JP3063610B2 - Fuel supply device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for an internal combustion engine which can perform fuel injection at a high pressure and is suitable for use in a cylinder injection type internal combustion engine.

[0002]

2. Description of the Related Art At present, fuel supplied to an internal combustion engine by a fuel injection valve is increasing. However, fuel injection by such a fuel injection valve requires fuel supply to the fuel injection valve at a predetermined fuel pressure. In particular, fuel injection at high pressure may lead to efficient combustion.

For example, in an internal combustion engine (hereinafter referred to as an engine) called a direct injection type internal combustion engine or a direct injection type internal combustion engine (direct injection type internal combustion engine), fuel is directly injected into a cylinder. Is provided with a fuel injection valve. In such a direct injection internal combustion engine, the fuel injection can be performed at an arbitrary timing, so that the fuel injection can be performed in the compression stroke of the engine according to the operating state of the engine in order to improve the fuel efficiency and the like.

That is, in a direct injection type engine, for example, the fuel is not entirely mixed by injecting the fuel in the compression stroke of the engine, but the air-fuel ratio in which the vicinity of the ignition plug is partially ignited is set. As a whole, a combustion operation having an extremely large air-fuel ratio (ultra-lean combustion operation) can be performed, and stable combustion can be performed while improving fuel efficiency.

Therefore, when the engine is idling or at a low load, the output of the engine is not so much required. Therefore, the lean burn operation by the fuel injection in the compression stroke is performed to improve the fuel efficiency, and when the engine load becomes large, the fuel in the intake stroke is increased. And the engine output required for stoichiometric or rich combustion operation by fuel injection during the intake stroke.

When performing in-cylinder injection in the compression stroke, a particularly high fuel injection pressure is required. Also,
Although not limited to the cylinder injection type engine, an engine having a supercharging mechanism requires a high fuel injection pressure according to the supercharging pressure at the time of supercharging. Therefore, for example, Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 83134 (first prior art) proposes a fuel supply device capable of obtaining a sufficiently high fuel injection pressure (for example, about several tens of atmospheres).

[0007] For example, a configuration as shown in FIGS. 7 and 8 has been conventionally proposed. 7 and 8, reference numeral 1 denotes a fuel injection valve (injector), 2 denotes a fuel tank, 3 denotes a fuel passage, and 4 denotes a low-pressure fuel pump provided upstream of the fuel passage 3 on the fuel tank 2 side. Is a high-pressure fuel pump provided between the low-pressure fuel pump and the fuel injection valve 1. Reference numeral 6 denotes a fuel filter provided at the inlet of the fuel passage, 7 and 12 denote check valves, 8 denotes a low-pressure regulator as low-pressure control means, 9 denotes an electromagnetic switching valve (switching valve), and 10 denotes a fuel pressure holding mechanism. , 14 are high-pressure regulators as high-pressure control means. 21 is a cylinder, 22 is a piston, 23 is a combustion chamber, 24 is a cylinder head, 25 is an intake passage, 26 is a spark plug, and 27 is an exhaust passage.

The fuel passage 3 is composed of a supply passage 3A for supplying fuel from the fuel tank 2 to the injector 1, and a return passage 3B for returning fuel not injected by the injector 1 to the fuel tank 2. I have. In addition, injector 1
Is supplied with fuel through the delivery pipe 1A,
Here, it is considered that the delivery pipe 1A itself is a part of the fuel passage 3.

The low-pressure fuel pump 4 is an electric feed pump provided in the fuel tank 2 upstream of the feed passage 3A of the fuel passage 3. The low-pressure fuel pump 4 is started when the engine is started.
When the engine is stopped, the engine stops, but a predetermined discharge pressure can be generated without depending on the rotation speed of the engine, and the fuel is pressurized from the state of the atmospheric pressure to about several atmospheres. The high-pressure fuel pump 5 pressurizes the fuel discharged from the low-pressure fuel pump 4 to about several tens of atmospheres. The high-pressure fuel pump 5 is provided with a reverse pump provided in the middle of a feed path 3A from the low-pressure fuel pump 4 to the high-pressure fuel pump 5. The discharge pressure from the low-pressure fuel pump 4 is maintained by the stop valve 7.

As the high-pressure fuel pump 5, an engine-driven pump (hereinafter referred to as an engine-driven pump) is used. The engine operates directly in conjunction with the operation of the engine, and depends on the rotational speed of the engine. Generates discharge pressure. Further, the discharge pressure from the low-pressure fuel pump 4 is set to a set pressure (for example, 0.33) between the supply path 3A and the return path 3B of the fuel passage 3.
(MPa).

A high-pressure regulator 14 is provided downstream of the injector 1.
Numeral 4 is for adjusting the discharge pressure from the high-pressure fuel pump 5 to a set pressure (for example, 5 MPa). Since the discharge flow rate from the high-pressure fuel pump 5 increases as the engine speed increases, even if the pressure is adjusted by the high-pressure regulator 14, the fuel pressure tends to increase slightly as the engine speed increases.

A bypass passage 11 is provided so that fuel can be supplied to the injector 1 by bypassing the high-pressure fuel pump 5. Further, the bypass passage 11 is provided with a check valve 12 that allows fuel to pass only from the upstream side to the downstream side of the feed path 3A. Further, a bypass passage 13 is provided so that the fuel in the injector 1 can be discharged to the fuel tank 2 by bypassing the high-pressure regulator 14.
An electromagnetic switching valve 9 is provided. The electromagnetic switching valve 9 opens when the engine starts, and closes after the engine starts.

Immediately after the start of the engine, even if the return passage 3B is open, a pressure close to the set pressure controlled by the low-pressure regulator 8 is provided immediately downstream of the electromagnetic switching valve 9 in the return passage 3B of the fuel passage 3. Fixed throttle 1 for obtaining fuel pressure
0 is provided. With such a configuration, the fuel in the fuel tank 2 is supplied to the low-pressure fuel pump (feed pump) 4.
The pressure is adjusted to a predetermined low pressure value by the downstream low pressure regulator 8, supplied to the injector 1, and the surplus fuel is returned to the fuel tank 2. Low pressure fuel pump 4
Immediately after the start, a discharge pressure state of a predetermined pressure (several atmospheric pressures) is obtained. However, immediately after the start of the engine, the rotation of the engine does not increase, so that the high-pressure fuel pump 5 does not generate a sufficient discharge pressure.

For this reason, immediately after the start of the engine, the high-pressure fuel pump 5 causes the resistance of the flow of the fuel flow in the fuel passage 3 due to the discharge pressure from the low-pressure fuel pump 4. Since fuel is supplied to the fuel injection valve 1 through the bypass passage 11 provided in parallel with the pump 5, the fuel can be injected from the fuel injection valve 1 at a fuel pressure approximately equal to the pressure adjusted by the low-pressure regulator 8. You.

Then, as the engine speed increases, the discharge flow rate of the high-pressure fuel pump 5 increases, and the discharge pressure of the high-pressure fuel pump 5 also smoothly increases. The valve 9 is closed, and the drive of the fuel injection valve 1 is controlled in a high-pressure mode (that is, a mode during normal operation). That is, the injector gain or the like in the high pressure mode is selected.

As a result, the fuel discharged from the low-pressure fuel pump 4 and pressurized to a high pressure by the high-pressure fuel pump 5 and regulated to a predetermined high pressure value by the high-pressure regulator 14 is supplied to the injector 1 and surplus. Fuel is fuel tank 2
Is returned to. As a result, the discharge pressure of the high-pressure fuel pump 5 is increased without any loss, and the fuel pressure on the downstream side of the high-pressure fuel pump 5 is increased. In addition, since the injector gain or the like in the high-pressure mode is selected, fuel injection can be performed appropriately.

Thus, the discharge pressure of the high-pressure fuel pump 5 rises to a sufficient level, so that fuel can be injected from the fuel injection valve 1 at a fuel pressure as high as the adjustment pressure of the high-pressure regulator 14, and immediately after the engine is started. For example, in an in-cylinder injection type internal combustion engine, it is required to perform the fuel injection during the compression stroke of the engine, or the fuel injection period (that is, the pulse width of the fuel injection) is gradually increased. A high fuel injection pressure required for shortening can be obtained.

The electromagnetic switching valve 9 for opening and closing the return passage 3B of the fuel passage 3 is closed after a predetermined period (relatively short time) has elapsed since the engine was started and the vapor was sufficiently discharged. Therefore, thereafter, the fuel pressure can be increased to the pressure controlled by the high-pressure regulator 9, and a sufficiently high fuel injection pressure can be obtained.

As a technique for supplying the fuel pressurized by the fuel pump to the fuel injection valve, there is another technique disclosed in, for example, Japanese Utility Model Laid-Open No. 59-65945 (second prior art). . In this technique, means for variably controlling the fuel supply pressure to the fuel injection valve according to the operating state of the engine at the time of idling and at the time of operation other than idling,
That is, a variable pressure regulator is provided so that the fuel supply pressure during idling is reduced as compared with the operation during operations other than idling.

For example, Japanese Patent Application Laid-Open No. 3-74569 (third prior art) discloses a technique relating to fuel injection control in a direct injection internal combustion engine. In this technique, a plurality of return passages that bypass a fuel injection pump via a switching valve are provided in a high-pressure fuel passage that supplies fuel from a fuel pump driven by an engine to an injector, and a rotation speed sensor and an accelerator opening of the engine are provided. By switching the switching valve by the control unit based on the signal from the degree sensor, the fuel pressure of the fuel discharged from the fuel pump can be changed in a plurality of stages according to the load of the engine, that is,
It is controlled to the high pressure side and the low pressure side.

Further, Japanese Patent Application Laid-Open No. 4-86351 (fourth prior art) discloses that when fuel is injected from an electromagnetic injection valve in synchronization with a suction stroke of a cylinder, the fuel varies according to a change in engine operating conditions. The opening time of the injection valve is determined so that the fuel injection time is proportional to the fresh air inflow time, and the fuel pressure is adjusted so that a predetermined amount of fuel is injected during the opening time, and the fuel is passed in front of the injection valve. A technique for injecting fuel over the entire intake fresh air is disclosed.

Japanese Utility Model Laid-Open Publication No. 63-75544 (Fifth Prior Art) discloses a pressure regulator setting for controlling fuel pressure in accordance with intake pipe pressure during lean burn control for burning in a lean air-fuel ratio region. A technique is disclosed in which the fuel pressure supplied to the fuel injection valve is reduced by a predetermined pressure by reducing the pressure, and the fuel injection time from the fuel injection valve is corrected so as to be longer according to the fuel pressure reduction amount.

[0023]

By the way, in an in-cylinder injection system engine, in order to achieve super lean burn by a partial lean combustion system in order to improve fuel efficiency,
The fuel pressure is increased to 5 MPa during the compression stroke, and the fuel is injected.
(0 rpm or more), it is considered that the fuel economy gain is small.

For example, FIG. 9 shows a fuel efficiency improvement rate of lean burn in a compression stroke. FIG. 9A shows a fuel pressure of 5 MPa.
And (b) is a case where the fuel pressure is 7 MPa.
In each of (a) and (b), the vertical axis represents the net effective pressure Pe, and the horizontal axis represents the engine speed. In FIG. 9, the bold line A indicates the fuel efficiency improvement rate, and the unit of the fuel efficiency improvement rate is%.

According to FIG. 9, when the fuel pressure is increased to 7 MPa, the fuel efficiency improvement rate is higher on the higher rotation speed side, and the output is also improved. Therefore, it is conceivable to improve the fuel efficiency and output by increasing the fuel pressure. However, when the fuel pressure is increased, the ratio of the burden on the engine by the high-pressure fuel pump 5 is increased when the engine is running at a low speed including an idle time and when the engine is under a low load, so that the fuel efficiency is rather deteriorated.

Also, when the engine is running at a low speed, particularly at idle, the fuel flow rate of the engine-driven pump decreases, and when the pressure adjusted by the high-pressure regulator 14 is increased, the lift amount of the valve decreases, and the valve lift is reduced. There is a problem that dust or the like may be generated in the high-pressure regulator 14 because the passage that extends is not expanded.

Further, in the case of a direct injection engine, although it is used because of the installation space and the like, the injector 1 may be directly attached to the cylinder head 24. In this case, silencing by an insulator or the like can be expected. In particular, if the fuel pressure is increased during idling, the injector 1
However, there is a problem that the driving noise increases. By the way, in the above-mentioned second prior art, a variable pressure regulator is used for controlling the fuel supply pressure, and a diaphragm is used for the variable pressure regulator. For example, when it is necessary to increase the fuel pressure as in a cylinder injection engine, there is a problem in terms of the durability of the diaphragm.

The third prior art discloses a technique for controlling a fuel pressure using a high-pressure side regulator and a low-pressure side regulator in a fuel injection control device employed in a two-cycle engine. It only discloses controlling the fuel pressure in order to adjust the fuel injection amount at the time of high rotation, but does not disclose improving torque while controlling fuel pressure to improve fuel economy. However, since no measures are taken at the time of starting the engine, there is a problem that it is difficult to perform control according to a request.

In the fourth prior art, the fuel pressure is adjusted so that a predetermined amount of fuel is injected within the valve opening time. As a method, the discharge amount of the fuel pump is adjusted based on the rotation speed of the engine. It is described that the fuel pressure is variable or the characteristics of the fuel pressure regulator are variable. However, there is no disclosure of any specific means by which the fuel pressure can be adjusted.

In the fifth prior art, a variable pressure regulator is used for controlling the fuel supply pressure in normal fuel injection other than in-cylinder fuel injection, and a diaphragm is used for the variable pressure regulator. When it is necessary to increase the fuel pressure as in a direct injection engine, there is a problem in terms of the durability of the diaphragm.

The present invention has been made in view of the above-described problems, and has sufficient durability, and can control switching of fuel pressure in accordance with engine speed, thereby improving fuel efficiency and output at high engine speed. On the other hand, it is an object of the present invention to provide a fuel supply device for an internal combustion engine, which is capable of suppressing injector driving noise during low rotation.

[0032]

According to a first aspect of the present invention, a fuel supply device for an internal combustion engine is provided between a fuel injection valve provided in an internal combustion engine and a fuel tank. From the fuel injection valve to the fuel tank and back to the fuel tank from the fuel injection valve, and a fuel passage provided upstream of the fuel injection valve in the fuel passage and driven by the internal combustion engine. A high-pressure fuel pump, first high-pressure control means provided in a fuel passage portion on the downstream side of the high-pressure fuel pump to control fuel pressure discharged from the high-pressure fuel pump, and a first high-pressure control means bypassing the first high-pressure control means. A first fuel pressure switching valve provided in the first bypass passage portion for opening and closing the first bypass passage in accordance with an engine operating state; a first high pressure control means; and a fuel passage portion downstream of the first bypass passage portion Provided, the second high pressure control means for controlling the fuel pressure discharged from the high-pressure fuel pump,
A second fuel pressure switching valve is provided in a second bypass passage that bypasses the second high-pressure control means, and opens and closes the second bypass passage in accordance with an engine operating state.

A fuel supply device for an internal combustion engine according to the present invention is provided between a fuel injection valve provided in the internal combustion engine and a fuel tank, and further extends from the fuel tank to the fuel injection valve. A fuel passage configured as a circulation circuit returning from the fuel injection valve to the fuel tank again, a high-pressure fuel pump provided in the fuel passage upstream of the fuel injection valve and driven by the internal combustion engine, and the high-pressure fuel pump A first high-pressure control means provided in a fuel passage portion on the downstream side of the high-pressure fuel pump to control fuel pressure discharged from the high-pressure fuel pump; and a first high-pressure control means provided in a first bypass passage portion bypassing the first high-pressure control means. A first fuel pressure switching valve that opens and closes the first bypass passage in accordance with an engine operating state; and a first high pressure control unit and a second bypass passage that bypasses the first bypass passage. A second high-pressure control means for controlling the pressure of the fuel discharged from the fuel pump; and a second high-pressure control means provided in the second bypass passage portion in series with the second high-pressure control means for opening and closing the second bypass passage in accordance with an engine operating state. And a second fuel pressure switching valve.

According to a third aspect of the present invention, there is provided a fuel supply device for an internal combustion engine provided between a fuel injection valve provided in the internal combustion engine and a fuel tank. The fuel supply device extends from the fuel tank to the fuel injection valve. A fuel passage configured as a circulation circuit returning from the fuel injection valve to the fuel tank again, a high-pressure fuel pump provided in the fuel passage upstream of the fuel injection valve and driven by the internal combustion engine, and the high-pressure fuel pump A first high-pressure control means provided in a fuel passage portion on the downstream side of the high-pressure fuel pump to control a fuel pressure discharged from the high-pressure fuel pump; and a first high-pressure control means provided in a fuel passage portion on the downstream side of the first high-pressure control means. A second high-pressure control means for controlling the fuel pressure discharged from the fuel pump to a pressure higher than the pressure regulated by the first high-pressure control means, the first high-pressure control means and the second high-pressure control means;
A fuel pressure switching valve that is provided in a first bypass passage that bypasses the high-pressure control means, and that opens and closes the first bypass passage in accordance with an engine operating state, and is provided in a second bypass passage that bypasses the first high-pressure control means. It is characterized by having a given aperture.

According to a fourth aspect of the present invention, there is provided a fuel supply device for an internal combustion engine provided between a fuel injection valve provided in the internal combustion engine and a fuel tank. A fuel passage configured as a circulation circuit returning from the fuel injection valve to the fuel tank again, a high-pressure fuel pump provided in the fuel passage upstream of the fuel injection valve and driven by the internal combustion engine, and the high-pressure fuel pump A first high-pressure control means provided in a fuel passage portion on the downstream side of the high-pressure fuel pump to control a fuel pressure discharged from the high-pressure fuel pump; and a first high-pressure control means provided in a fuel passage portion on the downstream side of the first high-pressure control means. A second high-pressure control means for controlling the fuel pressure discharged from the fuel pump to a pressure lower than the pressure regulated by the first high-pressure control means; and the first high-pressure control means and the second high-pressure control means.
A fuel pressure switching valve that is provided in a first bypass passage that bypasses the high-pressure control means, and that opens and closes the first bypass passage in accordance with an engine operating state, and is provided in a second bypass passage that bypasses the second high-pressure control means. It is characterized by having a given aperture.

According to a fifth aspect of the present invention, there is provided a fuel supply system for an internal combustion engine according to any one of the first to fourth aspects, further comprising: a low-pressure fuel pump provided upstream of the high-pressure fuel pump; A low-pressure control means is provided in a fuel passage portion on the downstream side of the low-pressure fuel pump and controls the fuel pressure discharged from the low-pressure fuel pump.

[0037]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram showing a fuel supply device for an internal combustion engine according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a fuel injection valve, 2 denotes a fuel tank, 3 denotes a fuel passage, 4 denotes a low-pressure fuel pump provided upstream of the fuel passage 3 on the fuel tank 2 side, and 5 denotes a low-pressure fuel pump and a fuel pump. This is a high-pressure fuel pump provided between the fuel injector and the injection valve 1. Reference numeral 6 denotes a fuel filter provided at the inlet of the fuel passage; 7, 12, 51, a check valve; 8, a low-pressure regulator as low-pressure control means; 9, 56, an electromagnetic switching valve (fuel pressure switching valve); , 50, 53 are throttles (orifices) as a fuel pressure holding mechanism, and 14, 57 are high pressure regulators as high pressure control means.

As shown in FIG. 1, a fuel passage 3 communicating between the injector 1 and the fuel tank 2 is provided with a low-pressure fuel pump 4 and a high-pressure fuel pump 5. The fuel passage 3 includes a supply path 3A for supplying fuel from the fuel tank 2 to the injector 1, and a return path 3B for returning fuel not injected by the injector 1 to the fuel tank 2. Further, the injector 1 is supplied with fuel through the delivery pipe 1A. Here, the delivery pipe 1A itself is considered as a part of the fuel passage 3.

Note that the configuration of the main part of the internal combustion engine having the present fuel supply device is almost the same as that of the prior art (see FIG. 7), and the description is omitted here. The operation of the injector 1 is computer-controlled so that a required fuel injection amount can be obtained at a required timing according to an engine speed, an intake air amount, and the like. The fuel injection amount is set by a pulse width of a pulse current for driving the injector, and the pulse width is set as an injector gain corresponding to a target fuel injection amount.

The low-pressure fuel pump 4 is an electric feed pump provided in the fuel tank 2 upstream of the feed passage 3 A of the fuel passage 3. Is driven downstream of the feed path 3A. At this time, the fuel is pressurized by the low-pressure fuel pump 4 from the state of the atmospheric pressure to about several atmospheric pressures. The low-pressure fuel pump 4 starts at the same time as the start of the engine and stops when the engine stops, but can generate a predetermined discharge pressure without depending on the rotation speed of the engine.

The high-pressure fuel pump 5 pressurizes the fuel discharged from the low-pressure fuel pump 4 to about several tens of atmospheres. The check valve 7 is interposed, and the discharge pressure of the low-pressure fuel pump 4 is maintained by the check valve 7.
The high-pressure fuel pump 5 uses an engine-driven pump (hereinafter, referred to as an engine-driven pump) such as a reciprocating compression pump which is more advantageous than the electric pump as the high-pressure pump in terms of pump efficiency and cost. , Of course,
It operates directly in conjunction with the operation of the engine, and generates discharge pressure according to the rotation speed of the engine.

High-pressure fuel pump 5 in supply passage 3A of the fuel passage
A check valve 51 is provided on the downstream side of. Further, between the feed path 3A and the return path 3B of the fuel passage 3, that is, the portion of the feed path 3A downstream of the check valve 7 on the upstream side of the high-pressure fuel pump 5 and the return path 3B. The discharge pressure from the low-pressure fuel pump 4 is set to a set pressure (for example, 0.33
(MPa). The low-pressure regulator 8 is closed until the discharge pressure from the low-pressure fuel pump 4 exceeds a set pressure (for example, 0.33 MPa). When the discharge pressure exceeds the set pressure, the fuel corresponding to the pressure exceeds the set pressure. By directly returning the fuel to the fuel tank 2, the pressure of the fuel supplied to the high-pressure fuel pump 5 is stabilized near the set pressure. Of course, in order to obtain the above set pressure, the low-pressure fuel pump 4
The discharge pressure is set to be equal to or higher than the set pressure.

Further, a high-pressure regulator (second high-pressure control means) 14 is provided downstream of the injector 1, that is, in the return path 3B of the fuel passage 3. The high-pressure regulator 14 is closed until the discharge pressure from the high-pressure fuel pump 5 exceeds the set pressure, and when the discharge pressure exceeds the set pressure, the fuel tank 2 removes the fuel for the excess pressure.
And the fuel pressure in the injector 1 is stabilized at a predetermined pressure. Here, the set pressure is generally 5 MPa in consideration of combustion stability and fuel efficiency of partial lean combustion.
(That is, about 50 atm). The high-pressure fuel pump is driven by the engine, and the regulator tends to increase the fuel pressure as the engine rotates at a higher speed. A throttle 53 is provided downstream of the high-pressure regulator 14 as a fuel pressure holding mechanism. The throttle 53 is a fixed throttle in which the inner diameter of the fuel passage 3 is merely reduced.

The upstream part and the downstream part of the high pressure fuel pump 5 are connected so that the fuel passing through the supply path 3A of the fuel passage 3 can be supplied to the injector 1 bypassing the high pressure fuel pump 5. A bypass passage 11 is provided. The bypass passage 11 is provided with a check valve 12 that allows fuel to pass only from the upstream side to the downstream side of the feed path 3A. This check valve 12 opens the bypass passage 11 when the high-pressure fuel pump 5 does not operate sufficiently and the fuel pressure is lower on the downstream side than on the upstream side of the high-pressure fuel pump 5, and the high-pressure fuel pump 5 is turned off. If the fuel pressure is higher on the downstream side of the high-pressure fuel pump 5 than on the upstream side,
The bypass passage 11 is closed.

A throttle 50 as a fuel pressure holding mechanism is provided between the bypass passage 11 and the high-pressure fuel pump 5. The throttle 50 is a fixed throttle that only reduces the inner diameter of the fuel passage 3. Further, a bypass passage connecting the upstream and downstream portions of the high-pressure regulator 14 and the fixed throttle 53 so that the fuel in the injector 1 can be discharged to the fuel tank 2 bypassing the high-pressure regulator 14. (Second bypass passage) 13 is provided. The bypass passage 13 has an electromagnetic switching valve (second fuel pressure switching valve) 9 for adjusting the discharge pressure from the high-pressure fuel pump 5 to a set pressure, and a throttle 10 as a fuel pressure holding mechanism.
Is provided.

The solenoid-operated directional control valve 9 opens the return line 3B when the power is received, and opens the return line 3B when the power is stopped.
B is closed, and the opening and closing of the electromagnetic switching valve 9 is controlled by a controller (not shown). This controller controls the electromagnetic switching valve 9 to be opened when the engine is started, and to be closed in the normal operation state (after starting). Here, the start of the engine is defined as a period from the time when the start operation mode is started by the input of the ignition key switch to the time when a predetermined time (for example, 2 seconds) elapses after the start operation mode ends. On the other hand, the normal operation state is after elapse of the predetermined time. Here, even when the engine is stopped, the electromagnetic switching valve 9 is closed.

The throttle 10 as a fuel pressure holding mechanism is provided in the return passage 3 B of the fuel passage 3 immediately downstream of the electromagnetic switching valve 9. This throttle 10 is used immediately after the engine is started.
Even if the return path 3B is open, this is for obtaining a fuel pressure at least close to the set pressure controlled by the low-pressure regulator 8, and here, the inner diameter of the fuel passage 3 is merely reduced. It has a fixed aperture.

Next, an additional device which is a feature of the present apparatus will be described. This additional device is additionally connected to the return passage 3B of the fuel passage 3 immediately downstream of the fuel injection valve 1, and includes a high-pressure regulator (first high-pressure control device).
Step) 57 and bypass passage (first bypass passage) 55
And an electromagnetic switching valve (first fuel pressure switching valve) 56 provided in the bypass passage 55.

The high-pressure regulator 57 is connected to the injector 1
, That is, in the return path 3B of the fuel passage 3. The high-pressure regulator 14 is closed until the discharge pressure from the high-pressure fuel pump 5 exceeds a set pressure.
When the discharge pressure exceeds the set pressure, the fuel corresponding to the excess pressure is caused to flow downstream, so that the fuel pressure in the injector 1 is stabilized at a predetermined pressure.
Here, the set pressure is set to 2 MPa.

The bypass passage (first bypass passage) 55 is provided between the upstream part of the high-pressure regulator 57 and the downstream part so that the fuel in the injector 1 can be discharged to the downstream side by bypassing the high-pressure regulator 57. Connect the side parts. Electromagnetic switching valve (first fuel pressure switching valve) 56
Is provided in the bypass passage 55, and is configured substantially in the same manner as the electromagnetic switching valve 9, and adjusts the discharge pressure from the high-pressure fuel pump 5 to a set pressure. That is, the electromagnetic switching valve 56 is configured to open the return path 3B at the time of operation receiving electric power, and to close the return path 3B at the time of stoppage of the power supply, and the electromagnetic switching valve 56 is controlled by a controller (not shown). The opening / closing of 56 is controlled. In this controller, the electromagnetic switching valve 56 is opened when the engine is started, and a normal operation state (after the start) is performed.
Controls the electromagnetic switching valve 56 to be closed.

Immediately after the start, the controller performs control in a start mode. When the start mode is completed, the controller controls the fuel pressure to 5 MPa using only the high-pressure regulator 14 (a second high-pressure mode described later). Lower pressure mode), and the high pressure regulator 14
And the high pressure regulator 57 at the same time to reduce the fuel pressure to 7
The mode is switched to one of a second high-pressure mode for adjusting the pressure to MPa (hereinafter referred to as a high-pressure mode because the pressure is higher than the first high-pressure mode).

In the low-pressure mode, the electromagnetic switching valve 9 is closed and the electromagnetic switching valve 56 is opened, whereby the pressure is regulated (5 MPa) by the high-pressure regulator 14. In the high-pressure mode, both the electromagnetic switching valves 9 and 56 are connected. Close it,
The pressure adjustment (2 MPa) of the pressure adjustment (2 MPa) by the high-pressure regulator 57 and the pressure adjustment (5 MPa) by the high-pressure regulator 14 are performed.

The switching between the low pressure mode and the high pressure mode is performed based on the engine speed. If the engine speed is equal to or less than a predetermined speed (for example, 2500 rpm), the low pressure mode is set and the engine speed is set to the predetermined speed (2500 rpm).
m) or more, the high pressure mode is set. In the controller, regarding the injector gain, in the low pressure mode,
The fuel pressure (5 MPa) is selected and the fuel pressure (5 MPa) is selected (low pressure injector gain). In the high pressure mode, the fuel pressure (7 MPa) is selected and the fuel pressure (high pressure injector gain) is selected. Control.

Since the apparatus of this embodiment is configured as described above, the fuel supply control is performed as follows. That is, referring to FIG. 1, in this device, when the engine starts,
The low-pressure fuel pump 4 and the high-pressure fuel pump 5 also start,
At the same time, the controller opens the electromagnetic switching valve 9 and also opens the electromagnetic switching valve 56 in the additional device, and controls the driving of the fuel injection valve 1 in the engine start mode. That is, the injector gain in the engine start mode is selected. In this case, the fuel is discharged from the low-pressure fuel pump 4,
A predetermined low pressure value (0.33M
The fuel whose pressure has been adjusted to Pa) is supplied to the injector 1, and the surplus fuel is returned to the fuel tank.

Immediately after the start of the engine, the discharge pressure of the high-pressure fuel pump 5 does not immediately rise, and instead, the fuel passage 3
Although the discharge pressure from the low-pressure fuel pump 4 is not sufficiently exerted due to the resistance of the flow of the fuel flow in the inside, in the present device, the fuel injection is performed through the bypass passage 11 provided in parallel with the high-pressure fuel pump 5. Since fuel is supplied to the valve 1 side, fuel injection can be performed from the fuel injection valve 1 at a fuel pressure of about 0.33 MPa adjusted by the low pressure regulator 8.

In general, immediately after the start of the engine, the amount of fuel required for combustion is small, the pulse width of the fuel injection is short, and the pulse timing of the fuel injection is the same as in the conventional multipoint injection (MPI). Only during the intake stroke is sufficient, and accordingly, the injector gain in the engine start mode is selected and fuel injection is performed. Therefore, even if the fuel pressure is about the adjustment pressure level of the low-pressure regulator 8, If the fuel pressure is stable, the rotation of the engine can be smoothly increased.

Thereafter, after a predetermined time has elapsed after the start of the engine and the vapor has been sufficiently discharged, the controller always closes the electromagnetic switching valve 9. After that, the electromagnetic switching valve 56 and the like of the additional device are controlled to open and close according to the engine speed. For example, if the engine speed is equal to or lower than a predetermined speed (2500 rpm), the electromagnetic switching valve 56 is opened and the fuel injection valve 1 is drive-controlled in the low pressure mode (idle mode) of the normal operation mode. That is, the low-pressure injector gain is selected. In this case, the fuel pressure is adjusted by the high-pressure regulator 14, and the discharge pressure of the high-pressure fuel pump 5 works effectively. That is, the fuel is discharged from the low-pressure fuel pump 4 and is pressurized to a high pressure by the high-pressure fuel pump 5, and a predetermined high pressure value (5
The fuel whose pressure has been adjusted to MPa) is supplied to the fuel injection valve 1, and the surplus fuel is returned to the fuel tank 2.

Further, when the engine speed reaches a predetermined speed (2
If it becomes higher than 500 rpm), the controller closes the electromagnetic switching valve 9 and closes the electromagnetic switching valve 56 in the additional device. The drive of the fuel injection valve 1 is controlled in a high-pressure mode (a mode other than the idle mode).
That is, the high-pressure injector gain is selected. The fuel is discharged from the low-pressure fuel pump 4 and pressurized to a high pressure by the high-pressure fuel pump 5, and at a predetermined pressure value (7) by the high-pressure regulator 57 and the high-pressure regulator 14 in the additional device.
The fuel whose pressure has been adjusted to MPa) is supplied to the fuel injection valve 1, and the surplus fuel is returned to the fuel tank 2.

Therefore, except during idle time, fuel efficiency and output can be improved at a high fuel pressure (7 MPa) in the high pressure mode. At the time of idling, there is an advantage that an increase in injector driving noise can be prevented at a relatively low fuel pressure (5 MPa) in the low pressure mode.
At idle, the engine speed is low and the fuel flow rate is low.
The lift amount is small and there is a risk of dust
Since the fuel pressure is relatively low at the time of idling in the present apparatus, there is an advantage that it is possible to prevent dust or the like caused by a low flow rate.

When the fuel pressure is switched, the fuel injection amount must be corrected depending on the fuel pressure behavior.
It has been confirmed that the present apparatus has few problems such as torque shock and the like and can smoothly increase or decrease the torque without performing the injection amount correction in such a case. Further, in the device of the first embodiment, the electromagnetic switching valves 9 and 56 are closed in the high-pressure mode (other than at the time of idling), which is the normal use mode of the engine (that is, the state in which no current flows). This has the advantage of being economical due to low power consumption. In addition, since a simple configuration in which an additional device is connected to a normally used device is provided, there is an advantage that the device can be easily improved.

When the solenoid-operated switching valve 56 fails (for example, when the solenoid-operated switching valve 56 does not move while being closed), the fuel pressure at the start becomes 2 MPa, but the difference is 0.33 MPa from the normal fuel pressure. Small and therefore 0.33 MPa
Therefore, even if the injector 1 is opened, the engine cannot be started. Further, when the electromagnetic switching valve 9 breaks down (for example, when the electromagnetic switching valve 9 stops moving and remains closed), the starting fuel pressure becomes 5 MPa, and 0.33 MPa.
When the injector 1 is opened with the intention of opening the valve, a large amount of fuel is supplied, so that the engine cannot be started in this state. However, since the throttle can be opened and a large amount of air can be taken in to achieve a flammable air-fuel ratio, the apparatus can be started. Reliability can be improved.

Next, a modification of the first embodiment will be described. FIG. 2 schematically shows the configuration of an apparatus according to a modification of the first embodiment. As shown in FIG. 2, the apparatus according to the modification of the first embodiment includes an apparatus according to the first embodiment and a high-pressure regulator (set pressure 2 MPa) 5 in an additional device.
7 instead of the high pressure regulator (set pressure 7 MPa) 59
Is used. The rest of the configuration is the same as in the first embodiment.

The high-pressure regulator 59 adjusts the discharge pressure from the high-pressure fuel pump 5 to a set pressure (7 MPa).
If the discharge pressure exceeds the set pressure, the fuel pressure in the fuel injection valve 1 is stabilized at a predetermined pressure by flowing the fuel for the excess pressure to the downstream portion. It has become.

Immediately after starting, the controller performs control in a start mode, and when the start mode is completed, a first high pressure mode (a second high pressure mode described later) in which the fuel pressure is adjusted to 5 MPa only by the high pressure regulator 14 is performed. Lower pressure mode), and a high pressure regulator 59.
The mode is switched to one of a second high-pressure mode in which the fuel pressure is adjusted to 7 MPa using only the pressure (the pressure is higher than the first high-pressure mode, and is referred to as a high-pressure mode).

In the low pressure mode, the electromagnetic switching valve 9 is closed and the electromagnetic switching valve 56 is opened, whereby the pressure is adjusted (5 MPa) by the high pressure regulator 14. In the high pressure mode, the electromagnetic switching valve 9 is opened. Solenoid switching valve 56
Is closed, and the pressure is adjusted by the high-pressure regulator 59 (7).
MPa). This low pressure mode,
The switching of the high pressure mode is performed based on the engine speed, and the engine speed is changed to a predetermined speed (for example, 2500 rpm).
pm) or less, the mode is set to the low pressure mode.

In the controller, the fuel pressure (5M
Pa) and the fuel pressure (7 MPa) that is appropriate for the fuel pressure (7 MPa) in the high pressure mode.
Each controls the driving of the injector.

Since the device of this modification is configured as described above, the fuel supply control is performed as follows. That is, FIG.
Referring to FIG. 1, in the present apparatus, when the engine is started, the low-pressure fuel pump 4 and the high-pressure fuel pump 5 are also started. At the same time, the controller opens the electromagnetic switching valve 9 and simultaneously operates the electromagnetic switching valve 56 in the additional device. Is also opened, and the drive of the fuel injection valve 1 is controlled in the engine start mode. That is, the injector gain in the engine start mode is selected. In this case, the fuel is discharged from the low-pressure fuel pump 4,
Fuel adjusted to a predetermined low pressure value by the downstream low pressure regulator 8 is supplied to the injector 1, and surplus fuel is returned to the fuel tank.

Immediately after the start of the engine, the discharge pressure of the high-pressure fuel pump 5 does not immediately rise, and instead, the fuel passage 3
Although the discharge pressure from the low-pressure fuel pump 4 is not sufficiently exerted due to the resistance of the flow of the fuel flow in the inside, in the present device, the fuel injection is performed through the bypass passage 11 provided in parallel with the high-pressure fuel pump 5. Since fuel is supplied to the valve 1 side, fuel injection can be performed from the fuel injection valve 1 at a fuel pressure of about 0.33 MPa adjusted by the low pressure regulator 8.

In general, immediately after the start of the engine, the amount of fuel required for combustion is small, so that the pulse width of the fuel injection is short, and the pulse timing of the fuel injection is the same as in the conventional multipoint injection (MPI). Only during the intake stroke is sufficient, and accordingly, the injector gain in the engine start mode is selected and fuel injection is performed. Therefore, even if the fuel pressure is about the adjustment pressure level of the low-pressure regulator 8, If the fuel pressure is stable, the rotation of the engine can be smoothly increased.

Thereafter, after a predetermined time has elapsed since the start of the engine, and after the vapor has been sufficiently discharged, the controller always closes one of the electromagnetic switching valves 9 and 56. These electromagnetic switching valves 9 and 56 are controlled to open and close according to the engine speed. For example, if the engine speed is equal to or less than a predetermined speed (2500 rpm), the electromagnetic switching valve 9
Is closed, the electromagnetic switching valve 56 is opened, and the drive of the fuel injection valve 1 is controlled in the low pressure mode (idle mode) in the normal operation mode. That is, the low-pressure injector gain is selected. In this case, the fuel pressure is adjusted by the high-pressure regulator 14, and the discharge pressure of the high-pressure fuel pump 5 works effectively. That is, fuel discharged from the low-pressure fuel pump 4 and pressurized to a high pressure by the high-pressure fuel pump 5 and regulated to a predetermined high pressure value (5 MPa) by the high-pressure regulator 14 is supplied to the fuel injection valve 1, The returned fuel is returned to the fuel tank 2.

Further, when the engine speed is equal to the predetermined speed (2
If it becomes higher than 500 rpm), the controller opens the electromagnetic switching valve 9 and closes the electromagnetic switching valve 56 in the additional device. The drive of the fuel injection valve 1 is controlled in a high-pressure mode (a mode other than the idle mode).
That is, the high-pressure injector gain is selected. Fuel discharged from the low-pressure fuel pump 4 and pressurized to a high pressure by the high-pressure fuel pump 5 and regulated to a predetermined pressure value (7 MPa) by the high-pressure regulator 59 in the additional device is supplied to the fuel injection valve 1. Excess fuel is returned to the fuel tank 2.

Therefore, the fuel consumption and the output can be improved at a high fuel pressure (7 MPa) in the high pressure mode except during the idling time. At the time of idling, there is an advantage that an increase in injector driving noise can be prevented at a relatively low fuel pressure (5 MPa) in the low pressure mode.
At idle, the engine speed is low and the fuel flow rate is low.
The lift amount is small and there is a risk of dust
Since the fuel pressure is relatively low at the time of idling in the present apparatus, there is an advantage that it is possible to prevent dust or the like caused by a low flow rate.

When the fuel pressure is switched, the fuel injection amount must be corrected depending on the fuel pressure behavior.
It has been confirmed that the present apparatus has few problems such as torque shock and the like and can smoothly increase or decrease the torque without performing the injection amount correction in such a case. In addition, since a simple configuration in which an additional device is connected to a normally used device is provided, there is an advantage that the device can be easily improved.

Next, a second embodiment will be described. FIG. 3 schematically shows the configuration of the device of the second embodiment. As shown in FIG. 3, the apparatus according to the present embodiment differs from the apparatus according to the first embodiment in the connection configuration of the additional device and the high-pressure regulator. That is, the high pressure regulator (set pressure 5
High pressure regulator (set pressure 7M)
Pa) 59 and the additional device is bypassed
(1st bypass passage) As 13 and 1st high pressure control means
Are connected in parallel to the high-pressure regulator 59 . In addition,
Other configurations are the same as those of the first embodiment.

The additional device includes a bypass passage (second bypass passage) 60, an electromagnetic switching valve 56, and a high-pressure regulator (second high-pressure control valve) 14. 14 are arranged in series. That is, in the apparatus of the present embodiment, the high-pressure regulator 14 that can regulate the pressure to 5 MPa is used as the high-pressure regulator of the additional device, and the high-pressure regulator 59 that can regulate the pressure to 7 MPa is used as the high-pressure regulator in the second bypass passage. The configurations of the electromagnetic switching valve 56 and the high-pressure regulator 14 are the same as those of the device of the first embodiment.

Immediately after the start, the controller performs control in a start mode. When the start mode is completed, the controller controls the fuel pressure to 5 MPa only by the high pressure regulator 14 (a second high pressure mode described later). Lower pressure mode), and the high pressure regulator 57
The mode is switched to any one of a second high-pressure mode in which the fuel pressure is adjusted to 7 MPa using only the pressure (the pressure is higher than the first high-pressure mode, and is referred to as a high-pressure mode).

In the low-pressure mode, the electromagnetic switching valve 9 is closed and the electromagnetic switching valve 56 is opened, whereby the pressure is adjusted (5 MPa) by the high-pressure regulator 14. In the high-pressure mode, both the electromagnetic switching valves 9 and 56 are connected. Close it,
Pressure adjustment by high pressure regulator 57 only (7MPa)
Is to be performed. The switching between the low pressure mode and the high pressure mode is performed based on the engine speed. If the engine speed is equal to or lower than a predetermined speed (for example, 2500 rpm), the mode is set to the low pressure mode, and if the engine speed is equal to or higher than the predetermined speed (2500 rpm). High-pressure mode is set.

In the controller, the fuel pressure (5M
Pa) and the fuel pressure (7 MPa) that is appropriate for the fuel pressure (7 MPa) in the high pressure mode.
Each controls the driving of the injector.

Since the device of this embodiment is configured as described above, the fuel supply control is performed as follows. That is, referring to FIG. 3, in this device, when the engine starts,
The low-pressure fuel pump 4 and the high-pressure fuel pump 5 also start,
At the same time, the controller opens the electromagnetic switching valve 9 and also opens the electromagnetic switching valve 56 in the additional device, and controls the driving of the fuel injection valve 1 in the engine start mode. That is, the injector gain in the engine start mode is selected. In this case, the fuel is discharged from the low-pressure fuel pump 4,
Fuel adjusted to a predetermined low pressure value by the downstream low pressure regulator 8 is supplied to the injector 1, and surplus fuel is returned to the fuel tank.

Immediately after the start of the engine, the discharge pressure of the high-pressure fuel pump 5 does not immediately rise, and instead, the fuel passage 3
Although the discharge pressure from the low-pressure fuel pump 4 is not sufficiently exerted due to the resistance of the flow of the fuel flow in the inside, in the present device, the fuel injection is performed through the bypass passage 11 provided in parallel with the high-pressure fuel pump 5. Since fuel is supplied to the valve 1 side, fuel injection can be performed from the fuel injection valve 1 at a fuel pressure of about 0.33 MPa adjusted by the low pressure regulator 8.

Generally, immediately after the start of the engine, the amount of fuel required for combustion is small, so that the pulse width of the fuel injection is short, and the pulse timing of the fuel injection is the same as in the conventional multipoint injection (MPI). Only during the intake stroke is sufficient, and accordingly, the injector gain in the engine start mode is selected and fuel injection is performed. Therefore, even if the fuel pressure is about the adjustment pressure level of the low-pressure regulator 8, If the fuel pressure is stable, the rotation of the engine can be smoothly increased.

Thereafter, after a predetermined time has elapsed since the start of the engine and the vapor has been sufficiently discharged, the controller always closes the electromagnetic switching valve 9. After that, the electromagnetic switching valve 56 and the like of the additional device are controlled to open and close according to the engine speed. For example, if the engine speed is equal to or lower than a predetermined speed (2500 rpm), the electromagnetic switching valve 56 is opened and the fuel injection valve 1 is drive-controlled in the low pressure mode (idle mode) of the normal operation mode. That is, the low-pressure injector gain is selected. In this case, the fuel pressure is adjusted by the high-pressure regulator 14, and the discharge pressure of the high-pressure fuel pump 5 works effectively. That is, the fuel is discharged from the low-pressure fuel pump 4 and is pressurized to a high pressure by the high-pressure fuel pump 5, and a predetermined high pressure value (5
The fuel whose pressure has been adjusted to MPa) is supplied to the fuel injection valve 1, and the surplus fuel is returned to the fuel tank 2.

Further, when the engine speed is equal to the predetermined speed (2
500 rpm) or more.
Is closed, and the fuel injection valve 1 is driven and controlled in the high-pressure mode (the mode other than the idle mode) in the normal operation mode. That is, the high-pressure injector gain is selected. The fuel is discharged from the low-pressure fuel pump 4 and pressurized to a high pressure by the high-pressure fuel pump 5.
The fuel adjusted to a predetermined pressure value (7 MPa) by 9 is supplied to the fuel injection valve 1, and the surplus fuel is returned to the fuel tank 2.

Therefore, other than at the time of idling, fuel efficiency and output can be improved at a high fuel pressure (7 MPa) in the high pressure mode. At the time of idling, there is an advantage that an increase in injector driving noise can be prevented at a relatively low fuel pressure (5 MPa) in the low pressure mode.
At idle, the engine speed is low and the fuel flow rate is low.
The lift amount is small and there is a risk of dust
Since the fuel pressure is relatively low at the time of idling in the present apparatus, there is an advantage that it is possible to prevent dust or the like caused by a low flow rate.

When the fuel pressure is switched, the fuel injection amount must be corrected depending on the fuel pressure behavior.
It has been confirmed that the present apparatus has few problems such as torque shock and the like and can smoothly increase or decrease the torque without performing the injection amount correction in such a case. Further, in the device of the second embodiment, the electromagnetic switching valves 9 and 56 are closed in the high-pressure mode (other than at the time of idling), which is the normal use mode of the engine (that is, the state where no current flows). This has the advantage of being economical due to low power consumption. In addition, since a simple configuration in which an additional device is connected to a normally used device is provided, there is an advantage that the device can be easily improved.

When the electromagnetic switching valve 56 is out of order (for example, when the electromagnetic switching valve 56 does not move while being closed), there is no problem since the starting fuel pressure becomes 0.33 MPa. Further, when the electromagnetic switching valve 9 fails (for example,
When the solenoid operated directional control valve 9 stops moving and remains closed),
The starting fuel pressure becomes 5 MPa, and if the injector 1 is opened with the intention of 0.33 MPa, a large amount of fuel is supplied. Therefore, the fuel cannot be started in this state. However, the flammable air is opened by opening the throttle and inhaling a lot of air. Since the fuel can be started at the fuel ratio, the reliability of the device can be improved.

Incidentally, the first and second embodiments were implemented for reasons such as improvement of fuel efficiency of the compression stroke injection at high engine speed (fuel pressure of 7 MPa) and reduction of injector driving noise at low engine speed (idle) (fuel pressure of 5 MPa). As in the form,
Since a switching valve and a high-pressure regulator are required to make the device capable of controlling the fuel pressure, the fuel system (fuel system) becomes complicated, and the control logic becomes complicated. The challenge remains to increase.

The third embodiment described below can solve such a problem. FIG. 4 schematically shows the configuration of the device according to the third embodiment. As shown in FIG. 4, the device of the present embodiment differs from the device of the first embodiment in that a throttle (orifice) 62 is used instead of the electromagnetic switching valve 56. In addition, other
It is configured similarly to the device of the embodiment. The high pressure regulator 14 regulates the fuel pressure to 5 MPa, but may be changed to a regulator that regulates the fuel pressure to 7 MPa.

The switching time constant has a small influence of the rotation and is stable. However, when switching between opening and closing of the electromagnetic switching valve, there is a dead time and there may be individual differences in the regulator. It is preferable to use the fuel pressure sensor 63 for switching the injector gain. Aperture 62
Has an inner diameter of, for example, φ0.4 from the capacity of the high-pressure fuel pump 5 and the required fuel pressure characteristics. The inside diameter of the stop 10 is larger than the stop 62, for example, φ0.8.

The controller performs control in the start mode immediately after the start, and when the start mode is completed, when the engine is running at a low speed, mainly the high pressure regulator 14 is controlled.
Alone, the fuel pressure is adjusted to 5 MPa. However, as the discharge flow rate of the high-pressure fuel pump 5 increases in accordance with the increase in the engine speed, the resistance of the throttle 62 increases, and the upstream side of the throttle 62, that is, The fuel pressure on the injector 1 side is increased, and when the fuel pressure on the injector 1 side reaches 7 MPa, the high-pressure regulator 57 adjusts the fuel pressure on the injector 1 side to 7 MPa while appropriately opening.

Therefore, depending on the engine speed, 5
The fuel pressure is continuously adjusted in the range of MPa to 7 MPa. However, since the resistance of the throttle 62 acts even when the engine is running at a low speed, the substantial control range of the fuel pressure is considered to be about 5.5 to 7 MPa. In the controller, based on the detection information from the fuel pressure sensor 63,
The driving of the injector 1 is controlled by setting an injector gain according to the fuel pressure.

Since the device of this embodiment is configured as described above, the fuel supply control is performed as follows. That is, referring to FIG. 4, in this device, when the engine starts,
The low-pressure fuel pump 4 and the high-pressure fuel pump 5 also start,
At the same time, the controller opens the electromagnetic switching valve 9 and controls the drive of the fuel injection valve 1 in the engine start mode. That is, the injector gain in the engine start mode is selected. In this case, the fuel is discharged from the low-pressure fuel pump 4,
Fuel adjusted to a predetermined low pressure value by the downstream low pressure regulator 8 is supplied to the injector 1, and surplus fuel is returned to the fuel tank.

Immediately after the start of the engine, the discharge pressure of the high-pressure fuel pump 5 does not immediately rise.
Although the discharge pressure from the low-pressure fuel pump 4 is not sufficiently exerted due to the resistance of the flow of the fuel flow in the inside, in the present device, the fuel injection is performed through the bypass passage 11 provided in parallel with the high-pressure fuel pump 5. Since fuel is supplied to the valve 1 side, fuel injection can be performed from the fuel injection valve 1 at a fuel pressure of about 0.33 MPa adjusted by the low pressure regulator 8.

Generally, immediately after the start of the engine, the amount of fuel required for combustion is small, so that the pulse width of the fuel injection is short, and the pulse timing of the fuel injection is the same as in the conventional multipoint injection (MPI). Only during the intake stroke is sufficient, and accordingly, the injector gain in the engine start mode is selected and fuel injection is performed. Therefore, even if the fuel pressure is about the adjustment pressure level of the low-pressure regulator 8, If the fuel pressure is stable, the rotation of the engine can be smoothly increased.

Thereafter, after a predetermined time has elapsed since the start of the engine and the vapor has been sufficiently discharged, the controller always closes the electromagnetic switching valve 9. Thereafter, the fuel pressure is adjusted by the throttle 62 and the high-pressure regulators 14 and 57 according to the engine speed. For example, if the engine speed is low, the throttle 62 does not have a large resistance (for example, about 0.5 MPa), and the fuel pressure is adjusted to about 5.5 MPa. Then, as the engine speed increases, the resistance of the throttle 62 increases, and the fuel pressure increases. Then, when the fuel pressure on the injector 1 side becomes 7 MPa, the high-pressure regulator 57 adjusts the fuel pressure to 7 MPa while appropriately opening it. On the other hand, when the engine speed is equal to or lower than the predetermined speed (2500 rpm), the fuel injector 1 is controlled by setting the injector gain according to the fuel pressure based on the detection information from the fuel pressure sensor 63.

In this case, the fuel pressure is set to the high pressure regulator 1
4, the discharge pressure of the high-pressure fuel pump 5 works effectively. That is, the fuel is discharged from the low-pressure fuel pump 4 and pressurized to a high pressure by the high-pressure fuel pump 5, and the amount of discharge from the high-pressure fuel pump 4 is small, so that the throttle 62 and the high-pressure regulator 14 work effectively. The fuel adjusted to a predetermined pressure value (5.5 to 7 MPa) at 14 is supplied to the fuel injection valve 1, and the surplus fuel is returned to the fuel tank 2. In addition, since the throttle is used, the fact that pressure feed is generated by the throttle is used. Therefore, the fuel pressure changes due to a change in the discharge amount of the pump depending on the number of revolutions of the engine.

Further, when the engine speed is equal to the predetermined speed (2
When the fuel injection valve 1 becomes higher than 500 rpm), the driving of the fuel injection valve 1 is controlled in a high-pressure mode (a mode other than the idle mode). That is, the high-pressure injector gain is selected.
At this time, the reason why the output of the fuel pressure sensor is not used is that 2500 rpm
At m or more, the fuel pressure is almost constant, the calculation load on the engine computer can be reduced as compared with selecting the gain in accordance with the sensor output, and there is no influence from sensor errors and the like. The fuel is discharged from the low-pressure fuel pump 4 and pressurized to a high pressure by the high-pressure fuel pump 5, and the discharge amount from the high-pressure fuel pump 4 increases. Fuel whose pressure has been adjusted to a predetermined pressure value (7 MPa) by the high-pressure regulator 14 is supplied to the fuel injection valve 1, and surplus fuel is returned to the fuel tank 2.

Next, a modification of the third embodiment will be described. FIG. 5 schematically shows a modification of the third embodiment. As shown in FIG.
The position of the stop (orifice) 62 of the apparatus of the embodiment is different. In addition, other
It is configured similarly to the device of the embodiment. The high-pressure regulator 14 regulates the fuel pressure to 2 MPa, and the high-pressure regulator 57 regulates the fuel pressure to 5 MPa.

Immediately after starting, the controller performs control in a start mode. When the start mode is completed, when the engine is running at a low speed, the fuel pressure is adjusted to 5 MPa mainly by the high pressure regulator 57 alone. As the discharge flow rate of the high-pressure fuel pump 5 increases in accordance with the increase, the resistance of the throttle 62 increases, and when the fuel pressure on the upstream side of the throttle 62, that is, on the injector 1 side reaches 7 MPa, the high-pressure regulator 14 Adjusts the fuel pressure on the injector 1 side to 7 MPa while appropriately opening.

Therefore, depending on the engine speed, 5
The fuel pressure is continuously adjusted in the range of MPa to 7 MPa. However, since the resistance of the throttle 62 acts even when the engine is running at a low speed, the substantial control range of the fuel pressure is considered to be about 5.5 to 7 MPa. In the controller, based on the detection information from the fuel pressure sensor 63,
The driving of the injector 1 is controlled by setting an injector gain according to the fuel pressure.

Since the device of this modification is configured as described above, the fuel supply control is performed as follows. That is, FIG.
With reference to this device, when the engine is started, the low-pressure fuel pump 4 and the high-pressure fuel pump 5 are also started, but at the same time, the controller opens the electromagnetic switching valve 9 and
Drive control of the fuel injection valve 1 is performed in the engine start mode. That is, the injector gain in the engine start mode is selected. In this case, the fuel discharged from the low-pressure fuel pump 4 and adjusted to a predetermined low-pressure value by the low-pressure regulator 8 downstream is supplied to the injector 1, and the surplus fuel is returned to the fuel tank.

Immediately after the start of the engine, the discharge pressure of the high-pressure fuel pump 5 does not immediately rise.
Although the discharge pressure from the low-pressure fuel pump 4 is not sufficiently exerted due to the resistance of the flow of the fuel flow in the inside, in the present device, the fuel injection is performed through the bypass passage 11 provided in parallel with the high-pressure fuel pump 5. Since fuel is supplied to the valve 1 side, fuel injection can be performed from the fuel injection valve 1 at a fuel pressure of about 0.33 MPa adjusted by the low pressure regulator 8.

In general, immediately after the start of the engine, the amount of fuel required for combustion is small, so that the pulse width of the fuel injection is short, and the pulse timing of the fuel injection is the same as in the conventional multipoint injection (MPI). Only during the intake stroke is sufficient, and accordingly, the injector gain in the engine start mode is selected and fuel injection is performed. Therefore, even if the fuel pressure is about the adjustment pressure level of the low-pressure regulator 8, If the fuel pressure is stable, the rotation of the engine can be smoothly increased.

Thereafter, after a predetermined time has elapsed since the start of the engine, and after the vapor has been sufficiently discharged, the controller always closes the electromagnetic switching valve 9. Thereafter, the fuel pressure is adjusted by the throttle 62 and the high-pressure regulators 14 and 57 according to the engine speed. For example, if the engine speed is low, the throttle 62 does not have a large resistance (for example, about 0.5 MPa), and the fuel pressure is adjusted to about 5.5 MPa by the high-pressure regulator 57 and the throttle 62. And, as the engine speed increases,
The resistance due to the throttle 62 increases, and the fuel pressure increases. Then, when the fuel pressure on the injector 1 side becomes 7 MPa, the high-pressure regulator 57 adjusts the fuel pressure to 7 MPa while appropriately opening it. On the other hand, when the engine speed is a predetermined speed (250
At 0 rpm or less, the fuel injection valve 1 is controlled by setting the injector gain according to the fuel pressure based on the detection information from the fuel pressure sensor 63.

In this case, the fuel pressure is set to the high pressure regulator 1
4, the discharge pressure of the high-pressure fuel pump 5 works effectively. That is, while being discharged from the low-pressure fuel pump 4 and pressurized to a high pressure by the high-pressure fuel pump 5, the amount of discharge from the high-pressure fuel pump 4 is small, so that the throttle 62 and the high-pressure regulator 57 effectively operate, and the throttle 62 and the high-pressure regulator Fuel adjusted to a predetermined pressure value (5.5 to 7 MPa) at 57 is supplied to the fuel injection valve 1, and excess fuel is returned to the fuel tank 2. In addition, since the throttle is used, the fact that pressure feed is generated by the throttle is used. Therefore, the fuel pressure changes due to a change in the discharge amount of the pump depending on the number of revolutions of the engine.

Further, when the engine speed is equal to the predetermined speed (2
When the fuel injection valve 1 becomes higher than 500 rpm), the driving of the fuel injection valve 1 is controlled in a high-pressure mode (a mode other than the idle mode). That is, the high-pressure injector gain is selected.
At this time, the reason why the output of the fuel pressure sensor is not used is that 2500 rpm
At m or more, the fuel pressure is almost constant, the calculation load on the engine computer can be reduced as compared with the case where the gain is selected in accordance with the sensor output, and the sensor is not affected by errors or the like. The fuel is discharged from the low-pressure fuel pump 4 and pressurized to a high pressure by the high-pressure fuel pump 5, and the discharge amount from the high-pressure fuel pump 4 increases. Fuel whose pressure has been adjusted to a predetermined pressure value (7 MPa) by the high-pressure regulator 14 is supplied to the fuel injection valve 1, and surplus fuel is returned to the fuel tank 2.

FIG. 6 shows the fuel pressure characteristics of the device according to the third embodiment and its modified example. The vertical axis represents the net effective pressure Pe, and the horizontal axis represents the engine speed. As shown in the figure, the fuel consumption and the output can be improved at a high fuel pressure (7 MPa) in the high pressure mode except during the idling time. At the time of idling, there is an advantage that an increase in injector driving noise can be prevented at a relatively low fuel pressure (5 MPa) in the low pressure mode. When the engine is idling, the engine speed is low and the fuel flow rate is low. Therefore, when the fuel pressure is increased, the lift amount of the high-pressure regulator 14 becomes small and there is a possibility that dust is caught. Since it is made lower, there is an advantage that it is possible to prevent dust and the like caused by a low flow rate.

In the present apparatus, since the fuel pressure changes smoothly, there is little problem such as torque shock due to the fuel pressure fluctuation, and there is an advantage that the torque can be smoothly increased or decreased. Further, in the device of the present embodiment, since the throttle 62 is used in place of the electromagnetic switching valve, there is an advantage that the power consumption is small and the device is economical. In addition, since a simple configuration using the throttle 62 without using the electromagnetic switching valve can reduce the cost, the cost can be reduced, the fuel consumption can be improved, the injector driving noise can be prevented, and the reliability of the device can be improved. There is an advantage that it can be achieved.

Further, since the fuel pressure is determined by the rotation speed of the high-pressure fuel pump 5, there is an advantage that a control logic for controlling the electromagnetic switching valve and a matching man-hour are not required. In addition, in the case of the first embodiment and the modification of the first embodiment, the high-pressure regulator of the apparatus main body is 2
It is also possible to use a device capable of adjusting the pressure to 5 MPa or 7 MPa, or a device capable of adjusting the additional device to 5 MPa.

In each of the devices of the first embodiment, the modified example of the first embodiment, and the second embodiment, the fuel pressure is set to 0.33 MPa when the engine is started, and to 5 M at the time of idling.
The pressure is set to 7 MPa except when the pressure is Pa and at the time of idling, but the pressure is not limited to these set pressures. Also,
It is considered that the torque when the engine is fully opened can be improved depending on how the pressure is set by the regulator.

[0111]

As described above in detail, the fuel supply system for an internal combustion engine according to the first aspect of the present invention has the advantage that the fuel pressure can be set according to the operating state of the engine. That is, the fuel consumption and the output can be improved with the high fuel pressure in the high pressure mode except during the idling time. At the time of idling, there is an advantage that an increase in injector driving noise can be prevented with a relatively low fuel pressure in the low pressure mode. Also, when the engine is idle, the engine speed is low and the fuel flow rate is low. Therefore, when the fuel pressure is increased, there is a possibility that dust may be trapped. And the like can be prevented.

According to the fuel supply device for an internal combustion engine according to the second aspect of the present invention, there is an advantage that the fuel pressure can be set according to the operating state of the engine. That is, the fuel consumption and the output can be improved with the high fuel pressure in the high pressure mode except during the idling time. At idle,
There is an advantage that the injector driving noise can be prevented from increasing at a relatively low fuel pressure in the low pressure mode.
Also, when the engine is idle, the engine speed is low and the fuel flow rate is low. Therefore, when the fuel pressure is increased, there is a possibility that dust may be trapped. And the like can be prevented.

According to the fuel supply device for an internal combustion engine according to the third and fourth aspects of the present invention, the cost can be reduced since the fuel supply device has a simple structure in which a throttle is used without using an electromagnetic switching valve. At the same time, the fuel consumption and the output can be improved by the high fuel pressure in the high pressure mode except during the idling time. At the time of idling, there is an advantage that an increase in injector driving noise can be prevented with a relatively low fuel pressure in the low pressure mode. Further, since the throttle is used in place of the electromagnetic switching valve, there is an advantage that it is economical because the power consumption is small.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating an apparatus according to a modification of the first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram illustrating an apparatus according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing an apparatus according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram showing an apparatus according to a modification of the third embodiment of the present invention.

FIG. 6 is a diagram showing fuel pressure characteristics adjusted by the device according to the third embodiment of the present invention and its modification.

FIG. 7 is a schematic configuration diagram showing a conventional fuel supply device for an internal combustion engine.

FIG. 8 is a configuration diagram schematically showing a relationship between a main part of a conventional fuel supply device for an internal combustion engine and an engine.

FIG. 9 is a diagram showing a fuel efficiency improvement ratio of lean combustion in a compression stroke for explaining the problem of the present invention, wherein (a) is a diagram showing a fuel efficiency improvement ratio when the fuel pressure is 5 MPa; FIG. 6B is a diagram showing a fuel efficiency improvement rate when the fuel pressure is set to 7 MPa.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fuel injection valve 2 Fuel tank 3 Fuel passage 3A Fuel passage supply path 3B Fuel passage return path 4 Low pressure fuel pump 5 High pressure fuel pump 6 Fuel filter 7, 12, 51 Check valve 8 Low pressure control as low pressure control means Valves 9, 56 Electromagnetic switching valve (fuel pressure switching valve) 10, 50, 53 Fixed throttle as fuel pressure holding mechanism 11, 13, 55, 60 Bypass passage 14, 56, 57, 59 High pressure control valve 62 as high pressure control means Throttle 63 Fuel pressure sensor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 37/00 F02M 37/00 311

Claims (5)

(57) [Claims] 1. A circulation circuit provided between a fuel injection valve provided in an internal combustion engine and a fuel tank, from the fuel tank to the fuel injection valve, and from the fuel injection valve back to the fuel tank. A high-pressure fuel pump provided on the fuel passage upstream of the fuel injection valve and driven by the internal combustion engine; and a fuel passage provided downstream of the high-pressure fuel pump.
First high-pressure control means for controlling the fuel pressure discharged from the high-pressure fuel pump; and a first bypass passage provided around the first high-pressure control means, wherein the first bypass passage is provided in accordance with an engine operating state. A first fuel pressure switching valve that opens and closes; a second high pressure control provided in the first high pressure control means and a fuel passage portion downstream of the first bypass passage portion to control a fuel pressure discharged from the high pressure fuel pump. Means, and a second fuel pressure switching valve provided in a second bypass passage part bypassing the second high pressure control means and opening and closing the second bypass passage in accordance with an engine operating state. A fuel supply device for an internal combustion engine. 2. A circulation circuit provided between a fuel injection valve provided in an internal combustion engine and a fuel tank, from the fuel tank to the fuel injection valve, and from the fuel injection valve back to the fuel tank. A high-pressure fuel pump provided on the fuel passage upstream of the fuel injection valve and driven by the internal combustion engine; and a fuel passage provided downstream of the high-pressure fuel pump.
First high-pressure control means for controlling the fuel pressure discharged from the high-pressure fuel pump; and a first bypass passage provided around the first high-pressure control means, wherein the first bypass passage is provided in accordance with an engine operating state. A first high-pressure switching valve that opens and closes; a second high-pressure control valve that is provided in the first high-pressure control means and a second bypass passage that bypasses the first bypass passage, and that controls a fuel pressure that is discharged from the high-pressure fuel pump. Control means, and a second fuel pressure switching valve provided in series with the second high-pressure control means in the second bypass passage portion and opening and closing the second bypass passage in accordance with an engine operating state. A fuel supply device for an internal combustion engine, characterized by: 3. A circulation circuit provided between a fuel injection valve provided in an internal combustion engine and a fuel tank, from the fuel tank to the fuel injection valve, and back from the fuel injection valve to the fuel tank again. A high-pressure fuel pump provided on the fuel passage upstream of the fuel injection valve and driven by the internal combustion engine; and a fuel passage provided downstream of the high-pressure fuel pump.
First high-pressure control means for controlling the pressure of the fuel discharged from the high-pressure fuel pump; and a fuel passage portion provided on a fuel passage portion downstream of the first high-pressure control means for controlling the fuel pressure discharged from the high-pressure fuel pump. 1
A second high-pressure control means for controlling the pressure to a pressure higher than the pressure regulated by the high-pressure control means; a first high-pressure control means and a first bypass passage which bypasses the second high-pressure control means; A fuel pressure switching valve that opens and closes the first bypass passage in accordance with an engine operating state; and a throttle provided in a second bypass passage that bypasses the first high-pressure control means.
Fuel supply device for internal combustion engines. 4. A circulation circuit provided between a fuel injection valve provided in an internal combustion engine and a fuel tank, from the fuel tank to the fuel injection valve, and from the fuel injection valve back to the fuel tank again. A high-pressure fuel pump provided on the fuel passage upstream of the fuel injection valve and driven by the internal combustion engine; and a fuel passage provided downstream of the high-pressure fuel pump.
First high-pressure control means for controlling the pressure of the fuel discharged from the high-pressure fuel pump; and a fuel passage portion provided on a fuel passage portion downstream of the first high-pressure control means for controlling the fuel pressure discharged from the high-pressure fuel pump. 1
A second high-pressure control means for controlling the pressure to a pressure lower than the pressure regulated by the high-pressure control means; and a first high-pressure control means and a first bypass passage which bypasses the second high-pressure control means, A fuel pressure switching valve that opens and closes the first bypass passage in accordance with an engine operating state; and a throttle provided in a second bypass passage portion that bypasses the second high-pressure control means.
Fuel supply device for internal combustion engines. 5. A low-pressure fuel pump provided upstream of the high-pressure fuel pump, and a fuel passage provided downstream of the low-pressure fuel pump,
The fuel supply device for an internal combustion engine according to any one of claims 1 to 4, further comprising low pressure control means for controlling a fuel pressure discharged from the low pressure fuel pump.