1. A chain tensioner comprising:
a cylindrical cylinder having open and closed ends;
a cylindrical plunger axially slidably inserted in said cylinder;
a return spring biasing said plunger in a protruding direction from said cylinder, said plunger having an open end inserted in said cylinder and a closed end and formed with an internal thread on the inner circumference; and
a screw rod having an external thread that is in threaded engagement with said internal thread of the plunger;
wherein a portion of said screw rod protruding from said plunger abuts a rod seat provided in said cylinder;
wherein said external thread on the outer circumference of said screw rod is formed by rolling;
wherein a cylindrical intermediate portion having an outer diameter smaller than the diameter of the root of said external thread is provided on a portion of said screw rod protruding from said plunger;
wherein a contact surface to be brought into contact with the rod seat is provided on the axial end face of said intermediate portion; and
wherein said contact surface is a forged contact surface.
2. The chain tensioner according to claim 1 wherein a chamfer tapering from the end of said external thread to said intermediate portion is provided on the outer circumference of said screw rod.
3. The chain tensioner according to claim 1 wherein a spring receiving hole for receiving one end of said return spring is formed in said screw rod and wherein said spring receiving hole is formed by forging.
4. The chain tensioner according to claim 3 wherein the wall thickness of the screw rod from the root of said external thread to said spring receiving hole is not smaller than twice the height of said external thread.
5. The chain tensioner according to claim 3 wherein an oil supply passage is provided in said cylinder for introducing hydraulic oil into a pressure chamber defined by said plunger and said cylinder, wherein a through hole is formed in said rod seat, communicating with said oil supply passage, wherein an oil path hole is formed in said screw rod, communicating said through hole with said spring receiving hole, and wherein said oil path hole is formed by forging.
6. The chain tensioner according to claim 1 wherein a carburized or carbonitrided layer is formed on the surface of said screw rod.
7. The chain tensioner according to claim 6 wherein surface hardness of said carburized or carbonitrided layer is Hv 600 or higher.
8. The chain tensioner according to claim 1 wherein said internal thread comprises a plurality of circumferentially spaced portions.
9. The chain tensioner according to claim 8 wherein said internal thread is formed by pressing, and wherein a pressed recess is formed on the outer circumference of said plunger, corresponding to said internal thread.
10. The chain tensioner according to claim 8 wherein said plurality of circumferentially spaced portions of said internal thread are arranged at equal angular intervals with circumferential spaces defined between adjacent circumferentially spaced portions, and each of said circumferentially spaced portions is shorter in circumferential length than said circumferential spaces.
11. The chain tensioner according to claim 8 wherein surface roughness of said internal thread is not larger than Ra 6.3.
12. The chain tensioner according to claim 8 wherein said plunger is carbonitrided.
13. The chain tensioner according to claim 8 wherein said plurality of circumferentially spaced portions of said internal thread are arranged with circumferential spaces defined between adjacent circumferentially spaced portions, and a radial gap between the outer diameter of said external thread of said screw rod and the diameter of said circumferential spaces is not larger than 0.5 mm.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of encoding and transporting interactive video, comprising the steps of:
receiving a video sequence;
encoding the video sequence into key frames represented by key frame bit sequences and non-key frames represented by non-key frame bit sequences, wherein a number of bits used to encode a frame is a function of an integral distance between the frame and a nearest preceding key frame;
packetizing and transporting the key frame bit sequences over a high quality network channel; and
packetizing and transporting the non-key frame bit sequences over a lower quality network channel.
2. The method of claim 1, wherein the non-key frames exclude bi-directionally predicted frames.
3. The method of claim 1, wherein the non-key frames include predicted frames.
4. The method of claim 1, wherein the key frames are inter-frames.
5. The method of claim 1, wherein the key frames are intra-frames.
6. The method of claim 1, wherein a number of bits used to encode a frame is a function of bandwidth available on a corresponding channel.
7. The method of claim 1, wherein spacing between key frames in the sequence of key frames is a function of bandwidth available on the high quality network channel.
8. The method of claim 1, wherein the high quality network channel is a Quality of Service channel.
9. A system for encoding and transporting interactive video, comprising:
a system encoder for encoding a video stream into key frames represented by key frame bit sequences and non-key frames represented by non-key frame bit sequences, wherein a number of bits used to encode a frame is a function of an integral distance between the frame and a nearest preceding key frame;
a system packetizer coupled to the system encoder for packetizing the key frame bit sequences and the non-key frame bit sequences;
a high quality network channel coupled to the system packetizer for transporting the packetized key frame bit sequences; and
a lower quality network channel coupled to the system packetizer for transporting the packetized non-key frame bit sequences.
10. The system of claim 9, wherein the non-key frames exclude bi-directionally predicted frames.
11. The system of claim 9, wherein the non-key frames include predicted frames.
12. The system of claim 9, wherein the key frames are inter-frames.
13. The system of claim 9, wherein the key frames are intra-frames.
14. The system of claim 9, wherein a number of bits used to encode a frame is a function of bandwidth available on a corresponding channel.
15. The system of claim 9, wherein spacing between key frames in the sequence of key frames is a function of bandwidth available on the high quality network channel.
16. The system of claim 9, wherein the high quality network channel is a Quality of Service channel.
17. A system for encoding and transporting interactive video on multiple-network channels, comprising:
a system encoder for encoding a video stream into key frames and non-key frames, spacing between consecutive key frames based on bandwidth available on the multiple-network channels, and a number of bits used to encode any given frame based on an integral distance between the given frame and a nearest preceding key frame and the bandwidth available on the multiple-network channels;
a system packetizer for packetizing key bits representing the key frames and non-key bits representing the non-key frames, coupled to the system encoder;
a high quality network channel for transporting the packetized key bits, coupled to the system packetizer; and
a network channel of the multiple-network channels for transporting the packetized non-key bits, coupled to the system packetizer.
18. A system for encoding and transporting interactive video on multiple-network channels, comprising:
a means for encoding a video stream into key frames and non-key frames, the spacing between consecutive key frames based on bandwidth available on the multiple-network channels, and a number of bits used to encode any given frame based on an integral distance between the given frame and a nearest preceding key frame and the bandwidth available on the multiple-network channels;
a means for packetizing key bits representing the key frames and the non-key bits representing the non-key frames, coupled to the means for encoding;
a first means for providing high quality transportation of the packetized key bits, coupled to the means for packetizing; and
a second means for providing lower quality transportation of the packetized non-key bits, coupled to the means for packetizing.