JP2508114B2 - Fuel injection device for diesel engine - Google Patents

Description

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

"Prior art" In the form of fuel injection into a diesel engine, it is desirable to speed up the pressure drop as much as possible at the end of injection from the viewpoint of engine exhaust smoke concentration, and to immediately stop injection from high pressure injection. .

However, the injection device disclosed in Japanese Patent Laid-Open No. 62-23552, in which the fuel overflow is adjusted by the electromagnetic spill valve for fuel metering, has an opening characteristic including response of the electromagnetic spill valve and other conduit loss. As a result, the overflow becomes relatively gentle on the high rotation side. That is, the exhaustion of fuel at the end of injection becomes worse.

On the other hand, an injection device in which a variable pressure chamber volume actuator is mounted in communication with the pressure chamber of the injection device for pilot injection is disclosed in JP-A-61-25925. However, the variable volume actuator is an injection device. Since it is used only for the pilot injection on the low rotation side, there is a problem that the expensive variable volume actuator is operated for a relatively short time.

"Problems to be Solved by the Invention" The present invention has been made in order to solve the above problems, and in addition to the action of the electromagnetic spill valve, the advantages of the variable volume actuator excellent in responsiveness described above are provided. combination,
An object of the present invention is to provide a fuel injection device for a diesel engine capable of instantaneously reducing the pressure at the end of injection.

"Means for Solving the Problems" The configuration of the present invention in accordance with the above-mentioned object is a fuel injection in which the fuel to be pressure-fed from the pressure chamber of the fuel injection pump of the diesel engine to the fuel injection valve is adjusted by the electromagnetic spill valve. An electrostrictive type pressurizing chamber volume variable actuator mounted in the pressurizing chamber for changing the volume of the pressurizing chamber, and a device for driving the electromagnetic spill valve to open at the end of injection. Output means for outputting a first drive signal and then outputting a second drive signal for driving the variable pressure chamber volume actuator at a required delay angle so as to increase the volume of the pressure chamber; And driving means for driving the variable volume actuator based on the second drive signal, after driving the electromagnetic spill valve based on the drive signal.

[Operation] According to the above configuration, at the end of injection, the first drive signal for opening the electromagnetic spill valve is first output, and then the electrostrictive pressure chamber volume variable actuator is operated with a required delay angle. A second drive signal for driving so as to increase. Therefore, based on these two drive signals,
Immediately after the electromagnetic spill valve opens and the pressure inside the pressurizing chamber begins to drop, the electrostrictive pressurizing chamber volume actuator starts to operate to increase the volume of the pressurizing chamber. For this reason, the pressure in the pressurizing chamber is likely to drop faster and drops instantaneously.

[Advantages of the Invention] According to the present invention, as described above, by operating the electrostrictive pressure chamber volume variable actuator in cooperation with the action of the electromagnetic spill valve, at the high rotation side of the injection device at the end of injection. Since the pressure drop of the engine can be performed instantaneously and the fuel cut at the end of injection can be made good, large fuel droplets are not injected into the combustion chamber of the engine and the smoke concentration of the engine is significantly reduced. It has an excellent effect that it can be lowered. Further, according to the injection device of the present invention, it is possible to improve fuel shortage by utilizing a variable volume actuator that has been conventionally used only for pilot injection on the low rotation side. Since the control can be performed only by setting a required delay angle by the electronic control device that controls the spill valve, the configuration of the control device is also simple.

[Example] Next, an example of the present invention will be described with reference to Figs. 1 to 5.

FIG. 1 is a partial cross-sectional view in which the present invention is applied to a distribution type fuel injection pump. A characteristic of this configuration is that an electrostrictive pressure chamber volume variable actuator 3 is provided in communication with the pressure chamber 2 of the distribution type fuel injection pump 1.

First, the fuel injection pump will be described. Casing 4
The plunger 6, which is reciprocally inserted into the cylinder bore 5, reciprocates in synchronization with half the engine speed. That is, the rotation of the engine is transmitted to the drive shaft 7 through the gear or the timing belt, and the plunger 6 is connected to the drive shaft 7.
Is driven to rotate, and the face cam 8 contacts the roller 9 to reciprocate. The face cam 8 is constantly urged to the left side of the drawing by a spring (not shown) and is in contact with the roller 9, and the reciprocating motion of the plunger 6 rotates around the axis to rotate the cam of the face cam 8. This is done by following the shape of the surface. Plunger 6 has, on its outer periphery, one distribution port 10 and suction grooves 11 as many as the number of engine cylinders.
And a pressurizing chamber 2 is formed between the tip end surface of the plunger 6 and the cylinder bore 5. When one of the suction grooves 11 communicates with the suction port 12 during the suction stroke of the plunger 6, fuel is introduced from the fuel chamber 13 into the pressurizing chamber 2. When the fuel in the pressure chamber 2 is pressurized during the pressure stroke of the plunger 6, it is pressure-fed from the distribution port 14 to the fuel injection valve 15 of each cylinder,
It is injected into the combustion chamber.

A fuel metering electromagnetic spill valve 16 is connected to the pressurizing chamber 2. The electromagnetic spill valve 16 is configured such that when a current is passed through the coil, the needle valve is lifted and the fuel in the high-pressure pressurizing chamber 2 is returned to the fuel chamber 13. Therefore,
When the electromagnetic spill valve 16 is actuated during the pressure stroke of the plunger 6, the fuel injection ends. Here, the timing of starting energization of the electromagnetic spill valve 16 is controlled by an electronic control device such as the microcomputer 20. The microcomputer 20 receives signals of an engine operating state detected by various sensors of the engine, a pump angle sensor 22, an accelerator operation amount sensor 24 and other sensors such as a temperature sensor 26, and the electromagnetic spill valve 16 is operated by a logic function described later. Control energization to.

The pump angle sensor 22 is combined with a pump angle pulsar 23 having a plurality of protrusions integrally attached to the drive shaft 7,
A pulse signal is output every predetermined angle of the drive shaft 7, that is, every rotation of a predetermined crank angle of the engine. In the case of this embodiment, the pulsar
The protrusions of 23 are provided with two toothless portions at every 90 ° crank angle from the state where 64 pieces are arranged at equal intervals. Therefore, when the engine rotates, a pump angle signal including a pulse signal from each tooth and a pulse signal from a toothless portion is generated as shown in the detected output after waveform shaping in FIG.

The accelerator operation amount sensor 24 is composed of, for example, a well-known potentiometer, and outputs the load information of the engine requested by the driver to the computer 20.

The pressurizing chamber volume variable actuator 3 includes a thin disk-shaped electrostrictive element 3a in a cylindrical casing 3b having a bottom.
It is formed by laminating one sheet into a columnar shape. A piston 3c is provided at the left end of the electrostrictive element 3a in FIG. 1 and is slidable in an oiltight manner with the casing 3b. This electrostrictive element 3a
Is a ceramic material called PZT, which contains lead zirconate titanate as its main component. When a compressive load is applied in the axial direction (when pressure in the pressurizing chamber acts), a voltage is generated in each electrostrictive element 3a, but it deforms. However, if this voltage is short-circuited or shot next time, a contraction (the volume of the pressurizing chamber increases) in the axial direction occurs. Further, it is possible to expand by applying a voltage in the polarization direction of the electrostrictive element 3a, and it is also possible to reduce the electrostrictive element 3a and restore the original state by releasing this voltage or applying a slight negative voltage. is there. Therefore, in this embodiment, by utilizing this property, the voltage generated at both terminals of the variable volume actuator 3 composed of an electrostrictive element at a desired time is calculated by the computer 20.
It is controlled so as to be short-circuited or to release the voltage by substantially increasing the volume of the pressurizing chamber 2 communicating with the actuator 3.

"Operation" The operation of the present embodiment having the above configuration will be described with reference to FIGS.

When the fuel injection routine starts as shown in the flowchart of FIG. 2, in step 101, information on the engine state such as the rotational speed, load, water temperature, and intake air temperature is
Inputs are made to the computer 20 from the pump angle sensor 22, the accelerator operation amount sensor 24, the temperature sensor 26, and the like. In step 102, the fuel injection amount is calculated based on the information. In step 103, the spill angle of the electromagnetic spill valve 16 that obtains the required fuel injection amount is calculated. In step 104, the calculated injection amount is zero (= 0).
It is judged whether or not, and when a positive result is obtained, the process returns, and when a negative result is obtained, the process proceeds to step 105,
An operating angle (delay angle) α of the variable volume actuator 3 is calculated. In step 106, the correction value of the operating angle α is
It is calculated as rotation correction τ ₁ and machine difference correction τ ₂ . As shown in FIG. 5 (a), the rotation correction τ ₁ has a characteristic that it decreases substantially in inverse proportion to the increase in the engine speed. This is because the difference in responsiveness becomes larger as the angle becomes higher, so that it is necessary to make the operating angle α ′ large. As shown in FIG. 5 (b), the machine difference correction τ ₂ is set to a small value for a model having a fast response of the electromagnetic spill valve for metering, and a large value for a model having a slow response. In step 107, the final operating angle α'is calculated from the following equation and the process returns.

α ′ = α−τ ₁ −τ ₂ FIG. 3 shows the entire fuel injection operation. At the time when the pump angle reference signal shown in FIG. As shown in FIG. 3 (1), the plunger stroke begins to increase, injection is started in the middle, and the control signal to the electromagnetic spill valve falls at a desired spill angle as shown in FIG. 3 (3) to cause electromagnetic spill. The valve opens and tries to end the injection. After that, the actuator actuation signal rises at the actuation angle α'as shown in FIG. 3 (4).

FIG. 4 shows the operation of the pressurizing chamber volume variable actuator. When the electromagnetic spill valve drive signal is turned off simultaneously with the injection end command as shown in FIG. 4 (1), as shown in FIG. 4 (2). Since the electromagnetic spill valve opens with a gentle curve,
As shown in FIG. 4 (3), the pressure in the pressurizing chamber is gradually decreased as shown by the solid line in the normal state, but the pressurizing chamber volume variable actuator operates as shown in FIGS. 4 (5) and 4 (6). ′
Therefore, as shown in FIG. 4 (4), short-circuiting the generated voltage between both terminals of the pressurizing chamber volume variable actuator causes rapid contraction to increase the volume of the pressurizing chamber. As indicated by a broken line in), the pressure in the pressurizing chamber is likely to drop faster, and instantaneously drops linearly to improve the fuel cutoff.

The present invention is not limited to the details of the structure of the above-described embodiment, and for example, a microcomputer as an electronic control device may partially include an electronic circuit.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional configuration diagram showing an embodiment of the present invention, FIG. 2 is a flow chart showing a fuel injection routine, FIG. 3 is a timing chart showing the entire fuel injection operation, and FIG. Operation timing charts showing the operation of the actuator, and FIGS. 5A and 5B are characteristic diagrams showing rotation correction and machine difference correction, respectively. 1 ... Distribution type fuel injection pump, 2 ... Pressurization chamber, 3 ... Pressure chamber volume variable actuator, 16 ... Electromagnetic spill valve for fuel metering, 20 ... Microcomputer.

Claims (1)

(57) [Claims] 1. A fuel injection device for adjusting the amount of fuel to be pressure-fed to a fuel injection valve from a pressure chamber of a fuel injection pump of a diesel engine by an electromagnetic spill valve, the fuel injection device being mounted in the pressure chamber. An electrostrictive variable pressure chamber volume variable actuator that changes the volume of the pressure chamber, and a first drive signal for driving the electromagnetic spill valve to open so as to open the electromagnetic spill valve at the end of injection, and then apply the applied delay angle with the required delay angle. Output means for outputting a second drive signal for driving the pressure chamber volume variable actuator so as to increase the volume of the pressurization chamber; and, after driving the electromagnetic spill valve based on the first drive signal, And a drive unit that drives the variable volume actuator based on two drive signals.