JPH0417809Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection nozzle for injecting fuel into a combustion chamber of an internal combustion engine, and particularly to an injection nozzle that performs injection by lift operation of a needle valve.

Internal combustion engines, particularly diesel engines, use injection nozzles capable of injecting high-pressure fuel because it is necessary to inject fuel into a high-pressure combustion chamber. This injection nozzle is equipped with a needle valve that opens and closes its nozzle, and performs fuel injection at an injection rate that corresponds to the lift amount of the needle valve. In this case, the needle valve has a step formed in its center,
The needle valve lift operation is performed by the difference between the valve opening force due to the high pressure fuel applied thereto and the valve closing force of the pressure spring, and the fuel injection pattern is determined by these setting conditions. That is, when lifting the needle valve with a relatively low hydraulic pressure, the pressure receiving surface of the stepped portion of the needle valve that receives the valve-opening force is made large, or the elastic force of the pressure spring is set to be relatively small. However, with this, the lift amount of the needle valve becomes relatively large, making the opening and closing operation of the needle valve unstable during high-speed rotation.
Due to the delay in the valve closing operation, the fuel becomes difficult to run out. On the other hand, if the elastic force of the pressure spring is increased or the stepped portion of the needle valve is made relatively small in order to improve fuel depletion, the opening of the needle valve will be delayed, and the amount of fuel injected will be reduced, especially at low speeds. There is a disadvantage that it is easy to decrease. In this way, there is a relative relationship between the valve closing force and the valve opening force, so the operating characteristics of conventional injection nozzles are almost constant due to the pressure spring and the shape of the pressure receiving surface of the stepped part of the needle valve. They tend to be regulated by patterns.

An object of the present invention is to provide an injection nozzle that can easily change the relative relationship between the valve-opening force and the valve-closing force to a desired value to improve the operating characteristics of the on-off valve.

In the injection nozzle according to the present invention, when a valve opening force due to the high pressure fuel in the liquid reservoir chamber is applied to the needle valve in the nozzle base frame, the valve opening force from the high pressure fuel in the liquid reservoir chamber is greater than the valve closing force due to the pressure spring. The needle valve center is located within the nozzle base frame between the push rod attached to the lower end of the pressure spring to support the pressure spring and the upper end of the needle valve. A pair of control cams are pivotally mounted at equal distances apart from the line to the left and right, and the pair of control cams rotate about respective rotation center lines that are perpendicular to the needle valve center line when viewed from the side, and the push rod comes into contact with the control cams. A rod-side contact surface and a needle-valve-side contact surface with which the needle valve contacts are respectively formed, and a cross section between the rod-side contact surface and the needle valve-side contact surface of each of the control cams is formed in a wedge shape. , the pair of control cams receiving the valve opening force from the needle valve on the needle valve side contact surface are configured to lift the push rod by a larger amount than the needle valve lift amount by the rod side contact surface; It is characterized by

The present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an injection nozzle 1 as an embodiment of the present invention. This injection nozzle 1 is attached to each cylinder of a diesel engine (not shown), and each cylinder is connected to an injection pump 2 via an injection pipe 3. In FIG. 1, reference numeral 4 indicates an overflow pipe, which is connected to the fuel tank 5. The injection nozzle 1 has a nozzle base frame, which is formed by a nozzle holder body 6 and a nozzle body 8 integrally connected to the nozzle holder body 6 via a retaining nut 7. The nozzle holder body 6 is formed with a communication path 10 that guides the fuel from the injection pipe 3 to a liquid reservoir chamber 9 (see FIG. 2) on the nozzle body 8 side. On the other hand, as shown in FIG. 2, the nozzle body 8 has a sliding hole 11 formed in its center, into which a needle valve 12 is inserted. The lower end of this needle valve is formed to open and close the nozzle 13 at the tip of the nozzle body 8. The needle valve 12 is formed with a stepped portion at its center, and there is a pressure receiving surface 12 that receives the hydraulic pressure of the fuel in the liquid reservoir chamber 9 and lifts the needle valve 12 in the opening direction A.
1 is formed. The upper end 122 of the needle valve 12 projects into the central hole 14 of the nozzle holder body 6,
Furthermore, it is in contact with a pair of control cams 15. Note that the flow passes through the gap between the needle valve 12 and the sliding hole 11, flows into the center hole 14, and flows into the overflow pipe 4.
An overflow pipe system is formed following the injection pump 2, and leaks the fuel sent from the injection pump 2 side in an amount larger than the injection amount.

As shown in FIG. 3, each control cam 15 has a cylindrical shape, and a pair of contact surfaces 151 and 152 are formed at the center of the control cam 15, which are opposite to each other. Here, the cross section between the pair of contact surfaces is wedge-shaped as shown in FIG. Furthermore, both ends thereof are formed as cylindrical parts 153, which are rotatably fitted into the receiving holes 601 of the nozzle holder body 6. The rotational center line l of each control cam 15 is located perpendicular to the paper plane in FIGS. 1 and 2, and is separated from the center line _l1 of the needle valve by a predetermined distance.
And they are orthogonal to each other (in side view). The pair of contact surfaces 151 and 152 are connected to the upper end portion 122 of the needle valve.
and the pressure rod 17 on the side of the pressure spring (hereinafter simply referred to as spring) 16,
It is compressed by these. The upper end of the spring 16 contacts the lower end of the adjusting screw 18, thereby setting a predetermined initial load. The needle valve 12 and the control cam 15 shown in FIG.
1,152 are in a state of being opposite to the lower and upper directions at the same inclination angle with respect to the plane containing the rotation center line l.
Here, the point of action P ₁ between the upper end portion 122 and the contact surface 151 and the point of action P ₂ between the push rod 17 and the contact surface 152 are both distances from the center point P.
They are formed so that L ₁ is the same.

The operation of the injection nozzle 1 shown in FIG. 1 will be explained. When high-pressure fuel is supplied from the injection pump 2 to the liquid reservoir chamber 9, the pressure receiving surface 121 receives the liquid pressure. The valve opening force received by this pressure receiving surface is applied to the point of action P ₁ of the control cam 15, while the valve closing force of the spring 16 is applied to the point of action P ₂ . At this time, control cam 1
A moment in the valve-closing direction and a moment in the valve-opening direction are applied to 5, but if the moment in the valve-opening direction increases further after the moment in the valve-closing direction and the moment in the valve-opening direction match, the control cam 15 rotates in the valve-opening direction. The maximum rotation amount θ _M is angularly varied (see Fig. 4). In this _case , as shown in _FIG .
As the lift amount of the needle valve 12 changes, one of the twisting distances (L ₁ ) becomes shorter (L ₂ ) and the other becomes longer (L ₃ ). Moreover, at this time, for the needle valve lift amount H ₁ ,
Spring 16 for a lift amount _H2 larger than this
side is displaced.

In this way, as shown in FIG. 6, the injection nozzle 1 has a displacement amount H 2 of the spring (indicated by a broken line) that is smaller than the lift amount H ₁ (indicated by a solid line) of the needle valve ₁₂ .
It is configured to increase in proportion to the rotational angular displacement of the control cam 15. In particular, the control cam 15 lifts the push rod 17 more as the needle valve lift amount increases, that is, suppresses the amplification effect of the compression amount of the pressure spring at the needle valve lift start position side, and maximizes the needle valve lift. The amplification effect of the amount of compression on the position side can be increased. Therefore, the needle valve 12 can be opened with a relatively low opening force, preventing a decrease in the fuel injection amount at low rotation speeds, and furthermore, the needle valve lift amount can be relatively small, so at high rotation speeds, the needle valve 12 can be opened with a relatively low opening force. This prevents a delay in the valve closing operation due to instability in the opening and closing operation of the needle valve, thereby preventing worsening of fuel shortage.

The injection nozzle 1 in Fig. 1 is the angle control cam 1.
Although the inclination angle α (see FIG. 3) of the pair of contact surfaces 151 and 152 in No. 5 was the same, they may be made different.

Furthermore, as shown in FIG.
7a is formed into a stepped shape, and a pair of control cams 1
5a and each point of action P ₂ after changing the specified rotation angle.
It is also possible to measure the sudden increase in the moment in the valve closing direction by making a stepwise change to the P ₂ a side. This is because the spring displacement amount as a lift amount increases rapidly as shown by the dashed line in FIG. 6, and as a result, a higher valve closing force can be obtained compared to the valve opening force.

[Brief explanation of the drawing]

FIG. 1 is a cutaway sectional view of a main part of an injection nozzle as an embodiment of the present invention, FIG. 2 is an enlarged sectional view of a main part of the same injection nozzle, FIG. Fig. 4 is an explanatory diagram of the operation of the above injection nozzle, Fig. 5 is a characteristic diagram of the control cam of the above injection nozzle, Fig. 6 is a lift amount diagram of the needle valve and spring of the above injection nozzle, and Fig. 7 is a diagram of the present invention. FIG. 7 shows a push rod side view of an injection nozzle according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Injection nozzle, 6... Nozzle holder body, 8... Nozzle holder, 9... Liquid reservoir chamber, 12
... Needle valve, 13 ... Nozzle, 15 ... Control cam, 16 ... Spring, 151, 152 ...
Contact surface, l ₁ ...Center line, 17...Push rod.

Claims (1)

[Scope of utility model registration request] In an injection nozzle that injects fuel from the nozzle at the tip of the nozzle base frame, when a valve opening force due to the high pressure fuel in the liquid reservoir chamber is applied to the needle valve in the nozzle base frame, the valve opening force is greater than the valve closing force due to the pressure spring. A push rod attached to the lower end of the pressure spring to support the pressure spring and the upper end of the needle valve are located within the nozzle base frame at an equal distance from the center line of the needle valve to the left and right. A pair of control cams are pivotally connected to each other, and the pair of control cams rotate about respective rotation center lines perpendicular to the needle valve center line when viewed from the side, and the needle and the rod-side abutment surface that the push rod comes into contact with are connected to each other. A contact surface on the needle valve side that the valve comes into contact with is formed respectively,
The cross section between the rod side abutting surface and the needle valve side abutting surface of each of the control cams is formed in a wedge shape,
The pair of control cams, which receive the valve opening force from the needle valve on the needle valve side contact surface, are configured to lift the push rod more as the needle valve lift amount increases by the rod side contact surface. The injection nozzle is characterized by: