JPH04109072A - Fuel injection timing inspecting device for fuel injection pump - Google Patents

Abstract

PURPOSE:To improve the accuracy of inspection by injecting high pressure fuel from a fuel sump to a passage and from the passage into a fuel pressure chamber so as to generate cavitation, and detecting shock waves generated in association with the generation of this cavitation. CONSTITUTION:In order to detect the fuel injection timing, a supporting plate 39 is moved downward first to connect the connecting part 40a of a connecting pipe 40 to the delivery valve 10 of a fuel injection pump P. Secondly, high pressure fuel is supplied into the fuel injection pump P from a high pressure fuel supply means 37, and the fuel supplied into the fuel sump part of the fuel injection pump P is let flow into a fuel pressure chamber through an intake/ exhaust port and then returned into a fuel tank through the delivery valve 10, the connecting pipe 40, a check valve 47 and a discharge pipe 48. Shock waves, generated at this time in association with cavitation generated in the fuel pressure chamber, is detected by an AE sensor 44, and this shock wave detection signal AE is inputted into a microcomputer 49. When this shock wave detection signal AE is changed into the low state from the high state, it is judged that the intake/exhaust port is shielded and fuel injection is started.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to the fuel injection timing (in this specification, the fuel injection timing refers to The present invention relates to an inspection device for inspecting fuel injection start timing and/or fuel injection end timing.

[Prior Art] The fuel injection timing of a fuel injection pump, that is, the fuel injection start timing and the fuel injection end timing, have a large influence on engine performance. Therefore, regarding each fuel injection pump,
It is checked whether the actual fuel injection timing matches the set fuel injection timing.

Conventional inspection equipment used for such inspections includes:
For example, there is one described in Japanese Utility Model Application Publication No. 56-121121. The inspection device included in this publication supplies fuel to the fuel injection pump while rotating the camshaft of the fuel injection pump, and at the same time drips fuel from a nozzle connected to the fuel injection pump, interrupting the dripping of fuel. Then, the fuel injection timing is inspected by restarting the engine.

In other words, the fuel injection pump is equipped with a plunger that reciprocates following the rotation of the camshaft, and when the plunger moves forward (pressurizing movement), it closes the passage that communicates the fuel reservoir and the fuel pressurizing chamber. , substantial pressurization by the plunger begins, and thus fuel injection begins. Thereafter, when the plunger opens the passage, fuel in the fuel pressurization chamber flows out through the passage and into the fuel reservoir. Therefore, the fuel pressurization by the plunger ends, and the fuel injection ends.

When inspecting the injection timing of such a fuel injection pump, low-pressure fuel is supplied to the fuel reservoir, a nozzle is connected to the fuel pressurizing chamber, and the camshaft is rotated in this state to cause the plunger to reciprocate. . At the beginning of the plunger's forward movement, the passage is open. Therefore, the fuel supplied to the fuel reservoir reaches the nozzle via the passage and the fuel pressurizing chamber and is dripped from there. When the passage is closed as the plunger moves forward, fuel is prevented from flowing from the fuel reservoir into the fuel pressurizing chamber, and as a result, dripping of fuel from the nozzle is interrupted. The fuel injection start timing is determined from the rotational position of the camshaft at the time when fuel dripping is interrupted. When the plunger moves further and the passage is reopened, dripping from the nozzle resumes. The fuel injection end timing is determined from the rotational position of the camshaft at the time of restart.

Note that the interruption and resumption of dripping of fuel from the nozzle is detected visually or by photoelectric inspection means.

[Problems to be Solved by the Invention] The injection timing inspection device as described above has a problem of low inspection accuracy.

That is, when dropping is interrupted, the interval between drops gradually becomes longer and then stops.

There are individual differences in the determination of this interval, that is, the determination of when to start fuel injection, and the repetition accuracy is also poor. These results in measurement errors. Although this error is small, the detection accuracy of the fuel injection start timing needs to be within ±2' in terms of the rotation angle of the camshaft. The conventional inspection apparatus described above has a problem in that it cannot achieve such high precision.

Note that, of course, there is a similar problem in measuring the injection end timing.

The present invention was made to solve the above problems, and an object of the present invention is to provide a fuel injection timing inspection device that can measure the fuel injection timing of a fuel injection pump with high accuracy.

[Means for Solving the Problems] In order to achieve the above object, the present invention prevents fuel pressurization by the plunger when the passage communicating between the fuel reservoir and the fuel pressurization chamber is closed during pressurization movement of the plunger. In a fuel injection timing inspection device that inspects the fuel injection timing of a fuel injection pump in which pressurization of fuel by the plunger ends when the passage is opened, the fuel injection timing is inspected by supplying high-pressure fuel to the fuel reservoir. A high-pressure fuel supply means that causes the fuel to flow from the fuel reservoir into the fuel pressurizing chamber through the passage to generate cavitation in the passage or in the fuel pressurizing chamber, and detecting a shock wave generated due to the occurrence of the cavitation. The present invention is characterized by comprising a detection means.

[Operation] While supplying high-pressure fuel to the fuel reservoir, the camshaft of the fuel injection pump is rotated to move the plunger under pressure. At the beginning of the pressurization movement, the passage is open, so the fuel in the fuel reservoir flows into the fuel pressurizing chamber through the passage, and as a result, cavitation occurs within the passage or within the fuel pressurizing chamber. A shock wave is generated as it occurs.

A detection means detects this shock wave.

When the passage is closed as the plunger moves forward, fuel is prevented from flowing from the fuel reservoir into the fuel pressurizing chamber via the passage, so cavitation no longer occurs and the shock wave disappears. A detection means detects disappearance of the shock wave. The fuel injection start timing can be determined from the rotational position of the camshaft when this shock wave disappears.

When the plunger moves further forward and the passage is reopened, cavitation occurs again and a shock wave is generated. A detection means detects the generation of this shock wave. From the rotational position of the camshaft at the time of this detection, it can be determined whether it is time to end fuel injection.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

First, to briefly explain the fuel injection pump that is the object of inspection by this inspection device, the size-type fuel injection pump P shown in FIG. The same number of cylinders (six in this case) are formed.

A cylindrical barrel 3 is inserted into the upper end of the through hole 2 . A fuel reservoir 4 is formed between the outer circumferential surface of the intermediate portion of the barrel 3 and the inner circumferential surface of the intermediate portion of the through hole 2 . Fuel is supplied to the fuel reservoir 4 via a joint 5.

Further, a plunger 6 is slidably and rotatably inserted into the barrel 3. This blanket 6 reciprocates following the rotation of the camshaft 7 and pressurizes the fuel in the fuel pressurizing chamber 8, and the forward movement (pressurizing movement) of the plan/middle 6
At times, when the plunger 6 closes the supply/discharge hole (passage) 9 formed in the barrel 3, the fuel pressure chamber 8, which was communicating with the fuel reservoir 4 via the supply/discharge hole 9, or the fuel reservoir 4 is It is blocked against. As a result, the fuel in the fuel pressurizing chamber 8 is pressurized as the blanket 6 moves forward.

The pressurized fuel is fed under pressure to a fuel injection nozzle (not shown) through the delivery valve 10 and a high-pressure pipe (not shown) connected to the delivery valve IO, and from there into the combustion chamber of the engine. Injected.

When the plunger 6 further moves forward and the passageway 11 formed on the outer circumferential surface of the plunger 6 faces the supply/discharge hole 9, a fuel pressurizing chamber 8 is formed in the vertical groove formed on the outer circumferential surface of the plunger 6. It communicates with the fuel reservoir 4 via a (passage) 12, a lead 11, and a supply/discharge hole 9.

As a result, the high-pressure fuel in the fuel pressurizing chamber 8 begins to flow into the fuel reservoir 4, and substantial fuel pressurization by the plunger 6 ends, thereby ending fuel injection.

When the plunger 6 moves backward, the fuel in the fuel reservoir 4 is sucked into the fuel pressurizing chamber 8 through the supply/discharge hole 9.

Further, a control sleeve 13 is fitted to the lower end of the plunger 6 in a non-rotatable but relatively slidable manner, and when the control sleeve 13 is appropriately rotated by a control rod 14, The location of the reed 11 facing the supply/discharge hole 9 changes, thereby adjusting the fuel injection end timing and, in turn, the fuel injection amount.

Next, an inspection device for measuring the fuel injection timing of the fuel injection pump P having the above configuration will be explained.

FIG. 2 schematically shows the overall configuration of the inspection apparatus according to the present invention.
is installed. The fuel injection pump P is placed on this X-Y table 32, and by adjusting the X-Y table 32 appropriately, the fuel injection pump P can be moved in the left-right direction (X-
The position in the X direction) and the position in the front-rear direction (Y-Y direction) are adjusted.

The camshaft 7 of the fuel injection pump P whose position has been adjusted is connected to the camshaft 7 via a surfomotor 33 or a reduction gear 34 . Then, the camshaft 7 is moved to 0.0 by the surfomotor 33. lrp
In order to detect the rotation of the camshaft 7, the camshaft 7 is rotated from the reducer 34 to the camshaft 7.
A rotation sensor 35 is placed near any of the locations up to. Further, a lift sensor 36 is attached to the pump body 1 in order to detect the lift amount of the plunger 6 that reciprocates as the camshaft 7 rotates.

Furthermore, a high-pressure fuel supply means 37 is connected to the joint 5 of the fuel injection pump P (see FIG. 1). This high-pressure fuel supply means 37 is for supplying high-pressure fuel to the fuel reservoir 4, and the pressure of the high-pressure fuel to be supplied is set to, for example, about 30 kg/cm. When fuel is supplied to the reservoir 4, if the supply and discharge hole 12 is open, the fuel will be injected into the fuel pressurizing chamber 8 or the board 11 through the supply and discharge hole 12. In particular, if the supply and discharge hole 12 is slightly open, In this state, the fuel in the fuel reservoir 4 is strongly jetted from the supply/discharge hole 12 into the fuel pressurizing chamber 8 or the lead 11, and this jetting causes cavitation in the fuel pressurizing chamber 8 or the lead 11. Note that when cavitation occurs, shock waves are generated accordingly.

Further, a column 38 is erected on the rear side of the X-Y table 32 on the inspection table 31. A support plate 39 is attached to this column 38 so that its position can be adjusted in the vertical direction (Z-Z direction). This support plate 39 extends horizontally forward and is located above the fuel injection pump P, and the support plate 39 has the same number of connection pipes 4 as the delivery valves 10.
0 or each is supported. Each connecting pipe 40 is arranged so that its axis coincides with the axis of the corresponding delivery valve 10. Moreover, each connecting pipe 40 has a vibration-proof bushing 4 fixed to the support plate 39, as shown in FIG.
1, but when a retaining ring 42 provided on the connecting pipe 40 hits the bush 41, it cannot move further downward.

Furthermore, a sensor holder 43 is fixed to the lower end of the connecting tube 40. Inside this sensor holder 43, there is an AE (
A foustic emission) sensor 44 is housed therein. As is well known, the AE sensor 44 is made of piezoelectric ceramic or the like, and is pressed into contact with the outer peripheral surface of the connecting tube 40 by a spring 45. When the shock wave is transmitted to the connecting pipe 40, a voltage is generated depending on the magnitude of the shock wave.

A spring 46 is arranged between the sensor holder 43 and the support plate 39. The connecting tube 40 is urged downward by the urging force of the spring 46, and the retaining ring 42 abuts against the bushing 41. However, if the support plate 39 is moved downward to abut against the delivery valve IO and then moved further downward, the connection pipe 40 will stop, while only the support plate 39 will move downward. As a result, the connecting pipe 40 is moved by the urging force of the spring 46 to the delivery valve lO.
will be brought into pressure contact with. In this case, the contact pressure of the connecting pipe 40 with respect to the delivery valve 10 is
Support plate 3 after 0 contacts delivery valve 10
It increases according to the moving distance of 9.

Note that a tapered connection hole 10a (this connection hole 10a communicates with the fuel pressurizing chamber 8) is provided in the upper end surface of the delivery valve 10 so that the delivery valve 10 and the connection pipe 40 are in close contact with each other. On the other hand, a spherical connecting portion 40a is formed on the lower end surface of the connecting tube 40. The connection hole lOa and the connection portion 40a are in annular line contact.

Further, a discharge pipe 48 is connected to the upper end of the connecting pipe 40 via a check valve 47, and the fuel discharged from the delivery valve 10 is sent to a fuel tank (not shown) via the discharge pipe 48. It is set to be returned.

Further, in order to calculate the fuel injection start timing and fuel injection end timing of the fuel injection pump P, this inspection device uses a microcomputer (hereinafter abbreviated as "Myfun").

) 49. The microcomputer 49 receives a rotation signal N indicating the rotation speed of the camshaft 7 from the rotation sensor 35, a lift signal indicating the lift amount of the plunger 6 from the lift sensor 37, and a lift signal N indicating the lift amount of the plunger 6 from the AE sensor 44. The voltage shock wave detection signal AE is manually generated.

Next, a case where the fuel injection start timing and fuel injection end timing are detected by the inspection device having the above configuration will be described.

First, the fuel injection pump P is placed on the XY table 32, and adjusted so that the axis of each delivery valve 10 coincides with the axis of the connecting pipe 40, respectively.

Thereafter, the support plate 39 is moved downward to bring the connecting portion 40a of the connecting pipe 40 into pressure contact with the connecting hole 10a of the delivery valve 10, thereby connecting the connecting pipe 40 to the fuel injection pump P.

Next, while high pressure fuel is supplied to the fuel reservoir 4 by the high pressure fuel supply means 37, the camshaft 7 is rotated at a low speed by the servo motor 40. Then, as the camshaft 7 rotates, each of the six plungers 6 reciprocates.

It is now assumed that the - plunger 6 of the six plungers 6 begins to move forward. - At the beginning of forward movement of the blanket 6, the supply/discharge hole 12 is open, and the fuel supplied from the high-pressure fuel supply means 37 into the fuel reservoir 4 passes through the supply/discharge hole 12 and enters the fuel pressurizing chamber 8. From there, it returns to the fuel tank via the tank 1<lub 10, the connecting pipe 40, the check valve 47 and the discharge pipe 48.

As the plunger 6 moves forward, the supply/discharge hole 12 gradually closes and its open area decreases. Since the pressure of the fuel supplied to the fuel reservoir 4 is high, the fuel is pressurized from the supply/discharge hole 4. Fuel is powerfully ejected into the chamber 8. This ejection generates a cavity 79 in the fuel pressurizing chamber 8. Shock waves are generated along with the generation of this cavity. This shock wave propagates to the connection pipe 40 via the delivery valve 10 and is detected by the AE sensor 44. AE sensor 44
The shock wave detection signal AE is input to the microcomputer 49.

When the supply/discharge hole 12 is completely closed due to the forward movement of the blanket 6, no fuel is injected from the supply/discharge hole 12 into the fuel pressurizing chamber 8 (this eliminates the occurrence of cavity condensation. Of course, shock waves also occur. It will no longer occur.

Therefore, the detection signal AE from the AE sensor 44 is also zero (
low).

The microcomputer 49 detects the supply/discharge hole 1 when the detection signal AE from the AE sensor 44 changes from a high state to a low state.
If it is 2, it is determined that it has been shielded, and it is determined that fuel injection has started. Then, the cam angle at the fuel injection start time is calculated from the lift signal at that time.

The plunger 6 further moves forward, connecting the supply/discharge hole 12 and the lead il.
At the same time as the two begin to face each other, high-pressure fuel in the fuel reservoir 4 is ejected from the supply/discharge hole 12 into the lead 11. As a result,
A cavity is generated within the lead 11, and a shock wave is generated. Therefore, the detection signal of the AE sensor changes from a low state to a no state. Microcomputer 49 is AE
When the detection signal AE from the sensor 44 changes from the low state to the no state, it is determined that the fuel injection has ended, and the cam angle is adjusted based on the lift signal at that time or the cam angle at the fuel injection start timing. The cam angle at the fuel injection end time is calculated based on the rotation signal N at the fuel injection end time.

Furthermore, the microcomputer 49 uses the cam angle at the fuel injection start timing of the minus plunger 6 as a reference for the fuel injection start and end timing based on the forward movement of the other plungers 6, and detects the detection signals from the other AE sensors 44. The cam angle at the fuel injection start timing is calculated from the output signal N of the rotation sensor 35 when changing from the low state to the high state.

Similarly, the fuel injection end timing is calculated from the output signal N of the rotation sensor 35 when the detection signal AE changes from a high state to a low state.

The fuel injection start timing and fuel injection end timing calculated by the microcomputer 49 are displayed on a display device (not shown) or printed by a printing device (not shown).

The above-mentioned fuel injection timing inspection device detects the shock wave caused by the occurrence of cavities, and determines the fuel injection start time when the detection signal changes from a low state to a low state, and when the detection signal changes from a low state to Since the end time of fuel injection is determined when the state of ``no'' or ``e'' is reached, the fuel injection timing can be detected more accurately than the conventional detection based on dripping of fuel.

Incidentally, in the conventional detection method, the detection accuracy of the fuel injection timing was at most ±5' in terms of cam angle, but with this inspection device, the detection accuracy could be improved to within ±2'. In addition, inspection time was also significantly reduced.

Note that, since the fuel injection pump P is provided with six plungers 6, the shock waves based on the other plungers 6 are also input to the AE sensor 44, which measures the shock waves based on the minus plunger 6. However, the shock waves generated by the forward movement of the other plungers 6 are attenuated at many fitting points before reaching the AE sensor 44 corresponding to the - plunger 6. smaller than the shock wave based on Therefore, if a certain threshold value is set for the detection signal AE input to the microcomputer 49 and signals lower than this are cut, shock waves other than those to be measured can cause incorrect fuel injection timing. It is possible to prevent judgment from occurring.

Further, the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the gist thereof.

For example, the inspection device of the present invention can be applied not only to the above fuel injection pump P, but also to other types of fuel injection pumps.

For example, the fuel injection pump shown in FIG. 4 is similar to the above-mentioned fuel injection pump P in that it is a side-type fuel injection pump, but in this fuel injection pump, a timing sleeve 17 is slidably attached to the outer periphery of the plunger 16. and are fitted so as to be relatively rotatable. The plunger 16 has a hole 16a that is opened at one end in the upper end surface facing the fuel pressurization chamber 8 and the other end is opened in the outer circumferential surface as a passage for communicating the fuel reservoir 4 and the fuel pressurization chamber 8. A vertical groove 16b extends upward from an opening in the outer peripheral surface of 16a.

and a lead 16C extending spirally from this vertical groove 16b.
is formed. On the other hand, a spill port 17a is formed in the timing sleeve 17 as a passageway, passing through the timing sleeve 17 from its outer peripheral surface to its inner peripheral surface.

In the fuel injection pump having the above configuration, when the hole 16a is blocked by the timing sleeve 17 when the plunger 16 moves forward, the plunger 16 starts pressurizing the fuel, and when the lead 16C faces the spill port 17a, fuel injection ends. do.

When inspecting the fuel injection timing, the hole 16a is gradually covered by the timing sleeve 17, and as its open area becomes smaller, the high-pressure fuel in the fuel reservoir 4 is injected into the hole 16a from the small open portion. As a result, cavitation occurs within the hole 16a. Thereafter, when the hole 16a is completely covered by the timing sleeve 17, cavitation will no longer occur. Further, after the hole 16a is blocked by the timing spill 17, the lead 16
When C begins to face the spill port 17a, fuel is spouted from the spill port 17a to the lead 16c, and the lead 16
Cavitation occurs within C. Therefore, similarly to the above embodiment, the fuel injection start timing can be detected by detecting the shock wave accompanying the occurrence of cavitation.

Further, the fuel injection pump shown in FIG. 5 is a distribution type fuel injection pump. As is well known, this fuel injection pump
The plunger 26 rotates and reciprocates, and when the inlet slit 26a separates from the inlet port 23a of the barrel 23 when the plunger 26 moves forward, the fuel in the fuel pressurizing chamber 28 is pressurized and fuel injection starts. do. Note that the pressurized fuel is discharged from the vertical hole 26b1 horizontal hole 26C and outlet slit 26d to the discharge port 23b.
The fuel is discharged into the fuel injection nozzle through a delivery valve (not shown).

The plunger 26 moves further forward, and its cut-off port 26e moves from the control sleeve 27 to the pump chamber 24 (
When exposed to a fuel pool (fuel puddle), fuel injection is terminated.

As is clear from the above content, in this fuel injection pump, the inlet port 23a1, the inlet slit 26a, the vertical hole 24b, and the cutoff port 26e constitute a passage that communicates the pump chamber 24 and the fuel pressurizing chamber 28. do.

When detecting the fuel injection timing of the fuel injection pump configured in this way, the connecting pipe 4o in the above-described embodiment is connected to the delivery valve in a press-contact state, and high-pressure fuel is force-fed to the pump chamber 24. . and,
The plunger 26 is rotated and reciprocated at low speed.

When the plunger 26 moves forward, the opposing area of the inlet port 23a and the inlet slit 26a is
6, the fuel in the pump chamber 24 is strongly jetted out from the inlet port 23a into the inlet slit 26a. As a result, cavitation occurs within the inlet slit 26a. When the inlet slit 26a is separated from the inlet boat 23a, fuel will no longer be ejected into the inlet slit 26a, and cavity/con will no longer occur. This tells you when it is time to start fuel injection. When the franchisor 26 moves forward further and the cut-off boat 26e begins to open, the fuel in the pump chamber 24 is ejected into the cut-off boat 26e, and cavitation begins to occur within the cut-off boat 26e. This determines when the fuel injection ends.

Further, in the above embodiment, the AE sensor 44 may be provided in the connecting pipe 40 or may be provided in the pump body 1.

[Effects of the Invention] As explained above, according to the fuel injection timing inspection device of the present invention, high-pressure fuel is supplied to the fuel reservoir, and the high-pressure fuel is supplied from the fuel reservoir to the passage or from the passage to the fuel pressurizing chamber. By injecting it, a cavity/con is generated, and the shock wave generated by the generation of this cavity is detected, so inspection accuracy can be greatly improved compared to conventional inspection equipment. Further, effects such as being able to shorten the time required for inspection can be obtained.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, in which FIG. 1 is a schematic configuration diagram showing the main parts, FIG. 2 is an overall configuration diagram with some parts omitted, and FIG. 3 FIG. 4 is a vertical cross-sectional view showing an example of a fuel injection pump that is a target of the inspection apparatus according to the present invention, and FIGS. 4 and 5 are cross-sectional views showing essential parts of other examples of the fuel injection pump. P: fuel injection pump, 4: fuel reservoir, 6: plunger, 8: fuel pressurization chamber, 9: supply/discharge hole (passage),
11... Lead (passage), 12... Vertical a (passage), 1
4.Fuel reservoir, 16..Plunger, 16a.hole (passage), 16b..vertical groove (passage), 16c..leat (
Passage), 17a... - Spill boat (passage), 23a...
Inlet boat (passage), 24 ・Fuel reservoir, 26
・ Branya, 26a... Inlet slit, 26
b... Vertical hole (passage), 26e... Cut-off boat (
passage), 28・fuel pressurization chamber, 37・high pressure fuel supply means,
44・AE sensor.

Claims (1)

[Claims] When the plunger moves under pressure, the plunger starts pressurizing the fuel when the passage that communicates the fuel reservoir and the fuel pressurizing chamber is closed, and when the passage is opened, the plunger stops pressurizing the fuel. In a fuel injection timing inspection device for inspecting fuel injection timing, supplying high-pressure fuel to the fuel reservoir causes fuel to flow from the fuel reservoir into the fuel pressurizing chamber via the passage,
Fuel injection timing of a fuel injection pump characterized by comprising: a high-pressure fuel supply means that generates capitation in a passage or a fuel pressurizing chamber; and a detection means that detects a shock wave generated due to the occurrence of the capitation. Inspection equipment.