JPH11200988A - Fuel supply system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid any infructuous work of a high pressure fuel pump at high- speed operation by installing a pressure sensor to detect pressure in a common rail, and a controller to control the opening or closing of a solenoid valve according to a detection signal out of this pressure sensor, respectively. SOLUTION: When fuel pressure in a common rail 7 exceeds the specified level by a fuel supply by a low-pressure fuel pump 3 and the drive of a high- pressure fuel pump 5 by an internal combustion engine 14, a solenoid valve 10 is opened free by a control signal to this solenoid valve 10 from a controller 9, and high pressure fuel from the high-pressure fuel pump 5 is returned to a fuel tank 2 from a low-pressure passage 19 via a branch point 16 at the downstream side, thereby unloading the high-pressure fuel pump 5. Since a one-way valve 6 is situated at the downstream side of this high-pressure fuel pump 5, this pump 5 itself comes into a state of being separated from a high pressure section in the common rail 7. With this, any possible infructuous work of the high-pressure fuel pump at high-speed operation is made avoidable in consequence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system for an internal combustion engine, and more particularly to a fuel supply system for a gasoline engine and other internal combustion engines using a fuel pump which does not perform internal compression, such as a gear pump or a trochoid pump. It is about.

[0002]

2. Description of the Related Art A conventional gear pump has a low volumetric efficiency. Therefore, when it is driven directly by an internal combustion engine, for example, when it is driven directly by a camshaft, the pump is operated at a low speed of the internal combustion engine (especially when starting the engine). ) Has a problem that it is difficult to obtain a sufficient discharge amount and fuel pressure.

As a means for obtaining a sufficient discharge flow rate at a low speed of the internal combustion engine, it is conceivable to increase the capacity of the pump. In the case of such means, not only the flow rate is increased due to the increase in the capacity, but also the volume efficiency is improved, but at the same time, when the engine is running at a high speed, the excess flow rate is increased, and the wasteful power consumption of the pump is increased. is there.

For example, in a "fuel supply device for an internal combustion engine" disclosed in JP-A-7-77118, a reciprocating compression engine is used to compress and supply gasoline as fuel, and after a high pressure is generated in a common rail (pressure accumulator). Although the high-pressure control means is opened to relieve high-pressure fuel, the relief after high-pressure generation is disadvantageous because the loss of the pump is large.

[0005] Japanese Patent Application Laid-Open No. 7-293394 discloses a "fuel injection device used in an internal combustion engine" which employs a piston type pump for supplying fuel and leaks the fuel after the pump has compressed the fuel. There is a problem that can not be avoided.

The "fuel injection device" disclosed in Japanese Patent Application Laid-Open No. 62-258160 employs a piston type pump for supplying fuel, and leaks from an upstream side of a check valve provided between the pump and the common rail. However, in order to adjust the discharge amount from the pump, it is necessary to open and close an electromagnetic valve synchronized with the lift of the pump piston,
There is a problem that control means is complicated.

[0007] Other known fuel supply devices include JP-A-8-158981 and JP-A-9-4498.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a hydraulic circuit for reducing the work of a high-pressure fuel pump used in a fuel supply device for an internal combustion engine. It is an object to provide a fuel supply device for an internal combustion engine having the same.

Another object of the present invention is to provide a fuel supply device for an internal combustion engine that performs control to appropriately release the fuel pressure held in the common rail.

Further, the present invention provides a fuel supply device for an internal combustion engine in which an electromagnetic valve is provided in a passage of a high-pressure fuel pump, and when the discharge flow rate is excessive, the electromagnetic valve can be opened to lower the discharge pressure. The task is to provide.

The present invention can ensure a sufficient fuel discharge amount at the time of starting the internal combustion engine or at other low speeds.
It is an object of the present invention to provide a fuel supply device for an internal combustion engine which can save useless work of a high-pressure fuel pump when a discharge flow rate is excessive such as at a high speed.

Another object of the present invention is to provide a fuel supply device for an internal combustion engine which can reduce wasteful work of a high-pressure fuel pump at low cost.

Another object of the present invention is to provide a fuel supply device for an internal combustion engine that can simplify the control operation and its structure.

[0014]

That is, according to the present invention, when a gear type pump or a trochoid pump which does not perform internal compression is employed, an electromagnetic valve is provided in a passage connecting a high pressure side and a low pressure side of the pump. When the discharge flow rate of the pump is excessive, the solenoid valve is opened to reduce the discharge pressure, thereby focusing on eliminating unnecessary work of the pump. A low-pressure fuel pump for supply, and a high-pressure fuel pump for fuel supply for increasing the pressure of fuel from the low-pressure fuel pump,
A fuel supply device for an internal combustion engine that supplies a predetermined high-pressure fuel to a common rail of the internal combustion engine by the high-pressure fuel pump, the fuel supply device being connected in series to the high-pressure fuel pump in a fuel supply-side passage provided with the high-pressure fuel pump. A directional valve,
An electromagnetic valve provided in a relief passage branched from a pump discharge side of the high-pressure fuel pump and connected to the pump inflow side,
A pressure sensor for detecting the pressure in the common rail,
A controller for controlling the opening and closing of the solenoid valve according to a detection signal from the pressure sensor.

[0015] The one-way valve may be provided downstream of the high-pressure fuel pump.

[0016] The one-way valve may be provided upstream of the high-pressure fuel pump.

A bypass passage may be provided in the fuel supply side passage of the high-pressure fuel pump, and a bypass valve may be provided in the bypass passage.

In the fuel supply device for an internal combustion engine according to the present invention, the high pressure side (pump discharge side) of the high pressure fuel pump is provided.
A solenoid valve is provided in a relief passage connecting the pressure rail and the low pressure side (pump inflow side), and the pressure of the common rail is detected by a pressure sensor. If this pressure is higher than the target pressure, the discharge flow rate of the high pressure fuel pump is excessive. Then, by opening the solenoid valve and lowering the discharge pressure, the high-pressure fuel pump is unloaded and the high-pressure fuel pump itself is unloaded, so that unnecessary work is omitted. Therefore, unlike the conventional mechanism for reducing the high-pressure fuel pressure of the common rail, the high-pressure regulator of the high-pressure fuel pump is not required, and the pump loss can be reduced. In addition, ON / OFF of the solenoid valve according to the detection signal of the pressure sensor
Since only the OFF control is used, the control means or the hydraulic circuit itself can be designed with a simple configuration.

Further, when a gear pump or a trochoid pump is used as the high-pressure fuel pump, even if the capacity is increased and the fuel supply amount is increased at the time of starting or the like, the increase in cost is minimized and the cost is reduced. Can be manufactured.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a fuel supply device 1 for an internal combustion engine according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic circuit diagram of a fuel supply device 1 for an internal combustion engine. The fuel supply device 1 for an internal combustion engine includes, for example, a fuel tank 2 such as gasoline, a low-pressure fuel pump 3 for fuel supply, and a low-pressure regulator thereof. 4, a high-pressure fuel pump 5 for fuel supply, a one-way valve 6, a pressure sensor 8 attached to a common rail 7, a controller 9, a solenoid valve 10, a bypass valve 11, and a safety valve 1.
And 2.

The low-pressure fuel pump 3, the high-pressure fuel pump 5, and the one-way valve 6 are provided in series in the fuel supply passage 13 in this order. The low-pressure fuel pump 3 is driven by an electric motor (not shown) or the like, and supplies a constant-pressure fuel to the high-pressure fuel pump 5 regardless of the rotation speed of the internal combustion engine. The low pressure regulator 4 maintains and controls the fuel supply pressure of the low pressure fuel pump 3 at a predetermined low pressure level.

The high-pressure fuel pump 5 is connected to the internal combustion engine 14
The high pressure of the low pressure fuel from the low pressure fuel pump 3 is supplied to the common rail 7 via the one-way valve 6. A fuel injection valve 15 is connected to the common rail 7 for each of a predetermined number of cylinders, and the fuel is injected from the fuel injection valve 15 into the cylinder at a predetermined timing.

The one-way valve 6 is provided downstream of the high-pressure fuel pump 5 in the fuel supply passage 13 to ensure one-way fuel supply from the high-pressure fuel pump 5 to the common rail 7.

The common rail 7 temporarily stores high-pressure fuel from the high-pressure fuel pump 5 and stabilizes the supply of high-pressure fuel to the fuel injection valve 15. The pressure sensor 8 detects the pressure in the common rail 7 and outputs a detection signal to the controller 9.

The controller 9 controls ON / OFF of the solenoid valve 10 in response to a detection signal from the pressure sensor 8, and outputs a control signal corresponding to a differential pressure ΔP between the target pressure P and the pressure Pc in the common rail 7. It is output to the solenoid valve 10 to control opening and closing. However, this opening / closing control is an ON / OFF control having a hysteresis width. As the signal processing, the input from the pressure sensor 8 is output to the solenoid valve 10 side through a Schmitt circuit that compares the input with the target pressure P. That is, PWM (Pulse
When Width Modulation) control is performed,
Since the pressure on the high-pressure side (downstream side) of the high-pressure fuel pump 5 does not decrease, the high-pressure fuel pump 5 is only subjected to the throttle action without being in a no-load state, and the power reduction effect of the high-pressure fuel pump 5 is lost. In the present invention, the ON / OFF control for providing a hysteresis width is performed.

The solenoid valve 10 is provided in the fuel supply passage 13 in parallel with the high-pressure fuel pump 5, that is, at the downstream branch point 16.
This is provided in a relief passage 18 which branches from the downstream branch point 16 and connects the downstream branch point 16 and the upstream branch point 17. The high pressure from the downstream branch point 16 is returned to the fuel tank 2 via the low-pressure passage 19 and the low-pressure regulator 4 according to the release control signal from the controller 9.

The bypass valve 11 is connected to the fuel supply passage 13
This is provided between a one-way valve 6 and a common rail 7 between a common rail side branch point 21 and an upstream side branch point 17 between the one-way valve 6 and the common rail 7. The bypass passage 20 is opened and closed by a control signal from the controller 9. Especially when starting the engine,
By opening the bypass valve 11 and supplying fuel to the common rail 7 without passing through the high-pressure fuel pump 5 so that fuel can be charged, and by turning off the bypass valve 11 for a certain time when the engine is stopped, The fuel pressure sealed and stored in the pipe (bypass passage 20 or common rail 7) is released by a predetermined ratio, the fuel in the common rail 7 is maintained at a predetermined low pressure, and the startability at the next start is improved.

The safety valve 12 is connected to a branch point 21 on the common rail side.
This is a safety mechanism for providing a recirculation passage 22 branching off from the bypass valve 11 to suppress an increase in fuel pressure at the common rail side branch point 21 or the common rail 7.

The fuel supply device 1 for an internal combustion engine having such a configuration.
, The fuel is supplied into the common rail 7 by the fuel supply by the low-pressure fuel pump 3 and the driving of the high-pressure fuel pump 5 by the internal combustion engine 14. When the fuel pressure in the common rail 7 exceeds a predetermined level (upper limit value P1), the controller The solenoid valve 10 is opened by a control signal from the solenoid valve 9 to the solenoid valve 10, and the high-pressure fuel from the high-pressure fuel pump 5 is returned from the low-pressure passage 19 to the fuel tank 2 through the downstream branch point 16, so that the high-pressure fuel pump Unload 5
Since the one-way valve 6 is located downstream of the high-pressure fuel pump 5, the high-pressure fuel pump 5 itself is disconnected from the high-pressure section of the common rail 7.

When the pressure in the common rail 7 drops to a predetermined level (lower limit value P2), the solenoid valve 10 is closed,
The fuel supply by the high-pressure fuel pump 5 is restarted.

FIG. 2 is a graph showing the time change of the fuel pressure in the common rail 7. The solid line in the figure shows the pressure control according to the present invention, and the dashed line in the figure shows the pressure control by the conventional low pressure regulator 4. Show. As shown in the figure, the pressure of the common rail 7 can be held and controlled in a region of a predetermined width around the target pressure P (region between the lower limit P2 and the upper limit P1).

Thus, when the discharge flow rate of the high-pressure fuel pump 5 is excessive with respect to the common rail 7 such as during high-speed operation of the engine, the solenoid valve 10 is opened to lower the discharge pressure of the high-pressure fuel pump 5, Since the work by the high-pressure fuel pump 5 can be reduced, it is possible to avoid the useless work. Further, unlike the pressure control in the conventional fuel supply device, the pressure is not released after the high pressure is generated in the common rail 7, but the pressure is increased in the portion of the high-pressure fuel pump 5 on the upstream side (downstream branch point 16). Since the high-pressure fuel pump 5 is opened by releasing the load, the driving loss of the high-pressure fuel pump 5 can be minimized. Also, as a control operation, the O
Since only N / OFF control is required, control can be realized with a simple configuration.

The pressure is released when the engine is stopped by opening the bypass valve 11 for a certain period of time. The fuel is held in the common rail 7 at a low fuel pressure, and the next start is performed. Startability at the time can be improved.

FIG. 3 is a schematic circuit diagram of a fuel supply device 30 for an internal combustion engine according to a second embodiment of the present invention, in which the same parts as those in FIG. If this is omitted and explained, this internal combustion engine fuel supply device 3
0 is different from the internal combustion engine fuel supply device 1 (FIG. 1) in that the one-way valve 6 is disposed upstream of the high-pressure fuel pump 5.

That is, the second connection point 3 of the low-pressure passage 19 is located upstream of the first connection point 31 between the bypass passage 20 provided with the bypass valve 11 and the fuel supply passage 13.
2, the one-way valve 6 is arranged between the first connection point 31 and the upstream branch point 17.

The fuel supply device 3 for an internal combustion engine having such a configuration.
0, the pressure control as shown in FIG. 2 can be easily performed as in the case of the internal combustion engine fuel supply device 1 of FIG. When the solenoid valve 10 is opened, the high-pressure part side (downstream side) of the high-pressure fuel pump 5 becomes the target pressure P, so that the prompt operation of the high-pressure fuel pump 5 when the next solenoid valve 10 is closed can be ensured. .

[0037]

As described above, according to the present invention, an electromagnetic valve is provided in parallel between the high pressure side and the low pressure side of the high pressure fuel pump, and the opening and closing of the solenoid valve is controlled to reduce the discharge pressure of the high pressure fuel pump. Since control is performed, useless work of the high-pressure fuel pump can be avoided with a simple configuration, particularly during high-speed operation of the engine.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram of a fuel supply device 1 for an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a graph showing a time change of a fuel pressure in a common rail 7;

FIG. 3 is a schematic circuit diagram of a fuel supply device 30 for an internal combustion engine according to a second embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 fuel supply device for internal combustion engine (first embodiment, FIG. 1) 2 fuel tank 3 low-pressure fuel pump for fuel supply 4 low-pressure regulator 5 high-pressure fuel pump for fuel supply 6 one-way valve 7 common rail 8 pressure sensor 9 Controller 10 Solenoid valve 11 Bypass valve 12 Safety valve 13 Fuel supply passage 14 Internal combustion engine 15 Fuel injection valve 16 Downstream branch point 17 Upstream branch point 18 Relief passage 19 Low pressure passage 20 Bypass passage 21 Common rail side branch point 22 Reflux passage 30 Internal combustion engine Fuel supply device (second embodiment, FIG. 3) 31 first connection point 32 second connection point P target pressure Pc pressure in common rail 7 ΔP between target pressure P and pressure Pc in common rail 7 Differential pressure P1 Upper limit of fuel pressure in common rail 7 P2 Below fuel pressure in common rail 7 Value

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 51/00 F02M 51/00 A F (72) Inventor Koji Aihara 3-13-26 Yayumicho, Higashimatsuyama-shi, Saitama Inside the Zexel Higashi-Matsuyama Plant (72) Eiji Suzuki 3-13-26, Yayumicho, Higashimatsuyama-shi, Saitama Prefecture Inside the Zexel Higashi-Matsuyama Plant (72) Inventor Hiroko Sugaya 3-13-26, Yayumicho, Higashimatsuyama-shi, Saitama Prefecture Zexel Higashimatsuyama Plant

Claims (4)

[Claims] 1. A low-pressure fuel pump for supplying fuel from a fuel tank, and a high-pressure fuel pump for supplying fuel from the low-pressure fuel pump for increasing the pressure of the fuel from the low-pressure fuel pump. A fuel supply device for an internal combustion engine that supplies fuel at a predetermined high pressure to a common rail of the internal combustion engine, wherein a one-way valve connected in series to the high pressure fuel pump in a fuel supply side passage provided with the high pressure fuel pump; An electromagnetic valve provided in a relief passage branched from a pump discharge side of the high-pressure fuel pump and connected to the pump inflow side; a pressure sensor for detecting a pressure in the common rail; and an electromagnetic valve in accordance with a detection signal from the pressure sensor. A fuel supply device for an internal combustion engine, comprising: a controller that controls opening and closing of a valve. 2. The fuel supply device for an internal combustion engine according to claim 1, wherein the one-way valve is provided downstream of the high-pressure fuel pump. 3. The fuel supply device for an internal combustion engine according to claim 1, wherein the one-way valve is provided upstream of the high-pressure fuel pump. 4. The fuel pump according to claim 1, wherein a bypass passage is provided in the fuel supply side passage of the high-pressure fuel pump, and a bypass valve is provided in the bypass passage.
A fuel supply device for an internal combustion engine according to the above.