JP2970182B2 - Fuel injection control device for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for controlling fuel injection of a diesel engine mounted on an automobile, for example.

[0002]

2. Description of the Related Art Conventionally, various technologies relating to fuel injection amount control of a diesel engine have been proposed, one of which is disclosed in Japanese Patent Application Laid-Open No. 1-290945. This is intended to compensate for the change in the injection amount due to the change in the fuel temperature, since the fuel injection amount to the diesel engine generally changes when the viscosity changes with the change in the temperature of the fuel. For this purpose, in the above technology, a predetermined fuel temperature (for example, 40 ° C.) is set as a reference temperature, and the fuel injection amount at the reference temperature is set as a reference injection amount. Then, a deviation between the actual fuel temperature detected by the fuel temperature sensor and the reference temperature is obtained, and the reference injection amount is corrected according to the deviation to calculate the fuel injection amount.

[0003]

However, the fuel temperature at the outlet of the fuel injection pump has a correlation with the engine speed. More specifically, as shown in FIG. 10, the fuel temperature THF is low in the low rotation speed range, and the fuel temperature THF increases as the engine speed NE increases. That is, the fuel temperature THF is proportional to the engine speed NE. Therefore, in the prior art in which the reference temperature is set to a constant value regardless of the engine speed NE, the engine speed NE
Is corrected when the fuel temperature THF deviates from the reference temperature due to the change in the fuel injection amount. As a result, the fuel injection amount is corrected even during the normal operation. Originally, an error is unavoidable in the correction. Therefore, if the correction is performed at the normal time as described above, there is a possibility that a new error in the fuel injection amount due to the correction may occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has as its object to compensate for fluctuations in fuel injection amount due to changes in fuel temperature and to make corrections during normal operation. It is an object of the present invention to provide a diesel engine fuel injection control device capable of preventing an error in the fuel injection amount from occurring.

[0005]

In order to achieve the above object, the present invention provides a diesel engine M as shown in FIG.
1, a low-pressure fuel supply mechanism M3a for supplying low-pressure fuel, and a low-pressure fuel from the low-pressure fuel supply mechanism M3a.
2, a pressurizing mechanism M3b for supplying the fuel to the fuel injection valve M2
A fuel injection pump M3 provided with a metering mechanism M3c for adjusting a fuel injection amount from the engine to the diesel engine M1, an operating state detecting means M4 for detecting an operating state of the diesel engine M1, and an operation by the operating state detecting means M4 Injection amount calculation means M5 for calculating the fuel injection amount according to the state
And an injection control means M6 for controlling a metering mechanism M3c of the fuel injection pump M3 in accordance with a calculation result by the injection amount calculation means M5 to adjust a fuel injection amount from the fuel injection valve M2. In the fuel injection control device for a diesel engine, a fuel temperature detecting means M7 for detecting a fuel temperature in a fuel passage downstream of the low-pressure fuel supply mechanism M3a of the fuel injection pump M3, and a rotational speed of the diesel engine M1 are detected. The rotation speed detection means M8, the reference fuel temperature storage means M9 for storing a reference fuel temperature corresponding to the rotation speed of the diesel engine M1, and the reference fuel temperature storage means M9 corresponding to the rotation speed by the rotation speed detection means M8. Is compared with the fuel temperature detected by the fuel temperature detecting means M7, and when the two fuel temperatures do not match, the injection amount calculation is performed. Injection quantity correcting means for correcting the fuel injection amount by step M5 to compare the amount of both the fuel temperature M1
0 is provided.

[0006]

When the diesel engine M1 is operating, its operating state is detected by the operating state detecting means M4. The injection amount calculation means M5 calculates the fuel injection amount according to the operation state by the operation state detection means M4. Then, the injection control means M6 controls the metering mechanism M3c of the fuel injection pump M3 according to the calculation result by the injection amount calculation means M5, and adjusts the fuel injection amount from the fuel injection valve M2.

During such fuel injection into the diesel engine M1, the fuel temperature in the fuel passage downstream of the low-pressure fuel supply mechanism M3a of the fuel injection pump M3 is detected by the fuel temperature detecting means M7. Further, the rotational speed of the diesel engine M1 is detected by the rotational speed detecting means M8.

[0008] Then, the injection amount correction means M10 compares the reference fuel temperature in the reference fuel temperature storage means M9 corresponding to the rotation speed by the rotation speed detection means M8 with the fuel temperature by the fuel temperature detection means M7. Here, the reference fuel temperature is a value stored in advance in the reference fuel temperature storage means M9, and is set according to the rotation speed of the diesel engine M1. This reference fuel temperature is the fuel temperature detected with the highest probability among the fuel temperatures when the diesel engine M1 is in the normal operation state.

[0009] If the two fuel temperatures do not match as a result of the comparison between the reference fuel temperature and the actual fuel temperature, the injection amount correcting means M10 calculates the fuel injection amount by the injection amount calculating means M5 as the fuel temperature. Is corrected according to the comparison amount of. This correction compensates for a change in the fuel injection amount due to a change in the fuel temperature.

When the actual fuel temperature coincides with the reference fuel temperature, the injection amount correcting means M10 does not correct the fuel injection amount by the injection amount calculating means M5.
For this reason, it is difficult to correct the fuel injection amount in the normal operation state, and errors caused by the correction are reduced.

[0011]

FIG. 2 shows an embodiment of the present invention.
This will be described with reference to FIG. FIG. 2 is a diagram showing a schematic configuration of an automotive diesel engine 2 provided with the fuel injection control device of the present embodiment, and FIG. 3 is a cross-sectional view of a distribution type fuel injection pump 1 for injecting fuel into the diesel engine 2. is there.
As shown in FIG. 2, the fuel injection pump 1 includes a drive pulley 3 that is drivingly connected to a crankshaft 40 of the 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,
Fuel is pressure-fed to a fuel injection nozzle 4 as a fuel injection valve provided for each cylinder of the diesel engine 2 to perform fuel injection.

As shown in FIG. 3, a drive shaft 5 is connected to the drive pulley 3. The drive shaft 5 includes a fuel feed pump (developed at 90 degrees in the figure) as a low-pressure fuel supply mechanism composed of a vane pump, and a disk-shaped pulsar 7 having a plurality of protrusions on the outer peripheral surface. Is installed. The base end (the right end in the figure) of the drive shaft 5 is connected to the cam plate 8 via a coupling (not shown). A roller ring 9 is interposed 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 mounted on the roller ring 9. The cam plate 8 is constantly biased and engaged with the cam roller 10 by the spring 11.

A plunger 12 for pressurizing fuel is mounted on the cam plate 8 so as to be integrally rotatable, and the rotational force of the drive shaft 5 is transmitted to the cam plate 8 via a coupling, thereby causing the cam plate 8 to rotate. 8 and the plunger 12 are reciprocally driven in the horizontal direction in the figure while rotating. The plunger 12 is fitted into a cylinder 14 formed in the pump housing 13, and a high-pressure chamber 15 is provided between a front end surface (right end surface in the figure) of the plunger 12 and an inner bottom surface of the cylinder 14. The same number of intake grooves 16 and distribution ports 17 as the number of cylinders of the diesel engine 2 are formed on the outer periphery of the distal end of the plunger 12. Further, a distribution passage 18 and a suction port 19 are formed in the pump housing 13 corresponding 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. In the suction stroke in which the plunger 12 moves to the left in the drawing (returns) and the high-pressure chamber 15 is depressurized, one of the suction grooves 16 communicates with the suction port 19 to move the fuel chamber 21 from the high-pressure chamber 15. Fuel is introduced to On the other hand, the plunger 12 moves rightward in the figure (forward movement).
In the compression stroke in which the high-pressure chamber 15 is pressurized, the fuel is pressure-fed from the distribution passage 18 to the fuel injection nozzle 4 of each cylinder and injected.

In this embodiment, a pressurizing mechanism for pressurizing the low-pressure fuel from the fuel feed pump 6 and supplying it to the fuel injection nozzle 4 by the plunger 12, the cylinder 14, the high-pressure chamber 15, and the like. Is configured.

A spill passage 22 for fuel overflow that connects the high-pressure chamber 15 and the fuel chamber 21 is provided in the pump housing 13.
Is formed, and an electromagnetic spill valve 23 is provided on the way. The electromagnetic spill valve 23 is a normally open type valve. When the coil 24 is not energized (off), the valve body 25 is opened and the fuel in the high-pressure chamber 15 overflows to the fuel chamber 21. When the coil 24 is energized (turned on), the valve body 25 is closed, and the overflow of fuel from the high-pressure chamber 15 to the fuel chamber 21 is stopped.

Therefore, by controlling the energization time of the electromagnetic spill valve 23, the electromagnetic spill valve 23 is controlled to close and open, and the overflow rate of fuel from the high-pressure chamber 15 to the fuel chamber 21 is adjusted. Then, by opening the electromagnetic spill valve 23 during the compression stroke of the plunger 12, the fuel in the high-pressure chamber 15 is reduced in pressure, and the fuel injection from the fuel injection nozzle 4 is stopped. That is, even when the plunger 12 moves forward, the high-pressure chamber 15 remains open while the electromagnetic spill valve 23 is open.
The fuel pressure in the inside does not increase, and the fuel injection from the fuel injection nozzle 4 is not performed. Also, during the forward movement of the plunger 12,
By controlling the timing of closing and opening the electromagnetic spill valve 23, the amount of fuel injected from the fuel injection nozzle 4 is controlled.

In the present embodiment, the spill passage 22 and the electromagnetic spill valve 23 constitute a metering mechanism for adjusting the fuel injection amount from the fuel injection nozzle 4 to the diesel engine 2.

Below the pump housing 13, there is provided a timer device (developed at 90 degrees in the figure) 26 for controlling the fuel injection timing. The timer device 26 controls the timing at which the cam face 8a engages the cam roller 10, that is, the reciprocating timing of the cam plate 8 and the plunger 12, by controlling the position of the roller ring 9 with respect to the rotation direction of the drive shaft 5. It is.

The timer device 26 is operated by hydraulic pressure, and includes a timer housing 27, a timer piston 28 fitted in the timer housing 27, and a low-pressure chamber 29 on one side of the timer housing 27. It includes a timer spring 31 for urging the timer piston 28 toward the other pressure chamber 30 and the like. The timer piston 28 is connected to the roller ring 9 via a slide pin 32.

In the pressurizing chamber 30 of the timer housing 27,
The fuel pressurized by the fuel feed pump 6 is introduced. The position of the timer piston 28 is determined by the balance between the fuel pressure and the urging force of the timer spring 31. Accordingly, the position of the roller ring 9 is determined, and the reciprocating timing of the plunger 12 via the cam plate 8 is determined.

In order to control the fuel pressure of the timer device 26, a timing control valve (TCV) 33 is provided in a communication passage 34 connecting the pressurizing chamber 30 and the low-pressure chamber 29. The TCV 33 is an electromagnetic valve whose opening and closing is controlled by a duty-controlled energization signal, and the fuel pressure in the pressurizing chamber 30 is adjusted by opening and closing the TCV 33. The plunger 12 is adjusted by the fuel pressure adjustment.
Is controlled, and the fuel injection timing from each fuel injection nozzle 4 is adjusted.

A rotation speed sensor 35 as rotation speed detecting means is mounted on the roller ring 9 so as to face the outer peripheral surface of the pulser 7. This rotation speed sensor 3
Reference numeral 5 denotes an electromagnetic pickup coil which detects passage of a projection or the like of the pulsar 7 when the projection or the like crosses and outputs a timing signal (engine rotation pulse) corresponding to the engine speed. Further, since the rotation speed sensor 35 is integrated with the roller ring 9, the rotation speed sensor 35 outputs a reference timing signal to the plunger lift at a constant timing regardless of the control operation of the timer device 26.

The pump housing 13 has a temperature (fuel temperature) T of fuel supplied to the diesel engine 2.
A fuel temperature sensor 36 is mounted as fuel temperature detecting means for detecting HF. The mounting position of the fuel temperature sensor 36 needs to be on the downstream side (outlet side) of the fuel feed pump 6 in the fuel passage of the fuel injection pump 1. This is because the fuel temperature in the fuel injection pump 1 is not constant, and the fuel is heated by the fuel feed pump 6 or the like, and the fuel temperature rises. Therefore, the fuel temperature THF is represented by the temperature of the outlet portion close to the diesel engine 2. The fuel temperature sensor 36 has a built-in thermistor whose electric resistance changes greatly depending on the temperature, and detects a change in the fuel temperature by a change in the electric resistance of the thermistor.

Next, the diesel engine 2 will be described. As shown in FIG. 2, in this diesel engine 2, a cylinder 41, a piston 42 and a cylinder head 43 are provided.
Accordingly, a main combustion chamber 44 is formed for each cylinder, and a sub-combustion chamber 45 is connected to each main combustion chamber 44. Then, the fuel injected from each fuel injection nozzle 4 is supplied to each sub combustion chamber 45. A glow plug 46 as a start-up assisting device is attached to each sub-combustion chamber 45.

An intake pipe 47 and an exhaust pipe 50 are connected to the diesel engine 2, respectively. A compressor 49 of a turbocharger 48 is provided in the intake pipe 47, and a turbine 5 of the turbocharger 48 is provided in the exhaust pipe 50.
1 is provided. A waste gate valve 52 for adjusting the supercharging pressure is attached to the exhaust pipe 50.

The exhaust pipe 50 and the intake pipe 47 are connected to the recirculation pipe 5.
The exhaust pipe 50 is connected to the exhaust pipe 50 so that a part of the exhaust gas can be recirculated to the intake pipe 47. An EGR valve 55 for adjusting the amount of exhaust gas recirculation (EGR amount) is provided in the middle of the recirculation pipe 54. This E
The negative pressure applied to the diaphragm chamber of the GR valve 55 is:
It is controlled by a vacuum switching valve (VSV) 56.

Further, a throttle valve 58 which is opened and closed in conjunction with an accelerator pedal 57 provided in a driver's seat is provided in the intake pipe 47. A bypass 59 is formed in parallel with the throttle valve 58, and a bypass throttle valve 60 is provided in the bypass 59 so as to be openable and closable. The opening and closing of the bypass throttle valve 60 is controlled by an actuator 63. Actuator 63
, A negative pressure generated by a negative pressure pump (not shown) is supplied through two VSVs 61 and 62.

The electromagnetic spill valve 23, the TCV 33, the glow plug 46, and the VSVs 56, 61, 62 are electrically connected to an electronic control unit (hereinafter simply referred to as "ECU") 71, and their drive timing is controlled by the ECU 7.
1 is controlled.

As sensors for detecting the operating state of the diesel engine 2, the following sensors are provided in addition to the rotation speed sensor 35. An intake air temperature sensor 72 for detecting the intake air temperature THA of the air taken into the intake pipe 47 via the air cleaner 64, and an accelerator opening for detecting an accelerator opening ACCP corresponding to the load of the diesel engine 2 from the open / close position of the throttle valve 58. A sensor 73, an intake pressure sensor 74 for detecting a supercharging pressure PiM in the suction port 53, a water temperature sensor 75 for detecting a cooling water temperature THW of the diesel engine 2, a rotation reference position of the crankshaft 40 of the diesel engine 2, for example, a specific cylinder. A travel angle (vehicle speed) is detected by turning on / off a reed switch 77b by a crank angle sensor 76 for detecting the rotational position of the crankshaft 40 with respect to the top dead center, and a magnet 77a rotated by rotation of a transmission gear (not shown). Vehicle speed sensor 7
7 are provided.

The ECU 71 includes the above-mentioned sensors 3
5, 36, 72 to 77 are respectively connected. Then, based on signals output from the sensors 35, 36, 72 to 77, the ECU 71 determines whether the electromagnetic spill valve 23, the TCV
33, the glow plug 46, the VSVs 56, 61, 62 and the like are suitably controlled.

Next, the configuration of the ECU 71 will be described with reference to the block diagram of FIG. ECU 71
Is a central processing unit (CPU) 81 that constitutes an injection amount calculation unit, an injection control unit, and an injection amount correction unit; a read-only memory (ROM) as a reference fuel temperature storage unit that stores a predetermined control program, a map, and the like in advance. 82, CP
A random access memory (RAM) 83 for temporarily storing the operation results of U81, a backup RAM 84 for storing data stored in advance, and an input port 85 and an output port 86 are connected as a logical operation circuit by a bus 87.

The input port 85 is connected to the intake air temperature sensor 7.
2. The accelerator opening sensor 73, the intake pressure sensor 74, the water temperature sensor 75 and the fuel temperature sensor 36 are provided with buffers 88 and 8.
9, 90, 91, 80, multiplexer 92 and A / D
It is connected via a converter 93. The input port 85 includes the rotation speed sensor 35 and the crank angle sensor 7.
6 and a vehicle speed sensor 77 are connected via a waveform shaping circuit 95. Then, the CPU 81 reads, as input values, detection signals of the respective sensors 35, 36, 72 to 77, etc., which are input via the input port 85. Output port 8
6 includes drive circuits 96, 97, 98, 99, 100, 10
1, the electromagnetic spill valve 23, the TCV 33, the glow plug 46, and the VSVs 56, 61, 62 are connected.

Then, the CPU 81 controls the sensors 35, 3
Based on the input values read from 6, 36, 72-77,
The electromagnetic spill valve 23, the TCV 33, the glow plug 46, and the VSVs 56, 61, 62 are suitably controlled.

Next, the operation and effect of the embodiment constructed as described above will be described. The flowchart of FIG. 5 shows a routine for calculating the fuel temperature THF among the processes executed by the CPU 81, and is started every predetermined time (one second in this embodiment). 6 shows a routine for controlling the fuel injection amount to the diesel engine 2 using the fuel temperature THF in FIG. 5, and is started at a predetermined timing.

First, the fuel temperature calculation routine of FIG. 5 will be described. When the CPU 81 shifts to this routine,
In step 101, the electric resistance value of the thermistor is calculated from the detected value (voltage value) of the fuel temperature sensor 36, and in step 102, it is determined whether or not the resistance value is within a predetermined range. This predetermined range is a range in which the resistance value of the fuel temperature sensor 36 can be taken during normal operation without any trouble such as disconnection. If the resistance value is within the predetermined range, the CPU 81 determines that the fuel temperature sensor 36 is operating normally, and calculates the fuel temperature THF corresponding to the resistance value in step 103. For this calculation, for example, a map in which the fuel temperature THF with respect to the resistance value (or the voltage value) is specified in advance is used.

If the resistance value is out of the predetermined range in step 102, the CPU 81 calculates that the fuel temperature sensor 36 is abnormal, and that the fuel temperature sensor 36 uses the resistance value of the fuel temperature sensor 36 to calculate an incorrect fuel temperature THF. Then, in step 104, the fuel temperature at the time of failure is calculated using the map of FIG. This map defines a reference fuel temperature α according to the engine speed NE.
It is stored in the ROM 82 in advance. The reference fuel temperature α is
Outlet portion (spill passage 22) when the fuel temperature at the inlet (fuel supply port 20) of the fuel injection pump 1 is 40 ° C.
The fuel temperature at That is, the reference fuel temperature α is the fuel temperature detected with the highest probability among the fuel temperatures when the diesel engine 2 is in the normal operation state.
As is apparent from FIG. 9, the reference fuel temperature α is substantially proportional to the engine speed NE.

After calculating the fuel temperature THF in steps 103 and 104, the CPU 81 ends this routine. Next, the routine of FIG. 6 will be described. When the process proceeds to this routine, the CPU 81 first determines in step 201 the engine speed NE, the accelerator opening ACCP, and the supercharging based on the detection values from the rotation speed sensor 35, the accelerator opening sensor 73, and the intake pressure sensor 74. Each pressure PiM is read.

In step 202, the CPU 81 calculates a basic fuel injection amount QBASE based on the values read in step 201. The calculation of the basic injection amount QBASE is based on the engine speed NE and the accelerator opening ACCP.
Is performed with reference to a map (not shown) using the parameter as a parameter. In addition, the CPU 8
1 is the cooling water temperature THW and accelerator opening ACC as required
Based on the values such as P and the engine speed NE, the low-temperature start increasing correction, the rapid deceleration increasing correction, and the like are performed.

Next, the CPU 81 determines in steps 203 to 20
In step 9, a calculation process of the maximum injection amount QFULL is performed based on the following equation (1). This maximum injection amount QFULL means the limit of the injection amount for the intake air to the diesel engine 2. QFULL = (MIN [K2 / K3 / QSPF1, QSPF2] + QSP0) KTF KNFI + QMAX + QFIX (1) In equation (1), (K2 / K3 / QSPF1) is the maximum injection amount on the diesel engine 2 side. Here, K2 is an intake pressure correction coefficient for correcting the basic injection amount characteristic according to the intake pressure, and is obtained from a one-dimensional map of the supercharging pressure PiM. K3 is an intake temperature correction coefficient for reducing the basic maximum injection amount characteristic when the intake air temperature is equal to or higher than a predetermined temperature, and is obtained from a one-dimensional map of the intake temperature THA. QSPF1 is the maximum injection increase and is obtained from a one-dimensional map of the engine speed NE. QSPF2 is the maximum injection amount on the transmission side.

MIN [K2, K3, QSPF1, QSP
F2] is the maximum injection amount (K2
・ K3 ・ QSPF1) and the maximum injection amount QSP on the transmission side
This means that the smaller maximum injection amount of F2 is selected (validated).

QSP0 is the maximum injection amount offset amount, which is obtained from a one-dimensional map of the engine speed NE. KTF is a fuel temperature correction coefficient. KNFI is
This is a correction coefficient for integration control for correcting the maximum injection amount QFULL according to the magnitude of variation due to aging of the fuel injection pump 1 or differences in fuel properties, and is obtained from a map. QMAX is a maximum injection amount correction amount at the time of cold. QF
IX is a fixed injection amount, which is calculated according to a calculation formula determined using the engine speed NE.

In step 203 of FIG. 6, the CPU 81 determines an intake pressure correction coefficient K2, an intake temperature correction coefficient K3, a maximum injection increase amount QSPF1, a maximum injection amount QSPF2 on the transmission side, a maximum injection amount offset amount QSP0, and correction for integral control. Coefficient KN
FI, the maximum injection amount correction amount QMAX at the time of cold, and the fixed injection amount QFIX are calculated according to a map, an arithmetic expression or the like.

Next, the CPU 81 determines in step 204 that FIG.
Is used to calculate the reference fuel temperature α corresponding to the engine speed NE in step 201. Then, C
In step 205, the PU 81 calculates two correction coefficients KTFC and KTFH for correcting the fuel temperature correction coefficient KTF according to the engine speed NE at that time.
The maps of FIG. 7 and the map of FIG. 8 are used to calculate both correction coefficients KTFC and KTFH. The former correction coefficient KT
FC is a correction coefficient used when the fuel temperature THF is lower than the reference fuel temperature α, and the latter correction coefficient KTF
H is a correction coefficient used when the fuel temperature THF is higher than the reference fuel temperature α.

Then, in step 206, the CPU 81 determines whether or not the fuel temperature THF obtained in the routine of FIG. 5 is equal to or higher than the reference fuel temperature α. The CPU 81
If THF ≧ α, the process proceeds to step 207, where THF <
If it is α, the process moves to step 208. Step 207
The CPU 81 calculates the correction coefficient KTFH and the fuel temperature TH
Using F and the reference fuel temperature α, a fuel temperature correction coefficient KTF is calculated according to the following equation (2).

KTF = 1 + KTFH · (THF−α) (2) That is, when the fuel temperature THF is equal to or higher than the reference fuel temperature α, the fuel viscosity is low and the fuel injection amount is small. for that reason,
In order to increase the fuel injection amount, the fuel temperature correction coefficient KTF is set to "1" or more by the equation (2).

In step 208, the CPU 81 determines the correction coefficient KTFC, the fuel temperature THF, and the reference fuel temperature α.
And the fuel temperature correction coefficient KTF according to the following equation (3):
Is calculated.

KTF = 1−KTFC · (α-THF) (3) That is, when the fuel temperature THF is lower than the reference fuel temperature α, the viscosity of the fuel is high and the fuel injection amount is large. Therefore, the fuel temperature correction coefficient KTF is set to “1” or less in the equation (3) so that the fuel injection amount is reduced.

When the fuel temperature correction coefficient KTF is determined in steps 207 and 208 as described above, the CPU 81 uses the values in step 203 in step 209,
The maximum injection amount QFULL is calculated based on the above equation (1). Then, the CPU 81 shifts to step 210, where the basic injection amount QBASE previously calculated in step 202 is
The value is compared with the maximum injection amount QFULL in step 209, and the smaller value is set as the final injection amount QFIN. Subsequently, in step 211, the CPU 81 sets the injection amount command value T corresponding to the final injection amount QFIN.
SP is obtained, and in step 212, the obtained injection amount command value TSP is output, and this routine ends. The output of the injection amount command value TSP controls the drive of the electromagnetic spill valve 23 to execute fuel injection.

As described above, in this embodiment, the reference fuel temperature α corresponding to the engine speed NE is set in advance, and this is set as the standard state of the fuel temperature (map in FIG. 9). And
The reference fuel temperature α corresponding to the engine speed NE is obtained by the speed sensor 35 (step 204).
Based on the detection result from the fuel temperature sensor 36, the fuel temperature THF at the exit portion of the fuel injection pump 1 at that time is calculated (step 103). Then, the reference fuel temperature α is compared with the fuel temperature THF (step 206). Here, the reference fuel temperature α is the fuel temperature detected with the highest probability among the fuel temperatures when the diesel engine 2 is in the normal operation state. When the two fuel temperatures do not match (when not in the normal operation state), the fuel injection amount is corrected by a correction amount (fuel temperature correction coefficient KTF) according to the comparison result (steps 207, 208, 209). This correction compensates for a change in the fuel injection amount due to a change in the fuel temperature.

When the diesel engine 2 is in the normal operation state, the fuel temperature THF becomes equal to the reference fuel temperature α. Therefore, (THF-α) and (α-THF) on the right side in the above equations (2) and (3) are “0”, and the fuel temperature correction coefficient KTF is “1”. That is,
During normal operation, the fuel injection amount is not corrected by the fuel temperature correction coefficient KTF. For this reason, the error caused by the correction during the normal operation state is reduced.

In this embodiment, the following effects are obtained when the fuel temperature sensor 36 is abnormal. That is, conventionally, when the fuel temperature sensor 36 breaks down, the fuel injection amount is generally corrected so that the fuel injection amount is smaller than in the normal state. According to this concept, in order to perform the above-mentioned decrease correction over the entire region of the engine speed NE, it is necessary to set the reference fuel temperature A to be lower than the fuel temperature THF at the time of low rotation, as shown by a dashed line in FIG. is there. However, in this case, as the engine speed NE becomes higher, the difference between the reference fuel temperature A and the actual fuel temperature THF becomes larger, and especially in a high speed region, an extreme decrease correction is performed, and the drivability deteriorates. Let me do it.

On the other hand, in the present embodiment, since the reference fuel temperature α corresponding to the engine speed NE is used as described above, even if the fuel temperature sensor 36 fails, the same correction as in the normal state is performed. be able to. For this reason, no extreme weight loss correction is performed in a high rotation range or the like, and the above-described deterioration in drivability can be prevented.

In the above-described embodiment, the present invention is embodied in the diesel engine 2 provided with a supercharger (turbocharger 48). However, a diesel engine provided with a supercharger as a supercharger, It can also be embodied in a diesel engine that does not have a diesel engine.

The mounting position of the fuel temperature sensor 36 is not particularly limited as long as it is an outlet portion of the fuel passage of the fuel injection pump 1. The outlet portion here is a fuel passage downstream of the fuel feed pump 6, that is, a portion other than the fuel supply port 20 to the fuel feed pump 6.

[0056]

As described above in detail, according to the present invention, the reference fuel temperature corresponding to the rotational speed of the diesel engine is stored, and the reference fuel temperature corresponding to the rotational speed of the diesel engine at that time is stored. Compare with the fuel temperature at the time,
When the two fuel temperatures do not match, the fuel injection amount is corrected in accordance with the comparison amount between the two fuel temperatures. Thus, while compensating for the change in the fuel injection amount caused by the change in the fuel temperature, the fuel injection amount is corrected in the normal operation state. There is an excellent effect that it is possible to prevent the occurrence of an error in the fuel injection amount due to the occasional correction.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram showing a supercharged diesel engine and a control device for controlling a fuel injection amount to the diesel engine according to an embodiment of the present invention;

FIG. 3 is a sectional view of a fuel injection pump according to one embodiment.

FIG. 4 is a block diagram illustrating an electrical configuration of an ECU according to one embodiment.

FIG. 5 is a flowchart illustrating a fuel temperature calculation routine in one embodiment.

FIG. 6 is a flowchart illustrating a fuel injection control routine in one embodiment.

FIG. 7 is a diagram showing a map in which a correction coefficient for an engine speed is defined in one embodiment.

FIG. 8 is a diagram showing a map in which a correction coefficient for an engine speed is defined in one embodiment.

FIG. 9 is a diagram showing a map in which a reference fuel temperature with respect to an engine speed is defined in one embodiment.

FIG. 10 is a graph showing the relationship between the engine speed and the fuel temperature at the outlet of the fuel injection pump.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel injection pump, 2 ... Diesel engine, 4 ... Fuel injection nozzle as fuel injection valve, 6 ... Fuel feed pump as low-pressure fuel supply mechanism, 12 ... Plunger which constitutes a part of pressurization mechanism, 14 ... A cylinder forming a part of the pressurizing mechanism, 15 ... a high-pressure chamber forming a part of the pressurizing mechanism,
Reference numeral 22: a spill passage forming a part of the metering mechanism; 23, an electromagnetic spill valve forming a part of the metering mechanism; 35, a rotation speed sensor as a rotation speed detecting means; Temperature sensor 73, accelerator opening degree sensor forming part of operating state detecting means 74, intake pressure sensor forming part of operating state detecting means 75, water temperature sensor forming part of operating state detecting means , 81: CP as injection amount calculation means, injection control means, and injection amount correction means
U, 82: ROM as reference fuel temperature storage means

Claims (1)

(57) [Claims] 1. A fuel injection valve for injecting high-pressure fuel into a diesel engine, a low-pressure fuel supply mechanism for supplying low-pressure fuel, and a fuel supply valve for pressurizing low-pressure fuel from the low-pressure fuel supply mechanism and supplying the fuel to the fuel injection valve. A fuel injection pump having a pressure mechanism, and a metering mechanism for adjusting a fuel injection amount from the fuel injection valve to the diesel engine; an operating state detecting means for detecting an operating state of the diesel engine; and an operating state detecting means A fuel injection amount calculating means for calculating a fuel injection amount according to the operating state of the fuel injection pump, and controlling a metering mechanism of the fuel injection pump in accordance with a calculation result by the injection amount calculating means, thereby injecting fuel from the fuel injection valve. A fuel injection control device for a diesel engine, comprising: an injection control means for adjusting an amount of fuel, wherein a fuel downstream of a low-pressure fuel supply mechanism of the fuel injection pump is provided. Fuel temperature detection means for detecting a fuel temperature in a road; rotation speed detection means for detecting a rotation speed of the diesel engine; reference fuel temperature storage means for storing a reference fuel temperature according to the rotation speed of the diesel engine; Compare the reference fuel temperature in the reference fuel temperature storage means corresponding to the rotation speed by the rotation speed detection means, and the fuel temperature by the fuel temperature detection means, when both fuel temperatures do not match,
A fuel injection control device for a diesel engine, comprising: an injection amount correction unit that corrects a fuel injection amount by the injection amount calculation unit according to a comparison amount between the two fuel temperatures.