JPH0784855B2 - Adjustment method of initial lift amount in two-stage valve opening pressure fuel injection nozzle - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of adjusting an initial lift amount in a two-stage valve opening pressure fuel injection nozzle.

[0002]

2. Description of the Related Art In a two-stage valve-opening pressure fuel injection nozzle (hereinafter sometimes simply referred to as a fuel injection nozzle), when a fuel pressure exceeds an initial valve opening pressure, a needle valve is initially lifted to perform an initial injection. When the fuel pressure is further increased and becomes equal to or higher than the main valve opening pressure, the needle valve is fully lifted and the main injection is performed. In the case of adjusting the initial lift amount of the needle valve in such a two-stage valve-opening pressure fuel injection nozzle, the initial lift amount of the needle valve is actually measured and adjusted so that this measured value falls within a predetermined allowable value. (See JP-A-59-46364).

[0003]

However, when the initial lift amount of the needle valve is controlled by the allowable value, there is a problem that the initial injection amount among the fuel injection nozzles greatly varies.

Upon pursuing this point, it was found that the cause was as follows. That is, the relationship between the lift amount of the needle valve and the fuel injection amount is different between the fuel injection nozzles A and B as shown in FIG. 4 due to the manufacturing error of the injection holes in each fuel injection nozzle. In this case, the increase rate of the fuel injection amount with respect to the lift amount is large in the range where the lift amount is about the initial lift amount. Therefore, if the initial lift amount is controlled by the upper and lower tolerances L _max and L _min , the maximum value Q _max and the minimum value Q _{min of} the fuel injection amount will be significantly different. As a result, there was a large variation in the initial injection amount between the fuel injection nozzles.

The present invention has been made on the basis of the above findings, and an object thereof is to provide a method of adjusting the initial lift amount in a two-stage valve opening pressure fuel injection nozzle capable of suppressing the variation in the initial injection amount. To do.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention initially lifts a needle valve when the pressure of fuel pumped from a fuel injection pump exceeds an initial valve opening pressure,
When the fuel pressure exceeds the main valve opening pressure, the needle valve fully lifts.Two-stage valve opening pressure When adjusting the initial lift of the fuel injection nozzle, the two-stage valve opening pressure A fuel having a pressure lower than the valve opening pressure is supplied, and the initial lift amount of the needle valve is adjusted so that the supply amount of this fuel per unit time is within a predetermined range. is there.

[0007]

The fuel having a pressure higher than the initial valve opening pressure and lower than the main valve opening pressure is supplied to the fuel injection nozzle, and the supply amount per unit time is measured. Then, the lift amount of the needle valve is adjusted so that the supply amount per unit time falls within a predetermined range.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a fuel supply device 1 used for carrying out the adjusting method of the present invention. The fuel supply device 1 supplies fuel of a predetermined pressure to a two-stage valve opening pressure fuel injection nozzle 2. Therefore, it is configured as follows.

In FIG. 1, reference numeral 3 is a cylinder device. The cylinder device 3 includes a cylinder 4 and a piston 5, and the cylinder 4 has a large-diameter cylinder hole 4
a and a small diameter cylinder hole 4b. A large diameter piston portion 5a of the piston 5 is slidably provided in the large diameter cylinder hole 4a, and a small diameter piston portion 5b of the piston 5 is slidably provided in the small diameter cylinder hole 4b. The large diameter piston portion 5a and the small diameter piston portion 5b are integrally connected by a rod 5c.

The inside of the cylinder 4 is divided into three chambers by a piston 5. That is, the pressurized fuel introduction chamber 6 is defined by the large-diameter cylinder hole 4a and the large-diameter piston portion 5a, and the large-diameter cylinder hole 4a, the small-diameter cylinder hole 4b, the large-diameter piston portion 5a, and the small-diameter piston portion 5b.
The return fuel introducing chamber 7 is defined by, and the fuel pressurizing chamber 8 is defined by the small diameter cylinder hole 4b and the small diameter piston portion 5b.

The pressurized fuel introducing chamber 6, the return fuel introducing chamber 7 and the fuel pressurizing chamber 8 are connected to the pump 10 by a directional switching valve 9.
And the fuel tank 11 are connected. That is, when the direction switching valve 9 is in the illustrated state, the pressurized fuel introducing chamber 6 is connected to the fuel tank 11, and the return fuel introducing chamber 7 and the fuel pressurizing chamber 8 are connected to the pump 10.
Connected to. When the direction switching valve 9 is switched from the illustrated state, the pressurized fuel introducing chamber 6 is connected to the pump 10, and the return fuel introducing chamber 7 and the fuel pressurizing chamber 8 are connected to the fuel tank 11. However, immediately before the fuel pressurizing chamber 8, the check valve 1
2 is installed, the fuel in the fuel pressurizing chamber 8 does not flow out to the fuel tank 11.

In the above structure, when the pressurized fuel supply chamber 6 is connected to the pump 10, the fuel introduced into the pressurized fuel introduction chamber 6 causes the piston 5 to move from the large diameter cylinder hole 4a side toward the small diameter cylinder hole 4b side. Can be moved. Then, the fuel in the fuel pressurizing chamber 8 is pressurized to a high pressure based on the area difference between the large diameter piston portion 5a and the small diameter piston portion 5b. The pressurized fuel is sent under pressure to the fuel injection nozzle 2. In this case, the pressure of the fuel pumped to the fuel injection nozzle 2 can be adjusted by adjusting the pressure of the fuel supplied from the pump 10 to the pressurized fuel introduction chamber 6 by the pressure adjusting valve 13. Normally, the pressure of the fuel supplied to the fuel return nozzle 2 is set to be a pressure higher than the initial valve opening pressure of the fuel injection nozzle 2 and lower than the main valve opening pressure, for example, a pressure higher than the initial valve opening pressure by about 10 Kg / cm ^2. Adjusted. The pressure of the fuel supplied to the fuel injection nozzle 2 is measured by the pressure gauge P.

When the direction switching valve 9 is switched from the above state, fuel is supplied from the pump 10 to the return fuel introducing chamber 7 and the fuel pressurizing chamber 8. Therefore, the piston 5 returns and moves from the small diameter cylinder hole 4b side toward the large diameter piston hole 4a side. As a result, the fuel in the pressurized fuel introducing chamber 6 is returned to the fuel tank 11.

Between the pressurized fuel introducing chamber 6 and the direction switching valve 9, a throttle 14a for suppressing the pulsation of the fuel supplied from the pump 10 to the pressurized fuel introducing chamber 6 and the pressurized fuel introducing chamber A hydraulic block 14 is installed in which a check valve 14b for allowing fuel to flow out from the chamber 6 to the fuel tank 11 without resistance is installed in parallel. A hydraulic block 15 having a throttle 15a and a check valve 15b, which is similar to the hydraulic block 14, is also installed between the return fuel introduction chamber 7 and the direction switching valve 9.

Further, the cylinder device 3 is provided with a position sensor 17 such as a magnet scale along the large diameter cylinder hole 4a. This position sensor 17
It is for detecting the position of the large-diameter piston portion 5a, and its output is output to the calculating means 18. Computing means 1
Reference numeral 8 calculates the supply amount Q of the fuel supplied from the cylinder device 3 to the fuel injection nozzle N based on the output signal from the position sensor 17. That is, assuming that the positions of the large-diameter piston portion 5a before and after the elapse of a unit time are A ₁ and A ₂ , respectively, and the cross-sectional area of the small-diameter cylinder hole 4b is S, the fuel supply amount Q per unit time is S · (A ₂ -A ₁ ). The supply amount Q calculated by the calculation means 18 is output to the recorder 19. The recorder 19 records the supply amount Q, and FIG.
Graph as shown in.

Next, the case where the initial lift amount of the fuel injection nozzle 2 is adjusted by using the fuel supply device 1 having the above-mentioned configuration will be described. The direction switching valve 9 is switched from the state shown in the figure, and fuel is supplied to the pressurized fuel introduction chamber 6 from the pump 10. This pressurizes the fuel in the fuel pressurizing chamber 8 and supplies the fuel to the fuel injection nozzle 2.

Since the fuel supplied to the fuel injection nozzle 2 has a pressure higher than the initial valve opening pressure and lower than the main valve opening pressure, the needle valve (not shown) of the fuel injection nozzle 2 is initially lifted. At the same time, the fuel is injected from the fuel injection nozzle 2. In this case, the injection amount injected from the fuel injection nozzle 2 is a constant amount because the pressure of the supplied fuel is constant and the lift amount of the needle valve is constant (initial lift amount).
Therefore, the supply amount of fuel supplied to the fuel injection nozzle 2 (supply amount per unit time) also becomes constant, and is recorded by the recorder 19 as indicated by a, b, and c in FIG.

When the supply amount Q per unit time is between the upper limit value and the lower limit value set in advance as shown in (a) of FIG. 2, the fuel injection nozzle 2 is regarded as a proper product and is directly treated as a product. To be done. When the supply amount is larger than the upper limit value as shown in (b) of FIG. 2, the initial lift amount of the fuel injection nozzle 2 is corrected to be small. Then, the above supply amount measurement is performed again. This is repeated until the supply amount Q falls between the upper limit value and the lower limit value. When the supply amount is smaller than the lower limit value as shown in FIG. 2C, the initial lift amount of the fuel injection nozzle 2 is corrected to be large. After that, it is the same as the above case a.

As is well known, the adjustment of the initial lift amount is performed by changing the thickness of the shim or the like which regulates the initial lift amount.

As described above, by adjusting the initial lift amount based on the supply amount Q, it is possible to reduce the variation in the initial injection amount in each fuel injection nozzle 2. That is, the supply amount Q per unit time and the actual fuel injection amount are almost the same when the mutual pressures are equal. Therefore, when the initial lift amount of the needle valve is adjusted by the supply amount Q, the variation in the initial lift amount may increase as shown in FIG. 3, but the variation in the initial injection amount can be suppressed to be small. it can. It should be noted that the upper limit value and the lower limit value of the supply amount are values that are within the range so that variations in the initial injection amount do not pose a problem, and are determined by experiments.

The present invention is not limited to the above embodiments, but can be modified as appropriate without departing from the scope of the invention. For example, instead of the fuel supply device 1 in the above embodiment, the fuel may be supplied to the fuel injection nozzle 2 by another supply device. Further, in the above-described embodiment, the pressure of the fuel supplied to the fuel injection nozzle 2 is kept constant during the supply amount measurement period, but if it is difficult to do so, for example, the supplied fuel The pressure may be gradually increased to detect whether the supply amount at a predetermined pressure falls between the upper limit value and the lower limit value.

[0022]

As described above, according to the method of adjusting the initial lift amount of the present invention, fuel having a pressure higher than the initial valve opening pressure but lower than the main valve opening pressure is supplied to the fuel injection nozzle, Since the initial lift amount of the needle valve is adjusted so that the supply amount per time is within a predetermined range, it is possible to suppress the variation in the initial injection amount in each fuel injection nozzle. can get.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a fuel supply device for carrying out an adjustment method of the present invention.

FIG. 2 is a diagram showing a relationship between a measurement time and a supply amount of fuel per unit time when fuel having a constant pressure is supplied to a fuel injection nozzle in the apparatus shown in FIG.

3 is a diagram showing a relationship between a lift amount of a needle valve and a fuel supply amount per unit time when fuel is supplied to a fuel injection nozzle in the device shown in FIG.

FIG. 4 is a diagram showing a relationship between a lift amount of a needle valve and a fuel injection amount.

[Explanation of symbols]

 1 Fuel Supply Device 2 Fuel Injection Nozzle 3 Cylinder Device 18 Arithmetic Means 19 Recorder

Claims (1)

[Claims] 1. A two-stage open in which the needle valve is initially lifted when the pressure of the fuel pumped from the fuel injection pump is equal to or higher than the initial valve opening pressure, and the needle valve is fully lifted when the fuel pressure is equal to or higher than the main valve opening pressure. When adjusting the initial lift amount of the valve pressure fuel injection nozzle, fuel having a pressure higher than the initial valve opening pressure and lower than the main valve opening pressure is supplied to the two-stage valve opening pressure fuel injection nozzle, and this fuel per unit time A method for adjusting an initial lift amount in a two-stage valve opening pressure fuel injection nozzle, characterized in that an initial lift amount of a needle valve is adjusted so that a supply amount falls within a predetermined range.