JP2765185B2 - Fuel injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a fuel injection device for injecting and supplying high-pressure fuel to a diesel engine.

[Prior art]

Conventionally, as disclosed in JP-A-59-165858, "Electromagnetic Control Injection System for Diesel Engine", high-pressure fuel is stored in a kind of surge tank called a common rail, and this is stored in an injection valve. 2. Description of the Related Art A common rail fuel injection device that injects fuel into a diesel engine by opening and closing the fuel injection device is known. Then, at the end of fuel injection, the fuel injection device instantaneously flows high-pressure fuel into the control chamber (control cavity), thereby obtaining good injection cutoff.

[Problems to be solved by the invention]

However, in the above-described configuration, due to the instantaneous inflow of high-pressure fuel and the subsequent pressure pulsation, the nozzle sheet impact load (hereinafter referred to as “impact load”), which is the impact load applied to the nozzle seat at the end of injection, is extremely high. There was a problem of becoming. In addition, a nozzle having sufficient strength against such a high impact load generally has to increase the space inside the injection hole at the tip (hereinafter referred to as "suck volume"). Since the fuel in the sack volume is located downstream of the nozzle seat, the fuel flows into the combustion chamber even when the nozzle is closed (that is, during non-injection). Therefore, when the sack volume is excessive, the fuel remaining in the sack volume after the explosion is drowned out, and the HC emission is deteriorated, and there is a problem from the viewpoint of exhaust emission purification. The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a fuel injection device capable of reducing an impact load at the end of fuel injection and reducing a suck volume at a nozzle tip. It is to be.

[Means for Solving the Problems]

The configuration of the invention for solving the above-mentioned problem is to control the pressure of the control chamber that holds the back pressure acting on the nozzle needle that opens and closes the injection hole to be switched between the high pressure side and the low pressure side by the switching valve, and In a fuel injection device, high-pressure fuel flows into and out of a control chamber through a one-way orifice provided between the control chamber and acting as a throttle only for outflow from the control chamber. In the high-pressure supply path leading to the high-pressure supply path upstream of the switching valve connecting the control chamber and the low-pressure side path, and another orifice was formed in series with the one-way orifice. Features.

[Action]

When high-pressure fuel is supplied to the control chamber, the high-pressure fuel flows to the control chamber via the valve contact on the high-pressure side of the switching valve, the orifice, and the one-way orifice. In this state, the injection holes are closed and no fuel is injected. At this time,
One-way orifices do not function as orifices.
Next, when the switching valve is switched to the low pressure side, the high pressure fuel in the control chamber flows to the low pressure side path via the one-way orifice and the valve contact on the low pressure side of the switching valve. As a result, the pressure in the control chamber becomes lower than the high-pressure fuel, the nozzle needle moves in the valve opening direction, and the high-pressure fuel is injected from the injection port. At this time, the pressure in the control chamber falls relatively smoothly due to the function of the one-way orifice. Next, when the switching valve is switched to the high-pressure side, as described above, high-pressure fuel is introduced into the control chamber. However, since the high-pressure fuel passes through the newly provided orifice, the pressure rise in the control chamber is compared by the function. It is performed loosely and smoothly. As a result, the moving speed of the nozzle needle decreases, and the impact load on the valve seat decreases. Moreover, the excessive flow of the high-pressure fuel into the control chamber at the end of the injection and the subsequent pressure pulsation are alleviated by the orifice.

【Example】

Hereinafter, the present invention will be described based on specific examples. FIG. 1 is a longitudinal sectional view showing a fuel injection device according to the present invention. The fuel injection device 1 is used by being inserted into a cylinder head of a diesel engine (not shown). The fuel injection device 1 mainly includes a valve body 10 in which a coil 11 and an armature 12 are disposed above, a one-way orifice 22 and a control chamber 23 in the center below the valve body 10, and a high-pressure fuel inlet 21 on the side. And a nozzle body 30 in which a nozzle unit 31 is disposed in the center below the main body 20. The valve body 10 has a port, and an inner valve 14 which is a free piston is provided at the center thereof, and an outer valve 13 which is integrally fixed to an armature 12 which moves up and down by the electromagnetic force of the coil 11 is provided on a peripheral surface thereof. And a three-way fitting to form a three-way solenoid valve. FIG. 2 is a partially enlarged longitudinal sectional view showing an orifice 131, which will be described later, formed at the lower end of the outer valve 13, which is the portion A in FIG. FIG. 3 is a partially enlarged longitudinal sectional view showing the one-way orifice 22 and the control chamber 23, which are part B of FIG. FIG. 4 is a partially enlarged longitudinal sectional view showing a tip end portion of a nozzle body 30 which is a portion C in FIG. Next, a series of operations of the above-described embodiment device will be described with reference to the timing chart of FIG. First, when the control pulse is off (non-energized), the outer valve 13 is urged downward by the spring 15, and the lower end of the outer valve 13, that is, the valve contact connected to the low-pressure side path is in contact with the valve body 10. . At this time, the high-pressure fuel introduced from the high-pressure fuel inlet 21 passes through a radial hole provided on the side surface of the outer valve 13 from the port.
The vehicle enters the outer valve 13 through 132. Then, when the inner valve 14 is pushed up, the ports communicate with each other. As a result, the high-pressure fuel enters the control chamber 23 and presses the nozzle needle 31 via the command piston 24 and the pin 25 toward the seat 32 which is a contact portion between the nozzle body 30 and the nozzle needle 31. That is, the high-pressure fuel is not injected from the injection hole 33 at the tip of the nozzle body 30. Next, when the control pulse is turned on (energized), the armature 12 is pulled up against the spring 15 by the electromagnetic force of the coil 11. Then, the outer valve 13 integrated with the armature 12 is also lifted upward to reach the ascending position of the inner valve 14, thereby interrupting the communication between the ports. The radial contact 132 formed in the outer valve 13, the inner peripheral surface of the cylinder of the valve body 10, the port (opening) and the outer peripheral surface of the outer valve 13 constitute a valve contact. That is, high-pressure fuel on the port side is prevented from flowing into the port side, and high-pressure is not applied to the control chamber 23. or,
As the outer valve 13 moves up, the ports communicate with each other. Here, the port is a low-pressure side path, and fuel is returned to a fuel tank (not shown) through the port. As a result, the high-pressure fuel in the control chamber 23 flows out to the low-pressure side of the port. Accordingly, the nozzle needle 31 rises due to the difference in oil pressure, and when the seat 32 opens, the high-pressure fuel introduced from the high-pressure fuel inlet 21 passes through a passage extending below the main body 20 and is injected from the injection hole 33 at the tip of the nozzle body 30. Is done. Next, at the end of injection, the control pulse is turned off (de-energized)
Thus, the electromagnetic force of the coil 11 disappears, and the outer valve 13 returns to the initial state again. That is, the ports are communicated with each other. As a result, high-pressure fuel flows again from the port, and high pressure is applied to the control chamber 23 through the port, so that the nozzle needle 31 moves the command piston 24 and the pin 25 in the same manner as described above.
The sheet 32 is pushed downward through the sheet, and the sheet 32 is closed. The inventors have conducted intensive experimental research to reduce the impact load on the seat 32 at the end of the above-described injection, and as a result, it is only necessary to mitigate the excessive inflow of high-pressure fuel into the control chamber 23 and the subsequent pressure pulsation. I came to the conclusion. An orifice different from the conventional one-way orifice 22 is further provided in a high-pressure fuel passage communicating from the high-pressure fuel inlet 21 to the control chamber 23 through the port. Specifically, as shown in a partially enlarged longitudinal sectional view in FIG. 2, another orifice is provided at the passage outlet to the port of the outer valve 13 so as to prevent the instantaneous inflow of high-pressure fuel into the control chamber 23. A squeezed orifice 131 was provided. Then, as shown in FIG. 5, after the control pulse was turned off, the control chamber pressure was suppressed to a small change from the conventional large change indicated by the broken line. As a result, the bounce in the needle lift was reduced, and the impact load (nozzle sheet impact load) was suppressed as shown by the solid line. Accordingly, the sheet thickness t of the sheet 32 of the nozzle body 30 can be suppressed, and the increase in the suck volume 34 can be suppressed. As another embodiment, a one-way orifice disposed in a passage extending from a port below the outer valve 13 to the control chamber 23 as shown in FIG. The orifice 161 is screwed or integrated into the valve body 10 above the valve body 10 in the passage of the throttle member 16.
Was provided. As a result of the experimental research, as shown in FIG. 7, the orifice diameters of the orifices 131 and 161 were not less than φ0.5 mm in order not to affect the descending speed of the nozzle needle 31 and the injection amount. ) Is equal to or less than the level of the conventional row type high pressure injection nozzle, it has been found that the diameter should be 0.6 mm or less.

【The invention's effect】

The present invention provides another high-pressure supply path in series with a one-way orifice in a high-pressure supply path leading to a control chamber and in an upstream high-pressure supply path before reaching a valve contact of a switching valve connecting the control chamber and the low-pressure side path. An orifice is formed. When the switching valve is switched to the high-pressure side, as described above, high-pressure fuel is introduced into the control chamber. However, since the high-pressure fuel passes through the newly provided orifice, the pressure rise in the control chamber is relatively gentle due to its function. Done in This allows
The moving speed of the nozzle needle is reduced, and the excessive inflow of high-pressure fuel into the control chamber and the subsequent pressure pulsation at the end of injection are alleviated, and the impact load is alleviated. That is, the fuel injection device according to the present invention can suppress an increase in the sheet thickness at the tip of the nozzle and suppress an increase in the suck volume at the tip of the nozzle, and thus have the effect of preventing HC emission deterioration.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a fuel injection device according to a specific embodiment of the present invention. FIG. 2 is a partially enlarged longitudinal sectional view of a portion A in FIG. FIG. 3 is a partially enlarged longitudinal sectional view of a portion B in FIG. FIG. 4 is a partially enlarged longitudinal sectional view of a portion C in FIG. FIG. 5 is a timing chart in a series of operations of the apparatus of the embodiment. FIG. 6 is a partial longitudinal sectional view showing another embodiment in which an orifice is formed in a portion B in FIG. FIG. 7 is an explanatory diagram showing the nozzle needle descent time, injection amount, and nozzle sheet impact load with respect to the orifice diameter. 1 ... fuel injection device, 10 ... valve body 11 ... coil, 12 ... armature 13 ... outer valve, 131 ... orifice 14 ... inner valve, 15 ... spring 20 ... main body, 21 ... high-pressure fuel Inlet 22 ... One-way orifice, 23 ... Control room 30 ... Nozzle body, 31 ... Nozzle needle 32 ... Seat, 33 ... Injection hole 34 ... Sac volume

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-143377 (JP, A) JP-A-59-165858 (JP, A) JP-A-64-36971 (JP, A) JP-A-2- 146255 (JP, A) Japanese Utility Model 2-1465 (JP, U) Japanese Utility Model 1-158553 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02M 47/00-47 / 06 F02M 51/00 F02M 51/06 F02M 61/08

Claims (1)

(57) [Claims] 1. A control valve for controlling a pressure of a control chamber for maintaining a back pressure acting on a nozzle needle for opening and closing an injection hole between a high-pressure side and a low-pressure side by a switching valve, and between the switching valve and the control chamber. A high-pressure fuel flowing into and out of the control chamber through a one-way orifice that acts as a throttle only for outflow from the control chamber. Another orifice is formed in series with the one-way orifice in the high-pressure supply passage, and in the upstream high-pressure supply passage before reaching the valve contact of the switching valve that connects the control chamber and the low-pressure passage. Characteristic fuel injection device.