JPH0440546B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring fuel injection timing of diesel engines and other engines, and more particularly to a device that allows inspectors at service shops and the like to easily measure fuel injection timing.

As a conventional device for measuring the fuel injection timing of a diesel engine, there is, for example, the one shown in FIGS. 1 and 2 (Japanese Utility Model Application No. 52-42922).

FIG. 1 is an external view of the fuel injection pump. 1st
In the figure, 1 is the injection pump body, 2 is a delivery pipe that sends fuel from the fuel injection pump body 1 to the injection nozzle of each cylinder, 3 is a delivery pipe holder for attaching the delivery pipe 2 to the fuel injection pump body 1, and 4 is a delivery pipe holder for attaching the delivery pipe 2 to the fuel injection pump body 1. This detector detects vibrations caused by pressure changes that occur in the delivery pipe when fuel is injected.

FIG. 2 is a block diagram of the circuit of the fuel injection timing measuring device.

In FIG. 2, 5 is an amplifier that amplifies the signal detected from the detector 4, 6 is a detection circuit that detects the opening timing of the injection nozzle, and 7 is a trigger that causes the discharge light emitter to emit light. A trigger generator 8 generates a signal, and numeral 8 indicates a discharge light emitter that emits light by the output of the trigger generator 7.

Next, its operation will be explained. In a rotating diesel engine, a detector 4 having a unique resonance frequency is attached to the delivery pipe 2 or delivery pipe holder 3 for the first cylinder of the fuel injection pump 1. The detector 4 picks up vibrations caused by pressure changes that occur in the pipe when fuel is injected at high pressure. The output voltage of the detector 4 due to this vibration is amplified by the amplifier 5, and the detection circuit 6 detects a signal corresponding to the injection timing. The trigger generator 7 is
The detection circuit 6 receives the output and generates a trigger signal for causing the discharge light emitter 8 to emit light at the fuel injection timing. A discharge light emitting device 8 filled with rare earth-added active gas such as neon or xenon emits light in response to the trigger signal. The person measuring the first cylinder top dead center mark engraved on a rotating part such as the flywheel of the engine or the mark at the start of fuel injection should be used with the discharge emitter 8.
By irradiating the mark with a flashing light, the mark is observed in a stationary state, and the appropriateness of the injection timing is determined based on the positional relationship with the alignment mark fixed on the engine block side.

However, with the conventional fuel injection timing measuring device as described above, it is possible to measure in-line fuel injection pumps normally used in truck engines, etc., but it is possible to measure the distributed fuel injection timing normally used in passenger car engines. The problem with injection pumps is that they cannot be measured.

In other words, the conventional devices shown in FIGS. 1 and 2 are supposed to detect pressure changes in the delivery pipe, but in reality, they detect mechanical vibrations that occur when the valves of the in-line fuel injection pumps are opened. It is detected through a pipe. However, in the case of a distribution type fuel injection pump, there is no mechanism that generates mechanical vibration when the valve is opened, so it was impossible to measure it with the above-mentioned conventional device.

The present invention was made to solve the above problems, and regardless of the type of fuel injection pump,
It is an object of the present invention to provide a device that can accurately measure fuel injection timing.

In order to achieve the above object, in the present invention,
A vibration detector is installed in the spill tube connected to the injection nozzle to return excess fuel to the fuel injection pump, and vibrations caused by injection when the injection nozzle is opened are detected, thereby measuring the combustion injection timing. It is composed of

The present invention will be explained in detail below based on the drawings.

FIG. 3 is a diagram showing one embodiment of the present invention, and is a diagram showing a mounting location of a vibration detector.

In Fig. 3, 9 is the engine body, 10A~
10F is an injection nozzle provided in each cylinder, 11 is a fuel injection pump, 12 is a delivery pipe, and 13 is in communication with each injection nozzle 10A to 10F in order to return excess fuel to the fuel injection pump 11. The spill tube 14 is a vibration detector attached to the spill tube 13, and 15 is a lead wire for taking out the signal of the vibration detector 14 to the outside.

When the vibration detector 14 is attached to the spill tube 13 as described above, when fuel is injected into the cylinder at high pressure from the injection nozzles 10A to 10F, the injection vibration that occurs in the injection nozzle can be detected via the spill tube 13. I can do it. Note that the spill tube 13 is usually formed of a hard tube such as brass, and is suitable for transmitting high frequency vibration components of 90 kHz or more, as will be described in detail later.

At the time of inspection, the vibration detector 14 can be attached to the spill tube 13 by screwing, clipping, or the like.

Figure 4 is a comparison diagram of vibration waveforms, and (A) is a comparison diagram of vibration waveforms when a distributed fuel injection pump is used.
When the vibration detector is attached to the spill tube as shown in the diagram, (B) is when it is attached to the delivery pipe holder (3 in Figure 3), and (C) is the delivery pipe near the fuel injection pump (2 in Figure 1). The waveform when installed is shown below.

Also, S ₁ is the cutoff frequency for the vibration detector signal.
The waveform is passed through a 90kHz high-pass filter.
_S2 is the output waveform of the lift sensor that detects the open state of the injection nozzle. This lift sensor was previously installed in the injection nozzle for comparison.

In the waveforms shown in FIG. 4, the rising time t ₀ of the output waveform S ₂ of the lift sensor indicates the opening timing of the injection nozzle, that is, the fuel injection timing.

As shown in Fig. 4, when a vibration detector is attached to the spill tube in (A), the signal output start point of the vibration detector coincides with time _t0 , so
Even when a distributed fuel injection pump is used, the fuel injection timing can be detected accurately.

However, in cases (B) and (C), the signal from the vibration detector is detected before time _t0 , and no particular change is observed in the signal level at time _t0 . Therefore, when using a distributed fuel injection pump,
If the vibration detector is attached to the delivery pipe or delivery pipe holder, it is impossible to accurately detect the fuel injection timing.

Next, FIG. 5 is a block diagram of one embodiment of the fuel injection timing measuring device of the present invention. Further, FIG. 6 is a signal waveform diagram of the apparatus shown in FIG. 5, and S ₃ to _{S 10} indicate signal waveforms at portions with the same reference numerals in FIG. 5, respectively.

In FIG. 5, the vibration detector 14 is attached to the spill tube 13, but for example, as shown in FIG. 3, it is attached near the injection nozzle 10A of the first cylinder.

The signal S ₃ of the vibration detector 14 is amplified by an amplifier 16 and filtered by a filter 17 (e.g. cut-off frequency
After passing through a high-pass filter (90k to 100kHz, or a combination of that filter and a low-pass filter with a cutoff frequency of 200k to 400kHz),
It is detected by the wave detector 18 and becomes a signal _S4 .

The comparator 19 outputs a signal _S5 that is at a high level while the signal _S4 is equal to or higher than the reference value _V1 .

The comparator 20 also receives the signal S ₃ (actually the amplifier 1
6 and the value after passing through filter 17) is the reference value V ₂
During the above period, a signal _S6 that remains at a high level is output.

As mentioned above, since the vibration detector 14 is installed near the injection nozzle 10A of the first cylinder,
The level of the signal _S3 is higher during the first cylinder injection than in other cases. Therefore, by appropriately setting the comparison level of the comparator 20, the signal _S6 can be sent out only when the first cylinder is injected, thereby making it possible to detect the first cylinder injection. I can do it.

Next, the counting circuit 21 counts the signal _S5 , and outputs a high level signal when the count reaches 6 (in the case of a six-cylinder engine), and is reset at the fall of the signal _S6 . Therefore, the rise of the signal _S7 of the counting circuit 21 corresponds to the fuel injection timing of the first cylinder.

Next, the variable delay circuit 22 converts the signal S ₇ into a delay time τ ₁
outputs a signal _S8 delayed by . This delay time τ ₁ can be changed by the inspector's operation.

The reason why the delay time τ ₁ is provided in this manner is to delay the light emission timing of the light emitter from the fuel injection timing in order to align it with the compression top dead center of the first cylinder.

The light emitter 23 emits light in response to the above signal _S8 .

On the other hand, the delay time measuring circuit 24 measures the time span from the rising edge of the signal S ₇ to the rising edge of the signal S ₈ , that is, the delay time τ ₁ , and measures the corresponding signal S ₉
Output.

Further, the period measuring circuit 25 measures the period of the signal S ₇ , that is, the period τ ₂ of two revolutions of the crankshaft, and outputs a signal S ₁₀ corresponding to the period τ 2 .

Next, the arithmetic circuit 26 inputs the signals _S9 and _S10 ,
By calculating θ=τ ₁ /τ ₂ ×720°, a signal indicating the delay amount, that is, the fuel injection timing is before the first cylinder compression top dead center, is output, and the display device 27 displays the angle. Display.

Next, a method for measuring fuel injection timing using the above device will be explained.

The inspector first attaches the vibration detector 14 to the spill tube 13 near the injection nozzle of the first cylinder and starts the engine.

Then, by illuminating the top dead center mark of the first cylinder engraved on a rotating part such as the flywheel with flashing light from the light emitter 23, the top dead center mark can be observed while the engine is stationary. The delay time τ ₁ is adjusted by operating the variable delay circuit 22 until the mark appears directly opposite the alignment mark fixed on the block side.

The angle θ shown on the display device 27 when adjusted as described above becomes a value indicating the fuel injection timing as an angle before the first cylinder compression top dead center.

In addition, a sensor detects the compression top dead center of the first cylinder, and the time τ ₀ (corresponding to the above τ ₁ ) from the rising point of the signal S ₇ to the time when the sensor signal is output (top dead center) is measured. circuit and engine speed N
(rpm) and a circuit to calculate θ=N/60×360×τ ₀ , the fuel injection timing can be detected immediately without the need for mark alignment, etc. It is possible to reduce the number of outputs.

If the top dead center timing can be detected by the top dead center sensor, the time interval between the injection start time (rise of S ₇ ) and the top dead center sensor output will be automatically detected, and the time interval between the top dead center sensor output and the engine speed at that point will be detected. It is possible to calculate the crank angle.

As explained above, according to the present invention, the vibration detector attached to the spill tube is used to detect high-frequency injection vibrations that occur when fuel is injected into the cylinder from the injection nozzle. The timing of fuel injection can be accurately detected without being disturbed by other vibrations of the engine, and the calculation display means can display the fuel injection timing expressed as an angle before compression top dead center. Since the fuel injection timing is calculated and displayed, the fuel injection timing can be detected accurately and easily, and the number of inspection steps can be significantly reduced, which is an excellent effect.

[Brief explanation of drawings]

Fig. 1 is an external view of a fuel injection pump, Fig. 2 is a block diagram of an example of a conventional measuring device, Fig. 3 is an embodiment of the present invention and shows the installation location of a vibration detector, Fig. 4 5 is a signal waveform diagram of the vibration detector, FIG. 5 is a block diagram of an embodiment of the measuring device of the present invention, and FIG.
The figure is a signal waveform diagram of the apparatus of FIG. 5. Explanation of symbols 1...Fuel injection pump body, 2...
Delivery pipe, 3...Delivery pipe holder,
4...detector, 5...amplifier, 6...detection circuit,
7...Trigger generator, 8...Discharge light emitter, 9...
Engine body, 10A to 10F... injection nozzle,
11... Fuel injection pump, 12... Delivery pipe, 13... Spill tube, 14... Vibration detector, 15... Lead wire, 16... Multiplier, 17...
...Filter, 18...Detector, 19...Comparator,
20...Comparator, 21...Counting circuit, 22...Variable delay circuit, 23...Light emitter, 24...Delay time measurement circuit, 25...Period measurement circuit, 26...Arithmetic circuit, 27...Display Device.

Claims (1)

[Scope of Claims] 1. A vibration detector attached near the injection nozzle of a specific cylinder of a hard pipe spill tube connected to the injection nozzle as a path for returning excess fuel to the fuel injection pump; a high-pass filter having a cut-off frequency of approximately 90 KHz or higher for filtering the output signal of the high-pass filter; and calculation display means for calculating and displaying the fuel injection timing from the output signal of the high-pass filter, and the calculation display means comprising: Means for detecting the point in time when the injection nozzle of the specific cylinder injects from the signal of the high-pass filter, and outputting a first signal at each point of time, and a second signal at the point in time when the specific cylinder reaches compression top dead center. means for outputting the above first
means for detecting _the time interval τ ₀ between the signal _of and a means for displaying the above-mentioned θ, that is, the fuel injection timing of a specific cylinder expressed as an angle before compression top dead center, which occurs when fuel is injected from the injection nozzle into the cylinder. A fuel injection timing measurement device for an engine, which detects a high frequency component of injection vibration via a spill tube, and calculates and displays the fuel injection timing expressed as an angle before compression top dead center based on the detected high frequency component.