阅读说明：本技术 一种压力控制模块及电液伺服制动系统 (Pressure control module and electro-hydraulic servo braking system ) 是由 张�杰 李磊 于 2021-09-16 设计创作，主要内容包括：本发明涉及车辆制动技术领域,尤其涉及一种压力控制模块及电液伺服制动系统。压力控制模块包括电机、丝杠、防转结构、活塞以及缸体,电机包括壳体、定子、转子以及法兰端盖,转子具有中空腔；丝杠设置于中空腔内,并与转子固定连接,丝杠上螺纹连接有丝母；防转结构用于防止丝母转动；活塞套设于丝杠的外周,并与丝母固定连接；缸体设置于法兰端盖上,缸体具有液压腔,活塞能够在液压腔内伸缩。本发明提供的压力控制模块为集成式结构,能够简化压力控制模块与HCU本体装配时的工艺,提高装配效率；还能够在与HCU本体进行装配前对压力控制模块进行密封检测及性能检测,降低装配后的电液制动系统的不良率；另外,能够大大减小整体结构的尺寸。(The invention relates to the technical field of vehicle braking, in particular to a pressure control module and an electro-hydraulic servo braking system. The pressure control module comprises a motor, a screw rod, an anti-rotation structure, a piston and a cylinder body, wherein the motor comprises a shell, a stator, a rotor and a flange end cover, and the rotor is provided with a hollow cavity; the screw rod is arranged in the hollow cavity and fixedly connected with the rotor, and a nut is connected to the screw rod in a threaded manner; the anti-rotation structure is used for preventing the nut from rotating; the piston is sleeved on the periphery of the screw rod and is fixedly connected with the screw nut; the cylinder body is arranged on the flange end cover, the cylinder body is provided with a hydraulic cavity, and the piston can stretch out and draw back in the hydraulic cavity. The pressure control module provided by the invention is of an integrated structure, so that the process of assembling the pressure control module and the HCU body can be simplified, and the assembling efficiency is improved; the pressure control module can be subjected to sealing detection and performance detection before being assembled with the HCU body, so that the reject ratio of the assembled electro-hydraulic brake system is reduced; in addition, the size of the overall structure can be greatly reduced.)

1. A pressure control module, comprising:

the motor (10) comprises a shell (11), a stator (12) and a rotor (13) which are arranged in the shell (11), and a flange end cover (14) which is arranged at one end of the shell (11), wherein the rotor (13) is rotatably connected with the stator (12), and the rotor (13) is provided with a hollow cavity (131);

the screw rod (20) is arranged in the hollow cavity (131) and is fixedly connected with the rotor (13), and a nut (30) is connected to the screw rod (20) in a threaded mode;

the anti-rotation structure is arranged in the hollow cavity (131), is connected with the nut (30) and is used for preventing the nut (30) from rotating so that the nut (30) only axially translates when the lead screw (20) rotates;

the piston (50) is sleeved on the periphery of the lead screw (20) and is fixedly connected with the nut (30);

the cylinder body (60) is arranged on the flange end cover (14), the cylinder body (60) is provided with a hydraulic cavity (64), and the piston (50) can be driven by the nut (30) to stretch and retract in the hydraulic cavity (64).

2. The pressure control module according to claim 1, wherein the rotation preventing structure includes a rotation preventing sleeve (40), the rotation preventing sleeve (40) is fixed in the hollow cavity (131), the rotation preventing sleeve (40) is sleeved on the outer periphery of the nut (30), the inner peripheral surface of the rotation preventing sleeve (40) and the outer peripheral surface of the nut (30) are provided with a first rotation preventing groove (31) extending along the axial direction of the nut, the other one is provided with a first rotation preventing protrusion (41) extending along the axial direction of the nut, and the first rotation preventing protrusion (41) is in sliding fit with the first rotation preventing groove (31).

3. The pressure control module according to claim 2, wherein the rotation prevention sleeve (40) is riveted to the flange end cover (14), the inner ring of the flange end cover (14) has a first riveting surface (141), the outer circumferential surface of the rotation prevention sleeve (40) has a second riveting surface (42), and the first riveting surface (141) and the second riveting surface (42) are riveted.

4. The pressure control module according to claim 3, characterized in that the inner ring of the flange end cover (14) further has a clinching guide surface (142), the clinching guide surface (142) being used to guide the second clinching surface (42) into the first clinching surface (141).

5. Pressure control module according to claim 3, characterized in that the second riveting surface (42) is provided with a knurling (421).

6. The pressure control module of claim 2, wherein the anti-rotation sleeve (40) is of unitary construction with the flange end cap (14).

7. The pressure control module according to any one of claims 1 to 6, characterized in that the outer peripheral surface of the flange end cover (14) and the inner peripheral surface of the housing (11) are provided with a second anti-rotation groove (111) on one and a second anti-rotation projection (143) on the other, the second anti-rotation projection (143) matching the second anti-rotation groove (111).

8. The pressure control module according to any of claims 1-6, wherein the hollow cavity (131) comprises a first cavity portion and a second cavity portion, the first cavity portion having a diameter larger than the second cavity portion; the lead screw (20) comprises a light shaft section (22) and a threaded section (21) which are connected, the screw nut (30) is in threaded connection with the threaded section (21), the threaded section (21) and the screw nut (30) are located in the first cavity portion, the light shaft section (22) is located in the second cavity portion, and the light shaft section (22) is fixedly connected with the rotor (13).

9. The pressure control module according to claim 8, further comprising a first cushion collar (81), the first cushion collar (81) being disposed on a connection face of the first chamber portion and the second chamber portion, the first cushion collar (81) being configured to cushion a return stroke of the nut (30).

10. The pressure control module according to any one of claims 1-6, further comprising a second buffer collar (82), the second buffer collar (82) being disposed in an inner race of the flange end cover (14), the second buffer collar (82) being configured to buffer the progress of the nut (30).

11. The pressure control module according to any one of claims 1-6, wherein the cylinder body (60) has a first sealing ring groove (62) formed on an inner wall thereof, a first sealing ring (91) is disposed in the first sealing ring groove (62), a second sealing ring groove (63) is formed on an outer wall of the cylinder body (60), and a second sealing ring (92) is disposed in the second sealing ring groove (63).

12. An electro-hydraulic servo brake system, comprising a pressure control module according to any of claims 1-11.

Technical Field

The invention relates to the technical field of vehicle braking, in particular to a pressure control module and an electro-hydraulic servo braking system.

Background

Along with the continuous development of automobile electromotion and intellectualization, the development requirements of an electromechanical liquid servo brake system are more and more, wherein a pressure control module is a core component of the whole system.

The pressure control module that prior art provided, mostly drive the lead screw rotation through planetary gear reduction mechanism by the motor, the rotation of lead screw turns into the translation of screw again, and screw and piston formula structure as an organic whole finally drive the piston and advance or retreat in order to realize pressure boost and decompression. Firstly, the adoption of a planetary gear speed reducing mechanism can cause the reduction of mechanical transmission efficiency, and the torque of a driving motor is required to be increased when the same axial force is obtained at the output end; secondly, the planetary gear speed reducing mechanism has low contact ratio, so that the noise is high when the system works; finally, the planetary gear reduction mechanism is matched with a transmission motor, so that the overall structural size is large.

In the pressure control module provided by the prior art, a part of the pressure control module is directly driven by a motor to rotate, but when the pressure control module is assembled with a hybrid vehicle control unit (HCU body), firstly, components such as a torque coupler and the like are assembled on the HCU body, and then, a motor assembly is assembled on the HCU body.

Therefore, a pressure control module is needed to solve the above technical problems.

Disclosure of Invention

The invention aims to provide a pressure control module and an electro-hydraulic servo brake system, which can simplify the process of assembling the pressure control module and an HCU body and can reduce the size of the whole structure.

In order to achieve the purpose, the invention adopts the following technical scheme:

a pressure control module, comprising:

the motor comprises a shell, a stator and a rotor which are arranged in the shell, and a flange end cover arranged at one end of the shell, wherein the rotor is rotationally connected with the stator and is provided with a hollow cavity;

the screw rod is arranged in the hollow cavity and fixedly connected with the rotor, and a nut is connected to the screw rod in a threaded manner;

the anti-rotation structure is arranged in the hollow cavity, is connected with the nut and is used for preventing the nut from rotating so that the nut only axially translates when the lead screw rotates;

the piston is sleeved on the periphery of the lead screw and is fixedly connected with the nut;

the cylinder body is arranged on the flange end cover and provided with a hydraulic cavity, and the piston can be driven by the nut to stretch in the hydraulic cavity.

As the preferred technical scheme of pressure control module, the rotation prevention structure includes the rotation prevention sleeve, the rotation prevention sleeve is fixed in the hollow cavity, just the rotation prevention sleeve is sleeved on the periphery of the screw, the inner peripheral surface of the rotation prevention sleeve and the outer peripheral surface of the screw are provided with a first rotation prevention groove extending along the self axial direction on one of the rotation prevention sleeve and a first rotation prevention protrusion extending along the self axial direction on the other one of the rotation prevention sleeve and the outer peripheral surface of the screw, and the first rotation prevention protrusion is in sliding fit with the first rotation prevention groove.

As a preferred technical solution of the pressure control module, the rotation prevention sleeve is connected to the flange end cover in a riveting manner, an inner ring of the flange end cover has a first riveting surface, an outer circumferential surface of the rotation prevention sleeve has a second riveting surface, and the first riveting surface is connected to the second riveting surface in a riveting manner.

As a preferred technical solution of the pressure control module, the inner ring of the flange end cover further has a riveting guide surface for guiding the second riveting surface into the first riveting surface.

As a preferable technical scheme of the pressure control module, a knurled structure is arranged on the second riveting surface.

As a preferred technical scheme of the pressure control module, the anti-rotation sleeve and the flange end cover are of an integrally formed structure.

As a preferred technical solution of the pressure control module, one of the outer peripheral surface of the flange end cover and the inner peripheral surface of the housing is provided with a second anti-rotation groove, and the other one of the outer peripheral surface of the flange end cover and the inner peripheral surface of the housing is provided with a second anti-rotation protrusion, and the second anti-rotation protrusion is matched with the second anti-rotation groove.

As a preferable technical solution of the pressure control module, the hollow cavity includes a first cavity portion and a second cavity portion, and a diameter of the first cavity portion is larger than a diameter of the second cavity portion; the lead screw comprises a light shaft section and a thread section which are connected, the nut is in threaded connection with the thread section, the thread section and the nut are located in the first cavity part, the light shaft section is located in the second cavity part, and the light shaft section is fixedly connected with the rotor.

As a preferable mode of the pressure control module, the pressure control module further includes a first buffer ring provided on a connection surface of the first chamber section and the second chamber section, and the first buffer ring is configured to buffer a return stroke of the screw.

As a preferable technical solution of the pressure control module, the pressure control module further includes a second buffer retainer ring, the second buffer retainer ring is disposed in the inner ring of the flange end cover, and the second buffer retainer ring is configured to buffer a process of the nut.

As the preferred technical scheme of pressure control module, first sealed annular has been seted up on the inner wall of cylinder body, be provided with first sealing washer in the first sealed annular, the sealed annular of second has been seted up on the outer wall of cylinder body, be provided with the second sealing washer in the sealed annular of second.

An electro-hydraulic servo brake system comprising a pressure control module as claimed in any preceding claim.

The invention has the beneficial effects that:

according to the pressure control module provided by the embodiment of the invention, the screw rod, the nut, the piston, the anti-rotation structure, the cylinder body and other parts required by pressure building are all integrated on the motor to form an integrated structure, so that on one hand, the process of assembling the pressure control module and the HCU body can be simplified, and the assembling efficiency is improved; on the other hand, the pressure control module can be subjected to sealing detection and performance detection before being assembled with the HCU body, and then the pressure control module is assembled with the HCU body after the test is passed, so that the reject ratio of the assembled electro-hydraulic brake system is reduced; in addition, the screw rod, the screw nut, the anti-rotation structure, the piston and other components are arranged in the hollow cavity of the rotor, so that the size of the whole structure can be greatly reduced.

Drawings

FIG. 1 is an exploded view of a pressure control module according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an assembly structure of a pressure control module according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view of a pressure control module provided by an embodiment of the present invention;

fig. 4 is a schematic structural view of a motor according to an embodiment of the present invention;

FIG. 5 is a schematic structural view of a screw and a nut according to an embodiment of the present invention;

FIG. 6 is a schematic view of an anti-rotation sleeve according to an embodiment of the present invention;

FIG. 7 is a schematic structural view of a flange end cap according to an embodiment of the present invention;

fig. 8 is a schematic structural view of a cylinder block according to an embodiment of the present invention;

fig. 9 is an exploded view schematically showing an electro-hydraulic servo brake system according to an embodiment of the present invention.

In the figure:

100. a pressure control module; 200. an HCU body;

10. a motor; 11. a housing; 111. a second anti-rotation slot; 12. a stator; 13. a rotor; 131. a hollow cavity; 14. a flange end cover; 141. a first riveting surface; 142. riveting the guide surface; 143. a second anti-rotation protrusion; 144. a second threaded hole; 15. blocking the cover; 20. a lead screw; 21. a threaded segment; 22. a light axis segment; 30. a nut; 31. a first anti-rotation slot; 40. a rotation prevention sleeve; 41. a first rotation-preventing projection; 42. a second riveting surface; 421. a knurled structure; 50. a piston; 60. a cylinder body; 61. a screw passing hole; 62. a first seal ring groove; 63. a second seal ring groove; 64. a hydraulic chamber; 71. a first screw; 72. a limiting ring; 73. a second screw; 81. a first buffer retainer ring; 82. a second buffer retainer ring; 91. a first seal ring; 92. and a second seal ring.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings and the embodiment. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some but not all of the elements associated with the present invention are shown in the drawings.

In the description of the embodiments of the present invention, unless otherwise explicitly specified or limited, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. Specific meanings of the above terms in the embodiments of the present invention can be understood in specific cases by those of ordinary skill in the art.

In embodiments of the invention, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may comprise the first and second features being in direct contact, or the first and second features being in contact, not directly, but via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

In the description of the embodiments of the present invention, the terms "upper", "lower", "left", "right", and the like are used in an orientation or positional relationship based on those shown in the drawings only for convenience of description and simplicity of operation, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the embodiments of the present invention. Furthermore, the terms "first" and "second" are used only for descriptive purposes and are not intended to have a special meaning.

The pressure control module that prior art provided, mostly drive the lead screw rotation through planetary gear reduction mechanism by the motor, the rotation of lead screw turns into the translation of screw again, and screw and piston formula structure as an organic whole finally drive the piston and advance or retreat in order to realize pressure boost and decompression. Firstly, the adoption of a planetary gear speed reducing mechanism can cause the reduction of mechanical transmission efficiency, and the torque of a driving motor is required to be increased when the same axial force is obtained at the output end; secondly, the planetary gear speed reducing mechanism has low contact ratio, so that the noise is high when the system works; finally, the planetary gear reduction mechanism is matched with a transmission motor, so that the overall structural size is large.

The pressure control module that prior art provided, some is still rotated by motor direct drive lead screw, but pressure control module when assembling with the HCU body, will assemble parts such as torque coupling ware at first on the HCU body, assemble motor element again on the HCU body, at the in-process of assembling motor element, lead screw pair slot and torque coupling ware alignment difficulty, the assembly process is complicated.

Based on the problems in the prior art, an embodiment of the present invention provides a pressure control module 100, as shown in fig. 1 to 4, the pressure control module 100 includes a motor 10, a screw 20, an anti-rotation structure, a piston 50, and a cylinder 60, wherein the motor 10 includes a housing 11, a stator 12 and a rotor 13 disposed in the housing 11, a flange end cover 14 disposed at one end of the housing 11, and a blanking cover 15 disposed at the other end of the housing 11, the rotor 13 is rotatably connected to the stator 12, and the rotor 13 has a hollow cavity 131; the screw rod 20 is arranged in the hollow cavity 131 and is fixedly connected with the rotor 13, the rotor 13 can drive the screw rod 20 to rotate, and the screw nut 30 is connected to the screw rod 20 in a threaded manner; the rotation preventing structure is arranged in the hollow cavity 131, is connected with the nut 30, and is used for preventing the nut 30 from rotating, so that the nut 30 only axially translates when the screw 20 rotates, and the rotation of the screw 20 can be converted into the translation of the nut 30; the piston 50 is sleeved on the periphery of the screw rod 20 and is fixedly connected with the screw nut 30; the cylinder body 60 is arranged on the flange end cover 14, the cylinder body 60 is provided with a hydraulic cavity 64, brake fluid is arranged in the hydraulic cavity 64, and the piston 50 can be driven by the nut 30 to extend and contract in the hydraulic cavity 64 so as to realize pressurization or depressurization.

According to the pressure control module 100 provided by the embodiment of the invention, the screw 20, the nut 30, the piston 50, the anti-rotation structure, the cylinder 60 and other parts required for pressure building are all integrated on the motor 10 to form an integrated structure, so that on one hand, the process of assembling the pressure control module 100 and the HCU body 200 can be simplified, and the assembling efficiency is improved; on the other hand, the sealing detection and the performance detection can be carried out on the pressure control module 100 before the test is assembled with the HCU body 200, and the test is assembled with the HCU body 200 after the test is passed, so that the reject ratio of the assembled electro-hydraulic braking system is reduced; in addition, the screw 20, the nut 30, the rotation preventing structure, the piston 50, and the like are disposed in the hollow cavity 131 of the rotor 13, so that the size of the overall structure can be greatly reduced.

In the present embodiment, referring to fig. 4 and 5, the hollow cavity 131 of the rotor 13 includes a first cavity portion and a second cavity portion, the diameter of the first cavity portion being larger than the diameter of the second cavity portion; the screw rod 20 comprises an optical axis section 22 and a threaded section 21 which are connected, the screw nut 30 is in threaded connection with the threaded section 21, the threaded section 21 and the screw nut 30 are located in the first cavity portion, the optical axis section 22 is located in the second cavity portion, and the optical axis section 22 is fixedly connected with the rotor 13. Through the structure, the lead screw 20 is convenient to fix and the return stroke of the nut 30 is convenient to limit. Preferably, as shown in fig. 1, the optical axis segment 22 is connected to the rotor 13 by a first screw 71, specifically, a first threaded hole is opened on an end surface of the optical axis segment 22, a threaded portion of the first screw 71 is connected to the first threaded hole, and a head of the first screw 71 abuts against the end surface of the rotor 13. Further preferably, a limit ring 72 is disposed between the head of the first screw 71 and the end surface of the rotor 13, so that the connection between the first screw 71 and the rotor 13 is more reliable.

In this embodiment, the anti-rotation structure includes an anti-rotation sleeve 40, one end of the anti-rotation sleeve 40 is connected to the flange end cover 14, and the anti-rotation sleeve 40 is sleeved on the outer periphery of the nut 30. referring to fig. 5 and 6, an inner peripheral surface of the anti-rotation sleeve 40 and an outer peripheral surface of the nut 30 are provided with a first anti-rotation groove 31 extending along the axial direction thereof, and another is provided with a first anti-rotation protrusion 41 extending along the axial direction thereof, and the first anti-rotation protrusion 41 is in sliding fit with the first anti-rotation groove 31. When the rotor 13 drives the screw rod 20 to rotate, the nut 30 can perform translational motion along the extending direction of the first anti-rotation protrusion 41 and the first anti-rotation groove 31 under the action of the first anti-rotation protrusion 41 and the first anti-rotation groove 31. The structure is simple and reliable. The first anti-rotation protrusions 41 and the first anti-rotation slots 31 can be provided in plural, in this embodiment, the case that the first anti-rotation protrusions 41 and the first anti-rotation slots 31 are provided in three is shown, and in other embodiments, the first anti-rotation protrusions 41 and the first anti-rotation slots 31 can be provided according to specific situations, which is not limited to this embodiment.

In this embodiment, referring to fig. 6 and 7, preferably, one end of the rotation preventing sleeve 40 is connected to the flange cover 14 by riveting, the inner ring of the flange cover 14 has a first riveting surface 141, the outer circumferential surface of the end of the rotation preventing sleeve 40 has a second riveting surface 42, and the first riveting surface 141 and the second riveting surface 42 are connected by riveting. Preferably, the inner ring of the flange cover 14 further has a rivet guide surface 142, and the rivet guide surface 142 is used for guiding the second rivet surface 42 of the rotation preventing sleeve 40 into the first rivet surface 141 of the flange cover 14, so as to further facilitate the rivet connection between the first rivet surface 141 and the second rivet surface 42. In addition, the second riveting surface 42 is preferably provided with a knurling structure 421, so that the riveting connection between the second riveting surface 42 and the first riveting surface 141 is more reliable. Alternatively, in other embodiments, the anti-rotation sleeve 40 and the flange end cover 14 may be formed integrally to simplify the process.

In this embodiment, the flange cover 14 and the housing 11 are connected by riveting. Preferably, referring to fig. 7 in combination with fig. 4, the outer circumferential surface of the flange cover 14 and the inner circumferential surface of the housing 11 are provided with a second anti-rotation groove 111 on one, and a second anti-rotation protrusion 143 on the other, wherein the second anti-rotation protrusion 143 is matched with the second anti-rotation groove 111. The connection between the flange cover 14 and the housing 11 can be more reliable by providing the second anti-rotation protrusions 143 and the second anti-rotation grooves 111.

In the present embodiment, the flange cover 14 is connected to the cylinder 60 by the second screws 73. Specifically, referring to fig. 7 and 8 in combination with fig. 1, a second threaded hole 144 is formed in the flange end cover 14, a screw through hole 61 is formed in the cylinder body 60, and a second screw 73 penetrates through the screw through hole 61 and then is in threaded connection with the second threaded hole 144, so that the flange end cover 14 is fixedly connected with the cylinder body 60. The number of the second screws 73 is plural, and preferably three in this embodiment, but in other embodiments, the number of the second screws 73 may also be more than three, and is not limited to this embodiment.

Referring to fig. 1, the pressure control module 100 according to the embodiment of the present invention further includes a first buffer retainer 81, the first buffer retainer 81 is disposed on a connection surface of the first chamber portion and the second chamber portion, and the first buffer retainer 81 is used to buffer a return stroke of the nut 30. Preferably, a fixing groove is formed on a connecting surface of the first chamber section and the second chamber section, and the first buffer retainer 81 is disposed in the fixing groove. In addition, the pressure control module 100 provided in the embodiment of the present invention further includes a second buffer retainer 82, the second buffer retainer 82 is disposed in the inner ring of the flange end cover 14, and the second buffer retainer 82 is used for buffering the process of the nut 30.

In addition, referring to fig. 8 in combination with fig. 1 to 3, a first sealing ring groove 62 is formed on an inner wall of the cylinder 60, and a first sealing ring 91 is disposed in the first sealing ring groove 62 to form a sealing environment with the piston 50. A second sealing ring groove 63 is formed on the outer wall of the cylinder body 60, and a second sealing ring 92 is arranged in the second sealing ring groove 63, so as to form a sealing environment when the pressure control module 100 is assembled with the HCU assembly. The number of the first sealing rings 91 and the number of the second sealing rings 92 can be plural, and this embodiment shows a case where there are two first sealing rings 91 and three second sealing rings 92, which can be set according to specific situations in other embodiments, and is not limited to this embodiment.

The embodiment of the invention further provides an electro-hydraulic servo braking system, which comprises the pressure control module 100 and the HCU body 200, wherein the shell 11 of the motor 10 in the pressure control module 100 is fixedly connected with the shell of the HCU body 200, and the cylinder 60 in the pressure control module 100 extends into the cavity of the HCU body 200. The structure and the operation principle of the HCU body 200 are prior art and will not be described in detail herein.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.