JP2000203009A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus in which damage onto the body of apparatus or a recording head is reduced while enhancing carrying performance and reliability. SOLUTION: An imaging apparatus for forming an image by carrying a recording medium comprises means 8 for recording on a recording medium P, a spur 14 turning while touching the recording medium P being carried and displaceable through contact therewith, and a detecting means, e.g. an optical sensor or microswitch 21, for detecting at least one of rotation or displacement of the spur 14 wherein carriage and recording of the recording medium P are controlled depending on the detection results of the detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for conveying a recording medium to form an image, and more particularly to an image forming apparatus capable of detecting conveyance abnormality of a recording medium and controlling conveyance and recording.

[0002]

2. Description of the Related Art Conventionally, in an ink jet recording apparatus, an interval between a recording medium and a recording head is set to be extremely small in order to increase the landing accuracy of ink. In order to perform stable printing with this ink jet printing apparatus, the effect of wrinkles and wavy deformation (hereinafter referred to as “cockling”) generated when ink is ejected on a printing medium is eliminated as much as possible. It is necessary to keep the distance between the surface of the recording medium and the recording head unchanged. In addition, it is necessary to prevent the floating of the paper from the platen toward the recording head even on a recording medium which is originally curled due to moisture or the like.

For this purpose, conventionally, for example, at a portion upstream of the recording head in the transport direction of the recording medium with respect to the recording head, the recording medium is pressed against the platen by a pressing member to prevent floating, or a plurality of small-diameter holes are provided in the platen. A structure in which the recording medium is brought into close contact with the platen by suction force generated by using the negative pressure generating means to prevent floating, or the recording medium is attracted to a belt-shaped or suction plate-shaped member by electrostatic attraction. And the like.

Further, as a means for detecting a transport abnormality, that is, a jam (paper jam), an optical or lever type jam detection sensor is provided in the transport path, and the apparatus is stopped when an abnormality occurs. Used.

[0005]

However, even with these means, it is difficult to completely eliminate the above-mentioned problems, and it is difficult to prevent image jams due to jamming due to inability to carry, abnormal conveyance due to jamming of a recording medium, and image defects. Occasionally, an image defect or the like due to contact with the recording head has occurred.

In a configuration such as the above-described conventional example, the ink discharge ports are arranged over the entire width of the recording medium in a direction intersecting the conveying direction of the recording medium arranged in the recording area or the recording medium arranged in the recording area. In a so-called full-line type ink jet recording head, cockling and floating of the recording medium occur remarkably.

[0007] In particular, when the recorded image has a high density, a large amount of ink is ejected onto the recording medium, and as a result, head rubbing due to large cockling, sometimes jamming, and poor conveyance (uneven feeding, image irregularity). Rubbing) may occur. As a result, the recording medium may come into contact with the recording head to disturb the image, cause clogging of the head, color mixing of ink, and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned various problems of the prior art, and an object of the present invention is to reduce damage to an apparatus body and a recording head.
An object of the present invention is to provide an image forming apparatus with improved transport performance and reliability.

[0009]

A typical configuration according to the present invention for achieving the above object is a recording means for recording on a recording medium in an image forming apparatus for conveying a recording medium to form an image. A rotating member that rotates in contact with the recording medium to be conveyed, and that can be displaced by contacting the recording medium; and a detecting unit that detects at least one of rotation and displacement of the rotating member. The conveyance and recording of the recording medium are controlled in accordance with the detection result.

[0010] In the above-mentioned configuration, the abnormal state of the recording medium is detected by detecting the state of the rotating member that rotates and shifts in contact with the recording medium, and the recording is stopped. Damage to the means can be prevented immediately.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be specifically described with reference to the drawings.

[First Embodiment] An image forming apparatus according to a first embodiment will be described with reference to FIGS. still,
FIG. 1 is a cross-sectional view of a main part of a recording unit, FIG. 2 is an explanatory diagram of a spur arrangement viewed from a width direction of a recording medium, FIG. 3 is an explanatory diagram of a case where a floating recording medium is conveyed, and FIG. FIG. 5 is an explanatory diagram of a state when a recording medium is jammed, and FIG. 5 is an explanatory diagram of the entire image forming apparatus.

{Overall Configuration} First, the overall configuration of an image forming apparatus will be described with reference to FIG. 5. This apparatus is a copier that records information read by a scanner unit A by a printer unit B. The scanner unit A places the original G on the original placing glass 1.
The document information is optically read by scanning the reading means 2 in the direction of arrow a, and the information is photoelectrically converted and transmitted to the printer unit B.

The printer unit B feeds the recording medium P loaded in the cassette 3 mounted below by the feed roller 4 and separates and feeds the recording medium P one by one by the separation roller pair 5. The recording medium P fed along the conveying path 6 is conveyed to the recording means 8 by the conveying roller pair 7, where the reading is performed while being conveyed by the conveying belt 9 wrapped around the rollers 9 a and rotating in the direction of arrow b. Full-color recording is performed according to the information, and the sheet is discharged to a discharge tray 11 by a discharge roller 10.

The recording means 8 has four ink jet recording heads 8C, 8M, 8Y, and 8B capable of ejecting inks of cyan, magenta, yellow, and black, respectively, arranged in the recording medium transport direction in order. A color image is formed on the recording medium P by discharging the color ink from each of the recording heads 8C, 8M, 8Y, 8B based on.

For this purpose, the recording head is provided with a fine liquid discharge port (orifice), a liquid path, an energy acting portion provided in a part of the liquid path, and a droplet forming energy acting on the liquid in the acting portion. It has energy generating means for generating energy.

As an energy generating means for generating such energy, a recording method using an electromechanical transducer such as a piezo element or the like, an electromagnetic wave such as a laser is irradiated to generate heat, and a droplet is discharged by the action of the heat. There are a recording method using an energy generating means, and a recording method using an energy generating means for discharging a liquid by heating a liquid by an electrothermal converter such as a heating element having a heating resistor.

Among them, a recording head used in an ink jet recording method in which a liquid is discharged by thermal energy has a liquid discharge port (orifice) for discharging a recording droplet to form a discharge droplet at a high density. Since they can be arranged, high-resolution recording can be performed. Among them, a recording head using an electrothermal transducer as an energy generating means is advantageous because it can be easily made compact, easily mounted at a high density, and inexpensively manufactured.

The recording head of this embodiment is a so-called full-line type recording head having an ink discharge port in the whole area in the width direction of the recording medium. The apparatus is configured so that recording is performed by discharging ink from the discharge port by energizing, and using the film boiling generated in the ink by the thermal energy to grow and shrink bubbles generated in the ink.

A recovery cap 12 protects the ink ejection sections of the recording heads 8C, 8M, 8Y, 8B during non-printing, and maintains a state in which normal ink ejection is possible.

{Conveying State Detecting Means of Recording Medium} The image forming apparatus of the present embodiment is configured so that the conveying state of the recording medium P can be detected by a rotating member. More specifically, as shown in FIG. 1, the fed recording medium P is adsorbed on the conveyor belt 9 by an adsorption roller 13 and sequentially sent to the recording heads 8C, 8M, 8Y, and 8B. On the upstream side of the recording heads 8C, 8M, 8Y, and 8B in the recording medium transport direction, spurs 14 as rotating members are provided so as to contact the recording medium P to be transported and to be driven to rotate. The spur 14 has a large number of teeth 14a protruding from the outer periphery, and the tip of the teeth 14a contacts the recording medium P, so that the contact area with the recording medium P is small. This is a rotating body that does not disturb the ink image even when it contacts the side, and is provided rotatably in the width direction of the recording medium P (a direction intersecting with the recording medium transport direction) as shown in FIG. A plurality (five in the present embodiment) is fixed to the shaft 15.

As shown in FIG. 2, an encoder plate 16 is fixed to one end of the shaft 15, and an optical pattern (not shown) provided on the encoder plate 16 is detected by an optical sensor 17. , The rotational speed of the spur 14 is detected.
That is, when the recording medium P is normally conveyed,
Since the encoder 14 keeps a constant rotation with it, the encoder detection signal becomes a pulse at a constant interval, and when this pulse is no longer constant, it means that a transport abnormality has occurred.

As shown in FIG. 1, the spurs 14 are each integrally held rotatably by a holder 18, and each of the holders 18 is attached to the apparatus main body so as to be swingable about a shaft 19. The holder 18 is urged by a tension spring 20 so that the spur 14 comes into contact with the recording medium P to be conveyed at a constant pressure.

A micro switch 21 as a holder swing detecting means is arranged near the holder 18 so that when the swing amount of the holder 18 exceeds a certain value, the micro switch 21 is pressed to turn on the detection signal. Has become. Accordingly, when the floating of the recording medium P becomes equal to or more than a certain value, the spur 14 that comes into contact with the spur shifts in accordance with the floating, so that it can be detected by the microswitch 21.

Next, the operation when the recording medium is transported in the above configuration will be described. The recording medium P is fed according to the recording operation, and is transported by the transport belt 9. At this time, as shown in FIG. 1, if the recording medium is normally conveyed on the conveyance belt 9 at a constant speed without being lifted or broken, the spurs 14 provided on the upstream side of the respective recording heads 8 will record. Since the recording medium P is disposed at a constant pressure with respect to the medium surface, the rotation speed of the recording medium P is maintained at a constant rotation speed. That is, since the signal from the encoder plate 16 connected to the spur 14 is a pulse at a constant interval, the apparatus continues a normal sequence, and at this time, the microswitches arranged near these spur holders 18 Naturally, the spur holder 18 remains OFF because the spur holder 18 does not swing. Then, the recording medium sequentially passes under each of the recording heads 8C, 8M, 8Y, and 8B to form an image of each color, and after forming the final color, is discharged.

Next, a description will be given of the operation in the case where there is a transport abnormality such as floating or jam of the recording medium.

First, the operation when the recording medium floats will be described with reference to FIG. FIG. 3 shows a case where the recording medium P reaches the cyan recording head 8C while the recording medium floats. However, a case where the recording medium reaches the other recording heads 8M, 8Y and 8B is also shown. The same is true.

When the recording medium reaches the first spur section while the recording medium floats, the spur 14 comes into contact with the recording medium P and continues to rotate in this state. At this time, the lifting of the recording medium P is suppressed by the urging pressure of the spur holder 18. That is, if the degree of floating can be corrected, the recording medium P pressed by the spur 14 is in a normal state, operates as normal, sequentially forms images of each color, and ends normally.

However, if the lifting of the recording medium P cannot be suppressed by the urging pressure of the spur holder 18, that is, if the stiffness of the recording medium P due to the floating exceeds the urging pressure of the spur holder 18, the spur holder Numeral 18 swings about the swing center axis 15 by the floating of the recording medium P. Due to this swing, the micro switch 21 is pressed to turn on the circuit.

When the circuit is turned on by the microswitch 21, the apparatus main body determines that the recording medium is transported abnormally, immediately stops the recording operation of the recording heads 8C, 8M, 8Y, and 8B, stops driving the transport belt 9, and If a continuous image forming operation is being performed, the next recording medium feeding operation is also stopped, and a jam is determined.

As a result, damage to the recording heads 8C, 8M, 8Y and 8B due to the floating of the recording medium P is prevented, and the recording of an image defect is not continued.

Next, the operation when the recording medium stops or a paper jam occurs will be described with reference to FIG.

The operation when the recording medium stops on the conveyor belt due to slippage or the like will be described. When the recording medium P stops on the transport belt 9, the spur that has been rotated in contact with the recording medium P
14 stops rotation. Then, the signal pulse from the encoder plate 16 stops. Therefore, when the signal pulse from the encoder plate 16 that detects the rotation of the spur 14 has an interval equal to or more than a certain interval, the apparatus determines that the conveyance of the recording medium is abnormal.

Then, the spur 14
When the rotation stop of the printer is detected, the apparatus main body determines that the recording medium conveyance is abnormal, immediately stops the recording operation of the recording heads 8C, 8M, 8Y, and 8B, stops the conveyance belt 9, and performs the continuous image forming operation. If it is medium, the next recording medium feeding operation is also stopped, and it is determined that a jam has occurred.

As described above, in this embodiment, the spur
14 prevents (prevents or corrects) the transport abnormality such as lifting or stopping of the recording medium P in advance, and monitors the fluctuation of the recording medium P at a level that cannot be completely corrected. The conveyance failure of the recording medium P due to the stoppage of the medium P on the conveyance belt 9 or the catching of the recording medium P is detected by detecting the rotation of the spur 14 by the encoder plate 16 to detect the jam and the conveyance failure (the image unevenness due to paper breakage or catching). , Image rub).

This makes it possible to constantly monitor the behavior of the recording medium itself over the entire width of the recording medium P, as compared with a conventional jam detection sensor of an optical type or a lever type. Become. For this reason,
Unlike the conventional jam detection sensor, it is possible to detect the conveyance abnormality of the recording medium in real time, instead of detecting the conveyance abnormality only by detecting the delay and the stagnation of the recording medium. 8M, 8Y, 8B
Damage and image defects can be prevented immediately.

In the present embodiment, the ON / OFF operation of each micro switch 21 is configured to be turned ON when the floating of the recording medium P is detected. It is needless to say that the on / off operation of the micro switch 21 may be reversed, that is, the micro switch 21 may be turned off by swinging.

In the present embodiment, the detection of the displacement of the spur 14 is performed by the microswitch 21. However, the present invention is not limited to this, and the same applies to a photo interrupter, a light detector, and the like. Needless to say, any signal can be obtained.

In this embodiment, the encoder plate 16 for detecting the rotation of the spur 14 is of an optical type. However, the present invention is not limited to this. For example, a magnetic encoder or a mechanical encoder may be used. What is necessary is just to have a mechanism for detecting rotation. The number of pulses generated by one rotation of the encoder is determined by the recording medium transport speed of the apparatus, the transport path length, and the like.

Although the plurality of spurs 14 are arranged in the width direction of the recording medium so as to cover substantially the entire width of the recording medium, the number and arrangement of spurs provided in the width direction of the recording medium are not limited. What is necessary is just to set suitably according to the kind of recording medium performed.

[Second Embodiment] In the first embodiment described above, an example is shown in which spurs and detection means are provided upstream of all four recording heads 8C, 8M, 8Y, 8B. As shown in FIG. 8, four recording heads 8C, 8M, 8Y,
8B, a spur 14 and a detecting means for detecting its rotation and displacement may be provided only on the upstream side of the cyan recording head 8C which is the most upstream in the recording medium transport direction. This embodiment has the same configuration as the above-described embodiment except that the spur 14, the spur holder 18 for detecting rotation and displacement of the spur 14, the micro switch 21, and the like are provided as a single unit. Have the same reference numerals. FIG. 6 is a diagram illustrating a state in which the recording medium P is normally conveyed. FIG. 7 is a diagram illustrating a state in which the recording medium P floats.
FIG. 4 is a state explanatory diagram when a jam occurs.

In this embodiment, before the recording medium P reaches the recording means, it is possible to detect the floating or jam of the recording medium P to stop the conveyance of the recording medium P or to stop the recording. Thus, effects similar to those of the above-described embodiment can be obtained.

The detecting means such as the one spur 14 and the microswitch 21 are not only provided on the upstream side of the recording means 8 but also on the upstream side.
By arranging it at the most downstream side of the recording means 8, that is, between the black recording head 8B and the discharge roller 10, a conveyance abnormality at the time of discharge may be detected. If the spurs 14 and the detecting means are arranged in the transport path of the recording medium P, the spurs 14 and the number of the detecting means may be one at any position.
It is not necessary to limit the number to four or four as in the above-described embodiment.

Third Embodiment In the above-described embodiment, an example is shown in which a full-line type recording head is used as recording means. However, as shown in FIGS. 9 to 11, a serial type recording head is used. Spurs even if you use it to record
14, a detecting means including a micro switch 21 or the like for detecting the rotation and displacement of the spur 14 may be provided so as to detect the conveyance abnormality of the recording medium P.

This embodiment is the same as the above-described second embodiment except that the recording means is a serial type, and the same members as those in the above-described embodiment are denoted by the same reference numerals. 9 is an explanatory diagram of a state in which the recording medium P is normally conveyed, FIG. 10 is an explanatory diagram of a state in which the recording medium P is lifted, and FIG. 11 is an explanatory diagram of a state in which a jam occurs. It is.

The recording means in this embodiment is such that the ink jet recording head 22 is mounted on a carriage 23, and the carriage 23 can reciprocate along a guide shaft 24 provided in the width direction of the recording medium. The carriage is reciprocated with respect to the recording medium P transported by the rollers 25 and supported by the platen 26, and ink is discharged from the recording head 22 to perform serial recording.

In this embodiment, the rotation and displacement of the spur 14 are detected and the recording medium
Is detected, and the conveyance of the recording medium is stopped and the recording operation is stopped, and the same effects as described in the first embodiment can be obtained.

[Other Embodiments] In the above-described embodiment, the ink jet recording system is used as the recording means. However, an electric current is supplied to the electrothermal converter according to a recording signal, and the thermal energy applied by the electrothermal converter is used. It is more preferable that the ink is ejected from an ejection port to perform recording by the growth and shrinkage of bubbles generated in the ink by utilizing film boiling in the ink.

Regarding the typical constitution and principle, it is preferable to use the basic principle disclosed in, for example, US Pat. Nos. 4,723,129 and 4,740,796. This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to a sheet or a liquid path holding a liquid (ink). By applying at least one drive signal corresponding to the recorded information and providing a rapid temperature rise above nucleate boiling,
This is effective because heat energy is generated in the electrothermal transducer, thereby causing film boiling on the heat-acting surface of the recording head. As a result, bubbles in the liquid corresponding to this drive signal one-to-one can be formed. The liquid is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are immediately and appropriately performed, so that particularly excellent liquid ejection can be achieved, which is more preferable.

As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable.

Further, if the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (linear liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned respective specifications, The present invention also includes a configuration using U.S. Pat. Nos. 4,558,333 and 4,459,600 which disclose a configuration in which a heat acting portion is arranged in a bending region.

Japanese Unexamined Patent Publication (Kokai) No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal transducer for a plurality of electrothermal transducers, or an aperture for absorbing pressure waves of thermal energy. Unexamined Japanese Patent Application Publication No.
The effect of the present invention is effective even in a configuration based on JP-A-59-138461. That is, according to the present invention, the recording can be performed reliably and efficiently regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium on which recording can be performed.

Such a recording head may have a configuration satisfying its length by a combination of a plurality of recording heads, or a configuration as a single recording head formed integrally.

In addition, even in the case of the serial type described above, the recording head fixed to the carriage or mounted on the carriage enables electrical connection with the apparatus main body and supply of ink from the apparatus main body. A replaceable chip type recording head or a cartridge type recording head in which an ink tank is provided integrally with the recording head itself may be used.

It is preferable to add recording head recovery means, preliminary auxiliary means, and the like, which are provided as components of the recording means of the present invention, since the effects of the present invention can be further stabilized. To be more specific, capping means for the recording head, cleaning means, pressurizing or suctioning means, preheating means using an electrothermal conversion type or another heating element or a combination thereof, and printing Performing a preliminary ejection mode for performing another ejection is also effective for performing stable printing.

Regarding the type and number of recording heads mounted on the carriage, for example, in addition to the recording head having only one corresponding to a single color ink, it corresponds to a plurality of inks having different recording colors and densities. May be provided in plurality. That is, for example, the recording mode of the recording means is not limited to the recording mode of only the mainstream color such as black, but may be any of a plurality of combinations integrally forming the recording head. To at least one of the full-color devices.

In addition, in the above embodiment, the ink is described as a liquid. However, an ink which solidifies at room temperature or lower and which softens or liquefies at room temperature, or an ink jet recording system The ink itself
Generally, the temperature is controlled within the range of 30 ° C or more and 70 ° C or less to control the temperature so that the viscosity of the ink is in the stable ejection range. Good. In addition, actively prevent the temperature rise due to thermal energy by using the energy of the state change from the solid state of the ink to the liquid state,
Alternatively, an ink that solidifies in a standing state for the purpose of preventing evaporation of the ink is used, and in any case, the ink is liquefied by application of heat energy according to a recording signal, and a liquid ink is discharged, or a recording sheet is used. It is also applicable to a case where an ink having a property of being liquefied for the first time by thermal energy, such as an ink which starts to solidify at the time when the temperature reaches.

The ink in such a case is disclosed in JP-A-54-5
No. 6847 or Japanese Patent Application Laid-Open No. Sho 60-71260, in which the porous sheet is opposed to the electrothermal converter in a state of being held as a liquid or solid substance in the concave portion or through hole of the porous sheet. It is good. The most effective one for each of the above-mentioned inks is to execute the above-described film boiling method.

Further, as the form of the above-mentioned ink jet recording means, in addition to the copying apparatus combined with the scanner unit as described above, in addition to those used as image output terminal devices of information processing equipment such as computers, readers and the like can be used. It may be a copier in combination, or a facsimile machine having a transmission / reception function.

Although an example in which an ink jet recording method is used as the above-described recording means has been described, the present invention does not require that the recording method be limited to the ink jet recording method. Can be applied to an impact recording method such as a wire dot recording method or other recording methods.

[0063]

The present invention is constructed as described above.
By detecting the state of the rotating member that rotates and shifts in contact with the recording medium, the conveyance abnormality of the recording medium is detected, and the recording is stopped or the like, thereby quickly preventing image defects and damage to the recording unit. Becomes possible.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a main part of a recording unit.

FIG. 2 is a diagram illustrating the arrangement of spurs as viewed from the width direction of a recording medium.

FIG. 3 is an explanatory diagram of a case where a floating recording medium is conveyed.

FIG. 4 is a diagram illustrating a state in which a recording medium has jammed.

FIG. 5 is an explanatory diagram of the entire image forming apparatus.

FIG. 6 is a diagram illustrating a state in which a recording medium is normally conveyed in the apparatus according to the second embodiment.

FIG. 7 is an explanatory diagram of a state in which a floating occurs on a recording medium.

FIG. 8 is a state explanatory diagram when a jam occurs.

FIG. 9 is an explanatory diagram illustrating a state in which a recording medium is normally conveyed in the apparatus according to the third embodiment.

FIG. 10 is an explanatory diagram of a state in which a floating occurs on a recording medium.

FIG. 11 is a state explanatory diagram when a jam occurs.

[Explanation of symbols]

 A: Scanner section B: Printer section G: Document P: Recording medium 1: Document mounting glass 2: Reading means 3: Cassette 4: Feed roller 5: Separation roller pair 6: Convey path 7: Convey roller pair 8: Recording Means 8C, 8M, 8Y, 8B: Recording head 9: Conveying belt 9a: Roller 10: Discharge roller 11: Discharge tray 12: Recovery cap 13: Suction roller 14: Spur 14a: Teeth 15: Shaft 16: Encoder plate 17: Optical sensor 18… Spur holder 19… Shaft 20… Tension spring 21… Micro switch 22… Recording head 23… Carriage 24… Guide shaft 25… Transport roller 26… Platen

Continued on front page F-term (reference) 2C056 EB12 EB29 EC12 FA03 FA13 HA29 HA32 HA34 2C058 AB16 AC07 AC17 AE02 AE09 AF04 AF17 AF20 AF27 GB05 GB06 GB22 GB30 GB43 GB47 GB54 3F048 AA05 AB01 BA14 BB05 CA08 CB09 CB17 DB03 DB03 DB03 DB03 DC06 DC13

Claims (7)

[Claims] 1. An image forming apparatus for conveying a recording medium to form an image, comprising: a recording means for recording on the recording medium; a rotating means for contacting the recording medium to be conveyed; A rotatable member; and detecting means for detecting at least one of rotation and displacement of the rotatable member, wherein transport and recording of the recording medium are controlled in accordance with a detection result of the detecting means. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein a plurality of the rotating members are arranged in a direction intersecting with a conveying direction of the recording medium. 3. The image forming apparatus according to claim 1, wherein said detecting means detects rotation of said rotating member by an optical or magnetic encoder. 4. The image forming apparatus according to claim 1, wherein the rotating member is a member having a small area in contact with a recording medium. 5. The image forming apparatus according to claim 1, wherein the recording unit performs recording by discharging ink according to a signal. 6. The image forming apparatus according to claim 5, wherein the recording unit discharges the ink by using film boiling generated in the ink by thermal energy applied by an electrothermal converter. 7. The image forming apparatus according to claim 5, wherein the recording unit has an ink ejection port in an entire area in a width direction of the recording medium.