Electromagnetic fuel injection valve

In an electromagnetic fuel injection valve in which a valve assembly formed by integrally connecting a valve element and a movable core to each other is contained in a valve housing, and a first journal part and a second journal part are provided in the valve assembly so as to be supported slidably in the guide hole in a valve housing, the outside surface of the first journal part (21) is formed by a sliding surface (45) slidable on the inside surface of the guide hole (14) and a pair of tapered tilt surfaces (46, 47) connecting to both the front and rear sides of the sliding surface (45); at least the tilt surface (47) on the movable core side, of both the tilt surfaces (46, 47), is formed of a first tilt surface part (47a) connecting to an end part of the sliding surface (45) and a second tilt surface part (47b) connecting to the first tilt surface part (47a); and an angle that the first tilt surface part (47a) makes with a plane perpendicular to the axis line of a valve shaft part (19b) is set larger than an angle that the second tilt surface part (47b) makes with the plane. Whereby a decrease in initial fitting property and an increase in abrasion loss can be avoided, and the weight of the valve assembly can be reduced while good response and flow characteristic are maintained.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Stage entry of International Application No. PCT/JP2005/003127, filed Feb. 25, 2005, the entire specification claims and drawings of which are incorporated herewith by reference.

TECHNICAL FIELD

The present invention relates to an electromagnetic fuel injection valve including a valve assembly in which a fixed core is connectingly provided at a rear end of a valve housing having a valve seat in a front end part thereof, and a valve element having a valve part capable of being seated on the valve seat and a valve shaft part connecting with the valve part and a movable core opposed to the fixed core are integrally connected to each other, the valve assembly being contained in the valve housing by being urged by spring to the side on which the valve part is seated on the valve seat, a first journal part close to the valve seat and a second journal part separated from the first journal part to the rear side in the axial direction being provided in the valve assembly so as to be slidably supported by a guide hole provided in the valve housing.

BACKGROUND ART

An electromagnetic fuel injection valve in which first and second journal parts, which are slidably supported by a guide hole in a valve housing, are provided in a valve shaft part in a valve assembly with an interval provided in the axial direction, and the outside surface of the first journal part close to a valve seat, of both the journal parts, is formed by a sliding surface capable of sliding on the inside surface of a guide hole provided in the housing and a pair of tapered tilt surfaces connected to both the front and rear sides of the sliding surface has already been known, for example, in Patent Document 1.Patent Document 1: Japanese Utility Model Application Laid-open No. 60-88070.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

In the above-mentioned electromagnetic fuel injection valve, a guide clearance between the first and second journal parts provided in the valve assembly and the valve housing is generally set larger on the second journal part side than on the first journal part side considering the assembly of the valve assembly into the valve housing. In the state in which a valve part is seated on the valve seat, therefore, there is a possibility that the valve assembly might tilt. The tilt angle depends on the guide clearance on the second journal part side, and in a state in which the valve part is seated, the first journal part does not come into contact with the inside surface of the guide hole. However, when the valve assembly while being tilted is operated to the valve open side due to the action of an electromagnetic attraction force to a movable core, the first journal part turns with a portion in which the second journal part is in contact with the inside surface of the guide hole being a support point so as to come into contact with the inside surface of the guide hole, and the end part on the movable core side, of the sliding surface forming a part of the outside surface of the first journal part, comes into contact with the inside surface of the guide hole. When the valve assembly is operated in the valve closing direction by an urging force of spring in this state, the end part on the movable core side, of the sliding surface of the first journal part, comes into sliding contact with the inside surface of the guide hole.

In order to reduce the weight of valve assembly by forming the journal part as small as possible, it is preferable that an angle that the tapered tilt surfaces connected to the opposite ends of the sliding surface provided along the axis line direction of the valve shaft part make with a plane perpendicular to the axis line be made as small as possible. However, if the angle is set too small, a connection part between the sliding surface and the tilt surface has an acute angle. In particular, as described above, the connection part between the tilt surface on the movable core side and the sliding surface, of the outside surface of the first journal part, is liable to come into contact with the inside surface of the guide hole according to the tilt of valve assembly, and if the connection part between the tilt surface and the sliding surface has an acute angle, initial fitting with respect to the inside surface of the guide hole is not so good, and the abrasion loss increases, so that the width of sliding surface is liable to change due to the abrasion of the sliding surface. As a result, the response changes, which induces a change in the flow characteristic of fuel.

A simple approach to the solution of this problem is to form the connection part between the tilt surface and the sliding surface so as to be curved. However, this approach results in a comparatively great change in an angle that the connection part makes with the sliding surface due to the abrasion of the sliding surface, which exerts a great influence on the state of friction.

The present invention has been achieved in view of the above-mentioned circumstances, and has an object to provide an electromagnetic fuel injection valve in which the weight of a valve assembly can be reduced while avoiding a decrease in initial fitting property and an increase in abrasion loss and maintaining good response and flow characteristic.

Means for Solving the Problems

In order to achieve the object, according to a first feature of the present invention, there is proposed an electromagnetic fuel injection valve including a valve assembly in which a fixed core is connectingly provided at a rear end of a valve housing having a valve seat in a front end part thereof, and a valve element having a valve part capable of being seated on the valve seat and a valve shaft part connecting to the valve part and a movable core opposed to the fixed core are integrally connected to each other, the valve assembly being contained in the valve housing by being urged by spring to the side on which the valve part is seated on the valve seat, a first journal part close to the valve seat and a second journal part separated from the first journal part to the rear side in the axial direction being provided in the valve assembly so as to be slidably supported by a guide hole provided in the valve housing, characterized in that the outside surface of the first journal part is formed by a sliding surface slidable on the inside surface of the guide hole and a pair of tapered tilt surfaces connecting to both the front and rear sides of the sliding surface; at least the tilt surface on the movable core side, of both the tilt surfaces, is formed of a first tilt surface part connecting to an end part of the sliding surface provided along the axis line of the valve shaft part and a second tilt surface part connecting to the first tilt surface part; and an angle that the first tilt surface part makes with a plane perpendicular to the axis line of the valve shaft part is set larger than an angle that the second tilt surface part makes with the plane.

According to a second feature of the present invention, in addition to the first feature, there is proposed an electromagnetic fuel injection valve in which the sliding surface of the first journal part is formed so that the length thereof in the direction along the axis line of the valve housing is 0.2 to 0.3 mm.

According to a third feature of the present invention, in addition to the first feature, there is proposed an electromagnetic fuel injection valve in which the valve part seated on the valve seat which is tapered is formed in a semispherical shape along an imaginary spherical surface, and the first journal part having the sliding surface slidable in the guide hole in the valve housing is provided in the valve shaft part so that a plane passing through the spherical surface center of the valve part and perpendicularly to the axis line of the valve shaft part is located within the width of the sliding surface.

According to a fourth feature of the present invention, in addition to the third feature, there is proposed an electromagnetic fuel injection valve in which the radius of the sliding surface is set smaller than the radius of the imaginary spherical surface.

According to a fifth feature of the present invention, in addition to the third or fourth feature, there is proposed an electromagnetic fuel injection valve in which the diameter of the valve shaft part is set smaller than the seal diameter at the time when the valve part is seated on the valve seat; at a plurality of places in the circumferential direction of the sliding surface having a larger diameter than that of the seal, a chamfered part for allowing fuel to flow is formed; and the valve assembly is provided with a fuel passage having at least a longitudinal hole having a rear end thereof opened and a front end thereof closed and extending coaxially with the valve shaft part, and a transverse hole leading to the longitudinal hole at the rear from the first journal part.

EFFECT OF THE INVENTION

With the first feature of the present invention, at least the tilt surface on the movable core side, of both the tapered tilt surfaces forming a part of the outside surface of the first journal part, is formed of a first tilt surface part having a sharp slope and a second tilt surface part having a gentle slope, and the first tilt surface part is connected to the end part on the movable core side of the sliding surface, so that the first journal part is formed so as to be as small as possible, whereby the weight of the valve assembly can be reduced. In addition, although a connection part between the tilt surface on the movable core side and the sliding surface easily comes into contact with the inside surface of the guide hole according to the tilt of the valve assembly, at least the connection part between the tilt surface on the movable core side and the sliding surface is prevented from having an acute angle, so that the initial fitting property to the inside surface of the guide hole is good, and the abrasion loss can be kept small. Therefore, good response and flow characteristic can be maintained. Also, since at least the tilt surface on the movable core side is connected to the sliding surface with an angle, the width of the sliding surface is hard to be changed due to the abrasion of the sliding surface, and also the angle that the tilt surface on the movable core side and the sliding surface make does not change, so that an adverse influence is not exerted on the state of friction.

With the second feature of the present invention, even if the guide clearance between the guide hole in the valve housing and the first journal part is set small, setting of the width of the sliding surface as small as about 0.2 to 0.3 mm enables the valve assembly to be opened and closed without impairing the degree of freedom, and also contributes to a decrease in slide resistance.

With the third feature of the present invention, by seating the semispherical valve part on the tapered valve seat, the aligning property of the valve element can be enhanced, and moreover, by arranging the sliding surface of the first journal part at a position closer to the valve part, the guide clearance between the guide hole in the valve housing and the first journal part can be set small. Therefore, the deflection of the valve part at the time of valve closing operation is restrained, and the sealing ability at the time when the valve is seated to be closed can be improved.

With the fourth feature of the present invention, even if the valve assembly swings in the state in which the valve part is seated on the valve seat, the guide clearance can be set smaller so that the sliding surface of the first journal part does not come into contact with the inside surface of the guide hole. Therefore, the deflection of the valve part at the time of valve closing operation is restrained more effectively, and the sealing ability at the time when the valve is seated to be closed can be enhanced. In addition, a smaller diameter of the first journal part can reduce the weight of the valve assembly.

With the fifth feature of the present invention, by decreasing the diameter of the valve shaft part and making the valve assembly hollow, the weight of the valve assembly can further be reduced. In addition, since the fuel from the fuel passage flows through the chamfered parts provided at the plurality of places in the circumferential direction of the sliding surface of the first journal part, the flow of fuel near the valve seat can be stabilized, and thereby the behavior of the valve assembly can also be stabilized.

BEST MODE FOR CARRYING OUT THE INVENTION

A mode for carrying out the present invention will now be described based on one embodiment of the present invention shown in the accompanying drawings.

FIGS. 1 to 4show one embodiment of the present invention.

First, inFIG. 1, an electromagnetic fuel injection valve for injecting fuel into an engine, not shown, includes a valve operating portion5in which a valve assembly20urged by spring in such a direction as to be seated on a valve seat13is contained in a valve housing8having the valve seat13at the front end thereof; a solenoid portion6in which a coil assembly30capable of generating an electromagnetic force for driving the valve assembly20to the side such as to be unseated from the valve seat13is contained in a solenoid housing31connectingly provided on the valve housing8; and a synthetic resin made covering portion7integrally having a coupler42for coupling connection terminals41connecting with a coil36of the coil assembly30, in which at least the coil assembly30and the solenoid housing31are sealingly embedded.

The valve housing8is made up of a magnetic cylindrical body9formed of a magnetic metal and a valve seat member10connected to the front end of the magnetic cylindrical body9in a fluid-tight manner. The valve seat member10is welded to the magnetic cylindrical body9in a state in which the rear end part thereof is fitted in a front end part of the magnetic cylindrical body9. The valve seat member10is provided coaxially with a fuel outlet hole12that is open in the front end surface thereof, the tapered valve seat13connecting with the inner end of the fuel outlet hole12, and a front guide hole14connecting with a large-diameter part at the rear end of the valve seat13, and the magnetic cylindrical body9is provided with a rear guide hole15which connects coaxially with the front guide hole14and is formed so as to have a diameter larger than that of the front guide hole14. Also, at the front end of the valve seat member10, a steel plate made injector plate17having a plurality of fuel injection holes16leading to the fuel outlet hole12is welded all the way around in a fluid-tight manner.

In the valve housing8, the valve assembly20in which a valve element19having a valve part19acapable of being seated on the valve seat13and a valve shaft part19bconnecting with the valve part19aand a movable core18forming a part of the solenoid portion6are formed integrally by using the same material is contained by being urged by spring to the side on which the valve part19ais seated on the valve seat13.

The valve assembly20is provided with a first journal part21slidably supported by the front guide hole14provided in the valve housing8and a second journal part22which is disposed at the rear in the axial direction of the first journal part21so as to be slidably supported by the rear guide hole15provided in the valve housing8. The first journal part21is provided in the valve shaft part19bclose to the valve seat13, and the second journal part22is provided on the movable core18.

The valve assembly20is provided with a longitudinal hole23extending coaxially with the valve shaft part19b,the rear end of which is opened and the front end of which is closed by the valve part19a,and a plurality of sets of transverse holes24aand24bleading to the longitudinal hole23so as to form a fuel passage25through cooperation of these holes.

The transverse holes24aare provided in the valve shaft part19bbetween the first journal part21and the valve part19a,and the transverse holes24bare provided in the movable core18.

The solenoid portion6includes the movable core18, a cylindrical fixed core28opposed to the movable core18, a return spring29for generating a spring force to urge the movable core18to the side on which the movable core18is separated from the fixed core28, the coil assembly30arranged so as to surround a rear part of the valve housing8and the fixed core28to enable an electromagnetic force for attracting the movable core18to the fixed core28side against the spring force of the return spring29to be generated, and the solenoid housing31surrounding the coil assembly30so that the front end part thereof is connected to the valve housing8.

The rear end of the magnetic cylindrical body9of the valve housing8is coupled coaxially to the front end of the fixed core28via a nonmagnetic cylindrical body32formed of a nonmagnetic metal such as stainless steel. The rear end of the magnetic cylindrical body9is butt welded to the front end of the nonmagnetic cylindrical body32, and the rear end of the nonmagnetic cylindrical body32is welded to the fixed core28in a state in which the front end part of the fixed core28is fitted in the nonmagnetic cylindrical body32.

In the fixed core28, a cylindrical retainer33is coaxially fitted and fixed by staking, and the return spring29is interposed between the retainer33and the movable core18. At the inner periphery of the rear end part of the movable core18, a ring-shaped stopper34formed of a nonmagnetic material is pressed in so as to slightly protrude from the rear end surface of the movable core18toward the fixed core28to avoid a direct contact of the movable core18to the fixed core28. Also, the coil assembly30is formed by winding the coil36on a bobbin35surrounding the rear part of the valve housing8, the nonmagnetic cylindrical body32, and the fixed core28.

The solenoid housing31includes a magnetic frame37, which has, at one end thereof, an annular end wall37aopposed to the end part on the valve operating portion5side of the coil assembly30and is formed of a magnetic metal in a cylindrical shape surrounding the coil assembly30, and a flange part28a,which protrudes from the rear end part of the fixed core28outward in the radial direction and is opposed to the end part on the opposite side from the valve operating portion5of the coil assembly30. The flange part28ais coupled magnetically to the other end part of the magnetic frame37. In addition, at the inner periphery of the end wall37aof the magnetic frame37, a fitting cylinder part37bfor fitting the magnetic cylindrical body9of the valve housing8is provided coaxially, and the solenoid housing31is connected to the valve housing8by fitting the valve housing8in the fitting cylinder part37b.

At the rear end of the fixed core28, a cylindrical inlet cylinder38is connectingly provided integrally and coaxially, and a fuel filter39is mounted in the rear part of the inlet cylinder33. In addition, a fuel passage40leading to the longitudinal hole23in the movable core18is provided coaxially in the inlet cylinder38, the retainer33, and the fixed core28.

The covering portion7is formed so that not only the solenoid housing31and the coil assembly30are sealingly embedded but also a part of the valve housing8and most of the inlet cylinder38are sealingly embedded while a gap between the solenoid housing31and the coil assembly30is filled. The magnetic frame37of the solenoid housing31is provided with a notch part43for arranging an arm part35a,which is formed integrally with the bobbin35of the coil assembly30, on the outside of the solenoid housing31.

The covering portion7is integrally provided with the coupler42for coupling the connection terminals41connecting with both ends of the coil36of the coil assembly30. The proximal end of the connection terminal41is embedded in the arm part35a,and coil ends36aof the coil36are welded to the connection terminals41.

InFIG. 2, the valve seat13is formed in a tapered shape, and the valve part19aseated on the valve seat13is formed in a semispherical shape along an imaginary spherical surface S. On the other hand, the first journal part21slidably supported in the front guide hole14in the valve housing8is formed by a sliding surface45slidable in the front guide hole14and a pair of tapered tilt surfaces46and47connecting with both the front and rear sides of the sliding surface45. The first journal part21is provided in the valve shaft part19bso that a plane P passing through the spherical surface center C of the valve part19aperpendicularly to the axis line of the valve shaft part19bis located within the width of the sliding surface45.

In addition, the radius R1of the sliding surface45is set smaller than the radius R2of the imaginary spherical surface S, and the sliding surface45is formed so that the length thereof in the direction along the axis line of the valve housing8, namely, a width L is 0.2 to 0.3 mm.

Also, the diameter D2of the valve shaft part19bis set smaller than the seal diameter D1at the time when the valve part19ais seated on the valve seat13, and the diameter D3(=R1×2) of the sliding surface45is set larger than the seal diameter D1.

InFIG. 3, at least the tilt surface47on the movable core18side, of the paired tilt surfaces46and47forming a part of the outside surface of the first journal part21, in this example, the tilt surface47on the movable core18side is made up of a first tilt surface part47aconnecting with the end part of the sliding surface45provided along the axis line of the valve shaft part19band a second tilt surface part47bconnecting with the first tilt surface part47a.An angle a that the first tilt surface part47amakes with a plane perpendicular to the axis line of the valve shaft part19bis set larger than an angle β that the second tilt surface part47bmakes with the said plane. In this example, α and β are set at 70 degrees and 20 degrees, respectively.

Also, the tilt surface46on the valve seat13side, of the paired tilt surfaces46and47that the first journal part21has, is formed in a tapered shape with an angle γ with respect to the plane perpendicular to the axis line of the valve shaft part19bbeing fixed. In this example, the angle γ is set at 45 degrees.

InFIG. 4, at a plurality of places in the circumferential direction of the sliding surface45of the first journal part21, plane-shaped chamfered parts45afor allowing fuel to flow are formed, so that the fuel flowing into the valve housing8through the transverse holes24bof the fuel passage25passes between the chamfered parts45aand the valve housing8and flows to the valve seat13side.

Next, the operation of this embodiment will be explained. The outside surface of the first journal part21close to the valve seat13, of the first and second journal parts21and22provided on the valve assembly20, is made up of the sliding surface45slidable on the inside surface of the front guide hole14provided in the valve seat member10of the valve housing8and the paired tapered tilt surfaces46and47connecting with both the front and rear sides of the sliding surface45. The tilt surface47on the movable core18side, of both the tilt surfaces46and47, is made up of the first tilt surface part47aconnecting with the end part of the sliding surface45provided along the axis line of the valve shaft part19band the second tilt surface part47bconnecting with the first tilt surface part47a,and the angle a that the first tilt surface part47amakes with the plane perpendicular to the axis line of the valve shaft part19bis set larger than the angle β that the second tilt surface part47bmakes with the said plane.

That is to say, the tilt surface47on the movable core18side, of the tapered tilt surfaces46and47forming a part of the outside surface of the first journal part21, is made up of the first tilt surface part47ahaving a sharp slope and the second tilt surface part47bhaving a gentle slope. Therefore, the first journal part21is formed so as to be as small as possible, by which the weight of the valve assembly20can be reduced.

In addition, although the connection part between the tilt surface47on the movable core18side and the sliding surface45easily comes into contact with the inside surface of the front guide hole14according to the tilt of the valve assembly20, since the first tilt surface part47ahaving a sharp slope is connected to the end part of the movable core18side of the sliding surface45, the connection part between the tilt surface47on the movable core18side and the sliding surface45is prevented from having an acute angle, so that the initial fitting property to the inside surface of the front guide hole14is good, and the abrasion loss can be kept small. Therefore, good response and flow characteristic can be maintained.

Also, since at least the tilt surface47on the movable core18side, in this embodiment, both the tilt surfaces46and47are connected to the sliding surface45with an angle, the width of the sliding surface45is less liable to be changed due to the abrasion of the sliding surface45, and also the angles that both the tilt surfaces46and47and the sliding surface45make do not change, so that an adverse influence is not exerted on the state of friction.

In addition, since the sliding surface45of the first journal part21is formed so that the length L in the direction along the axis line of the valve housing8is 0.2 to 0.3 mm, even if the guide clearance between the front guide hole14in the valve housing8and the first journal part21is set small, the setting of the width of the sliding surface45as small as about 0.2 to 0.3 mm enables the valve assembly20to be opened and closed without impairing the degree of freedom, and also contributes to a decrease in slide resistance.

The guide clearance between the first and second journal parts21and22provided in the valve shaft part19bof the valve assembly20and the valve housing8is generally set so that the guide clearance on the second journal part22side is larger than that on the first journal part21side considering the assembly of the valve assembly20into the valve housing8. Therefore, in the state in which the valve part19ais seated on the valve seat13, there is a possibility that the valve assembly20tilts, and the tilt angle depends on the guide clearance on the second journal part22side, so that it is necessary to set the diameter of the first journal part21so that in the state in which the valve part19ais seated, the first journal part21does not come into contact with the inside surface of the front guide hole14.

On the other hand, if the diameter of the first journal part21is made small and the guide clearance is made too large, the deflection of the valve part19aat the time of valve opening operation becomes great, so that exact seating of the valve part19aon the valve seat13is difficult to perform, which may result in a decrease in sealing ability at the time of seating.

In the electromagnetic fuel injection valve disclosed in Patent Document 1 (Japanese Utility Model Application Laid-open No. 60-88070), the first journal part is provided in the valve shaft part at a position comparatively distant from the valve part to the rear side, so that the guide clearance in the first journal part must inevitably be set comparatively large. Therefore, the deflection of the valve part at the time of valve opening operation becomes great, and the sealing ability at the time of seating may decrease.

By contrast, in the present invention, the valve part19aseated on the valve seat13formed in a tapered shape is formed in a semispherical shape along the imaginary spherical surface S, and the first journal part21is provided in the valve shaft part19bso that the plane P passing through the spherical surface center C of the valve part19aperpendicularly to the axis line of the valve shaft part19bis located within the width of the sliding surface45.

Thereupon, by seating the semispherical valve part19aon the tapered valve seat13, the aligning property of the valve element19can be enhanced, and also by arranging the sliding surface45of the first journal part21at a position closer to the valve part19a,the guide clearance between the front guide hole14in the valve housing8and the first journal part21can be set, for example, as small as 4 to 6 μm. Therefore, the deflection of the valve part19aat the time of valve opening operation is restrained, and the sealing ability at the time when the valve is seated to be closed can be improved.

Also, since the radius R1of the sliding surface45of the first journal part21is set smaller than the radius R2of the imaginary spherical surface S, even if the valve assembly20swings in the state in which the valve part19ais seated on the valve seat13, the guide clearance can be set smaller so that the sliding surface45of the first journal part21does not come into contact with the inside surface of the front guide hole14. Therefore, the deflection of the valve part19aat the time of valve opening operation is restrained more effectively, and the sealing ability at the time when the valve is seated to be closed can be enhanced. In addition, a smaller diameter of the first journal part21can reduce the weight of the valve assembly20.

Furthermore, the diameter D2of the valve shaft part19bis set smaller than the seal diameter D1at the time when the valve part19ais seated on the valve seat13; at the plurality of places in the circumferential direction of the sliding surface45having the diameter D3larger than the seal diameter D1, the chamfered parts45afor allowing fuel to flow are formed; and the valve assembly20is provided with the fuel passage25having at least the longitudinal hole23extending coaxially with the valve shaft part19b,the rear end of which is opened and the front end of which is closed, and the transverse holes24bleading to the longitudinal hole23at the rear from the first journal part21, in this example, the valve assembly20is provided with the fuel passage25having the longitudinal hole23and the plurality of sets of transverse holes24aand24bleading to the longitudinal hole23. Therefore, the diameter of the valve shaft part19bis decreased, and the valve assembly20is made hollow, by which the weight of the valve assembly20can further be reduced. In addition, since the fuel from the fuel passage25flows through the chamfered parts45aprovided at the plurality of places in the circumferential direction of the sliding surface45of the first journal part21, the flow of fuel near the valve seat13can be stabilized, and thereby the behavior of the valve assembly20can also be stabilized.

Although an embodiment of the present invention has been explained above, the present invention is not limited to the above-mentioned embodiment, and various design changes can be made without departing from the spirit and scope of the invention defined in the appended claims.