Method and system for operating a cam-driven pump

Abstract

A method for automatically operating a cam-driven pump is disclosed. The pump is monitored to determine whether a specified detachment condition or potential detachment of an actuator of the pump from a driving cam is occurring. The pump is operated in a minimal pressure holding mode to provide a minimal pressure within a working chamber of the pump so as to bias the actuator towards the cam if it is determined that the detachment condition is occurring.

Claims

1. A method for automatically operating a cam-driven pump comprising: determining whether a detachment condition indicating detachment of an actuator of the pump from a driving cam is fulfilled; and operating the pump in a minimal pressure holding mode to provide a minimal pressure within a working chamber of the pump so as to bias the actuator towards the cam when it is determined that the specific detachment condition is fulfilled.

2. The method according to claim 1, wherein operating the pump in a minimal pressure holding mode comprises controlling a valve arrangement in fluid communication with the pump in the minimal pressure holding mode to provide the minimal pressure within the working chamber of the pump so as to bias the actuator towards the cam when it is determined that the detachment condition is fulfilled.

3. The method according to claim 2, wherein the minimal pressure is specified to provide a biasing force acting on the actuator towards the driving cam that is at least the lesser of 2% of a biasing force of a spring biasing the actuator towards the driving cam and 500 N.

4. The method according to claim 2, further comprising: controlling an inlet valve in fluid communication with an inlet port of the pump to provide a specified intake quantity; and controlling an outlet valve in fluid communication with an outlet port of the pump to provide the minimal pressure when fulfillment of the detachment condition is determined.

5. The method according to claim 4, wherein at least one of the minimal pressure within the working chamber and the intake quantity is specified based on a speed of the driving cam.

6. The method according to claim 5, wherein at least one of a first minimal pressure within the working chamber and a first intake quantity is specified for a first speed of the driving cam and at least one of a larger second minimal pressure within the working chamber and a larger second intake quantity is specified for a larger second speed of the cam.

7. The method according to claim 4, wherein the outlet valve communicates with the outlet port via a reservoir, the method further comprising controlling the outlet valve to provide the minimal pressure within the reservoir when fulfillment of the detachment condition is determined.

8. The method according to claim 7, further comprising controlling the outlet valve to provide a specified pressure state within the reservoir when the detachment condition indicates a non-detachment condition of unlikely detachment of said actuator from said cam is fulfilled.

9. The method according to claim 1, further comprising determining the detachment condition based on a workload of a machine feed by the pump.

10. The method according to claim 9, further comprising determining the detachment condition when the machine is cut-off.

11. The method according to claim 1, further comprising determining the detachment condition based on a speed of the driving cam.

12. The method according to claim 11, further comprising determining the detachment condition when a speed of the cam exceeds a predetermined threshold.

13. A non-transitory computer readable medium comprising source code executable on a processor for carrying out the method according to claim 1.

14. A control system for automatically operating a cam-driven pump, comprising a controller configured to: determine whether a detachment condition indicating detachment of an actuator of the pump from a driving cam is fulfilled; and operate the pump in a minimal pressure holding mode to provide a minimal pressure within a working chamber of the pump so as to bias the actuator towards the cam when a specific detachment condition is fulfilled.

15. A pump arrangement comprising: a cam-driven pump having a working chamber, an inlet port and an outlet port in fluid communication with the working chamber, a driving cam and an actuator operably coupled to the driving cam for displacement in the working chamber; a valve arrangement having an inlet valve in fluid communication with the inlet port and an outlet valve in fluid communication with the outlet port; and a controller configured to: determine whether a detachment condition indicating detachment of the actuator from the driving cam; and operate the pump in a minimal pressure holding mode to provide a minimal pressure within the working chamber for biasing the actuator towards the driving cam when a specific detachment condition is fulfilled.

16. An internal combustion engine comprising an internal combustion engine and a pump arrangement according to claim 15, wherein the cam-driven pump is configured to feed the a common fuel rail of the internal combustion engine.

17. A vehicle comprising an internal combustion engine comprising an internal combustion engine according to claim 16.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements.

(2) FIG. 1 depicts apart of an internal combustion engine arrangement with a pump arrangement including a control system according to an embodiment of the present disclosure; and

(3) FIG. 2 is a flowchart illustrating a method according to an embodiment of the present disclosure, the method being implemented by a computer program or a computer program module and carried out by the control system.

DETAILED DESCRIPTION

(4) The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description.

(5) FIG. 1 shows a part of an internal combustion engine arrangement with an internal combustion engine including injectors 51 and a pump arrangement including a control system in form of an ECU 1 according to an embodiment of the present disclosure.

(6) The pump arrangement includes a cam-driven high-pressure fuel pump of a common rail system, including a working chamber 20 with an inlet port 21 and an outlet port 22, and an actuator 23 having a plunger 24 and a cam-follower 25 driven by a cam 26 which itself is driven by a camshaft of the internal combustion engine (not shown). Actuator 23 is permanently biased towards cam 26 by a biasing means in form of a spring 27.

(7) The pump arrangement further includes a valve arrangement including an inlet valve in form of a DIV 3 in fluid communication with inlet port 21 and an outlet valve in form of a PRV 4 of the common rail system in fluid communication with outlet port 22 via a common rail 50 which both are automatically controlled by ECU 1.

(8) The common rail system of the internal combustion engine includes the common rail 50 for feeding the injectors 51 of the internal combustion engine and the PRV 4.

(9) ECU 1 automatically controls valve arrangement 3, 4 according to a method according to an embodiment of the present disclosure, the method being implemented by a computer program or a computer program module and described in further detail with reference to FIG. 2.

(10) During normal non-cut off condition of the internal combustion engine ECU 1 controls or provides a pressure within common rail 50 respectively by controlling DIV 3 and/or PRV 4 in a step S5.

(11) ECU 1 regularly proceeds to a step S10. In step S10 ECU 1 determines if the internal combustion engine is cut-off or not.

(12) If ECU 1 determines that the internal combustion engine is not cut-off (S10: N), it returns to step S5.

(13) If ECU 1 determines that the internal combustion engine is cut-off (S10: Y), it proceeds with step 320 in which it determines if a rotating speed of cam 26 exceeds a predetermined threshold or not. If it determines that the cam speed does not exceed the predetermined threshold (S20: N), ECU 1 also returns to step S5

(14) If ECU 1 determines that the cam speed exceeds the predetermined threshold (S20: Y), ECU 1 determines that a specified detachment condition of potential detachment of actuator 23 from driving cam 26 is fulfilled and proceeds with step S30.

(15) In step S30 ECU 1 specifies an intake quantity for DIV 3 and an outlet pressure for PRV 4 based on the cam speed. The outlet pressure for PRV 4 corresponds to a (pre)specified minimal pressure state within working chamber 20.

(16) In an exemplary embodiment the intake quantity may be specified as being 50 mm.sup.3 and/or the outlet or minimal pressure may be specified as being 500 bar if the cam speed is within a range between the predetermined threshold and the predetermined threshold plus 499 rounds per minute [rpm].

(17) In the exemplary embodiment the intake quantity may be specified as being increased by 5 mm.sup.3 and/or the outlet pressure may be specified as being increased by 50 bar for every further 500 rpm of cam speed beyond the predetermined threshold. In other words the intake quantity may be specified as being 55 mm.sup.3 and/or the outlet pressure may be specified as being 550 bar if the cam speed is within a range between the predetermined threshold plus 500 rpm and the predetermined threshold plus 999 rpm, the intake quantity may be specified as being 60 mm.sup.3 and/or the outlet pressure may be specified as being 600 bar if the cam speed is within a range between the predetermined threshold plus 1000 rpm and the predetermined threshold plus 1499 rpm and so forth.

(18) ECU 1 then controls DIV 3 to provide the specified intake quantity and PRV 4 to provide the specified outlet or minimal pressure in step S30, thereby controlling the valve arrangement 3, 4 to provide a minimal pressure within working chamber 20 for biasing actuator 23 towards cam 26.

(19) ECU 1 then proceeds to steps S40, S50 which correspond to steps S10, S20 respectively. As long as ECU 1 determines that the internal combustion engine is still cut-off (S40: Y) and the cam speed still exceeds the predetermined threshold (S50: Y), ECU 1 returns to step S30 wherein it again specifies the intake quantity and outlet pressure based on an actualized cam speed.

(20) If ECU 1 determines that either the internal combustion engine is no longer cut-off (S40: N) or the cam speed does not exceed the predetermined threshold any more (S50: N), ECU 1 proceeds with step S60.

(21) In the step S60 ECU 1 controls outlet valve 4 so as to quickly provide a specified pressure state within common rail 50 based on a pressure demand of the internal combustion engine since a non-detachment condition is fulfilled (S40 OR S50: N). ECU 1 then returns to step S5, i.e. into normal non-cut off operation.

(22) According to another embodiment depicted by a broken line in FIG. 2, the non-detachment condition may only be fulfilled if the internal combustion engine is no longer cut-off (S40: N). In other words, if ECU 1 determines that the internal combustion engine is still cut-off (S40: Y) it returns to step S30. In this other embodiment ECU 1 therefore returns to step S5 directly, i.e. without carrying out step S60, if it determines during cut-off condition (S40: Y) that the cam speed does not exceed the predetermined threshold any more (S20: N).

(23) The ECU 1 may include a digital central processing unit (CPU) or processor in communication with a memory system and an interface bus. Instead of an ECU, the system may have a different type of processor to provide the electronic logic, e.g. an embedded controller, an onboard computer, or any processing module that might be deployed in the vehicle. The CPU is configured to execute instructions stored as a program in the memory system, and send and receive signals to and from the interface bus. The memory system may include various storage types including optical storage, magnetic storage, solid state storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals to and from the various sensors and control devices. The program may embody the methods disclosed herein, allowing the CPU to execute the steps of such control methods.

(24) The program stored in the memory system is transmitted from outside via a cable or in a wireless fashion. Outside the system it is normally visible as a computer program product, which is also called transient or non-transient computer readable medium or machine readable medium in the art, and which should be understood to be a computer program code residing on a carrier, the carrier preferably being either transitory or non-transitory in nature with the consequence that the computer program product can be regarded to be transitory or non-transitory in nature.

(25) An example of a transitory computer program product is a signal, e.g. an electromagnetic signal such as an optical signal, which is a transitory carrier for the computer program code. Carrying such computer program code can be achieved by modulating the signal by a conventional modulation technique such as QPSK for digital data, such that binary data representing the computer program code is impressed on the transitory electromagnetic signal. Such signals are e.g. made use of when transmitting computer program code in a wireless fashion via a WiFi connection to a laptop.

(26) In case of a non-transitory computer program product the computer program code is embodied in a tangible storage medium. The storage medium is then the non-transitory carrier mentioned above, such that the computer program code is permanently or non-permanently stored in a retrievable way in or on this storage medium. The storage medium can be of conventional type known in computer technology such as a flash memory, an Asic, a CD or the like.

(27) While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.