Electromagnetic fuel injection valve

Abstract

Provided is an electromagnetic fuel injection valve (1) that suppresses overshoot and overshoot return, and that reduces a fluid pressure acting on a valve body (6) as much as possible. In the electromagnetic fuel injection valve (1), a lift up to a valve opening position of the valve body (6) that is performed against an urging force of a return spring (7) according to excitation of a coil is achieved when overshoot and overshoot return caused at that time are set. A small pitch part (16) of the return spring (7) shows a totally compressed state when a lift amount of the valve body (6) is a first lift amount or more that is smaller than a valve opening lift amount corresponding to the valve opening position, and a large pitch part (18) acts when the lift amount is a second lift amount or more that is 1 / 2 or less of the valve opening lift amount.

Description

[Technical Field]

[0001] The present invention relates to an electromagnetic fuel injection valve that employs a hammering mechanism and is suitable for a direct injection injector. [Background technology]

[0002] Conventionally, in a direct injection injector employing a hammering mechanism, the lift of the valve disc to the valve open position is achieved by stabilizing the overshoot and overshoot return that occur during the lift (see, for example, Patent Document 1).

[0003] Specifically, in the electromagnetic fuel injection valve of Patent Document 1, when the coil is energized in the valve-closed state, the resulting magnetic force first attracts the movable core to the fixed core, compressing the auxiliary spring, which is weaker than the return spring, and then abutting against the valve-opening stopper. The movable core then moves the valve-opening stopper against the biasing force of the return spring, colliding with the fixed core and stopping. During this time, the valve disc, along with the valve-opening stopper, leaves the valve seat, establishing an open valve state.

[0004] However, when the movable core collides with the fixed core, the valve disc and the valve-opening stopper overshoot due to their inertia. As the valve-opening stopper moves away from the movable core by the amount of this overshoot, the compressive deformation of the return spring increases, causing a further overshoot return due to the repulsive force of the return spring. After the overshoot return, the valve disc is settled in the valve-open position when the movable core is pulled back again by the fixed core. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Publication No. S63-118376 Summary of the Invention [Problem to be solved by the invention]

[0006] The overshoot and overshoot return cause the valve disc to operate unstably, increasing the variation in the injected fuel flow rate. Therefore, if the overshoot and overshoot return can be reduced, the variation in the injected fuel flow rate can be suppressed. However, if the inside of the return spring is used as a fuel passage, fluid pressure is applied to the top of the valve disc, which can reduce the maximum operating fuel pressure.

[0007] In view of the problems of the prior art, an object of the present invention is to suppress overshoot and overshoot return in an electromagnetic fuel injection valve. Another object of the present invention is to reduce as much as possible the fluid pressure acting on the valve body. [Means for solving the problem]

[0008] The electromagnetic fuel injection valve of the present invention comprises: a valve housing in which a fuel injection hole and a valve seat are formed; a valve element that lifts from a valve-closed position in contact with the valve seat to a valve-open position in response to excitation of a coil, thereby enabling fuel to be injected from the fuel injection hole; a return spring that returns the valve body to the valve closing position, an electromagnetic fuel injection valve in which the lift of the valve element to the valve open position is achieved by stabilizing an overshoot and an overshoot return that occur upon the lift, The return spring is an unequal pitch coil spring having a small pitch portion and a large pitch portion, The small pitch portion exhibits a fully compressed state when the lift amount of the valve element is equal to or greater than a first lift amount that is smaller than a valve opening lift amount corresponding to the valve open position. and the end windings on both sides of the return spring are each made up of two windings so that the small pitch portion of the return spring and the large pitch portion of the return spring are connected to each other. The large pitch portion is the The lift amount The aforementioned It is characterized by its action when the valve lift is equal to or greater than the second lift amount, which is half or less of the valve opening lift amount.

[0009] In this configuration, when the coil is not energized, the valve disc is held in the closed position by the return spring. When the coil is energized, the valve disc is lifted to the open position by settling the overshoot and overshoot return that occur during the lift.

[0010] During this time, the lift of the valve disc increases, and until it reaches the first lift, the small pitch section of the return spring, which has a small spring constant, functions to quickly increase the lift. Once the lift reaches the first lift, the small pitch section becomes fully compressed and stops functioning. Also, once the lift reaches the second lift, which is less than half the opening lift, the large pitch section, which has a large spring constant, comes into play.

[0011] Therefore, by setting the first lift amount equal to or greater than the second lift amount, the small pitch portion is allowed to function until the lift amount reaches the first lift amount, and then the large pitch portion is allowed to function immediately thereafter. As a result, the large pitch portion, which has a large spring constant, suppresses an increase in the lift amount of the valve disc even before overshoot occurs. Therefore, overshoot and overshoot return can be effectively suppressed.

[0012] Furthermore, according to the present invention, when the inside of the return spring is used as a fuel passage, fuel supplied from the upstream side toward the inside of the return spring can easily flow to the outside of the return spring through the large pitch interval of the large pitch section, thereby minimizing the application of fluid pressure to the top of the valve disc and improving the maximum operating fuel pressure of the electromagnetic fuel injection valve.

[0013] In the present invention, the spring constant of the large-pitch portion may be seven times or more the spring constant of the small-pitch portion, whereby the pressing force of the large-pitch portion, which is seven times or more the pressing force of the small-pitch portion, can more effectively suppress overshoot and overshoot return, and more effectively reduce variations in flow rate.

[0014] In the present invention, the large pitch portion may be located upstream of the return spring. This allows fuel supplied from the upstream side toward the inside of the return spring to flow more quickly to the outside of the return spring through the large pitch interval of the upstream large pitch portion. This more effectively reduces the fluid pressure applied to the valve body, thereby more effectively improving the maximum operating fuel pressure of the electromagnetic fuel injection valve. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view of an electromagnetic fuel injection valve according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a part of FIG. 1 showing a state in which the valve is closed. [Figure 3] FIG. 2 is an enlarged cross-sectional view of a part of FIG. 1 in an open state. [Figure 4] 10 is a graph showing the relationship between load and deflection in a return spring with an unequal pitch. [Figure 5] 10 is a graph showing the relationship between the number of turns and the spring constant of a return spring. [Figure 6] 2 is a front view showing a specific example of a return spring used in the electromagnetic fuel injection valve of FIG. 1. FIG. [Figure 7A] 4 is a graph showing the change in the lift amount of the valve body over time when the electromagnetic fuel injection valve of FIG. 1 is in an open state. [Figure 7B] FIG. 7B is an enlarged view of a portion of the graph in FIG. 7A. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows an electromagnetic fuel injection valve according to one embodiment of the present invention. As shown in Fig. 1, this electromagnetic fuel injection valve 1 includes a valve housing 4 in which a fuel nozzle 2 (fuel injection hole) and a valve seat 3 are formed, a valve element 6 that enables fuel to be injected from the fuel nozzle hole 2 by lifting the valve element 6 from a valve-closed position in contact with the valve seat 3 to a valve-open position in response to excitation of a coil 5, and a return spring 7 that returns the valve element 6 to the valve-closed position in contact with the valve seat 3.

[0017] The valve element 6 is lifted to the valve open position by settling the overshoot and overshoot return that occur during the lift. The valve element 6 is composed of a valve portion 8 that cooperates with the valve seat 3 and a rod 9 connected to the valve portion 8.

[0018] The electromagnetic fuel injection valve 1 also includes a hollow fixed core 10 connected to the upstream end of the valve housing 4, a movable core 12 facing an attraction surface 11 of the fixed core 10 and slidably fitted on the rod 9, and a valve-opening side stopper 13 fixed to the rod 9 and abutting against the movable core 12 attracted to the attraction surface 11 when the coil 5 is energized, thereby opening the valve body 6.

[0019] Valve-closing stopper 14 is fixed to rod 9 closer to valve seat 3 than valve-opening stopper 13. An auxiliary spring 15 is provided between valve-opening stopper 13 and movable core 12. The auxiliary spring 15 exerts a spring force that moves movable core 12 away from valve-opening stopper 13 and brings it into contact with valve-closing stopper 14 when coil 5 is not energized.

[0020] Figures 2 and 3 show enlarged views of the main parts of Figure 1. Figure 2 shows the state when the valve is closed, and Figure 3 shows the state when the valve is open. As shown in Figure 2, the return spring 7 is an improper pitch spring, and has a small pitch portion 16 with a small pitch and a large pitch portion 17 with a large pitch.

[0021] The small pitch section 16 is in a fully compressed state when the lift amount of the valve body 6 is equal to or greater than a first lift amount that is smaller than the valve opening lift amount corresponding to the valve open position, and the large pitch section 17 is in operation when the lift amount is equal to or greater than a second lift amount that is equal to or less than half of the valve opening lift amount.

[0022] Figure 4 shows the relationship between load and deflection in such an unequal-pitch return spring 7. As shown by the graph curve in Figure 4, when the load applied to the return spring 7 is equal to or less than the load L1 corresponding to the first lift amount at which the small-pitch portion 16 is fully compressed, only the small-pitch portion 16, which has a small spring constant, deflects, and therefore the amount of deflection relative to changes in load is large.

[0023] If the load L2 corresponding to the second lift amount at which the large pitch section 17 functions is equal to or less than the load L1, when the load exceeds the load L1 and the small pitch section 16 is fully compressed, only the large pitch section 17, which has a large spring constant, bends, so the amount of bending relative to the change in load becomes small. Therefore, the functions of the small pitch section 16 and the large pitch section 17 can be used in a continuous manner before and after the load L1.

[0024] Figure 5 shows the relationship between the number of turns and the spring constant of the return spring. Using this relationship, the number of turns in the small pitch section 16 and the large pitch section 17 can be selected to set appropriate spring constants for the small pitch section 16 and the large pitch section 17. For example, using the relationship in Figure 5, the number of turns in the large pitch section 17 and the small pitch section 16 can be set so that the spring constant of the large pitch section 17 is seven times the spring constant of the small pitch section 16.

[0025] Figure 6 shows a more specific example of a return spring 7 configured by selecting the number of turns for the small pitch portion 16 and the large pitch portion 17 based on the relationship between the number of turns and spring constant in Figure 5. The small pitch portion 16 of this return spring 7 is configured with 7.5 turns, giving it a spring constant of 20.57 N / mm and a pitch of 0.9985. The large pitch portion 17 is configured with one turn, giving it a spring constant of 154.3 N / mm. The end turns 18 on both sides of the return spring 7 are configured with two turns. The spring constant of the large pitch portion 17 is more than seven times that of the small pitch portion.

[0026] In this configuration, when the coil 5 is not energized, the valve element 6 is seated on the valve seat 3 by the biasing force of the return spring 7, and the valve is in a closed state, as shown in Figures 1 and 2. The movable core 12 is brought into contact with the valve-closing stopper 14 by the biasing force of the auxiliary spring 15, and a predetermined gap is maintained between the movable core 12 and the fixed core 10.

[0027] When the coil 5 is energized in this state, the magnetic force generated thereby first attracts the movable core 12 to the fixed core 10, compressing the auxiliary spring 15, which is weaker than the return spring 7, and the movable core 12 comes into contact with the valve-opening stopper 13.

[0028] When movable core 12 comes into contact with valve-opening stopper 13, it quickly moves valve-opening stopper 13 against the biasing force of return spring 7, and stops when it collides with attraction surface 11. During this time, rod 9 moves together with valve-opening stopper 13, so that valve element 6 at the tip of rod 9 leaves valve seat 3, establishing an open valve state.

[0029] When movable core 12 impacts against attraction surface 11, valve element 6 and valve-opening stopper 13 overshoot due to their inertia, but the overshooting is stopped when valve-closing stopper 14, which is integrated with valve element 6, collides with movable core 12. During this time, valve-opening stopper 13 moves away from movable core 12 by an amount equal to the overshoot of valve element 6, increasing the compressive deformation of return spring 7, so that the repulsive force of return spring 7 also suppresses the overshoot of valve element 6.

[0030] When the overshoot stops, the repulsive force of return spring 7 returns valve-opening stopper 13 to a position where it abuts against movable core 12, which is in contact with attraction surface 11, thereby holding valve element 6 in the predetermined valve-open position. At this time, the biasing force of auxiliary spring 15 is smaller than the biasing force of return spring 7, which biases valve element 6 in the valve-closing direction, so auxiliary spring 15 does not interfere with the attraction of fixed core 10 to movable core 12 and the abutment of valve-opening stopper 13 against movable core 12 by return spring 7 when coil 5 is energized, and does not hinder valve element 6 from opening to the predetermined position.

[0031] In this way, during the process of opening valve disc 6, the impact force that movable core 12 imparts to attraction surface 11 is divided into the impact force when only movable core 12 first collides with attraction surface 11 and the impact force when closing-side stopper 14 subsequently collides with movable core 12, so that the energy of each collision is relatively small, preventing wear on the contact areas between attraction surface 11 and movable core 12 and keeping collision noise low. Moreover, when closing-side stopper 14 collides with movable core 12, return spring 7 is deformed more than the amount of compressive deformation that occurs during normal valve opening, so return spring 7 absorbs the collision energy of closing-side stopper 14 with movable core 12 and reduces the impact force.

[0032] When the valve element 6 opens, fuel is pressure-fed from a fuel pump (not shown) to a fuel supply tube 19. The fuel passes through the inside of a pipe-shaped retainer 20, the hollow portion 21 of the fixed core 10, the flat portion 22 around the valve-opening stopper 13, the through hole 23 of the movable core 12, the inside of the valve housing 4, and the flat portion 24 around the valve portion 8, and is then injected directly into the combustion chamber of the internal combustion engine through the fuel nozzle 2.

[0033] Next, when the power supply to the coil 5 is cut off, the repulsive force of the return spring 7 pushes the valve-opening stopper 13, which moves toward the valve seat 3 together with the movable core 12 and the valve element 6, causing the valve portion 8 to seat on the valve seat 3. At this time, the movable core 12 moves slightly later than the valve portion 8 seats on the valve seat 3, due to the influence of residual magnetism between it and the fixed core 10 and the relatively small set load of the auxiliary spring 15 that moves the movable core 12 forward.

[0034] When the valve element 6 first sits on the valve seat 3, it bounces back due to the impact of the seating. However, the movable core 12, which descends later, comes into contact with the closing stopper 14 fixed to the bouncing valve element 6, thereby minimizing the amount of bouncing back of the valve element 6.

[0035] When the rebound of the valve element 6 is suppressed, the valve element 6 is held in a closed state by the repulsive force of the return spring 7, stopping fuel injection, and the movable core 12 is held in contact with the closing side stopper 14 by the repulsive force of the auxiliary spring 15.

[0036] As described above, the impact force that the valve disc 6 exerts on the valve seat 3 during the valve closing process is divided into the impact force when only the valve disc 6 first seats on the valve seat 3 and the impact force when the movable core 12 subsequently collides with the valve-closing stopper 14, and the energy of each impact is relatively small. Furthermore, when the valve disc 6 first seats on the valve seat 3, it bounces off due to the seating impact and then seats on the valve seat 3 again, exerting an impact, but the valve closing stroke of the valve disc 6 after bouncing off is much smaller than the valve closing stroke of the valve disc 6 from the normal valve open position, so the impact force on the valve seat 3 is very small. This prevents wear on the seating areas of the valve portion 8 and the valve seat 3 and minimizes seating noise.

[0037] Figure 7A shows the change in lift amount of the valve element 6 over time when the electromagnetic fuel injection valve 1 is in the valve open state as described above. Figure 7B shows an enlarged view of the area within the square frame in Figure 7A. In Figures 7A and 7B, graph curve A shows the change in lift amount when the return spring 7 of this embodiment in Figure 6 is used. For comparison, graph curve B shows the change in lift amount when a return spring with 7.5 turns, a spring constant of 20.57 N / mm, and a uniform pitch of 1.215 is used instead of the return spring 7.

[0038] When the valve is opened, the movable core 12 collides with the valve-opening stopper 13 in response to the energization of the coil 5. As shown in Figures 7A and 7B, the movable core 12 pushes up the valve-opening stopper 13 against the biasing force of the return spring 7, increasing the lift of the valve element 6. When the movable core 12 reaches the valve-opening lift (valve-open position) at which it collides with the fixed core 10, the valve element 6 and the valve-opening stopper 13 leave the movable core 12 due to inertia and move further upstream, taking the valve-closing stopper 14 with them, entering an overshoot state.

[0039] 6 is used in this embodiment, the small pitch portion 16 of the return spring 7 is fully compressed when the movable core 12 reaches the first lift amount, which is before the valve opening lift amount L (valve open position; see FIG. 7B) at which the movable core 12 collides with the fixed core 10. Therefore, from this point onwards, the large pitch portion 17, which has a larger spring constant, comes into action, and due to its repulsive force, the rate of increase in the lift amount (see graph curve A) falls more quickly than when the above-mentioned constant-pitch return spring is used (see graph curve B).

[0040] As a result, when the return spring 7 of this embodiment shown in FIG. 6 is used, as shown by the graph curve A, overshoot and overshoot return are more effectively suppressed than when the return spring with the equal pitch shown by the graph curve B is used, and the valve opening lift amount L (valve opening position) is quickly settled.

[0041] As described above, according to this embodiment, the large pitch portion 17 effectively suppresses overshoot and overshoot return when the valve is opened, thereby stabilizing the operation of the valve body 6 and reducing variations in the flow rate.

[0042] Furthermore, since the fuel supplied from the upstream side toward the inside of the return spring 7 easily flows to the outside of the return spring 7 through the large pitch interval of the large pitch portion 17, it is possible to avoid as much as possible the application of fluid pressure to the top of the valve body 6, thereby improving the maximum operating fuel pressure of the electromagnetic fuel injection valve 1.

[0043] Furthermore, since the spring constant of the large pitch section 17 is more than seven times that of the small pitch section 16, the appropriate pressing force of the large pitch section 17 can more effectively suppress overshoot and overshoot return, and further effectively reduce the variation in flow rate.

[0044] Furthermore, since the large pitch portion 17 is provided on the upstream side of the return spring 7, the fuel supplied to the inside of the return spring 7 can be more quickly circulated to the outside of the return spring 7. This makes it possible to more effectively reduce the fluid pressure applied to the valve body 6 and more effectively improve the maximum operating fuel pressure of the electromagnetic fuel injection valve 1.

[0045] Although the embodiment of the present invention has been described above, the present invention is not limited to this. For example, in this embodiment, when lifting the valve element 6, a hammering mechanism is employed in which the movable core 12 is caused to collide with the valve-opening stopper 13 against the biasing force of the auxiliary spring 15 (hammering), and then the valve element 6 together with the valve-opening stopper 13 is pushed up to the valve-opening side against the biasing force of the return spring 7. However, instead of this, hammering may be omitted and the valve element 6 may be directly pushed up to the valve-opening side by the movable core 12 against the biasing force of the return spring 7. [Explanation of symbols]

[0046] 1...electromagnetic fuel injection valve, 2...fuel nozzle, 3...valve seat, 4...valve housing, 5...coil, 6...valve body, 7...return spring, 8...valve portion, 9...rod, 10...fixed core, 11...suction surface, 12...movable core, 13...valve opening side stopper, 14...valve closing side stopper, 15...auxiliary spring, 16...small pitch portion, 17...large pitch portion, 18...end turn, 19...fuel supply tube, 20...retainer, 21...hollow portion, 22...flat portion, 23...through hole, 24...flat portion, A, B...graph curves.

Claims

1. a valve housing in which a fuel injection hole and a valve seat are formed; a valve body that lifts from a valve-closing position in contact with the valve seat to a valve-opening position in response to excitation of a coil, thereby enabling fuel to be injected from the fuel injection hole; a return spring that returns the valve body to the valve closing position, an electromagnetic fuel injection valve in which the lift of the valve element to the valve open position is achieved by stabilizing an overshoot and an overshoot return that occur upon the lift, The return spring is an unequal pitch coil spring having a small pitch portion and a large pitch portion, the small pitch portion is wound multiple times and assumes a fully compressed state when the lift amount of the valve body is equal to or greater than a first lift amount that is smaller than the valve opening lift amount corresponding to the valve open position, the return spring has two end turns so that the small pitch portion with multiple turns and the large pitch portion with one turn are connected to each other, and the large pitch portion acts when the lift amount is equal to or greater than a second lift amount that is equal to or less than half of the valve opening lift amount.

2. 2. The electromagnetic fuel injection valve according to claim 1, wherein the spring constant of the large pitch portion is seven times or more the spring constant of the small pitch portion.

3. 2. The electromagnetic fuel injection valve according to claim 1, wherein the large pitch portion is located upstream of the return spring.

Images