JPH0452467Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a unit injector.

[Prior Art] As is well known, the unit injector A is constructed by integrating the plunger portion of an injection pump and an injection nozzle as shown in FIG. 4, and is mounted on the cylinder head 1. and plunger (Fig. 1)
The lift movement of 22 is driven from the camshaft 2 via the rocker arm 3 in the same way as the intake and exhaust valves (not shown), and fuel is supplied by a feed pump (not shown) attached to the engine body. Since this unit injector does not have a high-pressure injection pipe, it is particularly effective in improving injection characteristics at high pressure and high speed, as shown by the solid line in FIG. Note that the chain line represents the injection characteristics of a conventional injection pump and injection nozzle.

However, as can be seen from FIG. 5, the injection pressure is low at low speeds and high at high speeds. Therefore, as shown by the dashed line, if we increase the injection pressure at low speeds to improve fuel atomization and improve combustion and smoke, the injection pressure will become excessive at high speeds.
Excessive pressure acts on the oil passage inside the injector, reducing the durability of the injector. Incidentally, such a unit injector is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-72867.
It is stated in the No.

Furthermore, in the injector described in JP-A-60-13972, fuel injection is performed in two parts: pilot injection and main injection, which has a negative effect on fuel consumption and smoke generation. arise.

[Problem to be solved] Therefore, the purpose of the present invention is to increase injection pressure at low speeds and suppress excessive injection pressure at high speeds, thereby improving fuel consumption and smoke generation. The goal is to provide a unit injector that can

[Means for Solving the Problems] The unit injector according to the present invention includes a relief valve 4 in the oil passage 32 pressurized by the plunger 22 of the pump section 20 of the unit injector 10.
A branch portion 34 leading to 0 is provided, and the relief valve 40
is provided with a needle valve 43 seated on a seat surface 42 of a lower body 41, and between a seat 44 in contact with the upper end of the needle valve 43 and an adjusting screw 46 screwed into a threaded portion of the upper body 45. A spring 47 that adjusts the opening pressure of the relief valve 40 is tensioned, and the lower body 41 has an annular chamber 48 surrounding the small diameter portion 43a of the needle valve 43 and an annular chamber 48 formed between the lower body 41 and the pump body 28. An orifice 50 is provided that communicates the chamber 49, and the annular chamber 49 is connected to a fuel supply passage.

[Description of effects] At high speed, when the injection pressure reaches the valve opening pressure set by the spring 47 of the relief valve 40,
The hydraulic pressure acting on the needle valve 43 from the oil passage 32 is
The needle valve 43 is pushed up against the spring 47 to open it. This allows the pressure oil to flow through orifice 5.
However, due to the resistance of the orifice 50, the oil pressure rises smoothly without dropping too rapidly, and the maximum pressure is kept at a suitable value. Therefore, oil path 3
No excessive pressure acts on 2 and 14, and as a result,
The durability of the unit injector is improved. Note that at low speeds, it functions in the same manner as before.

In this way, according to the present invention, the injection pressure is increased at low speeds to improve combustion and smoke, and at high speeds, the oil in the high pressure oil passage is released from the relief passage to the fuel supply passage via the relief valve and orifice, thereby increasing the pressure. This can reduce excessive injection pressure and improve the durability of the unit injector.

[Examples] Examples of the present invention will be described below with reference to the drawings.

In FIG. 1, the unit injector consists of a nozzle section, generally designated 10, and a pump section, generally designated 20. In the nozzle portion 10, a known nozzle assembly 13 is attached to a nozzle holder 11 with a retaining nut 12, and the nozzle holder 11 is provided with a high pressure oil passage 14 and a low pressure oil passage 16 in which a spring valve 15 is interposed. ing.

A pressure chamber 23 is defined in the pump section 20 by a plunger 22 that is in sliding contact with a barrel 21 .
This pressure chamber 23 includes a port 21a that is closed when the plunger 22 descends, and an annular chamber 2 that surrounds the barrel 21.
4 to a fuel supply passage 25, and this fuel supply passage 25 is connected via a connector 26 to a feed pump (not shown) mounted on the engine body.

A guide cover 29 is provided at the top of the plunger 22 and slidably contacts the cylindrical portion 28a of the pump body 28 via a spring seat 27. Then, the spring seat 27 and the pump body 28
The plunger 22 is urged upward and the top of the guide cover 29 is moved between the rocker arm 3 (the fourth
A spring 30 is tensioned to abut against the spring 30 shown in FIG. Further, a pinion 60a is formed in the sleeve 60, and the plunger 22 is rotated through the sleeve 60 by the rack 31 that meshes with the pinion to adjust the stroke of the plunger 22, that is, the injection amount.

On the other hand, the pressure chamber 23 is communicated with the high pressure oil passage 14 of the nozzle holder 11 via the high pressure oil passage 32, and the annular chamber 24 is communicated with the low pressure oil passage 16 of the nozzle holder 11 via the low pressure oil passage 33. Up to this point, it is constructed substantially the same as a conventional unit injector, and operates in the same manner.

In the present invention, a branch portion 34 is provided in the high pressure passage 32.
The branch part 34 is connected to the fuel supply passage 25 via a relief oil passage 35, and the relief oil passage 35 is provided with a relief valve 40 and an orifice 5.
0 is interposed.

In FIG. 2, the relief valve 40 is provided with a needle valve 43 that is seated on a seat surface of a lower body 41, that is, a valve seat 42. As shown in FIG. A seat 44 in contact with the upper end of the needle valve 43 and the upper body 4
A spring 47 that adjusts the opening pressure of the relief valve 40, that is, the relief start pressure, is disposed between the adjusting screw 46 and the adjusting screw 46 that is screwed into the threaded portion of the relief valve 40.
is installed. The lower body 41 is provided with an orifice 50 that communicates between an annular chamber 48 surrounding the small diameter portion 43a of the needle valve 43 and an annular chamber 49 formed between the lower body 41 and the pump body 28.

Next, the operation will be explained mainly with reference to FIG.

In Fig. 3, the horizontal axis shows time t, or the crank angle, and the vertical axis shows the injection pressure P, or the oil pressure in the high-pressure oil passage 32.With conventional unit injectors, when the injection pressure at low speed is increased, the chain line As a result, the maximum pressure becomes excessive (see the dashed line in Fig. 5).
In the present invention, when the injection pressure reaches the relief start pressure P ₁ set by the spring 47 of the relief valve 40, the high pressure oil path 32 releases the oil to the relief oil path 3.
The hydraulic pressure acting on the needle valve 43 through the needle valve 5 pushes up the needle valve 43 against the spring 47 to open it. This allows the pressure oil to flow through the orifice 50.
However, due to the resistance of the orifice 50, the oil pressure rises steadily and smoothly as shown by the solid line without dropping too rapidly, and the maximum pressure Pmax is kept at a suitable value. . Therefore, no excessive pressure acts on the high pressure oil passages 32, 14, and as a result, the durability of the unit injector is improved.

[Effects of the invention] As described above, the present invention provides the following excellent effects.

() Since the pressure is low at low speeds, the relief valve does not open, and the injection pressure is used as is to improve combustion and smoke.

() At high speeds, the combination of relief valve and orifice releases oil and cuts pressure, making it possible to suppress excessive injection pressure.

() The orifice can prevent a sudden drop in oil pressure when the relief valve is opened.

() There is no excessive injection pressure, and the unit injector has a long life.

() Good combustion, preventing smoke generation and reducing fuel consumption.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing an embodiment of the present invention, Fig. 2 is a side sectional view showing a relief valve, Fig. 3 is an injection pressure characteristic diagram explaining the effects of the present invention, and Fig. 4 is a conventional FIG. 5 is a side view showing the unit injector and its injection pressure characteristics. 10... Nozzle part, 20... Pump part, 2
2...Plunger, 25...Fuel supply passage, 32
...High pressure oil path, 35...Relief oil path, 40...Relief valve, 50...Orifice.

Claims (1)

[Scope of utility model registration request] An oil passage 32 pressurized by the plunger 22 of the pump section 20 of the unit injector 10 is provided with a branch section 34 leading to a relief valve 40, and the relief valve 40 has a needle seated on the seat surface 42 of the lower body 41. A valve 43 is provided, and a seat 44 and an upper body 4 contacting the upper end of the needle valve 43 are provided.
A spring 47 for adjusting the opening pressure of the relief valve 40 is tensioned between the adjuster steering screw 46 which is screwed into the threaded portion of the lower body 41.
is provided with an orifice 50 that communicates with an annular chamber 48 surrounding the small diameter portion 43a of the needle valve 43 and an annular chamber 49 formed between the lower body 41 and the pump body 28, and the annular chamber 49 is provided with a fuel supply. A unit injector characterized by being connected to a passage.