Valve position detector

• US 20010042566A1
• Filed: 07/17/2001
• Published: 11/22/2001
• Est. Priority Date: 10/20/1998
• Status: Active Grant

• Current Assignee: Fuji Oozx Inc. (Daido Steel Company Limited)
• Original Assignee: Fuji Oozx Inc. (Daido Steel Company Limited)
• Inventors: Adegawa, Makoto, Kobayashi, Haruki, Mori, Akiyoshi
• Granted Patent: US 6,382,246 B2
• Time in Patent Office: Days
• US Class Current: 137/554
• CPC Class Codes: F01L 1/46 Component parts, details, or accessories, not provided for in preceding subgroups
• CPC Class Codes: F01L 2820/045 Valve lift
• CPC Class Codes: F01L 9/20 by electric means
• CPC Class Codes: G01D 5/2403 by moving plates, not forming part of the capacitor itself, e.g. shields
• CPC Class Codes: G01D 5/2412 by varying overlap
• CPC Class Codes: Y10T 137/8242 Electrical

Abstract

A poppet valve moves up and down in a valve operating mechanism in an internal combustion engine. A cylindrical fixed electrode is fixed to a support plate on a cylinder head, and a cylindrical moving electrode is mounted to the lower surface of a valve spring retainer which is mounted to the poppet valve via a cotter. The fixed electrode is connected to a circuit which comprises a variable condenser and a resistance. The valve moves up and down during firing operation of the engine. Thus, variation in electrostatic capacity is detected by the two electrodes, transmitted to a circuit via a lead mounted to the fixed electrode, and converted to a voltage by the circuit, thereby detecting valve position exactly.

Claims

1. A valve position detector for detecting position of a poppet valve driven by a valve operating mechanism, a valve stem of said valve being slidably supported by a cylinder head, said detector comprising:

a variable capacity electrode of an electrostatic capacity sensor for detecting position of said valve by detecting variation in electrostatic capacity when said valve is moved, said variable capacity electrode being provided between said cylinder head or a stationary member integrally formed therewith, and said valve or a member which follows said valve.

2. A valve position detector as claimed in

claim 1

wherein said variable capacity electrode comprises a cylindrical fixed electrode which surrounds a valve stem of said valve concentrically with said valve stem and is mounted to a support plate fixed to the cylinder head, and a cylindrical moving electrode mounted to a valve spring retainer fixed to said valve, said fixed electrode being partially overlapped on said moving electrode to form an opposing area varying form.

3. A valve position detector as claimed in

claim 2

wherein said moving electrode is connected to a lead which is connected to a measuring circuit which comprises a variable condenser, a coil, and a high frequency power source connected to a resistance in series, in parallel to convert variation in electrostatic capacity to a voltage which is amplified by an amplifier to determine position of the valve.

4. A valve position detector as claimed in

claim 3

wherein said moving electrode is made as earth potential.

5. A valve position detector as claimed in

claim 2

wherein a tubular cover is mounted between the valve spring retainer and the fixed electrode to prevent foreign substance from invading between said two electrodes.

6. A valve position detector as claimed in

claim 2

wherein a tubular cover is mounted between the fixed and moving electrodes, an inner circumferential surface of said cover being elastically pressed on an outer circumferential surface of said moving electrode to prevent foreign substance from invading between said two electrodes.

7. A valve position detector as claimed in

claim 1

wherein an inner fixed electrode is mounted to the cylinder head, an outer fixed electrode being mounted to a support plate which is fixed to the cylinder head, a dielectric being inserted between said fixed electrodes and mounted to a valve spring retainer to form an inductivity varying electrode.

8. A valve position detector as claimed in

claim 1

wherein an electromagnetic actuator is provided to move the valve up and down, an external thread being formed at a lower end of a drive shaft of said electromagnetic actuator, an external thread being formed at an upper end of the valve, said two external threads being connected by a connecting member, said variable capacity electrode comprising a fixed electrode fixed to a support plate on the cylinder block and a moving electrode mounted to the valve to form an electrostatic capacity displacement sensor.

11. A valve position detector as claimed in

claim 1

wherein an electromagnetic actuator is provided over said variable capacity electrode which comprises inner and outer fixed electrodes fixed to a lower surface of said electromagnetic actuator, and a moving electrode mounted to an upper surface of a valve spring retainer which is mounted to the valve, said moving electrode being inserted to move vertically between said inner and outer fixed electrodes.

12. A valve position detector as claimed in

claim 1

wherein said valve is driven by an electromagnetic actuator over said valve, said variable capacity electrode comprising a fixed electrode which is mounted on an inner surface of an electrode holder, and a moving electrode mounted to a drive shaft of said electromagnetic actuator, said moving electrode being movable in said fixed electrode to form an opposing area varying type electrode.

13. A valve position detector as claimed in

claim 1

wherein said variable capacity electrode comprises a frustum-shaped fixed electrode mounted to a support plate on the cylinder head and a frustum-shaped moving electrode mounted to a valve stem of the valve over said fixed electrode.

9. A valve position detector as claimed 8 wherein a bellows-like cover is mounted between an upper end outer circumferential surface of the fixed electrode and an upper end of the moving electrode to prevent foreign substance from invading between the two electrodes.

10. A valve position detector as claimed 7 wherein an electromagnetic actuator is provided over the variable capacity electrode.