JP2003184708A - Method for measuring fuel injection start timing in engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for measuring a fuel injection start timing capable of automatically measuring of fuel injection start timing accurately in a short time and measuring all engines in a line without increasing the number of operators. <P>SOLUTION: A crack shaft is rotated by external power under a condition that fuel is compressed at designated pressure and is fed to a fuel injection pump mounted on a crank case. A change of fuel feeding pressure P nearby a fuel injection start timing is detected by comparing with crankshaft angles θand the fuel injection start timing is measured by automated analysis of detected data. An approximate line L in a fuel feeding pressure rising area and an average value P1 line in a stable pressure after the rise are computed, and a crankshaft angles θs at intersection points of these lines is defined as the fuel injection start timing. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a fuel injection start timing of a fuel injection pump mounted on a diesel engine.

[0002]

2. Description of the Related Art A fuel injection pump mounted on a diesel engine is connected to a pump mounting seat of a crankcase via a shim, and a dimensional error between a camshaft axial center of the crankcase and the pump mounting seat. If the size is large or a shim with a different thickness is installed, the dimensional distance between the cam shaft axis and the fuel injection pump will change, and the fuel injection start timing will deviate from the proper state, adversely affecting exhaust gas. Become. Therefore, with the fuel injection pump installed in the engine, it is determined whether the fuel injection start timing is within the allowable range, the defective product is extracted, and only the engine with stable performance is supplied to the market. ing.

The conventional method of measuring the fuel injection start timing is performed off-line separately from the engine assembly line.
First, the crankshaft is manually rotated while the dial gauge is in contact with the upper surface of the piston of the engine in which the cylinder head is not assembled, and the piston top position that is the reference angle of the fuel injection start timing is detected.

Next, the crankshaft is manually rotated while the fuel is pumped to the fuel injection pump by the hydraulic pump at a predetermined pressure, and a few drops of the fuel flow out from the first cylinder outlet of the fuel injection pump per second. That is, the crankshaft angle based on the piston top position angle at that time was used as the fuel injection start timing.

[0005]

In the above-mentioned conventional measuring direction, the time required for measurement per one unit is about 5 minutes including the attachment and detachment of the dedicated jig, and it is necessary to measure all the units inline. Required a lot of workers. For example, if the total number is to be measured in-line with a tact time of 50 seconds, it is necessary to increase the number of employees by five.

Further, since the measurement form by visual confirmation is adopted, the measurement result is likely to vary (± 1 ° or more depending on the operator's feeling) depending on the operator's feeling, and in order to improve the engine quality. Higher precision measurement is desired.

The present invention has been made paying attention to such a point, and the automatic measurement of the fuel injection start timing can be accurately performed in a short time, without increasing the number of workers. Its main purpose is to provide a fuel injection start timing measurement direction that enables in-line measurement of the total number of fuel injection units.

[0008]

According to a first aspect of the present invention, there is provided a fuel injection start timing measuring method for an engine, wherein a crankshaft is fed to a fuel injection pump assembled in a crankcase while the fuel is being pumped at a predetermined pressure. It is characterized in that it is rotated by external power, a change in the supplied fuel pressure near the fuel injection start timing is detected in comparison with the crankshaft angle, and the fuel injection start timing is measured by automatic analysis of the detection data.

The fuel injection timing measuring method for an engine according to a second aspect of the present invention is characterized in that, in the first aspect of the invention, the fuel injection start timing is measured by analyzing the waveform of the supplied fuel pressure near the fuel injection start timing. To do.

According to a third aspect of the present invention, there is provided an engine fuel injection timing measuring method according to the second aspect of the invention, wherein an intersection of an approximate straight line of a rising region of the supplied fuel pressure and an average straight line of a pressure stable region after rising. Is used as the fuel injection start timing.

According to the fuel injection start timing measuring method of the present invention, the fuel injection pump assembled to the crankcase is connected to the fuel supply means having the means for detecting the supplied fuel pressure, and the crankshaft angle is measured. Means, the crankshaft is rotated at a low speed by an external drive means such as a motor, and the fluctuation data of the supplied fuel pressure with respect to the crankshaft angle is detected and collected, and the detected data is automatically analyzed to determine the fuel injection start timing. Figure out.

Considering the fluctuation of the supplied fuel pressure in the Bosch type fuel injection pump shown in FIG. 2, the fuel is supplied to the fuel supply port b of the fuel injection pump 5 at a predetermined pressure (set by a relief valve). When the cam 23 for driving the pump is rotated at a low speed in this state, the fuel in the fuel supply line 27 is drawn into the fuel intake port during the stroke in which the plunger 24 ascends to the top dead center and finishes one fuel delivery. Since the fuel is sucked into the plunger 24 from a, the fuel pressure supplied to the fuel supply line 27 becomes lower than the set pressure, as shown in FIG. 9A. Then, when the plunger 24 enters the ascending stroke, the fuel inlet a of the plunger barrel 25 is gradually closed by the plunger 24, and the fuel pressure supplied to the fuel supply line 27 gradually increases. Then, the fuel injection (pressure feeding) process starts from the time when the plunger 24 completely closes the fuel intake port a, the fuel trapped in the plunger barrel 25 is pressurized, and the delivery valve is pushed open to be delivered. In this fuel injection stroke, the fuel inlet a of the plunger barrel 25
Remains closed by the plunger 24,
The fuel pressure supplied to the fuel supply line 27 is maintained at the set pressure. Then, when the rising inclined groove of the plunger 24 communicates with the fuel intake port a and the fuel injection stroke ends, the fuel supply pressure in the fuel supply conduit 27 starts to decrease.

In the operation of the above fuel injection pump,
The fuel injection start timing is the time when the fuel intake port a of the plunger barrel 25 is closed by the ascending plunger 24. At this time, the fuel pressure supplied to the fuel supply conduit 27 ends at the rise and stabilizes at a predetermined pressure. It's time. In other words, if the fluctuation waveform of the fuel pressure supplied to the fuel supply line 27 is detected and the inflection point A from the rising region of the pressure to the stable region of the set pressure is detected, the crankshaft angle θs at that point will start fuel injection. It is time.

However, the actual fluctuation waveform of the supplied fuel pressure is, as shown in FIG. 9B, the inflection portion from the rising region of the pressure to the stable region of the set pressure is a curved waveform, and the stable region The waveform also includes some fluctuations, and the inflection point cannot be directly grasped.

Therefore, in the method of the present invention, the waveform of the rising region is approximated to the straight line L by the calculation based on the detected data, the average value P1 of the stable region is calculated, and the obtained straight line of the approximate line L and the average value P1 is calculated. The intersection point with and is grasped as the inflection point A, and the crankshaft angle θs at this point is taken as the fuel injection start timing.

[0016]

1 is a block diagram showing a schematic configuration for carrying out a fuel injection start timing measuring method according to the present invention, in which 1 denotes a diesel engine to which a cylinder head is not yet attached. Engine crankcase, 2
Is a crankshaft, 3 is a piston incorporated in a plurality of cylinders of the crankcase 1, and 4 is a piston 3 in a predetermined cylinder.
Of the contact type acting on the upper surface of the fuel cell, 5 is a fuel injection pump mounted on the side of the crankcase 1, 6 is a motor for forcibly rotating the crankshaft 2 from the outside, and 7 is mounted on the motor 5. A rotation sensor such as a rotary encoder, 8 is a fuel supply tank, 9 is a motor-driven fuel supply pump that pumps the fuel in the fuel supply tank to the fuel injection pump 5, and 10 is a relief valve that sets and maintains the fuel supply pressure,
Reference numeral 11 is a pressure sensor for detecting the pressure of the fuel to be pumped, 1
Reference numeral 2 is a fuel recovery tank for recovering fuel delivered from a predetermined cylinder outlet 4a of the fuel injection pump 4, 13 is a fuel reduction pump, 14 is a fuel filter, and the displacement sensor 4, the pressure sensor 11, and The detection data from the rotary encoder 7 is the D / A converter 15 and the amplifier 16.
Are input to the arithmetic unit 17 using the microcomputer via.

FIG. 2 shows a schematic structure of the fuel injection pump 5. The fuel injection pump 5 is mounted and connected to a mounting seat formed in a part of the crankcase 1 via a gasket shim 21 for adjusting injection timing, and a camshaft 22 supported in the crankcase 1 is not shown. It is geared to the crankshaft 2. As the fuel injection pump 5 itself, a well-known Bosch type is used.
When the plunger 24 is pushed up by the rotation of the cam 23 provided for the plunger 24, the fuel F in the plunger barrel 25 is pressurized from the time when the plunger 24 blocks the fuel intake port a of the plunger barrel 25, and the delivery valve 2
6 is pushed out and delivered, and the plunger 24
The injection start time is when the fuel intake port a of the plunger barrel 25 is blocked.

The present invention is a method for automatically measuring the above injection start timing, and the details thereof will be described below with reference to the flowchart of FIG.

First, the crankcase 1 as a work
Is a crankshaft 2, a group of pistons 3, a fuel injection pump 5,
The camshaft 22 and the gears for driving the camshaft are assembled, and the camshaft 22 is carried into the measurement area in the engine assembly line in an upper open state where the cylinder head is not assembled. When the work reaches a predetermined position, the motor 6 is automatically connected to the shaft end of the crankshaft 2 via the coupling 18, and the fuel is supplied to the fuel supply port b and the fuel delivery port c of the fuel injection pump 5. The pipe 27 and the fuel recovery pipe 28 are connected by an operator. Further, the displacement sensor 4 is carried into a cylinder (for example, the first cylinder) preset for measurement, and the detection end of the displacement sensor 4 is brought into downward contact with the upper surface of the piston 3 of the cylinder.

Next, the crankshaft 2 is rotated at a low speed (for example, 10 rpm) by the motor 6, and the measurement is started. The height of the upper surface of the piston 3, which is displaced vertically as the crankshaft 2 is rotated, is measured, and
Is measured by the rotation sensor 7 (# 1), and the crankshaft angle (piston top position angle θ0) at the time when the piston 3 reaches the upper limit is calculated (#).
2). As shown in FIG. 8, the piston top position angle θ0 is calculated as a bisected position of the crankshaft angles θ1 and θ2 that provide the same height detection value near the piston top position.

When the piston top position angle θ 0 is detected, the crankshaft 2 is rotated at a low speed (eg 10 rpm) while the fuel is being pumped at a predetermined pressure (eg 30 kgf / cm ² ),
The pressure change of the supplied fuel in the range before and after the fuel injection start timing is detected by the pressure sensor 11 in comparison with the crankshaft angle, and the injection start timing is determined by the following waveform analysis of the detection data.

First, the crankshaft angle θ and the supplied fuel pressure P are sampled (# 3) in the injection start timing measurement range from the measurement start angle to the measurement end angle, and the sampled supply fuel pressure data is set in advance. The moving average is calculated by the number of points (for example, 31 points), and the fluctuation waveform shown in FIG. 3 is obtained (# 4).

Next, an average value P1 of the supplied fuel pressures in a constant range (average value acquisition angle range) is calculated in a region where the pressure change after the supplied fuel pressure P rises and changes is relatively stable. (# 5). In this case, the control rack (not shown) of the fuel injection pump 5 may be located at any position, but by setting the control rack at the maximum fuel supply amount position and lengthening the effective stroke of the plunger, the average value can be obtained. It is possible to obtain a long angle range and accurately perform the average calculation process.

Next, an operation for linearly approximating the waveform in the region where the supply fuel pressure P rises and changes is performed. In this calculation, a value obtained by subtracting the preset pressure difference from the average value P1 is obtained as the number of points (for example, 6 points) set as the approximate straight-line calculation pressure, and the crankshaft angle for each point is read (# 6). . Next, using the method of least squares, the approximate straight line L in the rising region of the supplied fuel pressure P
Is calculated as follows (# 7).

That is, with the crankshaft angle as the x-axis and the supplied fuel pressure as the y-axis, the sampled 6-point crankshaft angle x and the approximate straight-line calculation pressure y are (x1, y1), (x2, y2), respectively. , (X3, y3), (x4,
y4), (x5, y5), (x6, y6) If the equation of the approximate straight line L is y = kx + y0, the proportional constant k and the y-axis intercept y0 are k = (6 · C1-A2 · C2) / (6 · A1−A2 ² ) y ₀ = (A3 · C2−A2 · C1) / (6 · A1−A2 ² ) Here, A1, A2, C1 and C2 can be obtained from the following equations. A1 = x1 ² + x2 ² + x3 ² + x4 ² + x5 ² + x6 ² A2 = x1 + x2 + x3 + x4 + x5 + x6 C1 = x1 ・ y1 + x2 ・ y2 + x3 ・ y3 + x4 ・ y4 + x5 / y5 + x6 / y
6 C2 = y1 + y2 + y3 + y4 + y5 + y6

When the approximate straight line L is obtained as described above, the average value P1 is substituted for the y value of the approximate straight line L,
The x value of the approximate straight line L at that time is obtained, and this x value (crankshaft angle) is used as the fuel injection start timing θs (#
8).

The results of the fuel injection start timing measurement test using the above measuring method will be illustrated below. FIG. 6 is a chart showing the measurement conditions, in which the thickness of the gasket shim 21 is changed to four types (0.5 mm, 0.55 mm, 0.6 mm, 0.75 mm) and the supply fuel pressure is in the range of 28 to 32 kgf / cm ² . I am changing it in 3 steps. Further, FIG. 5 shows the measured data of the fluctuation waveform of the supplied fuel pressure, and FIG. 6 shows the test result. For reference, the conventional visual measurement is also performed at the same time. For this visual measurement, the transparent tubular portion 29 provided in the fuel recovery conduit 28 is visually observed in FIG. The fuel injection start timing is the time when it is confirmed that the flow of 3 to 3 drops has started to flow, and the data in FIG. 6 is the average obtained by performing visual measurement a plurality of times under the same conditions.

The test result shows that the fuel supply pressure is 2
It was recognized that automatic measurement accuracy of the fuel injection start timing can be ensured even if the fuel injection rate is changed at 8 to 32 kgf / cm ² . Also, the fuel injection start timing changes by changing the shim thickness,
It was confirmed that the variation of the fuel supply pressure waveform was extremely small when the shim thickness was the same.

[0029]

As is apparent from the above description, according to the method of the present invention, the operator only performs the detaching operation of the measuring instrument or the assist thereof, and all the measurement calculations are automatically performed. The time required for measurement per unit is short,
Even if it is introduced inline, the number of workers for measurement can be reduced. Moreover, since the measurement itself does not include human factors, highly accurate measurement is possible, which is effective for improving the quality and stabilizing the quality of the engine.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a measurement structure for carrying out the method of the present invention.

FIG. 2 is a vertical sectional view showing a part of a fuel injection pump.

FIG. 3 is a diagram showing a fluctuation waveform of supply fuel pressure.

[Figure 4] Chart showing the conditions of measurement test

FIG. 5 is a diagram showing fluctuation waveforms of the supplied fuel pressure actually measured under various conditions.

FIG. 6 is a chart showing the results of measurement tests.

FIG. 7 is a basic flowchart for detecting fuel injection start timing.

FIG. 8 is a diagram illustrating a piston top position detecting means.

FIG. 9 (a) The theoretical fluctuation waveform of the supplied fuel pressure (B) Actual fluctuation waveform of supplied fuel pressure

[Explanation of symbols]

1 crankcase 2 crankshaft 5 Fuel injection pump P Fuel supply pressure P1 average value L approximate straight line θ Crankshaft angle θs Crankshaft angle (fuel injection start timing)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kengo Adachi             64 Ishizukitamachi, Sakai City, Osaka Prefecture Kubo Co., Ltd.             Ta Sakai Factory (72) Inventor Kimihiro Yoshida             64 Ishizukitamachi, Sakai City, Osaka Prefecture Kubo Co., Ltd.             Ta Sakai Factory (72) Inventor Hisao Tsujii             64 Ishizukitamachi, Sakai City, Osaka Prefecture Kubo Co., Ltd.             Ta Sakai Factory F-term (reference) 3G084 BA15 CA00 DA21 DA27 FA17                       FA38

Claims (3)

[Claims] 1. A fuel injection pump mounted on a crankcase, wherein a crankshaft is rotated by an external power in a state where fuel is pumped at a predetermined pressure, and a change in supplied fuel pressure near a fuel injection start timing is measured by a crankshaft angle. The method for measuring the fuel injection start timing of an engine, characterized by measuring the fuel injection start timing by automatically analyzing the detected data. 2. The fuel injection start timing measuring method for an engine according to claim 1, wherein the fuel injection start timing is measured by analyzing a waveform of the supplied fuel pressure in the vicinity of the fuel injection start timing. 3. The crankshaft angle at the intersection of the approximate straight line of the rising region of the supplied fuel pressure and the average straight line of the pressure stable region after rising is used as the fuel injection start timing. Engine fuel injection start timing measurement method.