JPH0452468Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electronic control unit injector for a diesel engine.

[Conventional technology]

Recently, a unit injector for a diesel engine, which is operated by a plunger that reciprocates following the movement of a cam, has been developed.
It has been developed as shown in the publication, but an electronically controlled version of this is, for example,
It is notified as shown in SAEpaper850542 (Figures 9 and 10).

In FIG. 9, 21 is a unit injector main body, and a spill valve device 23 is provided on the upper part of the unit injector main body. The spill valve device 23 includes a spill valve 24 that controls the supply of fuel from the fuel supply passage 22 and the return of fuel from the fuel return passage 22' by a control means. This control means includes a control unit (not shown) and a solenoid 25 operated by a control signal sent from the control unit, and is configured to close the spill valve 24 for a predetermined period of time. Supplementing this with reference to Fig. 10, a command is given to the solenoid 25 by the control signal a in the ON state from the control unit, the solenoid current flows for a predetermined time b, and after the response delay time has elapsed, the spill valve 24 is closed for a predetermined time. c.

The unit injector main body 21 is provided with a cylinder portion 21A, and a fuel supply passage 22 and a fuel return passage 22' are freely communicated with the cylinder portion 21A. A plunger 26 that reciprocates following the movement of a cam (not shown) is fitted into the cylinder portion 21A, and the unit injector main body 21
A needle valve 27 is provided at the tip.

With the spill valve 24 closed, fuel is sent to the tip of the unit injector body 21 via the fuel supply passage 22, and this fuel is pressurized by the plunger 26 to lift the needle valve 27 for a predetermined time (10th Figure e) Pressurized fuel is injected for a predetermined period of time.

[Problem that the invention attempts to solve]

In the case of a conventional electronic control unit injector, in a low speed range, the injection pressure remains almost constant and does not increase even if the load is increased (as shown in FIG. 11).

However, at high speeds, when the load is increased, the injection pressure increases significantly (Fig. 10d and 12).
(as shown in the figure), there was a problem that excessive pressure was generated and durability deteriorated.

[Purpose of invention]

The present invention was developed to solve the above-mentioned problems, and its purpose is to provide an electronic control unit injector for diesel engines that prevents excessive injection pressure in high-speed ranges and has improved durability. be.

[Means for solving problems]

In order to achieve the above object, the present invention forms a fuel supply passage and a fuel return passage in the unit injector body, and controls the return of fuel from the fuel return passage by a spill valve whose opening and closing are controlled by a control means. A spill valve device is provided in the unit injector body, and a plunger that reciprocates following the movement of the cam is fitted into the unit injector body, and fuel is sent to the tip of the unit injector body via the fuel supply passage, causing spills. An electronic control unit for diesel engines that lifts a needle valve installed at the tip of the unit injector body by pressurizing fuel with a plunger with the valve closed, injects pressurized fuel for a predetermined period of time, and then fully opens the spill valve. At the injector, based on the signals from the engine load sensor and engine rotation sensor,
The present invention is characterized by comprising a control means that calculates the total operating time and the initial valve closing time, opens the closed spill valve by a minute displacement after the initial valve closing time has elapsed, and fully opens the spill valve after the full operating time has elapsed.

[Effect of invention]

According to the present invention, the spill valve device includes a control means that opens the closed spill valve by a small amount of displacement after the initial valve closing time has elapsed, and then fully opens the spill valve. Therefore, the injection pressure of the fuel injected from the nozzle tip is maintained approximately constant.

[Example of idea]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 8 show an electronic control unit injector for a diesel engine according to an embodiment of the present invention.

As shown in FIGS. 1 to 3, a unit injector main body 1 is provided with a spill valve device 2. As shown in FIGS. This spill valve device 2 includes a spill valve 3 and a control means 4. The spill valve 3 controls the return of fuel from a fuel return passage 6 provided in the unit injector body 1. The control means 4 is composed of a control unit 7 and a solenoid 8 operated by a control signal sent from the control unit 7, and opens the closed spill valve 4 by a minute displacement after the initial valve closing time has elapsed, and then fully opens it. It is something that makes you

An engine load sensor 9 and an engine rotation sensor 10 are connected to the control means 7. The above control signal is shown in Fig. 4, and the initial valve closing time t ₂ is
It is a signal that is in the ON state, and then the ON state and OFF state repeat alternately, and the total operating time is t ₁ . The control unit 7 also stores MAP1 shown in FIG. 5 and MAP2 shown in FIG. 6. MAP1 determines the total operating time _t1 according to the engine speed and load,
MAP2 determines the initial valve closing time _t2 based on the engine rotation speed.

Further, the unit injector main body 1 is provided with a cylinder portion 1A, a plunger 11 is fitted into the cylinder portion 1A, and a cylindrical portion 12 is connected to the plunger 11 so as to be freely pressable.
3, it is constantly pressed in the X direction. Cylindrical part 1
2 is driven back and forth following the movement of a cam (not shown), and this movement is directly transmitted to the plunger 11. And cylinder part 1A
A fuel supply passage 5 is connected to the fuel supply passage 5.
is adapted to communicate with an L-shaped hole 11A provided in the plunger 11 when the plunger 11 is in the raised state (the state shown in FIG. 1). A communication passage 14 is provided at the bottom of the cylinder portion 1A, and this communication passage 14 merges with the fuel return passage 6 and connects to the junction point 1.
A merging passage 16 is formed beyond 5.
Further, a needle valve 17 is provided at the tip of the unit injector main body 1.

Initially, as shown in FIGS. 1 and 2, the plunger 11 is in a raised state and the spill valve 3 is fully open. At this time, fuel is supplied from the feed pump (not shown) to the fuel supply passage 5 from the inlet 5A, and through the hole 11A of the plunger 11.
It is introduced into the compression chamber 1B of the cylinder portion 1A, pressurized there, and then introduced into the communication passage 14. However, the fuel guided into the communication passage 14 is transferred to the return passage 6.
through the gap C of the spill valve 3 in the open state.
The fuel escapes to the fuel supply route 5 via the fuel supply route 5.

Then, when the plunger 11 descends and the communication between the fuel supply passage 5 and the L-shaped hole 11A is cut off,
The fuel is pressurized to a higher pressure in the compression chamber 1B, but
Since the spill valve 3 is still open, fuel escapes from the fuel return passage 6 to the fuel supply passage 5.

When the control signal shown in FIG. 4 is sent from the control unit 7 to the solenoid 8 when the spill valve 3 is open as described above and fuel escapes from the fuel return passage 6 to the fuel supply passage 5, its waveform is determined by MAP1 in FIG. 5, MAP2 in FIG. 6, and the flowchart in FIG. To explain this, as shown in FIG. 7, an engine load signal L and an engine rotation speed signal N are input from the engine load sensor 9 and the engine rotation sensor 10 to the control unit 7, and are read (S1, S
2).

Based on the input engine load signal L and engine rotational speed signal N, the total operating time _t1 of one unit of the control signal is read by MAP1 in FIG. 5 (S3). Based on the input engine speed signal N, the initial valve closing time t ₂ of one unit of the control signal is read by MAP2 in FIG. 6 (S4). next,
In S5, it is determined whether _t1 has elapsed. time t ₁
If the time has elapsed, the process advances to S13, the control signal for one unit is turned OFF, and the spill valve 4 is opened.
If the time t ₁ has not elapsed, the process proceeds to S6, where it is determined whether the initial valve closing time t ₂ has elapsed.
If the time _t2 has not elapsed, the process returns to S5. time
When t ₂ has elapsed, it is determined as YES and the process proceeds to S7.
The control signal is turned OFF. Then proceed to S8,
It is determined whether the total operating time t ₁ has elapsed. If time _t1 has elapsed, the process advances to S13. If the time t ₁ has not elapsed, the process advances to S9 and it is determined whether the pulse width interval time t _d has elapsed. time
If t _d has not elapsed, the process returns to S8. When the time _td has elapsed, the process advances to S10, and the control signal is turned ON. Next, in S11, it is determined whether the total operating time _t1 has elapsed. If time t ₁ has elapsed, S1
Proceed to step 3. If time t ₁ has not elapsed, S12
Then, it is determined whether the pulse width time t _d ' has elapsed. If the pulse width time t _d ' has not elapsed, the process returns to S11. If the pulse width time t _d ' has elapsed, the process returns to S7 and the control signal is turned OFF.
In this manner, as shown in FIG. 3, after the initial valve closing time t ₂ has elapsed, a square clock pulse wave of pulse width time t _d ' is sent until the total actuation time t ₁ has elapsed.

When a control signal having the waveform shown in FIG. 4 created in the above procedure is sent to the solenoid 8 via a relay (not shown), a solenoid current flows. This solenoid current causes the spin valve 3 to close after the response delay time has elapsed (movement amount h). When the spill valve 3 is closed, the fuel does not return to the fuel return passage 6 but flows to the merging passage 16 via the communication passage 14. Therefore,
The needle valve 17 lifts (Fig. 8e) and fuel injection begins. Of the solenoid currents, the current that flows after the initial valve closing time _t2 has elapsed is (Figure 8b)
As shown in , the current flowing during the initial valve closing time t ₂ is very small. Therefore, the spill valve 4 is configured to open by a small amount after the initial valve closing time _t2 has elapsed, and then to fully open (FIG. 8c). During the entire operating time _t1 during which the spill valve 4 is operating as described above, the needle valve 17 is in a lifted state and fuel is being injected. Therefore, in the low speed range and the high speed range, the injection pressure of the fuel injected from the nozzle tip is no longer in the state shown by the dotted line as in the conventional example, but is maintained almost constant (FIG. 8d).

On the other hand, in the high speed range, the total operating time _t1 becomes smaller due to MAP1 in FIG. 5, and therefore the injection amount becomes smaller. Furthermore, since _the initial valve closing time t ₂ becomes smaller due to MAP2 in _FIG .
t ₂ ) is also longer, contributing to keeping the injection pressure constant. As described above, it is possible to prevent excessive injection pressure in the high speed range and improve durability.

In this embodiment, the control means includes the control unit 7 and the control unit 7.
For example, the control means may be a servo device (often used in robot control) to precisely control the position of the spill valve 3. ) can also be configured.

[Effect of idea]

As described above, according to the present invention, in an electronic control unit injector for a diesel engine, excessive injection pressure can be prevented in a high-speed range, and durability can be improved.

[Brief explanation of the drawing]

Figure 1 is a sectional view of an electronic control unit injector for a diesel engine according to an embodiment of the present invention;
The figure is an enlarged view of part A in Figure 1, Figure 3 is an explanatory diagram of the control means of the electronic control unit injector of the diesel engine, Figure 4 is a waveform diagram of the control signal, and Figure 5 is a complete diagram of the control signal. MAP1 for determining the operating time, MAP2 for determining the initial valve closing time of the control signal, FIG. 7 is a flowchart for determining the waveform of the control signal, and FIG. 8 is an explanation of the operation of the unit injector of the diesel engine. Figure 9 is a sectional view of a conventional electronic control unit injector of a diesel engine, Figure 10 is an explanatory diagram of the operation of the electronic control unit injector of the diesel engine, and Figure 11 is an electronic control of the diesel engine. FIG. 12 is an explanatory diagram of the injection pressure of the unit injector in a low speed range, and FIG. 12 is an explanatory diagram of the injection pressure of the electronically controlled unit injector of the same diesel engine in a high speed range. DESCRIPTION OF SYMBOLS 1... Unit injector body, 1A... Cylinder part, 2... Spill valve device, 3... Spill valve, 4... Control means, 5... Fuel supply passage, 6...
...Fuel return passage, 7...Control unit,
8... Solenoid, 9... Engine load sensor,
10...Engine rotation sensor, 11...Plunger, 11A...L-shaped hole, 14...Communication path, 1
5...merging point, 16...merging passage, _t1 ...total operating time, _t2 ...initial valve closing time.

Claims (1)

[Scope of utility model registration request] A fuel supply passage and a fuel return passage are formed in the unit injector body, and a spill valve device is provided in the unit injector body for controlling the return of fuel from the fuel return passage by a spill valve whose opening and closing are controlled by a control means. A plunger that reciprocates by following the movement of the cam is inserted into the unit injector body, and fuel is sent to the tip of the unit injector body through the fuel supply passage, and with the spill valve closed, the plunger adds fuel. In the electronically controlled unit injector of a diesel engine, the needle valve installed at the tip of the unit injector body is lifted by applying pressure, and after injecting pressurized fuel for a predetermined period of time, the spill valve is fully opened. Equipped with a control means that calculates the total operating time and initial valve closing time based on the signal from the sensor, opens the closed spill valve by a small amount of displacement after the initial valve closing time has elapsed, and fully opens the spill valve after the full operating time has elapsed. An electronic control unit injector for a diesel engine.