Adjustment mechanism and headrest

1. An adjustment mechanism for a headrest for a seat, comprising:

a scissor lever, comprising:

at least one first lever arm and at least one second lever arm which can be pivoted relative to one another about a common main pivot axis (S) at a common intersection point (P),

a compensating lever arm is arranged at exactly one lever arm end of each lever arm so as to be pivotable about a compensating pivot axis (AS 1 , AS 2 ) running parallel to the main pivot axis (S), wherein

a free end of each compensating lever arm comprises an attachment structure for attaching the compensating lever arm to a body and

a lever arm end opposite the compensating lever arm of each lever arm comprises an attachment structure for attaching the lever arm to a body

wherein a pivotable arrangement of each compensating lever arm on the associated lever arm is implemented by a pivot bearing, wherein

the pivot bearing comprises a bearing shell which has an opening (O) penetrating the bearing shell and which is arranged on the compensating lever arm or on the lever arm and a bearing body which is arranged on the lever arm or on the compensating lever arm and which corresponds to the bearing shell,

wherein a distance between the bearing surfaces (L 1 , L 2 ) of the bearing body which correspond to the bearing shell is smaller than an internal diameter of the bearing shell and larger than a width (B 2 ) of the opening (O) and

wherein a width (B 1 ) of the bearing body extending at least substantially perpendicular to this distance is smaller than the width (B 2 ) of the opening (O).

2. The adjustment mechanism as claimed in claim 1 , wherein the at least one first lever arm and the at least one second lever arm each have first and second lever arm portions, wherein the first lever arm portions of the at least one first lever arm and the at least one second lever arm have a smaller length than the second lever arm portions of the at least one first lever arm and the at least one second lever arm.

3. The adjustment mechanism as claimed in claim 1 , wherein the lever arms each have two lever arm portions, wherein

a first lever arm portion extends from the intersection point (P) in the direction of the respectively associated compensating lever arm,

a second lever arm portion extends from the intersection point (P) in the direction of a lever arm end remote from the respectively associated compensating lever arm, and

the lever arms are angled back from the intersection point (P) in the opposing direction about the main pivot axis (S), such that an angle (a) which is different from 180° is formed between the longitudinal axes of the lever arm portions.

4. The adjustment mechanism as claimed in claim 1 , wherein

the bearing body is insertable through the opening (O) into the bearing shell in a position of each compensating lever arm relative to the associated lever arm which is outside an operating position of the compensating lever arm and

in the operating position of the compensating lever arm the bearing body is positively mounted in the bearing shell.

5. The adjustment mechanism as claimed in claim 1 , wherein at least one of the lever arms comprises a blocking structure for blocking the scissor lever in different relative pivoted positions of the lever arms to one another.

6. A headrest for a vehicle seat, which has a headrest body, said headrest comprising:

a base element designed for attachment to a seat,

a head rest element with a head rest surface and

an adjustment mechanism which is mechanically coupled to the base element and to the head rest element and is arranged between the base element and the head rest element for longitudinally displacing the head rest element in a first seat direction (X) and in the direction opposite to said first seat direction, wherein the adjustment mechanism comprises:

a scissor lever, comprising:

at least one first lever arm and at least one second lever arm which can be pivoted relative to one another about a common main pivot axis (S) at a common intersection point (P),

a compensating lever arm is arranged at exactly one lever arm end of each lever arm so as to be pivotable about a compensating pivot axis (AS 1 , AS 2 ) running parallel to the main pivot axis (S), wherein

a free end of each compensating lever arm comprises an attachment structure for attaching the compensating lever arm to a body and

a lever arm end opposite the compensating lever arm of each lever arm comprises an attachment structure for attaching the lever arm to a body

wherein a pivotable arrangement of each compensating lever arm on the associated lever arm is implemented by a pivot bearing, wherein

the pivot bearing comprises a bearing shell which has an opening (O) penetrating the bearing shell and which is arranged on the compensating lever arm or on the lever arm and a bearing body which is arranged on the lever arm or on the compensating lever arm and which corresponds to the bearing shell,

wherein a distance between the bearing surfaces (L 1 , L 2 ) of the bearing body which correspond to the bearing shell is smaller than an internal diameter of the bearing shell and larger than a width (B 2 ) of the opening (O) and

wherein a width (B 1 ) of the bearing body extending at least substantially perpendicular to this distance is smaller than the width (B 2 ) of the opening (O).

7. The headrest as claimed in claim 6 , wherein

the free end of the compensating lever arm of the at least one first lever arm is mechanically coupled to the base element,

the free lever arm end of the first lever arm opposing this compensating lever arm is mechanically coupled to the head rest element,

the free end of the compensating lever arm of the at least one second lever arm is mechanically coupled to the head rest element, and

the free lever arm end of the at least one second lever arm opposing this compensating lever arm is mechanically coupled to the base element.

8. The headrest as claimed in claim 7 , wherein

the free end of the compensating lever arm of the at least one first lever arm is mechanically coupled to the head rest element,

the free lever arm end of the at least one first lever arm opposing this compensating lever arm is mechanically coupled to the base element,

the free end of the compensating lever arm of the at least one second lever arm is mechanically coupled to the base element and

the free lever arm end of the at least one second lever arm opposing this compensating lever arm is mechanically coupled to the head rest element.