JPH1061511A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the volume of boosting fuel so as to inject fuel with high pressure instantly even in the case of a low speed rotating condition when an engine is started by directly supplying pressurized fuel to an injector by a booster when the engine is started. SOLUTION: When an engine is started, an operating circuit 35 is connected to an AP, and simultaneously a return circuit 42 is connected to a BR. Fuel is forcibly supplied from a low pressure pump 5 is supplied to the operating chamber 39 of a booster 33, and fuel in a return chamber 41 is returned to a fuel tank 3, and thereby, a piston 47 is moved to a right side in the booster 33, fuel of a boosting circuit 27 is pressurized, and its fuel is directly supplied to an injector 17a. Return of fuel from a first injector 17a to a common rail 9 is blocked by a third check valve 32. Boosted fuel by a booster 33 is supplied to the common rail 9 without supplying to the common rail 9, and thereby, high pressure fuel is directly injected from the injector 17a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for directly injecting high-pressure fuel into an engine cylinder by driving a high-pressure pump by driving an engine.

[0002]

2. Description of the Related Art There is known a so-called direct injection gasoline engine in which high-pressure gasoline fuel is directly injected from an injector into a cylinder of an engine. In a fuel injection device used for this type of gasoline engine, it is required to increase a fuel injection pressure to make a spray state of fuel injected from an injector fine.

On the other hand, in order to keep the injection pressure of the fuel injected from the plurality of injectors constant, each injector is connected to a pressure accumulating chamber called a common rail, and the fuel pressure-fed from the high pressure pump is supplied to a predetermined high pressure by the common rail. The pressure can be increased up to.

However, since the high-pressure pump is operated by driving the engine, a high discharge pressure cannot be obtained at the time of starting the engine because the rotation speed (rotation speed) of the engine is low, and the pressure of the common rail is increased. There is a problem that is difficult. That is, when the rotation speed of the engine is low, fuel leakage increases during pressurization by the high-pressure pump, and the volume efficiency of the high-pressure pump deteriorates, making it difficult to increase the pressure of the fuel.

On the other hand, in Japanese Patent Application Laid-Open No. Hei 7-293381, a bypass passage which can be opened and closed by an electromagnetic valve is provided in parallel with the high pump, and the high pressure pump is bypassed at the time of starting, so that the fuel is injected from the injector at the time of starting. There is disclosed a technique for stabilizing the fuel injection pressure at a low pressure while adjusting the fuel injection amount according to the pressure.

In Japanese Patent Application Laid-Open No. 5-321787, a starting auxiliary pump is provided in addition to the high-pressure pump, which is activated at the time of starting. ) Discloses a configuration for accelerating the boosting.

[0007]

However, in the technique disclosed in the former publication, the fuel is injected from the injector at a low fuel pressure. Therefore, as described above, the spray properties of the fuel are poor and the combustion is unstable. And there is an inconvenience of deteriorating the exhaust characteristics and the like. Therefore, fuel injection under low fuel pressure cannot be adopted.

On the other hand, in the latter technique, even when the engine is started, the pressure of the accumulator is increased at an early stage to try to inject high-pressure fuel from the injector, but the accumulator has a predetermined capacity. For this reason, there is a problem that it takes a predetermined time to increase the pressure of the accumulator even when the auxiliary pump is used together.

An object of the present invention is to provide a fuel injection device that can inject fuel at a high pressure even in a low-speed rotation state when the engine is started.

[0010]

In order to achieve the above object, according to the present invention, a high pressure pump for pressurizing fuel to a high pressure by driving an engine and a fuel pressurized by the high pressure pump are provided. In a fuel injection device including a pressure accumulator that accumulates and supplies the pressure to an injector, a pressure intensifier connected to the injector and increasing the pressure of fuel supplied to the injector, and an actuation unit that operates the pressure intensifier at the time of starting the engine. The fuel pressurized by the pressure intensifier at the time of starting the engine is directly supplied to the injector.

According to the first aspect of the present invention, when the engine is started, the operating means drives the pressure intensifier to directly supply the fuel pressurized to a high pressure to the injector. That is,
The fuel pressurized by the booster is not directly supplied to the accumulator, but is directly supplied to the injector.Therefore, the volume of the fuel to be boosted is small. Fuel can be injected.

According to a second aspect of the present invention, in the first aspect, the operating means includes a supply pump for supplying fuel from a fuel tank to the high-pressure pump, and a supply of fuel supplied from the supply pump. Switching means for switching to the pressure intensifier at the start, and switching the switching means at the time of starting the engine to operate the pressure intensifier with the fuel supplied from the supply pump.

According to the second aspect of the present invention, the supply pump for supplying fuel to the high-pressure pump is used. When the engine is started, the circuit of the fuel supplied from the supply pump is switched to operate the pressure intensifier. Let it. Therefore, there is no need for a separate pump to operate the intensifier,
The configuration of the entire apparatus can be simplified.

According to a third aspect of the present invention, there is provided the first or second aspect.
In the invention described in the above, a plurality of the injectors are provided, the pressure intensifier is connected to only some of these injectors, and the operating means operates when the pressure intensifier is operated. This inhibits fuel injection from other injectors.

According to the third aspect of the present invention, the pressure intensifier is connected to only some of the plurality of injectors, and when starting the engine, the high pressure fuel is injected only from the injectors and the other injectors are used to inject the high pressure fuel from the other injectors. Prohibit fuel injection. Therefore, when the engine is started, low-pressure fuel is prevented from being injected from another injector to which no pressure intensifier is connected, and only high-pressure injection can be performed. Further, since there is no discharge of fuel from the pressure accumulator via another injector when the engine is started, the pressure increase in the pressure accumulator can be promoted, and high-pressure fuel can be injected from all the injectors at an early stage.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. A fuel injection device 1 according to an embodiment of the present invention directly injects gasoline into a combustion chamber (cylinder) of a gasoline engine, and is used for a so-called direct injection gasoline engine.

As shown in FIG. 1, the fuel injection device 1 includes a fuel tank 3, a low-pressure pump (operating means or supply pump) 5 provided in the fuel tank 3, a high-pressure pump 7,
A main circuit is formed by connecting a common rail 9 as a pressure accumulator for accumulating the fuel pressure-fed from the high pressure pump 7, a high pressure regulator 11, and a low pressure regulator 13. The low-pressure pump 5 pumps fuel (gasoline) in the fuel tank 3 to the high-pressure pump 7, and a filter 15 is interposed between the low-pressure pump 5 and the high-pressure pump 7.

The high-pressure pump 7 pressurizes the fuel supplied from the low-pressure pump 5 to a high pressure. The high-pressure pump 7 is driven by the engine, pressurizes the fuel to a high pressure, and feeds the fuel to the common rail 9.

A plurality of first to fourth injectors 17a, 17b, 17c and 17d are connected to the common rail 9, and the fuel stored at a high pressure by the common rail 9 is supplied to each of the first to fourth injectors 17a, 17b. 17b, 17c, 1
Injection starts from 7d. The common rail 9 is provided with a pressure detector 21 for detecting pressure, and is configured to send a detected pressure signal to a control device 23 described later.

A part of the excess fuel of the common rail 9 is returned to the fuel tank 3 via the low pressure regulator 13 together with the excess fuel of the high pressure pump 7 via the high pressure regulator 11. In addition, each of the first to fourth injectors 17a, 17
Each of b, 17c, and 17d is connected to a drive circuit 25, and the injection timing and the stop of the injection by the control device 23 are individually controlled via the drive circuit 25.

A pressure increasing circuit 27 is connected to the first injector 17a via first and second check valves 29 and 31, and these first check valve 29 and second check valve 31 are connected to each other. Between them, a pressure intensifier 33 is arranged. The first check valve 29 prevents the fuel from flowing from the pressure intensifier 33 to the fuel tank 3, and the second check valve 31 is connected to the first injector 17 a from the pressure intensifier 33.
Blocking the flow of fuel to

Further, an operation circuit 35 for operating the pressure intensifier 33 is formed between the low pressure pump 5 and the high pressure pump 7. The operation circuit 35 is connected to an operation chamber 39 and a return chamber 41 of the pressure intensifier 33 via a switching valve 37. The pressure intensifier 33 is provided with a piston 47 integrally having a large-diameter low-pressure-side piston portion 44 and a small-diameter high-pressure-side piston 45 in a casing thereof. The above-described working chamber 39 is provided on the low-pressure-side piston portion 44 side. The return chamber 41 is formed between the low pressure side piston portion 44 and the high pressure side piston 45.
Are formed, and the pressurizing chamber 43 is formed in the high-pressure side piston 45.

The switching valve 37 is a two-position switching valve.
In the first position shown in FIG. 2, the reference symbols P and A in the figure are connected, and B and R are connected, the fuel pumped from the low-pressure pump 5 as the operating means is supplied to the operating chamber 39, and the return chamber 41 A circuit is configured to return the fuel inside the fuel tank 3 from the return passage 42 to the fuel tank 3. Therefore, at the first position, the pressure intensifier 35 operates to move the piston 47 to the right in FIG. 1 to increase the fuel pressure of the pressure intensifying circuit 27. On the other hand, in the second position, FIG.
The reference symbols P and B are connected to each other, and A and R are connected to each other to supply the fuel pumped from the low-pressure pump 5 to the return chamber 41 and to discharge the fuel in the working chamber 39 from the return passage 42 to the fuel tank 3. A circuit is configured to move the piston 47 to the right, release the pressure in the working chamber 39 to the fuel tank 3, and stop the operation of the pressure intensifier 35.

Next, the operation of the fuel injection device 1 will be described. First, the operation when the engine is rotating at a high speed (after starting the engine) in a normal state will be described. During this high-speed rotation, the fuel (gasoline) in the fuel tank 3 is supplied from the low-pressure pump 5 to the high-pressure pump 7 through the filter 15. The high-pressure pump 7 is driven by the rotation of the engine to pressurize the fuel to a high pressure, and sends it to the common rail 9 to accumulate the pressure. The accumulated fuel is injected from the first to fourth injectors 17a to 17d in a high pressure state. Excess fuel in the common rail 9 and the high-pressure pump 7 is returned to the fuel tank 3 via the regulators 11 and 13, respectively. The timing and state of the fuel injection from the injectors 17a to 17d are controlled by the control device 23 via the drive circuit 25.

Next, the operation when the engine is started (when the engine is rotating at a low speed) will be described with reference to FIG. First, when the operation is started by turning on the switch by the ignition key, in step S1, the control device 23
7 is switched to the first position.

That is, the operation circuit 35 is connected to the AP in FIG. 1, and at the same time, the return passage 42 is connected to the BR. As a result, the fuel pumped from the low-pressure pump 5 is supplied to the intensifier 33.
Is supplied to the working chamber 39 and the fuel in the return chamber 41 is returned to the fuel tank 3.
Moves to the right in the figure, pressurizes the fuel in the pressure increasing circuit 27, and is supplied directly to the injector 17a. The return of fuel from the first injector 17a to the common rail 9 is prevented by the third check valve 32. In other words, the fuel whose pressure has been increased by the pressure intensifier 33 is directly supplied to the injector 17a without being supplied to the common rail 9 having a predetermined volume, so that high-pressure fuel can be directly injected from the injector 17a.

Moreover, in the present embodiment, the injector for supplying high-pressure fuel from the pressure-intensifying circuit is the first injector 1
7a, only the pressure obtained by the pressure increasing circuit 27 can be directly injected without dispersing the high-pressure fuel of the pressure increasing circuit 27.

Next, at step S3, the control device 23 sends the second to fourth injectors 17b via the drive circuit 25.
Prohibits fuel injection from １７17d. That is, the low-pressure injection that injects without the pressure of the common rail 9 rising to a predetermined value is prohibited. Accordingly, since the second to fourth injectors 17b to 17d do not perform low-pressure injection, all of the first to fourth injectors 17a to 17d perform only high-pressure injection. Therefore, a favorable injection state can be ensured in all the injectors. Further, when the injection using the pressure increasing circuit 27 is performed, since there is no injection from the other injectors 17b to 17d, the fuel in the common rail 9 is not discharged during the low-speed operation of the engine and the pressure in the common rail 9 is reduced. The pressure can be increased to a predetermined high pressure in a short time.

Subsequently, in step S4, it is determined whether or not the engine speed is 0. If the engine speed is 0, the process returns to step S1, and if not, the process proceeds to the next step S5.

In step S5, the detected pressure PF from the pressure detector 21 provided on the common rail 9 is compared with a predetermined target value PH. If the common rail internal pressure PF is larger than the target pressure, the process proceeds to step S6. Then, the prohibition of injection of the second to fourth injectors 17b to 17d is released.
Subsequently, in step S9, the switching valve 37 is switched to the second position, the operation circuit is connected to the BP, and the return passage 42 is set to the A position.
Connect to R and end. On the other hand, if the common rail internal pressure PF is smaller than the target pressure in step S5, the process again proceeds to step S7, where it is determined whether or not the engine speed is zero.
5 and waits for an increase in the fuel pressure in the common rail 9. That is, in step S7, the rotation state of the engine is checked again, and when the engine rotation speed is 0, for example, when the engine is stopped before the pressure rises,
The presenter is returned to the initial state by making the BP connection, and the process is temporarily terminated to prepare for the restart.

On the other hand, if the engine speed is not 0 in step S7, that is, if the engine is continuing to rotate, the process proceeds to step S8, where the switching valve 37 is switched to the second position, and the operation circuit 35 is turned on. It connects to the BP of FIG. 1 and at the same time connects the return passage 42 to the AR. As a result, the piston 47 is moved to the left to release the pressure in the working chamber 39 to the fuel tank 3, thereby stopping the operation of the pressure intensifier 35 and terminating the control at the low speed rotation of the engine. Thereafter, in the pressure intensifier 35, the piston 47 moves to the left, reduces the pressure in the pressure intensifying circuit 27, and returns to the start after preparing for the next pressure increasing.

In the present embodiment, even when the engine is running at a low speed, high-pressure injection of fuel can be realized from the injector, so that the fuel spray state is good, combustion is stable, and the exhaust characteristics of the engine are excellent. In addition, since the fuel injection from the injectors not connected to the pressure increasing circuit is prohibited during the low-speed operation, complete high-pressure injection of fuel can be realized without performing low-pressure injection from all injectors.

In this embodiment, the existing low-pressure pump 5 for sending the fuel in the fuel tank 3 to the high-pressure pump 7 is used as the operating means for operating the pressure intensifier 35.
The number of parts can be reduced, and the configuration can be simplified.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention. For example, the control device 23 detects the pressure in the common rail 9 and cancels the operation of the pressure intensifier 33, but is not limited thereto, and detects the rotation speed of the engine and cancels the operation of the pressure intensifier 33. However, a similar effect can be obtained. In this case, in step S5, the target pressure is compared with the target rotational speed instead of the target pressure PF.

The number of the injectors 17a connected to the pressure increasing circuit 27 is not limited to one, but may be two, three, or the like. In this case, it is desirable to provide a third check valve 32 between the injector connected to each pressure booster circuit and the common rail 9.

Further, the operating means for operating the pressure intensifier 33 is not limited to using a low-pressure pump, but may be configured to separately include an auxiliary pump or the like for driving the pressure intensifier 33.

[0037]

According to the first aspect of the present invention, when the engine is started, the fuel pressurized by the pressure intensifier is directly supplied to the injector without the intervention of the pressure accumulator. Fuel can be injected at a high pressure even in the low-speed rotation state.

According to the second aspect of the present invention, since the supply pump for supplying fuel to the high-pressure pump is used for operating the pressure intensifier, a separate pump for operating the pressure intensifier is not required. Therefore, the configuration of the entire apparatus can be simplified.

According to the third aspect of the present invention, since the pressure intensifier is connected to only some of the plurality of injectors and prohibits the injection of fuel from other injectors, all the injectors are connected. Therefore, only high-pressure injection can be reliably performed. Further, since no fuel is discharged from the pressure accumulator when the engine is started, the pressure increase in the pressure accumulator can be promoted.

[0040]

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a schematic configuration of a fuel injection device according to the present invention.

FIG. 2 is a flowchart showing a control flow during low-pressure operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fuel injection device 5 Low-pressure pump (actuation means or supply pump) 7 High-pressure pump 9 Common rail (pressure accumulator) 17a Injector (injector to which a pressure intensifier is connected) 17a, 17b, 17c, 17d Injector (other injectors) 27 Circuit 37 Switching valve (switching means) 33 Booster

Claims (3)

[Claims] 1. A fuel injection device comprising: a high-pressure pump for pressurizing fuel to a high pressure by driving an engine; and a pressure accumulator for accumulating fuel pressurized by the high-pressure pump and supplying the fuel to an injector. A booster for increasing the pressure of the fuel supplied to the injector; and an operating means for operating the booster at the time of starting the engine, wherein the fuel pressurized by the booster at the time of starting the engine is directly supplied to the injector. Characteristic fuel injection device. The operating means includes a supply pump for supplying fuel from a fuel tank to the high-pressure pump, and switching means for switching a supply destination of the fuel supplied from the supply pump to the pressure intensifier. 2. The fuel injection device according to claim 1, wherein the switching means is switched to operate the pressure intensifier with the fuel supplied from the supply pump. 3. A plurality of said injectors are provided, said pressure intensifier is connected to only some of said injectors, and when said operating means operates said pressure intensifier other 3. The fuel injection device according to claim 1, wherein fuel injection from the injector is prohibited.