JP2009175251A - Image forming apparatus and control method for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption by shortening time (fixing time for a first sheet of paper) required to complete a fixing operation for the first sheet of recording paper after reception of an image forming instruction from a standby state, and by minimizing time required to supply power to a heater. <P>SOLUTION: The image forming apparatus draws a first sheet of recording paper 70 from a paper feed section 2 to a paper path 8 at a point of time when the temperature of the nip section 25 of the fixing device 14 heated by a heater 27 reaches a paper feed temperature Tf lower than the fixing temperature Ts of toner. In the image forming apparatus, the distance d of a margin between the toner image formation area D of a first sheet of recording paper 70 and the conveyance start side end 71 of the sheet of paper 70 is measured. The distance d of the margin is compared with a threshold k1 stored in the storage section 36 in advance. If the distance d of the margin is equal to or greater than a threshold value k1, paper feed temperature Tf is shifted to the low temperature side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a paper feed unit on which recording paper is placed, an image recording unit that forms an image on the recording paper sent from the paper feed unit, and a paper discharge unit from the paper feed unit through the image recording unit The present invention relates to an image forming apparatus provided with a sheet conveyance path to the position and a control unit that controls conveyance of a recording sheet in the sheet conveyance path, and a control method therefor.

  One of the important problems in this type of image forming apparatus is the time required to complete the fixing operation for the first recording sheet after receiving the image forming command from the standby state (hereinafter referred to as the first sheet). For example, the fixing time can be shortened. The fixing time for the first sheet greatly depends on the time required for warming up each device constituting the image forming apparatus. In particular, it takes time to heat the nip portion of the fixing device. That is, prior to the image forming process, it is necessary to raise the temperature of the nip portion above a predetermined fixing temperature, and it takes time to raise the temperature of the nip portion.

Therefore, in the conventional image forming apparatus, in view of the conveyance time from the paper feeding unit to the nip part and the heater capability capable of increasing the temperature during the conveyance time, the outer surface temperature of the heat roller related to the nip part is When a predetermined sheet feeding temperature lower than the fixing temperature is reached, the sheet feeding operation from the sheet feeding unit is started (for example, see Patent Document 1).
Specifically, as shown in FIG. 6, when an image formation command is received from the standby state, a heater built in the heat roller of the fixing device is heated to raise the temperature of the nip portion. When the nip portion reaches a predetermined paper feed temperature Tf, the recording paper is fed out from the paper feed cassette and sent to the transport path. The paper feed temperature Tf is set to a temperature lower than the fixing temperature Ts. More specifically, the paper feed temperature Tf is determined by the fixing temperature Ts, the temperature increase rate of the nip portion per unit time, and the transport time t from when the recording paper 70 is fed out from the paper feed cassette to the nip portion. The That is, the paper feed temperature Tf is set so as to satisfy the relational expression (paper feed temperature Tf ≧ fixing temperature Ts−temperature increase speed × conveying time t).

JP 7-64436 A

  As in Patent Document 1, if the paper feeding operation is started when the paper feeding temperature lower than the fixing temperature is reached, the paper feeding operation is started after the temperature of the nip portion reaches the fixing temperature. Compared to the control mode, the first sheet fixing time can be shortened. Further, since the heat generation time of the heater can be shortened, there is an advantage that the power consumption of the fixing device can be reduced.

However, in the control mode of Patent Document 1, the paper feed timing is uniformly determined based on the time required for the start end of the recording paper in the transport direction (hereinafter simply referred to as the transport start end) to reach the nip portion. For this reason, when the margin on the recording paper is large, there is a tendency that the heater is heated unnecessarily for a long time.
That is, there is no toner image to be fixed at the conveyance start end of the first recording sheet, and the toner image may start from the center in the conveyance direction of the recording sheet or the conveyance end. As a specific example, there may be mentioned a case where the first recording sheet is a so-called cover and only the title is described at the center in the transport direction. In this case, the heat generated by the heater for maintaining the fixing temperature from when the conveyance start end of the recording paper reaches the nip until the toner image formation region passes through the nip is wasted. There is a disadvantage that the fixing time of the first sheet becomes long, and the waiting time of the user from when the image forming command is issued until the first recording sheet is output becomes long.

  The present invention aims to shorten the time (first sheet fixing time) required for completing the fixing operation on the first recording sheet after receiving the image forming command from the standby state, and to minimize the heater energization time. The purpose is to reduce the power consumption.

  The present invention provides a paper feed unit on which a recording paper is placed, an image recording unit that forms an image on a recording paper sent from the paper feed unit, and the paper feed unit through the image recording unit. An image forming apparatus including a sheet conveyance path to a paper discharge section and a control section that controls conveyance of a recording sheet in the sheet conveyance path is an object. The image recording unit applies an image forming unit for forming a toner image on a recording sheet, and heat-pressing the recording sheet on which the toner image is formed by the image forming unit, thereby fixing the toner image on the recording sheet. A fixing device, and the fixing device includes a heater for heating a nip portion that heats and pressurizes the recording paper. The control unit feeds the first recording sheet from the sheet feeding unit to the sheet conveyance path when the temperature of the nip portion reaches a sheet feeding temperature lower than the toner fixing temperature due to heat generated by the heater. It is configured. Then, the control unit measures a margin distance between the toner image formation region for the first recording sheet and the conveyance start end of the recording sheet, and compares the margin distance with a threshold value stored in advance in the storage unit. If the margin distance is equal to or greater than a threshold value, the sheet feeding temperature is shifted to a low temperature side.

  The control unit compares a plurality of threshold values stored in the storage unit with the margin distance and, based on a comparison result between the threshold values and the margin distance, sets the sheet feeding temperature in the low temperature side in multiple stages. Can be shifted to.

  The present invention also provides a paper feeding unit on which recording paper is placed, an image recording unit that forms an image on the recording paper sent from the paper feeding unit, and the image recording unit from the paper feeding unit. An object of the present invention is a control method for an image forming apparatus including a paper transport path that reaches the paper discharge section and a control section that controls transport of recording paper in the paper transport path. The image recording unit applies an image forming unit for forming a toner image on a recording sheet, and heat-pressing the recording sheet on which the toner image is formed by the image forming unit, thereby fixing the toner image on the recording sheet. A fixing device, and the fixing device includes a heater for heating a nip portion that heats and pressurizes the recording paper. The control unit feeds the first recording sheet from the sheet feeding unit to the sheet conveyance path when the temperature of the nip portion reaches a sheet feeding temperature lower than the toner fixing temperature due to heat generated by the heater. It is configured. The margin detection step for measuring the margin distance between the toner image formation region for the first recording sheet and the conveyance start end of the recording sheet, and the margin distance obtained in the margin detection step are stored in advance in the storage device. The method includes a comparison step for comparing with a stored threshold value, and a paper feed temperature correction step for shifting the paper feed temperature to a low temperature side when a margin distance is equal to or greater than the threshold value.

  In the storage unit, a plurality of threshold values are stored in advance, and in the comparison step, the paper feeding temperature is shifted to the low temperature side in multiple stages based on the comparison result between the threshold values and the margin distance. It can be.

  In the present invention, the margin distance between the toner image formation area on the first recording sheet and the conveyance start edge of the recording sheet is measured, and the distance between the toner image formation area and the conveyance start edge is equal to or greater than the threshold value The paper feeding temperature was shifted to the low temperature side. In other words, conventionally, when the conveyance start end of the recording paper reaches the nip portion, the paper feed temperature is fixed uniformly so that the outer surface temperature of the nip portion reaches the fixing temperature.In the present invention, When the toner image formation area reaches the nip portion, the paper feed temperature is shifted to the low temperature side so that the outer surface temperature of the nip portion reaches the fixing temperature.

  If the paper feed temperature is shifted to the low temperature side in this way, the paper feed operation is performed when the outer surface temperature of the nip portion is lower than the conventional temperature. It is possible to shorten the time (first sheet fixing time) required from completion of the image forming command to the completion of the fixing operation on the first recording sheet. The timing at which the toner image formation area reaches the nip portion and the timing at which the nip portion reaches the fixing temperature can be made to substantially coincide with each other to minimize the time lag between the two timings. Power consumption can be reduced.

  The control unit compares a plurality of threshold values stored in the storage unit with the margin distance and, based on a comparison result between the threshold values and the margin distance, sets the sheet feeding temperature in the low temperature side in multiple stages. Can be shifted to. More specifically, when the margin distance is small, the shift width of the paper feed temperature is small, and conversely, when the margin distance is large, the shift width of the paper feed temperature to the low temperature side is increased. The control form can be taken. As described above, when the shift range of the paper feed temperature can be changed in multiple stages according to the margin distance, the timing at which the nip portion reaches the fixing temperature at the timing at which the toner image formation region reaches the nip portion is further increased. The time lag between both timings can be further minimized. Thus, the sheet feeding operation can be started at the optimum sheet feeding timing according to the margin distance, so that the fixing time of the first sheet can be further shortened and the power consumption of the fixing device can be further reduced. Can do.

  According to the control method of the image forming apparatus according to the present invention, it is possible to obtain the same operational effects as those of the previous image forming apparatus. That is, when it is determined in the comparison step that the margin distance is equal to or greater than the threshold value, the paper feed temperature is shifted to the low temperature side in the paper feed temperature correction step, so that the outer surface temperature of the nip portion reaches a lower temperature than before. The paper feeding operation can be performed when That is, the paper feed timing can be advanced as compared with the prior art. As a result, the fixing time of the first sheet can be shortened, and the power consumption of the fixing device can be reduced.

  A plurality of threshold values are stored in advance in the storage unit, and in the comparison step, the paper feed temperature can be shifted to the low temperature side in multiple steps based on the comparison result between the threshold values and the margin distance. According to this, the timing at which the nip portion reaches the fixing temperature can be made closer to the timing at which the toner image formation region reaches the nip portion, and the time lag between the two timings can be further minimized. The sheet feeding operation can be started at the optimum sheet feeding timing. Accordingly, it is possible to further shorten the fixing time of the first sheet and further reduce the power consumption of the fixing device.

  1 to 5 show an embodiment in which an image forming apparatus and a control method thereof according to the present invention are applied to a multifunction machine having a copy function and a facsimile function. In FIG. 2, the multi-function device 1 includes a paper feed cassette (paper feed unit) 2 on which stacked recording paper (hereinafter simply referred to as paper) 70 is placed, and a paper 70 sent from the paper feed cassette 2. An image recording unit 3 that performs image formation on the image recording unit 3 and an image reading unit 4 disposed above the image recording unit 3 are included. An operation panel 5 having various operation buttons and an automatic document feeder (ADF) 6 are provided on the upper surface of the image reading unit 4. Inside the multi-function device 1, a paper transport path (hereinafter simply referred to as a transport path) 8 from the paper feed cassette 2 to the paper discharge section 7 through the image recording section 3 is formed. As shown in FIG. 3, the multifunction device 1 includes a printer controller (control unit: hereinafter simply referred to as a controller) 80 that controls the image forming operation in the image recording unit 3, and a central unit that controls the entire multifunction device 1. It is controlled by a control unit (MPU) 90.

  At the time of image formation accompanying a copy operation or the like, the paper feed roller 9 arranged at the upper end of the paper feed cassette 2 is driven to rotate, and the paper 70 is fed out to the transport path 8 one by one. As shown in FIG. 3, the paper feed roller 9 is connected to the main motor 10 that is a drive source of each part of the image recording unit 3 by connecting a paper feed clutch 11 disposed on the power transmission path. It receives the driving force of the motor 10 and rotates. The main motor 10 and the paper feed clutch 11 are controlled by a controller 80. In addition, as shown in FIG. 2, between the paper feed roller 9 and the image recording unit 3 in the conveyance path 8, the supply to the image recording unit 3 is synchronized with a toner image on a photosensitive drum 15 described later. A registration roller pair 12 for controlling paper timing is provided.

  The image recording unit 3 fixes the toner image on the paper 70 by applying an image forming unit 13 that forms a toner image on the paper 70 and heat-pressing the paper 70 on which the toner image is formed by the image forming unit 13. And a fixing device 14 to be operated. The image forming unit 13 is configured around a horizontal cylindrical photosensitive drum (hereinafter simply referred to as a drum) 15 that contacts a sheet 70 and transfers a toner image. The drum 15 during image formation rotates in the clockwise direction in FIGS. Around the drum 15, along the rotation direction, a charger 16 that charges the drum 15, a print head 17, a developing roller 18 of a toner cartridge, and a transfer roller 19 for transferring a toner image onto a sheet 70. And a cleaning unit 20 are provided. Toner is supplied from the toner cartridge to the developing roller 18 via the supply roller 21.

  The fixing device 14 includes a heat roller 23, and a press roller 24 as main components, and includes a nip portion 25 that performs heat and pressure processing on the paper 70 between the rollers 23 and 24. The heat roller 23 is formed by applying a coating treatment with polytetrafluoroethylene (PTFE) on the outer peripheral surface of a roller core formed of a metal such as aluminum having a high thermal conductivity in a hollow cylindrical shape for the purpose of improving toner releasability. The heater 27 is incorporated as a heating element. The heater 27 is configured by a halogen lamp that is formed by enclosing a filament in a long rod-like tube extending in the axial direction of the heat roller 23. The press roller 24 is pressed against the heat roller 23 by a compression spring (not shown), and is driven to rotate in accordance with the driving rotation of the heat roller 23. At the end of the conveyance path 8, a discharge roller pair 28 that performs a discharge operation of the paper 70 to the paper discharge unit 7 is disposed. The fixing device 14 is provided with a temperature sensor 29 for detecting the outer surface temperature of the heat roller 23.

  As shown in FIG. 3, a system bus 31 leading to the MPU 90 includes an interface (I / F) 32 with a PC, a scanner 33 constituting the image reading unit 4, an operation unit 34, and a data conversion circuit (CODEC) 35. A storage unit 36, a network control unit (NCU) 37, a modem 38, and the like are connected. The operation unit 34 includes a touch panel and various operation switches arranged on the operation panel 5. The storage unit 36 includes a ROM 40 that stores system programs and the like, a RAM 41 that serves as a work area for the MPU 90 and the controller 80, and an image memory 42. Information such as the toner fixing temperature Ts and the paper feed temperature Tf is stored in the ROM 40. The image memory 42 functions as a so-called buffer, and temporarily stores image data sent from the PC via the I / F 32 or image data of a document read by the scanner 33.

  In addition, in the present embodiment, a correction value for paper feed temperature correction is selected based on the margin distance d (see FIG. 1) from the conveyance start end 71 of the paper 70 to the toner image formation area D in the ROM 40. The threshold value for this is stored in advance. Specifically, two threshold values k1 and k2 as shown in FIG. The threshold value k1 is set to 1/3 of the length dimension L in the conveyance direction of the paper 70, and the threshold value k2 is set to 1/2 of the length dimension L. When the margin distance d is equal to or greater than the threshold k2, that is, when the margin distance d is equal to or greater than ½ of the length dimension L, Δt2 is selected as a correction value for correcting the paper feed temperature Tf. When the margin distance d is not less than the threshold value k1 and less than k2, that is, when the margin distance d is not less than 1/3 and less than 1/2 of the length dimension L, the correction for correcting the paper feed temperature Tf is performed. Select Δt1 as the value. The comparison operation between the margin distance d and the threshold values k1 and k2 and the selection operation of the correction values Δt1 and Δt2 will be described in detail later.

  The controller 80 includes a temperature sensor 29, a paper feed sensor (PSS) 45 that detects the position of the paper 70 on the conveyance path 8, a current detection unit 46 that detects a current value supplied to the transfer roller 19, and the like. Is connected. The controller 80 controls a transfer bias application circuit 47 for supplying a bias voltage to the transfer roller 19 based on a detection signal from the current detection unit 46 and the like. In addition, the controller 80 controls a charging bias applying circuit 48 for supplying a bias voltage to the charger 16 and a developing device bias applying circuit 49 for supplying a bias voltage to the developing roller 18 and the supply roller 21. is doing. The controller 80 also controls a memory removal voltage application circuit 50 for supplying a voltage to the cleaning device 20, a drive circuit 51 for the heater 27 of the fixing device 14, and the like.

  Next, the operation of the multifunction device 1 when it receives an image formation command from the standby state will be described with reference to the flowcharts of FIGS. This image formation command includes data relating to the number and size (B5, A3, etc.) of the sheets 70 to be printed, and data of toner images formed on each sheet 70. From the I / F 32 or the scanner 33, the system The data is transmitted to the controller 80 via the bus 31.

  When an image formation command (print trigger) is received (YES in S1), the controller 80 starts warm-up of each part of the image recording unit 3. Specifically, when a predetermined time elapses after receiving the image forming command, energization of the heater 27 is started and the nip portion 25 is heated. Further, the controller 80 measures the distance (margin distance d) between the toner image formation region D (see FIG. 1) on the first sheet 70 and the conveyance start end 71 of the sheet 70 (margin detection step: S2). ). As described above, the image formation command received by the controller 80 includes the data regarding the size of the paper 70 and the toner image. Therefore, the margin distance d can be detected based on these data.

  Next, the controller 80 compares the margin distance d with a threshold value k1 stored in advance in the ROM 40 (first comparison step: S3). If the margin distance d is equal to or greater than the threshold k1 (YES in S3), the process proceeds to the second comparison step (S4), and the margin distance d is compared with the threshold k2. If the margin distance d is greater than or equal to the threshold value k1 (YES in S3) and greater than or equal to the threshold value k2 (YES in S4), the correction value Δt2 is selected (S5) and the paper feed temperature correction step (S6) is performed. Then, the paper feed temperature Tf is corrected using the correction value (Δt2) (Tf ″ = Tf−Δt2). That is, the margin distance d from the conveyance start end 71 is the length L in the conveyance direction of the sheet. It is determined that it is ½ or more, and the paper feed temperature Tf is greatly shifted downward.

  If the margin distance d is equal to or greater than the threshold value k1 (YES in S3), but is less than the threshold value k2 (NO in S4), the correction value Δt1 is selected (S7) and the paper feed temperature correction step (S8) is performed. The paper feed temperature Tf is corrected using the correction value (Δt1) (Tf ′ = Tf−Δt1). That is, it is determined that the margin distance d from the conveyance start end 71 is not less than 1/3 and less than 1/2 of the length L in the conveyance direction of the paper 70, and the paper feed temperature Tf is shifted downward. However, Δt1 is smaller than Δt2 (see FIG. 1), and the shift width in S8 is smaller than the paper feed temperature correction process in S6.

  On the other hand, when the margin distance d is smaller than the threshold value k1 (NO in S3), the margin distance d from the conveyance start end 71 is less than 1/3 of the length dimension L in the conveyance direction of the paper 70, and the margin distance d Therefore, the paper feed temperature Tf is not corrected.

  Next, the controller 80 performs a paper feeding operation using the paper feed temperature (Tf ′, Tf ″) corrected in the paper feed temperature correction process of S6 or S8, or the paper feed temperature (Tf) not corrected. Specifically, the controller 80 determines the temperature of the heat roller 23 related to the nip portion 25 (hereinafter referred to as nip temperature) based on the outer peripheral surface temperature of the heat roller 23 detected by the temperature sensor 29. ) T. When the nip temperature T reaches the paper feed temperature (Tf, Tf ′, Tf ″) (YES in S9), the paper feed clutch 11 is turned on to feed the power of the main motor 10. Conducted by the roller 9, the paper 70 is sent from the paper feed cassette 2 to the transport path 8 (S10).

  In S <b> 11, when the paper 70 reaches the image forming unit 13, a toner image is formed on the paper 70, and then when the paper 70 reaches the nip portion 25 of the fixing device 14, the paper 70 is subjected to heat and pressure processing. The toner image is fixed on the paper 70. However, as shown in FIG. 1, when the image forming area D reaches the nip portion 25, the nip temperature T reaches the fixing temperature Ts. Therefore, the corrected sheet feeding temperatures Tf ′ and Tf ″ are set. Even when the paper 70 is fed at the used paper feeding timing, no fixing failure occurs.

  Next, the controller 80 checks whether or not the image forming process for all the sheets 70 has been completed (S12). Specifically, when there are a plurality of sheets 70, that is, when it is necessary to perform image forming processing on the second and subsequent sheets 70 (NO in S12), the process returns to S10 and the sheet feeding operation is performed. Do.

  As described above, in the image forming apparatus according to the present embodiment, when the distance d between the toner image formation region D and the conveyance start end 71 of the paper 70 is equal to or greater than the threshold value k1, the paper feed temperature Tf is set to the low temperature side. Shifted to. According to this, since the sheet feeding operation is performed when the outer surface temperature of the nip portion 25 reaches a lower temperature than before, the sheet feeding timing is advanced than before, and the fixing time for the first sheet is shortened. Can be planned. Since the timing at which the toner image formation area D reaches the nip portion 25 and the timing at which the nip portion 25 reaches the fixing temperature Ts can be substantially matched to minimize the time lag between the two timings, the energization control for the heater 25 is wasted. The power consumption of the fixing device 14 can be reduced.

  In addition to the above, the number of thresholds (the number of comparison steps) can be arbitrarily selected. That is, the threshold value may be one, or three or more.

FIG. 6 is a diagram for explaining sheet feeding timing by the image forming apparatus according to the present invention. 1 is a conceptual diagram illustrating an overall configuration of an image forming apparatus. FIG. 3 is a configuration diagram for explaining control of the image forming apparatus. It is a figure which shows the relationship between a threshold value and a correction value. 6 is a flowchart for explaining a series of image forming processes. FIG. 10 is a diagram for explaining sheet feeding timing by a conventional image forming apparatus.

Explanation of symbols

2 Paper feed unit (paper feed cassette)
3 Image recording section 8 Paper transport path 9 Paper feed roller 14 Fixing device 25 Nip section 27 Heater 70 Recording paper 71 Start of recording paper transport 80 Control section (printer controller)
D Toner image forming region Ts Fixing temperature Tf / Tf ′ / Tf ″ Feeding temperature Δt 1 / Δt 2 Correction value

Claims (4)

A paper feed unit on which the recording paper is placed, an image recording unit for forming an image on the recording paper sent from the paper feed unit, and a paper discharge unit from the paper feed unit through the image recording unit to the paper discharge unit An image forming apparatus comprising: a paper conveyance path to which the recording paper is conveyed; and a control unit that controls conveyance of the recording paper in the paper conveyance path,
The image recording unit applies an image forming unit that forms a toner image on a recording sheet, and heat-presses the recording sheet on which the toner image is formed by the image forming unit, thereby fixing the toner image on the recording sheet. A fixing device, and the fixing device includes a heater for heating a nip portion that performs a heating and pressing process on the recording paper,
The control unit feeds the first recording sheet from the sheet feeding unit to the sheet conveyance path when the temperature of the nip portion reaches a sheet feeding temperature lower than the toner fixing temperature due to heat generated by the heater. Is composed of
The control unit measures a margin distance between a toner image formation region on the first recording sheet and a conveyance start end of the recording sheet, compares the margin distance with a threshold value stored in advance in a storage unit, and An image forming apparatus that shifts the sheet feeding temperature to a low temperature side when a margin distance is equal to or greater than a threshold value. The control unit compares a plurality of threshold values stored in the storage unit with the margin distance,
The image forming apparatus according to claim 1, wherein the sheet feeding temperature is shifted to a low temperature side in multiple stages based on a comparison result between the threshold and the margin distance. A paper feed unit on which the recording paper is placed, an image recording unit for forming an image on the recording paper sent from the paper feed unit, and a paper discharge unit from the paper feed unit through the image recording unit to the paper discharge unit A control method for an image forming apparatus, comprising: a paper transport path to be reached; and a control unit that controls transport of the recording paper in the paper transport path,
The image recording unit applies an image forming unit for forming a toner image on a recording sheet, and heat-pressing the recording sheet on which the toner image is formed by the image forming unit, thereby fixing the toner image on the recording sheet. A fixing device, and the fixing device includes a heater for heating a nip portion that performs a heating and pressing process on the recording paper,
The control unit feeds the first recording sheet from the sheet feeding unit to the sheet conveyance path when the temperature of the nip portion reaches a sheet feeding temperature lower than the toner fixing temperature due to heat generated by the heater. Is composed of
A margin detection step for measuring a margin distance between a toner image formation region on the first recording sheet and a conveyance start end of the recording sheet;
A comparison step of comparing the margin distance obtained in the margin detection step with a threshold value stored in advance in a storage device;
And a paper feed temperature correction step of shifting the paper feed temperature to a low temperature side when a margin distance is equal to or greater than a threshold. In the storage unit, a plurality of threshold values are stored in advance,
4. The method of controlling an image forming apparatus according to claim 3, wherein, in the comparison step, the sheet feeding temperature is shifted to a low temperature side in multiple steps based on a comparison result between the threshold value and the margin distance.

Images