The disclosure of Japanese Patent Application No. 2005-229605 filed on Aug. 8, 2005 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention generally relates to an electromagnetically driven valve, and more particularly, relates to a pivot-type electromagnetically driven valve that is used for an internal combustion engine and driven by electromagnetic force and elastic force and to a means of driving the same.
2. Description of the Related Art
An electromagnetically driven valve has been disclosed, for example, in the U.S. Pat. No. 6,467,441.
The electromagnetically driven valve has a problem in that its sliding resistance at low temperature is different from that at high temperature, so that its controllability also varies. Moreover, when variable lift control is used to hold a disc out of contact with a core, if coil current fluctuates due to load-induced fluctuations in battery voltage, it is impossible to control the holding of the electromagnetically driven valve in a stable manner.
The invention aims to provide an electromagnetically driven valve that can be driven in a stable manner.
A first aspect of the invention relates to an electromagnetically driven valve that is operated by a combined action of electromagnetic force and elastic force. The electromagnetically driven valve includes a valve element that has a valve stem and moves in reciprocating motion in a direction in which the valve stem extends; an oscillating member that is interlocked with the valve element at an driving end, extending to a pivoting end, from which a central axis extends and the oscillating member oscillates around the central axis; a coil that oscillates the oscillating member; a power supply that supplies electric current to the coil; and a control portion that controls the flow of electric current from the power supply to the coil. During the initial period of operation of the oscillating member, the control portion controls the flow of electric current so that electric current is provided from the power supply to the coil in cycles. Specifically, during the initial period of operation, the control portion controls the number of cycles, the cycle length, and the value of the electric current in accordance with the voltage and temperature.
In an electromagnetically driven valve configured in the above-described manner, a control portion controls the periodic number, the periodic length and the current value in accordance with the voltage and temperature, at the initial drive; therefore it can accelerate heating to improve controllability by applying higher electric current at the low temperature period when sliding resistance is large.
A second aspect of the invention relates to an electromagnetically driven valve that is operated by a combined action of electromagnetic force and elastic force. The electromagnetically driven valve includes a valve element that has a valve stem and moves in reciprocating motion in a direction in which the valve stem extends; an oscillating member that is interlocked with the valve element at a driving end, extending to a pivoting end, from which a central axis extends and the oscillating member oscillates around the central axis; a core of an electromagnet that oscillates the oscillating member; and a permanent magnet that is located on the outer side of the driving end of the oscillating member and is positioned in such a way that a magnetic flux passing through the oscillating member and the core becomes greater.
In the electromagnetically driven valve configured as described above, the magnetic flux passing through the oscillating member and the core becomes greater, thereby reducing electric power consumption and making the valve less subject to the effects of voltage when the valve is held at an intermediate lift position. As a result, an electromagnetically driven valve is provided that improves controllability and ensures stable operation.
According to the invention, an electromagnetically driven valve is provided that ensures stable operation.
The foregoing and further objects, features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:
Embodiments of the invention will be explained below with reference to the drawings. Note that in the embodiments below, identical reference symbols are used to represent identical or equivalent elements, and explanations thereof are not repeated.
(First Embodiment)
A U-shaped housing 51 is a base member, and various elements are installed in the housing 51. The upper electromagnet 60 and the lower electromagnet 160 respectively include cores 61 and 161, which are made of magnetic material, and the coils 62 and 162, which are wound around the cores 61 and 161. The flow of electric current to the coils 62 and 162 generates a magnetic field, which drives the disc 30. The disc 30 is arranged between the upper electromagnet 60 and the lower electromagnet 160, and the disc is attracted to either of them by the attraction force of the upper electromagnet 60 and the lower electromagnet 160. This causes the disc 30 to move in reciprocal motion between the upper electromagnet 60 and the lower electromagnet 160. The reciprocal motion of the disc 30 is transmitted to a stem 46 through a long hole 22 and a pin 21.
The electromagnetically driven valve 1 in the embodiment constitutes one of an intake valve or exhaust valve in an internal combustion engine such as a gasoline engine and diesel engine. The embodiment section describes the case where a valve element serves as an intake valve fitted to an intake port 18, however the invention is applicable to a valve element that serves as an exhaust valve.
The disc 30 includes an arm portion 31 and a bearing portion 38, and the arm portion 31 extends from driving end 32 to pivoting end 33. The arm portion 31 is a member that is attracted by the upper electromagnet 60 and the lower electromagnet 160; so that it oscillates (or pivots) in the direction indicated by the arrow 30a. The bearing portion 38 is set at an end of the arm portion 31, and the arm portion 31 pivots around the bearing portion 38. It is possible for the upper surface of the arm portion 31 to come into contact with the upper electromagnet 60, and it is possible for the lower surface of the arm portion 31 to come into contact with the lower electromagnet 160.
The bearing portion 38 is cylindrical, and a torsion bar 36 is accommodated therein. A first end of the torsion bar 36 is fitted into the housing 51 by means of a spline fitting, while the other end is fitted into the bearing portion 38 of the disk 30. Consequently, when the bearing portion 38 pivots, a force in the opposite direction to the rotation is transmitted from the torsion bar 36 to the bearing portion 38. Thus a reaction force is constantly applied to the bearing portion 38 in a neutral direction. At driving end 32 of the disk 30, the stem 46 is provided in such a way that force is imparted to it from the disc 30, and the stem 46 is guided by a stem guide 45. The stem 46 and the disc 30 can oscillate in the direction indicated by the arrow 30a.
The housing 51 has a projection 52, and pivoting end 33 of the disk 30 is accommodated therein. A bearing 59 is arranged between the bearing portion 38 and the projection 52 of the housing 51.
The intake port 18 is provided in the lower part of the cylinder head 41. The intake port 18 is a passage for the introduction of intake air into a combustion chamber, and either air-fuel mixture or air passes through the intake port 18. A valve seat 42 is provided between the intake port 18 and the combustion chamber, thereby improving the sealability of the valve element 14.
The valve element 14 is installed on the cylinder head 41 as an intake valve. The valve element 14 includes the valve stem 12 extending in the longitudinal direction and a bell portion 13 attached at the end of the valve stem 12. The valve stem 12 is guided by a stem guide 43 and is fitted with a spring retainer 19. The spring retainer 19 is energized in the upward direction by a valve spring 17. Thus both the spring retainer 19 and the valve stem 12 are energized by the valve spring 17.
The ECU 100 controls electric current flowing from the power supply 200 to the coils 62 and 162. The ECU 100 obtains temperature and voltage data from a temperature sensor 102 and a voltage sensor 101. The voltage sensor 101 monitors voltage from the power supply 200. The temperature sensor 102 detects temperature (water temperature, air temperature, or the temperature of the electromagnetically driven valve 1). The ECU 100 is connected to a memory unit 104, in which various map data are stored, including the current cycles and the current values that flows into the coils 62 and 162.
At time t11 the electric current is reduced. Once the arm portion 31 moves upward, downward torsion force is applied to it by the torsion bar 36. As a result, the arm portion 31 moves downward until moves below the neutral position, at which time it stops and then starts to move upward. When it starts moving upward, electric current once more flows to the coils 62 and 162, and the arm portion 31 is strongly drawn upward. This reciprocating motion is repeated from cycle 1 to cycle 3. Through this process, the amplitude of the movements of the valve element 14 gradually becomes greater until the valve element 14 is finally in the closed state. The electric current cycles (cycle 1 to cycle 3 in
Once the valve-closed state shown in
The cycles shown in
The ECU 100 also calculates the number of cycles based on the
That is, in the embodiment of the invention, the electric current, cycle length, and number of cycles for the initial period of operation are mapped according to the temperature and voltage, and are then controlled to conform to the map based on monitoring values that are input from the temperature and voltage sensors. Particularly, when the temperature is very low and the sliding resistance is high, the normal set value for over-current is momentarily increased. When the temperature is very low, the difference between the measured temperature and the heat-resistance limit temperature of the coils 62 and 162 is greater than under normal operating conditions. The amount by which the electric current is increased is therefore set so that the amount of temperature increase in the coils, due to their heating by the increased electric current, will be equal to the increased temperature difference between the measured temperature and the heat-resistance limit temperature of the coils 62 and 162. The number of cycles for the initial period of operation when the temperature is very low is set so that the temperature of an actuator rises enough to lower the high sliding resistance almost to the sliding resistance level under normal operating conditions. That is, the flow of electric current is controlled so that the upper and lower electromagnets 60 and 160 are heated. In an electromagnetically driven valve configured in this manner, the controllability of the electromagnetically driven valve 1 can be improved by accelerating its heating when the temperature is low and the sliding resistance is high.
(Second Embodiment)
The first and second embodiments of the invention have been explained above, but numerous variations of the embodiments shown here are possible. The electromagnetically driven valve is not limited to the single-disc driven type, and it may be structured so that an electromagnet is arranged between two parallel disks.
The embodiments disclosed herein are illustrative examples in every respect and should be considered to be non-limiting. The scope of the invention is indicated not by the explanations above, but by the scope of the claims, and it is intended that the equivalents of the claims and all modifications within the spirit and scope of the claims be included.
The invention can be used, for example, in the field of electromagnetically driven valves for internal combustion engines that are mounted in vehicles.
Number | Date | Country | Kind |
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2005-229605 | Aug 2005 | JP | national |