JPH02157472A - Fuel injection device - Google Patents

Abstract

PURPOSE:To improve a combustion characteristic by providing a solenoid valve in a passage connecting a pressure feeding pump chamber to a discharge gallery, providing a drain port in a position corresponding to an injection finishing timing in a pressure receiving chamber in which an injection plunger slides and forming a passage to the solenoid valve therefrom. CONSTITUTION:As an injection plunger 31 opens the drain port 23 of a pressure receiving chamber 32 with progress in fuel injection, pressure in a pressure feeding pump chamber 18 leaks into a discharge gallery 7 lowering the pressure. Synchronized with this timing, a solenoid valve 50 is changed from a closed condition to an open condition. Thereupon, the fuel in the chamber 18 leaks into the discharge gallery 7 via the valve 50, to rapidly lower the pressure in the chamber 18. Also, since the port 23 is connected to the valve 50 through a passage 26, the pressure of fuel discharged out of the port 23 is added as the acting force on the opening action of the valve 50, accelerating the opening action of and instantaneously opening the valve 50 while suddenly reducing the pressure in the pressure feeding pump chamber 18 and an injection pump chamber 33 as well as injection pressure to make the damping of injection rate at the time of finishing injection steep.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a fuel injection device for supplying fuel to a diesel engine.

[Prior art]

In recent years, in order to improve the combustion characteristics of diesel engines, it has been required to increase the fuel injection pressure. For this purpose, hydraulic pressure is generated by a pressure-feeding plunger operated in synchronization with the engine, and this hydraulic pressure drives the injection plunger.The injection plunger pressurizes the fuel introduced into the injection pump chamber in advance to a high pressure, and the high-pressure fuel A device is being considered that injects the liquid from an injection nozzle at high pressure. Among these, there is a type in which the end of injection is controlled by a drain port formed in a pressure receiving chamber connected to the pressure pump chamber being opened by movement of the injection plunger to leak the pressure in the pressure pump chamber.

[Problem to be solved by the invention]

However, in the above device, when the drain port is opened and the pressure in the pressure pump chamber decreases, the pressure in the injection pump chamber is high, so the injection plunger moves toward the pressure pump chamber, i.e.
It moves in the direction of blocking the drain port and prevents the pressure drop in the pressure pump chamber. As a result, the pressure in the pressure pump chamber and, therefore, the pressure in the injection pump chamber decreases slowly, resulting in deterioration of combustion characteristics and an increase in driving load on the pressure plunger. The present invention has been made to solve the above problems, and aims to improve combustion characteristics and reduce the driving load of the pressure-feeding plunger by sharply reducing the injection rate at the end of injection. . [Means for Solving vAa] The configuration of the invention for solving the above problem is to pressurize the fuel in the pressure pump chamber with a pressure plunger driven in synchronization with the engine, and use the hydraulic pressure generated in the pressure pump chamber to pressurize the fuel in the pressure pump chamber. In a fuel injection device that operates an injection plunger to pressurize fuel in an injection pump chamber and inject it from an injection nozzle, a pressure pump chamber is formed in a passage connecting a pressure pump chamber and a discharge gear gallery by an opening/closing operation. A pressure receiving chamber is provided with an electromagnetic valve that controls injection by leaking or closing fuel, and the pressure receiving chamber communicates with the pressure pump chamber and the injection plunger slides under pressure.
A drain port is provided at a position corresponding to the injection end time to spill the pressure in the pressure receiving chamber to the discharge gear; A passage is formed from the to the solenoid valve, and the solenoid valve is opened at the end of injection.

[Effect]

During the compression stroke of the pressure plunger, when the solenoid valve changes from the open state to the closed state, the pressure pump chamber is shielded from the discharge gear and its pressure increases. Then, the injection plunger receives the pressure and moves in a direction to pressurize the injection pump chamber, thereby increasing the pressure in the injection pump chamber. As a result, high pressure fuel is injected from the injection nozzle. Next, when the fuel injection progresses and the injection plunger opens the drain port of the pressure receiving chamber, the pressure in the pressure pump chamber leaks to the discharge gear gallery and the pressure decreases. Also, in synchronization with this timing, the solenoid valve is changed from a closed state to an open state. Then, the fuel in the pressure pump chamber is leaked to the discharge gear via this solenoid valve, so the pressure in the pressure pump chamber is rapidly reduced. Further, since the drain port and the solenoid valve are connected through a passage, the pressure of the fuel spilled from the drain port is applied as a force for opening the solenoid valve. As a result, the opening operation of the electromagnetic valve is accelerated in response to this pressure and instantaneously becomes open, and the pressure in the pressure pump chamber and the injection pump chamber and the injection pressure are rapidly reduced. In this way, the injection rate attenuates sharply at the end of injection, resulting in good combustion characteristics. Furthermore, the driving load on the pressure-feeding plunger is also reduced.

【Example】

The present invention will be described below based on a specific example. In FIG. 1, 1 is a fuel injection unit, and this unit 1 is fitted into a cylinder rad 2 of a diesel engine, sealed with an 01J ring 3 and a gasket 5, and an annular space is formed between the cylinder rad 2 and the cylinder rad 2. It forms a main gear rally 4. The main components of the unit 1 include a pressure cylinder 11, an injection cylinder 12 connected to the pressure cylinder 11 below the cylinder, a nozzle holder 13, and an injection nozzle 14. By screwing the retaining nut 15 to the outer circumference of one end of the pressure-feeding cylinder 11, the injection cylinder 12 is coupled to the pressure-feeding cylinder 11, and the injection cylinder 12, nozzle holder 13, and injection nozzle 14 are aligned along the axial direction. interconnected. A pressure plunger 17 is slidably inserted into the pressure cylinder 11, and the pressure cylinder 11 and the pressure plunger 17 constitute a pressure pump chamber 18. The pressure-feeding plunger 17 is connected to a cam follower 19, which is in contact with a cam that is synchronized with the rotation of an engine (not shown) and is pushed downward by this cam. A follower spring 20 is mounted between the cam follower 19 and the pressure cylinder 11, and the spring 20 presses the pressure plunger 17 upward to return. Further, an injection plunger 31 is slidably inserted into the injection cylinder 12. A pressure receiving chamber 32 is formed in the upper part of the injection plunger 31, and this pressure receiving chamber 32 communicates with the pressure pump chamber 18. Therefore, when the pressure in the pressure pump chamber 18 increases, the pressure in the pressure receiving chamber 32 also increases, and the injection plunger 31 is pushed downward. Injection plunger 31, injection cylinder 12 and nozzle holder 1
An injection pump chamber 33 is formed in a space surrounded by 3 and 3. The injection pump chamber 33 is connected to the injection nozzle 1 via the pressure passage 42.
4. The injection nozzle 14 is of a known needle valve type (not shown), and this needle valve closes the injection hole by being pushed by a nozzle spring 44 housed in a nozzle spring chamber 43. It is configured to open the nozzle hole by rising against the biasing force of the spring 44 when high-pressure fuel is sent. On the other hand, a solenoid valve 5 is used to control the fuel injection timing.
0 is attached to the pressure feeding cylinder 11. The electromagnetic valve 50 has a body 58 and a casing 59, which are attached to the pressure-feeding cylinder 11 with a screw. Inside the solenoid valve 50, a needle 51 that moves up and down and an armature 60 connected to the needle 51 are attracted by energization. The coil 57 and the needle 5 disposed in the spring chamber 61 close the valve.
1 in the valve opening direction (upward in the figure)
and are provided. Further, an annular groove 54 is formed on the outer periphery of the center of the needle 51, and a valve body 53 is formed at the tip thereof, and the valve body 53 abuts against a valve seat 63 formed in the upper part of the spring chamber 61. Further, the spring chamber 61 communicates with an oil reservoir chamber 64 on one side and is connected to a passage 66 on the other side. The passage 66 is a check valve 56
, a discharge pipe 67 and a discharge gear 7 to the tank 8 . An injection rate control port 1 - 21 and a timing port 22 are open to the pressure pump chamber 18 . Injection rate control port 2
1 is connected to the annular groove 54 of the needle 51 via a passage 24 in a closed state, and is further connected to a passage 66 via a passage 65 and a throttle valve 55. Further, the timing port 22 is connected to an oil reservoir chamber 64 of the solenoid valve 50 via a timing passage 25. A drain port 23 is provided in the pressure receiving chamber 32 of the injection cylinder 12.
is open, and the pressure receiving chamber 32 communicates with the nozzle spring chamber 43 via the feed passage 26, the spring chamber 61 of the electromagnetic valve 50, and the passage 27. Low-pressure fuel is supplied to the main gear rally 4 from a metering pump 6 via an introduction path 9 formed in the cylinder head 2 . In addition, the main gear lary 4 is connected to the sub gear lary 72, which is a gap formed between the inner surface of the retaining nut 15, the pressure feeding cylinder LL injection cylinder 12, the nozzle holder 13, and the injection nozzle 14, via the open lower 0°71. Further, the sub-gearry 72 communicates with the feed passage 26 and the passage 27 through openings 29,30. The low pressure fuel is supplied to the pressure pump chamber 18, the spring chamber 61, and the oil storage chamber 6.
4. The nozzle spring chamber 43, the passage 24, the timing passage 25, the feed passage 26, etc. are filled, and excess low-pressure fuel is discharged to the tank 8 via the check valve 56, the discharge pipe 67, etc. On the other hand, high-pressure fuel for metered injection supplied from the metering pump 6 is introduced via a fuel passage 10 formed in the pressure-feeding cylinder 11, and further includes a check valve 35 and a metering passage 3.
4 into the injection pump chamber 33. Next, the operation of this fuel injection unit will be explained with reference to FIG. 2. During the process in which the pressure-feeding plunger 17 moves from the bottom dead center to the top dead center, the solenoid valve 50 is in an open state, and the pressure-feeding pump chamber 1
Low-pressure fuel is sucked into the fuel tank 8 through the sub-gear rally 72, the opening 29, the feed passage 26, the spring chamber 61, the oil reservoir chamber 64, the timing passage 25, and the timing port 22. Moreover, when the pressure-feeding plunger 17 reaches the top dead center, the second
As shown in FIG. 2(B), high-pressure fuel metered from the metering pump 6 according to the operating state at an appropriate timing tl is introduced into the injection pump chamber 33 through the above-mentioned route, and as shown in FIG.
As shown in C), the injection plunger 31 moves toward the lower pressure pressure pump chamber 18 by the amount of introduced fuel. Next, when the pressure plunger 17 is pushed downward from time t2 by a cam (not shown) via the cam follower 19 while the solenoid valve 50 is kept open, the fuel in the pressure pump chamber 18 is transferred to the timing port 22 and the timing passage 25. , oil chamber 64, spring chamber 61, passage 66, check valve 56,
It is discharged into the tank 8 via the discharge pipe 67 and the discharge gallery IJ7. Therefore, the internal pressure of the pressure pump chamber 18 does not increase, so the injection plunger 31 does not move. Next, as shown in FIG. 2(d), when the coil 57 of the solenoid valve 50 is energized at time t3, the electromagnetic force causes the valve body 53 to resist the biasing force of the spring 52 and press against the valve seat 63. When they come into contact, the valve becomes closed. Then, the timing port 22 is closed to the exhaust gear gallery 7, but the fuel in the pressure pump chamber 18 is transferred to the injection rate control port 21, the passage 24, the annular groove 54, the passage 65, the throttle valve 55, the passage 66, and the reverse. stop valve 56,
It is discharged into the tank 8 via the discharge pipe 67 and the discharge gear gallery 7. However, since the exhaust system includes the throttle valve 55, the resistance is greater than when exhausting from the timing port 22, and the internal pressure of the pressure pump chamber 18 increases. Therefore, the injection plunger 31 receives pressure from the pressure receiving chamber 32 and moves downward, increasing the internal pressure of the injection pump chamber 33. However, since the pressure pump chamber 18 is leaking through the injection rate control port 21, the injection pressure gradually increases as shown in FIG. At t4, the needle 45 is lifted,
As shown in FIG. 2(j), injection is started at a gradually increasing injection rate. In this way, since the injection rate at the start of injection increases gradually, engine explosion noise can be suppressed. Next, at time t5, when the timing lead 28 of the pressure-feeding plunger 17 closes the injection rate control port 21, the leakage in the pressure-feeding pump chamber 18 disappears, and the discharge system such as the passage 24 is suddenly cut off, reducing the effective compression capacity. Since the pressure decreases rapidly, the internal pressure of the pressure pump chamber 18 increases rapidly. Then, the injection plunger 31 receives pressure from the pressure receiving chamber 32 and moves downward rapidly, causing the internal pressure of the injection pump chamber 33 to rise rapidly. As a result, the injection rate also increases rapidly and good injection continues. Next, at time t6, when the injection plunger 31 descends to the position where the drain port 23 opens into the pressure receiving chamber 32, the fuel in the pressure pump chamber 18 is discharged through the drain port 23, the feed passage 26, the passage 66, the check valve 56, and the discharge. tube 67,
It is discharged into a tank 8 via a discharge gear 7. As a result, the internal pressure of the pressure pump chamber 18 decreases, and the internal pressure of the injection pump chamber 33 decreases accordingly, resulting in a decrease in injection pressure. However, when the internal pressure of the pressure pump chamber 18 decreases, the injection plunger 31 receives the internal pressure of the injection pump chamber 33 and moves toward the pressure pump chamber 18, which acts to prevent the drain port 23 from opening. This prevents the internal pressure of the chamber 18 from decreasing, and the internal pressure of the pressure pump chamber 18, the internal pressure of the injection pump chamber 33, and the injection pressure tend to gradually decrease. However, at time t7, which is approximately synchronized with time t6, when the energization of the coil 57 of the solenoid valve 50 is cut off, the valve body 5
3 is lifted up by the biasing force of the spring 52, and the valve is opened. Then, since the pressure pump chamber 18 leaks to the tank 8 through the above-mentioned path, its internal pressure decreases rapidly.Therefore, the internal pressure of the injection pump chamber 33 also decreases, the injection pressure decreases, and injection is stopped. At this time, the internal pressure of the pressure pump chamber 18 is applied to the spring chamber 61 via the drain port 23 and the feed passage 26, thereby increasing the lifting speed of the valve body 53. Therefore, the solenoid valve 50 is rapidly switched to the open state, and the internal pressure of the pressure pump chamber 18 and the injection pump chamber 33 are increased.
The internal pressure and injection pressure rapidly decrease, and therefore the injection rate also rapidly decreases. Further, the internal pressure of the pressure pump chamber 18 is applied to the nozzle spring chamber 43 via the drain port 23 and the passage 27, accelerating the closing of the needle 45. In the above embodiment, the throttle valve 55 is used to suppress the sudden increase in the injection pressure at the beginning of injection, but as shown in FIG. 7
3 and a vertical hole 7 communicating with the horizontal hole 73 and the spring chamber 61.
4, and the vertical hole 74 thereof may be used as an orifice to function as a throttle valve. Further, as shown in FIG. 4, a similar mechanism may be formed in the pressure-feeding plunger 17. That is, a vertical hole 77, a horizontal hole 76, and an annular groove 75 are formed in the pressure-feeding plunger 17, which communicate with the pressure-feeding pump chamber 18, and the annular groove 75 is formed at the beginning of injection.
An injection rate control port 21 is provided at a position facing 5, and the injection rate control port 21 is connected to the feed passage 26 or the passage 66.
The mechanism of the electromagnetic valve 50 may be simplified by connecting it to the electromagnetic valve 50. Here, the timing to start energizing the coil 57 of the solenoid valve 50 is the timing to start fuel injection, and the timing to cut off energization is the timing to end fuel injection. Therefore, these timings need to be determined depending on the operating state of the engine. Next, a method of controlling the solenoid valve 50 will be described. The rotation angle sensor 104 for detecting the engine rotation speed and the cylinder discrimination sensors 102 and 103 for cylinder discrimination are sensors that output pulse signals at a predetermined angle by the rotation of a drive shaft (not shown) that rotates in synchronization with the rotation of the engine. be. As shown in FIG. 5, the signal G1 outputted by the cylinder discrimination sensor 102 is 45° from the top dead center of the 11th 5th and 3rd cylinders.
The signal G2 outputted by the cylinder discrimination sensor 103 is output at a 45 degree advance position from the top dead center of the sixth, second, and s4 cylinders. Also, the signal He output from the rotation angle sensor 104 is at a position 30 degrees advanced from the top dead center of each cylinder (30 degrees BT port C).
Degree retarded position 1i! (20' ATDC) is output every 5 degrees between 50 degrees. Such cylinder discrimination sensors 102, 103, rotation angle sensor 104, and other sensors that detect the operating state of the engine, such as an accelerator opening sensor, an intake air pressure sensor,
Cooling water temperature sensors, etc. are connected to the electronic control unit 100, and the electronic control unit 100 determines the operating state of the engine according to the output signals of these sensors, and calculates the optimal injection start timing, injection end timing, injection amount, etc. death,
The opening and closing of the solenoid valve 50 is controlled via the drive circuit 101 at the timing shown in FIG. In normal control, the first pulse of the signal Ne that is output after the first pulse of the signal G2 that is output after the signal G1 is set to the 30° advance position (30'' of the top dead center of the sixth cylinder).
BTDC), and thereafter, the detection time of the first pulse of the signal Ne after the pulse of the signal G2 is detected is determined to be 30° BTDC of the second cylinder and 30" BTDC of the fourth cylinder. Every time a pulse of the signal G1 is detected, the detection time of the first pulse of the signal Ne detected after each pulse is determined as 30° BTDC of the first cylinder, 30° BTDC of the fifth cylinder, 30° BTDC of each cylinder is determined. In this way, 30° 8 TDC of each cylinder is detected, but if the injection start timing is determined to be, for example, 76 BTDC from the engine operating condition, 10 ° [1
TDC is determined by counting the pulses of the signal Ne from 30°BTI)C, and from 10" BTDC to 7"
The three degrees to BTDC is controlled by the time predicted from the period of the signal Ne. The solenoid valve 50 is closed at the injection start timing calculated in this way, and the injection end timing is determined based on the injection start timing and the injection amount determined by the engine operating condition. Valve 50 is opened. Next, processing when a sensor fails will be described. When the signal Ne is not output normally, the signal Gl is output. G2 is substituted as the signal Ne. That is, the signals Gl, G2
has a period of 120 degrees, so the period of the pulse signal is measured to find the time per degree, and from that value the time required from detecting 45 degrees BTDC of each cylinder to the predetermined injection start angular position The time is predicted, and the injection start timing is controlled based on that time. If either the signal G1 or the signal G2 is not output normally, the pulse period of one signal is similarly converted into time to control the 45° BTDC and injection start timing of each cylinder that cannot be actually measured. Signals Gl, G2. If all Ne is not output normally, the control of the solenoid valve 50 is stopped and the valve body 53 is opened by the biasing force of the spring 52. As a result, the internal pressure of the pressure pump chamber 18 no longer increases, and the injection plunger 31 is no longer driven downward. However, since the metered fuel is continuously pumped into the injection pump chamber 33 from the metering pump 6, the injection plunger 31 is pushed upward and comes into contact with the upper surface of the pressure receiving chamber 32 and stops. After this, the fuel pumped from the metering pump 6 has no escape, and the internal pressure of the injection pump chamber 33 rises to the injection-enabled pressure, and injection starts at the timing when the fuel is pumped from the metering pump 6. be done. In this way, the cylinder discrimination sensors 102, 103. Even if the rotation angle sensor 104 fails, operation can be continued.

【Effect of the invention】

The present invention provides a solenoid valve that controls injection by leaking or closing fuel in the pressure pump chamber through opening and closing operations in the passage connecting the pressure pump chamber and the discharge gear gallery, and in the pressure receiving chamber, a solenoid valve is provided in the passage connecting the pressure pump chamber and the discharge gear gallery. A drain port is provided at the position to spill the pressure in the pressure receiving chamber to the discharge gear, and a passage is provided from the drain port to the solenoid valve so that the pressure in the pressure receiving chamber is added to the force that opens the solenoid valve via the drain port. Since the solenoid valve is opened at the end of injection, the opening action of the solenoid valve is accelerated by the pressure in the pressure pump chamber, and the pressure in the pressure pump chamber leaks through this solenoid valve. As a result, the pressure drop becomes steeper. Therefore, the injection rate decreases sharply at the end of injection, improving combustion characteristics. Furthermore, since the pressure in the pressure pump chamber decreases steeply, the driving load on the pressure plunger is reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of a fuel injection unit according to a specific embodiment of the present invention, FIG. 2 is a timing chart explaining the operation of the fuel injection unit, and FIGS.
The figure is a sectional view showing characteristic parts of a fuel injection unit according to another embodiment, and FIG. 5 is a timing chart showing a method of controlling the electromagnetic valve of the fuel injection unit. 1...Fuel injection unit 6 Metering pump 7/Discharge gear rally 11 Pressure feeding cylinder 12 Injection cylinder
17 Pressure-feeding plunger 18 Pressure-feeding pump chamber 21
Injection rate control port 22 Timing port 23
Drain port 26...Feed passage 31...
Injection plunger 32...pressure receiving chamber 33, injection pump chamber 50, °, solenoid valve 54, annular groove 61...spring chamber

Claims (1)

[Claims] A pressure-feeding plunger driven in synchronization with the engine pressurizes the fuel in the pressure-feeding pump chamber, and the hydraulic pressure generated in the pressure-feeding pump chamber operates the injection plunger. In a fuel injection device that pressurizes fuel and injects it from an injection nozzle, an electromagnetic device is provided in a passage connecting the pressure pump chamber and the discharge gallery for controlling injection by causing the fuel in the pressure pump chamber to leak or close by an opening/closing operation. A valve is provided, and in a pressure receiving chamber that communicates with the pressure pump chamber and in which the injection plunger slides under pressure, a drain port is provided at a position corresponding to the injection end time to spill the pressure of the pressure receiving chamber to a discharge gallery; A passage is formed from the drain port to the solenoid valve so that the pressure in the pressure receiving chamber is applied to the acting force for opening the solenoid valve through the drain port, and the solenoid valve is opened at the end of injection. A fuel injection device featuring: