JPS5918249A - Fuel injection rate controlling apparatus for diesel engine - Google Patents

Abstract

PURPOSE:To enable to control the fuel injection rate of a diesel engine according to parameters relating to the operation of the engine, by forming a pressure chamber communicated with a pressurizing chamber of a fuel injection pump and incorporating therein a piston which is displaced in response to the voltage impressed on a piezoelectric stack. CONSTITUTION:A fuel injection rate controlling apparatus 15, communicated with a pressurizing chamber 4 for pressurizing fuel via a connecting passage 16 at the time when a plunger 2 of a fuel injection pump 1 is moved to the right, comprises a cylinder 19 in which a pressure chamber 17 is defined by a piston 18. A piezoelectric stack 20 constituted by stacking piezoelectric elements is disposed in the other chamber of the cylinder 19 defined by the piston 18, and the piston 18 is pre-loaded by a compression coiled spring 21 disposed in the pressure chamber 17. With such an arrangement, the piston 18 can be displaced by impressing on the piezoelectric stack 20 a voltage corresponding to the deviation between the output of a pressure sensor 23 for detecting the pressure in the pressurizing chamber 4 and an aimed value determined by the operational conditions of an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection rate control device for a diesel engine.

It is generally known that in diesel engines, the fuel injection rate is a factor that has an important effect on engine characteristics.

However, in the past, the fuel injection rate was not controlled, and the cam shape and piping of the cam disk of the fuel injection pump were not controlled.

By tuning the injection valves, etc., it was possible to obtain the optimal fuel injection rate only under certain conditions.

Therefore, it has been difficult to optimize the fuel injection rate when engine operating parameters such as accelerator pedal travel and engine speed change.

The present invention has been made in view of the above points, and an object of the present invention is to enable the fuel injection rate to be controlled according to the operating parameters of a diesel engine.

Therefore, in the fuel injection rate control device for a diesel engine according to the present invention, a cylinder having a built-in piston is used to connect a pressurizing chamber that pressurizes fuel with a plunger of a fuel injection pump or a passage that sends fuel pressurized by a plunger to an injection valve. A communicating pressure chamber is formed, and a piezo stack in which piezoelectric effect elements are laminated is inserted between the end of the cylinder opposite to the pressure chamber and the piston, and the piston is moved according to the voltage applied to the piezo stack. The fuel injection rate can be controlled in accordance with the operating parameters of the engine by controlling the pressure in the pressure chamber by changing the total pressure of the fuel delivered to the injection valve.

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

FIG. 1 is a configuration diagram showing an example of a mechanical part of a fuel injection device equipped with a fuel injection rate control device embodying the present invention.

In the figure, only the parts of the fuel injection pump 1 that are related to the present invention are shown, but the fuel injection pump 1 is driven by the rotation of a cam disc connected to the drive shaft of an engine (not shown) to provide rotational movement for fuel distribution and fuel suction pumping. The plunger 2 is provided with a plunger 2 that makes a reciprocating motion.

When the plunger 2 moves to the left in the figure, the suction longitudinal groove 2, a aligns with the fuel suction boat 6, and fuel is suctioned into the pressurizing chamber 4.

Further, when the plunger 2 moves rightward in the figure, the fuel in the pressurizing chamber 4 is pressurized, and when the horizontal discharge passage 2b and the discharge passage 5 coincide, the pressurized fuel is transferred to the vertical passage 2C2 and the horizontal discharge passage. 21], discharge passage 5. The fuel is supplied to the injection valve 8 via the delivery valve 6 and piping 7 to perform injection.

Then, when the relief passage 2d of the plunger 2 moves to the right relative to the sleeve 9 and is opened, the pressurized fuel escapes from the relief passage 2d into the case inner space 10, and the pressure thereof is lower than the set pressure of the delivery valve 6. , and fuel injection ends.

Note that the position of the sleeve 9 that determines the fuel injection amount is determined by the position of the magnet 11 fixed to the sleeve 9 and this magnet 1.
It is controlled by a sleeve actuator consisting of two annular coils 12, 13 arranged around one.

Next, the fuel injection rate control device 15 includes a cylinder 19 fully equipped with a piston 18 provided so as to form a pressure chamber 17 that communicates with the pressurization chamber 4 of the fuel pump 1 via a communication passage 16;
A piezo stack 20 in which piezoelectric effect elements are laminated is inserted between the pressure chamber 17 in the cylinder 19, the end portion 19a, and the piston 18, and a compression coil spring that applies a preload to the piston 18 provided on the pressure chamber 17 side. 21. and an oil seal 22 fitted to the piston 18.

Note that the coil spring 21 may be omitted as long as it has a weak biasing force and the piston 18 and the piezo stack 20 are fixed together.

In addition, a pressure sensor 26 such as a tilting strain gauge is attached to the end of the fuel injection pump 1 so that the pressure in the pressurizing chamber 4 can be detected through the communication passage 16.

FIG. 2 is a block diagram of a control section that completely controls the voltage applied to the piezo stack 20 of the fuel injection rate control device 15 of FIG. 1, and a feedback control system based on its output.

In the same figure, the control section 25 includes a function generator 26° compensator 27 and a voltage generator 28.

The function generator 26 creates a target pressure waveform based on engine operating parameters such as accelerator pedal travel α, engine speed N, and cooling water temperature T, and generates a target pressure waveform based on engine operating parameters such as accelerator pedal travel α, engine speed N, and cooling water temperature T, and generates a target pressure waveform based on engine operating parameters such as accelerator pedal travel α, engine speed N, and cooling water temperature T. The target value of pressure P for each cylinder as a function of time in synchronization with. Output. Note that the target pressure waveform is determined experimentally in advance.
What is necessary is to select the target pressure waveform according to the input data.

The compensator 27 has a target value P. and the detected value P of the pressure sensor 26
Depending on the magnitude of the difference, compensation is performed proportionally, integrally, or differentially to enable responsive and stable control.

The voltage generator 28 outputs a voltage e according to the output of the compensator 27 to the piezo stack 20 of the fuel injection rate control device 15.

Next, the operation of the embodiment configured as described above will be explained.

First, the control of fuel pressure by the fuel injection rate control device 15 will be described.

Displacement fjkv of piston 18 of fuel injection rate control device 15
A is the amount of displacement y due to the voltage e being applied to the piezo stack 20. and the displacement amount Yp due to the force and the pressure Ps of the pressure chamber 17 (ye
vp) (see Figure 6).

Therefore, the amount of volume change Q2 of the fuel in the pressure chamber 17 is:
If the cross-sectional area of the piston 18 is t A 2, then Qz=Az
It is expressed as (ye-yp)=Az(ke"e &p'Ps). However, both ke and kP are coefficients.

That is, by varying the voltage e applied to the piezo stack 20, the volume change amount Q2 changes.

On the other hand, the volume change Q1 of the fuel in the pressurizing chamber 4 of the fuel injection pump 1 is the cross-sectional area of the plunger 2 'ff:A + .

If the stroke amount is X, Qt=A+x It is expressed as

Therefore, the amount of fuel Q that is also discharged from the delivery valve 6
is the sum of the amount of change in fuel volume Q1 that occurs in the pressurizing chamber 4 due to the stroke of the granger 2 and the amount of change in fuel volume Q2 that occurs in the pressure chamber 17 due to the application of voltage ef to the piezo stack 20.

By the way, the pressure P generated in the pressurizing chamber 4 (the pressure in the communication passage 16 and the pressure chamber 17 is the same in the state of no flow) is determined by the dimensions of the piping and the bulk modulus of fuel, which are shown by the system gain G in FIG.
Since it is determined by the material and type of fuel, it is determined by the volumetric change rate Q, Q2 of the fuel.

From the above, the pressure P in the pressurizing chamber 4 is P=f(x, x, e, e) It is expressed as However, the second is the rate of change in the amount of o-reduction.

This is the voltage change rate.

Here, the stroke amount X and the stroke amount change rate;
Since the pressure P is uniquely determined by the fuel injection pump 1, the engine speed, and the cam shape of the cam disk, the pressure P can be arbitrarily controlled by changing the voltage e applied to the piezo stack 20.

In this case, it is sufficient to control the pressure waveform by correcting the pressure waveform determined by the stroke of the plunger 2.
The change in the volume change amount Q2 is sufficient to be - several times the volume change amount Q1.

Therefore, it is sufficient for the displacement y8 of the piezo stack 20 due to the applied voltage e to be several tens of μm.

On the other hand, even if the displacement amount ye is a minute change of several tens of μm, the change in the pressure waveform occurs on the order of several msec, so the piezo stack 20 makes the change rate of 11e on the order of several hundred μsec. There is a need.

In this way, the pressure in the pressurizing chamber 4 is controlled by the fuel injection rate control device 15.

Therefore, the control unit 25 sets the accelerator pedal travel α.

A target pressure value P determined based on engine operating parameters such as engine speed N and cooling water temperature T.

After performing PID compensation on the difference between the detected value P and the detected value P detected by the pressure sensor 26, a voltage e corresponding to the difference is applied to the piezo stack 20 of the fuel injection rate control device 15,
Pressure P is target value P. so that it becomes

In this manner, the fuel injection rate, that is, the injection waveform by the injection valve 8 can be controlled by controlling the pressure Pi in the pressurizing chamber 4 according to the operating parameters of the engine.

FIG. 4 is a configuration diagram showing another embodiment of the present invention,
Components corresponding to those in FIG. 1 are designated by the same reference numerals, and explanations of those portions will be omitted.

In this embodiment, a fuel injection rate control device 15 and a pressure sensor 26 are provided near the injection valve 8 of each cylinder, and a pressure chamber 17 is
It communicates with a passage 60 through which fuel pressurized by a plunger is sent to the injection valve 8, and a pressure sensor 23 is arranged so as to be able to detect the pressure within the passage 60.

In this way, since the inlet pressure of the injection valve 80 can be directly controlled, the influence of the pump and piping on the fuel before reaching the injection valve 8 can be compensated for, and more accurate control can be performed.

As explained above, according to the present invention, since the fuel injection pressure can be controlled, the fuel injection rate can be optimally controlled according to the operating parameters of the engine such as the accelerator pedal travel and the engine speed. Improved fuel efficiency 2. Reduction of noise and vibration, purification of exhaust gas.

Improved startability can be achieved. Further, since the cam shape of the cam disk can be simplified, costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a control section that controls the fuel injection rate control device 15 of FIG. 1 and a feedback control system based on its output. FIG. 6 is a diagram showing an example of the characteristics of the fuel injection rate control device 15. FIG. 4 is a configuration diagram showing another embodiment of the present invention. 1.Fuel injection pump 2. ...Plunger 4...
・Pressure chamber 6...Delivery valve 15...
・Fuel injection rate control device 17...pressure chamber 18...
Piston 19... Cylinder 20... Piezo stack 21... Compression coil spring 26... Pressure sensor 25... Control section 26... Function generator 27... Compensator 28... Voltage generator
60...Aisle Figure 3 1+@2771

Claims (1)

[Claims] 1. In a diesel engine, a cylinder containing a piston is installed so as to form a pressure chamber communicating with a pressurization chamber in which fuel is pressurized by a plunger of a fuel injection pump or a passage in which fuel pressurized by the granger is delivered to an injection valve. A piezo stack is inserted between the end of the cylinder opposite to the pressure chamber and the piston, and the piston is displaced in accordance with a voltage applied to the piezo stack to reduce the pressure in the pressure chamber. 1. A fuel injection rate control device, characterized in that the fuel injection rate can be controlled by controlling and changing the pressure of fuel delivered to the injection valve.