Patent Application
20110042491
The present invention relates to a fuel injection valve used in internal combustion engines, in which a valve element abuts against a valve seat to thereby prevent leakage of a fuel and the valve element separates from the valve seat to perform injection.
JP-B2-3737122 discloses a fuel injection valve, in which a spherical surface on a valve element side and a conical surface on a valve seat side abut against each other to thereby seal a fuel, a transition section is provided between a valve shaft and a conical section, and a sealing seat formed as a narrow spherical zone is provided between the transition section and the conical section.
Electromagnetic type fuel injection valves are generally used for fuel injection valves that supply a fuel to internal combustion engines. Here, problems will be described taking an electromagnetic type fuel injection valve as an example. Electromagnetic type fuel injection valves are normally closed type electromagnetic valves, in which a valve element is normally pushed against a valve seat surface by a bias spring to bring about a closed state. When an electric current is introduced to a coil to generate an electromagnetic force, the valve element and the valve seat surface are caused to separate from each other to create a clearance to bring about an opened state.
Here, in the opened state, when a fuel passes through a clearance between the valve element and a valve seat, an increase in velocity of flow or in pressure loss is caused and a decrease in static pressure at a tip end of the valve element is caused. Therefore, the valve element in the opened state is pushed by fuel pressure in a valve closing direction.
In order to maintain the opened state against the force in the valve closing direction, it is necessary to increase an electric current introduced to a coil to increase an electromagnetic force, or to set a range of fuel pressure as used small, or to make a force, which is given by the bias spring, smaller than a predetermined value. Among these measures, there is a limit in electric power, which can be introduced to the coil, because of heat generation of the coil, attendant shortening of life, and thermal degradation of resin members. Also, because of the effect on engine combustion performance, it is not preferred that a usable range of fuel pressure be set small.
Here, when a force, which is given by the bias spring, is set small, there is caused a problem that a force, which closes the valve element, becomes small to bring about a decrease in responsibility. In the course of valve closing, the force of the bias spring and a fluid force by a fuel cause the valve element to perform a valve closing motion, and when the force by the bias spring is set small so that a workable maximum fuel pressure (maximum working fuel pressure) becomes large, a small fuel pressure enables the valve element not to sufficiently receive a force required for valve closing and time required for valve closing is prolonged. That is, a valve closing delay time is prolonged.
The valve closing delay time is a response delay time of a fuel injection valve related to a valve closing motion and a delay time which determines a controllable minimum injection quantity. That is, when a bias spring force is small, there is caused a problem that a valve closing delay time is prolonged and a controllable minimum injection quantity increases.
Accordingly, in order to make a controllable minimum injection quantity fairly small, in other words, to shorten a valve closing delay time, it is necessary to set a bias spring force large. Here, in order that a maximum working fuel pressure does not become small, it is necessary to decrease a fluid force acting on a valve element.
The invention has been thought of in view of the above and has its object to decrease a fluid force acting on a valve element.
In order to solve the above problems, according to the invention, a valve element or a seat member is shaped so that in a region extending from a spherical surface portion, which forms a sealing portion of the valve element, to a portion, which becomes in parallel to a cylindrical-shaped portion of the valve element, a clearance between a valve seat and the valve element is made larger than a distance between a circular arc, which connects between a terminal end of the spherical surface portion and the cylindrical-shaped portion, and a conical surface, which forms the valve seat. As a result that a fluid (fuel) increases in velocity of flow at a tip end of the valve element and dynamic pressure increases, so that static pressure decreases according to Bernoulli's theorem, or static pressure decreases due to pressure loss resulted at the tip end of the valve element, a major part of a force caused by the fuel to act on the valve element is a force due to the fact that the tip end of the valve element acts as a pressure receiving surface. Accordingly, when it is tried to decrease this force, it is necessary to decrease a fuel in velocity of flow, or to narrow a region, which is high in velocity of flow, to narrow a region for reception of the decreased static pressure. According to the invention, a region at the tip end of the valve element, which decreases in static pressure, or pressure loss to be occurred can be decreased by decreasing a region, in which a fuel is high in velocity of flow, in the vicinity of a sealing portion at the tip end of the valve element. As a result, it is possible to obtain a fuel injection valve, in which a bias spring force acting on the valve element can be increased and which is decreased in valve closing delay time and exhibits a good responsibility.
According to the invention, it is possible to obtain a fuel injection valve, in which a force given by flow of a fuel acting on a valve element can be decreased and a maximum fuel pressure enabling the fuel injection valve to work can be increased, or which is made good in responsibility even at the time of low pressure by setting a bias spring force high. As a result, it is possible to obtain a fuel injection valve, in which, for example, a controllable minimum injection quantity is small and which realizes an internal combustion engine being made high in one of fuel consumption, exhaust, and output performances.
Other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention when taken in conjunction with the accompanying drawings.
Embodiments of an electromagnetic type fuel injection valve according to the invention will be described hereinafter.
In
When the coil 108 is energized, magnetic flux is generated on a core 107, a yoke 109, and an anchor 106, which constitute a magnetic circuit of the electromagnetic valve, so that magnetic attraction is generated between the core 107 and the anchor 106, between which a clearance is present. When the magnetic attraction become larger than the force produced by the bias of the spring 110 and the fuel pressure as described above, the valve element 101 is attracted toward the core 107 by the anchor 106 to bring about a valve opened state.
When put in the valve opened state, a clearance is generated between the valve seat 203 and the spherical surface 202 of the valve element and fuel injection is started. When fuel injection is started, energy given as the fuel pressure is converted into kinetic energy to reach the injection ports 201 to result in injection.
The valve element 101 together with the anchor 106 is enclosed in a nozzle holder 104. The valve element 101 is guided in two locations in a direction of driving by a guide member 103 provided on a tip end side, on which the sealing portions are formed, and a valve element guide 105 provided on a base end side, on which the anchor 106 is provided. The guide member 103 and the valve element guide 105 are provided on the nozzle holder 104 so as to guide the valve element 101 in two locations in a direction along a central axis of the valve element (a direction of valve axis).
When the valve element 301 is displaced and the valve is put in a valve opened state, a fuel passes through a clearance between the valve element 301 and a valve seat member 302. It is important in restricting a displacement magnitude that the clearance between the valve element 301 and the valve seat member 302 be set comparatively small. That is, in order to make the fuel injection valve good in responsibility, it is important that a displacement magnitude don't become too large. Therefore, flow of a fuel passing through a small clearance increases in velocity of flow 303.
Generally, when a fuel increases in velocity of flow, dynamic pressure (ρv2)/2 (ρ indicates density of fluid and v indicates velocity of flow) increases and pressure loss becomes large in proportion to dynamic pressure. When pressure loss occurs in this manner, pressure below the valve element decreases. Also, when an increase in velocity of flow causes an increase in dynamic pressure, a part being high in velocity of flow decreases in static pressure according to Bernoulli's theorem.
The valve element receives a fuel pressure supplied on an upstream side thereof (for example, a position in contact with the spring 110) and is pushed back by fuel pressure on a downstream side thereof (that is, on the side toward the valve seat member 102), and a difference therebetween presents a force acting on the valve element. Accordingly, a decrease in static pressure due to conversion into kinetic energy and a decrease in static pressure due to pressure loss cause pressure indicated by arrows 305 to act as a force acting on the valve element at a tip end thereof and lowering the valve element in a valve closing direction.
In the present embodiment, the valve element is formed in external shape as shown in
The spherical surface 202 is formed with a seat portion 202a which comes into contact with a seat portion 203a of the valve seat 203, and in a region extending from an upstream side 202b to a downstream side 202c, a spherical surface portion is formed. A center of the spherical surface portion is positioned as indicated by O. In the present embodiment, the spherical surface 202 has the same radius as that of the cylindrical-shaped portion 205.
A wide angle conical surface 203b having a wider angle than that of the conical surface, which defines the valve seat 203 is formed upstream of the valve seat 203, and the wide angle conical surface 203b is contiguous to a conical surface, which defines the valve seat 203 inwardly (toward a valve axis) of a cylindrical-shaped surface forming the cylindrical-shaped portion 205 in a direction perpendicular to the valve axis.
In the cross sectional view of
When flow goes toward the central axis of the fuel injection valve, it will go in a direction, in which a radius decreases, thus showing a tendency that a cross sectional area of a flow passage decreases essentially and linearly.
Description will be given along positions in the flow direction. At a position, like a position 401 shown in
In the present embodiment, a clearance enlarged portion is provided on a valve element portion between the cylindrical-shaped portion 205 and the spherical surface 202 to enlarge a clearance between the valve element 101 and the valve seat 203 further than the case where the valve element is shaped by connecting the virtual cylindrical-shaped surface 205a and the spherical surface 202 together by the circular arc (a virtual spherical surface) 202d. For example, it is preferred that the conical surface 204 as shown in
In addition, in
In the present embodiment, also by providing the wide angle conical surface 203b, a clearance area between the valve element 101 and the valve seat 203 is larger in comparison with the case where the valve seat 203 is defined by a single conical surface. At this time, the valve element 101 may have a valve element configuration provided by connecting the virtual cylindrical-shaped surface 205a and the spherical surface 202 together by the circular arc (a virtual spherical surface) 202d. Even when the wide angle conical surface 203b is not provided, only the conical surface 204 of the valve element 101 enables enlarging a clearance area between the valve element 101 and the valve seat 203 as described above.
In case of providing the conical surface 204, it is preferred that the spherical surface 202 be provided up to an upstream side of a position (a seated position) in contact with the valve seat 203 and the spherical surface 202 and the conical surface 204 are connected smoothly together.
In this manner, by making a distance between a tip end surface of the valve element 101 and the valve seat 203 large, the cross sectional area of the flow passage between the valve element 101 and the valve seat 203 can greatly cover a wide region. That is, a clearance, as shown by the point 402 in
By decreasing the force acting on the valve element 101, it is possible to decrease a force, with which the valve element 101 is closed by fuel pressure, and as a result, that range of fuel pressure, in which the fuel injection valve can operate, can be set on a high pressure side. As a result, it is possible to provide a fuel injection valve, by which a fuel further atomized due to use in high pressure is injected. Also, it is possible to provide a fuel injection valve, in which fuel pressure is wide in range of use and of which injection quantity is made large in flow rate by the use at variable fuel pressures.
Alternatively, also by increasing the preset load of the spring 110, it is possible to maintain a workable range of fuel pressure. In this manner, in the case where the preset load of the spring 110 is made large, it is possible to make a valve closing motion of a fuel injection valve quick. Since a controllable minimum injection quantity is determined by time required for the valve closing motion of a fuel injection valve, the controllable minimum injection quantity of a fuel injection valve can be decreased when the preset load of the spring 1101 is made large. As a result, it is possible to provide a fuel injection valve capable of meeting an operating condition, which needs a further small injection quantity.
In addition, in the present embodiment, the cylindrical-shaped portion 205 is made a smaller cylindrical-shaped surface than the sliding guide surface 206 of the valve element in order to enlarge a region outwardly of the point 501 in
In case of using the spherical body 602 for the valve element 601, a seat member is shaped so that in a region extending to a seat position from a position 603 in parallel to the shaft portion 607, the cross sectional area of a flow passage in a clearance between the valve element (the spherical body 602) and the seat conical surface 604 is enlarged as compared with the case where the position 603 and the seated position are connected together by a circular arc.
The flat surface portion 606 is provided and a point of intersection of the flat surface portion 606 and the seat conical surface 604 is set inwardly of a diameter of the position 603 in parallel to a cylinder corresponding to a sphere used for the valve element 601 but outwardly of a diameter of the seat position, whereby the cross sectional area of a flow passage in a clearance between the seat conical surface 604 and the spherical body 602 is enlarged while oiltightness of the seat is ensured.
In contrast, according to the present embodiment, outside a point 702a in a fluid passage at a point of intersection of the flat surface portion 606 and the seat conical surface 604, a clearance between the valve element and the seat conical surface can be enlarged as shown by a line 706. That is, the provision of the flat surface portion 606 enables making the cross sectional area of a passage large as shown by a line 706 even in a region, in which a clearance is essentially narrow as shown by the line 705.
As a result, it is possible to narrow a region, in which a large velocity of flow caused by narrowness of a fluid passage is generated, outside a seat position 703b (on an upstream side in a flow direction). Therefore, a decrease in static pressure and pressure loss due to an increase in dynamic pressure can be restricted and by decreasing area of influence, it is possible to decrease a force acting on the valve element 601 in the valve closing direction.
While the above description has been given with respect to the embodiments, it is apparent to those skilled in the art that the invention is not limited thereto but susceptible of various changes and modifications within the spirit of the invention and the scope of the appended claims.
While an in-cylinder direct injection type electromagnetic fuel injection valve for gasoline engines has been described by way of example, the invention is effective in port injection type electromagnetic fuel injection valves for gasoline engines and fuel injection valves driven by piezo elements and magnetostrictive elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-220678 | Aug 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/062729 | 7/14/2009 | WO | 00 | 10/19/2010 |
