Patent Publication Number: US-2003234054-A1

Title: Electromagnetic valve

Description:
[0001] The present application is based on and claims priority under 35 U.S.C § 119 with respect to Japanese Patent application No. 2002-122751 filed on Apr. 24, 2002, the entire content of which is incorporated herein by reference. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present Invention relates to an electromagnetic valve.  
       BACKGROUND OF THE INVENTION  
       [0003] A conventional electromagnetic valve of this kind is disclosed, for example, in Japanese laid-open Publications No. 10-122404 or No. 11-166641. This valve includes a plunger driven by an electromagnetic mechanism, a spool moved by the plunger in the axial direction, a valve body in which fluid passages are formed and a sleeve in which the spool is accommodated and which is fitted into the valve body. In the electromagnetic valve disclosed in the former publication, a pushing member is pressed into the plunger and is contacted with a spherical portion which is formed on one end of the spool. Thereby, the spool is moved in the axial direction of the valve body in response to the movement of the plunger. On the other hand, in the electromagnetic valve disclosed in the latter publication, a spherical portion is formed on one end of a pushing member which is pressed into the plunger and is contacted with one end of the spool so that the spool is moved in the axial direction of the valve body. In these valves, the declination and the inclination of the axial centers of the pushing member and the spool is absorbed by the spherical portion.  
       [0004] In the above valves, however, since it is necessary to form the spherical portion on one end of the pushing member or one end of the spool by process, the manufacturing cost of the valve is increased. Further, since it is necessary to form the pushing member and the spool by a material having superior wear resistance and impact-resistance, the manufacturing cost of the valve is further increased.  
       SUMMARY OF THE INVENTION  
       [0005] It is, therefore, a principal object of the present invention to provide an improved electromagnetic valve which overcomes the above drawbacks.  
       [0006] In order to attain the foregoing object, the present invention provides an electromagnetic valve which includes a plunger driven by an electromagnetic mechanism, a tubular spool moved by the plunger in the axial direction, a valve body having fluid passages, a sleeve accommodating the spool therein so as to be able to slide in the axial direction and fitted into the valve body, a ball member pressed into one end of the spool and a pushing member fixed to the plunger and contacted with the ball member. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0007] The above object, features and advantages of the present invention will be more apparent and more readily appreciated from the following detailed description of a preferred exemplary embodiment of the present invention, taken in connection with the accompanying drawing, in which;  
     [0008]FIG. 1 is a cross sectional view of an electromagnetic valve according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PRESENT INVENTION  
     [0009] Referring to FIG. 1, an electromagnetic valve  10  is a linear type electromagnetic valve and is used to control the pressure or the flow rate of the fluid which is used for controlling a subject of the control such as, for example, a variable valve timing control device (VVT) or a vehicular automatic transmission and so on.  
     [0010] The electromagnetic valve  10  includes an electromagnetic mechanism  1  which is controlled by duty signal from electric control unit (not shown), a spool  3  which is moved by the electromagnetic mechanism  1  and a cylindrical sleeve  2  in which the spool  3  is disposed so as to be able to slide in the axial direction. The electromagnetic valve  10  is fitted into a hole Po which is formed on a cylinder block  8  of an engine and is fixed to the cylinder block by a screw  9   a  through a bracket  4 . The cylinder block  8  corresponds to a valve body of the present invention.  
     [0011] Fluid pressure from a fluid pressure source P Is supplied to the electromagnetic valve  10  through a fluid passage P 1  of the cylinder block  8 . Further, the electromagnetic valve  10  supplied the fluid pressure to the VVT through fluid passages P 2 , P 3  formed on the cylinder block  8  and discharges the fluid pressure to an oil pan Q through a fluid passage DR.  
     [0012] The electromagnetic mechanism  1  includes a front yoke member  12  which has an approximately cylindrical shape and which is made of magnetic material, a rear yoke member  13  which has an approximately cylindrical shape and which is made of magnetic material, a cylindrical bobbin which is made of resin, a coil  14  which is wound on the bobbin, a case  15  which is made of magnetic material, a plunger  16  which is made of magnetic material and which is movable in the axial direction by electromagnetic force, a connector  17  and so on.  
     [0013] A cylindrical concave portion  16   a  is formed on one end of the plunger  16  and a pushing member  18  is pressed into the concave portion  16   a.  The case  15  is snugly fitted on the outer circumference of the front yoke  12 . Thereby, it is prevented that water comes in the electromagnetic mechanism  1  from outside. Further, it is prevented that the fluid leaks from inside of the electromagnetic mechanism  1 .  
     [0014] The electromagnetic mechanism  1  is pressed into the right end  2   b  of the sleeve  2  through a projecting portion  12   g  of the front yoke  12 . Thereby, the end surface  2   c  of the right end  2   b  of the sleeve  2  is contacted with a stepped portion  12   f  of the front yoke  12 . As a result, it is prevented that water comes in the electromagnetic mechanism  1  from outside. Further, it is prevented that the fluid leaks from inside of the electromagnetic mechanism  1 .  
     [0015] The spool  3  has an approximately cylindrical shape. A penetrating passage  3   b  which is used as a drain passage is formed in the spool  3 . Further, radial passages  3   c,    3   d  are formed so as to communicate between the penetrating passage  3   b  and the outer circumference of the spool  3 . A circular grooves  3   e  is formed on the outer circumference of the spool  3 . A ball member  11  is pressed into an opening of the penetrating passage  3   b  of one end side of the spool  3  which is opposite to the electromagnetic mechanism  1  and is always contacted with one end of the pushing member  18 . The ball member  11  is a ball of all-purpose ball bearing and has superior wear resistance and impact-resistance.  
     [0016] The inner diameter of the penetrating passage  3   b  is constant in the axial direction and is the same as the inner diameter of the opening thereof into which the ball member  11  is pressed. The inner diameter of the opening thereof into which the ball member  11  is pressed may be larger than the inner diameter of the penetrating passage  3   b.  Thereby, it is able to form the penetrating passage  3   b  without changing the inner diameter in the axial direction and therefore tubular material can be used to the spool  3 . Further, it is not necessary to form the spool  3  by material having superior wear resistance and impact-resistance. Accordingly, the manufacturing cost of the electromagnetic valve can be reduced.  
     [0017] A spring  6  is interposed between the sleeve  2  and the spool  3 . One end of the spring  6  contacts with a stepped portion  2   e  of the sleeve  2  and the other end of the spring  6  contacts with a stepped portion  3   a  of the spool  3 . Thereby, the spool  3  is always urged toward the electromagnetic mechanism  1  and the ball member  11  is always contacted with the pushing member  18 .  
     [0018] First radial port  2   f  are formed on the sleeve  2  so as to penetrate in the radial direction. Second radial ports  2   j  and third radial ports  2   k  are formed on the sleeve  2  so as to penetrate in the radial direction, respectively. The second and third radial ports  2   j,    2   k  are located at both side of the first radial ports  2   f  in the axial direction of the sleeve  2 . Further, a fourth port  2   n  is formed on the left end of the sleeve  2  so as to open in the axial direction. An outer circular groove  2   a  is formed on the outer circumference of the sleeve  2  and a seal ring is fitted in the groove  2   a.    
     [0019] When the electromagnetic valve is not operated, the spool  3  is urged toward the electromagnetic mechanism  1  by the spring  6  and the spool  3  is in the condition shown in FIG. 1. Therefore, the fluid passage P 1  is communicated to fluid passage P 2  through the first radial ports  2   f,  the circular groove  3   e  and the radial second ports  2   j.  Thereby, the fluid pressure from the fluid pressure source P is supplied to VVT. Further, the fluid returned from the VVT is discharged to the oil pan Q through the fluid passage P 3 , the third radial ports  2   k,  the radial passage  3   c,  the penetrating passage  3   b,  the forth port  2   m  and the drain passage DR.  
     [0020] When the duty signal is supplied to the electromagnetic mechanism  1  and the electromagnetic valve  10  is operated, the plunger  16  is moved toward the spool  3  by the magnetic force. Then, the pushing member  18  pushes the spool  3  through the ball member  11  and the spool  3  Is moved leftward against the urging force of the spring  6 . When the spool  3  is moved leftward, the rand portions  3   f,    3   g  close the second radial ports  2   j  and the third radial ports  2   k,  respectively and the fluid supply to VVT is interrupted.  
     [0021] When the duty ratio of the duty signal supplied to the electromagnetic mechanism  1  is further increased, the spool  3  contacts with the left end portion  2   e  of the sleeve  2  and the movement of the spool  3  stops. At this time, the communication between the fluid passage P 1  and the second radial ports  2   i  is interrupted and the communication between the fluid passage P 1  and the fluid passage P 3  through the circular groove  3   e  and the second radial ports  2   k  is established. Thereby, the fluid pressure from the fluid pressure source P is supplied to VVT. Further, the fluid returned from the VVT is discharged to the oil pan Q through the fluid passage P 2 , the radial passage  3   d,  the penetrating passage  3   b,  the fourth radial ports  2   m  and the drain passage DR.  
     [0022] The invention has thus been shown and described with reference to a specific embodiment, however, it should be understood that the invention is in no way limited to the details of the illustrates structures but changes and modifications may be made without departing from the scope of the appended claims.