recent years, there have been proposed and developed various automotive SBW vehicle steering systems in which a steering reaction torque (or a steering reaction force) applied to a steering wheel and a steer angle at steered road wheels can be arbitrarily determined. One such SBW vehicle steering system has been disclosed in Japanese Patent Provisional Publication No. 2004-237785 (hereinafter is referred to as “JP2004-237785”), corresponding to European Patent Application No. EP 1 445 171 A2. FIG. 8 shows the SBW vehicle steering system disclosed in JP2004-237785. As seen in FIG. 8, the SBW vehicle steering system 100 is comprised of a steering wheel 101 operated by the driver, a steering-wheel angle sensor 102, a steered-road-wheel angle converter (in other words, a rotary-to-linear motion converter) 103, a steering motor 103a, a steer-by-wire (SBW) controller 104, an electromagnetic clutch mechanism 105 by which steering wheel 101 and steered-road-wheel angle converter 103 are mechanically coupled to or uncoupled from each other, a battery 110, and a vehicle speed sensor 142. Steering-wheel angle sensor 102 detects a steering movement, that is, an amount of rotation and a rotation direction of steering wheel 101 rotated by the driver, and generates an electric information signal indicative of the steering movement. Vehicle speed sensor 142 tells SBW controller 104 at what speed the vehicle is moving, and generates a vehicle speed sensor signal. SBW controller 104 controls operation of steering motor 103a responsively to at least the electric information signal from steering-wheel angle sensor 102 (exactly, input information from vehicle speed sensor 142 as well as steering-wheel angle sensor 102). Steered-road-wheel angle converter (rotary-to-linear motion converter) 103 includes a rack-and-pinion mechanism via which rotary motion of steering motor 103a is converted into linear motion of a steering linkage mechanically linked to steered road wheels, thereby varying a steered-road-wheel angle (a steer angle at steered road wheels).
FIG. 9 shows the detailed structure of electromagnetic clutch mechanism 105. As seen in FIG. 9, clutch mechanism 105 is comprised of primary and secondary clutch plates 106-107, an electromagnetic clutch solenoid 108, and a spring 109. Primary clutch plate 106 rotates in synchronism with rotation of steering wheel 101. Primary and secondary clutch plates 106-107 are located to oppose each other. Secondary clutch plate 107 is fixedly connected to the input shaft of steered-road-wheel angle converter 103. Spring 109 permanently biases primary clutch plate 106 toward secondary clutch plate 107. With solenoid 108 energized, an attraction force is produced to move primary clutch plate 106 apart from secondary clutch plate 107 against the spring bias of spring 109. Radial clutch grooves 106a and 107a, configured to mesh with each other, are formed in the two confronting surfaces of primary and secondary clutch plates 106-107 opposing each other.
During an SBW operating mode, an electromagnetic coil 108a of solenoid 108 is energized by SBW controller 104. Thus, electromagnetic clutch mechanism 105 is kept at its disengaged state in which steering wheel 101 (serving as an operating member or a steering input section) and steered-road-wheel angle converter 103 (serving as a steering output section) are mechanically uncoupled from each other. When steering wheel 101 is turned by the driver during the SBW operating mode, SBW controller 104 drives steering motor 103a responsively to at least the information signal from steering-wheel angle sensor 102, and then rotary motion of steering motor 103a is motion-converted into linear motion by means of steered-road-wheel angle converter 103 for steering.
Conversely when SBW controller 104 determines that an SBW system failure, such as a failure in steering motor 103a, occurs, electromagnetic coil 108a of solenoid 108 is de-energized by SBW controller 104. Thus, clutch mechanism 105 is shifted to the engaged state in which steering wheel 101 and steered-road-wheel angle converter 103 are directly coupled to each other via the clutch mechanism engaged. During the direct-coupled mode (or the fail-safe mode) executed in the presence of an SBW system failure, SBW controller 104 inhibits the SBW operating mode that the operation of steering motor 103a is controlled responsively to at least the steering-wheel angle sensor signal. Thus, the operating force (steering movement), applied to steering wheel 101 by the driver, is transferred through clutch mechanism 105 directly to steered-road-wheel angle converter 103, and thus input rotation transferred from steering wheel 101 through clutch mechanism 105 to steered-road-wheel angle converter 103 is converted into linear motion by means of steered-road-wheel angle converter 103, for steering.
As discussed above, when a system failure in the SBW vehicle steering system 100 occurs, clutch mechanism 105 can be shifted to its engaged state for switching from the SBW operating mode to the direct-coupled mode, thus ensuring manual steering even in the presence of the SBW system failure.
In the automotive SBW vehicle steering system as disclosed in JP2004-237785, the radial clutch grooves are formed in the two confronting surfaces of the primary and secondary clutch plates opposing each other. The grooved clutch plate structure is suitable to large steering torque transmission. However, suppose that the electromagnetic clutch mechanism is switching to the engaged state under a condition where the primary clutch plate is rotating in synchronization with rotation of the steering wheel while the secondary clutch plate remains stationary and thus there is a relative-rotation difference between the primary and secondary clutch plates. In such a situation (in the presence of the relative-rotation difference between the primary and secondary clutch plates), there is an increased tendency that the radial clutch grooves of the primary and secondary clutch plates cannot be rapidly brought into mesh. That is, in case of the grooved clutch plate structure, it is difficult to switch the electromagnetic clutch mechanism momentarily to the engaged state in the presence of a relative-rotation difference between the primary and secondary clutch plates. Suppose that, in order to switch the electromagnetic clutch mechanism momentarily to the engaged state, the primary and secondary clutch plates do not have any radial clutch grooves. Such an ungrooved clutch plate structure is unsuitable to large steering torque transmission.
It is, therefore, in view of the previously-described disadvantages of the prior art, an object of the invention to provide a vehicle steering system, configured to execute a steer-by-wire (SBW) operating mode for SBW control and a direct-coupled mode during which steering input and output sections are mechanically coupled to each other via a clutch in the presence of an SBW system failure, and to reconcile (i) momentary switching of the clutch to its engaged state as soon as the SBW system failure occurs and (ii) large steering torque transmission via the clutch engaged.
In order to accomplish the aforementioned and other objects of the present invention, a vehicle steering system configured to execute a steer-by-wire (SBW) operating mode for SBW control and to execute a direct-coupled mode for failsafe, comprises a clutch device configured to mechanically couple and uncouple an operating member to and from an input shaft of a steering mechanism, the clutch device comprising a first member fixed to a first end face of two opposing end faces of a clutch input shaft linked to the operating member and a clutch output shaft linked to the input shaft of the steering mechanism, the first member defining a cylindrical inner peripheral wall surface, a second member defining a cylindrical outer peripheral wall surface in rolling contact with the inner peripheral wall surface, a pair of spring-loaded wedges movably mounted in an annular space defined between a hub portion formed integral with the first member and a central circular hole formed in the second member, each of the wedges having a first end and a second end, the first ends of the wedges located to circumferentially oppose each other, and the second ends of the wedges located to be circumferentially spaced apart from each other, a steering-movement transmission member provided on a second end face of the two opposing end faces of the clutch input shaft and the clutch output shaft, and interleaved between the second wedge ends to keep the first wedge ends in close proximity to each other via the steering-movement transmission member, and a lock pin configured to squeeze into and retreat out of a clearance space defined between the two opposing first wedge ends to ensure a lock state in which the clutch device is kept in an engaged state by a wedging action of the wedges jammed between the first and second members and an unlock state in which the clutch device is kept in a disengaged state with the wedges unjammed between the first and second members.
According to another aspect of the invention, a vehicle steering system comprises a sensor provided to detect at least a steering movement of an operating member, a steering mechanism comprising a steering actuator configured to produce a rotary motion whose direction and amount are determined based on the detected steering movement, and a motion converter configured to convert the rotary motion produced by the steering actuator and transferred to an input shaft of the steering mechanism into a linear motion of an output shaft of the steering mechanism for steering road wheels, and a clutch device configured to mechanically couple and uncouple the operating member to and from the input shaft of the steering mechanism, the clutch device comprising a first member fixed to a first end face of two opposing end faces of a clutch input shaft linked to the operating member and a clutch output shaft linked to the input shaft of the steering mechanism, the first member defining an inner peripheral wall surface, a second member defining an outer peripheral wall surface in rolling contact with the inner peripheral wall surface, a circumference of the outer peripheral wall surface having a diameter less than a diameter of a circumference of the inner peripheral wall surface, a pair of wedges movably mounted in an annular space defined between a hub portion formed integral with the first member and a central circular hole formed in the second member, each of the wedges having a first end and a second end, the first ends of the wedges located to circumferentially oppose each other, and the second ends of the wedges located to be circumferentially spaced apart from each other, a spring configured to force the first wedge ends to move apart from each other, a steering-movement transmission member provided on a second end face of the two opposing end faces of the clutch input shaft and the clutch output shaft, and interleaved between the second wedge ends within the annular space to keep the first wedge ends in close proximity to each other via the steering-movement transmission member, and a lock pin configured to move apart from the second end face for squeezing the lock pin between the two opposing first wedge ends and to move toward the second end face for retreating the lock pin out of a clearance space defined between the two opposing first wedge ends, wherein, under an unlock state in which the lock pin retreats out of the clearance space defined between the two opposing first wedge ends, the clutch device is kept in a disengaged state in which the wedges are permitted to freely slide within the annular space without wedging action between the first and second members to prevent steering torque transmission via the steering-movement transmission member and the wedges, and wherein, under a lock state in which the lock pin squeezes between the two opposing first wedge ends, the clutch device is kept in an engaged state in which the first and second members are coupled to each other by a wedging action of the wedges jammed between the first and second members to permit steering torque transmission via the steering-movement transmission member and the wedges.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.
Referring now to the drawings, particularly to
As shown in
When steering wheel 2 is turned by the driver during a steer-by-wire (SBW) operating mode (a normal operating mode), the steering-wheel movement (clockwise or counterclockwise steering movement), in other words, the amount and direction of rotation of steering shaft 2a, is detected by steering angle sensor 3, and then steering angle sensor 3 generates steering angle sensor signal “a”. SBW controller 9 outputs control command signal “A”, determined based on the latest up-to-date information signal “a” from steering angle sensor 3, to the steering actuator of steered-road-wheel angle converter 6. As a result of this, the steering actuator is driven depending on the detected steering movement, and then rotary motion of the steering actuator is transferred to input shaft 6a of steered-road-wheel angle converter 6. The rotary motion transferred to input shaft 6a is converted into linear motion of output rod 6c, that is, a leftward or rightward motion of output rod 6c, and then road wheels 10 are steered by the output-rod linear motion. During the SBW operating mode, on the other hand, the steering torque, applied to steering wheel 2 (i.e., steering shaft 2a), is detected by steering torque sensor 4, and then steering torque sensor 4 generates steering torque sensor signal “b”. SBW controller 9 outputs control command signal “B”, determined based on the latest up-to-date information signal “b” from steering torque sensor 4, to the steering reaction torque actuator of steering reaction force mechanism 5, thereby reproducing a virtual steering reaction torque correlated with the actual vehicle driving state, taken in by the driver through steering wheel 2.
Conversely when SBW controller 9 determines that an SBW system failure and/or a failure in an automotive electrical equipment of the vehicle, such as a failure in the steering actuator or a failure in the steering reaction torque actuator, occurs and thus the SBW operating mode cannot be executed normally, that is, during a failure mode, SBW controller 9 outputs control command signal “C”, corresponding to a solenoid de-energization signal (i.e., a clutch-engagement signal) to the electromagnetic coil of electromagnetic clutch 8, thus switching electromagnetic clutch 8 from a disengaged state to an engaged state. This realizes a direct-coupled mode during which the steering input section (steering wheel 2 and steering shaft 2a) and the steering output section (steered-road-wheel angle converter 6) are directly coupled to each other via the electromagnetic clutch 8 engaged.
Referring now to
As clearly shown in
As discussed above, outer peripheral wall surface 18a is in rolling contact with inner peripheral wall surface 17a and there is a slight offset between the center of the annular outer-peripheral-wall-surface defining member 18 and the center of the disk-shaped inner-peripheral-wall-surface defining member 17. That is, inner-peripheral-wall-surface defining member 17 and outer-peripheral-wall-surface defining member 18 construct an eccentric rolling-element mechanism 33. As clearly shown in
Returning to
The interrelationship between the wedge pair (20, 20) and lock pin 23 is described hereunder. As previously described in reference to the cross section shown in
In the unlock state of lock pin 23 as shown in
In the lock state of lock pin 23 as shown in
Hereinafter described in detail in reference to the longitudinal cross section of
For the purpose of certainly smoothly squeezing lock pin 23 between the two opposing 1st circumferential ends 20a, 20a of wedges 20, 20, as shown in
Hereinafter described in detail is the operation of the vehicle steering system of the embodiment.
During the SBW operating mode (during the normal operating mode), coil 27 of electromagnet 26 is energized so that electromagnet 26 attracts movable core 28 toward a stand-by position. Thus, lock pin 23 and retainer disk 32 as well as core 28 are forced upwards against the spring bias of return spring 25 and then kept at a retreated position. As a result, coupling mechanism 30 is conditioned in the unlock state shown in
As set forth above, during the unlock state, there is no transmission of rotary motion of connecting shaft 13 to output pulley 15. That is, electromagnetic clutch 8 is kept in its disengaged state in which steering wheel 2 and steered-road-wheel angle converter 6 are mechanically uncoupled from each other. Under this condition (i.e., under the clutch disengaged state), when steering wheel 2 is turned by the driver, SBW controller 9 outputs control command signal “A”, determined based on the latest up-to-date information signal “a” from steering angle sensor 3, to the steering actuator of steered-road-wheel angle converter 6. As a result, the steering actuator is driven depending on the detected steering movement, and then rotary motion of the steering actuator is transferred to input shaft 6a of steered-road-wheel angle converter 6. The rotary motion transferred to input shaft 6a is converted into linear motion of output rod 6c, and then road wheels 10 are steered by the output-rod linear motion.
Conversely when SBW controller 9 determines that an SBW system failure and/or a failure in an automotive electrical equipment of the vehicle, such as a failure in the steering actuator or a failure in the steering reaction torque actuator, occurs and thus the SBW operating mode cannot be executed normally, that is, during a failure mode, SBW controller 9 outputs control command signal “C”, corresponding to a solenoid de-energization signal (an OFF signal) to the electromagnetic coil 27 of electromagnetic clutch 8. That is, coil 27 of electromagnet 26 is de-energized and thus there is no attraction force acting on movable core 28. As a result, by the spring bias of return spring 25 acting on retainer disk 32, lock pin 23 axially downwardly moves together with disk 32 as well as core 28, and then lock pin 23 has been finally squeezed between the two opposing 1st circumferential ends 20a, 20a of wedges 20, 20 (see
As previously described, even when connecting shaft 13 is rotating, the relative position of the shaft center (in particular, tip portion 23b) of lock pin 23, projected from the bottom end of lower axial-end member 13c of connecting shaft 13, with respect to the wedge pair (20, 20) is permanently kept or positioned within the clearance space defined by the recessed guide grooves 22, 22 of 1st circumferential ends 20a, 20a of wedges 20, 20, when viewed in the axial direction of connecting shaft 13 (see
During the direct-coupled mode (during the engaged state of electromagnetic clutch 8), SBW controller 9 inhibits the output of control command signal “A”, determined based on the latest up-to-date information signal “a” from steering angle sensor 3, to the steering actuator of steered-road-wheel angle converter 6. During the direct-coupled mode, steering torque applied to steering wheel 2 by the driver is transferred via electromagnetic clutch 8 directly to input shaft 6a of steered-road-wheel angle converter 6 for steering the road wheels (steered wheels 10) even in the presence of an SBW system failure and/or a failure in an automotive electrical equipment of the vehicle.
As will be appreciated from the above, according to the vehicle steering system of the embodiment, during the SBW operating mode (during the normal operating mode), the steering movement (i.e., the amount and direction of rotation of steering shaft 2a) is detected. The steering actuator of steered-road-wheel angle converter 6 produces a rotary motion whose direction and amount are both determined based on the detected steering movement. Steered-road-wheel angle converter 6 converts the rotary motion produced by the steering actuator and transferred to its input shaft 6a into linear motion of its output rod 6c, for steering road wheels (steered wheels) 10 by the linear motion of output rod 6c. Conversely during a failure mode (in the presence of an SBW system failure and/or a failure in an automotive electrical equipment of the vehicle), the vehicle steering system is configured such that lock pin 23 (included in the clutch device) is squeezed between the two opposing 1st circumferential ends 20a, 20a of wedges 20, 20 by forward movement of lock pin 23. The wedging action of the wedge pair (20, 20) ensures a lock state in which wedges 20, 20 are kept jammed between inner-peripheral-wall-surface defining member 17 and outer-peripheral-wall-surface defining member 18 to integrally couple two members 17-18 with each other with the jammed wedge pair (20, 20), and thus there is no relative rotation between two members 17-18. In the lock state, driving portion 13a drives inner-peripheral-wall-surface defining member 17, and then connecting shaft 13 of the clutch device (i.e., the clutch input shaft of electromagnetic clutch 8) and output pulley 15 (i.e., the clutch output shaft of electromagnetic clutch 8), coupled to each other, rotate together. That is, the wedge pair (20, 20) jammed between two members 17-18 produces the clutch engaged state. In this manner, by virtue of smooth squeezing motion of lock pin 23 between the two opposing 1st circumferential ends 20a, 20a of wedges 20, 20, during a transition from the SBW operating mode to the failure mode, steering shaft 2 and steered-road-wheel angle converter 6 can be mechanically momentarily coupled to each other to ensure manual steering for steered road wheels 10. In other words, during the transition from the SBW operating mode to the failure mode, it is possible to momentarily switch the clutch device (electromagnetic clutch 8) to its engaged state by way of smooth squeezing motion of lock pin 23 between the two opposing 1st circumferential wedge ends 20a, 20a. Additionally, rolling contact between inner-peripheral-wall-surface defining member 17 and outer-peripheral-wall-surface defining member 18, enables large steering torque transmission.
In addition to the above, according to the vehicle steering system of the embodiment, in an electric-power supplied state for coil 27 of electromagnet 26 in which coil 27 is energized during the SBW operating mode, electromagnet 26 attracts lock pin 23 (exactly, armature core 28) toward its stand-by position against the spring bias of return spring 25, and whereby the clutch device (electromagnetic clutch 8) becomes kept at its disengaged state. Conversely in an electric-power unsupplied state for coil 27 of electromagnet 26 in which coil 27 is de-energized during the failure mode, lock pin 23 axially advances and squeezes between the two opposing 1st circumferential ends 20a, 20a of wedges 20, 20, and whereby the clutch device becomes kept at its engaged state. That is, even in the electric-power unsupplied state, the operating mode of the vehicle steering system can be reliably kept at its direct-coupled mode in which steering shaft 2 and steered-road-wheel angle converter 6 are mechanically coupled to each other for ensuring manual steering for steered road wheels 10.
Furthermore, according to the vehicle steering system of the embodiment, the inner peripheral wall surface 17a of inner-peripheral-wall-surface defining member 17 and the outer peripheral wall surface 18a of outer-peripheral-wall-surface defining member 18 are both formed with fine (or close) ridges and troughs, for example by way of knurling. When outer-peripheral-wall-surface defining member 18, whose outer peripheral wall surface 18a is in rolling contact with the inner peripheral wall surface 17a, rolls on the inner peripheral wall surface 17a of inner-peripheral-wall-surface defining member 17, there is a less slippage at the rolling-contact portion and thus the relative velocity of the two contacting surfaces at the point of rolling contact is approximately zero. This is because the coefficient (the ratio) of the frictional force between the inner peripheral wall surface 17a and the outer peripheral wall surface 18a in rolling contact with each other is high due to the fine ridges and troughs formed on the inner and outer peripheral wall surfaces 17a-18a, for example by way of knurling. Therefore, it is possible to effectively suppress an undesired slippage between connecting shaft 13 and output pulley 15 under the clutch engaged state. Alternatively, inner-peripheral-wall-surface defining member 17 may have an internal toothed gear formed on the inner periphery, whereas outer-peripheral-wall-surface defining member 18 may have an external toothed gear formed on the outer periphery and in meshed-engagement with the internal toothed gear of member 17. However, meshed-engagement between the internal and external toothed gears requires high-precision gear shaping, to prevent an undesirably great drag torque from being created when internal and external teeth in mesh are de-meshing from each other. On the contrary, rolling contact between inner-peripheral-wall-surface defining member 17 and outer-peripheral-wall-surface defining member 18 does not require high-precision machining. Thus, rolling contact between two members 17-18 is superior to meshed-engagement between two members 17-18, with respect to reduced manufacturing costs. Additionally, owing to meshing/de-meshing action of the internal and external toothed gears of two members 17-18, requiring high-precision gear shaping, in other words, to avoid an undesirable interference between the addendum circles of the internal and external toothed gears at a circumferential position opposite to the deeply-meshed-engagement portion (i.e., the completely-engaged portion), the eccentricity (the eccentric distance) between the geometric centers of the internal and external toothed gears must be limited to a value greater than the tooth depth. In contrast, the lower limit of the eccentricity (the eccentric distance) between the geometric centers of inner-peripheral-wall-surface defining member 17 and outer-peripheral-wall-surface. defining member 18 in rolling contact (which never requires high-precision machining) can be set to a value less than that of meshed-engagement. Setting the eccentricity (the eccentric distance) between the geometric centers of two members 17-18 to a smaller value enables a smaller angle of wedge 20, (exactly, a smaller angle between inside and outside curved and tapered faces of each wedge 20), in other words, a greater wedge effect, thus enabling large steering torque transmission. Also, setting the eccentricity (the eccentric distance) between the geometric centers of two members 17-18 in rolling contact to a smaller value, in other words, a comparatively wide range of eccentricity settings, means an increased design flexibility.
In the shown embodiment, the side of the clutch output shaft (i.e., output pulley 15 constructing a part of electromagnetic clutch 8) has inner-peripheral-wall-surface defining member 17, which is fixedly connected to the clutch output shaft (output pulley 15). On the other hand, the side of the clutch input shaft (i.e., connecting shaft 13 constructing a part of electromagnetic clutch 8) has lock pin 23 and driving portion 13a. Driving portion 13a is formed in such a manner as to axially extend from the bottom end of the clutch input shaft (connecting shaft 13) and functions, in a broader sense, as a steering-movement transmission member via which driver-applied steering movement (steering torque) can be transmitted from the steering input section to the steering output section with the clutch device engaged (in other words, with the jammed wedges). In the shown embodiment, steering-movement transmission member 13a functions as a driving member, which drives the inner-peripheral-wall-surface defining member via the jammed wedges during the failure mode. In lieu thereof, the clutch device may be configured such that the side of the clutch input shaft (connecting shaft 13) has inner-peripheral-wall-surface defining member 17, whereas the side of the clutch output shaft (output pulley 15) has lock pin 23 and steering-movement transmission member 13a via which driver-applied steering movement (steering torque) can be transmitted from the steering input section to the steering output section with the clutch device engaged. In this case, steering-movement transmission member 13a functions as a driven member, which is driven by the inner-peripheral-wall-surface defining member via the jammed wedges during the failure mode.
In the shown embodiment, when electromagnetic coil 27 is energized, the clutch device (electromagnetic clutch 8) is kept disengaged. Conversely when electromagnetic coil 27 is de-energized, the clutch device is kept engaged. In lieu thereof, the clutch device may be configured such that the clutch device is kept engaged with coil 27 energized, and kept disengaged with coil 27 de-energized.
In the shown embodiment, an electromagnetically-operated clutch (electromagnetic clutch 8) is utilized as a clutch device. It will be appreciated that the invention is not limited to such an electromagnetically-operated clutch, but that another type of clutch, for example a hydraulically-operated clutch or a pneumatically-operated clutch, may be utilized.
In the shown embodiment, a plurality of fine ridges and troughs are formed on both of inner and outer peripheral wall surfaces 17a-18a. Such a plurality of fine ridges and troughs may be formed on either one of inner and outer peripheral wall surfaces 17a-18a in rolling contact.
In the shown embodiment, control command signal “A” for the steering actuator of steered-road-wheel angle converter 6 is determined based on the latest up-to-date information signal “a” from steering angle sensor 3. Alternatively, control command signal “A” for the steering actuator of steered-road-wheel angle converter 6 may be determined based on the latest up-to-date information data signal “V” from the vehicle speed sensor as well as the latest up-to-date information data signal “a” from steering angle sensor 3.
The entire contents of Japanese Patent Application No. 2006-346883 (filed Dec. 25, 2006) are incorporated herein by reference.
While the foregoing is a description of the preferred embodiments carried out the invention, it will be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the scope or spirit of this invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-346883 | Dec 2006 | JP | national |
