Patent Application
20050001702
The present invention relates to electromechanical valve actuators and a method of assembling electromechanical valve actuators.
As engine technology advances and manufacturers strive to increase engine power, improve fuel economy, decrease emissions, and provide more control over engines, manufacturers are developing electromechanical valve actuators to replace cam shafts for opening and closing engine valves. Electromechanical valve actuators allow selective opening and closing of the valves in response to various engine conditions.
Electromechanical valve actuators generally include two electromagnets formed from a lamination stack and an embedded power coil. A spring loaded armature located between the electromagnets is movable between the electromagnets as the power coils are selectively energized to create a magnetic force to attract the armature. The surface of the electromagnets to which the armature is attracted when the power coil of an electromagnet is energized is generally referred to as a pole face. The armature abuts to the valve so that as the armature moves between pole faces in pole-face-to-pole-face operation, the valve is opened and closed.
In operation, as an electromagnet is energized, the armature is drawn to the pole face of that electromagnet. As the armature plate approaches the pole face, the gap between the pole face and armature plate, generally referred to as the air gap, decreases. As the air gap decreases, the magnetic force acting on the armature exponentially increases, causing the armature to increase in velocity as it approaches the pole face of the energized electromagnet. The increase in velocity increases the force of the impact of the armature against the electromagnet, causing noise vibration and harshness concerns. Due to the impact of the armature plate on a pole face, quiet operation of electromechanical valve actuators may be challenging to achieve.
To reduce noise, vibration, and harshness issues and obtain quiet operation, many manufacturers have attempted to dampen movement of the armature through active energy absorption systems. Most of these energy absorption systems use fluid dampers, such as a piston or shock, supplied with fluid to dampen the impact force of the armature. Under normal engine operating conditions, the armature cycles between electromagnetic pole faces about 700 to 5000 times per minute. These fluid energy absorption systems need to be configured to allow quick resetting of the energy absorption system to absorb the next impact. One problem with fluid energy absorption systems is that it is difficult to provide fluid to the dampers without decreasing the efficiency of the electromagnets. For example, additional holes drilled into the lamination stack of the electromagnets decreases their efficiency, and such a decrease in efficiency requires additional power to be supplied to the electromagnet to properly and consistently attract the armature plate to the pole face. A decrease in efficiency also requires additional power to hold the armature plate to the pole face so that the valve remains open or closed for a desired time period. Any requirement of additional power puts increased demand on today's already overloaded vehicle electrical systems.
Electromechanical valve actuators also operate in high temperatures with very short cycle times. It is difficult to provide lubrication to armature stems without decreasing the magnetic efficiency of the electromagnets. Lubrication is generally required between the armature stem and lining. Separate oil lines may be added to the top and bottom of the electromechanical valve actuators to provide lubrication to each electromagnet lamination stack, but these oil lines add additional manufacturing costs and assembly time, and increase the package size of the electromechanical valve actuator.
Electromechanical valve actuators are traditionally formed by creating a lamination stack from individual laminated plates, machining an armature hole and, if the electromechanical valve includes an energy absorption system, machining damper holes. For proper operation, the armature holes are machined perpendicular to the armature plate and therefore in a linear electromechanical valve actuator, typically perpendicular to the pole face. With the lamination stack assembled and machined, a power coil may be inserted within a coil cavity on the lamination stack. The power coil is held in place by filling voids in the cavity with epoxy. The assembled electromagnets are then secured within c-channels with fasteners. For example, the electromagnet may be bolted to the c-channel, or a bolt may pass through a passage on each side of the electromagnet and couple the electromagnet to each side of the c-channel. Properly positioning the electromagnets within the c-channels during assembly is difficult due to various tolerance stack ups. Properly assembling the c-channels into a complete electromechanical valve actuator with the armature plate between the electromagnets so that the pole faces of linear electromagnets are parallel with the armature plate and so that the stem passages in the armature electromagnet and valve electromagnet are aligned is difficult and time consuming. Any misalignment of the armature stem passage creates excessive wear and friction caused heat.
An electromechanical valve actuator for use with an internal combustion engine. The electromechanical valve is formed by molding electromagnets in electromagnet receivers for easy formation and assembly of the electromechanical valve actuator. The molding material may include lubrication passages and cooling passages to improve the durability of the electromechanical valve actuator. A connector may also be integrally molded out of the molding material.
The electromechanical valve actuator generally comprises an electromagnet receiver, an electromagnet and a molding material coupling the electromagnet to the electromagnet receiver. The electromechanical valve actuator is assembled by placing the electromagnet within the electromagnet receiver and placing the electromagnet receiver with the inserted electromagnet into a die. When inserted into the die, the electromagnet and the electromagnet receiver are substantially separated to define a void therebetween. The die is then closed and the void is filled with a molding material to structurally secure the electromagnet to the electromagnet receiver.
Further scope of applicability of the present invention will become apparent from the following detailed description, claims, and drawings. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.
The present invention will become more fully understood from the detailed description given here below, the appended claims, and the accompanying drawings in which:
A linear electromechanical valve actuator 10, typically mounted on an internal combustion engine (not shown) to open and close the valves (e.g. the intake or exhaust valves), is illustrated in
The electromechanical valve actuator 10 drives an engine valve (not shown) to open or close a valve port on the engine to selectively allow the flow of gases in and out of a cylinder. The electromechanical valve actuator 10 may include an optional energy absorption system 90 to reduce noise, vibration, and harshness issues by reducing or eliminating the force of impact of the armature assembly 20 against the electromagnets 72, 74 during operation. More specifically, the energy absorption system 90 extracts kinetic energy from the armature assembly 20, thereby slowing the armature assembly 20 as it approaches the pole face 70 of the electromagnets 72, 74. The electromechanical valve actuator 10 may further include an energy absorption system 90 as illustrated in
The armature assembly 20 includes an armature plate 24 and an armature stem 22 as illustrated in
The electromagnet assembly 60 includes the valve electromagnet 72 and the armature electromagnet 74, each having a pole face 70. When assembled, the pole faces 70 of the valve and armature electromagnets 72, 74 oppose each other with the armature plate 24 disposed in the gap 18 therebetween. Each of the electromagnets 72, 74 includes a lamination stack 62 and a power coil 82. The lamination stack 62 is generally formed from laminated sheets (not shown) and defines a coil cavity 64 and an armature stem passage 68. The stem passage 68 may be lined with an armature liner 69. The lamination stack 62 may also define optional bumper passages 66 (
The power coils 82 are generally formed as is well known in the art and are connected to a source of electric current (not shown) through the lead wires 84. The lead wires may terminate in end connectors 86 to allow easy assembly and integration of the electromechanical valve actuator 10 to the engine. The electromagnets 72, 74 are selectively energized by a controller (not shown) such as an engine management system. As the power coils 82 are selectively energized, a magnetic field is created in and around the electromagnets 72, 74 to attract the armature plate 24 to the energized electromagnet 72, 74. The shape of the power coils and the lamination stack 62 may be tailored to adjust the size, shape, and configuration of the magnetic field to attract the armature plate 24 with maximum efficiency to the pole face 70 of an energized electromagnet 72, 74. As the controller selectively energizes alternating electromagnets 72, 74, the armature plate 24 cycles between pole faces 70 of the electromagnets 72, 74 to drive the engine valve between open and closed positions. Once in motion, a spring assembly 30, such as the illustrated armature spring (not shown) and valve spring 32, provides the force to move the armature assembly 20, specifically the armature plate 24, from pole-face-to-pole-face with the electromagnets 72, 74 controlling the movement of the armature plate 24. The electromagnets 72, 74 also may secure the armature plate 24 to one of the pole faces 70 temporarily to hold the valve in an open or closed position for a desired length of time.
The valve c-channels 42 and the armature c-channels 44 act as electromagnet receivers and are generally formed as is well known in the art, but include openings to allow die members, such as the illustrated molding pins 130, to locate the electromagnets during the molding process. The c-channels 42, 44 include a base 36 and sides 38. The base 36 generally includes the openings, such as the illustrated pin openings 46 and armature hole 44. The pin openings 46 allow die pins, such as the molding pins 130, illustrated in
The molding material 50 is generally any material that is: capable of securing the electromagnets 72, 74 to the c-channels 42, 44 over the life of the electromechanical valve actuator 10; resistive to oil swelling; non-electrically conductive; thermally conductive; and durable against wear from heat and friction. Low shrinkage of the molding material 50 while curing is also desirable to keep the electromagnets 72, 74 aligned during the curing process. Many two part epoxies formed from a resin and a hardener fit these characteristics. As illustrated in
The molding material 50 may also form end faces 54 of the valve portion 12 and armature portion, as well as part of the pole faces 70 of the electromagnets 72, 74. The end faces 54 may further include an integrally formed connector 56 also formed from the molding material 50. The end faces 54 may be formed in any size, shape or configuration to improve packaging, allow easy transitions between different vehicles and engines, and allow routing of lubrication passages. In the illustrated embodiment, the molding material 50 encapsulates the electromagnets 72, 74. The lead wires 84 are also encapsulated in the molding material 50 for protection. As illustrated in
The electromechanical valve actuator 10 is generally formed by molding the electromagnets 72, 74 within their respective c-blocks 42, 44 to individually form the valve side 12 and armature side 14 and then assembling the sides 12, 14 with the spacer 16 therebetween. More specifically, the valve c-block 42 and armature c-block 44 are formed to fit within mold cavities and receive the electromagnets so that a molding gap 78 is defined between the electromagnets 72, 74 and the c-blocks 42, 44. The molding material 50 is then received in the gap 78 to secure and locate the electromagnets 72, 74 relative to the c-channels 42, 44 and electrically isolate the electromagnets from the c-channels 42, 44 and rest of the electromechanical valve actuator 10.
The die 110 may be formed in a variety of configurations and shapes depending on the ultimate configuration or shape of the electromechanical valve actuator 10, specifically the armature and valve sides 12, 14. As illustrated in
While the die 110 is illustrated in
The method of formation of the valve side 12 or armature side 14 generally includes the steps of forming an electromagnet 72, 74 and c-channel 42, 44, inserting the electromagnet 72, 74 into the c-channel 42, 44 and inserting the combination into a die 110 with molding pins 130 spacing the electromagnet 72, 74 from the c-channel 42, 44 to create a molding gap 78. The die 110 is then closed and a molding material 50 is inserted to fill the voids by any molding process known in the art. When the molding material 50 is cured, die is removed from the molded side 12, 14. The sides 12, 14 are then assembled together with a spacer 16 and armature assembly 20 therebetweeen. The spring assembly 30 is added and the electromechanical valve actuator 10 is assembled to the engine. The method of formation and assembly of the electromechanical valve actuator will now be described in greater detail below.
The components of the electromechanical valve actuator 10, including the lamination stack 62 and power coil 82, are generally formed as is well known in the art and assembled to form an electromagnet 72, 74, before the epoxy is added to secure the power coil 82 within the coil cavity 64 on the lamination stack 62. The c-channels 42, 44 are also formed as is well known in the art, but include the illustrated pin openings 46.
In the illustrated embodiment, the molding pins 130 are placed into the pin openings 46 on the c-channels 42, 44, and the electromagnets 72, 74 are assembled into the respective c-channels 42, 44. The assembled c-channels 42, 44 and electromagnets 72, 74 are placed on the die base 116. If no energy absorption system 90 is desired, the molding pins 130 may be formed as illustrated in
The die base 116 may include interlocking features (not shown) that interlock with the c-channel 42, 44 to properly align the c-channel 42, 44 within the die 110, or that interlock with the molding pins 130, which then locate the c-channel 42, 44 on the die base 116 through the pin openings 46. The electromagnets 72, 74 are then secured to the die base with the molding tube 140 and a molding fastener 142. The molding tube 140 may be formed to the size of the armature passage 68, or sized to the diameter of the opening remaining after a liner 69, illustrated in
With the c-channels 42, 44 and electromagnets 72, 74 secured to the die base and aligned for molding, the die side walls 114 are installed. Although not order specific, the regular die side wall 118 may be arranged first and secured to the die base 116 with the die fasteners 124. The regular die side wall 118 is arranged a distance away from the electromagnets 72, 74, so that the end faces 54 receive the desired thickness of molding material 50 during the molding process. Next the connector side wall 120 is assembled onto the die base 116. The connector side wall 120 generally includes a connector gap 122 and a wire opening 123 as illustrated in
With the die 110 being assembled around the c-blocks 42, 44 and the electromagnets 72, 74, the die 110 is then closed and the molding material 50 is inserted to form the valve side 12 and armature side 14. The molding material 50 generally flows through the die 110 to form the end faces 52, the pole face 70 above the power coils 82, between the lamination stack, and to secure the electromagnet 72, 74 within the c-channel 42, 44 without the use of fasteners.
Lubrication passages 52 may be formed within the molding material 50 during the molding process to allow transfer of lubrication fluid to the armature stem 22, as shown
After the molding material 50 cures, the die 110 is removed from the valve side 12 and armature side 14. The electromechanical valve actuator 10 is then assembled as is well known in the art with the spacer 16 and armature assembly 20 between the sides 12, 14 and attached to the engine.
As shown in
The foregoing discussion discloses and describes an exemplary embodiment of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.
This application claims the benefit of U.S. Provisional Application No. 60/479,169, filed Jun. 17, 2003, the entire disclosure of this application being considered part of the disclosure of this application and hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60479169 | Jun 2003 | US |
