Image forming apparatus

An image forming apparatus comprising:

• medium-conveying means for attracting and conveying a print medium having a characteristic with which cockling is produced by application of liquid droplets;
• attracting means for attracting the print medium to the medium-conveying means;
• and
• a first liquid ejecting head for first providing liquid droplets on the upstream side in the direction of conveyance of the print medium, and a second liquid ejecting head for later providing liquid droplets on the downstream side, said first and second ejecting heads being separated from the print medium with a gap,
• wherein for a slope α and an intercept β obtained from a tangential line to a curved line which the tangential line passes through an x-y reference point (1, γ) obtained from the curved line in an x-y coordinate system, the curved line representing the height (y) mm of the cockling in response to the time (x) (second) elapsed since the application of liquid droplets onto the print medium, a minimum gap H (mm) in the gap, the length L (mm) of an ejecting head existence region extending from an ejecting portion of said first liquid ejecting head up to an end of said second liquid ejecting head, and a conveyance speed V (mm/sec) of the print medium satisfy an inequality:
• H>α(L/V)+β, with H≧γ and α+β=γ.

An image forming apparatus comprising:

• medium-conveyance means having a conveyance surface for moving at a speed V along a conveyance reference surface to convey a print medium;
• and
• at least two liquid ejecting heads disposed at a distance in the movement direction of the conveyance surface and respectively having an ejection opening surface through which a plurality of ejection openings are opened for ejecting a liquid, said image forming apparatus forming an image by ejecting the liquid onto the surface of the print medium from the ejection opening of said liquid ejecting head disposed oppositely to the conveyance surface,
• wherein an interval is defined between the ejection opening surface of an arbitrary second liquid ejecting head located downstream of a first liquid ejecting head located upstream in the movement direction of the conveyance surface for firstly ejecting the liquid to the print medium and the conveyance surface,
• the inverval is set smaller than the total sum of the maximum value of variations of the height of the conveyance surface with respect to the conveyance reference surface, the maximum error amount of the thickness of the print medium and the maximum amount of relief from the conveyance surface, and the maximum height HCX of cockling produced on the print medium owing to the liquid ejected onto the surface of the print medium, and
• the interval is set to be larger than the total sum of the maximum value of variations of the height of the conveyance surface with respect to the conveyance reference surface, the maximum error amount of the thickness of the print medium and the maximum amount of relief from the conveyance surface, and the height HC1 of the cockling produced on the print medium after the elapse of predetermined time TC1 since first ejection of the liquid to the print medium from said first liquid ejecting head, and
• wherein a distance L between said first liquid ejecting head and said second liquid ejecting head is set shorter than (V/VCX)HCX when the maximum value of the growth speed of the cockling is represented by VCX, and further
• the predetermined time TC1 being L/V.

An image forming apparatus comprising:

• medium-conveyance means having a conveyance surface that moves at a speed V along a conveyance reference surface to convey a print medium;
• and
• at least two liquid ejecting heads each having ejection opening surfaces through which a plurality of ejection openings are disposed, separated in the movement direction of the conveyance surface and being opened to eject a liquid, whereby the liquid is ejected to the surface of the print medium from the ejection openings of said liquid ejecting head facing the conveyance surface to form an image,
• wherein a gap is defined between the ejection opening surface of an arbitrary second liquid ejecting head located on a more downstream side than a first liquid ejecting head located on an upstream side in the movement direction of the conveyance surface for firstly ejecting the liquid to the print medium and the conveyance surface.
• the gap is set smaller than the total sum of the maximum value of variations of the height of the conveyance surface with respect to the conveyance reference surface, the maximum error amount of the thickness of the print medium and the maximum amount of relief from the conveyance surface, and the cockling height HC2when the growth speed is maximum of the cockling after the liquid is firstly ejected to the print medium from said first liquid ejecting head, and
• the gap is set larger than the total sum of the maximum of variations of the height of the conveyance surface with respect to the conveyance reference surface, the maximum error amount of the thickness of the print medium and the maximum amount of relief from the conveyance surface, and the height HC1 of the cockling produced on the print medium after the elapse of a predetermined time TC1 since the liquid is firstly ejected to the print medium from said first liquid ejecting head, and
• wherein a distance L between said first liquid ejecting head and said second liquid ejecting head is set to be shorter than (V/VCX) when the maximum value of the growth speed of the cockling is represented by VCX, and further
• the predetermined time TC1 being L/V.

An image forming apparatus comprising:

• medium-conveyance means having a conveyance surface moved at a speed V along a conveyance reference surface to convey a print medium;
• and
• at least two liquid ejecting heads having ejection opening surfaces which are disposed separated from each other in the movement direction of the conveyance surface and through which a plurality of ejection openings are opened, each for ejecting a liquid, whereby the liquid is ejected from the ejection openings of said liquid ejecting head facing the conveyance surface onto the surface of the print medium to form an image,
• wherein a gap is defined between the conveyance surface and the ejection opening surface of an arbitrary second liquid ejecting head located more downstream than a first liquid ejecting head located on the upstream side in the movement direction of the conveyance surface for firstly ejecting the liquid onto the print medium,
• the gap is set smaller than the total sum of the maximum value of variations of the height of the conveyance surface with respect to the conveyance reference surface, the maximum error amount of the thickness of the print medium and the maximum amount of relief from the conveyance surface, and a cockling height HC3 at a time TC3 which is calculated on the basis of the maximum value VCX of the growth speed of the cockling produced on the print medium since the liquid is firstly ejected onto the print medium through said first liquid ejecting head and when a difference between the cockling height HC3 and the actual cockling height is maximum, and
• the gap is set larger than the total sum of the maximum value of variations of the height of the conveyance surface with respect to the conveyance reference surface, the maximum error amount of the thickness of the print medium and the maximum amount of relief from the conveyance surface, and a cockling height HC1 produced on the print medium after the passage of predetermined time TC1 since the liquid is firstly ejected onto the print medium by said first liquid ejecting head, and
• wherein a distance L between said first liquid ejecting head and said second liquid ejecting head is set shorter than V·TC3, and
• the predetermined time TC1 being L/V.

An image forming apparatus comprising:

• medium-conveyance means having a conveyance surface;
• and
• at least two liquid ejecting heads having ejection opening surfaces which are disposed separated from each other in the movement direction of the conveyance surface and through which a plurality of ejection openings are opened for ejecting a liquid, whereby the liquid is ejected onto the surface of the print medium from the ejection openings of said liquid ejecting heads facing the conveyance surface to form an image,
• wherein an interval is defined between the conveyance surface and the ejection opening surface of an arbitrary second liquid ejecting head located downstream of a first liquid ejecting head which is located on the upstream side in the movement direction of the conveyance surface,
• the interval is set smaller than the total of the maximum of variations of the height of the conveyance surface with respect to the conveyance reference surface, the maximum error amount of the thickness of the print medium and the maximum amount of relief from the conveyance surface, and the maximum height HCX of the cockling produced on the print medium owing to the liquid ejected on the print medium, and
• the interval is set larger than the total sum of the maximum of variations of the height of the conveyance surface with respect to the conveyance reference surface, the maximum error amount of the thickness of the print medium and the maximum amount of relief from the conveyance surface, and the height HC4 of the cockling after the passage of predetermined time TC1 which is calculated on the basis of the maximum value VCX of the growth speed of the cockling and since the liquid is firstly ejected to the print medium by said first liquid ejecting head, and
• wherein a distance between the first liquid ejecting head and said second liquid ejecting head is set shorter than (V/VCX)HCX, and further
• the predetermined time TC1 being L/V.