JPH0510154A - Drive controller of piezoelectric element for fuel injection control - Google Patents

Abstract

PURPOSE:To improve the accuracy of control over fuel injection timing and injection quantity by citing any displacement delay even if an element temperature goes up and a response time of piezoelectric element displacement becomes longer, and executing a pilot injection at the specified timing. CONSTITUTION:A piezoelectric element 30 is attached to a fuel injection pump 1, and this piezoelectric element 30 operates to expand or contract by means of charge and discharge operations, regulating the extent of fuel pressure in a high-pressure chamber 15 and making it perform a main injection and a pilot injection advance of this main injection with a fuel injection nozzle 4. In addition, a thermocouple 77, detecting a temperature of the piezoelectric elect 30, is attached to a piezoelectric spill valve 23. A central processing unit (CPU) calculates the charging timing of the piezoelectric element 30 in order to do the pilot injection at the specified timing based on the specified crank angle of a diesel engine 2. Moreover, this CPU quickens the charging timing of the piezoelectric element 30 in proportion as the temperature detected by the thermocouple 77 is going up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for a piezoelectric element for fuel injection control provided in a fuel injection pump for supplying high pressure fuel to a fuel injection valve.

[0002]

2. Description of the Related Art Conventionally, during low-speed operation or low-load operation of a compression ignition diesel engine, fuel injected into a combustion chamber explosively burns due to ignition delay,
Combustion noise and nitrogen oxides (NO _x ) in exhaust gas may increase. For this, it is effective to perform pilot injection prior to main fuel injection. In this pilot injection, a part of the total fuel injection amount injected in each injection period is pre-injected prior to the main injection, and the fuel from the pilot injection is ignited to maintain a sufficient temperature in the combustion chamber. The fuel ignition of the main injection that follows is effectively performed.

In order to perform the pilot injection, the high pressure chamber and the fuel chamber in the fuel injection pump communicate with each other through a spill passage, and a spill valve is arranged in the spill passage. By controlling the opening and closing of the spill valve during the compression stroke of the plunger, the amount of fuel that overflows to the low pressure side through the spill passage is adjusted, and pilot injection and subsequent main injection are executed. As the spill valve, one using a piezoelectric element has been adopted in recent years. That is, the piezoelectric element has a property of expanding when electric charge is supplied (charged) and contracting when electric charge is discharged (discharged),
In the spill valve, the spill passage is opened and closed by driving the valve body by the expansion and contraction operation of this piezoelectric element.

However, the capacitance of the piezoelectric element generally decreases as the temperature decreases, and the amount of charge that can be received decreases and the amount of elongation decreases. Therefore, if the temperature becomes low as described above, good fuel injection control cannot be performed.

In order to address such a problem, Japanese Patent Laid-Open No. 1-187345 discloses a temperature of a piezoelectric element detected by a temperature sensor and applies the temperature to the piezoelectric element as the detected temperature becomes lower. A technique for increasing the voltage is disclosed. According to this technique, the amount of electric charge charged in the piezoelectric element can be kept constant and a constant amount of expansion can be obtained.

[0006]

However, in the above-mentioned prior art, when the temperature of the piezoelectric element rises, the capacitance increases, so that the capacitance increases in response to a constant charge amount. As a result, the applied voltage decreases. Then, due to the decrease in the applied voltage, the charging time becomes longer, and the time required for the piezoelectric element to reach a predetermined extension amount becomes longer. As a result, the displacement of the piezoelectric element is delayed, the start timing and the end timing of the pilot injection are delayed, and the accuracy of controlling the fuel injection timing and the fuel injection amount is reduced.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to be able to compensate for the displacement delay even if the element temperature rises and the response time of displacement of the piezoelectric element becomes long. Therefore, it is an object of the present invention to provide a drive control device for a piezoelectric element for fuel injection control, which can execute pilot injection at a predetermined timing and improve the accuracy of control of fuel injection timing and fuel injection amount.

[0008]

In order to achieve the above object, the present invention, as shown in FIG. 1, sucks fuel into a high pressure chamber M3 by reciprocating motion of a plunger M2 based on rotation of a diesel engine M1. A fuel injection pump M5 that pressurizes and supplies the high-pressure fuel pressurized in the high-pressure chamber M3 to the fuel injection valve M4, expands and contracts due to charge and discharge, and pressurizes the fuel in the high-pressure chamber M3. And a fuel injection control piezoelectric element M6 that causes the fuel injection valve M4 to perform main injection and pilot injection prior to the main injection.
Basic timing calculation means M7 for calculating charge / discharge timing of the piezoelectric element M6 to perform pilot injection at a predetermined timing with reference to a predetermined crank angle of the diesel engine M1, and an element for detecting the temperature of the piezoelectric element M6. A temperature detection sensor M8 and a timing correction means M9 for accelerating the charging / discharging timing of the piezoelectric element M6 by the basic timing calculation means M7 as the temperature detected by the element temperature detection sensor M8 rises are provided.

[0009]

When the fuel injection pump M5 operates, the plunger M2 reciprocates based on the rotation of the diesel engine M1, and the reciprocating motion sucks and pressurizes the fuel into the high pressure chamber M3. Then, the high pressure fuel pressurized in the high pressure chamber M3 is supplied to the fuel injection valve M4. At this time, when the fuel injection control piezoelectric element M6 is charged and discharged and expands and contracts, the pressure of the fuel in the high-pressure chamber M3 is adjusted, and the fuel injection valve M4.
At, main injection and pilot injection prior to the main injection are performed.

When executing the main injection and the pilot injection, the basic timing calculating means M7 carries out the pilot injection at a predetermined timing with reference to a predetermined crank angle of the diesel engine M1, so that the charging / discharging timing of the piezoelectric element M6. To calculate. The charge / discharge timing at this time is corrected according to the temperature of the piezoelectric element M6.
That is, the temperature of the piezoelectric element M6 is detected by the element temperature detection sensor M8, and as the element temperature rises, the timing correction means M9 advances the charge / discharge timing of the piezoelectric element M6 by the basic timing calculation means M7.

Therefore, when the element temperature rises, the time required for the piezoelectric element M6 to reach a predetermined amount of expansion (response time of the piezoelectric element M6) increases, but the increased amount is charged and discharged as described above. It is compensated by advancing the timing.

[0012]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a schematic diagram of a distributed fuel injection pump 1 provided with a drive control device for a piezoelectric element for fuel injection control according to the present embodiment, and a supercharged diesel engine 2 to which fuel is supplied by the fuel injection pump 1. It is a figure which shows a structure and FIG. 3 is a figure which expands and shows the said fuel injection pump 1. As shown in FIG. The fuel injection pump 1 includes a drive pulley 3 drivingly connected to a crankshaft 44 of a diesel engine 2 via a belt or the like. Then, the fuel injection pump 1 is driven by the rotation of the drive pulley 3, and the fuel is pressure-fed to a fuel injection nozzle 4 as a fuel injection valve provided for each cylinder (four cylinders in this case) of the diesel engine 2 to inject fuel. I do.

A drive shaft 5 is attached to the drive pulley 3.
A fuel feed pump (developed by 90 degrees in the figure) 6 composed of a vane type pump and a disc-shaped pulsar 7 are attached to the drive shaft 5. On the outer peripheral surface of the pulsar 7, the same number of teeth (4 in this case) as the number of cylinders of the diesel engine 2 are formed at equal angular intervals, and 14 adjacent teeth (total 5 teeth).
6) projections are formed at equal angular intervals. And
The base end portion (right end portion in the drawing) of the drive shaft 5 is connected to the cam plate 8 via a coupling (not shown). A roller ring 9 is provided between the pulsar 7 and the cam plate 8, and a plurality of cam rollers 10 facing the cam face 8 a of the cam plate 8 are attached to the roller ring 9. The cam plate 8 is constantly urged and engaged with the cam roller 10 by the spring 11.

A fuel pressurizing plunger 12 is integrally rotatably attached to the cam plate 8, and the rotational force of the drive shaft 5 is transmitted to the cam plate 8 via a coupling, whereby the cam plate 8 is rotated. Also, the plunger 12 is reciprocally driven in the left-right direction in the drawing while rotating. The plunger 12 is fitted into a cylinder 14 formed in the pump housing 13, and a high-pressure chamber 15 is formed between the tip end surface (the right end surface in the drawing) of the plunger 12 and the inner bottom surface of the cylinder 14. The same number of suction grooves 16 and distribution ports 17 as the number of cylinders of the diesel engine 2 are formed on the outer periphery of the plunger 12 on the front end side. A suction passage 19 and a distribution passage 18 are formed in the pump housing 13 so as to correspond to the suction groove 16 and the distribution port 17.

When the fuel feed pump 6 is driven based on the rotation of the drive shaft 5, fuel from a fuel tank (not shown) is supplied into the fuel chamber 21 through the fuel supply port 20. Further, in the intake stroke in which the plunger 12 moves (returns) in the left direction in the drawing and the high pressure chamber 15 is decompressed, one of the intake grooves 16 communicates with the intake passage 19 to move from the fuel chamber 21 to the high pressure chamber 15. Fuel is introduced into.
On the other hand, in the compression stroke in which the plunger 12 moves to the right in the drawing (forward movement) to pressurize the high-pressure chamber 15, fuel is pressure-fed and injected from the distribution passage 18 to the fuel injection nozzle 4 of each cylinder. It

The pump housing 13 includes a high pressure chamber 1
A spill passage 22 for fuel overflow is formed to connect the fuel cell 5 and the fuel chamber 21. A piezo spill valve 23 is provided in the middle of the spill passage 22. The piezo spill valve 23 is for adjusting the pressure of the fuel in the high-pressure chamber 15 to cause the fuel injection nozzle 4 to perform main injection and pilot injection prior to the main injection.

The piezo spill valve 23 is provided with a valve 24 that can move up and down. The valve 24 closes (closes) the spill passage 22 by coming into contact with a valve seat 25, and is separated from the valve seat 25. As a result, the spill passage 22 is opened (opened). The valve 24 is driven to drive the spill passage 2
In order to open and close the valve 2, the urging force of the spring 26 acts on the lower side of the valve 24, and the pressure of the fuel acts on the upper side of the valve 24. That is, the spring 26 is disposed immediately below the valve 24 in a compressed state, and the spring 26 constantly urges the valve 24 upward so that the spill passage 22 is opened.

A variable pressure chamber 27 is formed above the valve 24, and the fuel in the variable pressure chamber 27 pushes the valve 24 downward through a communication hole 28 having a small diameter. In order to adjust the pressing force of the fuel acting on the upper surface of the valve 24 by changing the volume of the variable pressure chamber 27, the piezoelectric element 30 as a piezoelectric element and the piston 2 are provided above the variable pressure chamber 27.
9 is provided, and a spring 31 is provided below the transformer chamber 27.
Are arranged. The spring 31 always biases the piston 29 upward. Further, the piezo element 30 is a PZ
It has a structure in which a plurality of plate-shaped members made of T or the like are laminated, and expands when a voltage is applied and electric charges are supplied (charged), and the piston 29 is moved downward against the biasing force of the spring 31.
When the electric charge is discharged (discharged), it contracts and allows the upward movement of the piston 29 by the urging force of the spring 31.

Further, in order to stabilize the behavior of the valve 24 even when the fuel inside the variable pressure chamber 27 is reduced due to a leak, the variable pressure chamber 27 and the high pressure chamber 15 can be communicated by the reset passage 32. .. The opening and closing of the reset passage 32 is performed when the rotational movement and the reciprocating movement of the plunger 12 come to a predetermined timing. By opening and closing the reset passage 32, fuel is replenished in the variable pressure chamber 27 before the piezoelectric element 30 expands, and the initial pressure in the variable pressure chamber 27 is reset to a constant value.

Here, the fuel injection control by the piezo spill valve 23 will be briefly described with reference to FIGS. First, in FIG. 5, the plunger 12 moves to the left in the figure (return).
In this state, the suction groove 16 of the plunger 12 communicates with the suction passage 19 and the distribution port 17 is blocked from the distribution passage 18. The piezo element 30 contracts and the valve 24 opens the spill passage 22. Therefore, the fuel is sucked into the high pressure chamber 15 through the suction passage 19, and further guided to the variable pressure chamber 27 through the reset passage 32.

As shown in FIG. 6, when the plunger 12 moves to the right in FIG. 6 from the above state (forward), both the suction passage 19 and the reset passage 32 are shut off, and the inside of the high pressure chamber 15 is closed. The fuel begins to be pressurized. At this time, the piezo element 30 is still contracted, and the spill passage 22 is open.

As shown in FIG. 7, when a predetermined voltage is applied to the piezo element 30, the piezo element 30 is caused by the piezoelectric effect.
Stretches. As a result, the fuel in the variable pressure chamber 27 is pressurized, and the pressing force of the fuel overcomes the urging force of the spring 26 to move the valve 24 downward and close the spill passage 22. At this time, even if the high pressure chamber 15 is pressurized by the forward movement of the plunger 12, the valve 24 continues to be closed because the pressure receiving area difference of the valve 24 and the pressure of the variable pressure chamber 27 are high. When the distribution port 17 of the plunger 12 communicates with the distribution passage 18 as shown in FIG. 8, fuel is injected from the fuel injection nozzle 4 (fuel injection start).

When the charge of the piezo element 30 is released (shorted) as shown in FIG. 9 when a predetermined injection amount is obtained,
The piezo element 30 contracts and the pressure in the variable pressure chamber 27 decreases.
Then, the valve 24 is moved upward by the biasing force of the spring 26, and the spill passage 22 is opened. As a result, the high-pressure fuel in the high-pressure chamber 15 overflows into the fuel chamber 21, and the injection ends (fuel injection end).

Therefore, by adjusting the timing of applying the voltage to the piezo element 30 of the piezo spill valve 23 and the timing of discharging the charge of the piezo element 30, the start timing and the end timing of the pilot injection, the start timing and the end of the main injection are adjusted. It is possible to control the timing.

As shown in FIG. 2, on the lower side of the pump housing 13, a timer device (90 degrees expanded in the figure) 34 for controlling fuel injection timing is provided. The timer device 34 controls the position of the roller ring 9 with respect to the rotation direction of the drive shaft 5 to control the timing at which the cam face 8a engages with the cam roller 10, that is, the reciprocating timing of the cam plate 8 and the plunger 12. Is.

The timer device 34 is operated by hydraulic pressure, and includes a timer housing 35, a timer piston 36 fitted in the timer housing 35, and a low pressure chamber 37 on one side of the timer housing 35. The timer piston 36 is composed of a timer spring 39 and the like for pressing and urging the timer piston 36 to the pressurizing chamber 38 on the other side. The timer piston 36 is connected to the roller ring 9 via a slide pin 40.

In the pressure chamber 38 of the timer housing 35,
The fuel pressurized by the fuel feed pump 6 is introduced. The position of the timer piston 36 is determined by the equilibrium relationship between the fuel pressure and the urging force of the timer spring 39. In addition, the position of the roller ring 9 is determined by the position of the timer piston 36, and the plunger 1 is moved through the cam plate 8.
The reciprocating timing of 2 is determined.

In order to control the fuel pressure of the timer device 34, a timing control valve 41 is provided in the communication passage 42 connecting the pressurizing chamber 38 and the low pressure chamber 37. The timing control valve 41 is an electromagnetic valve that is opened / closed by a duty-controlled energization signal, and the fuel pressure in the pressurizing chamber 38 is adjusted by the opening / closing control of the timing control valve 41. Then, the lift timing of the plunger 12 is controlled by the fuel pressure adjustment, and the fuel injection timing from each fuel injection nozzle 4 is adjusted.

A rotation speed sensor 43 composed of an electromagnetic pickup coil is attached to the upper portion of the roller ring 9 so as to face the outer peripheral surface of the pulsar 7. The rotation speed sensor 43 detects passage of the protrusions and the like of the pulsar 7 when they cross, and outputs a timing signal (engine rotation pulse) corresponding to the engine rotation speed NE. Also,
Since this rotation speed sensor 43 is integrated with the roller ring 9, it outputs a reference timing signal to the plunger lift at a constant timing regardless of the control operation of the timer device 34.

Next, the diesel engine 2 will be described. As shown in FIG. 2, in this diesel engine 2, a cylinder 45, a piston 46, and a cylinder head 47.
A main combustion chamber 48 corresponding to each cylinder is formed by. The cylinder head 47 is also provided with auxiliary combustion chambers 49 corresponding to the respective cylinders, and these auxiliary combustion chambers 49 communicate with the main combustion chamber 48. Then, the fuel injected from each fuel injection nozzle 4 is supplied to each auxiliary combustion chamber 49. A well-known glow plug 50 as a start assist device is attached to each sub-combustion chamber 49.

A compressor 54 of a turbocharger 53 is arranged in the intake pipe 52 of the diesel engine 2, and a turbine 56 of the turbocharger 53 is arranged in the exhaust pipe 55. A waste gate valve 57 for adjusting the boost pressure is attached to the exhaust pipe 55. Further, the diesel engine 2 is provided with a recirculation pipe 59 for recirculating a part of the exhaust gas in the exhaust pipe 55 to the intake port 58 of the intake pipe 52. An EGR valve 60 for adjusting the exhaust gas recirculation amount is provided in the middle of the recirculation pipe 59, and the EGR valve 60 is controlled to be opened and closed by the control of a vacuum switching valve (VSV) 61. Further, in the middle of the intake pipe 52, a throttle valve 63 that is opened / closed in association with the depression amount of the accelerator pedal 62 is provided. A bypass passage 64 is formed in parallel with the throttle valve 63, and a bypass throttle valve 65 whose opening and closing is controlled by an actuator 68 according to various operating states is provided in the middle of the bypass passage 64. Actuator 6
8 is driven by the control of two VSVs 66 and 67.

The piezo spill valve 23, the timing control valve 41, the glow plug 50, and the VSVs 61, 66, 67 are electrically connected to an electronic control unit (hereinafter simply referred to as "ECU") 71,
The ECU 71 controls the drive timings thereof.

As a sensor for detecting the operating state of the diesel engine 2, the following sensors are provided in addition to the rotation speed sensor 43. That is, the intake temperature sensor 72 for detecting the intake temperature of the air sucked into the intake pipe 52 via the air cleaner 69, the throttle valve 63.
An accelerator opening sensor 73 for detecting an accelerator opening corresponding to the load of the diesel engine 2 from an open / closed position of the diesel engine 2, an intake pressure sensor 74 for detecting an intake pressure in the intake port 58,
A water temperature sensor 75 for detecting the cooling water temperature of the diesel engine 2, a rotation reference position of the crankshaft 44 of the diesel engine 2, for example, the crankshaft 4 with respect to the top dead center of a specific cylinder.
A crank angle sensor 76 for detecting the rotational position of No. 4 is provided.

Further, a thermocouple 77 as an element temperature detecting means is attached to the piezo spill valve 23. The thermocouple 77 comes into contact with the surface of the piezo element 30 to detect the temperature of the piezo element 30 (element temperature). T) is detected.

Each of the above-mentioned sensors 4 is provided in the ECU 71.
3, 72 to 77 are respectively connected. And E
The CU 71, based on the signals output from the respective sensors 43, 72 to 77, the piezo spill valve 23, the timing control valve 41, the glow plug 50 and the VSV 61,
66, 67 etc. are controlled suitably.

Next, the structure of the above-mentioned ECU 71 will be described with reference to the block diagram of FIG. The ECU 71 is a central processing unit (CPU) 81, a read-only memory (RO) in which a predetermined control program, maps and the like are stored in advance.
M) 82, a random access memory (RAM) 83 for temporarily storing calculation results of the CPU 81, a backup RAM 84 for storing prestored data, and the like, and a bus 87 for connecting these units, an input port 85, an output port 86, and the like.
It is configured as a logical operation circuit connected by.

The CPU 81 detects the charge and discharge timing of the piezo element 30 so as to perform pilot injection at a predetermined timing based on a predetermined crank angle of the diesel engine 2 by the basic timing calculation means and the thermocouple 77. As the temperature rises, it constitutes a timing correction means for accelerating the charge / discharge timing of the piezo element 30.

The intake temperature sensor 7 is connected to the input port 85.
2, the accelerator opening sensor 73, the intake pressure sensor 74, the water temperature sensor 75 and the thermocouple 77 are buffers 88, 89, 9
0, 91, 92, a multiplexer 93 and an A / D converter 94 are connected. Similarly, input port 85
Includes the rotation speed sensor 43 and the crank angle sensor 76.
Are connected via a waveform shaping circuit 95. And
The CPU 81 reads the detection signals of the sensors 43, 72 to 77, etc. input via the input port 85 as input values. In addition, the output port 86 is provided with drive circuits 96, 97,
Piezo spill valve 2 via 98, 99, 100, 101
3, a timing control valve 41, a glow plug 50, VSVs 61, 66, 67, etc. are connected.

The CPU 81 uses the sensors 43, 72
The piezo spill valve 23, the timing control valve 41, the glow plug 50, the VSVs 61, 66, 67 and the like are suitably controlled based on the input values read from ˜77.

Next, the operation and effect of this embodiment configured as described above will be described. The flowchart of FIG. 10 shows a routine executed to correct the charging / discharging timing of the piezo element 30 among the respective processes executed by the CPU 81, and is executed by a regular interrupt every predetermined time.

Prior to the shift to this routine, the CPU 8
1 controls the drive of the piezo spill valve 23,
The fuel pressure is adjusted and main injection and
Pilot injection prior to the main injection is performed. sand
That is, the CPU 81 of the diesel engine 2 at that time
Reference crank angle θ based on operating conditions₀From pie
Pilot injection opening corresponding to lot injection start timing
Start command angle θ₁Corresponding to the pilot injection end timing
Pilot injection end command angle θ₂, Main injection start timing
Main injection start command angle θ₃, And the main injection end
Main injection end command angle θ corresponding to imming_FourTo calculate.
The CPU 81 then determines these command angles θ ₁~ Θ_FourBased on
When the piezo element 30 is charged or discharged via the drive circuit 96,
Power This drives the piezo spill valve 23.
Then, the pilot injection and the main injection are executed.

The process shown in FIG. 10 is performed during such fuel injection control.
When shifting to the routine of, the CPU 81 firstly executes step 1
At 01, the element temperature T of the piezo element 30 at that time is read by the thermocouple 77. Subsequently, the CPU 81 calculates the displacement delay Δt corresponding to the element temperature T in step 102. The calculation of the displacement delay Δt is performed using a map stored in advance in the ROM 82. This map defines the displacement delay (time) Δt with respect to the element temperature T as shown in FIG. In this embodiment, when the element temperature T is low, the piezoelectric element 30 reaches a predetermined expansion amount in a short time, and as the element temperature T rises, the time required for the piezoelectric element 30 to reach the predetermined expansion amount becomes longer. Therefore, a map is defined in which the displacement delay Δt is small when the element temperature T is low, and the displacement delay Δt increases as the element temperature T rises.

Next, the CPU 81 proceeds to step 103, reads the engine speed NE at that time by the rotation speed sensor 43, and converts the displacement delay Δt into an angle at step 104 using the map of FIG. That is, in order to calculate the start and end timings of the pilot injection and the main injection, the displacement delay Δt determined by the time as described above.
To convert the angle. This map shows the engine speed NE
An angle Δθ corresponding to the displacement delay Δt is defined for each time. That is, in this map, the angle Δθ differs depending on the engine speed NE even if the displacement delay Δt is the same, and more specifically, the angle Δθ is defined to increase as the engine speed NE increases. .. And
The CPU 81 shifts to step 105 after performing the angle conversion using the map of FIG.

In step 105, the CPU 81, as shown in FIG. 13, the pilot injection start command angle θ _1a , the pilot injection end command angle θ _2a , the main injection start command angle θ _3a, and the main injection end command angle θ _{4a at that time.} And the command angles θ _{1a to} θ _4a are corrected by subtracting the angle Δθ. C
The PU 81 determines the corrected pilot injection start command angle θ _1b , the pilot injection end command angle θ _2b ,
At a timing corresponding to their command angle theta _1b through? _4b based on the main injection start command angle theta _3b and the main injection end command angle theta _4b,
The piezoelectric element 30 is charged or discharged via the drive circuit 96. As a result, the piezo spill valve 23 is driven, and pilot injection and main injection are executed.

As described above, in this embodiment, the thermocouple 77 is attached to the piezo spill valve 23, and the displacement delay Δt corresponding to the element temperature T of the piezo element 30 detected by the thermocouple 77 is obtained from the map (step 102). ), The displacement delay Δt is converted into an angle Δθ (step 104), and the value is converted into a command angle θ _{1a to} θ for pilot injection and main injection.
_{Since the difference is} subtracted from _4a (step 105), the effect of the displacement delay can be offset by this subtraction.

Therefore, when the element temperature T rises, unlike the prior art in which the applied voltage to the piezoelectric element is increased as the element temperature decreases to keep the charge charge constant and a constant amount of expansion is obtained. In addition, although the time required for the piezoelectric element 30 to reach a predetermined extension amount (response time of the piezoelectric element) increases, this increase can be compensated by advancing the charge / discharge timing as described above. .. As a result, pilot injection can be performed at stable timing without being influenced by the element temperature T, which is advantageous in terms of exhaust emission.

Further, in the present embodiment, when the displacement delay Δt is converted into an angle, a map is used in which the angle Δθ increases as the engine speed NE increases even if the displacement delay Δt is the same. The variation of the angle Δθ due to the variation of the rotational speed NE can also be compensated, and therefore, the displacement delay Δt
Therefore, the accuracy of control of fuel injection timing and the like can be further improved as compared with the case where the angle is converted from.

The present invention is not limited to the configuration of the above-described embodiment, and may be arbitrarily modified within the scope not departing from the spirit of the invention, for example, as follows. In the above-described embodiment, the thermocouple 77 is brought into contact with the piezo element 30 so that the element temperature T of the piezo element 30 is directly detected. However, fuel near the piezo element 30, for example, the high pressure chamber 1
It is also possible to detect the temperatures of the fuel inside the fuel cell 5 and the fuel inside the variable pressure chamber 27, and represent this as the element temperature of the piezo element 30.

[0049]

As described in detail above, according to the present invention, the temperature of the piezoelectric element is detected by the element temperature detection sensor, and as the detected temperature rises, the basic timing calculation means charges and discharges the piezoelectric element. Since the timing is advanced, even if the element temperature rises and the response time of the piezoelectric element displacement becomes long, the displacement delay can be compensated, the pilot injection is executed at a predetermined timing, and the fuel injection timing and fuel The excellent effect that the precision of control of the injection amount can be improved is achieved.

[Brief description of drawings]

FIG. 1 is a conceptual configuration diagram of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a fuel injection pump and a diesel engine in one embodiment embodying the present invention.

FIG. 3 is an enlarged view of the fuel injection pump in FIG.

FIG. 4 is a block diagram showing a configuration of an ECU in one embodiment.

FIG. 5 is a partial cross-sectional view showing a state where the plunger is moved back and fuel is sucked into the high pressure chamber in one embodiment.

FIG. 6 is a partial cross-sectional view showing a state in which the plunger moves forward from the state of FIG. 5 to pressurize the fuel in the high-pressure chamber in one embodiment.

FIG. 7 is a partial cross-sectional view showing a state in which the piezo element is expanded and the spill passage is closed from the state of FIG. 6 in one embodiment.

FIG. 8 is a partial cross-sectional view showing a state where fuel is injected in one embodiment.

FIG. 9 is a partial cross-sectional view showing a state in which the piezo element contracts from the state of FIG. 8 and fuel injection ends in one embodiment.

FIG. 10 is a flowchart for explaining an injection command angle correction process in one embodiment.

FIG. 11 is a diagram showing a map in which a displacement delay with respect to an element temperature is set in one example.

FIG. 12 is a diagram showing a map in which an angle with respect to a displacement delay and an engine speed is determined in order to convert the displacement delay into an angle in one embodiment.

FIG. 13 is a timing chart of control signals output to the piezo spill valve in one embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel injection pump, 2 ... Diesel engine, 4 ... Fuel injection nozzle as a fuel injection valve, 12 ... Plunger,
15 ... High-pressure chamber, 30 ... Piezo element as piezoelectric element, 7
7 ... Thermocouple as element temperature detection sensor, 81 ... C constituting basic timing calculation means and timing correction means
PU, θ ₀ ... Reference crank angle

Claims (1)

Claim: What is claimed is: 1. A fuel which sucks and pressurizes fuel into a high pressure chamber by reciprocating motion of a plunger based on rotation of a diesel engine, and supplies the high pressure fuel pressurized in the high pressure chamber to a fuel injection valve. A fuel injection control that is provided in an injection pump and that expands and contracts by charging and discharging to adjust the pressure of fuel in the high-pressure chamber and performs main injection and pilot injection prior to the main injection by the fuel injection valve. Piezoelectric element, basic timing calculation means for calculating charge / discharge timing of the piezoelectric element to perform pilot injection at a predetermined timing based on a predetermined crank angle of the diesel engine, and temperature of the piezoelectric element is detected. As the element temperature detection sensor and the temperature detected by the element temperature detection sensor rise, the basic timing calculation means Drive control apparatus for a fuel injection control piezoelectric element characterized in that a timing correction means for advancing the discharge timing of the piezoelectric element.