JP4422039B2 - Toner adhesion measuring device - Google Patents

Description

  The present invention relates to a toner adhesion amount measuring apparatus used in an electrophotographic copying machine, an electrophotographic printer, and the like.

As shown in the perspective view of FIG. 13, the conventional specular reflection type toner adhesion amount measuring apparatus irradiates light from the light projecting element 51 onto the photosensitive drum 52 to which the toner is adhered, and receives the reflected light by the light receiving element 54. Thus, the toner adhesion amount is measured.
To the surface of the photosensitive drum 52, color printing toner 53 such as cyan, yellow, magenta, and black necessary for transferring characters, images, and the like to copy paper is attached by charging.

  FIG. 14 is a plan view of the regular reflection type toner adhesion amount measuring apparatus. In FIG. 14, when light is irradiated from the light projecting element 51 to the photosensitive drum 52 to which toner is attached, the light is reflected by the photosensitive drum 52. The reflected light includes a reflected light component Ir 1 from the toner 53 and a reflected light component Ir 2 from the photosensitive drum 52, and is received by the light receiving element 54.

When the toner adhesion amount increases, most of the irradiation light from the light projecting element 51 is diffused and reflected by the toner, so that the amount of light received by the light receiving element 54 tends to decrease. On the other hand, when the toner adhesion amount decreases, most of the irradiation light from the light projecting element 51 is specularly reflected on the surface of the photosensitive drum 52 and received by the light receiving element 54, so that the amount of received light tends to increase.
From this, by obtaining a signal output corresponding to the amount of light received by the light receiving element 54, the amount of toner adhering to the photosensitive drum 52 can be measured.

The relationship between the amount of toner adhering and the amount of light received by the light receiving element 54 is a characteristic curve as shown in FIG. 15. In a region where the amount of adhering toner is small, the specular reflected light from the photoconductor is dominant and the amount of received light is high. As a result, the amount of received light decreases as the toner adhesion increases.
Further, when the toner adhesion amount increases, the diffuse reflection light by the toner increases and the light reception amount at the light receiving element 54 increases, so that a region where the toner adhesion amount cannot be obtained uniquely occurs, and the toner adhesion amount is accurately measured. There was a problem that I could not.

On the other hand, in the polarization separation type toner adhesion amount measuring apparatus shown in FIG. 16, the amount of received toner is detected by removing the reflected light component from the toner using a signal processing circuit after detecting the amount of light received by the two light receiving elements. This solves the problem that the amount of received light increases in a region with a large amount of light.
In the polarization separation type toner adhesion amount measuring apparatus, the light from the light projecting element 51 is irradiated to the photosensitive drum 52 to which the toner is adhered as a single polarized light through the polarization filter 56. The reflected light is applied to the photosensitive drum 52 to which the toner is attached by the polarization separation prism 57, and the polarized light component (P wave) in the direction parallel to the single polarized light and the polarized light component (S in the direction orthogonal to the single polarized light). After the light is received by the light receiving elements 54 and 55, the toner adhesion amount is measured based on the difference between the light receiving signals of the light receiving element 54 and the light receiving element 55 (see, for example, Patent Document 1 and FIG. 5). .
JP-A-6-250480

Since the surface of the photosensitive drum 52 is coated with high gloss silicon, selenium, or the like, the reflected light when the surface of the photosensitive drum is irradiated with light has a property of being easily biased in a direction parallel to the object surface. .
Accordingly, the single polarized light irradiated from the light projecting element 51 through the polarizing filter 56 is reflected on the surface of the photosensitive drum without disturbing the polarization, and is in the same polarized light component (P wave) state as the single polarized light. Then, it passes through the polarization separation prism and is received by the light receiving element 54.
On the other hand, the single polarized light irradiated to the dielectric toner is disturbed in polarization, and the polarized light component (P wave) parallel to the single polarized light and the polarized light component (S) orthogonal to the single polarized light. Is reflected by the polarization separation prism and received by the light receiving elements 54 and 55, respectively.

The light receiving element 54 receives the polarized light component (both P wave) from the surface of the photosensitive drum and the toner, and the light receiving element 55 receives the polarized light component (S wave) from the toner. By taking the difference, the P-wave and S-wave polarized light components from the toner cancel each other, and a received light signal corresponding to the polarized light component (P-wave) from the surface of the photosensitive drum can be extracted.
The amount of light received by the polarized light component (P wave) from the surface of the photosensitive drum is proportional to the area of the surface of the photosensitive drum where the toner is not attached, so that the amount of toner attached is not affected by the reflected light from the toner. Can be measured.
Therefore, as shown in the characteristic curve diagram of FIG. 15, the amount of light received in the high toner adhesion region does not occur such that the amount of light received by the light receiving element 54 increases due to the influence of reflected light from the toner in the high toner adhesion region. You can get
For this reason, in a high-end machine where printing image quality is given priority, it is common to use a polarization separation type toner adhesion amount measuring device in order to detect an accurate toner adhesion amount.

  FIG. 17 shows another conventional example of a polarization separation type toner adhesion amount measuring apparatus. In FIG. 17, the reflected light is transmitted using a polarizing filter instead of the polarization separating prism, and the polarized light component (P wave) in a direction parallel to the single polarized light irradiated to the photosensitive drum 52 on which the toner is adhered is single. After being separated into one polarized light component and a polarized light component (S wave) in the orthogonal direction and received by the light receiving elements 54 and 55, respectively, the toner adhesion amount is determined based on the difference between the light receiving signals of the light receiving element 54 and the light receiving element 55. Measurement is performed (see, for example, Patent Document 1 and FIG. 2).

[Problem 1] Ability to detect toner adhesion amount From the viewpoint of color engineering, it has been confirmed that the human eye has a high ability to accurately detect color information in an area darker than a light color. Therefore, there is a high technical need for accurately detecting a region where the toner adhesion amount is larger in order to perform printing with high image quality.
However, at present, the polarization separation type toner adhesion amount measuring apparatus does not sufficiently satisfy the requirement, and further improvement in measurement performance is demanded in a region where the toner adhesion amount is large.

FIG. 18 is a plan view of the polarization separation type toner adhesion amount measuring apparatus shown in FIG.
In FIG. 18, the light projecting element 51 and the light receiving elements 54 and 55 with the lead portions formed in an L shape are incorporated and mounted on the circuit board 60 with the light shielding wall 66 in the center of the optical unit holder 61.
As the light projecting element 51, an LED having a resin mold structure as shown in FIG. 19 is used, and the commercially available LED has a minimum diameter of 3 mm.
The mold and the lead frame 63 for external connection are integrally formed with a mold resin 64, and the LED chip 65 is mounted in the cavity portion at the center of the lead frame, and then connected by wire bonding.
The light receiving elements 54 and 55 also have a structure in which a lead frame is integrally formed in a resin mold similar to that shown in FIG. 19 and a photodiode chip is mounted in the cavity, and then connected by wire bonding.
Even though the light projecting element 51 and the light receiving elements 54 and 55 have a diameter of 3 mm and a length of 10 mm, the optical unit holder 61 having a width of 20 mm can be arranged to have a narrow angle up to an incident / reflection angle of 20 °. It was.

Further, since the photosensitive drum is charged with an electric field strength of about 1 kV / m, the influence of electrostatic noise on the signal processing circuit built in the polarization separation type toner adhesion amount measuring apparatus is eliminated, and the scattering of toner causes the apparatus to scatter. In order to make it difficult for toner to adhere to the detection surface, the distance from the detection surface to the photosensitive drum needs to be 5 mm or more.
On the other hand, it is necessary to keep the distance from the detection surface to the photosensitive drum to 7 mm or less in order to avoid an increase in the size of the printing device and not to reduce the SN ratio at the time of detection.
Therefore, in order to set the distance from the sensor detection surface to the photosensitive drum in the range of 5 to 7 mm and arrange the light projecting element and the light receiving element having a diameter of φ3 and a length of 10 mm with the light shielding wall interposed therebetween, the incident / reflection angle θ≈ The limit is set to 20 °.

Therefore, the sensor irradiates the photosensitive drum to which the toner is attached at an incident angle θ = 20 °. However, since the spherical toner is irradiated from an oblique direction, the projected light is irradiated on the surface of the photosensitive drum. A blind spot that is not irradiated (hereinafter referred to as a dead angle) is born.
FIG. 20 shows the difference in dead angle when the incident angles θ = 20 ° and θ = 8 ° are set. The shadow length w due to the dead angle when the radius of the toner particles = R is Is expressed by the following [Equation 1].

Therefore, when the incident angle θ1 = 20 °, w1 = 0.42R, and when the incident angle θ2 = 8 °, w2 = 0.15R, so w2 / w1≈0.36. The length can be set to 1/2 or less.
Originally, the shaded portion due to this dead angle is a region where the toner is not attached and the irradiation light to the photoreceptor is to be projected, and the incident angle θ can be set to an acute angle more than 20 °. If possible, this region can be irradiated, and the measurement accuracy can be improved.

[Problem 2] Distance variation characteristic of toner adhesion amount detection In the above problem 1, in order to answer the technical need to accurately detect a region where the toner adhesion amount is larger, the distance variation between the sensor and the photosensitive drum is required. On the other hand, it is necessary to always obtain a stable output.
In FIG. 21, when the incident / reflecting angle θ is set to θ = 20 ° and θ = 8 °, how much misalignment occurs when reflected light from the photosensitive drum is received by the light receiving element due to distance variation. It is shown.
The light receiving position shift in the light receiving element causes a shift of 2 × ΔL × sin θ with respect to the distance variation ΔL between the sensor light receiving surface and the photosensitive drum, and when a shift of ΔL = 0.5 mm occurs, θ = 20 °, 0.34 mm, and θ = 8 °, 0.14 mm. As the incident / reflection angle becomes sharper, the influence of the light receiving position shift on the distance variation becomes smaller.
Therefore, in order to further improve the detection characteristics when the distance varies, it is preferable to make the incident / reflection angle θ sharp.

[Problem 3] Performance Variation of Toner Adhesion Amount Sensor In the polarization separation type sensor of FIG. 18, the light projecting element 51 and the light receiving elements 54 and 55 use elements of a resin mold structure.
When positional deviation occurs in these light projecting elements and light receiving elements, the characteristic curve for detecting the toner adhesion amount will vary. Is closely attached to the holder 61 so as not to cause a positional shift.
However, the variation in the light emission distribution of the light projecting element 51 is caused by the variation in the internal structure of the light projecting element, and the variation in the sensor characteristic curve due to this variation cannot be improved.

FIG. 22 is a front view of an LED chip and a lead frame having a resin mold structure, where (a) is a normal position, and (b) is a diagram showing a case where the chip mounting position and the resin mold position are shifted.
The lead frame 63 exists inside the resin mold 64, but when the LED chip 65 is mounted on the lead frame 63, a mounting position shift of about ± 50 μm occurs.
Further, when the lead frame 63 is resin-molded, the relative position between the lead frame and the mold resin mold is displaced by about ± 150 μm, and the maximum is between the LED chip 65 and the mold resin outer shape 64. A large positional deviation of 200 μm will occur.

FIG. 23 shows a structural view of the polarization separation type toner adhesion amount measuring apparatus of FIG. 18 viewed from the side.
The relative displacement between the LED chip and the mold resin shown in FIG. 22 causes variations in the irradiation direction from the light emitting element 51 to the photosensitive drum 52.
For example, when the irradiation direction of the light emitting element 51 is shifted to the left, the reflected light from the photosensitive drum 52 is received in a form shifted toward the light receiving element 54 due to the influence of the curved surface of the photosensitive drum ( Increasing the amount of P wave received).
On the contrary, when the irradiation direction of the light emitting element 51 is shifted to the right, the reflected light from the photosensitive drum 52 is received in a form shifted toward the light receiving element 55 (increase in the amount of received light of the S wave).
Therefore, as shown in the characteristic curve of FIG. 24, the normal characteristic curve varies as a characteristic curve a when the irradiation position is shifted to the left and a characteristic curve b when the irradiation position is shifted to the right. Therefore, there is a problem in that it is necessary to individually adjust the gain of the light receiving amount of the light receiving element 54 with respect to the light receiving element 55.

[Problem 4] Restriction on dimensions of toner adhesion amount sensor Conventionally, a color laser beam printer (LBP) has a volume of about 350 L. However, as the miniaturization has progressed, printers with half the volume have been developed. It's getting on. Accordingly, the volume of the ink jet printer is not changed, and the use in the field of individual users and SOHO is rapidly expanding. Naturally, the toner adhesion amount measuring device is required to be reduced in volume including the sensor thickness.
On the other hand, the conventional toner density sensor as shown in FIG. 18 uses optical parts having a diameter of about 3 mm and a length of about 10 mm for the light projecting element 51 and the light receiving elements 54 and 55, and needs to be arranged in the vertical direction with respect to the photosensitive drum surface. Therefore, miniaturization of color LBP was inhibited.
Further, in the polarization separation type toner adhesion amount measuring apparatus using the polarization separation prism as shown in FIG. 16, it is necessary to dispose the polarization separation prism between the optical paths from the surface of the photosensitive drum to the light receiving element. It becomes a factor that further inhibits.
On the other hand, in the polarization separation type toner adhesion amount measuring apparatus using the polarization filter of FIG. 17, only a portion corresponding to the thickness of the polarization filter is a factor to increase the height of the sensor, and therefore a polarization separation prism is used. Compared to measuring devices, it is easy to miniaturize.
Therefore, in order to reduce the height dimension of the polarization separation type toner adhesion amount measuring device having high toner detection performance, the polarization separating type toner adhesion amount measurement device using the polarization filter of FIG. It was necessary to reduce the size of the light receiving element.

  Due to the above problems, the distance between the light projecting element and the light receiving element is shortened, the incident angle to the toner adhering to the photosensitive drum is sharpened, the dead angle is reduced, and the toner Improves sensor detection performance in high adhesion areas, reduces sensor output fluctuation due to distance fluctuation, and maintains position accuracy of light emitting point of light emitting element and light receiving point of light receiving element, reducing performance variation There has been a demand for a miniaturized toner adhesion amount measuring apparatus that can be used.

The present invention has been made to solve the above-described problems, and includes a light projecting optical system including a light projecting element that irradiates light onto an image bearing member to which toner adheres, and an image bearing of light emitted from the light projecting optical system. A light receiving optical system including a light receiving element that receives reflected light from the body,
The light projecting optical system irradiates the image carrier with the light from the light projecting element as single polarized light that has passed through the light polarizing filter,
The light receiving optical system receives first polarized light in a direction parallel to the single polarized light irradiated from the light projecting optical system by the first light receiving polarizing filter, out of the reflected light component from the image carrier. A first light receiving element having a light receiving element and a second light receiving element for receiving polarized light orthogonal to the single polarized light emitted from the light projecting optical system by the second light receiving polarizing filter; A toner adhesion amount measuring apparatus for measuring a toner adhesion amount based on a difference between a light reception signal at the second light reception signal and a light reception signal at a second light receiving element,
The light projecting element and the first and second light receiving elements are mounted on the same circuit board and covered with an optical unit holder.
The optical unit holder is provided with a recess, and the projection polarizing filter and the first and second light receiving polarization filters are fitted into the recess,
A projecting polarizing filter and first and second light receiving polarizing filters are fixed to the outer surface of the optical unit holder, and a plastic piece having a convex optical lens is fixed to the filter and the outer surface of the optical unit holder. Positioning and fixing the polarizing filter and the convex optical lens part,
A light shielding wall is provided between the light projecting element and the first and second light receiving elements, and the light shielding wall extends from the optical unit holder side to the circuit board side,
Attaching amount of toner, characterized in that a slit for restricting the optical path of the irradiation light from the light projecting element to the image carrier is provided in the optical unit holder, and the light projection angle and the light reception angle with respect to the image carrier are set to 19 ° or less It is a measuring device.

In addition, the present invention is to solve the above-described problems, and includes a light projecting optical system including a light projecting element that irradiates light to an image carrier to which toner adheres, and a light projected from the light projecting optical system. A light receiving optical system including a light receiving element for receiving reflected light from the image carrier,
The light projecting optical system irradiates the image carrier with the light from the light projecting element as single polarized light that has passed through the light polarizing filter,
The light receiving optical system receives first polarized light in a direction parallel to the single polarized light irradiated from the light projecting optical system by the first light receiving polarizing filter, out of the reflected light component from the image carrier. A first light receiving element having a light receiving element and a second light receiving element for receiving polarized light orthogonal to the single polarized light emitted from the light projecting optical system by the second light receiving polarizing filter; A toner adhesion amount measuring apparatus for measuring a toner adhesion amount based on a difference between a light reception signal at the second light reception signal and a light reception signal at a second light receiving element,
The light projecting polarizing filter and the first light receiving polarizing filter are constituted by a single polarizing filter,
The light projecting element and the first and second light receiving elements are mounted on the same circuit board and covered with an optical unit holder.
A light shielding wall is provided between the light projecting element and the first and second light receiving elements, and the light shielding wall extends from the optical unit holder side to the circuit board side,
Attaching amount of toner, characterized in that a slit for restricting the optical path of the irradiation light from the light projecting element to the image carrier is provided in the optical unit holder, and the light projection angle and the light reception angle with respect to the image carrier are set to 19 ° or less. It is a measuring device.

Furthermore, the toner adhesion amount measuring apparatus is characterized in that the semiconductor chip used for the light projecting element and the light receiving element is directly mounted on a circuit board without a metal frame .

A toner adhesion amount measuring apparatus is characterized in that a concave portion is provided in the optical unit holder, and a light projecting polarizing filter and first and second light receiving polarizing filters are fitted in the concave portion. Then, a light projecting polarizing filter and first and second light receiving polarizing filters are fixed to the outer surface of the optical unit holder, and a plastic piece having a convex optical lens formed on the outer surface of the filter and the optical unit holder is provided. The toner adhesion amount measuring device is characterized in that the polarizing filter and the convex optical lens portion are fixedly positioned and fixed.

  Further, the toner adhesion amount measuring apparatus is characterized in that the light projecting element and the first and second light receiving elements are arranged on substantially the same straight line.

  The slit for limiting the optical path for irradiating light from the light projecting element to the image carrier is elliptical or rectangular, and the major axis direction of the slit is parallel to the first and second light receiving element arrangement directions. The toner adhesion amount measuring apparatus is characterized in that:

  In addition, a third light receiving element for detecting the light amount of the light emitting element is disposed on the circuit board, and the light emitted from the first light projecting element is reflected by the reflector provided in the optical unit holder, and the reflected light is reflected. Is a toner adhesion amount measuring apparatus having a function of maintaining the light quantity of the light projecting element at a constant value by receiving the light by the third light receiving element and feeding back to the first light projecting element.

  The light emitting element and the light receiving element are mounted directly on the circuit board, and the distance between the two elements is shortened so that the incident angle to the toner adhering to the photosensitive drum is sharpened (19 ° or less). In addition, the dead angle is reduced, and the sensor detection performance in the high toner adhesion region in the polarization separation type sensor can be improved, and the sensor output fluctuation due to the distance fluctuation can be reduced.

  In addition, by directly mounting the semiconductor chip as the light projecting element and the light receiving element on the circuit board, the position accuracy of the light emitting point of the light projecting element and the light receiving point of the light receiving element can be maintained, and polarization separation with little performance variation Type toner adhesion amount measuring device can be provided.

Furthermore, a concave portion is provided on the light projecting surface and the light receiving surface side of the optical unit holder, and the concave portion transmits a polarized light in a direction parallel to the single polarized light irradiated from the light projecting optical system; When the polarizing filter is inserted into the optical unit holder, the single polarizing light emitted from the light projecting optical system and the polarizing filter (S wave) that passes the polarized light in the vertical direction are fitted to each other. Can prevent mispositioning.
Then, by setting the depth of the concave portion to the thickness of the polarizing filter, the polarizing filter can be arranged with high positional accuracy.

  By mounting the light projecting element and the two light receiving elements on the same straight line on the circuit board and arranging them in parallel on the cylindrical surface of the photosensitive drum, the light emitting element and the two light receiving elements are not affected by the curvature radius R of the cylindrical photosensitive drum. Even when the sensor is tilted in the horizontal or vertical direction (angle change), the sensor can be hardly affected by the output fluctuation.

  Further, out of the light emitted from the light projecting element, the polarization filter that passes the single polarized light, and the same polarized light as the single polarized light emitted from the light projecting optical system among the reflected light components from the image carrier By constructing the polarizing filter through which the components pass with a single polarizing filter, it is possible to cover two polarizing filters that were required in the past, and to simplify the assembly of the polarization separation type toner adhesion measuring device. be able to.

  In addition, the light projecting path from the light projecting element to the photosensitive drum has an elliptical or rectangular slit that restricts the light to be projected, and the long side of the slit is set in the arrangement direction of the two light receiving elements. Even when the sensor is tilted (angle change) with respect to the cylindrical direction of the photosensitive drum, fluctuations in the sensor output are reduced, and a stable light receiving output can be obtained.

  A third light receiving element for detecting the light amount of the light emitting element is arranged on the circuit board, and the third light receiving element is fed back from the third light receiving element to the light projecting element using a reflector, whereby the light amount of the light projecting element is constant. Therefore, it is possible to correct the change in the amount of light due to the temperature change of the light projecting element.

  Embodiments of the present invention will be described below with reference to the drawings.

[Example 1]
FIG. 1 is a diagram showing a first embodiment of a toner adhesion amount measuring apparatus according to the present invention, in which an LED chip 1 serving as a light projecting element and photodiode chips 4 and 5 serving as light receiving elements are mounted on a circuit board 10. The optical unit holder 11 limits the sensor light projecting / receiving path.
In FIG. 1, (a) is a perspective view during assembly, (b) is a perspective view after assembly, and (c) is a partial cross-sectional view from the lateral direction of (b).
Each of the LED chip 1 and the photodiode chips 4 and 5 uses a semiconductor bare chip, and is arranged in a straight line in the longitudinal direction of the circuit board 10 in the form of chip mounting.

As shown in FIG. 2A, the chip mounting form of the LED chip 1 and the photodiode chips 4 and 5 on the circuit board 10 is obtained by die-bonding the chip on the circuit board 10 and then starting from the chip surface side. The upper wiring pattern is formed by bonding with gold wires or aluminum wires 15 or, as shown in FIG. 2B, bumps 16 are formed on the chip surface and flipped onto the circuit board 10 It takes the form of chip mounting.
When these semiconductor bare chips are directly mounted on a circuit board, the chip mounting position accuracy can be ± 20 μm.

Between the LED chip 1 mounted on the circuit board 10 and the photodiode chips 4, 5, an interval that secures a distance for constituting the light shielding wall 13 is arranged.
Then, a moisture proof resin 14 is applied to the LED chip 1 and the photodiode chips 4 and 5 by a transparent resin mold, and then the optical unit holder 11 is fitted and bonded onto the circuit board.

A slit (window) serving as an optical path for light projection and light reception is provided on the upper surface of the optical unit holder 11, and light is irradiated from the LED chip 1 to the photosensitive drum 2 through this slit, and reflected light from the photosensitive drum 2. Is received by the photodiodes 4 and 5 through the slits.
Further, the outer surface of the optical unit holder 11 is provided with concave portions corresponding to the vertical, horizontal, and thickness dimensions of the polarizing filter, and the polarizing filters 6, 8, and 9 can be fitted and disposed in the concave portion. it can.

FIG. 3A is a diagram illustrating a path in which light is irradiated from the LED chip 1 of FIG. 1C to the photosensitive drum 2 and reflected from the photosensitive drum 2 to the photodiode chips 4 and 5.
The LED chip has a relatively wide half-value angle (example: 45 °) as indicated by an irradiation light curve 18 shown in FIG. Therefore, as shown in FIG. 3A, by arranging the slit 17 to have the same angle as the incident angle θ to the photosensitive drum 2, the light passing through the optical path is limited by the slit 17, and at the incident angle θ. The photosensitive drum 2 can be irradiated with light.

The light projected at the incident angle θ is applied to the photosensitive drum 2 in a state of being made into a single polarized light by the projection polarizing filter 6.
The reflected light from the photosensitive drum 2 passes through the first and second light receiving polarization filters 8 and 9, and the polarized light (P wave) in the direction parallel to the single polarized light on the light projecting side is the first light receiving polarization filter. 8 is received by the photodiode 4, and the polarized light (S wave) in the direction orthogonal to the single polarized light on the light projecting side is received by the photodiode 5 through the second light receiving polarization filter 9. The difference between the received light signal and the received light signal of the photodiode 5 is calculated by a signal processing circuit (not shown), and the toner adhesion amount is measured.

[Example 2]
FIG. 4 is a view showing a second embodiment of the toner adhesion amount measuring apparatus according to the present invention. A plastic piece 19 (transparent) having a convex optical lens formed on the front surface of the optical unit holder 11 of the toner adhesion quantity apparatus of FIG. ). Since the sensor structure is substantially the same as that of FIG. 1 except that the plastic piece 19 is disposed, portions different from FIG. 1 will be described below.

FIG. 4A is a perspective view showing a second embodiment of the toner adhesion amount measuring apparatus. The light projecting polarization filter 6 fitted to the optical unit holder 11, the first and second light receiving polarizations. A plastic piece 19 formed with a convex optical lens is brought into contact with the outer surfaces of the filters 8 and 9, and the plastic piece 19 and the optical unit holder 11 are fixed so that the convex optical lens portion is aligned with the position of the polarizing filter portion. ing.
FIG. 4B is a partial cross-sectional view from the lateral direction of the toner adhesion amount measuring device, and FIG. 4C is a schematic cross-sectional view of a plastic piece 19 on which a convex optical lens is formed. As is clear from FIGS. 4B and 4C, the light is condensed and irradiated on the convex optical lens portion (the front surface 19b and the back surface 19a) so that the irradiation light from the light projecting element 1 is not dispersed.
The light reflected from the photosensitive drum 2 is restricted by the light receiving side lens (front surface 19c, back surface 19d) of the convex optical lens portion, and is condensed by the convex optical lens so that the light is not dispersed. Light is received by the diodes 4 and 5. Since the photodiodes 4 and 5 on the light receiving side of the sensor are arranged side by side in the longitudinal direction of the substrate, the light receiving side lens is an elliptical lens with the arrangement direction of the photodiodes 4 and 5 on the long axis side. Thus, even if the distance between the sensor and the photosensitive drum 2 varies, it is possible to reduce the influence of the light receiving position shift on the light receiving side photodiodes 4 and 5.
In addition, a polarizing filter is fitted into the concave portion of the optical unit holder, and a plastic piece having a convex optical lens formed on the outer surface thereof is fixed, so that the polarizing filter is accurately placed between the optical unit holder and the plastic piece for a long period of time. It becomes possible to fix the positioning.
In the above embodiment, the convex optical lens surfaces 19b and 19c are convex surfaces, but may be flat surfaces.

In the embodiment shown in FIGS. 1 and 4, the light emitting element and the light receiving element are reduced in size by directly mounting the semiconductor bare chip on the circuit board instead of the conventional resin mold type LED and photodiode. By arranging the distances between the light receiving elements closer to each other, the incident / reflection angle θ to the photosensitive drum, which is limited to θ = 20 ° in the conventional structure, is sharpened to 19 ° or less.
FIG. 5 is a diagram showing the relationship between the toner adhesion amount and the light reception amount at the incident / reflection angles θ = 20 ° (conventional example) and θ = 8 ° (example 2) by the toner adhesion amount measuring device of FIG. .
The sharpening to the incident / reflecting angle θ = 8 ° has resulted in an improvement in detection performance in the high adhesion amount region, and as shown in FIG. 20, the dead angle in the irradiation light to the toner is reduced. The ability to project and receive light onto the photosensitive drum can be increased.

  In addition, by not using LED and photodiode resin molds and lead frames, the thickness can be reduced to about 1/3 of the conventional one, and the sensor height in the vertical direction on the photosensitive drum can be reduced, greatly reducing the size. ing.

Furthermore, by mounting semiconductor chips such as LEDs and photodiodes directly on the circuit board, the mounting position shift of the chip to the lead frame, which was a problem with resin molded products, and the position shift of the lead frame with the resin mold die (A maximum of 200 μm) is reduced to ± 20 μm.
Since the positional accuracy of both the light projecting element and the light receiving element can be improved, variations in detection characteristics of the sensor are greatly reduced.

[Example 3]
6A and 6B show a third embodiment of the toner adhesion amount measuring apparatus according to the present invention, in which FIG. 6A is a perspective view and FIG. 6B is a front view. The LED chip 1 that is a light projecting element and the photodiode chips 4 and 5 that are light receiving elements are arranged in a straight line in the longitudinal direction of the circuit board 10, and the circuit board 10 and the cylindrical surface of the photosensitive drum are arranged in parallel. .
In FIG. 6, when a lateral shift is caused in the circuit board on which the light projecting element and the light receiving element are mounted, there is no influence from the R surface of the photosensitive drum as shown in FIG.
Furthermore, by setting the incident / reflecting angle θ to an acute angle, the influence of distance fluctuation with the photosensitive drum can be greatly reduced as shown in FIG.
Therefore, it is possible to provide a sensor having excellent distance characteristics and angular characteristics.

Further, the light projecting side slit is elliptical, and the long axis side of the slit is set to coincide with the arrangement direction of the two light receiving elements.
In this case, since the light projected to the photosensitive drum is projected as an elliptical spot light, the reflected light is reflected in a direction spreading in the arrangement direction of the light receiving elements. Therefore, when a lateral tilt (angle change) is generated, reflected light is less affected by the tilt (angle change), and a sensor output with stable angle characteristics can be obtained.
FIG. 7 is a diagram showing angular characteristics when the slit on the light projecting side is a circle having a diameter of 1 mm and an ellipse having a size of 1 mm × 2 mm. As shown in FIG. 7, when the elliptical slit is used, the output characteristics hardly change in the angle characteristics.

[Example 4]
FIG. 8 shows a fourth embodiment of the toner adhesion amount measuring apparatus according to the present invention, which improves the workability when the polarizing filter is incorporated in the optical unit holder.
FIG. 8A is a perspective view when assembling the above apparatus, and FIG. 8B is a front view after the assembly.
In FIG. 8, a polarizing filter (P wave) 6 arranged to polarize the light projected from the light projecting element, and light in a polarization direction parallel to the single polarized light irradiated to the photosensitive drum among the reflected light. A polarizing filter (P wave) 8 that transmits light and a polarizing filter (S wave) 9 that transmits polarized light orthogonal to the single polarized light applied to the photosensitive drum are disposed in the fitting portion of the optical unit holder 11. Has been.
A light emitting side LED chip and a light receiving side photodiode chip are arranged inside the optical unit holder 11 as viewed from the polarizing filter. Here, the three polarizing filters 6, 8, 9 are individually inserted into the stepped portion of the optical unit holder 11. However, since the polarization directions of the filters are different, the polarizing filters having the same vertical and horizontal dimensions are used. If used, there is a risk of misdirection during installation.
Therefore, as shown in FIG. 9, by preparing polarizing filters having different vertical and horizontal dimensions and incorporating them by changing the arrangement depending on the required polarization direction, it is possible to eliminate the mistake in inserting the polarizing filter.

[Example 5]
Further, as a fifth embodiment of the toner adhesion amount measuring apparatus according to the present invention, FIG. 10 shows an example in which workability is improved by using two polarizing filters which were used in the above embodiment.
FIG. 10 shows the polarization filter (P wave) 6 arranged to polarize the light projected from the light projecting element and the photosensitive drum among the reflected light when the polarization filter of FIG. 9 is inserted. A polarizing filter (P wave) 8 that transmits light having the same polarization direction as that of single polarized light is integrated into a single polarizing filter.
Thereby, two polarizing filters can be provided, and the efficiency of the filter assembling work can be improved.

[Example 6]
FIGS. 11A and 11B are views showing a sixth embodiment of the toner adhesion amount measuring apparatus according to the present invention, in which FIG. 11A is a perspective view before the optical unit holder is attached, and FIG. 11B is a lateral view after the attachment. It is a fragmentary sectional view.
In addition to the configuration of FIG. 4, the toner adhesion amount measuring device of FIG. 11 reflects a part of the light emitted from the light emitting element 1 by the reflector 21 and is arranged on the side surface side of the light projecting element 1. The photodiode chip 20 as an element receives light, and a feedback function is provided to control the amount of light emitted from the light emitting element 1 to be constant based on the amount of light received.

FIG. 12 is a diagram showing a feedback control function of the toner adhesion amount measuring apparatus of FIG.
In FIG. 12, a part of the light irradiated from the LED chip 1 that is a light projecting element to the photosensitive member 2 to which the toner 3 adheres is reflected by a reflector 21 disposed obliquely in front of the light projecting element 1 to project the light. Light is received by the third light receiving element 20 disposed on the side surface of the element 1.
The output of the light receiving element 20 corresponding to the irradiation light quantity of the light projecting element 1 is compared with the reference value Vref by the comparator 67. When the output is smaller than Vref, the light quantity of the light emitting element 1 is increased. Is controlled so that the output of the light receiving element 13 is always kept at Vref.
Therefore, even when the irradiation light amount of the light projecting element 1 changes due to a change in ambient temperature or a change with time, feedback control is performed to keep the output of the light receiving element 13 constant at Vref, so that the irradiation light amount of the light projecting element 1 is always changed. Can be kept constant.

1A and 1B are diagrams illustrating a toner adhesion amount measuring apparatus according to an embodiment of the present invention, in which FIG. 1A is a perspective view during assembly, FIG. 1B is a perspective view after assembly, and FIG. It is a fragmentary sectional view from the horizontal direction. It is the side view which showed the form which mounts an LED chip and a photodiode chip on the circuit board of FIG. FIG. 3A is a diagram showing an optical path in light projection and light reception of the toner adhesion amount measuring apparatus in FIG. 1, and FIG. 3B is a diagram showing an irradiation light distribution of the LED chip. FIG. 4A is a view showing a toner adhesion amount measuring apparatus according to another embodiment of the present invention, and FIG. 4A shows a plastic piece having an optical lens formed on the front surface of the optical unit holder of the toner adhesion amount measuring apparatus of FIG. FIG. 4B is a partial sectional view from the lateral direction, and FIG. 4C is a schematic sectional view of a plastic piece on which an optical lens is formed. FIG. 5 is a diagram showing the relationship between the toner adhesion amount and the light reception amount when the incident angle θ is 8 ° and 20 ° by the toner adhesion amount measuring device of FIG. 4. FIG. 6A is a perspective view of a toner adhesion amount measuring apparatus according to another embodiment of the present invention, and FIG. 6B is a front view thereof. FIG. 7 is a diagram showing the relationship between the sensor angle deviation and the amount of received light when the projection slit has a circular shape of φ1 mm and an elliptical shape with a minor axis of 1 mm × major axis of 2 mm in the toner adhesion amount measuring apparatus of FIG. 6. is there. FIGS. 8A and 8B are diagrams showing a toner adhesion amount measuring apparatus according to another embodiment of the present invention, FIG. 8A being a perspective view when a polarizing filter is attached, and FIG. 8B being a plan view after being attached. is there. FIGS. 9A and 9B are views showing a toner adhesion amount measuring apparatus according to another embodiment of the present invention, FIG. 9A is a perspective view when three polarizing filters are attached, and FIG. It is a front view. FIGS. 10A and 10B are diagrams showing a toner adhesion amount measuring apparatus according to another embodiment of the present invention. FIG. 10A is a perspective view when two polarizing filters are attached, and FIG. It is a front view. 11A and 11B are diagrams illustrating a toner adhesion amount measuring apparatus according to an embodiment of the present invention, in which FIG. 11A is a perspective view when an optical unit holder is attached, and FIG. 11B is a partial cross-sectional view from the lateral direction after attachment. FIG. 11C is a schematic cross-sectional view of a plastic piece on which an optical lens is formed. FIG. 12 is a diagram illustrating a feedback control function of the toner adhesion amount measuring device of FIG. 11. It is a perspective view of a regular reflection type toner adhesion amount measuring apparatus according to a conventional example. It is a top view of the toner adhesion amount measuring apparatus of FIG. It is a figure which shows the relationship between the toner adhesion amount and the light reception amount by the toner adhesion amount measuring apparatus of FIG. It is a perspective view of the toner adhesion amount measuring apparatus using the polarization separation prism according to another conventional example. It is a perspective view of the toner adhesion amount measuring apparatus using a polarizing filter according to another conventional example. FIG. 18 is a plan view of the toner adhesion amount measuring device of FIG. 17. It is a perspective view of resin mold structure LED. FIG. 6 is a diagram illustrating a dead angle depending on an incident angle to a photosensitive member. FIG. 6 is a diagram showing a positional deviation of reflected light due to a change in distance between a photoconductor and a toner adhesion amount measuring device. It is the figure which showed the position shift of the chip | tip of a resin mold structure LED, and a lead frame. FIG. 4 is a diagram showing a light receiving position shift caused by a position shift of an irradiation position on a photoconductor. FIG. 24 is a diagram showing the relationship between the toner adhesion amount and the light reception amount when the irradiation position on the photoconductor in FIG. 23 is shifted.

Explanation of symbols

1 LED chip (light emitting element)
2 Photosensitive drum 3 Toner 4 P-wave light receiving photodiode (first light receiving element)
5 S-wave light receiving photodiode (second light receiving element)
6 Polarizing filter for light projection (P wave)
8 First light-receiving polarizing filter (P wave)
9 Second light-receiving polarizing filter (P wave)
DESCRIPTION OF SYMBOLS 10 Circuit board 11 Optical unit holder 12 Connector 13 Light-shielding wall 14 Transparent mold resin 15 Gold wire or aluminum wire 16 Bump 17 Light emission side slit 18 LED projection light distribution 19 Plastic piece 19a which formed the convex optical lens Convex lens part back surface 19b Convex lens Partial surface 19c Convex lens partial surface 19d Convex lens partial back surface 19e Protrusion 19f Protrusion 20 Third light receiving element 21 Reflector 51 Light projecting element 52 Photosensitive drum 53 Toner 54 Light receiving element 55 Light receiving element 56 Polarizing filter 57 Polarizing separation prism 58 Polarizing filter 59 Polarizing filter 60 circuit board 61 optical unit holder 62 connector 63 lead frame 64 resin mold 65 LED chip 66 light shielding wall 67 comparator

Claims (12)

Light receiving optical system including a light projecting element that irradiates light onto an image carrier to which toner adheres and a light receiving element that receives reflected light from the image carrier of light irradiated from the light projecting optical system And having a system
The light projecting optical system irradiates the image carrier with the light from the light projecting element as single polarized light that has passed through the light polarizing filter,
The light receiving optical system receives first polarized light in a direction parallel to the single polarized light irradiated from the light projecting optical system by the first light receiving polarizing filter, out of the reflected light component from the image carrier. A first light receiving element having a light receiving element and a second light receiving element for receiving polarized light orthogonal to the single polarized light emitted from the light projecting optical system by the second light receiving polarizing filter; A toner adhesion amount measuring apparatus for measuring a toner adhesion amount based on a difference between a light reception signal at the second light reception signal and a light reception signal at a second light receiving element,
The light projecting element and the first and second light receiving elements are mounted on the same circuit board and covered with an optical unit holder.
The optical unit holder is provided with a recess, and the projection polarizing filter and the first and second light receiving polarization filters are fitted into the recess,
A projecting polarizing filter and first and second light receiving polarizing filters are fixed to the outer surface of the optical unit holder, and a plastic piece having a convex optical lens is fixed to the filter and the outer surface of the optical unit holder. Positioning and fixing the polarizing filter and the convex optical lens part,
A light shielding wall is provided between the light projecting element and the first and second light receiving elements, and the light shielding wall extends from the optical unit holder side to the circuit board side,
Attaching amount of toner, characterized in that a slit for restricting the optical path of the irradiation light from the light projecting element to the image carrier is provided in the optical unit holder, and the light projection angle and the light reception angle with respect to the image carrier are set to 19 ° or less. measuring device.   A toner adhesion amount measuring apparatus, wherein the semiconductor chip used for the light projecting element and the light receiving element according to claim 1 is directly mounted on a circuit board without a metal frame. 2. A toner adhesion amount measuring apparatus, wherein the light projecting element according to claim 1 and the first and second light receiving elements are arranged on substantially the same straight line . The slit for limiting an optical path for irradiating light from the light projecting element to the image carrier according to claim 1 is elliptical or rectangular, and the major axis direction of the slit is the first and second light receiving element arrangement directions. A toner adhesion amount measuring device which is parallel . A third light receiving element for detecting the light amount of the light emitting element is disposed on the circuit board according to claim 1 , and the light emitted from the first light projecting element is reflected by a reflector provided in the optical unit holder, and the reflection is performed. A toner adhesion amount measuring apparatus having a function of maintaining a light amount of a light projecting element at a constant value by receiving light with a third light receiving element and feeding it back to the first light projecting element . Light receiving optical system including a light projecting element that irradiates light onto an image carrier to which toner adheres and a light receiving element that receives reflected light from the image carrier of light irradiated from the light projecting optical system And having a system
The light projecting optical system irradiates the image carrier with the light from the light projecting element as single polarized light that has passed through the light polarizing filter,
The light receiving optical system receives first polarized light in a direction parallel to the single polarized light irradiated from the light projecting optical system by the first light receiving polarizing filter, out of the reflected light component from the image carrier. A first light receiving element having a light receiving element and a second light receiving element for receiving polarized light orthogonal to the single polarized light emitted from the light projecting optical system by the second light receiving polarizing filter; A toner adhesion amount measuring apparatus for measuring a toner adhesion amount based on a difference between a light reception signal at the second light reception signal and a light reception signal at a second light receiving element,
The light projecting polarizing filter and the first light receiving polarizing filter are constituted by a single polarizing filter,
The light projecting element and the first and second light receiving elements are mounted on the same circuit board and covered with an optical unit holder.
A light shielding wall is provided between the light projecting element and the first and second light receiving elements, and the light shielding wall extends from the optical unit holder side to the circuit board side,
Attaching amount of toner, characterized in that a slit for restricting the optical path of the irradiation light from the light projecting element to the image carrier is provided in the optical unit holder, and the light projection angle and the light reception angle with respect to the image carrier are set to 19 ° or less. measuring device. 7. A toner adhesion amount measuring apparatus , wherein the semiconductor chip used for the light projecting element and the light receiving element according to claim 6 is directly mounted on a circuit board without a metal frame . 7. A toner adhesion amount measuring apparatus according to claim 6 , wherein a concave portion is provided in the optical unit holder, and a light projecting polarizing filter and first and second light receiving polarizing filters are fitted in the concave portion . 9. A plastic piece in which a light projecting polarizing filter and first and second light receiving polarizing filters are fixed to an outer surface of an optical unit holder according to claim 8, and a convex optical lens is formed on the outer surface of the filter and the optical unit holder. And fixing the polarizing filter and the convex optical lens portion to fix the position of the polarizing filter. 7. A toner adhesion amount measuring apparatus, wherein the light projecting element according to claim 6 and the first and second light receiving elements are arranged on substantially the same straight line. The slit for limiting the optical path for irradiating light from the light projecting element to the image carrier according to claim 6 is elliptical or rectangular, and the major axis direction of the slit is the first and second light receiving element arrangement directions. A toner adhesion amount measuring device which is parallel. A third light receiving element for detecting the light amount of the light emitting element is disposed on the circuit board according to claim 6, and the light emitted from the first light projecting element is reflected by a reflector provided in the optical unit holder, and the reflection A toner adhesion amount measuring apparatus having a function of maintaining a light amount of a light projecting element at a constant value by receiving light with a third light receiving element and feeding it back to the first light projecting element.

Images