Common rail fuel injection system

• US 20060065242A1
• Filed: 09/16/2005
• Published: 03/30/2006
• Est. Priority Date: 09/29/2004
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Nagai, Koichi
• Granted Patent: US 7,204,233 B2
• Time in Patent Office: Days
• US Class Current: 123/458
• CPC Class Codes: F02D 2200/0602 Fuel pressure
• CPC Class Codes: F02D 2250/31 Control of the fuel pressure
• CPC Class Codes: F02D 41/3863 by controlling the flow out of the common rail, e.g. using pressure relief valves
• CPC Class Codes: F02M 2200/505 Adjusting spring tension by sliding spring seats
• CPC Class Codes: F02M 63/0015 electrical, e.g. using solenoid
• CPC Class Codes: F02M 63/0026 using piezoelectric or magnetostrictive actuators
• CPC Class Codes: F02M 63/004 Sliding valves, e.g. spool valves, i.e. whereby the closing member has a sliding movement along a seat for opening and closing
• CPC Class Codes: F02M 63/0225 Fuel-injection apparatus having a common rail feeding several injectors F02M63/0003 takes precedence; Means for varying pressure in common rails; Pumps feeding common rails
• CPC Class Codes: F02M 63/0235 by bleeding fuel pressure

Abstract

A pressure-reduction valve that returns fuel in a common rail to a low-pressure system is such one that a valve-opening pressure of the valve device is changed by an actuator into a target common rail pressure. Thus, when the actual common rail pressure in the common rail exceeds the target common rail pressure, the pressure-reduction valve opens at once. On the contrary, when the actual common rail pressure in the common rail decreases to reach the target common rail pressure, the pressure-reduction valve closes at once. Accordingly, the pressure-reduction valve limits an overshoot and an undershoot of the actual common rail pressure to a minimum without being influenced by a fuel temperature or by detection timings of the common rail pressure sensor.

Claims

1. A common rail fuel injection system for an internal combustion engine comprising:

a high-pressure pump that feeds a high-pressure fuel;

a common rail that accumulates the high-pressure fuel fed by the high-pressure pump;

an injector that injects the high-pressure fuel accumulated in the common rail;

a target common rail pressure calculator that calculates a target common rail pressure in accordance with a driving state of the internal combustion engine;

a valve device that opens when an actual common rail pressure in the common rail exceeds a predetermined valve-opening pressure to flow the high-pressure fuel in the common rail to a low-pressure system; and

a valve-opening pressure changer that changes the valve-opening pressure of the valve device into the target common rail pressure.

2. The common rail fuel injection system according to claim 1, wherein:

the valve device is provided with a fixing member having a high-pressure passage communicated with the common rail, a valve body capable of blocking the high-pressure passage, and a spring urging the valve body to block the high-pressure passage;

the valve-opening pressure changer is provided with an actuator that varies a spring force of the spring, and an actuator controller that controls the actuator to change the valve-opening pressure into the target common rail pressure; and

the valve device and the actuator are integrally provided as a pressure-reduction valve.

3. The common rail fuel injection system according to claim 2, wherein the actuator controller executes an open control of the actuator based on the target common rail pressure.

4. The common rail fuel injection system according to claim 3, wherein the actuator controller is provided with an initialization means that executes:

a minimum pressure-side initialization operation to memorize a minimum pressure control value when the valve device opens or closes in gradually actuating the actuator in a state that the actual common rail pressure equivalent to a minimum target common rail pressure is generated in a memory device; and

a maximum-pressure-side initialization operation to memorize a maximum pressure control value when the valve device opens or closes in gradually actuating the actuator in a state that the actual common rail pressure equivalent to a maximum target common rail pressure is generated in the memory device

at a time prior to shipping, and

the actuator controller calculates an open control value by interpolating between the minimum pressure control value and the maximum pressure control value memorized in the memory device in determining the open control value corresponding to the target common rail pressure in a normal driving time.

5. The common rail fuel injection system according to claim 3, further comprising a common rail pressure sensor that detects a common rail pressure accumulated in the common rail,

wherein the actuator controller is further provided with:

a correction value calculator that determines a correction value for the actuator to eliminate a pressure difference when a detected common rail pressure detected by the common rail pressure sensor differs from the target common rail pressure;

a memorization executor that memorizes the correction value calculated by the correction value calculator in a memory device; and

a correction executer that corrects an open control value applied to the actuator based on the correction value memorized in the memory device.