JPH0882599A - Image forming apparatus and toner concentration detection device used therein - Google Patents

Abstract

PURPOSE: To detect the amt. of the color toner bonded to an image carrier which high optical accuracy especially in a high bonding region wherein the surface of the image carrier is perfectly covered with toner. CONSTITUTION: The toner pattern image formed on an image carrier 1 is irradiated with the light of a light emitting element 2 and an image forming condition is controlled by the result obtained by detecting the reflected light thereof by a photodetector 3. A light emitting element 2 and the photodetector 3 have directional characteristics and the point P where the optical axes of the light emitting element 2 and the photodetector 3 cross each other at a right angle is present in the vicinity of the surface of the image carrier 1 and the optical axis plane S1 containing an optical axis with respect to the normal line (h) at the point P is inclined by an angle ϕ under a predetermined condition.

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 typified by a color copying machine, and is used for the same. The toner density on an image carrier is detected by a light emitting element and a light receiving element, and an image is formed accordingly. The present invention relates to a toner density detection device that controls conditions.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine or a printer, which develops an electrostatic latent image formed on a surface of a photoconductor as an image carrier using a developer containing toner, the electrostatic latent image is formed. Since the toner contained in the developer accommodated in the developing device is consumed with the development of the above, in order to keep the density of the copy image constant at all times, a new toner is added depending on the consumption amount of the developer. Toner must be replenished. Therefore, conventionally, paying attention to the fact that the toner concentration in the developer and the development concentration (toner adhesion amount to the photoconductor) have a fixed proportional relationship,
A reference chart having a certain density provided near the original glass for placing an original to be copied is exposed and developed on the photoconductor to form a reference pattern image for toner density detection, and the density is optically measured. The amount of replenishment of toner is controlled according to the detected value. Specifically, the density of the predetermined 9 set values of the reference pattern image is compared with the density of the reference pattern image detected for toner replenishment control. If the latter is higher, the toner replenishment is stopped or the replenishment amount is increased. If it is low, the toner supply is restarted or the supply amount is increased.

On the other hand, in recent years, the development of mono-color copying machines for red, blue, etc. has been promoted.
A system in which a developing device for black toner and a developing device for color toner are arbitrarily replaced, or a system in which both developing devices are provided side by side and their operations are arbitrarily switched and controlled is adopted. Conventionally, an optical means for detecting the density of a reference pattern image used in a black toner copying machine is composed of a light emitting element and a light receiving element, and the light receiving element is configured to detect specularly reflected light from the light emitting element. The optical axis plane including the optical axes of the received and emitted luminous fluxes coincides with the plane including the normal line of the image carrier. However, during development with color toner, since the color toner causes diffuse reflection, there is almost no difference in the reflectance between the photoconductor as the image carrier and the color toner, and the color toner indicated by the broken line in FIG. The solid line (black toner) cannot obtain a correlation between the toner density and the light receiving element output (amount of regular reflection light), and it is impossible to detect the density of the reference pattern image by the color toner.

As a countermeasure against this, Japanese Patent Laid-Open No. 61-20947
In JP-A-0, at least one of a light emitting element and a light receiving element is used so that the light receiving element receives specularly reflected light when black toner is used for development, and color toner is used for development. In this case, there is disclosed a toner concentration detecting device in which the light receiving element can rotate and switch in the optical axis plane so as to receive irregularly reflected light. Further, Japanese Patent Laid-Open No. 62-164066 discloses a monocolor toner having an infrared photosensor output characteristic of a quadratic curve in accordance with the amount of toner adhering on the image carrier, when the image density increases, the sensor output A method of controlling in a color characteristic region that increases even more, and limiting the replenishment of toner when the sensor output exceeds a certain value, and Japanese Patent Laid-Open No. Sho 62-209476 uses two light receiving elements, There is disclosed a method of arranging one to receive specularly reflected light and the other to receive irregularly reflected light, and controlling the toner supply amount of the developing device in accordance with the difference between the output signals of both light receiving elements.

[0005]

However, in any of the above-mentioned conventional color density detecting methods or devices, the optical axis plane including the optical axes of the light emitting element and the light receiving element is the normal line of the image carrier. Since it is configured to include, and adopts the method of changing the angle of each element in this optical axis plane,
Since there is a problem that the mechanism has to be incorporated in a narrow space and the structure is complicated, a simpler structure has been desired. Therefore, an object of the present invention is to solve the above-mentioned conventional problems and to detect the amount (area density) of color toner adhered on the image carrier with high optical accuracy. It is an object of the present invention to provide a color density detecting device having a simple structure capable of detecting with high accuracy in a high adhesion region such that the surface of the image carrier is completely covered.

[0006]

According to a first aspect of the present invention, in an image forming apparatus, a toner pattern image formed on an image carrier is irradiated with light from a light emitting element, and the reflected light is detected by a light receiving element. In the toner concentration detecting device for controlling the image forming condition based on the result, the light emitting element and the light receiving element both have directional characteristics, and the point where the optical axes of the light emitting element and the light receiving element intersect is substantially the image carrier. The angle ψ formed on the surface and formed by the normal line at this intersection and the optical axis plane including the optical axis is 1
A color density detecting device satisfying the condition of 5 ° ≦ ψ <90 ° is provided.

According to a second aspect of the invention, in the image forming apparatus, the toner pattern image formed on the image carrier is irradiated with the light of the light emitting element, and the reflected light is detected by the light receiving element to determine the image forming condition. In the toner concentration detecting device to be controlled, both the light emitting element and the light receiving element have relatively narrow directional characteristics, and their divergence angles are φ1 and φ2, respectively, and the optical axes of the light emitting element and the light receiving element. The point where
The angle ψ formed by the normal line at this intersection and the optical axis plane including the optical axis on the surface of the image carrier is ψ> (φ1 +
A color density detecting device satisfying the condition of φ2) / 2 is provided.

According to a third aspect of the invention, in the image forming apparatus, the toner pattern image formed on the image carrier is irradiated with the light of the light emitting element, and the reflected light is detected by the light receiving element to determine the image forming condition. In the toner concentration detecting device to be controlled, both the light emitting element and the light receiving element have relatively narrow directional characteristics, and their divergence angles are φ1 and φ2, respectively, and the optical axes of the light emitting element and the light receiving element. The point where
The angle ψ formed by the plane including the rotation axis of the image carrier and the optical axis plane including the optical axis in the vicinity of the surface of the image carrier is ψ.
A color density detecting device satisfying the condition of> (φ1 + φ2) / 2 is provided.

According to a fourth aspect of the invention, in the image forming apparatus, the toner pattern image formed on the image carrier is irradiated with the light of the light emitting element, and the reflected light is detected by the light receiving element to determine the image forming condition. In the toner concentration detecting device to be controlled, both the light emitting element and the light receiving element have relatively narrow directional characteristics, and their divergence angles are φ1 and φ2, respectively, and the optical axes of the light emitting element and the light receiving element. The point where
An angle ψ formed by a plane orthogonal to the rotation axis of the image carrier and an optical axis plane including the optical axis in the vicinity of the surface of the image carrier.
Is equipped with a color density detection device that satisfies the condition of ψ> (φ1 + φ2) / 2.

According to a fifth aspect of the present invention, there is provided a toner density detecting device for an image forming apparatus, wherein a colored particle pattern formed on an image carrier is irradiated with light from a light emitting element and the reflected light is detected by a light receiving element. In the toner density detecting device for controlling the image forming condition based on the result, the directivity which is the spread of the luminous flux of the light emitting element is φ1, the directivity which is the spread of the luminous flux of the light receiving element is φ2, and the luminous flux The optical axes of the received light fluxes are on the optical axis plane S1 that is substantially the same plane, and the intersection P where the optical axes of the light emitting element and the light receiving element intersect each other is on the surface of the image carrier or in the vicinity thereof. The angle formed by the optical axis plane S1 and the surface perpendicular to the surface of the image carrier at the intersection P is ψ, and the diameter of the light receiving / emitting surface of the element having the wider spread of the light receiving / emitting light flux is d The light from the element carries the image In when the optical path length of the shortest up to the reflected said light receiving element ρ, ψ ≧ min (φ1, φ2) / 2, where, min (φ1, φ2) is .phi.1, represent smaller .phi.2.

[0011] and configured so as to satisfy ^{_{ψ ≧ tan ~ 1 (d /}} 2ρ) / 2.

According to a sixth aspect of the present invention, there is provided a toner density detecting device for an image forming apparatus, wherein a toner pattern formed on a cylindrical image carrier is irradiated with light from a light emitting element, and the reflected light is received by a light receiving element. In the toner density detecting device for controlling the image forming condition according to the result detected in step 1, the directivity which is the spread of the luminous flux of the light emitting element is φ1, the directivity which is the spread of the received luminous flux of the light receiving element is φ2, and the light emission is performed. The optical axes of the light beam and the received light beam are on the optical axis plane S1 as substantially the same plane, and the intersection point P where the optical axes of the light emitting element and the light receiving element intersect each other is on or near the surface of the image carrier. , Sa is a plane including the rotation center axis of the image carrier and the point P, ψ is an angle formed by the planes S1 and Sa, and a diameter of a light emitting / receiving surface of the element having a wider spread of the light receiving / emitting light flux. d, the light from the light emitting element Let ρ be the shortest optical path length that is reflected by the image bearing member and reaches the light receiving element. Ψ ≧ min (φ1, φ2) / 2, where min (φ1, φ2) is smaller than φ1 and φ2. Represents one.

[0013] and configured so as to satisfy ^{_{ψ ≧ tan ~ 1 (d /}} 2ρ) / 2.

According to a seventh aspect of the present invention, there is provided a toner density detecting device for an image forming apparatus, wherein a toner pattern formed on a cylindrical image carrier is irradiated with light from a light emitting element and the reflected light is received by a light receiving element. In the toner density detecting device for controlling the image forming condition according to the result detected in step 1, the directivity which is the spread of the luminous flux of the light emitting element is φ1, the directivity which is the spread of the received luminous flux of the light receiving element is φ2, and the light emission is performed. The optical axes of the light beam and the received light beam are on the optical axis plane S1 as substantially the same plane, and the intersection point P where the optical axes of the light emitting element and the light receiving element intersect each other is on or near the surface of the image carrier. And a plane perpendicular to the rotation center axis of the image carrier is S
t, the angle between the planes S1 and St is ψ, the diameter of the light receiving and emitting surface of the element having the wider spread of the light receiving and emitting light flux is d, and the light from the light emitting element is reflected by the image carrier to receive the light receiving element. Let ρ be the shortest optical path length up to, ψ ≧ min (φ1, φ2) / 2, where min (φ1, φ2) represents the smaller of φ1 and φ2.

[0015] and configured so as to satisfy ^{_{ψ ≧ tan ~ 1 (d /}} 2ρ) / 2.

According to an eighth aspect of the present invention, in the toner concentration detecting device according to the fifth, sixth or seventh aspect, the light emitting element and the light receiving element are arranged so that the respective optical axes of the light emitting element and the light receiving element are included in one plane. It has a structure in which a support member is unitized and a condensing optical element is provided in front of the light emitting element. According to a ninth aspect of the present invention, in the toner concentration detecting device according to the fifth, sixth or seventh aspect,
The light emitting element and the light receiving element are unitized by a supporting member so that each optical axis of the light emitting element and the light receiving element is included in one plane,
It has a configuration in which a condensing optical element is provided in front of the light receiving element.
According to a tenth aspect of the invention, in the toner concentration detecting device according to the fifth, sixth, seventh or eighth aspect, the light emitting element and the light receiving element are supported by a supporting member so that each optical axis of the light emitting element and the light receiving element is included in one plane. The light emitting and receiving element unit is unitized and is rotatably supported with respect to the image carrier.

[0017]

According to the invention of claim 1, the light emitting element and the light receiving element are
Both have directional characteristics, and the point where the optical axes of the light emitting element and the light receiving element intersect is substantially on the surface of the image carrier, and the angle formed by the normal line at this intersection and the optical axis plane including each optical axis. Is defined as ψ, the sensitivity of the light receiving element to diffused reflection light from the color toner remarkably appears in the range of 15 ° ≦ ψ <90 °.
Therefore, the optical axis plane is rotated so that ψ is in this range,
For example, by setting it within 30 °, the amount of color toner adhering to the image carrier can be detected with high optical accuracy.

According to the second aspect of the invention, both the light emitting element and the light receiving element have relatively narrow directional characteristics, and the spread angles are φ1 and φ2, respectively, and the optical axes of the light emitting element and the light receiving element intersect. If the point is almost on the surface of the image carrier, and the angle formed by the normal to this intersection and the plane of the optical axis is ψ, the sensitivity of the light receiving element to diffused reflection light from the color toner is ψ> (φ
It appears remarkably in the range satisfying the condition of 1 + φ2) / 2. Therefore, by rotating the optical axis plane and setting ψ within this range, for example, 30 °, the amount of color toner adhering to the image carrier can be detected with high optical accuracy.

According to a third aspect of the invention, both the light emitting element and the light receiving element have directional characteristics, and their divergence angles are φ.
1, φ2, and the point where the optical axes of the light emitting element and the light receiving element intersect is in the vicinity of the substantially surface of the image carrier, and a plane including the rotation axis of the image carrier and an optical axis plane including the optical axis. When the angle formed is ψ, the sensitivity of the light receiving element to diffused reflection light from the color toner is remarkably exhibited in the range where ψ> (φ1 + φ2) / 2 is satisfied. Therefore, by rotating the optical axis plane and setting ψ within this range, for example, 30 °, the amount of color toner adhering to the image carrier can be detected with high optical accuracy.

According to a fourth aspect of the present invention, both the light emitting element and the light receiving element have directional characteristics, and the spread angles are φ1 and φ2, respectively, and the optical axes of the light emitting element and the light receiving element intersect. Is approximately in the vicinity of the surface of the image carrier, and an angle formed by a plane orthogonal to the rotation axis of the image carrier and an optical axis plane including the optical axis is ψ, diffuse reflection from the color toner of the light receiving element The sensitivity to light is remarkably exhibited in the range where ψ> (φ1 + φ2) / 2 is satisfied. Therefore, the optical axis plane is rotated to set ψ within this range (for example, 30
By doing so, the amount of color toner adhering to the image carrier can be detected optically with high accuracy.

According to a fifth aspect of the present invention, the spread angle of the luminous flux of the light emitting element is φ1, and the spread angle of the received luminous flux of the light receiving element is φ2.
The optical axes of the emitted light beam and the received light beam are on the same plane S1, and the intersection point where the optical axes intersect with each other is near the surface of the image carrier, and the surface of the image carrier at the intersection point. The angle between the plane perpendicular to the plane S1 is ψ, the diameter of the light receiving / emitting surface of the element having the wider spread of the light receiving / emitting light flux is d,
Let ρ be the shortest optical path length until the light from the light emitting element is reflected by the image carrier to reach the light receiving element. Ψ ≧ min (φ1, φ2) / 2, where min (φ1, φ2) is φ1 , Φ2 is smaller.

Further, since it is constructed so as to satisfy ψ ≧ tan _to ¹ (d / 2ρ) / 2, the color toner adhered on the image carrier does not receive the specularly reflected light from the surface of the image carrier. Is detected with high optical accuracy.

According to a sixth aspect of the invention, the spread of the luminous flux of the light emitting element is φ1, and the spread of the received luminous flux of the light receiving element is φ2.
The optical axes of the emitted light beam and the received light beam are on the same plane S1,
An intersection point P where the optical axes intersect with each other is located near the surface of the cylindrical image carrier, and the rotation center axis of the image carrier and the point P.
Sa is the plane including and the angle between the planes S1 and Sa is ψ, the diameter of the light receiving / emitting surface of the element with the wider spread of the light emitting / receiving light flux is d, and the light from the light emitting element is reflected by the image carrier. When the shortest optical path length to reach the light receiving element is ρ, ψ ≧ min (φ1, φ2) / 2, where min (φ1, φ2) represents the smaller one of φ1 and φ2.

[0024] and which is configured so as to satisfy the ^{_{ψ ≧ tan ~ 1 (d /}} 2ρ) / 2, without receiving the regular reflection light by cylindrical image bearing member surface, deposited on an image carrier The amount of the formed color toner is optically detected with high accuracy.

According to a seventh aspect of the present invention, the spread of the luminous flux of the light emitting element is φ1, the spread of the received luminous flux of the light receiving element is φ2, and the optical axes of the luminous flux and the received luminous flux are on the same plane S1, and An intersection point P where the respective optical axes intersect with each other is located near the surface of the cylindrical image carrier, the plane orthogonal to the rotation center axis of the image carrier is St, the angle formed by the planes S1 and St is ψ, and the light reception / emission is performed. When the diameter of the light receiving / emitting surface of the element with the wider spread of the light flux is d and the shortest optical path length from the light emitting element to the light receiving element after being reflected by the image carrier is ρ, ψ ≧ min ( φ1, φ2) / 2, where min (φ1, φ2) represents the smaller of φ1 and φ2.

[0026] and which is configured so as to satisfy the ^{_{ψ ≧ tan ~ 1 (d /}} 2ρ) / 2, without receiving the regular reflection light by cylindrical image bearing member surface, deposited on an image carrier The amount of the formed color toner is optically detected with high accuracy.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a color image forming apparatus to which the present invention is applied. In FIG. 1, image information converted into a digital signal in a scanner unit (not shown) is sent to a writing unit 22 that forms a visible image pattern. To be
The writing unit 22 emits laser light 22Y, 22M, 22C, 22BK including image information of each color to the recording units 23Y, 23M, 23C, 23BK, and the recording units 23Y, 23M, 23C, 23BK are on the same plane. They are arranged at regular intervals on the top. Each of the recording units 23Y, 23M, 23C, and 23BK has the same electrophotographic system configuration although the developing colors are different. For example, the recording unit 23C includes the photosensitive drum 24.
C is uniformly charged by a charger 25C at a potential corresponding to any gradation, and laser light 22C from the writing unit 22 irradiates modulated light according to image information to expose the photosensitive drum 4C. By photoconductor drum 4
The electrostatic latent image of the cyan light image formed on C is developed by the developing unit 26C and visualized.

The transfer paper sent from the paper supply unit (not shown) is
The registration roller 30 sends the toner image to the transfer belt 1 supported by the driving roller 34 and the driven roller 35 at the same timing and the toner images in order by the photoconductor drums 4BK, 4C, 4M, and 4Y while being conveyed leftward in the drawing. After being transferred, it is fixed by the fixing roller 32 and discharged. In this transfer belt 1, as shown in FIG.
The light emitting element 2 and the light receiving element 3 have a predetermined point P on the belt 1.
Are arranged so that the angles formed by the perpendicular line s and the optical axes 2a and 3a thereof are θ ₁ and θ ₂ , respectively. The light emitting element 2 and the light receiving element 3 used in this embodiment both have a relatively wide directivity, and the amount of light emitted from the light emitting element 2 or the sensitivity of the light receiving area of the light receiving element 3 is halved. The angles, that is, the divergence angles are respectively φ1 and φ2 (for example, φ1 = 30 °, φ2 = 2
0 °), the relationship of (φ1 + φ2) / 2 = 25 °.

Then, as shown in FIG. 3 viewed from the direction of arrow A in FIG. 2, the light emitting element 2 and the normal line h at the point P and the plane S1 including the optical axis 2a (3a) form an angle ψ. The light receiving element 3 is arranged, and in this embodiment, ψ = 30 °. In this configuration, when the angle ψ formed by the normal line h at the point P and the plane S1 is changed,
As can be seen from the comparison between the characteristic line 40 in the case where the transfer belt 1 is completely covered with the color toner and the characteristic line 41 in the case where there is no toner adhesion, as shown in FIG. In the range of −10 degrees to 10 degrees, the output voltage of the light receiving element 3 hardly changes, but outside the above range, the change is most noticeable as a difference between the values of the two characteristic lines. Therefore, as in this embodiment, for example, by setting the angle ψ = 30 °, the toner density on the transfer belt 1 is detected with high sensitivity. In addition, when black toner is used, since it is specularly reflected light, it can be detected with the highest sensitivity at an angle ψ = 0 °. Therefore, the value of ψ can be changed between when black toner is used and when color toner is used. A configuration can be switched between 0 ° and 30 ° as required.

An embodiment based on claim 2 will be described. As shown in FIG. 5, the light emitting element 2 and the light receiving element 3 are connected to the photosensitive drum 4C (photosensitive drums BK, 4C,
4M, 4Y) used as an example)
Perpendicular to the photoconductor drum 4C and its optical axis 2 at
They are arranged so that the angles formed by a and 3a are θ ₁ and θ ₂ , respectively. The light emitting element 2 and the light receiving element 3 used in this embodiment both have a relatively narrow spread of the light receiving and emitting light flux, that is, have a narrow directivity, and the amount of light emitted from the light emitting element 2 or the light receiving element 3 receives light. The angles at which the sensitivity of the range is halved, that is, the spread angles are φ1 and φ2 (for example, φ1 = 8 °, φ
2 = 12 °), there is a relationship of (φ1 + φ2) / 2 = 10 °.

Then, as shown in FIG. 6 viewed from the direction of arrow A in FIG. 5, a normal line (a straight line perpendicular to the tangent line) h at the point P
The light emitting element 2 and the light receiving element 3 are arranged such that the angle S and the plane S1 including the optical axis 2a (3a) form an angle ψ, and in this embodiment, ψ = 30 °. In this configuration,
When the angle ψ formed by the normal line h at the point P and the plane S1 is changed, as shown in FIG. 7, the photosensitive drum 4C
Characteristic curve 4 when color toner is completely covered
2. As can be seen from the comparison between the characteristic curve 43 with some toner adhesion and the characteristic curve 44 with no toner adhesion, since the color toner is diffusely reflected, the angle ψ is close to 0 ° or ± 30 °. In the vicinity, the change in the output voltage of the light receiving element 3 is noticeable as a difference between the values of the three characteristic curves, but in the vicinity of ± 10 °, the change is hardly seen. As shown in FIG. 8, the relationship between the output of the light receiving element 3 and the toner density when the angle ψ = 0 ° is as shown in FIG. 8, where the toner adhesion amount is 0.5 mg / cm ² or more, the characteristic line of the color toner is 50. As can be seen from the black toner characteristic line 51, the output of the light receiving element 3 hardly changes and has no sensitivity. Therefore, as in this embodiment, for example, the angle ψ = 30
By setting the angle to °, the toner density on the photoconductor drum 4C is detected with high sensitivity.

An embodiment based on claim 3 will be described. The configuration of this embodiment is substantially the same as the embodiment of claim 2. As shown in FIG. 10, the difference lies in a plane S1 including the optical axis 2a of the light emitting element 2 and the optical axis 3a of the light receiving element 3.
However, it is limited to form an angle ψ with respect to the plane Sa including the rotation axis of the photoconductor drum 4C. As shown in FIG. 9, the light emitting element 2 and the light receiving element 3 are connected to the photosensitive drum 4
A perpendicular line s at a predetermined point P on C and its optical axes 2a and 3a
Are arranged so that the angles formed by and are respectively θ ₁ and θ ₂ . Both the light emitting element 2 and the light receiving element 3 used in this embodiment have a relatively narrow directivity, and the light amount of the emitted light of the light emitting element 2 or the sensitivity of the light receiving area of the light receiving element 3 is halved. , The divergence angle is φ1 and φ2 (for example, φ
When 1 = 8 ° and φ2 = 12 °), there is a relation of (φ1 + φ2) / 2 = 10 °. Then, as shown in FIG. 10 when viewed from the direction of arrow A in FIG. 9, the light emitting element is such that the plane Sa including the rotation axis of the photosensitive drum 4C and the plane S1 including the optical axis 2a (3a) form an angle ψ. 2 and the light receiving element 3 are arranged,
In this embodiment, ψ = 30 ° is set. The description of the operation is the same as that of claim 2 and will not be repeated.

An embodiment based on claim 4 will be described. The configuration of this embodiment is substantially the same as that of the embodiment of claim 2, except that it includes an optical axis 2a of the light emitting element 2 and an optical axis 3a of the light receiving element 3 as shown in FIG. Plane S
1 is limited to form an angle ψ with respect to a plane St orthogonal to the rotation axis of the photoconductor drum 4C, and a point P ′ at which the optical axis 2a of the light emitting element 2 and the optical axis 3a of the light receiving element 3 intersect. Is
The point is not limited to the point P on the surface of the photosensitive drum 1, but is a position set inward from the surface of the photosensitive drum 1 from this point P, that is, a point set near the surface of the photosensitive drum 1.

In FIG. 11, the light emitting element 2 and the light receiving element 3
The point P ′ where the optical axes 2a and 3a of the
It is located at a position displaced from the intersection P with the normal line h on C to the inside of the photosensitive drum 1, and the normal line h passing through this point P and its optical axis 2a.
And 3a are arranged so that the angles formed by them are θ ₁ and θ ₂ , respectively. The light emitting element 2 and the light receiving element 3 used in this embodiment both have a relatively narrow directivity, and the amount of light emitted from the light emitting element 2 or the sensitivity of the light receiving area of the light receiving element 3 is halved. The angles, that is, the divergence angles are φ1 and φ2 (eg φ
When 1 = 8 ° and φ2 = 12 °), there is a relation of (φ1 + φ2) / 2 = 10 °.

FIG. 1 seen from the direction of arrow A in FIG.
As shown in FIG. 2, the light emitting element 2 and the light receiving element 3 are arranged so that the plane St including the point P and orthogonal to the rotation axis of the photosensitive drum 4C and the plane S including the optical axis 2a (3a) form an angle ψ. Are arranged, and in this embodiment, for example, ψ = 30 ° is set. The description of the operation is the same as that of claim 2, and therefore will be omitted. In this case, the point where the optical axes 2a and 3a intersect is deviated to the position P ', but since the diffusely reflected light is received, there is no problem in the sensitivity of the light receiving element 3. However, it cannot be used as a regular reflection sensor.

An embodiment based on claim 5 will be described. The light emitting element 2 and the light receiving element 3 are, as shown in FIG.
It is fixedly supported by a support member 61 of the light emitting / receiving element unit 60. A Fresnel lens 62 as a condensing optical system is arranged in front of the light emitting element 2, and a dustproof glass 63 is arranged in front of the light receiving element 3. Fresnel lens 6
In FIG. 2, the surface of the image bearing member 1 is irradiated with a light beam that is narrowed down at point P, and the light receiving element 3 receives the light spot at point P through the dustproof glass 63. Here, the directivity φ of the light emitting element 2
1 is 2 °, the directivity φ2 of the light receiving element 3 is 30 °, the diameter d of the circular light receiving surface of the light receiving element 3 is 1.2 mm, and the light from the light emitting element 2 is reflected at a point P on the image carrier 1 to be received. If the shortest optical path length ρ to reach the element 3 is 16 mm, then φ1 <φ2, so min (φ1, φ2) / 2 = φ1 / 2 = 1 ° where min (φ1, φ2) is φ1, It means the smaller φ2. , And the addition, a ^{_{tan ~ 1 (d / 2ρ)}} / 2 = tan ~ 1 (1.2 / 2 × 16) / 2 = 1 °.

FIG. 15 shows the relationship between the normal line h at the intersection point P of the image carrier 1 of FIG. 3 and the angle ψ formed by the plane S1 and the sensor output voltage (corresponding to the detected light amount). A curve 70 is a characteristic curve of the output voltage when there is no toner, B′AB is a region where the regular reflection of the image carrier 1 can be mainly detected, and C ′.
B ′ and BC are areas where only diffuse reflection of the image carrier 1 is detected. A curve 71 shows the characteristic when the toner adheres to the entire surface. The output voltage characteristic curve 71 has little dependence on the angle ψ. The same applies to the diffused reflection light component of the image carrier 1 when there is no toner.

By setting the angle ψ to 2 °, which is a value larger than 1 °, the light from the light emitting element 2 is not specularly reflected by the image carrier 1 and enters the light receiving element 3. . Therefore, the characteristics already described as shown in FIG. 13 can be obtained.

An embodiment based on claim 6 will be described.

As shown in FIG. 16, the light emitting element 2 and the light receiving element 3 are fixedly supported by a supporting member 161 of the light emitting and receiving element unit 160. A dustproof glass 163 is arranged in front of the light emitting element 2, and a Fresnel lens 162 as a condensing optical system is arranged in front of the light receiving element 3.
The Fresnel lens 162 allows only the light from the narrow region of the light flux irradiated onto the surface of the image carrier 1 by the light emitting element 2 through the dustproof glass 163 to enter the light receiving element 3. Here, the diameter d of the circular light emitting surface of the light emitting element 2 is 1.6 mm, the directivity φ1 is 30 °, and the directivity φ2 of the light receiving element 3 is 2
If the shortest optical path length ρ until the light from the light emitting element 2 is reflected at the point P on the image carrier 1 to reach the light receiving element 3 is 20 mm, then φ1> φ2, so min (φ1, φ2 ) / 2 = φ1 / 2 = 1 ° However, min (φ1, φ2) means the smaller of φ1 and φ2.

[0041] a and, also, a ^{_{tan ~ 1 (d / 2ρ)}} / 2 = tan ~ 1 (1.6 / 2 × 20) / 2 = 1.2 °.

FIG. 18 shows the relationship between the normal line h at the intersection point P of the image carrier 1 of FIG. 3 and the angle ψ formed by the plane S1 and the sensor output voltage (corresponding to the amount of detected light). A curve 170 is a characteristic curve of the output voltage when there is no toner, and is B′AB.
Is an area where the regular reflection of the image carrier 1 can be mainly detected,
C'B 'and BC are areas where only diffused reflection of the image carrier 1 can be detected. A curve 171 shows the characteristic when the toner adheres to the entire surface. Here, the angle ψ (the angle between the normal line h at the intersection point P of the image carrier 1 in FIG. 3 and the plane S1) is set to 2 °, which is a value larger than 1.2 °, so that the light emitting element 2 The light from is not specularly reflected by the image carrier 1 and does not enter the light receiving element 3. Therefore, the characteristics already described as shown in FIG. 13 can be obtained.

Further, as shown in FIG. 17, a light emitting / receiving element unit 160 as a sensor is rotatably supported with respect to the image carrier 1, and is rotated with respect to the image carrier 1.
It is also possible to detect specular reflection light and diffuse reflection light, respectively. A characteristic curve 171 in FIG. 18 shows the light receiving element output characteristic when the angle η of the sensor optical axis plane (the plane including the optical axes of the light emitting element and the light receiving element) with respect to the normal line h of the image carrier 1 is rotated. With respect to the characteristic curve 71 in FIG. 15, the sensor output decreases at a large angle. This is the image carrier 1
And the distance between the sensor and the sensor becomes large. That is,
When the sensor angle η changes, the distance between the image carrier and the light emitting / receiving element also changes, so that the output voltage when toner adheres to the entire surface decreases at a position where the absolute value of the angle η is large. From FIG. 18, it is preferable to detect specularly reflected light when η = 0 ° and irregularly reflected light when η> 2 °.

An embodiment based on claim 7 will be described.

The light emitting element 2 and the light receiving element 3 are fixedly supported by a support member 61 of the light emitting and receiving element unit 60, as shown in FIG. A Fresnel lens 62 is arranged in front of the light emitting element 2, and a dustproof glass 63 is arranged in front of the light receiving element 3. The Fresnel lens 62 irradiates point P with a light beam that is narrowed down on the surface of the cylindrical image carrier 4c (FIG. 11), and the light receiving element 3 receives the light spot at point P.

Here, the directivity φ1 of the light emitting element 2 is 2 °,
The directivity φ2 of the light receiving element 3 is 30 °, the diameter d of the circular light receiving surface of the light receiving element 3 is 1.2 mm, and the light from the light emitting element 2 is reflected by the surface of the image carrier 4c and reaches the light receiving element 3. If the shortest optical path length ρ is 16 mm, then φ1 <φ2, so min (φ1, φ2) / 2 = φ1 / 2 = 1 ° However, min (φ1, φ2) means the smaller of φ1 and φ2. .

[0047] a and, also, a ^{_{tan ~ 1 (d / 2ρ)}} / 2 = tan ~ 1 (1.2 / 2 × 16) / 2 = 1.1 °. FIG. 15 shows the relationship between the sensor output voltage and the angle ψ formed by the plane St and the plane S1 orthogonal to the rotation center axis at the point P of the image carrier 4c shown in FIG. Here, by setting the angle ψ to 2 °, which is a value larger than 1.1 °, the light from the light emitting element 2 is not specularly reflected by the image carrier to enter the light receiving element 3.

[0048]

As described above, according to the invention of claim 1, the light emitting element and the light receiving element both have directional characteristics,
Moreover, the point where the optical axes of the light emitting element and the light receiving element intersect is substantially on the surface of the image carrier, and the angle ψ formed by the normal line and the optical axis plane at this intersection satisfies the condition of 15 ° ≦ ψ> 90 °. Because of the simple structure, the amount of color toner adhering to the image carrier can be detected with high optical accuracy, and in particular, high adhesion such that the toner completely covers the surface of the image carrier can be detected. It is possible to detect with high accuracy even in a region. Further, as compared with the conventional method of rotating the light emitting element and the light receiving element in the optical axis plane, the optical axis plane itself is rotated, so that a relatively large space can be taken and the configuration is simple. Assembly work becomes easy. Furthermore, the function of the specular reflection sensor and that of the diffuse reflection sensor are the same by using the specular reflection sensor when ψ = 0 ° and the diffuse reflection sensor when ψ = x ° (x is in the above range) by simply rotating the optical axis plane. Can be combined.

According to the second aspect of the present invention, both the light emitting element and the light receiving element have relatively narrow directional characteristics, and the divergence angles are φ1 and φ2, respectively, and the light emitting element and the light receiving element are both. Since the point where the optical axes intersect is approximately on the surface of the image carrier, and the angle ψ formed by the normal line at this intersection and the optical axis plane including the optical axis satisfies the condition of ψ> (φ1 + φ2) / 2. The same effect as that of claim 1 is achieved.

According to the third aspect of the present invention, both the light emitting element and the light receiving element have relatively narrow directional characteristics, and the spread angles are φ1 and φ2, respectively, and the light emitting element and the light receiving element are both. The point where the optical axes intersect is approximately in the vicinity of the surface of the image carrier, and the angle ψ formed by the plane including the rotation axis of the image carrier and the plane of the optical axis including the optical axis is ψ> (φ1 + φ2) / 2. Since the condition (1) is satisfied, the same effect as that of claim 1 can be obtained.

According to the invention of claim 4, both the light emitting element and the light receiving element have relatively narrow directional characteristics, and the spread angles thereof are φ1 and φ2, respectively, and the light emitting element and the light receiving element are both. The point where the optical axes intersect is approximately in the vicinity of the surface of the image carrier, and the angle ψ formed by the plane orthogonal to the rotation axis of the image carrier and the plane of the optical axis including the optical axis is ψ> (φ1 + φ2) / Since the condition 2 is satisfied, the same effect as that of claim 1 can be obtained.

According to the fifth, sixth and seventh aspects of the invention, the directivity of the light emitting element is φ1, that of the light receiving element is φ2, the diameter of the circular light receiving and emitting surface of the light receiving and emitting element is d, and the light from the light emitting element is The shortest optical path length from the image carrier to the light receiving element is ρ,
When the inclination angle formed by the plane perpendicular to the surface of the image carrier and the optical axis plane of the light emitting / receiving element is ψ, the value of the inclination angle ψ is
min (φ1, φ2) / 2 (however, min (φ1, φ2) is φ
It means the smaller of 1 and φ2. ) And tan _~ ¹ (d / 2
ρ) / 2 is set to be larger than the larger value, so that the light from the light emitting element is not specularly reflected by the image carrier to enter the light receiving element, and the color toner density can be detected with high accuracy. You can

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a color image forming apparatus of an embodiment according to the present invention.

FIG. 2 is a configuration diagram showing a light emitting element and a light receiving element constituting a color density detecting device of an embodiment based on claim 1.

FIG. 3 is a configuration diagram showing a color density detection device when FIG. 2 is viewed from the A direction.

FIG. 4 is a characteristic diagram showing the relationship between the angle formed by the normal line of the image carrier and the plane of the optical axis and the output voltage of the light receiving element.

FIG. 5 is a configuration diagram showing a light emitting element and a light receiving element of an embodiment according to claim 2.

FIG. 6 is a configuration diagram showing a color density detection device when FIG. 5 is viewed from the direction A.

FIG. 7 is a characteristic diagram showing the relationship between the angle formed by the normal line of the image carrier and the plane of the optical axis and the output voltage of the light receiving element.

FIG. 8 is a characteristic diagram showing the relationship between the toner adhesion amount on the image carrier and the output voltage from the light receiving element.

FIG. 9 is a configuration diagram showing a light emitting element and a light receiving element of an embodiment according to claim 3;

10 is a configuration diagram showing a light emitting element and a light receiving element when FIG. 9 is viewed from the direction A. FIG.

FIG. 11 is a configuration diagram showing a light emitting element and a light receiving element of an embodiment according to claim 4.

12 is a configuration diagram showing a light emitting element and a light receiving element when FIG. 11 is viewed from the direction A. FIG.

FIG. 13 is a characteristic diagram showing a relationship between an output voltage of a conventional light receiving element and a toner adhesion amount on an image carrier.

FIG. 14 is a side view showing an example of a light emitting / receiving element unit in which a light emitting element and a light receiving element are integrated by a supporting member.

FIG. 15 is a characteristic curve showing the relationship between the inclination angle ψ of the density detection sensor with respect to the surface of the image carrier and the sensor output voltage.

FIG. 16 is a side view showing another example of a light emitting / receiving element unit in which a light emitting element and a light receiving element are integrated by a supporting member.

FIG. 17 is a side view showing an example of a light emitting / receiving element unit rotated with respect to the surface of an image carrier.

FIG. 18 is a characteristic curve showing the relationship between the inclination angle ψ of the density detection sensor with respect to the surface of the image carrier and the sensor output voltage.

[Explanation of symbols]

 1, 4c Image carrier 2 Light emitting element 3 Light receiving element 4C, 4M, 4Y, 4BK Image carrier 60, 160 Light emitting and receiving element unit 61, 16 1 Support member 62, 162 Fresnel lens 63, 163 Dustproof glass ψ Concentration detection sensor inclination Angle S1 Optical axis plane d Diameter of light emitting / receiving surface of light emitting / receiving element ρ Shortest distance from image carrier to light receiving element

Claims (10)

[Claims] 1. An image provided with a toner density detecting device for irradiating light of a light emitting element on a toner pattern image formed on an image carrier and detecting the reflected light by a light receiving element to control an image forming condition. In the forming apparatus, the light emitting element and the light receiving element both have directional characteristics,
Moreover, the point where the optical axes of the light emitting element and the light receiving element intersect is substantially on the surface of the image carrier, and the angle ψ formed by the normal line at this intersection and the optical axis plane including the optical axis is 15 ° ≦ ψ <90. An image forming apparatus equipped with a toner density detecting device satisfying the condition of °. 2. An image provided with a toner density detecting device for controlling an image forming condition by irradiating light of a light emitting element on a toner pattern image formed on an image carrier and detecting the reflected light by a light receiving element. In the forming apparatus, both the light emitting element and the light receiving element have relatively narrow directional characteristics, the divergence angles are φ1 and φ2, respectively, and the point where the optical axes of the light emitting element and the light receiving element intersect with each other. An angle ψ formed between the normal line at this intersection and the optical axis plane including the optical axis substantially on the surface of the image bearing member is equipped with a toner concentration detecting device satisfying the condition of ψ> (φ1 + φ2) / 2. Image forming apparatus. 3. An image provided with a toner density detecting device for irradiating a toner pattern image formed on an image carrier with light from a light emitting element and controlling an image forming condition according to a result of detecting the reflected light by a light receiving element. In the forming apparatus, both the light emitting element and the light receiving element have relatively narrow directional characteristics, the divergence angles are φ1 and φ2, respectively, and the point where the optical axes of the light emitting element and the light receiving element intersect with each other. An angle ψ formed by a plane including the rotation axis of the image carrier and the optical axis plane including the optical axis, which is approximately in the vicinity of the surface of the image carrier, has a toner density satisfying the condition of ψ> (φ1 + φ2) / 2. An image forming apparatus equipped with a detection device. 4. A toner density detecting device for irradiating a toner pattern image formed on an image carrier with light from a light emitting element, and controlling the image forming condition according to the result of detection of the reflected light by a light receiving element. The element and the light receiving element both have relatively narrow directional characteristics, the divergence angles are φ1 and φ2, respectively, and the point where the optical axes of the light emitting element and the light receiving element intersect is approximately the image carrier. The toner density is characterized in that an angle ψ formed by a plane orthogonal to the rotation axis of the image carrier and an optical axis plane including the optical axis in the vicinity of the surface satisfies a condition of ψ> (φ1 + φ2) / 2. Detection device. 5. A device for irradiating the colored particle pattern formed on an image carrier with light from a light emitting element and controlling the image forming condition according to the result of detection of the reflected light by the light receiving element. The directivity that is the spread of the light flux is φ1, the directivity that is the spread of the received light flux of the light receiving element is φ2, and the optical axes of the emitted light flux and the received light flux are on the optical axis plane S1 that is substantially the same plane. An intersection point P where the optical axes of the light emitting element and the light receiving element intersect with each other is on or near the surface of the image carrier, and a plane perpendicular to the plane of the image carrier at the intersection point P and the optical axis plane S1. Is defined as ψ, the diameter of the light receiving / emitting surface of the element having the wider spread of the light receiving / emitting light flux is d, and the light from the light emitting element is reflected by the image carrier to reach the light receiving element. When the shortest optical path length is ρ, ψ ≧ min (φ1 , Φ2) / 2, where min (φ1, φ2) represents the smaller of φ1 and φ2. And toner concentration detecting apparatus characterized by satisfying ^{_{ψ ≧ tan ~ 1 (d /}} 2ρ) / 2. 6. An apparatus for irradiating light of a light emitting element on a toner pattern formed on a cylindrical image carrier and controlling the image forming condition according to the result of detecting the reflected light by the light receiving element. The directivity that is the spread of the luminous flux of
1. Set the directivity, which is the spread of the received light flux of the light receiving element, to φ
2, the optical axes of the emitted light beam and the received light beam are on the optical axis plane S1 that is substantially the same plane, and the intersection P where the optical axes of the light emitting element and the light receiving element intersect with each other is the image carrier. A plane located on or near the surface and including the rotation center axis of the image carrier and the point P is Sa, and planes S1 and Sa are planes.
Is defined by ψ, the diameter of the light receiving and emitting surface of the element having the wider spread of the light receiving and emitting light flux is d, and the shortest time until the light from the light emitting element is reflected by the image carrier to reach the light receiving element When the optical path length is ρ, ψ ≧ min (φ1, φ2) / 2, where min (φ1, φ2) represents the smaller one of φ1 and φ2. And toner concentration detecting apparatus characterized by satisfying ^{_{ψ ≧ tan ~ 1 (d /}} 2ρ) / 2. 7. An apparatus for irradiating light from a light emitting element onto a toner pattern formed on a cylindrical image carrier, and controlling the image forming condition according to the result of detection of the reflected light by the light receiving element. The directivity that is the spread of the luminous flux of
1. Set the directivity, which is the spread of the received light flux of the light receiving element, to φ
2, the optical axes of the emitted light beam and the received light beam are on the optical axis plane S1 that is substantially the same plane, and the intersection P where the optical axes of the light emitting element and the light receiving element intersect with each other is the image carrier. A plane which is on or near the surface and is orthogonal to the central axis of rotation of the image carrier is St, an angle formed by the planes S1 and St is ψ, and The diameter is d, and the shortest optical path length until the light from the light emitting element is reflected by the image carrier to reach the light receiving element is ρ.
Then, ψ ≧ min (φ1, φ2) / 2, where min (φ1, φ2) represents the smaller of φ1 and φ2. And toner concentration detecting apparatus characterized by satisfying ^{_{ψ ≧ tan ~ 1 (d /}} 2ρ) / 2. 8. The light emitting element and the light receiving element are unitized by a supporting member so that the respective optical axes of the light emitting element and the light receiving element are included in one plane, and a condensing optical element is provided in front of the light emitting element. The toner concentration detecting device according to claim 5, 6, or 7. 9. The light emitting element and the light receiving element are unitized by a supporting member so that each optical axis of the light emitting element and the light receiving element is included in one plane, and a condensing optical element is provided in front of the light receiving element. The toner concentration detecting device according to claim 5, 6, or 7. 10. The light emitting element and the light receiving element are unitized by a supporting member so that the respective optical axes of the light emitting element and the light receiving element are included in one plane, and the light receiving and emitting element unit is attached to the image carrier. 9. The toner concentration detecting device according to claim 5, 6, 7 or 8, which is rotatably supported.