JPH078841Y2 - Fuel injector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a fuel injection device for supplying fuel to a combustion chamber of an internal combustion engine using a fuel injection nozzle.

(Prior Art) An internal combustion engine, especially a diesel engine, injects fuel from its fuel supply system into a high-pressure gas in a combustion chamber using an injection pump and an injection nozzle, burns the fuel, and generates thermal energy with it. Is getting the output according to.

The fuel injection pump and the fuel injection nozzle used here have a shorter high-pressure oil passage when they are integrated than when they are separate bodies, and moreover, transmission of the pressure wave from the fuel injection pump to the fuel injection nozzle. The delay is reduced and the injection timing can be adjusted easily.

That is, a so-called unit injector 3 is attached to the cylinder head 2 above the combustion chamber 1 of the diesel engine shown in FIG. This unit injector 3 has a fuel injection nozzle 4 at its lower portion and a fuel injection pump 5 at its upper portion, and a high pressure oil passage 8 is provided between a plunger chamber 6 in which an upper plunger 9 slides and a lower nozzle chamber 7. It is connected by. A branch passage 11 extends from the middle of the high-pressure oil feed passage 8, and this branch passage is connected to the low-pressure passage 15 via the solenoid valve 10.
It is connected to the side.

The solenoid valve 10 is composed of a needle valve 12 and a valve drive unit 13 that opens and closes the needle valve, and the valve drive unit is driven by a valve control device 14. In this device, when the solenoid valve 10 is closed, the combustion chamber 1
Fuel is injected into the high pressure oil passage 8 to return the oil when opened.

The injection pressure Pf generated by such a fuel injection device is V, where V is the total volume in the high-pressure oil passage system that is in constant communication with the high-pressure oil passage 8, and is the compression volume in the high-pressure oil passage system that is the sliding volume of the plunger 9. Δ
If V is V and the bulk modulus is K, it is statically expressed by the following equation.

Pf = K · ΔV / V (1) (Problems to be solved by the invention) However, the injection pressure Pf when driving such a fuel injection device is such that the flow velocity of the fuel flowing through the high-pressure oil passage 8 is large. As a result, the injection pressure Pf increases as the engine speed increases, as indicated by the broken line A and the chain line B in FIG.
Has the property of increasing.

Therefore, if the injection pressure Pf at the maximum engine speed is suppressed below the durability limit pressure Plim of the unit injector 3, the injection pressure Pf at the low engine speed becomes too low. On the contrary, if the injection pressure Pf at a low rotation speed is set high, the injection pressure Pf at a high rotation speed region becomes too high, and the durability is lost. An object of the present invention is to provide a fuel injection device capable of relatively reducing the vertical deviation of the injection pressure over the entire number range.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a pump chamber supported by an engine body of an internal combustion engine and supplied with fuel from a fuel supply system, and an output shaft of the internal combustion engine. And a plunger that pressurizes the fuel in the pump chamber in response to the driving force of the pump chamber, and high-pressure fuel from the pump chamber is supplied through a high-pressure oil passage and the fuel is supplied to the combustion chamber of the internal combustion engine when the needle valve is opened. An injection nozzle for injecting, and a fuel injection solenoid valve that opens and closes between the high-pressure oil passage and the low-pressure oil passage, and the high-pressure oil passage has a pressure regulating chamber via a pressure regulating solenoid valve. It is characterized in that it is connected so that it can communicate with each other, and the pressure regulating solenoid valve is controlled by the control means so as to open when the engine speed exceeds a set value.

(Operation) When the engine speed is below the set value, the pressure regulating solenoid valve closes, and when the engine speed exceeds the set value, the pressure regulating solenoid valve opens, and the pressure regulating chamber communicates with the high pressure oil passage side, and the high pressure oil By increasing the total volume V of the passage system, it is possible to suppress an excessive increase in injection pressure.

(Embodiment) The fuel injection device of FIG. 1 is a combustion chamber 20 of a diesel engine.
Fuel is injected into a cylinder head 21 of a diesel engine, and a base portion 22 thereof is incorporated and fixed. A fuel injection pump 23 is provided above the base 22 and a fuel injection nozzle 24 is provided below the base 22, and both are connected by a high-pressure oil feed passage 25.

The fuel injection pump 23 is a plunger chamber formed in the base 22.
Plunger that can slide in the same room as 26 and this plunger
And a plunger drive system 29 that presses 27 against the elastic force of the return spring 28.

The plunger chamber 26 is formed with an inflow port 30 on its inner wall and an outflow port 31 on its lower wall, and the inflow port 30 is connected to a feed pump side (not shown) via a low pressure fuel supply passage 32 and an outflow port 31.
Are connected to high-pressure oil passages 25, respectively. Plunger
27 is the stroke S from the pressurization start position B1 with the inlet 30 closed.
Is moved to reciprocate to reach the pressurization end position B2, and fuel is continuously pumped during this time.

The plunger drive system 29 is pivotally supported by a base portion (not shown) of the diesel engine, and receives the output rotational force of the engine and rotates at a half speed thereof, and a push cam reciprocated by the cam. Rod 34 and shaft on base 22
It is composed of a rocker arm 36 pivotally supported via 35. Here, the lift operation of the drive cam 33 is configured so as to overlap with the vicinity of the front and rear of the compression top dead center of the engine in timing.

The fuel injection nozzle 24 is an injection port 37 for injecting fuel into the combustion chamber 20.
A nozzle chamber 38 inside the nozzle, and a needle valve 39 as a needle valve that is biased to close the nozzle 37 and that opens and closes the nozzle. The needle valve 39 receives the pressure of the nozzle chamber 38 in the annular pressure receiving portion 40 and performs a lift operation.

A branch passage 41 is formed so as to extend from the middle of the high-pressure oil passage 25, and the tip thereof is connected to the low-pressure oil passage 43 side via an electromagnetic spill valve (hereinafter simply referred to as a first solenoid valve) 42 serving as a fuel injection solenoid valve. Is formed so that it can communicate with. The low-pressure oil passage 43 communicates with the drain pipe side of a fuel tank (not shown). Fork 41
A branch path 44 is further branched from the middle of the path, and the branch path 44 is opened and closed by a second solenoid valve 45 as a pressure regulation solenoid valve and the pressure regulation chamber 46.
Is in communication with.

The pressure adjusting chamber 46 has a predetermined volume Va, and when the second solenoid valve 45 is on, the total volume V of the high pressure oil passage system including the branch passage 44, the branch passage 41, the high pressure oil feed passage 25, and the plunger chamber 26 is Va. Only increase. The volume of the pressure adjusting chamber is experimentally set so as to obtain the characteristic C in FIG.

The first solenoid valve 42 is formed by a valve drive unit 47 and a needle valve 48. When the valve is off, the tip of the needle valve 48 separates from the valve seat 49, and when the valve is on, the tip of the needle valve 48 contacts the valve seat 49. Close branch 41,
At this time, the fuel injection nozzle 24 operates to inject.

The second solenoid valve 45 is formed by the valve drive unit 50 and the needle valve 51, and closes the branch passage 44 when it is off and opens the branch passage when it is on.

Both of these solenoid valves 42, 45 are connected to the controller 5 as a control means.
Connected to 2.

A main part of the controller 52 is formed by a microcomputer, and a rotation sensor that outputs engine rotation information is provided in the controller 52.
53, a load sensor 54 that outputs engine load information, and a sensor (not shown) that outputs engine warm-up information and the like are connected at least. In the processing as the engine controller, the controller 52 uses the engine speed, load information, warm-up information, etc. to inject fuel injection timing (a time width corresponding to a deviation angle α from the reference position K as shown in FIG. 2) and injection. The amount (a value proportional to the time width shown as T in FIG. 2) is calculated, and the first electromagnetic field is calculated via the injector drive circuit 521 based on the latest fuel injection timing and injection amount value calculated for each injection process. Drive the valve 42.

Moreover, the current engine speed Ne and load information are taken in,
Based on this and the second solenoid valve drive map of FIG. 3, ON,
The off output is calculated, and this output drives the second solenoid valve 45 via the second solenoid valve drive circuit 522.

Here, the second solenoid valve drive map of FIG. 3 has the characteristics of calculating the on output in the idle region and the high rotation and high load region of the engine, and the off output in the other regions. This makes it possible to prevent noise during idling and ensure the durability of the injector at high output.

In such a fuel injection device, the drive cam 33 injects the plunger 27 via the valve drive system 29 in response to the drive of the engine. During the injection operation, while the first solenoid valve 42 is off, all the fuel on the high-pressure oil passage side, which is increased in pressure by driving the plunger, flows down from the branch passage 41 to the low-pressure passage 43 side, and the plunger 27 idles during this period. Then, when the controller 52 makes an ON output, the needle valve 48 is closed during this period, the hydraulic pressure in the nozzle chamber 38 is rapidly increased, the needle valve 39 is lifted, and based on the characteristics shown in FIG. Fuel is injected.

Further, if it is determined from the engine speed information and the load information that the operating region of the engine is in the ON region of FIG. 3, the controller 52
Outputs an ON output to the second solenoid valve 45, and connects the pressure adjusting chamber 46 to the high pressure oil passage side. As a result, the injection pressure Pf is lowered from Pfa to Pfb (one example of which is indicated by the symbol C in FIG. 5). It is possible to prevent the injection pressure Pf from exceeding the endurance limit pressure Plim (see FIG. 5) even when the pressure is reduced and the rotation speed is further increased from the current state, and idle noise can be reduced during idling.

Although the pressure adjusting chamber 46 is connected to the branch passage 41 in the above-described processing, it may be formed so as to be connectable to another high pressure oil passage system instead.

(Effect of the Invention) As described above, according to the present invention, the vertical deviation of the injection pressure can be relatively reduced over the entire range of the engine speed, that is, the injection pressure at the low engine speed can be set relatively high. It is possible to suppress the injection pressure at a high rotation speed to be equal to or lower than the durability limit pressure, and it is possible to stabilize the rotation by securing the injection amount at a low rotation speed and to secure the durability at a high rotation speed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a fuel injection device and an internal combustion engine equipped with the same as one embodiment of the present invention, FIG. 2 is a characteristic diagram of an injection valve drive current of the same device, and FIG. 3 is the same device. FIG. 4 is a characteristic diagram of a solenoid valve drive map incorporated in the engine, FIG. 4 is an injection pressure characteristic diagram of the same device, FIG. 5 is an engine speed-injection pressure characteristic diagram of the fuel injection device, and FIG. 6 is a conventional device. FIG. 20 …… combustion chamber, 22 …… base, 24 …… injection nozzle, 25 ……
High-pressure oil passage, 26 …… plunger, 27 …… plunger, 29
...... Plunger drive system, 32 …… Fuel supply path, 39 …… Needle valve, 42 …… First solenoid valve, 43 …… Low pressure oil path, 45 …… Second solenoid valve, 46 …… Pressure adjusting chamber, 52 ……controller.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Yoharu Yamada 10 Okuramachi, Nakahara-ku, Kawasaki-shi, Kanagawa Japan Automotive Engineering Co., Ltd. Kawasaki Plant

Claims (1)

[Scope of utility model registration request] 1. A plunger chamber supported by an engine body of an internal combustion engine and supplied with fuel from a fuel supply system, and a plunger for receiving a driving force from an output shaft of the internal combustion engine to pressurize the fuel in the pump chamber. A high-pressure fuel from the pump chamber is supplied through the high-pressure oil passage and an injection nozzle that injects fuel into the combustion chamber of the internal combustion engine when the needle valve is opened; and the high-pressure oil passage and the low-pressure oil passage. And a fuel injection solenoid valve that opens and closes the space between them, and a pressure regulation chamber is connected to the high pressure oil passage via a pressure regulation solenoid valve, and the pressure regulation solenoid valve sets the engine speed. A fuel injection device controlled by a control means to open when a value exceeds a value.