Internal combustion engine

Patent metadata

Field	Value
Publication number	US-9822672-B2
Application number	US-201414910731-A
Country	US
Kind code	B2
Filing date	Aug 6, 2014
Priority date	Aug 9, 2013
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

An internal combustion engine includes an exhaust valve, a plurality of cams Ca, Cb, and Cc used to drive the exhaust valve, a cam-switching variable valve mechanism that selects a use cam used to drive the exhaust valve out of the plurality of cams Ca, Cb, and Cc, and an electronic control unit that determines whether switching abnormality of the use cam in the variable valve mechanism is present on the basis of a locus M in a predetermined period K which is a period in which the exhaust valve is opened. The locus M is a locus of an in-cylinder pressure changing rate dPc/dθ and is specifically a locus indicating a variation of the in-cylinder pressure changing rate dPc/dθ depending on a crank angle θ.

First claim

The invention claimed is:

1. An internal combustion engine comprising:
a variable valve mechanism including a plurality of cams used to drive an exhaust valve; and
an electronic control unit configured to:
(a) select a use cam, which is a cam used to drive the exhaust valve, out of the plurality of cams, and
(b) determine whether switching abnormality of the use cam is present on the basis of a locus of an in-cylinder pressure changing rate in a predetermined period, the predetermined period being a period in which the exhaust valve is opened,

wherein:
the variable valve mechanism is configured to switch the cams such that a plurality of modes are performed,
the electronic control unit is configured to set the predetermined period to at least one period of a period in which the exhaust valve is opened by switching of the use cam and a period in which the exhaust valve is not opened by the switching of the use cam, when the switching of the use cam is normally performed depending on the modes, and
the electronic control unit is configured to determine whether the switching abnormality is present on the basis of a predetermined item of the locus, and the predetermined item includes at least one of:

(i) presence of an inflection point obtained by operating of the exhaust valve,
(ii) absence of the inflection point,
(iii) value of the inflection point, and
(iv) generating timing of the inflection point.

2. The internal combustion engine according to claim 1 , wherein
the predetermined period is a period after the switching to the use cam has started.

3. The internal combustion engine according to claim 1 , wherein
the electronic control unit is configured to determine that the variable valve mechanism is abnormal when the electronic control unit determines that the switching abnormality is present in at least one of the plurality of modes, and
the electronic control unit is configured to determine that the variable valve mechanism is normal when the electronic control unit determines that the switching abnormality is not present in all of the plurality of modes.

4. The internal combustion engine according to claim 1 , wherein
the variable valve mechanism individually fluctuates depending on cam profiles of the plurality of cams, the variable valve mechanism includes a plurality of fluctuation portions configured to relay dynamic power transmitted from a cam shaft to the exhaust valve, the cam shaft is provided with the plurality of cams, and a plurality of coupling mechanisms configured to connect and disconnect two fluctuation portions out of the plurality of fluctuation portions, and
the electronic control unit is configured to select the cam used to drive the exhaust valve out of at least three cams as the plurality of cams.

5. The internal combustion engine according to claim 4 , wherein
the plurality of cams includes a first cam, a second cam, and a third cam,
the plurality of fluctuation portions include a first fluctuation portion configured to fluctuate using the first cam, a second fluctuation portion configured to fluctuate using the second cam, and a third fluctuation portion configured to fluctuate using the third cam,
the plurality of coupling mechanisms includes a first coupling mechanism and a second coupling mechanism, the first coupling mechanism includes a first lock member that connects and disconnects the first fluctuation portion and the second fluctuation portion, the second coupling mechanism includes a second lock member that connects and disconnects the second fluctuation portion and the third fluctuation portion, the second fluctuation portion is provided with a valve driving portion configured to transmit dynamic power to the exhaust valve,
a valve opening period of the exhaust valve using the first cam includes a valve opening period of the exhaust valve using the second cam,
the cam profile of the first cam and the cam profile of the second cam are set so that an amount of lift of the exhaust valve using the first cam is greater than an amount of lift of the exhaust valve using the second cam,
the cam profile of the third cam is set so as to drive the exhaust valve at timing different from one of the cam profile of the first cam and the cam profile of the second cam, and
the total number of modes is six.

6. The internal combustion engine according to claim 5 , wherein
the electronic control unit is configured to determine whether abnormality of coupling or decoupling performed by at least one of the first lock member and the second lock member is present.

7. The internal combustion engine according to claim 1 , wherein
the electronic control unit is configured to determine an abnormality form of the switching abnormality of the use cam on the basis of the mode and the locus in the predetermined period.

8. The internal combustion engine according to claim 5 , wherein
the electronic control unit is configured to determine an abnormality form of the switching abnormality of the use cam in the variable valve mechanism on the basis of the mode and the locus in the predetermined period,
the modes include a first mode, the first mode is a mode in which a switching form of the use cam is switching from the second cam to the first cam, and
the electronic control unit is configured to determine the abnormality form on the basis of the mode and a first inflection point when the mode is the first mode, and the first inflection point is an inflection point obtained with the operation of the exhaust valve using at least one of the first cam and the second cam in the locus.

9. The internal combustion engine according to claim 8 , wherein
the modes include a second mode, the second mode is a mode in which the switching form of the use cam switches from the second cam to the first and third cams, and
the electronic control unit is configured to determine the abnormality form on the basis of the mode and a second inflection point when the mode is the second mode, and the second inflection point is an inflection point obtained with the operation of the exhaust valve using the third cam in the locus.

10. The internal combustion engine according to claim 9 , wherein
the modes include a third mode, the third mode is a mode in which the switching form of the use cam switches from the second and third cams to the first cam, and
when the mode is the third mode, the electronic control unit is configured to
(A) determine the abnormality form on the basis of the mode and the first inflection point, and
(B) determine the abnormality form on the basis of the mode and the second inflection point.

11. The internal combustion engine according to claim 10 , wherein
a first predetermined inflection point is an inflection point obtained with the operation of the exhaust valve using the first cam when the exhaust valve is driven along the cam profile of the first cam in the locus,
a deviation is a magnitude of a phase difference between the first inflection point and the first predetermined inflection point,
the electronic control unit is configured to determine that the abnormality form is a response delay of switching timing of the use cam generated between the first coupling mechanism and the second coupling mechanism when the mode is the third mode, the first inflection point and the second inflection point are present in the locus, and the deviation is less than a predetermined value.

12. The internal combustion engine according to claim 11 , wherein
the exhaust valve, the plurality of cams, the plurality of fluctuation portions, and the plurality of coupling mechanisms are provided to each of a plurality of cylinders,
the e

Assignees

• Toyota Motor Co Ltd

Inventors

• Haga Hiroyuki
• Miyoshi Yuji

Classifications

• F01L1/267 Primary

  with means for varying the timing or the lift of the valves · CPC title

• F02D41/221

  relating to the failure of actuators or electrically driven elements · CPC title

• F02D35/023

  by determining the cylinder pressure · CPC title

• F02D2041/001

  for engines with variable valve actuation · CPC title

• Y02T10/40

  Engine management systems · CPC title