# US 7,610,901 B2 · Method for detecting the opening of a passive pressure control valve

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- Number: US 7,610,901 B2
- Document ID: US7610901B2
- Status: Granted
- Kind: B2
- Application number: 11/975,585
- Filed: 2007-10-19
- Published: 2008-04-24
- Granted: 2009-11-03
- Earliest claimed: 2006-10-19
- Assignees: MTU Friedrichshafen GmbH
- Inventors: Martin Bucher; Armin Dölker; Volker Wachter; Uwe Kosiedowski
- Web page: https://patentgrep.com/patent/US7610901B2

## CPC

- F02M 63/025: {from the common rail}
- F02D 41/221: {relating to the failure of actuators or electrically driven elements}
- F02D 41/3863: {by controlling the flow out of the common rail, e.g. using pressure relief valves}
- F02D 2041/224: {Diagnosis of the fuel system}
- F02M 59/34: by throttling of passages to pumping elements or of overflow passages {, e.g. throttling by means of a pressure-controlled sliding valve having liquid stop or abutment}
- F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W)

## Abstract

A method for detecting the opening of a passive pressure control valve, which conducts fuel from a common rail system back to a fuel tank, in which the rail pressure (pCR) is automatically controlled by calculating a correcting variable for acting on the controlled system from a rail pressure control deviation via a pressure controller, and in which, starting from a steady-state rail pressure in normal operation, a load reduction is detected when the rail pressure exceeds a first limit. Opening of the pressure control valve is detected after the first limit is exceeded if a steady-state operating state is subsequently detected again, and if a characteristic of the closed-loop control system deviates significantly from a reference value.

## Claims

### Claim 1

A method for detecting opening of a passive pressure control valve, which conducts fuel from a common rail system back to a fuel tank, comprising the steps of: automatically controlling rail pressure (pCR) by calculating a correcting variable for acting on a controlled system from a rail pressure control deviation (ep) via a pressure controller; detecting, starting from a steady-state rail pressure in normal operation, a load reduction when the rail pressure (pCR) exceeds a first limit (GW1); and detecting opening of a pressure control valve after the first limit (GW1) is exceeded if a steady-state operating state is subsequently detected again, and if a characteristic of a closed-loop control system deviates significantly from a reference value (REF).

### Claim 2 (depends on 1)

The method in accordance with claim 1, including reading out the reference value (REF) from a leakage input-output map as a function of a current operating point.

### Claim 3 (depends on 2)

The method in accordance with claim 2, including determining the current operating point by engine speed (nMOT) and a set injection quantity (Q(SW)) or, alternatively, a set torque (M(SW)).

### Claim 4 (depends on 1)

The method in accordance with claim 1, including determining the characteristic of the closed-loop control system from an I component (V(I)) of the pressure controller or from an actuating variable derived from the correcting variable of the pressure controller.

### Claim 5 (depends on 4)

The method in accordance with claim 4, wherein the actuating variable is a set volume flow (VSL), a set electric current (iSL), or a PWM signal (PWM).

### Claim 6 (depends on 5)

The method in accordance with claim 5, wherein a significant deviation is present when the I component (V(I)) of the pressure controller or the set volume flow (VSL) becomes greater than the reference value (REF).

### Claim 7 (depends on 5)

The method in accordance with claim 5, wherein significant deviation is present when the set electric current (iSL) or the PWM signal (PWM) becomes smaller than the reference value (REF).

### Claim 8 (depends on 2)

A method in accordance with claim 2, including determining the reference value (REF) stored in the leakage input-output map from one of the characteristics of the closed-loop control system in normal operation.