JPH04339152A - Control device for fuel injection of internal combustion engine - Google Patents

Abstract

PURPOSE:To speedily increase engine speed by reducing driving torque for a fuel injection pump at the time of starting an engine. CONSTITUTION:A fuel relief passage 50 is branched from the pressurized chamber 34 of a fuel injection pump 32 always driven by an engine. A control valve 52 to control the quantity of fuel returned from the chamber 34 into a fuel tank 48 is arranged in the fuel relief passage 50. At the time of starting the engine, the valve closing time of the control valve 52 is controlled in feedback mode so that fuel pressure P detected by a pressure sensor 55 in a common rail 29 may attain a low target fuel pressure, and the fuel is jetted through a low pressure fuel injection valve 26 into the collecting part of an air supply passage. On the other hand, during the ordinary operation of the engine after its starting, the valve closing time of the control valve 52 is controlled in feedback mode so that the fuel pressure P may attain a high target fuel pressure, and the fuel is jetted through a high pressure fuel injection valve 25 into a combustion chamber 5.

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 system for an internal combustion engine.

0002

[Prior Art] A fuel injection system for an internal combustion engine, which includes a fuel injection pump that is constantly driven by the engine, a fuel injection valve that is placed in the engine combustion chamber, and a fuel injection valve that is placed in the engine air supply passage. is publicly known (Japanese Unexamined Patent Publication No. 58-91367
(see publication). In this internal combustion engine, a fuel injection pump is directly connected to the engine crankshaft via a V-belt, and the fuel injection pump is driven by the engine to constantly pressurize fuel to a high pressure.

0003

By the way, when the engine is cranked by the starter motor at the time of starting the engine, it is desirable that the cranking rotational speed increases quickly so that the engine can be started quickly. However, in the above-mentioned internal combustion engine, the fuel injection pump is constantly driven by the engine to pressurize the fuel to high pressure even when the engine is started, and as a result, the loss of work for driving this fuel injection pump is large, resulting in a decrease in engine speed. The problem is that it does not rise quickly. In order to reduce the drive loss work of the fuel injection pump and quickly increase the engine speed when starting the engine, the fuel injection pump is connected to the engine via an electromagnetic clutch, for example, and It is conceivable to stop the fuel injection pump by releasing the connection between the fuel injection pump and the engine using an electromagnetic clutch during a predetermined period. However, providing the electromagnetic clutch in this manner not only complicates the drive mechanism of the fuel injection pump but also causes problems such as an increase in cost.

0004

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a fuel injection pump that is constantly driven by the engine, a fuel injection valve that is disposed in the engine combustion chamber or in the engine air supply passage. A fuel injection control device for an internal combustion engine, comprising a control valve that branches a fuel relief passage from a pressurizing chamber or a discharge side of a fuel injection pump and controls the amount of fuel discharged through the fuel relief passage. By controlling the opening and closing of the control valve, the pressure of the fuel supplied to the fuel injection valve when starting the engine is made lower than the pressure after starting the engine.

[0005]

[Operation] The fuel injection pump is constantly driven by the engine. When the engine is started, the control valve is controlled to open and close so that the pressure of the fuel supplied to the fuel injection valve is lower than the pressure after the engine is started, and as a result, the amount of fuel discharged through the fuel relief passage is increased. In this way, the driving torque of the fuel injection pump is reduced when starting the engine, so that the engine speed can be quickly increased.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a case where the present invention is applied to a spark ignition two-stroke internal combustion engine. Referring to Figure 1, 1 is the engine body, 2 is the piston, 3 is the crankshaft, 4 is the cylinder head, 5 is the combustion chamber, 6 is the intake valve, 7 is the intake port, 8 is the exhaust valve, 9 is the exhaust The ports are shown respectively. An ignition plug 10 is arranged at the center of the inner wall surface of the cylinder head 4. Further, on the inner wall surface of the cylinder head 4, in order to ensure good loop scavenging, there is a mask that covers the opening between the intake valve periphery and the valve seat on the exhaust valve 8 side throughout the opening period of the intake valve 6. A wall 11 is formed.

The air intake port 7 of each cylinder is connected to a common surge tank 15 for each cylinder via a corresponding air intake branch pipe 14. This surge tank 15 has a mechanical supercharger 16 connected to the crankshaft 3 and driven by the engine.
The mechanical supercharger 16 is connected to its discharge side via an air supply duct 17, and the suction side of the mechanical supercharger 16 is connected to an air supply duct 18. The air supply duct 18 is connected to an air cleaner 20 via an air flow meter 19, and a throttle valve 21 is disposed within the air supply duct 18.

A high-pressure fuel injection valve 25 for injecting fuel into the combustion chamber 5 is attached to the cylinder head 4, and a low-pressure fuel injection valve 25 for injecting fuel into the combustion chamber 5 is attached to the gathering part of the air supply branch pipe 14. A fuel injection valve 26 is arranged. The high-pressure fuel injection valve 25 is connected to a common rail 29 via a corresponding fuel distribution pipe 28, and the common rail 29 is connected to a pressurizing chamber 34 of a fuel injection pump 32 via a fuel discharge passage 30. At the connection part between the fuel discharge passage 30 and the pressurizing chamber 34,
A check valve 36 is arranged to allow fuel to flow only from the pressurizing chamber 34 to the fuel discharge passage 30. Further, a fuel branch passage 38 branches off from the fuel discharge passage 30, and this fuel branch passage 38 is connected to the low pressure fuel injection valve 26.

The fuel injection pump 32 includes a cylinder 40 and a plunger 41 that is reciprocatably inserted into the cylinder 40.
The above-mentioned pressurizing chamber 34 is formed by the inner wall surface of the cylinder 40 and the top surface of the plunger 41. The plunger 41 is pressed against a cam 44 formed on a camshaft 43 by a compression spring 42, and the camshaft 43 is connected to the crankshaft 3 via a belt 45. Therefore, as the crankshaft 3 rotates, the cam 44
is rotated, and as a result, the plunger 41 is caused to reciprocate within the cylinder 40. In the embodiment shown in FIG. 1, when the crankshaft 3 makes one revolution, the cam 4
4 rotates once, that is, 1 of piston 2
The plunger 41 is configured to make one reciprocating motion for each reciprocating motion.

The cylinder 40 of the fuel injection pump 32 is connected via a fuel supply passage 47 to a fuel supply pump 49 disposed within a fuel tank 48 . Also, fuel injection pump 3
A fuel relief passage 50 is branched from the second pressurizing chamber 34, and the fuel relief passage 50 is connected to the fuel tank 48. A control valve 52 for controlling the amount of fuel discharged from the pressurizing chamber 34 via the fuel relief passage 50 is disposed within the fuel relief passage 50 . The control valve 52 is opened and closed by an actuator 53 including, for example, a solenoid, and the actuator 53 is controlled by an output signal from an electronic control unit 60.

The electronic control unit 60 is composed of a digital computer, and includes a ROM (read only memory) 62, a RAM (random access memory) 63, a CPU (microprocessor) 64, and a backup RAM 65, which are interconnected by a bidirectional bus 61. , input port 6
6 and an output port 67. Air flow meter 19 generates an output voltage proportional to intake air amount Q, and this output voltage is input to input port 66 via AD converter 68 . Also, common rail 29 has common rail 29.
A pressure sensor 55 that generates an output voltage proportional to the fuel pressure P inside is attached, and the output voltage of this pressure sensor 55 is inputted to an input port 66 via an AD converter 69. Further, a water temperature sensor 56 that generates an output voltage proportional to the engine cooling water temperature TW is attached to the engine body 1, and the output voltage of this water temperature sensor 56 is inputted to the input port 66 via the AD converter 70. Furthermore, the input port 66 includes an ignition switch 57, a crank angle sensor 58 that generates an output pulse every time the crankshaft 3 rotates, for example, by 30 degrees, and an output signal that generates, for example, an output signal indicating that the No. 1 cylinder is at top dead center. A top dead center detection sensor 59 is connected. On the other hand, the output port 67 has a corresponding drive circuit 72,
It is connected to the actuator 53 of the spark plug 10, the low pressure fuel injection valve 26, the high pressure fuel injection valve 25, and the control valve 52 via 73, 74, and 75.

Next, referring to FIGS. 1 and 2, the operation of the fuel injection pump 32 and the fuel pressure P in the common rail 29 will be explained.
The control method will be explained below. The fuel supplied from the fuel tank 48 into the fuel supply pump 49 is fed to the fuel supply pump 4
9, a predetermined pressure Pf, for example 0.2M
The pressure of the fuel is increased to Pa, and the fuel that has been increased to this pressure Pf is supplied into the pressurizing chamber 34 of the fuel injection pump 32 through the fuel supply passage 47 when the plunger 41 is located near the bottom dead center. When the plunger 41 rises past the bottom dead center, the fuel supply passage 47 is closed off from the pressurizing chamber 34 by the outer peripheral wall surface of the plunger 41. Next, the plunger 41
If the control valve 52 is open when the pressure rises further, the fuel in the pressurizing chamber 34 is returned to the fuel tank 48 via the fuel relief passage 50. On the other hand, when the control valve 52 closes, the fuel in the pressurizing chamber 34 is compressed, and as a result, when the fuel pressure in the pressurizing chamber 34 becomes higher than the fuel pressure in the fuel discharge passage 30, the check valve 36 opens. Then, the pressurized chamber 34
The fuel inside the common rail 29 passes through the fuel discharge passage 30.
As a result, the fuel pressure P within the common rail 29 is immediately raised. Therefore, by controlling the valve closing period RCP of the control valve 52 during the upward stroke of the plunger 41, the amount of fuel Qp discharged from the fuel injection pump 32 into the fuel discharge passage 30 is controlled. The fuel pressure P can be controlled with good responsiveness. That is, Figure 1
In the embodiment shown in FIG. 2, the valve closing period RCP of the control valve 52 is adjusted to the fuel pressure P so that the fuel pressure P in the common rail 29 detected by the pressure sensor 55 becomes a predetermined target fuel pressure. Feedback control is performed to compensate for these ΔP and Qi based on the differential pressure ΔP with respect to the target fuel pressure and the calculated fuel injection amount Qi to be injected next from the high-pressure fuel injection valve 25 or the low-pressure fuel injection valve 26. . As shown in FIG. 2, the closing end timing RO of the control valve 52 is fixed to the timing when the plunger 41 is located at the top dead center, while the closing start timing RC of the control valve 52 is fixed to the timing when the plunger 41 is located at the top dead center. It can be changed according to.

During normal engine operation after engine startup, the fuel pressure P in the common rail 29 detected by the pressure sensor 55 is set to a predetermined high target fuel pressure Ph, for example.
The valve closing period RCP of the control valve 52 is feedback-controlled so as to maintain a predetermined constant pressure of about 10 MPa to 20 MPa. Further, during normal engine operation, the low pressure fuel injection valve 26 is not operated, and only fuel is injected from the high pressure fuel injection valve 25 into the combustion chamber 5. In the embodiment shown in FIG. 1, during high-load engine operation, fuel is injected from the high-pressure fuel injection valve 25 toward the entire top surface of the piston 2 before and after the exhaust valve 8 closes, that is, when the piston 2 is in a low position. As a result, a uniform air-fuel mixture is formed throughout the combustion chamber 5. On the other hand, during low-load engine operation, the piston 2
piston 2 from the high pressure fuel injection valve 25 when the position of
Fuel is injected into the groove 77 formed on the top surface, and the injected fuel is guided below the ignition plug 10 along the inner wall surface of the groove 77 to collect the air-fuel mixture around the ignition plug 10. In this way, the inside of the combustion chamber 5 is stratified. In this way, the fuel pressure P in the common rail 29 is adjusted to the engine compression so that fuel can be injected from the high-pressure fuel injection valve 25 into the combustion chamber 5 even when the position of the piston 2 is high, that is, when the in-cylinder pressure is high. The target fuel pressure Ph is maintained at the above-mentioned high pressure that is higher than the cylinder pressure at the end of the stroke. Further, by injecting fuel at high pressure from the high-pressure fuel injection valve 25 in this manner, the injection speed of the fuel is increased, and as a result, a high fuel injection rate is ensured and atomization of the injected fuel is promoted.

On the other hand, when starting the engine, the fuel pressure P in the common rail 29 detected by the pressure sensor 55 is set to a predetermined low target fuel pressure Pl, for example 0.5 MPa.
The valve closing period RCP of the control valve 52 is feedback-controlled so that the pressure is maintained at a predetermined constant pressure of about 1 MPa. Also, when starting this engine, the high pressure fuel injection valve 2
5 is not activated, and the air supply branch pipe 14 is connected from the low pressure fuel injection valve 26.
Only the fuel is injected into the collecting part. In this way, when the engine is started, the valve closing period RCP of the control valve 52 is controlled so that the fuel pressure P in the common rail 29 becomes the low target fuel pressure Pl, and as a result, during the upward stroke of the plunger 41, the fuel injection pump 32 Fuel relief passage 50
The amount of fuel returned into the fuel tank 48 via the fuel tank 48 is increased. In this way, the driving torque of the fuel injection pump 32 is significantly reduced when starting the engine. As a result, when the engine is cranked and rotated by a starter motor (not shown) when the engine is started, the cranking rotational speed is quickly increased. Moreover, in this way, the fuel pressure P in the common rail 29 is lower than the target fuel pressure Pl.
When starting the engine, which is controlled by the engine, fuel is injected into the air supply branch pipe 14 from the low pressure fuel injection valve 26 as described above. When the engine is started, the engine temperature is generally low, so the atomization of the injected fuel is poor, but by injecting the fuel into the air supply branch pipe 14 in this way, the injected fuel is sufficiently premixed with the air, resulting in good mixing. Qi is formed. Note that since a mask wall 11 is formed on the inner wall surface of the cylinder head 4, even if the air-fuel mixture is supplied from the air supply port 7, this air-fuel mixture will not flow through the exhaust port 9.
There is no way to blow inside. In this way, when the engine is started, the engine cranking speed is quickly raised as described above, and the injected fuel is sufficiently premixed with the air to form a good air-fuel mixture, so that combustion in the engine starts quickly. and ensure good combustion. Thus, once engine combustion begins, the engine speed N rapidly increases. In this way, since the engine cranking rotational speed increases quickly and engine combustion starts quickly, good engine startability can be ensured.

[0015] When combustion of the engine is started and the engine speed N becomes higher than a predetermined engine start judgment speed N1, for example, 600 rpm, the common rail 29
The target fuel pressure within is switched from a low target fuel pressure Pl to a high target fuel pressure Ph. That is, common rail 2
The valve closing period RCP of the control valve 52 is feedback-controlled so that the fuel pressure P in the control valve 9 becomes a high target fuel pressure Ph. At this time, fuel injection from the low-pressure fuel injection valve 26 is stopped, and fuel injection from the high-pressure fuel injection valve 25 is started, thus shifting the engine to normal operation. Note that if the engine speed N rises to the engine start determination speed N1, the number of fuel discharges per unit time of the fuel injection pump 32 has increased sufficiently, so the common rail 29
The internal fuel pressure P can be quickly and easily increased from the low target fuel pressure Pl to the high target fuel pressure Ph. Also, the target fuel pressure in the common rail 29 is set to low pressure Pl.
Instead of immediately switching from fuel injection from the low pressure fuel injection valve 26 to fuel injection from the high pressure fuel injection valve 25 when the target fuel pressure is switched from low pressure Pl to high pressure Ph, the fuel injection pump 32 is a predetermined number of discharges NHO, for example, after the fuel has been discharged once, that is, after the fuel pressure P in the common rail 29 has been reliably increased to the high target fuel pressure Ph, the fuel is discharged from the high pressure fuel injection valve 25. Alternatively, the injection may be started. Further, in this embodiment, the engine starting determination rotation speed N1 when the target fuel pressure in the common rail 29 is switched from the low pressure Pl to the high pressure Ph is, for example, 600r as described above.
pm, while the target fuel pressure is set to high pressure Ph.
If the engine speed N drops for some reason after switching to the low pressure Pl, the engine start determination speed N2 for returning the target fuel pressure to the low pressure Pl is set to, for example, 300 rpm. In this way, engine starting judgment rotation speed N1, N2
By providing hysteresis in the engine, hunting is prevented and the fuel pressure P in the common rail 29 smoothly transitions from the low target fuel pressure Pl to the high target fuel pressure Ph, that is, from engine starting operation to engine normal operation. We are working to ensure a smooth transition.

In FIG. 1, the high-pressure fuel injection valve 25 and the low-pressure fuel injection valve 26 are each electromagnetically controlled to open and close by solenoids (not shown). By the way, when the engine is started, the engine temperature is generally low, so the voltage of the battery (not shown) is low. Furthermore, since the starter motor is driven for cranking operation when starting the engine, the battery voltage also decreases. In the embodiment shown in FIG. 1, only the low pressure fuel injection valve 26 is operated and the high pressure fuel injection valve 25 is not operated when the engine is started when the battery voltage is low. Therefore, no consideration is required to enable the high-pressure fuel injection valve 25 to be driven when the battery voltage is low, and as a result, the drive mechanism and drive circuit for the high-pressure fuel injection valve 25 can be significantly simplified. On the other hand, the low-pressure fuel injection valve 26 is operated only when the engine is started, and therefore the low-pressure fuel injection valve 26 only needs to be opened against the low fuel pressure Pl, so that it can be driven satisfactorily even at a low voltage. Further, since it is not necessary to measure the fuel injection amount with high precision when starting the engine, the drive circuit for the low-pressure fuel injection valve 26 can be simplified.

Next, with reference to FIGS. 3 to 7, control of the fuel pressure P in the common rail 29 and fuel injection control in the embodiment shown in FIGS. 1 and 2 will be described.

First, when the ignition switch 57 is turned on to start engine operation, the initial value setting process shown in FIG. 4 is executed. Referring to FIG. 4, first, in step 110, the value of flag SF is reset to zero. Next, in step 111, the counter NS
The value of is cleared to 0. Next, in step 112, the value of the counter NH is cleared to zero. Next, in step 113, the value of the starting rotation speed determination flag HNF is reset to zero. Next, in step 114, the value of the fuel pressure flag HIF is reset to zero.

Next, the main routine will be explained with reference to FIG. Referring to Figure 3, first step 10
0, the engine load Q/N is calculated based on the intake air amount Q found from the output signal of the air flow meter 19 and the engine rotation speed N found from the output signal of the crank angle sensor 58.

Next, in step 101, it is determined whether the value of the fuel pressure flag HIF is 0 or not. Note that this fuel pressure flag HIF is shown in FIGS. 6 to 7 as described later.
The value 0 or the value 1 is set in subroutine A shown in FIG. If the fuel pressure flag HIF is 0, it means that fuel should be injected from the low-pressure fuel injection valve 26, that is, when the engine is started, and in this case, the process advances to step 102. Step 1
02, the fuel injection time TAUb from the low pressure fuel injection valve 26 when the fuel pressure P in the common rail 29 is the low target fuel pressure Pl is calculated. This fuel injection time TAUb is determined by, for example, the engine load Q/N and the engine speed N.
The fuel injection time TAUb is calculated based on the fuel injection time TAUb data stored in advance in the ROM 62 in the form of a map related to the fuel injection time TAUb. Next, in step 103, the ROM 62
The fuel injection start time and fuel injection completion time are calculated from the data stored in the controller. Then step 104
Then, data for starting the injection at the fuel injection start time and data for completing the injection at the fuel injection completion time are output from the low pressure fuel injection valve 26 to the output port 67, and based on these data, the data for starting the injection at the fuel injection start time and the data for completing the injection at the fuel injection completion time are output. Fuel injection takes place.

On the other hand, if the fuel pressure flag HIF is not 0 in step 101, it means that fuel should be injected from the high-pressure fuel injection valve 25, that is, the engine is in normal operation after the engine has been started, and in this case, the process proceeds to step 105. move on. In step 105, the fuel pressure P in the common rail 29 is
The fuel injection time TAUa from the high pressure fuel injection valve 25 when is the high target fuel pressure Ph is calculated. This fuel injection time TAUa is calculated based on fuel injection time TAUa data stored in advance in the ROM 62 in the form of a map regarding engine load Q/N and engine speed N, for example. Next, in step 106, R
The fuel injection start timing and fuel injection completion timing are calculated from the data stored in the OM 62. Next, in step 107, data for starting the injection at the fuel injection start time and data for completing the injection at the fuel injection completion time are output from the high-pressure fuel injection valve 25 to the output port 67.
Fuel injection from the high pressure fuel injection valve 25 is performed based on these data.

In the interrupt routine shown in FIG. 5, when the plunger 41 of the fuel injection pump 32
This is executed by an interrupt caused by an output pulse output from the crank angle sensor 58 at the engine crank angle corresponding to the engine position. In the embodiment shown in FIG. 1, the plunger 41 makes one reciprocation for one reciprocation of the piston 2, so the interrupt routine shown in FIG. 5 is executed once per engine cycle. Referring to FIG. 5, step 12
At 0, subroutine A is called.

Next, subroutine A will be explained with reference to FIGS. 6 and 7. Referring to FIGS. 6 and 7, first, in step 130, the value of the flag SF is set to 1.
It is determined whether or not. If the flag SF is not 1, the process proceeds to step 131, where the valve closing start timing RC (see FIG. 2) of the control valve 52 is set to a predetermined initial value RCc. Initial value RCc of the valve closing start timing of this control valve 52
The fuel injection pump 3 is activated by the reciprocating movement of the plunger 41.
The valve closing start timing is set at which the amount of fuel discharged from 2 into the fuel discharge passage 30 is at a maximum, for example, at the timing when the plunger 41 is located at the bottom dead center. On the other hand, the closing end timing RO of the control valve 52 is fixed at the timing when the plunger 41 is located at the top dead center, as shown in FIG. Next, in step 132, the actuator 53 of the control valve 52 is driven so that the control valve 52 starts closing at the valve-closing start time RC and finishes closing at the valve-closing end time RO. Next, in step 133, the fuel pressure flag HIF is set to the value 0. Next, in step 134, the value of the counter NH is cleared to zero. Next, in step 135, the value of the counter NS is incremented by one. Next, in step 136, it is determined whether the value of the counter NS is equal to or greater than a predetermined number of ejections NS0, for example, two times. If the value of the counter NS is greater than or equal to the predetermined number of discharges NS0, step 13
7, the value 1 is set in the flag SF, and this subroutine A ends. On the other hand, if the value of the counter NS is less than the predetermined number of ejections NS0, this subroutine A is directly terminated.

That is, from step 131 to step 13
7 is a process in which the fuel injection pump 32 discharges a predetermined number of times N after the ignition switch 57 is turned on.
This is executed during a period until fuel is discharged S0 times, and during this period, the control valve 52 is kept closed throughout the entire upward stroke of the plunger 41. Therefore, the fuel in the pressurizing chamber 34 of the fuel injection pump 32 is removed from the fuel relief passage 5.
0 into the fuel discharge passage 30 without being returned into the fuel tank 48. As a result, the fuel pressure P in the common rail 29 can be quickly raised toward a predetermined low target fuel pressure Pl, for example 1 MPa.

On the other hand, in step 130, the flag S
If F is 1, that is, if the fuel injection pump 32 has discharged fuel a predetermined number of times NS0 or more since the ignition switch 57 was turned on, the process proceeds to step 138. In step 138, it is determined whether the value of the starting rotation speed determination flag HNF is 0 or not. If the value of the starting rotation speed determination flag HNF is 0, the process proceeds to step 139, where it is determined whether the engine rotation speed N is equal to or higher than a predetermined engine start determination rotation speed N1, for example, 600 rpm. Engine speed N is 600r
If it is greater than or equal to pm, the process proceeds to step 140, where the starting rotation speed determination flag HNF is set to the value 1, and then the process proceeds to step 143. On the other hand, the engine speed N is 600
If the rpm is below, the process directly proceeds to step 143.

On the other hand, if the value of the starting rotation speed determination flag HNF is not 0 in step 138, the process proceeds to step 141, where it is determined whether the engine rotation speed N is less than or equal to a predetermined engine start determination rotation speed N2, for example 300 rpm. It is determined whether or not. If the engine speed N is less than 300 rpm, the process proceeds to step 142, where the starting rotation speed determination flag HNF is set to the value 0, and then the process proceeds to step 143. On the other hand, if the engine speed N is 300 rpm or more, the process directly proceeds to step 143. As shown in steps 138 to 142, the value of the starting rotation speed determination flag HNF is changed over with hysteresis between 600 rpm and 300 rpm.

In step 143, it is determined whether the value of the starting rotation speed determination flag HNF is 0 or not. When the value of the starting rotation speed judgment flag HNF is 0, that is, when the engine rotation speed N is lower than the engine starting judgment rotation speed, that is, when the engine is starting, the fuel pressure P in the common rail 29 is
to a predetermined low target fuel pressure Pl, for example 1M
In order to perform feedback control on Pa, the process proceeds to step 144 and subsequent steps.

At step 144, a pressure difference ΔP is calculated from the fuel pressure P in the common rail 29 detected by the pressure sensor 55 and the predetermined low target fuel pressure Pl mentioned above based on the following equation. ΔP=P−Pl

(1) Next, in step 145, the correction coefficient Kp is calculated based on the data of the correction coefficient Kp stored in advance in the ROM 62 in the form of a map regarding the fuel pressure P in the common rail 29 and the engine speed N. Next, in step 146, the amount of discharged fuel Qp to be discharged from the fuel injection pump 32 into the fuel discharge passage 30 is calculated based on the following equation. Qp = K・Qi +Kp・ΔP
…(
2) Here, Qi is the fuel injection time T at step 102 or step 105 of the main routine shown in FIG.
This is the latest value of the fuel injection amount from the low-pressure fuel injection valve 26 or the high-pressure fuel injection valve 25 found when calculating AUb or TAUa, and K is a correction coefficient.

Next, in step 147, the closing period RCP of the control valve 52 is calculated from the amount of discharged fuel Qp to be discharged from the fuel injection pump 32. Next, in step 148, the valve closing start timing RC of the control valve 52 is calculated from the valve closing period RCP of the control valve 52. In addition, the control valve 5
The valve closing end timing RO of No. 2 is fixed at the timing when the plunger 41 is located at the top dead center, as shown in FIG. Next, in step 149, the control valve 52 determines the valve closing start timing RC.
The actuator 53 of the control valve 52 is driven so as to start closing the valve at the closing time RO and finish closing the valve at the closing end time RO. Next, in step 150, the fuel pressure flag H
The value 0 is set to IF. Then step 151
Then, the value of the counter NH is cleared to 0, and this subroutine A ends.

On the other hand, if the value of the starting rotation speed judgment flag HNF is not 0 in step 143, that is, if the engine rotation speed N is higher than the engine starting judgment rotation speed, that is, if the engine is in normal operation after starting, the common rail In step 1, the fuel pressure P in the fuel tank 29 is feedback-controlled to a predetermined high target fuel pressure Ph, for example, 10 MPa.
52 Proceed to the following processing.

In step 152, a pressure difference ΔP is calculated from the fuel pressure P in the common rail 29 detected by the pressure sensor 55 and the above-mentioned predetermined high target fuel pressure Ph based on the following equation. ΔP=P−Ph

(3) Next, in step 153, a correction coefficient Kp is calculated in the same manner as in step 145 described above. Next, in step 154, the amount of discharged fuel Qp to be discharged from the fuel injection pump 32 into the fuel discharge passage 30 is determined.
is calculated based on the following formula. Qp = K・Qi +Kp・ΔP
…(
4) Here, Qi is the fuel injection time T at step 105 or step 102 of the main routine shown in FIG.
This is the latest value of the fuel injection amount from the high-pressure fuel injection valve 25 or the low-pressure fuel injection valve 26 found when calculating AUa or TAUb, and K is a correction coefficient.

Next, in step 155, the closing period RCP of the control valve 52 is calculated from the amount of discharged fuel Qp to be discharged from the fuel injection pump 32. Next, in step 156, the valve closing start timing RC of the control valve 52 is calculated from the valve closing period RCP of the control valve 52. In addition, the control valve 5
The valve closing end timing RO of No. 2 is fixed at the timing when the plunger 41 is located at the top dead center, as shown in FIG. Next, in step 157, the control valve 52 determines the valve closing start timing RC.
The actuator 53 of the control valve 52 is driven so as to start closing the valve at the closing time RO and finish closing the valve at the closing end time RO.

Next, in step 158, it is determined whether the value of the fuel pressure flag HIF is 0 or not. If the value of the fuel pressure flag HIF is not 0, this subroutine A is immediately terminated. On the other hand, if the value of the fuel pressure flag HIF is 0, the process proceeds to step 159 and the value of the counter NH is incremented by 1. Next, in step 160, the value of the counter NH becomes a predetermined number of discharges NH0,
For example, it is determined whether or not it is greater than once. If the value of the counter NH is larger than the predetermined number of discharges NH0, the process proceeds to step 161 and the fuel pressure flag is set to HI.
The value 1 is set in F, and this subroutine A ends. On the other hand, the value of the counter NH is the predetermined number of discharges N.
If it is less than H0, this subroutine A is directly terminated. That is, after the target fuel pressure in the common rail 29 is switched from the low pressure Pl to the high pressure Ph, the value of the fuel pressure flag HIF is switched to 1 after the fuel injection pump 32 has discharged fuel a predetermined number of discharges NH0. Note that the number of times of ejection NH0 can also be set to 0 times.

Next, a second embodiment will be described with reference to FIGS. 8, 2, 9, and 4 to 7. Comparing the embodiment shown in FIG. 8 with the first embodiment shown in FIG. 1, the embodiment shown in FIG. 8 does not include a low-pressure fuel injection valve 26 for starting at the gathering portion of the air supply branch pipe 14. The other configurations are similar to the embodiment shown in FIG. Note that the same reference numerals are used for similar components.

Control of the fuel pressure P in the common rail 29 and fuel injection control from the high pressure fuel injection valve 25 during normal engine operation after engine startup are the same as in the first embodiment. That is, the control valve 52 is adjusted so that the fuel pressure P in the common rail 29 detected by the pressure sensor 55 becomes a predetermined high target fuel pressure Ph, for example, 10 MPa.
The valve closing period RCP is feedback-controlled, and high-pressure fuel is injected from the high-pressure fuel injection valve 25 into the fuel chamber 5.

On the other hand, when starting the engine, the valve closing period RCP of the control valve 52 is fed back so that the fuel pressure P in the common rail 29 detected by the pressure sensor 55 becomes a predetermined low target fuel pressure Pl, for example 1 MPa. When the piston 2 is in a low position, low-pressure fuel is injected from the high-pressure fuel injection valve 25 into the combustion chamber 5. In this way, when the engine is started, the fuel pressure P in the common rail 29 is changed to the low target fuel pressure Pl as in the case of the first embodiment.
Since the valve closing period RCP of the control valve 52 is controlled so that
The amount of fuel returned into the 8 is increased. In this way, the driving torque of the fuel injection pump 32 is significantly reduced when starting the engine. As a result, the engine cranking rotational speed is quickly increased, so that combustion in the engine is promptly started, and thus good engine startability can be obtained. Next, combustion of the engine is started in this way, and the engine rotation speed N reaches a predetermined engine start determination rotation speed N1.
, for example, when the target fuel pressure in the common rail 29 becomes higher than 600 rpm, the target fuel pressure in the common rail 29 is switched from the low target fuel pressure Pl to the high target fuel pressure Ph. Next, after fuel is discharged from the fuel injection pump 32 a predetermined number of times NH0, for example, once, fuel injection during normal operation of the engine begins.

In FIG. 8, the high-pressure fuel injection valve 25 is electromagnetically controlled to open and close by a solenoid (not shown). When this solenoid is deenergized during normal operation after starting the engine, the valve body of the high pressure fuel injection valve 25 maintains the high fuel pressure Ph.
The valve is closed by the pressing force of a compression spring (not shown). Note that this compression spring presses the valve body with a considerably large force in order to completely close the valve body. Therefore, when the high pressure fuel injection valve 25 is opened, the high fuel pressure Ph
In order to open the valve body against the large pressing force of the compression spring, the solenoid is formed with a large number of turns and allows a large current to flow when energized. However, when the engine is started, the voltage of the battery (not shown) is generally low because the engine temperature is low. Furthermore, since the starter motor is driven when starting the engine, the battery voltage further decreases. the result,
When the engine starts, the suction force with which the solenoid suctions the valve element becomes weaker. Therefore, if the fuel pressure is high, even if an attempt is made to open the high-pressure fuel injection valve 25, the nozzle port of the high-pressure fuel injection valve 25 will not open completely, resulting in a problem that the fuel injection amount cannot be controlled with precision. Put it away. On the other hand, in this embodiment, as described above, the common rail 29
Since the internal fuel pressure P is controlled to the low target fuel pressure Pl, the nozzle opening of the high-pressure fuel injection valve 25 is completely and reliably opened when the solenoid is energized even when the battery voltage is low. Therefore, the fuel injection amount can be controlled with high precision. Further, in the second embodiment, there is no need to provide a low-pressure fuel injection valve for starting separately from the high-pressure fuel injection valve 25, so there is an advantage that costs can be reduced compared to the first embodiment.

Next, with reference to the main routine shown in FIG. 9, the initial value setting processing routine shown in FIG. 4, the crank angle interrupt routine shown in FIG. 5, and the subroutine A shown in FIGS. The fuel injection control etc. in this embodiment will be explained. Note that each routine shown in FIGS. 4 to 7 is the same as in the first embodiment.

Referring to the main routine shown in FIG.
First, in step 170, the engine load Q/N is calculated based on the intake air amount Q determined from the output signal of the air flow meter 19 and the engine rotational speed N determined from the output signal of the crank angle sensor 58.

Next, in step 171, it is determined whether the value of the fuel pressure flag HIF is 0 or not. If the value of the fuel pressure flag HIF is 0, this means that the engine is starting, and in this case, the process proceeds to step 172. Step 17
2 shows the high pressure fuel injection valve 25 when the fuel pressure P in the common rail 29 is controlled to a low target fuel pressure Pl.
The fuel injection time TAUl from is calculated. This fuel injection time TAUl is calculated based on fuel injection time TAUl data stored in advance in the ROM 62 in the form of a map regarding engine load Q/N and engine speed N, for example. Next, in step 173, R
Fuel injection start time and fuel injection completion time are calculated from data stored in OM 62. Next, in step 174, data for starting the injection at the fuel injection start time and data for completing the injection at the fuel injection completion time are output from the high-pressure fuel injection valve 25 to the output port 67, and based on these data, the high-pressure fuel injection valve Low pressure fuel injection from 25 is performed.

On the other hand, if the fuel pressure flag HIF is not 0 in step 171, this means that the engine is in normal operation after completion of engine starting, and in this case, the process proceeds to step 175. In step 175, the fuel injection time TAUh from the high pressure fuel injection valve 25 when the fuel pressure P in the common rail 29 is controlled to the high target fuel pressure Ph is calculated. This fuel injection time TAUh is stored in the ROM in advance in the form of a map regarding engine load Q/N and engine speed N, for example.
It is calculated based on the fuel injection time TAUh data stored in 62. Then step 176
Then, the fuel injection start timing and fuel injection completion timing are calculated from data stored in the ROM 62 in advance. Next, in step 177, data for starting the injection at the fuel injection start time and data for completing the injection at the fuel injection completion time are sent to the output port 67 from the high-pressure fuel injection valve 25.
Based on these data, the high pressure fuel injection valve 2
High-pressure fuel injection from 5 is performed.

Note that step 172 and step 1
75, the fuel injection time TAUl as described above.
Instead of finding the fuel injection times TAUl and TAUh from the map of and the map of TAUh, respectively,
Based on the fuel pressure P in the common rail 29 detected by the pressure sensor 55, the fuel injection time T is determined as follows.
AUl and TAUh can also be determined. That is, a map of the fuel injection time TAUh when the fuel pressure P in the common rail 29 is the high target fuel pressure Ph is stored in the ROM 62 in advance. Step 172
In step 175, the fuel injection time TAU is calculated based on the map of TAUh and the actual fuel pressure P in the common rail 29 detected by the pressure sensor 55 based on the following equation.

[Math 1]

Next, a third embodiment will be described with reference to FIGS. 10 to 13 and FIG. 9. In the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. By controlling the valve closing period RCP of the valve 52, the amount of fuel discharged from the fuel injection pump 32 into the fuel discharge passage 30 is controlled. On the other hand, in the third embodiment shown in FIG. 10, a general fuel injection pump 80 whose fuel discharge amount cannot be controlled is used to control the fuel pressure P in the common rail 29 in the same way as in the second embodiment. That's what I do.

Referring to FIG. 10, a fuel relief passage 82 branches off from the common rail 29. This fuel relief passage 8
2 is connected to the first fuel relief passage 85 and the second fuel relief passage through the switching valve 84.
It branches into a fuel relief passage 86. The first fuel relief passage 85 is connected to the fuel tank 48 , and a high pressure relief valve 87 is disposed within the first fuel relief passage 85 . on the other hand,
The second fuel relief passage 86 is the first fuel relief passage downstream of the high pressure relief valve 87.
This second fuel relief passage 8 is connected to a fuel relief passage 85 .
A low pressure relief valve 88 is disposed within 6. The output port 67 of the electronic control unit 60 is connected to the switching valve 84 via the drive circuit 90, and the switching valve 84 is connected to the electronic control unit 6.
Switching is controlled by an output signal of 0.

When the fuel relief passage 82 is connected to the first fuel relief passage 85 by the switching action of the switching valve 84, the common rail 29 is connected to the fuel tank 48 via the high pressure relief valve 87. In this case, the fuel pressure P in the common rail 29 is a predetermined constant high pressure Ph, for example 1
When the pressure exceeds 0 MPa, the high pressure relief valve 87 opens, and the fuel in the common rail 29 is returned to the fuel tank 48 via the fuel relief passage 82 and the first fuel relief passage 85. On the other hand, when the fuel pressure P in the common rail 29 falls below the above-mentioned predetermined constant high pressure Ph, the high pressure relief valve 87 closes. Therefore, the high pressure relief valve 87
serves to maintain the fuel pressure P in the common rail 29 at a predetermined constant high pressure Ph. On the other hand, the switching valve 8
When the fuel relief passage 82 is connected to the second fuel relief passage 86 by the switching action of No. 4, the common rail 29 is connected to the fuel tank 48 via the low pressure relief valve 88. In this case, when the fuel pressure P in the common rail 29 exceeds a predetermined constant low pressure Pl, for example 1 MPa, the low pressure relief valve 88 opens, and the fuel in the common rail 29 is released into the fuel relief passage 82 and the second fuel relief passage. 86 and returned into the fuel tank 48. Therefore, the low pressure relief valve 88 serves to maintain the fuel pressure P in the common rail 29 at a predetermined constant low pressure Pl. Figure 10
As can be seen, the switching valve 84, high pressure relief valve 87, and low pressure relief valve 88 are control valves 8 that control the amount of fuel discharged from the common rail 29 via the fuel relief passage 82.
9. Note that in the example shown in FIG.
Unlike the embodiments shown in FIGS. 1 and 8, the pressure sensor 55 is not installed within the common rail 29.

Next, control of the fuel pressure P in the common rail 29 at the time of starting the engine and during normal operation of the engine after starting the engine will be explained. During normal engine operation after engine startup, the common rail 29 is connected to the fuel tank 48 via the fuel relief passage 82, the high pressure relief valve 87, and the first fuel relief passage 85 by the switching action of the switching valve 84. Therefore, the fuel pressure P in the common rail 29 is maintained at a predetermined constant high pressure Ph as described above, and high-pressure fuel is injected from the high-pressure fuel injection valve 25 into the combustion chamber 5.

On the other hand, when the engine is started, the common rail 29 is connected to the fuel tank 48 via the fuel relief passage 82, the low pressure relief valve 88, and the second fuel relief passage 86 by the switching action of the switching valve 84. As a result, the fuel relief passage 8
2, the amount of fuel discharged from the common rail 29 is increased, thus increasing the fuel pressure P in the common rail 29.
is maintained at a predetermined constant low pressure Pl as described above. At this time, low-pressure fuel is injected from the high-pressure fuel injection valve 25 into the combustion chamber 5 when the piston 2 is in a low position. In this way, when the engine starts, the fuel pressure P in the common rail 29
is maintained at a predetermined constant low pressure Pl, so the driving torque of the fuel injection pump 80 is significantly reduced. As a result, the engine cranking rotational speed is quickly increased, and combustion of the engine is promptly started, thus ensuring good engine startability. Next, when combustion of the engine is started and the engine speed N becomes higher than a predetermined engine start judgment speed N1, for example 600 rpm, the fuel relief passage 82 is switched to the high pressure relief valve by the switching action of the switching valve 84. 87, thus increasing the fuel pressure P within the common rail 29. Next, a predetermined number of discharges NH from the fuel injection pump 80 is performed.
After the fuel is discharged 0 times, for example once, the fuel injection during normal engine operation begins. Note that when this discharge number NH0 is set to 0 times and the switching valve 84 is switched so that the fuel relief passage 82 is connected to the high pressure relief valve 87, the fuel injection during normal engine operation is immediately started. You can do it like this.

Next, the flow of controlling the fuel pressure P in the common rail 29 in the third embodiment will be explained with reference to FIGS. 11 to 13 and FIG. 9. Note that the main routine shown in FIG. 9 is the same as in the second embodiment.

When the ignition switch 57 is turned on when starting engine operation, the initial value setting process shown in FIG. 11 is executed. Referring to FIG. 11, first, in step 180, the value of the counter NH is cleared to zero. Next, in step 181, the starting rotation speed determination flag HN
The value of F is reset to 0. Then step 182
Then, the value of the fuel pressure flag HIF is reset to zero.

The crank angle interrupt routine shown in FIG. 12 is executed once per cycle of the fuel injection pump 80. In the embodiment shown in FIG.
Since the plunger 41 makes one reciprocating motion in response to the reciprocating motion, the interrupt routine shown in FIG. executed. Referring to FIG. 12, subroutine B is called at step 190.

Next, subroutine B will be explained with reference to FIG. Referring to FIG. 13, first, in step 200, it is determined whether the value of the starting rotation speed determination flag HNF is 0 or not. Starting rotation speed judgment flag H
If the value of NF is 0, the process proceeds to step 201, where it is determined whether the engine rotation speed N is equal to or higher than a predetermined engine start determination rotation speed N1, for example, 600 rpm. If the engine speed N is 600 rpm or more, the process proceeds to step 202 and the starting speed determination flag HNF is set.
is set to the value 1, and then the process proceeds to step 205. On the other hand, if the engine speed N is 600 rpm or less, the process directly proceeds to step 205.

On the other hand, if the value of the starting rotation speed determination flag HNF is not 0 in step 200, the process proceeds to step 203, where it is determined whether the engine rotation speed N is less than or equal to a predetermined engine start determination rotation speed N2, for example 300 rpm. It is determined whether or not. If the engine speed N is less than 300 rpm, the process proceeds to step 204, where the starting rotation speed determination flag HNF is set to the value 0, and then the process proceeds to step 205. On the other hand, if the engine speed N is 300 rpm or more, the process directly proceeds to step 205.

In step 205, it is determined whether the value of the starting rotation speed determination flag HNF is 0 or not. If the value of the starting rotation speed determination flag HNF is 0, the process proceeds to step 206, where the switching valve 84 is controlled to connect the fuel relief passage 82 to the low pressure relief valve 88. Next, in step 207, the fuel pressure flag HIF is set to the value 0, and then in step 208, the value of the counter NH is cleared to 0, and this subroutine B ends.

On the other hand, if the value of the starting rotation speed determination flag HNF is not 0 in step 205, the process proceeds to step 209, where the switching valve 84 is controlled to connect the fuel relief passage 82 to the high pressure relief valve 87. . Next, in step 210, it is determined whether the value of the fuel pressure flag HIF is 0 or not. If the value of the fuel pressure flag HIF is not 0, this subroutine B is immediately terminated. On the other hand, the fuel pressure flag HI
If the value of F is 0, the process advances to step 211 and the value of the counter NH is incremented by 1. Then step 21
2, the value of the counter NH is set to the predetermined number of discharges N.
It is determined whether H0 is greater than, for example, once. If the value of the counter NH is larger than the predetermined number of discharges NH0, the process proceeds to step 213, where the fuel pressure flag HIF is set to the value 1, and this subroutine B is ended. On the other hand, if the value of the counter NH is less than or equal to the predetermined number of ejections NH0, this subroutine B is immediately terminated.

Note that also for the first embodiment shown in FIG. 1, a fuel injection pump 80 is used instead of the fuel injection pump 32 as shown in FIG. By branching the fuel relief passage and arranging the switching valve 84, high pressure relief valve 87, and low pressure relief valve 88 in the fuel relief passage, the same operation and effect as in the first embodiment can be obtained. Needless to say.

Next, FIGS. 8, 9, and 14 to 1
A fourth embodiment will be described with reference to 6. As shown in FIG. 8, the configuration of this fourth embodiment is the same as that of the second embodiment. In the second embodiment, when the engine is started, the control valve 52 is set so that the fuel pressure P in the common rail 29 becomes a predetermined low target fuel pressure Pl, for example, 1 MPa.
The valve closing period RCP is feedback-controlled, and then the engine speed N is set to a predetermined engine start judgment speed N1.
When the fuel pressure P in the common rail 29 becomes higher than the predetermined high target fuel pressure Ph, for example, 10M
The valve-closing period RCP of the control valve 52 is feedback-controlled so as to be equal to Pa. In this fourth embodiment as well, the fuel pressure P in the common rail 29 is controlled as in the second embodiment when the engine is started at normal temperature.

On the other hand, when starting an engine at a cryogenic temperature, for example when starting an engine when the engine cooling water temperature TW is below 0°C, the viscosity of the lubricating oil increases, so the frictional resistance of each part of the engine increases, and as a result, the engine cranking speed decreases. becomes particularly difficult to rise. In order to solve this problem, in the fourth embodiment, when starting the engine at a cryogenic temperature, a predetermined period of time C0 is set from the start of cranking.
, for example, during a period SP0 until 3 seconds have elapsed, the control valve 52 is controlled to open and close so that the valve closing period RCP (see FIG. 2) of the control valve 52 becomes a predetermined valve closing period RCP0, for example, zero. . That is, the control valve 52 is kept open at all times. As a result, during the upward stroke of the plunger 41, the fuel in the pressurizing chamber 34 is returned to the fuel tank 48 via the fuel relief passage 50 without being pushed into the fuel discharge passage 30. Since the driving torque of the fuel injection pump 32 is thus significantly reduced, the engine cranking speed can be quickly increased even when the engine is started at a cryogenic temperature. Note that the period S from the start of cranking until a predetermined period of time C0 has elapsed
At P0, the fuel pressure P in the common rail 29 is at an extremely low pressure below the discharge pressure Pf of the fuel supply pump 49, so it is not a question whether or not fuel is injected from the high-pressure fuel injection valve 25 into the combustion chamber 5. do not have.

Next, when a predetermined period of time C0 has elapsed from the start of cranking, the control valve 52 is closed so that the fuel pressure P in the common rail 29 reaches a predetermined low target fuel pressure Pl, for example 1 MPa. Period RCP
is feedback-controlled, and low-pressure fuel is injected from the high-pressure fuel injection valve 25 into the combustion chamber 5. Since the engine cranking rotational speed is rapidly increased during the above-mentioned period SP0, combustion of the engine is promptly started, and thus good engine startability can be obtained even when the engine is at an extremely low temperature. Next, when combustion of the engine is started and the engine speed N becomes higher than a predetermined engine start judgment speed N1, for example 600 rpm, the target fuel pressure in the common rail 29 changes from the low target fuel pressure Pl. The target fuel pressure Ph is switched to the high target fuel pressure Ph, that is, the fuel pressure P in the common rail 29 is switched to the high target fuel pressure Ph.
The valve closing period RCP of the control valve 52 is feedback-controlled so that the pressure is, for example, 10 MPa. After the fuel injection pump 32 has discharged fuel a predetermined number of times NH0, for example, once from the time of switching the target fuel pressure,
Shifts to fuel injection during normal engine operation. In addition,
If engine combustion starts and the engine speed N exceeds the engine start determination speed N1 before a predetermined period of time C0 has elapsed since the start of cranking, the target fuel in the common rail 29 at that point The pressure is set to a high target fuel pressure Ph, and feedback control of the valve closing period RCP of the control valve 52 is started.

Next, the flow of the opening/closing control of the control valve 52 in the fourth embodiment will be explained with reference to FIGS. 9 and 14 to 16. Note that the main routine shown in FIG. 9 is the same as in the second embodiment.

When the ignition switch 57 is turned on when starting engine operation, the initial value setting process shown in FIG. 14 is executed. Referring to FIG. 14, first, in step 220, the engine cooling water temperature TW detected by the water temperature sensor 56 is set to a predetermined constant water temperature TW0.
For example, it is determined whether the temperature is 0° C. or higher. If the engine cooling water temperature TW is 0° C. or higher, the process proceeds to step 221, where the water temperature flag TLF is set to the value 0, and then the process proceeds to step 223. On the other hand, when the engine cooling water temperature TW is below 0°C, that is, when the engine starts at a cryogenic temperature, step 222
The process proceeds to step 223, where the water temperature flag TLF is set to the value 1, and then the process proceeds to step 223. In step 223, the value of flag SF is reset to zero. Then step 224
Then, the value of the counter NS is cleared to 0. Next, in step 225, the value of the counter NH is cleared to zero. Next, in step 226, the value of the starting rotation speed determination flag HNF is reset to zero. Then step 2
27, the value of the fuel pressure flag HIF is reset to zero.

Similar to the interrupt routine shown in FIG. 5, the interrupt routine shown in FIGS. 15 and 16 is similar to the interrupt routine shown in FIG.
It is executed once per cycle of the fuel injection pump 32 by an interruption by an output pulse output from the crank angle sensor 58 at the engine crank angle corresponding to the position .

Referring to FIGS. 15 and 16, first, in step 230, it is determined whether the value of the water temperature flag TLF is 1 or not. If the value of the water temperature flag TLF is not 1, the process advances to step 231, subroutine A (see FIGS. 6 and 7) is called, and this interrupt routine is ended. On the other hand, if the value of the water temperature flag TLF is 1 in step 230, that is, if the engine cooling water temperature TW when engine operation is started is 0° C. or lower, the process proceeds to step 232. From step 232 to step 236, step 1 of subroutine A
38 to step 142 (see FIG. 6), the starting rotation speed determination flag HNF is set.

Next, in step 237, it is determined whether the value of the starting rotation speed determination flag HNF is 0 or not. If the value of the starting rotation speed determination flag HNF is 0, the process proceeds to step 238, where it is determined whether the elapsed time C from the start of cranking is a predetermined fixed time C0, for example, 3 seconds or less. Ru. Step 239 if the elapsed time C from the start of cranking is 3 seconds or less
Then, the closing start timing RC (see FIG. 2) of the control valve 52 is set to a predetermined initial value RC0. The initial value RC0 of the valve closing start timing of the control valve 52 is set, for example, to the timing when the plunger 41 is located at the top dead center. In this case, since the closing end timing RO of the control valve 52 is fixed at the timing when the plunger 41 is located at the top dead center as shown in FIG. 2, the control valve 52 is always kept open. become. Next, in step 240, the control valve 5
The actuator 53 of the control valve 52 is driven so that the control valve 2 is kept open at all times. Then step 2
41, the value 0 is set to the fuel pressure flag HIF. Next, in step 242, the value of the counter NH is cleared to 0, and this interrupt routine is ended.

On the other hand, if it is determined in step 237 that the value of the starting rotation speed determination flag HNF is not 0, or if it is determined in step 238 that the elapsed time C from the start of cranking is 3 seconds or more, Proceed to step 243. The processing contents from step 243 to step 261 are the same as the processing contents from step 143 to step 161 of subroutine A (see FIG. 7).

Next, a fifth embodiment will be described with reference to FIGS. 8, 9, 14, 17 and 18. In this fifth embodiment, as in the fourth embodiment, a predetermined period of time C
0, for example, during the period SP0 until 3 seconds have passed,
The control valve 52 is controlled to open and close so that the valve closing period RCP of the control valve 52 becomes a predetermined valve closing period RCP0, for example, an extremely short period close to zero. However, in the fifth embodiment, unlike the fourth embodiment, when 3 seconds elapse from the start of cranking when the engine is started at a cryogenic temperature, the fuel pressure in the common rail 29 decreases regardless of the value of the engine speed N at that time. P is a predetermined high target fuel pressure Ph, for example 10 MPa
The valve-closing period RCP of the control valve 52 is feedback-controlled so that.

The interrupt routine shown in FIGS. 17 and 18 corresponds to the interrupt routine shown in FIGS. 15 and 16 when the plunger 41 of the fuel injection pump 32 is, for example, at a position of 30° before bottom dead center. This is executed once per cycle of the fuel injection pump 32 by an interruption by an output pulse output from the crank angle sensor 58 at the engine crank angle. In addition, FIGS. 17 and 18
The processing contents of each step shown in FIG. 15 and FIG.
The processing content of each step with the same reference numeral shown in 6 is the same.

Next, a sixth embodiment will be described with reference to FIGS. 19 to 22 and FIG. 9. The configuration of the sixth embodiment shown in FIG. 19 is almost the same as the configuration of the third embodiment shown in FIG. Differences from the configuration of the third embodiment shown in FIG. 10 will be explained. Referring to FIG. 19, a fuel relief passage 82 is branched from the common rail 29. This fuel relief passage 82 is branched into a first fuel relief passage 85 , a second fuel relief passage 86 , and a third fuel relief passage 93 via a switching valve 92 . First fuel relief passage 85
is connected to the fuel tank 48, and this first fuel relief passage 8
A high pressure relief valve 87 is disposed within 5. Also, the second
The fuel relief passage 86 is connected to a first fuel relief passage 85 downstream of the high pressure relief valve 87 , and a low pressure relief valve 88 is disposed within the second fuel relief passage 86 . Further, the third fuel relief passage 93 is connected to the first fuel relief passage 85 downstream of the high pressure relief valve 87. An output port 67 of the electronic control unit 60 is connected to a switching valve 92 via a drive circuit 95, and switching of the switching valve 92 is controlled by an output signal from the electronic control unit 60.

When the fuel relief passage 82 is connected to the first fuel relief passage 85 by the switching action of the switching valve 92, the common rail 29 is connected to the fuel tank 48 via the high pressure relief valve 87. In this case, as in the case of the third embodiment shown in FIG. 10, the fuel pressure P in the common rail 29 is set to a predetermined constant high pressure Ph, for example 10 MPa.
When the pressure exceeds this point, the high pressure relief valve 87 opens, and the fuel in the common rail 29 is returned to the fuel tank 48 via the fuel relief passage 82 and the first fuel relief passage 85. Therefore, the high pressure relief valve 87 serves to maintain the fuel pressure P in the common rail 29 at a predetermined constant high pressure Ph. On the other hand, when the fuel relief passage 82 is connected to the second fuel relief passage 86 by the switching action of the switching valve 92, the common rail 29 is connected to the fuel tank 48 via the low pressure relief valve 88. In this case, the third
As in the case of the embodiment, the fuel pressure P in the common rail 29
is a predetermined constant low pressure Pl, for example 1 MPa
When the pressure exceeds this point, the low pressure relief valve 88 opens, and the fuel in the common rail 29 is returned to the fuel tank 48 via the fuel relief passage 82 and the second fuel relief passage 86. Therefore, the low pressure relief valve 88 serves to maintain the fuel pressure P in the common rail 29 at a predetermined constant low pressure Pl. Further, when the fuel relief passage 82 is connected to the third fuel relief passage 93 by the switching action of the switching valve 92,
The fuel sent into the common rail 29 from the fuel injection pump 80 is directly returned into the fuel tank 48 via the fuel relief passage 82 and the third fuel relief passage 93. As can be seen from FIG. 19, the switching valve 92, high pressure relief valve 87, and low pressure relief valve 88 constitute a control valve 94 that controls the amount of fuel discharged from the common rail 29 via the fuel relief passage 82.

Next, a method of controlling the control valve 94 will be explained with reference to FIG. When the engine is started at normal temperature, the switching action of the switching valve 92 causes the common rail 29 to flow through the fuel relief passage 82, the low pressure relief valve 88, and the second fuel relief passage 86, as in the case of the third embodiment shown in FIG. and is connected to a fuel tank 48. As a result, the fuel pressure P in the common rail 29 is maintained at a predetermined constant low pressure Pl, and low-pressure fuel is injected from the high-pressure fuel injection valve 25 into the combustion chamber 5. Next, the engine rotation speed N is set to a predetermined engine start judgment rotation speed N1.
, the common rail 29 is connected to the fuel relief passage 82, the high pressure relief valve 87 and the first fuel relief passage 8 due to the switching action of the switching valve 92 as in the case of the third embodiment.
5 to a fuel tank 48. As a result, the fuel pressure P in the common rail 29 is maintained at a predetermined constant high pressure Ph, and high pressure fuel is injected from the high pressure fuel injection valve 25 into the combustion chamber 5.

On the other hand, when starting the engine at a very low temperature, where it is particularly difficult to ensure good engine startability, for example, the engine cooling water temperature TW
When starting the engine when the temperature is below 0°C, the switching action of the switching valve 92 causes the common rail 29 to switch between the fuel relief passage 82 and It is connected to the fuel tank 48 via a third fuel relief passage 93. As a result, the fuel sent into the common rail 29 from the fuel injection pump 80 directly passes through the fuel relief passage 82 and the third fuel relief passage 93 to the fuel tank 4.
In this way, the fuel pressure P in the common rail 29 is maintained at an extremely low pressure below the discharge pressure Pf of the fuel supply pump 49. In this way, the discharge pressure of the fuel injection pump 80 becomes extremely low, so the driving torque of the fuel injection pump 80 is significantly reduced, and as a result, the engine cranking speed can be quickly increased even when the engine is started at a very low temperature. can be raised. Note that during this period SP0, the fuel pressure P in the common rail 29 is extremely low as described above, so it does not matter whether fuel is injected from the high-pressure fuel injection valve 25 or not.

Next, when a predetermined period of time C0 has elapsed from the start of cranking, the common rail 29 is connected to the fuel tank 48 via the low pressure relief valve 88 by the switching action of the switching valve 92. As a result, common rail 2
The fuel pressure P in the combustion chamber 9 is maintained at a predetermined constant low pressure Pl, and low-pressure fuel is injected from the high-pressure fuel injection valve 25 into the combustion chamber 5. Since the engine cranking rotational speed is quickly increased during the above-mentioned period SP0, engine combustion is started quickly, and good engine startability is thus ensured even when the engine is started at a cryogenic temperature. Next, when combustion of the engine is started and the engine speed N becomes higher than a predetermined engine start judgment speed N1, for example, 600 rpm, the common rail 29 is moved through the high pressure relief valve 87 by the switching action of the switching valve 92. and is connected to a fuel tank 48. As a result, the fuel pressure P in the common rail 29 is kept at a predetermined constant high pressure Ph.
from the high pressure fuel injection valve 25 to the combustion chamber 5.
High pressure fuel is injected inward. That is, the process shifts to fuel injection during normal engine operation. Note that if engine combustion starts and the engine speed N exceeds the engine start judgment speed N1 before a predetermined period of time C0 has elapsed from the start of cranking, the common rail 29 is at high pressure. The switching valve 92 is controlled to be connected to the relief valve 87 . As can be seen from the above description, the sixth embodiment achieves the same effect as the fourth embodiment shown in FIG. 8 by using the configuration shown in FIG. 19.

Next, the flow of the opening/closing control of the control valve 94 in the sixth embodiment will be explained with reference to FIGS. 9 and 20 to 22. Note that the main routine shown in FIG. 9 is the same as in the second embodiment.

When the ignition switch 57 is turned on to start engine operation, the initial value setting process shown in FIG. 20 is executed. Referring to FIG. 20, first, in step 270, the engine cooling water temperature TW detected by the water temperature sensor 56 is set to a predetermined constant water temperature TW0.
For example, it is determined whether the temperature is 0° C. or higher. If the engine cooling water temperature TW is 0° C. or higher, the process proceeds to step 271, where the water temperature flag TLF is set to the value 0, and then the process proceeds to step 273. On the other hand, when the engine cooling water temperature TW is below 0°C, that is, when the engine starts at a cryogenic temperature, step 272
The process proceeds to step 273, where the water temperature flag TLF is set to the value 1, and then the process proceeds to step 273. In step 273, the value of the counter NH is cleared to zero. Then step 274
Then, the value of the starting rotation speed determination flag HNF is reset to zero. Next, in step 275, the fuel pressure flag H
The value of IF is reset to 0.

The interrupt routine shown in FIGS. 21 and 22 is executed once per cycle of the fuel injection pump 80, similar to the interrupt routine shown in FIG. Figure 21
and FIG. 22, first step 280
It is determined whether the value of the water temperature flag TLF is 1 or not. If the value of the water temperature flag TLF is not 1, the process advances to step 281, subroutine B (see FIG. 13) is called, and this interrupt routine is ended.

On the other hand, if the value of the water temperature flag TLF is 1 in step 280, that is, if the engine cooling water temperature TW at the start of engine operation is 0° C. or lower, the process proceeds to step 282. In steps 282 to 286, the starting rotation speed determination flag HNF is set in the same manner as in steps 200 to 204 (see FIG. 13) of subroutine B.

Next, in step 287, it is determined whether the value of the starting rotation speed determination flag HNF is 0 or not. If the value of the starting rotation speed determination flag HNF is 0, the process proceeds to step 288, where it is determined whether the elapsed time C from the start of cranking is a predetermined fixed time C0, for example, 3 seconds or less. Ru. If the elapsed time C from the start of cranking is less than 3 seconds, step 289
, and connect the fuel relief passage 82 to the third fuel relief passage 93.
The switching valve 92 is controlled so as to be connected to. Next, in step 290, the fuel pressure flag HIF is set to the value 0, and then in step 291, the value of the counter NH is cleared to 0, and this interrupt routine is ended.

On the other hand, if it is determined in step 287 that the value of the starting rotation speed determination flag HNF is not 0, or if it is determined in step 288 that the elapsed time C from the start of cranking is 3 seconds or more, Proceed to step 292. The processing content from step 292 to step 300 is the same as the processing content from step 205 to step 213 (see FIG. 13) of subroutine B.

Next, a seventh embodiment will be described with reference to FIGS. 9, 19, 20, 23 and 24. In this seventh embodiment, as in the sixth embodiment, a predetermined period of time C0 is set from the start of cranking when the engine is started at a cryogenic temperature.
For example, during the period SP0 until 3 seconds have elapsed, the common rail 29 is connected to the third fuel relief passage 93 via the fuel relief passage 82 by the switching action of the switching valve 92. However, in the seventh embodiment, unlike the sixth embodiment, when 3 seconds elapse from the start of cranking when the engine is started at a cryogenic temperature, the switching action of the switching valve 92 is stopped regardless of the value of the engine speed N at that time. The common rail 29 is connected to the fuel relief passage 82 by
The high pressure relief valve 87 is connected to the high pressure relief valve 87 via the high pressure relief valve 87.

The interrupt routine shown in FIGS. 23 and 24 is executed once per cycle of the fuel injection pump 80, similar to the interrupt routine shown in FIGS. 21 and 22. Note that the processing content of each step shown in FIGS. 23 and 24 is the same as the processing content of each step with the same reference numeral shown in FIGS. 21 and 22.

[0080] Up to now, the case where the present invention is applied to a two-stroke internal combustion engine has been explained, but the present invention can also be applied to a four-stroke internal combustion engine.
Needless to say, it can also be applied to cycle internal combustion engines.

[0081]

Effects of the Invention Since the driving torque of the fuel injection pump is reduced when starting the engine, the engine speed can be quickly increased, thus providing good engine startability.

[Brief explanation of drawings]

[Fig. 1] 2 to which the fuel injection control device of the first embodiment is applied
1 is an overall diagram of a cycle internal combustion engine.

FIG. 2 is a diagram showing the relationship between the stroke amount of the plunger of the fuel injection pump and the valve closing timing of the control valve.

FIG. 3 is a flowchart of the main routine in the first embodiment.

FIG. 4 is a flowchart of an initial value setting processing routine in the first and second embodiments.

FIG. 5 is a flowchart of a fuel pressure control routine in the common rail in the first and second embodiments.

FIG. 6 is the first half of a flowchart of subroutine A.

FIG. 7 is the second half of the flowchart of subroutine A.

FIG. 8 is an overall view of a two-stroke internal combustion engine to which the fuel injection control devices of the second, fourth, and fifth embodiments are applied.

FIG. 9 is a flowchart of a main routine in second to seventh embodiments.

FIG. 10 is an overall view of a two-stroke internal combustion engine to which the fuel injection control device of the third embodiment is applied.

FIG. 11 is a flowchart of an initial value setting processing routine in the third embodiment.

FIG. 12 is a flowchart of a fuel pressure control routine in the common rail in the third embodiment.

FIG. 13 is a flowchart of subroutine B.

FIG. 14 is a flowchart of an initial value setting processing routine in the fourth and fifth embodiments.

FIG. 15 is the first half of a flowchart of a fuel pressure control routine in the common rail in the fourth embodiment.

FIG. 16 is the second half of a flowchart of a common rail fuel pressure control routine in the fourth embodiment.

FIG. 17 is the first half of a flowchart of a fuel pressure control routine in the common rail in the fifth embodiment.

FIG. 18 is the second half of a flowchart of a common rail fuel pressure control routine in the fifth embodiment.

FIG. 19 is an overall view of a two-stroke internal combustion engine to which the fuel injection control devices of the sixth and seventh embodiments are applied.

FIG. 20 is a flowchart of an initial value setting processing routine in the sixth and seventh embodiments.

FIG. 21 is the first half of a flowchart of a common rail fuel pressure control routine in the sixth embodiment.

FIG. 22 is the second half of a flowchart of a common rail fuel pressure control routine in the sixth embodiment.

FIG. 23 is the first half of a flowchart of a fuel pressure control routine in the common rail in the seventh embodiment.

FIG. 24 is the second half of a flowchart of a common rail fuel pressure control routine in the seventh embodiment.

[Explanation of symbols]

5... Combustion chamber 14...Air supply branch pipe 25...High pressure fuel injection valve 26...Low pressure fuel injection valve 29...Common rail 32...Fuel injection pump 34...pressurization chamber 50...Fuel relief passage 52...Control valve 80...Fuel injection pump 82...Fuel relief passage 84...Switching valve 85...First fuel relief passage 86...Second fuel relief passage 87...High pressure relief valve 88...Low pressure relief valve 89...Control valve 92...Switching valve 93...Third fuel relief passage 94...Control valve

Claims (1)

[Claims] Claim 1. A fuel injection control device for an internal combustion engine, comprising a fuel injection pump that is constantly driven by the engine, and a fuel injection valve disposed in an engine combustion chamber or an engine air supply passage. It is equipped with a control valve that branches a fuel relief passage from the pressurization chamber or the discharge side and controls the amount of fuel discharged through the fuel relief passage, and controls the opening and closing of the control valve to inject fuel when starting the engine. A fuel injection control device for an internal combustion engine that lowers the pressure of fuel supplied to a valve below the pressure after the engine is started.