Rotational structure for rotary knob

1. A rotational structure for a rotary knob attached to a rotary shaft rotatably provided at a device body, the rotational structure providing rotational resistance to the rotary knob, comprising:

an annular sheet interposed between the device body and the rotary knob, wherein the annular sheet includes an annular surface and an axially opposite surface facing axially away from the annular surface;

an attachment member configured to attach a fixed portion of the annular sheet to the device body with the fixed portion being interposed between the attachment member and the device body; and

an annular body-side protrusion provided at the device body, wherein the annular body-side protrusion and the annular surface of the annular sheet are in contact, about a central axis of the rotary knob, thereby forming an imaginary continuous ring of contact on an outside of the fixed portion in a radial direction of the annular sheet, wherein the annular body-side protrusion is configured to warp each of the annular surface and the axially opposite surface toward the rotary knob, and wherein the annular body-side protrusion includes an annular rib in contact with the annular surface of the annular sheet thereby forming the imaginary continuous ring of contact,

wherein the rotary knob contacts the annular sheet on an outside of the annular rib in the radial direction of the annular sheet, such that warpage of the annular sheet biases the rotary knob in a direction away from the device body, and is configured to, in a biased state, slide on the annular sheet such that when the rotary knob rotates the contact between the rotary knob and the annular sheet provides the rotational resistance to the rotary knob.

2. The rotational structure for a rotary knob of claim 1 , wherein the fixed portion of the annular sheet is disposed axially inward toward the device body relative to an outside of the annular sheet along the central axis of the rotary knob.

3. The rotational structure for a rotary knob of claim 1 , wherein the annular sheet is axially interposed between the attachment member and the annular body-side rib along the central axis of the rotary knob.

4. The rotational structure for a rotary knob of claim 1 , wherein the attachment member is spaced from contact with the rotary knob.

5. The rotational structure for a rotary knob of claim 1 , wherein the annular rib uniformly warps the annular sheet toward the rotary knob.

6. The rotational structure for a rotary knob of claim 1 , wherein a portion of the rotary knob is separate from the attachment member and in contact with the annular sheet.

7. The rotational structure for a rotary knob of claim 1 , wherein the rotary knob contacts the annular sheet radially outward of a radially outermost portion of the annular rib.

8. A rotational structure for a rotary knob attached to a rotary shaft rotatably provided at a device body, the rotational structure providing rotational resistance to the rotary knob, comprising:

an annular sheet interposed between the device body and the rotary knob, wherein the annular sheet includes an annular surface and an axially opposite surface facing axially away from the annular surface;

an attachment member configured to attach a fixed portion of the annular sheet to the device body with the fixed portion being interposed between the attachment member and a protrusion of the device body; and

an annular sliding portion provided at the rotary knob, wherein the annular sliding portion and the annular surface of the annular sheet are in contact, about a central axis of the rotary knob, thereby forming an imaginary continuous ring of contact on an outside of the fixed portion in a radial direction of the annular sheet, wherein the annular sliding portion is configured to warp an outside of, including a radially outer end of, each of the annular surface and the axially opposite surface sheet toward the device body, and wherein the annular sliding portion includes an annular rib in contact with the annular surface of the annular sheet thereby forming the imaginary continuous ring of contact, and

the rotary knob is biased in a direction away from the device body in such a manner that the annular sheet contacts the annular rib, and in a biased state, and when the rotary knob rotates the annular rib slides on the annular sheet and the contact between the annular rib and the annular sheet provides the rotational resistance to the rotary knob.

9. The rotational structure for a rotary knob of claim 8 , wherein the fixed portion of the annular sheet is disposed axially outward toward the rotary knob relative to an outside of the annular sheet along the central axis of the rotary knob.

10. The rotational structure for a rotary knob of claim 8 , wherein the fixed portion of the annular sheet is axially interposed between the attachment member and a body-side protrusion provided at the device body along the central axis of the rotary knob.

11. The rotational structure for a rotary knob of claim 8 , wherein the attachment member is spaced from contact with the rotary knob.

12. The rotational structure for a rotary knob of claim 8 , wherein the annular rib uniformly warps the annular sheet toward the device body.

13. The rotational structure for a rotary knob of claim 8 , wherein the entire rotary knob is biased in a direction away from the device body via contact with the annular sheet.

14. A rotational structure for a rotary knob attached to a rotary shaft rotatably provided at a device body, the rotational structure providing rotational resistance to the rotary knob, comprising:

an annular sheet interposed between the device body and the rotary knob, wherein the annular sheet includes an annular surface and an axially opposite surface facing axially away from the annular surface;

an attachment member configured to attach a fixed portion of the annular sheet to the device body with the fixed portion being interposed between the attachment member and the device body, wherein the attachment member is spaced from contact with the rotary knob; and

an annular portion provided at the rotary knob or at the device body, wherein the annular portion and the annular surface of the annular sheet are in contact, about a central axis of the rotary knob, thereby forming an imaginary continuous ring of contact on an outside of the fixed portion in a radial direction of the annular sheet, wherein the annular portion is configured to warp an outside of, including a radially outer end of, each of the annular surface and the axially opposite surface in the same axial direction, and wherein the annular portion includes an annular rib in contact with the annular surface of the annular sheet thereby forming the imaginary continuous ring of contact,

wherein the rotary knob is in contact with the annular sheet on the outside of the fixed portion in the radial direction of the annular sheet, wherein the rotary knob is biased in a direction away from the device body via contact with the annular sheet, and wherein the rotary knob is configured to, in a biased state, slide on the annular sheet such that when the rotary knob rotates the contact between the rotary knob and the annular sheet provides the rotational resistance to the rotary knob.

15. The rotational structure for a rotary knob of claim 14 , wherein the annular rib uniformly warps the annular sheet.

16. The rotational structure for a rotary knob of claim 14 , wherein the fixed portion is interposed axially between the attachment member and the device body.

17. The rotational structure for a rotary knob of claim 14 , wherein the entire rotary knob is biased in a direction away from the device body via contact with the annular sheet.