JPH08319871A - Pressure accumulation type fuel injection device of internal combustion engine - Google Patents

Abstract

PURPOSE: To provide a pressure accumulation type fuel injection device which can jet properly the fuel from an injector even when a high pressure pump goes in failure. CONSTITUTION: A high pressure pump 7 pressurizes the fuel lifted from a fuel tank 8 by a low pressure pump 9 and feeds it by pressure to a common rail 4 via a supply pipe 6. At the common rail 4, the high pressure fuel supplied from the pump 7 is held at a specified high pressure level, and this high pressure fuel is injected into an engine 1 from its injection valve 2 wherein the injecting operation is controlled by a solenoid valve 3. The outlet from the low pressure pump 9 is connected with the common rail 4 via a detour 16, and on the way of this detour 16, a check valve 17 is installed which prevents the high pressure fuel from counterflowing toward the low pressure pump 9 from the common rail 4. Even when the high pressure pump 7 is in failure, it is possible to feed fuel to the common rail 4 from the low pressure pump 9, the engine can be operated continuously.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an internal combustion engine (hereinafter, referred to as
The present invention relates to a fuel injection device in which fuel is injected and supplied to a combustion chamber of an "internal combustion engine".

[0002]

2. Description of the Related Art Conventionally, from the viewpoint of measures against exhaust gas and improvement of fuel consumption rate in a gasoline engine, a fuel injection system has been proposed in which fuel is pressurized by a pump and injected from an injector to an intake manifold or an intake port. Various types of systems in which fuel is directly injected into the room have also been proposed.

In the direct injection type fuel injection device,
It is necessary to control the fuel injection amount and injection timing according to the operating state of the engine, and as a means for this, a solenoid valve is generally provided in the injector, and the nozzle of the injector is opened and closed by turning on and off the power supply to this solenoid valve. Has been taken. However, this control is so-called time control, and the injection condition varies depending on the fuel supply pressure to the injector. Therefore, JP-A-62-645 and the like propose that a common pressure accumulator is provided in the supply passage connecting the fuel pump and the injector, and the fuel pressure is adjusted to a high pressure by this pressure accumulator and supplied to each injector. There is.

[0004]

However, according to the fuel injection device disclosed in Japanese Patent Laid-Open No. 62-645, the fuel pumped from the fuel tank by the low pressure pump is sent under pressure to the pressure accumulator via the high pressure pump. The high-pressure fuel stored in this pressure accumulator is injected and supplied from the injector according to the opening time of the solenoid valve. The high-pressure pump is the only fuel pressure source that supplies fuel to the accumulator, so if a failure occurs in this high-pressure pump, the high-pressure fuel cannot be supplied to the accumulator. There is a problem that fuel injection cannot be performed properly, and as a result, the operation of the engine is stopped and the engine cannot be restarted. The causes of failure of the high-pressure pump are malfunction of the plunger due to foreign matter being caught in the plunger of the high-pressure pump, malfunction of the solenoid valve that adjusts the fuel discharge amount of the high-pressure pump, and disconnection of the electric supply signal line to this solenoid valve. The failure of the electronic control unit that controls this solenoid valve, and the like.

An object of the present invention is to provide a pressure accumulating fuel injection device which can properly inject fuel from an injector even when a high pressure pump fails.

[0006]

According to a first aspect of the present invention, there is provided an accumulator type fuel injection system for an engine, wherein fuel pumped up by a low pressure pump is pressurized by a fuel pressurizing section of a high pressure pump. The pressurized high-pressure fuel is supplied into the common rail to accumulate the pressure, and the first solenoid valve of the first solenoid valve is passed from the common rail through a branch pipe corresponding to each cylinder of the engine and an injection valve provided in the branch pipe. In a pressure-accumulation fuel injection device configured to inject fuel into an engine by opening and closing at a predetermined timing, a bypass passage that bypasses the fuel pressurizing portion and connects the low pressure pump outlet and the common rail inlet is provided. And

According to a second aspect of the present invention, there is provided an accumulator fuel injection system for an engine according to the first aspect, which is a check for preventing backflow of fuel from the common rail to the low pressure pump outlet. A valve is provided in the bypass passage. According to a third aspect of the present invention, there is provided an accumulator type fuel injection system for an engine according to the second aspect, wherein the bypass passage and the check valve are provided inside the high pressure pump.

According to a fourth aspect of the present invention, there is provided an accumulator type fuel injection system for an engine according to the first aspect of the present invention, wherein the fuel discharge amount of the high pressure pump is adjustable. And a control device for inputting signals indicating various operating states of the engine and controlling opening and closing of the second solenoid valve based on the signals, and a pressure sensor for detecting the common rail internal pressure, When the pressure value detected by the pressure sensor becomes equal to or lower than a predetermined value, the control device stops the operation of the second electromagnetic valve.

According to a fifth aspect of the present invention, there is provided the fuel pressure accumulation type fuel injection system for an engine according to the first aspect of the present invention, wherein the low pressure pump is an electric pump. And a control device capable of sending a control signal for controlling the rotation speed of the low pressure pump to the low pressure pump based on a pressure detection signal from the pressure sensor.

[0010]

According to the first aspect of the present invention, there is provided a bypass passage for bypassing the fuel pressurizing portion of the high pressure pump and connecting the low pressure pump outlet and the common rail inlet with each other. As a result, fuel can be supplied from the low-pressure pump to the common rail. Therefore, even if the high-pressure fuel is not supplied from the high-pressure pump to the common rail when the high-pressure pump fails, the fuel can be injected into the engine and the engine can be continuously operated.

According to a second aspect of the present invention, there is provided a fuel injection system for accumulating fuel for an engine, wherein a check valve for preventing a backflow of fuel from the inside of the common rail to the outlet of the low pressure pump is provided in the bypass passage so that the engine is operated normally. In, the fuel is favorably supplied from the low pressure pump to the high pressure pump. According to the engine pressure-accumulation fuel injection device of the third aspect of the present invention, by providing the bypass passage and the check valve inside the high-pressure pump, it is not necessary to additionally install a fuel pipe for the bypass passage around the engine.

According to a fourth aspect of the present invention, there is provided a fuel injection device for a high pressure pump, wherein when the pressure value detected by the pressure sensor for detecting the pressure in the common rail is below a predetermined value. By stopping the operation of the second solenoid valve that adjusts, the power consumption of the engine when the high-pressure pump fails can be reduced. According to the accumulator fuel injection system for an engine of claim 5 of the present invention, the rotational speed of the low pressure pump is controlled based on the pressure detection signal from the pressure sensor for detecting the pressure in the common rail, so that when the high pressure pump fails. Can adjust the fuel pressure supplied to the common rail.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows the overall system of a pressure-accumulation type fuel injection device according to a first embodiment of the present invention. As shown in FIG. 1, the engine 1 is provided with an injection valve 2 corresponding to the combustion chamber of each cylinder. The engine 1 has four cylinders, but the number of cylinders is not limited in the present invention. In the first embodiment, the fuel injection performed from the four injection valves 2 to the corresponding cylinders is controlled by turning on and off the solenoid valve 3, which is the first solenoid valve for injection control. It The inlet side of these injection valves 2 is connected to a high-pressure accumulator pipe (hereinafter, “high-pressure accumulator pipe” is referred to as Commodore) 4 common to each cylinder. The high pressure fuel is stored in the common rail 4, and the high pressure fuel accumulated in the common rail 4 is injected by the opened solenoid valve 3 while the solenoid valve 3 is open. Fuel is injected into the engine 1 from the controlled injection valve 2.

It is necessary for the common rail 4 to continuously accumulate a high-pressure fuel corresponding to the fuel injection pressure. Therefore, the common rail 4 is connected to the high-pressure pump 7 via the supply pipe 6 and the check valve 5. Has been done. The high-pressure pump 7 pressurizes the fuel pumped up by the low-pressure pump 9 from the fuel tank 8 to a high pressure, and feeds it to the common rail 4 via the supply pipe 6. The common rail 4 holds the high pressure fuel supplied from the high pressure pump 7 at a predetermined high pressure.

In order to control the on / off of the solenoid valve 3, an electronic control unit (hereinafter "electronic control unit" is referred to as an ECU
11) is used, and this ECU 11 has
For example, the engine speed sensor 12 and the load sensor 13
The information on the engine speed and the engine load is input from the ECU 11, and the ECU 11 calculates the optimum fuel injection timing and the fuel injection amount according to the engine operating state judged by these information, and based on the calculation result, the solenoid valve is operated. The control signal is output to 3. In addition, the ECU 11 has a common rail 4
Information such as a pressure detection signal is also input from the pressure sensor 14 that detects the fuel pressure inside. Further, the ECU 11 sends a control signal for adjusting the fuel discharge amount of the high-pressure pump 7 to the control device 10, which is the second solenoid valve, so that the injection pressure becomes the optimum value according to the engine speed and the engine load. ing.
Further, the ECU 11 can send a control signal for adjusting the rotation speed of the low-pressure pump 9 to the low-pressure pump 9.

The high pressure pump 7 and the low pressure pump 9 are connected by a fuel passage 18. Further, the outlet side of the low-pressure pump 9 and the common rail 4 are connected by a bypass passage 16. The bypass passage 16 bypasses the high pressure pump 7 from the low pressure pump 9 and is connected to the common rail 4. A check valve 17 is provided in the bypass passage 16 so that high-pressure fuel does not flow backward from the common rail 4 to the low-pressure pump 9. Thus, when the pressure in the common rail 4 is lower than the pressure on the outlet side of the low pressure pump 9, the low pressure pump 9 does not pass through the high pressure pump 7 and the common rail 4 moves.
Fuel can be supplied through the bypass passage 16.

During normal operation, the high-pressure fuel pressurized by the high-pressure pump 7 is supplied from the fuel passage 18 into the common rail 4. The fuel in the common rail 4 is supplied to the high pressure pump 7 and the low pressure pump 9 by the check valve 5 and the check valve 17.
It does not flow back to the side. As a result, the pressure inside the common rail 4 is maintained at a predetermined high pressure. Next, the structure of the high pressure pump 7 will be described.

The high-pressure pump 7 is provided with a plunger, which is a fuel pressurizing portion that reciprocates in response to a cam of a camshaft driven by a crankshaft of an engine (not shown). The fuel is sucked into the chamber and the fuel is pressurized in the pressure chamber. Then, the amount of fuel discharged from the high-pressure pump 7 is adjusted by the discharge amount control device 10 having the second solenoid valve capable of opening and closing the overflow passage for overflowing the fuel in the pressure chamber to the low pressure side. The high-pressure fuel pressurized in the pressure chamber is supplied from the fuel passage 18 to the common rail 4 at a predetermined timing.

The operation of the high pressure pump 7 will be described with reference to FIGS. As shown in FIG. 2, the pump head 3
The pressure chamber 33 formed by 0, the pump housing 31, and the end surface of the plunger 32 has a suction port 36 for sucking fuel from the low-pressure pump 9 and a discharge port 39 for supplying fuel to the common rail 4 side. Suction port 36 and pressure chamber 33
The valve member 38 composing a part of the discharge amount control device 10 is reciprocally moved to and disconnected from the valve member 38, and the valve member 38 is controlled to be opened and closed by a drive unit of the discharge amount control device 10. By energizing the coil 37, the movable piece (not shown) coupled to the valve member 38 is attracted upward in FIG. 2 by the electromagnetic attraction force.

As shown in FIG. 2, when the plunger 32 is lowered in FIG. 2 when the valve member 38 is in the open state, the fuel is sucked from the suction port 36 into the high pressure chamber 33. At this time, the check valve 5 is closed due to the high pressure on the common rail 4 side. When the plunger 32 reaches the lowermost position, it starts rising again. As shown in FIG. 3, when the plunger 32 reaches the desired position (the timing for turning on the metering valve final drive),
The valve member 38 moves from the state shown in FIG. 3 in the valve closing direction, which is above 3. A part of the fuel in the pressure chamber 33 is returned to the low pressure pump side via the suction port 36 until the plunger 32 starts to rise from the lowermost position and the valve member 38 is closed. When the valve member 38 shifts to the valve closed state from the state shown in FIG.
5, the valve member 34 is pushed open in the valve opening direction to open the fuel passage 1
High-pressure fuel is pumped into the common rail 4 from 8. This pressure feeding process is performed until the plunger 32 reaches the uppermost position. When the plunger 32 reaches the uppermost position, the solenoid valve of the discharge amount control device 10 switches from on to off, and the valve member 38 shifts from the valve closed state to the valve open state with a time delay. After this valve open state, as shown in FIG. 2, the pressure chamber 33 is passed again from the suction port 36 through the periphery of the valve member 38.
Inhale fuel into. By repeating this operation, fuel is supplied from the high pressure pump 7 to the common rail 4 via the fuel passage 18, and the high pressure fuel is accumulated in the common rail 4. Since the electromagnetic valve of the discharge amount control device 10 operates as a metering valve, the "solenoid valve of the discharge amount control device 10" is hereinafter referred to as a metering valve.

Next, FIG. 5 shows the relationship between the drive pulse of the metering valve, the lift of the metering valve, and the plunger lift amount. The plunger lift amount repeats the reciprocating motion according to the cam peak of the cam shaft of the high pressure pump (not shown). The metering valve drive pulse switches from OFF to ON when the plunger lift amount has a desired value, and the ON state switches the metering valve from open to closed. On the contrary, when the metering valve drive pulse changes from the on state to the off state, the metering valve switches from the closed state to the open state with a time delay thereafter. The switching of the metering valve drive pulse from ON to OFF occurs when the plunger lift amount reaches the maximum amount. The switching of the metering valve drive pulse from OFF to ON is controlled when the plunger reaches the desired lift position, and this timing is a predetermined elapsed time from the reference position detected from the cam angle signal. It is determined by the final drive ON timing T _P of the metering valve. This metering valve final drive ON timing T _P is determined according to the engine speed and the engine load as described above. Generally, the fuel discharge amount is adjusted by decreasing T _P when the load is high and increasing T _P when the load is low.

In FIG. 5, the metering valve for the metering valve drive pulse
Final drive on timing T_P1And T_P2Are each
In contrast, it shows when the fuel discharge amount is large and when the fuel discharge amount is small.
ing. Adjusting valve drive pulse to T_P1Switch from off to on
Then, the plunger stroke of the plunger lift S1
The fuel discharge amount corresponds to the _P2
When switched from off to on with, the plunger lift S2
The fuel discharge amount corresponds to the plunger stroke.

Next, a control system for controlling the metering valve will be described. The ECU 11 inputs an engine rotation speed signal from the rotation speed sensor 12, an engine load signal from the load sensor 13, a pressure detection signal in the common rail 4 from the pressure sensor 14, and the like, and fetches an engine operating state signal from these pieces of information. . This operation flowchart is shown in FIG.
As shown in FIG. 6, in step 101, the engine operating state signal is fetched, and in step 102, the fuel injection amount q
Is calculated, the injection timing T ₁ is calculated in step 103, and fuel pressure control is performed in step 104. The fuel pressure control in step 104 is specifically executed by the fuel pressure control routine shown in FIG. Next, the fuel pressure control routine shown in FIG. 7 will be described.

In step 201, the engine operating state signal
Is taken in, and in step 202 the target fuel pressure P_TCalculate
Then, in step 203, the metering valve basic drive on timing
Ng T_BTo calculate. Then, in step 204, P
_C(Actual fuel pressure) -P_TIs greater than the predetermined reference pressure ΔP
Judge whether it is good or not, | P_C−P_T│> ΔP
That is, in this case, the actual fuel pressure is relatively close to the target fuel pressure.
This shows the state, at which time the metering valve final drive on
Imming correction value T_FBAs the correction value
Timing T_PTo calculate. This procedure is step 20
6 and final drive of metering valve as shown in step 213
On timing T_P= T_B(Basic timing) + T
_FB(Feedback correction timing)
It In step 204, | P_C−P_T|> ΔP
If it is determined that P_C> P_T
Whether or not P,_C> P_TIf so, step 2
Go to 08 T_FBTo T_FBReplace with + ΔT. I.e. key
Volume valve final drive ON timing T_PDelay. This
Reduce fuel delivery. P in step 205_C
≤P _TIf it is determined that the
See, T_FB= T_FB-Set to ΔT, then proceed to step 209.
See, T_FB<T_FGOr not. T_FB≧ T_FGso
If there is, go to step 213. Smell in step 209
T_FB<T_FGIf it is determined that
Diagnose an obstacle and count the counter value from this point
Then, in step 210, the count value C_PFAdd +1
Calculate Then proceed to step 211 and count value C_PF>
Predetermined value C_KOr not. This is a high pressure fuel
After the pump error occurs, count value C_PFIs the predetermined value C_KTo
It is judged whether or not it exceeds, and a predetermined value C_KWhen not exceeding
At step 213, the metering valve final drive ON timing T
_PIs calculated and the high pressure pump is driven by this value. Coun
Value C_PFIs the predetermined value C_KWhen it exceeds the step 211
Then, the process proceeds to step 212, and the drive of the metering valve is stopped. That
After that, from the low-pressure pump 9 to the common passage via the bypass passage 16.
Fuel is supplied into the container 4.

Next, the engine speed, the pressure in the accumulator pipe,
The metering valve drive pulse, the injector solenoid valve drive pulse, and the high-pressure pump failure determination will be described with reference to FIG. As shown in FIG. 8, when an abnormality occurs in the high-pressure pump, that is, when the normal fuel is not supplied and discharged from the high-pressure pump, the fuel pressure in the common rail gradually decreases,
When the counter counts a certain value, it is determined that the high pressure pump has failed, and after this determination, driving of the metering valve in the high pressure pump is stopped. That is, the drive pulse of the metering valve is stopped. After that, the fuel pressure in the common rail gradually decreases, but the injection pulse of the injector is relatively increased to increase the injection amount and maintain the engine speed at a constant value. When the fuel pressure in the common rail further decreases to the discharge pressure of the low-pressure pump 9, the check valve 17 opens to allow the low-pressure pump 9 to bypass the bypass passage 1.
Fuel is supplied into the common rail 4 via 6. After that, the driving pulse valve opening time of the injector becomes long and the engine speed is maintained at a predetermined value. In the present invention, when the high-pressure pump 7 fails, the control signal for increasing the rotation speed is sent from the ECU 11 to the low-pressure pump 9 to keep the engine rotation speed at a predetermined value.

On the other hand, in the conventional comparative example, since the fuel from the low-pressure pump 9 cannot be supplied into the common rail 4, the fuel pressure in the common rail further decreases as shown by the dotted line in FIG. The internal fuel pressure drops to atmospheric pressure, the engine speed drops sharply, and the operation of the engine 1 stops. In the present embodiment, such a situation that the operation of the engine 1 is stopped is avoided, and the fuel discharged from the low-pressure pump 9 is supplied to the engine 1 from the common rail 4 through the injector in accordance with the operation of the solenoid valve 3. 1 operation can be maintained.

Therefore, when the high pressure pump fails, for example, EC
Uncontrollable U11, discharge amount control device 10 having a metering valve
When the fuel cannot be pressure-fed from the high-pressure pump 7 to the common rail 4 due to a malfunction such as a malfunction of the engine or a foreign substance caught in the plunger 32, a low pressure is supplied to the common rail 4 from the low-pressure pump 9 via the bypass passage 16. By supplying the fuel, the fuel can be injected and supplied from the injection valve to the engine. (Second Embodiment) A second embodiment of the present invention is shown in FIG.

The second embodiment shown in FIG. 9 is an embodiment in which a fuel passage for bypassing the low pressure pump and bypassing the high pressure pump to supply fuel to the common rail is formed in the high pressure pump. As shown in FIG. 9, a bypass passage 46 that connects the suction port 36 and the fuel supply passage 48 to the common rail 4 is formed in the pump head 30 of the high-pressure pump 7. This detour passage 46
A check valve 47 is provided therein to prevent the reverse flow of fuel from the common rail 4 side to the high pressure pump 7 side. Since other configurations are similar to those of the first embodiment, the components substantially the same as those shown in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

According to the second embodiment, since the bypass passage 46 which is not affected by the operation of the plunger 32 which is the fuel pressurizing portion of the high pressure pump 7 is formed in the pump head 30 of the high pressure pump 7, even when the high pressure pump fails. The fuel can be supplied from the low-pressure pump 9 to the common rail 4 without separately providing a pipe around the engine. The metering valve operates in the same manner as in the first embodiment during normal operation and failure of the high pressure pump 4.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a pressure accumulation type fuel injection device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing the operation of the main part of the high-pressure pump of the first embodiment.

FIG. 3 is a sectional view showing the operation of the main part of the high-pressure pump of the first embodiment.

FIG. 4 is a sectional view showing the operation of the main part of the high-pressure pump of the first embodiment.

FIG. 5 is a cam angle signal of the high-pressure pump according to the first embodiment,
It is a time chart of a metering valve drive pulse, a metering valve lift, and a plunger lift.

FIG. 6 is a flowchart showing a main routine of fuel pressure control by the high pressure pump of the first embodiment.

FIG. 7 is a flowchart showing a fuel pressure control routine according to the first embodiment.

FIG. 8 is a time chart showing an engine speed, a fuel pressure in a common rail, a metering valve drive pulse in a high-pressure pump, a solenoid valve drive pulse in an injector, and a high-pressure pump failure determination signal between an example of the present invention and a conventional comparative example. Is.

FIG. 9 is a sectional view showing a main part of a high-pressure pump according to a second embodiment of the present invention.

[Explanation of symbols]

 1 engine 3 solenoid valve (first solenoid valve) 4 common rail 5 check valve 6 fuel passage 7 high-pressure pump 9 low-pressure pump 10 discharge rate control device (second solenoid valve) 11 ECU (control device) 12 rotation speed sensor 13 load Sensor 14 Pressure sensor 16 Detour passage 17 Check valve 18 Fuel passage 32 Plunger (fuel pressurization part) 33 Pressure chamber 36 Suction port 37 Coil 38 Valve member 39 Discharge port 46 Detour passage 47 Check valve

Claims (5)

[Claims] 1. The fuel pumped up by a low-pressure pump is pressurized by a fuel pressurizing unit of a high-pressure pump, the pressurized high-pressure fuel is supplied into a common rail to accumulate pressure, and from the common rail to each cylinder of an internal combustion engine. In the pressure-accumulation fuel injection device, which is configured to inject fuel into an internal combustion engine at a predetermined timing by opening and closing a first electromagnetic valve through an injection valve provided in the branch pipe via a corresponding branch pipe. An accumulator type fuel injection device for an internal combustion engine, characterized in that a bypass passage is provided that bypasses a portion and communicates the low pressure pump outlet and the common rail inlet. 2. The pressure-accumulation fuel injection device for an internal combustion engine according to claim 1, wherein a check valve for preventing backflow of fuel from the inside of the common rail to the outlet of the low-pressure pump is provided in the bypass passage. 3. The pressure-accumulation fuel injection device for an internal combustion engine according to claim 2, wherein the bypass passage and the check valve are provided inside the high-pressure pump. 4. A second solenoid valve capable of adjusting the fuel discharge amount of the high-pressure pump, and a signal indicating various operating states of the internal combustion engine are input, and the second solenoid valve is opened / closed based on this signal. A control device that controls the pressure and a pressure sensor that detects the pressure in the common rail are provided. When the pressure value detected by the pressure sensor becomes equal to or lower than a predetermined value, the control device operates the second solenoid valve. The pressure-accumulation fuel injection device for an internal combustion engine according to claim 1, 2 or 3, which is stopped. 5. The low-pressure pump is an electric pump, and a pressure sensor for detecting the pressure in the common rail, and a control signal for controlling the rotation speed of the low-pressure pump based on a pressure detection signal from the pressure sensor are supplied to the low-pressure pump. 3. A control device capable of delivering to a pump.
Alternatively, the pressure-accumulation fuel injection device for an internal combustion engine according to the item 3.