JPS63120855A - Fuel injection timing regulating method for diesel engine - Google Patents

Abstract

PURPOSE:To reduce the occurrence of a cam rotation angle reference position error due to the regulation error of a plunger lift, by a method wherein a cam rotation angle is measured in a cam lift high speed region by means of the plunger lift, and is set in a cam rotation angle reference position based on crank angle reference position. CONSTITUTION:A timing mark 28 on the crank pulley 25 side or a timing mark 29 on the engine body side, by means of which an engine crank angle reference position is determined, is set so that a plunger lift regulation reference (cam rotation reference position) can be set in a region where a change in a cam lift (plunger lift) based on a cam rotation angle is increased, except a camlift low speed region. After setting is made in the engine crank angle reference position by mating the timing marks 28 and 29 with each other, lift characteristics of a plunger 6 is measured by means of a dial gauge 31, regulation is made so that a lift amount is adjusted to a given value, and a given cam rotation reference position = a fuel injection timing is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for adjusting fuel injection timing for a diesel engine.

(Prior art) As a conventional fuel injection device for a diesel engine, there is, for example, the one shown in Fig.
1965, etc.), this will be explained first.

In FIG. 5, 1 is a fuel injection pump, 2 is its pump housing, and 3 is a drive shaft rotationally driven by the engine.One is a drive shaft that drives a feed pump 4 to draw fuel into the pump housing 2. .

A plunger 6 having a cam disc 5 connected to the drive shaft 3 so as to be movable relative to the drive shaft 3 in the axial direction is disposed coaxially with the plunger 6, and as the plunger 6 reciprocates inside the cylinder 7, high-pressure pumping is performed. perform the operation.

A roller 1 is mounted on the flange surface of the cam disc 5 and is held in a roller holder 9 whose position is adjustable by a timer piston 8.
A plurality of cams 11 corresponding to the number of cylinders in contact with the cam disk 5 are formed at equal intervals, and the plunger 6 is reciprocated in the axial direction every time the cam 11 is overlaid by the roller 10 by rotation of the cam disk 5. Therefore, the plunger 6 rotates coaxially with the drive shaft 3 and reciprocates by the number of cams 11 per unit rotation.

Here, when the plunger 6 is in the suction stroke moving to the left in the figure, the fuel in the pump housing 2 is sucked into the pumping chamber 14 from the suction port 12 through the suction 113 of the plunger 6, and the plunger 6 moves to the right in the figure. When the fuel in the pumping chamber 14 is compressed, it is delivered to the discharge boat 16 from the distribution groove 15 of the plunger 6, from the delivery valve 17, through the injection pipe 18, and into the injection nozzle 19.
From there, it is injected into the cylinder.

Further, a control sleeve 20 is slidably fitted into a portion of the plunger 6 that exists outside the cylinder 7, and when the cut-off boat 21 of the plunger 6 comes off the inner peripheral surface of the control sleeve 20 and is exposed, the pumping chamber 14
The fuel flows in waves from the cut-off port 21 and forms an injection path. Therefore, by adjusting the position of the control sleeve 20 using the governor mechanism 22, the injection path, that is, the injection amount can be controlled.

As shown in FIG. 2, a timing pulley 23 is attached to the drive shaft 3, and a timing belt (or chain) 26 is wound between it and a crank pulley 25 attached to the crankshaft 24 of the engine. 27 is a tension roller.

Next, we will explain the conventional method of adjusting fuel injection timing.
In order to position the engine crankshaft 24 at the reference position, a timing mark 28 is provided on the crankshaft 725 as shown in FIG. 2, and a timing mark 29 is provided on the engine body side.

Therefore, by first aligning the timing marks 28 and 29, the desired engine crank angle reference position (
For example, obtain the compression top dead center of a specific cylinder.

The rotation of the crank pulley 25 is transmitted by the timing belt 26 to the timing pulley 23 attached to the drive shaft 3 of the fuel injection pump 1, and the rotation of the drive shaft 3 is converted by the cam 11 into reciprocating motion of the plunger 6. therefore,
Remove the closing plug 30 (Fig. 5) from the head of the cylinder 7, insert the dial gauge 31 as shown in Fig. 1,
By measuring the lift amount of the plunger 6 and determining the mounting position of the fuel injection pump 1 so that the lift amount becomes a predetermined value, a predetermined cam rotation angle reference position=fuel injection timing can be obtained.

<Problems to be Solved by the Invention> However, in such a conventional fuel injection timing adjustment method, the cam rotation angle reference position of the fuel injection pump with respect to the engine crank angle reference position is detected by a plunger lift. Therefore, the accuracy of the cam rotation angle reference position relative to the detection accuracy of the plunger lift changes depending on the cam lift speed, and furthermore, in the cam lift low speed region, the cam rotation angle change in response to the plunger lift change is large, so the fuel injection timing adjustment accuracy is There was a problem in that engine performance such as noise, emissions, and output became unstable.

In view of these conventional problems, an object of the present invention is to provide a fuel injection timing adjustment method for a fuel injection pump using a cam with a cam lift speed characteristic having a low speed region with respect to the cam rotation angle. .

Means for Solving Problems> For this reason, the present invention measures the cam rotation angle at the engine crank angle reference position using a plunger lift in a high speed range other than the cam lift low speed range, and calculates the cam rotation angle with respect to the engine crank angle reference position. It is designed to be set at a reference position.

(Function) By measuring and adjusting the plunger lift in the cam lift high speed region in this manner, the cam rotation angle reference position error relative to the adjustment error of the plunger lift can be reduced.

(Example) An example of the present invention will be described below based on FIGS. 1 to 4.

FIG. 3 is a characteristic diagram of cam lift (L) and cam lift speed (V) with respect to the cam rotation angle (θ), and shows a region where the change in cam lift (plunger lift) with respect to the cam rotation angle is large other than the cam lift low speed region (θ8. At the plunger lift adjustment reference point (cam lift high speed region of L8 or higher)
The timing mark 28 on the crank pulley 25 side or the timing mark 29 on the engine body side, which determines the engine crank angle reference position, is set so that the cam rotation angle reference position) can be set. The other configurations are the same as those in FIGS. 1 and 2.

Conventionally, this timing mark was set to be the compression top dead center of a specific cylinder (for example, the first cylinder), but when the compression top dead center was used as the reference point, the plunger lift adjustment reference point was set in the low speed region of the cam. For example, in Figure 3, if the reference point is (
θ. , Lo), then Δθ=01−〇. Move the timing mark by the amount of time it takes to move the timing mark to the position after compression top dead center.

Therefore, by first aligning the timing marks 28 and 29, the engine crank angle reference position is set. At this time, the cam lift is in the high speed region.

Next, the lift amount of the plunger 6 is measured with the dial gauge 31, and the lift amount is adjusted to a predetermined value to obtain a predetermined cam rotation angle reference position=fuel injection timing.

When the fuel injection timing is adjusted based on the plunger lift in this way, as shown in Figure 4, the plunger lift adjustment reference point is set at the point L+ where the cam lift speed is high, and when it is set at the low speed region Lo. The same adjustment error ±
Since the change in the cam rotation angle with respect to ΔL is small, the variation in the cam rotation angle reference position can be reduced (Δθ1<Δθ).

).

<Effects of the Invention> As explained above, according to the present invention, since the injection timing adjustment reference point (plunger lift adjustment reference point) is set in a high speed region other than the cam lift low speed region, the cam is The rotation angle reference position error can be reduced, thereby improving the accuracy of fuel injection timing adjustment and achieving stable engine performance.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a fuel injection pump during fuel injection timing adjustment, showing an embodiment of the present invention, Fig. 2 is a schematic diagram of the drive mechanism of the fuel injection pump, and Figs. 3 and 4 are cam rotation angles. FIG. 5 is a sectional view of the fuel injection pump. 1...Fuel injection pump 3...Drive shaft 6...
・Plunger 11...Cam 23...Timing pulley 25...Crank pulley 26...Timing belt 28, 29...Timing mark
31...Dial cage patent applicant Fujio Sasashima, agent of Nissan Motor Co., Ltd., patent attorney Figure 3 Figure 4

Claims (1)

[Claims] In a diesel engine equipped with a fuel injection pump that is equipped with a cam that converts the rotation of a drive shaft driven by the engine into reciprocating motion and transmits it to the plunger, and this cam has a cam lift speed characteristic that has a low speed region with respect to the cam rotation angle. Fuel injection for a diesel engine, characterized in that the cam rotation angle at an engine crank angle reference position is measured from a plunger lift in a high speed range other than the low speed range, and the cam rotation angle reference position is set with respect to the engine crank angle reference position. How to adjust the timing.