JP4147685B2 - Solenoid valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetically driven valve, and more particularly to an electromagnetically driven valve provided with an elastic body between a valve body and an armature shaft that prevents the valve body from rebounding during a valve closing operation.
[0002]
[Prior art]
Conventionally, an electromagnetically driven valve has been known as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-13435. The conventional electromagnetically driven valve includes a valve body that functions as an intake valve or an exhaust valve of an internal combustion engine, an armature shaft that is arranged coaxially with the valve body, and an armature that is fixed to the armature shaft. . The valve body and the armature shaft are provided apart from each other in the axial direction, and an elastic body made of a coil spring is interposed in the separated portion.
[0003]
An upper coil and an upper core are disposed above the armature. A lower coil and a lower core are disposed below the armature. Each of the upper coil and the lower coil generates an electromagnetic force that attracts the armature by being supplied with an exciting current.
According to the electromagnetically driven valve of the conventional example, by supplying an exciting current to the upper coil, the valve body can be displaced in the valve closing direction by attracting the armature to the upper coil. In this case, the valve body is fully closed by the armature contacting the upper core. Also, by supplying an exciting current to the lower coil, the valve element can be displaced in the valve opening direction by attracting the armature to the lower coil. In this case, the valve element is fully opened when the armature contacts the lower core. Therefore, the exhaust valve or the intake valve can be repeatedly opened and closed between the fully open state and the fully closed state by supplying an excitation current to the upper coil and the lower coil at an appropriate timing.
[0004]
By the way, the armature that is attracted to the upper coil and displaced upward during the valve closing drive may rebound when it comes into contact with the lower surface of the upper core. When the rebound of the armature is transmitted to the valve shaft, the valve element performs an unnecessary valve opening operation. On the other hand, in the above conventional example, the rebound of the armature is buffered by the coil spring provided between the valve body and the armature shaft. For this reason, according to the electromagnetically driven valve of the conventional example, an unnecessary valve opening operation of the valve body due to the rebound of the armature during the valve closing drive is prevented.
[0005]
[Problems to be solved by the invention]
In general, since the valve body is exposed to the combustion chamber, it is exposed to high heat generated during combustion of the air-fuel mixture during the hot state and becomes a high temperature and is in a state of thermal expansion as compared with the cold state. In the electromagnetically driven valve of the above conventional example, when the valve body is thermally expanded, the clearance between the valve body and the armature shaft becomes small. Therefore, the coil spring provided between the valve body and the armature shaft reduces the clearance. Only further compression. And with compression of a coil spring, the urging | biasing force which a coil spring provides with respect to a valve body in the valve opening direction increases. For this reason, in the electromagnetically driven valve of the above-described conventional example, the force for holding the valve body in the fully closed position during the hot state (hereinafter referred to as the valve closing force) may be lower than that during the cold state and may become insufficient. There is. If the valve closing force on the valve body becomes insufficient, a so-called gas blow-off phenomenon occurs in which the combustion gas unnecessarily blows from the combustion chamber through the gap between the valve body and the valve seat to the exhaust port or intake port. Combustion efficiency will decrease.
[0006]
The present invention has been made in view of the above-described points, and prevents the valve opening operation of the valve body due to the rebound of the armature during the valve closing drive, and suppresses the decrease in the valve closing force accompanying the temperature rise. An object of the present invention is to provide an electromagnetically driven valve capable of
[0007]
[Means for Solving the Problems]
The object is as described in claim 1
An armature driven by cooperation of electromagnetic force by an electromagnetic coil and urging force by an urging member, an armature shaft extending in the axial direction of the armature, and a valve disposed coaxially with the armature shaft An electromagnetically driven valve comprising a body and an elastic body interposed in the spacing portion,
The elastic body is achieved by an electromagnetically driven valve that is a coil spring formed of a shape memory alloy .
[0008]
In such an electromagnetically driven valve, the opening operation of the valve body due to the rebound of the armature during the valve closing drive is prevented by the elastic body. Further, even if the valve body is thermally expanded as the temperature rises and the distance between the armature shaft and the valve body is shortened, the natural length of the elastic body is reduced accordingly. For this reason, an increase in the urging force in the valve opening direction applied from the elastic body to the fully closed valve body is suppressed. Therefore, according to the present invention, it is possible to suppress a decrease in the force for maintaining the valve body in the fully closed position as the temperature rises while preventing the armature from bouncing off during the valve closing drive.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an overall configuration diagram of an electromagnetically driven valve 10 according to an embodiment of the present invention. The electromagnetically driven valve 10 constitutes an exhaust valve of the internal combustion engine 12.
As shown in FIG. 1, the internal combustion engine 12 includes a lower head 14 and an upper head 16 fixed to the upper portion of the lower head 14. An exhaust port 18 is formed in the lower head 14. A combustion chamber 20 is formed in the lower part of the lower head 14. A valve seat 22 is formed at the opening end of the exhaust port 18 on the combustion chamber 20 side.
[0011]
The electromagnetically driven valve 10 includes a valve body 24. The valve body 24 is seated on the valve seat 22 to block the exhaust port 18 from the combustion chamber 20, and the valve body 24 is separated from the valve seat 22 to make the exhaust port 18 and the combustion chamber 20 conductive.
The valve body 24 includes a valve shaft 26. The valve shaft 26 is held so as to be slidable in the axial direction by a valve guide 28 fixed inside the lower head 14 provided in the internal combustion engine 12. A lower retainer 30 is fixed to the upper portion of the valve shaft 26. A cylindrical portion 32 is formed around the valve shaft 26 in the lower head 14. A lower spring 34 is disposed between the lower surface of the lower retainer 30 and the bottom surface of the cylindrical portion 32. The lower spring 34 urges the valve body 24 upward in FIG. 1 via the lower retainer 30.
[0012]
The electromagnetically driven valve 10 also includes an armature shaft 36. The armature shaft 36 is disposed at the same time as the valve shaft 26 and spaced apart upward. In addition, a buffer spring 66 made of a shape memory alloy is interposed in a space between the valve shaft 26 and the armature shaft 36. The buffer spring 66 will be described in detail later.
[0013]
The armature shaft 36 is a rod-shaped member made of a nonmagnetic material. An applicator 38 is fixed to the upper end portion of the armature shaft 36. The upper end of the upper retainer 38 is in contact with the lower end of the upper spring 40. The upper end portion of the upper spring 40 is in contact with the adjustment bolt 42. The upper spring 40 urges the armature shaft 36 downward in FIG. 1 via the upper retainer 38.
[0014]
A disk-shaped armature 44 is joined to the outer periphery of the armature shaft 36. The armature 44 is a member made of a soft magnetic material. A cylindrical portion 46 is formed around the armature shaft 36 in the upper head 16. In the cylindrical portion 46, an upper coil 48 and an upper core 50 are disposed above the armature 44. In the cylindrical portion 46, a lower coil 52 and a lower core 54 are disposed below the armature 44. The energization of the upper coil 48 and the lower coil 52 is controlled by an electronic control unit (hereinafter referred to as ECU) 56.
[0015]
Both the upper core 50 and the lower core 54 are members made of a magnetic material. The upper core 50 and the lower core 54 are provided with through holes 58 and 60 penetrating the center portion, respectively. An upper bearing 62 is disposed at the upper end of the through hole 58 provided in the upper core 50. A lower bearing 64 is disposed at the lower end of the through hole 60 provided in the lower core 54. The upper bearing 62 and the lower bearing 64 are sliding bearings made of a cylindrical metal member or a resin member, respectively. The above-described armature shaft 36 is held by an upper bearing 62 and a lower bearing 64 so as to be slidable in the axial direction.
[0016]
The upper core 50 and the lower core 54 are fitted in the cylindrical portion 46 of the upper head 16 so that a predetermined interval is secured between them. In the above-described adjustment bolt 42, the armature 44 is in a neutral position between the upper core 50 and the lower core 54 by the upper spring 40 and the lower spring 34 in a state where no excitation current is supplied to either the upper coil 48 or the lower coil 52. It has been adjusted to be held in.
[0017]
Next, the operation of the electromagnetically driven valve 10 will be described with reference to FIG.
In the electromagnetically driven valve 10, the valve body 24 is seated on the valve seat 22 when the armature 44 is in contact with the upper core 50. This state is maintained by supplying a predetermined current to the upper coil 48. Hereinafter, the state where the valve body 24 is seated on the valve seat 22 is referred to as a fully closed (valve closed) state, and the position of the valve body 24 at that time is referred to as a fully closed position. FIG. 1 shows the state of the electromagnetically driven valve 10 when the valve body 24 is fully closed.
[0018]
When the excitation current supplied to the upper coil 48 is interrupted while the valve body 24 is maintained at the fully closed position, the electromagnetic force acting on the armature 44 disappears. When the electromagnetic force acting on the armature 44 disappears, the armature shaft 36 and the armature 44 are displaced downward in FIG. 1 by being biased by the upper spring 40. When an appropriate excitation current is supplied to the lower coil 52 when the amount of displacement of the armature 44 reaches a predetermined value, an attractive force that attracts the armature 44 toward the lower core 54 is generated. The armature 44 and the armature shaft 36 are further displaced downward by this suction force.
[0019]
When the armature shaft 36 is displaced downward, the buffer spring 6 is compressed accordingly until the windings are in close contact. When the buffer spring 66 comes into close contact, it cannot contract any further. Therefore, thereafter, the downward displacement of the armature shaft 36 is directly transmitted to the valve shaft 26 through the buffer spring 66 in a close contact state. As a result, the valve body 24 is displaced downward in FIG. 1 against the urging force of the lower spring 34 as the armature 44 and the armature shaft 36 are displaced.
[0020]
Thus, when the valve body 24 is driven to open, the lower end of the armature shaft 36 and the upper end of the valve shaft 26 are not in direct contact, and the valve shaft 26 is pressed against the armature shaft 36 via the buffer spring 66. Is displaced in the valve opening direction. For this reason, the electromagnetically driven valve 10 does not generate a collision sound due to direct contact between the armature shaft 36 and the valve shaft 26. Therefore, according to the present embodiment, the operation sound of the electromagnetically driven valve 10 is reduced.
[0021]
The downward displacement of the valve body 24 continues until the armature 44 contacts the lower core 54. When the armature 44 is in contact with the lower core 54, the valve body 24 is at a position farthest from the valve seat 22. Hereinafter, the state in which the armature 44 contacts the lower core 54 and the valve body 24 is located farthest from the valve seat 22 is referred to as a fully open state, and the position of the valve body 24 at that time is referred to as a fully open position. This fully open state is maintained by supplying a predetermined exciting current to the lower coil 52.
[0022]
When the exciting current supplied to the lower coil 52 is interrupted while the valve body 24 is maintained at the fully open position, the electromagnetic force acting on the armature 44 disappears. When the electromagnetic force acting on the armature 44 disappears, the urging force of the lower spring 34 displaces the valve body 24 upward in FIG. At this time, the armature shaft 36 and the armature 44 are also displaced upward by being pressed by the valve shaft 26 via the buffer spring 68. When an appropriate excitation current is supplied to the upper coil 48 when the amount of displacement of the armature 44 reaches a predetermined value, an attractive force for attracting the armature 44 toward the upper coil 48 is generated.
[0023]
When the above suction force acts on the armature 44, the armature shaft 36 and the armature 44 are further displaced upward in FIG. 1 against the urging force of the upper spring 40. At this time, the upward displacement of the valve body 24 is continued until the valve body 24 is seated on the valve seat 22 and is fully closed. After the valve body 24 is fully closed, the buffer spring 66 that has been in close contact gradually expands as the clearance between the armature shaft 36 and the valve shaft 26 increases. The upward displacement of the armature shaft 36 and the armature 44 continues until the armature 44 contacts the upper core 50.
[0024]
As described above, according to the electromagnetically driven valve 10, the valve body 24 can be displaced toward the fully closed position by supplying a predetermined excitation current to the upper coil 48, and a predetermined excitation current is applied to the lower coil 52. By supplying, the valve body 24 can be displaced toward the fully open state. Therefore, according to the electromagnetically driven valve 10, by alternately supplying an exciting current to the upper coil 48 and the lower coil 52, the valve body 24 can be repeatedly reciprocated between the fully open position and the fully closed position. .
[0025]
Next, the buffer spring 66 that is a main part of the present embodiment will be described in detail.
2A is an enlarged view of the buffer spring 66 and its surroundings when the internal combustion engine 12 is cold, and FIG. 2B is an enlarged view of the buffer spring 66 and its surroundings when the internal combustion engine 12 is hot. FIG. 2A and 2B both show the state of the buffer spring 66 when the valve body 24 shown in FIG. 1 is in a fully closed state.
[0026]
As shown in FIGS. 2A and 2B, protrusions 68 and 69 are formed on the upper end of the valve shaft 26 and the lower end of the armature shaft 36, respectively. The protrusions 68 and 69 have a role of preventing the displacement of the buffer spring 66. The portions around the protrusions 68 and 69 on the upper end surface of the valve shaft 26 and the lower end surface of the armature shaft 36 constitute outer edge portions 70 and 71, respectively.
[0027]
As shown in FIG. 2A, when the internal combustion engine 12 is cold, a clearance C1 is formed between the outer edge portion 70 at the upper end of the valve shaft 26 and the outer edge portion 71 at the lower end of the armature shaft 36. In this embodiment, the buffer spring 66 is configured such that its natural length is slightly smaller than the clearance C1.
On the other hand, when the internal combustion engine 12 is hot, the valve shaft 26 is thermally expanded by the high heat generated by the combustion of the air-fuel mixture in the combustion chamber 20. Therefore, as shown in FIG. 2B, when the internal combustion engine 12 is hot, there is a gap between the outer edge portion 70 at the upper end of the valve shaft 26 and the outer edge portion 71 at the lower end of the armature shaft 36 as compared with the clearance C1. A clearance C2 that is narrow by the thermal expansion of the valve shaft 26 is formed. In this embodiment, the buffer spring 66 is formed of a shape memory alloy so that the natural length thereof is reduced in accordance with the decrease in the clearance due to the temperature rise from the cold time to the hot time. Yes. According to such a configuration, the compression amount of the buffer spring 66 is substantially constant regardless of the temperature. For this reason, the biasing force in the valve opening direction applied to the fully closed valve body 24 by the buffer spring 66 hardly increases even when the temperature rises. Therefore, according to the present embodiment, a decrease in the valve closing force accompanying the temperature rise is suppressed, and the valve body 24 is reliably maintained in the fully closed state.
[0028]
In the present embodiment, the thermal expansion of the valve shaft 26 is absorbed by the clearance between the protrusion 69 at the lower end of the armature shaft 36 and the protrusion 68 at the upper end of the valve shaft 26. Further, when the valve seat 22 is worn, the lower spring 34 displaces the valve shaft 26 upward according to the wear amount, that is, in a direction in which the clearance is reduced, so as to be in close contact with the valve seat 22. Therefore, according to the present embodiment, even if thermal expansion of the valve shaft 26 or wear of the valve seat 22 occurs, the valve body 24 is reliably fully closed.
[0029]
Further, in this embodiment, even if the armature 44 abutting against the upper core 50 at the time of valve closing drive rebounds, the downward displacement of the armature shaft 36 is buffered by the buffer spring 66, so that the valve body at the time of valve closing drive 24 unnecessary valve opening operations are prevented.
As described above, according to the present embodiment, the valve body 24 is surely fully closed when the valve is closed and unnecessary opening operation of the valve body 24 is prevented. However, it is possible to reliably prevent the so-called gas blow-off phenomenon that the air blows from the combustion chamber 20 to the exhaust port through the gap between the valve body 24 and the valve seat 22 unnecessarily.
[0030]
Furthermore, in the present embodiment, the armature shaft 36 and the valve shaft 26 are configured to indirectly contact each other via a buffer spring 66. For this reason, it is suppressed that the high heat which generate | occur | produces with combustion of the air-fuel | gaseous mixture in the combustion chamber 20 is transmitted from the valve body 24 side to the armature shaft 36 side. Therefore, according to the present embodiment, the upper bearing 58 and the lower bearing 64 that hold the armature shaft 36 slidably are prevented from being damaged by high heat.
[0031]
The buffer spring 66 is not limited to the shape memory alloy, and may be made of other materials as long as the natural length decreases as the temperature rises.
In the above embodiment, the upper coil 48 and the lower coil 52 correspond to the “electromagnetic coil” recited in the claims, the lower spring 34 and the upper spring 40 correspond to the “biasing member” recited in the claims, The buffer spring 66 corresponds to an “elastic body” recited in the claims.
[0032]
【The invention's effect】
As described above, in the first aspect of the present invention, the opening operation of the valve body due to the rebound of the armature during the valve closing drive is prevented by the elastic body. Moreover, in this invention, even if temperature rises, the increase in the urging | biasing force of the valve opening direction provided to a valve body from an elastic body at the time of valve closing is suppressed. Therefore, according to the present invention, it is possible to suppress a decrease in the force for maintaining the valve body in the fully closed position as the temperature rises while preventing the armature from bouncing off during the valve closing drive.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an electromagnetically driven valve according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a buffer spring 66 of the internal combustion engine 12 and its surroundings.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Electromagnetic drive valve 12 Internal combustion engine 24 Valve body 26 Valve shaft 34 Lower spring 40 Upper spring 36 Armature shaft 44 Armature 48 Upper coil 50 Upper core 52 Lower coil 54 Lower core 56 ECU
66 Buffer spring

Claims (1)

An armature driven by cooperation of electromagnetic force by an electromagnetic coil and biasing force by a biasing member, an armature shaft extending in an axial direction of the armature, and a valve disposed coaxially with the armature shaft An electromagnetically driven valve comprising a body and an elastic body interposed in the spacing portion,
The electromagnetically driven valve is characterized in that the elastic body is a coil spring formed of a shape memory alloy .

Images