Blowing apparatus including piezoelectric valve and optical granular material sorting machine using the blowing apparatus

The present invention has an object to provide a blowing apparatus wherein a piezoelectric element is unlikely to cause insulation deterioration leading to burnout during use of the blowing apparatus. The blowing apparatus of the present invention blows compressed gas supplied from a compressed gas supply unit through a nozzle hole of a nozzle unit by opening a piezoelectric valve. The blowing apparatus comprises a humidity sensor detecting a humidity of the compressed gas inside a flow path unit, and a humidity control unit comparing a detected value of the humidity detected by the humidity sensor with a set value. If the humidity of the compressed gas inside the flow path unit detected by the humidity sensor is equal to or greater than the set value, the humidity control unit replaces the compressed gas inside the flow path unit with the compressed gas whose humidity is less than the set value and which is supplied from the compressed gas supply unit, before starting to use the blowing apparatus.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is the National Stage of International Application No. PCT/JP2016/075945 filed Sep. 5, 2016 and claims benefit of Japanese Application No. 2015-176659 filed on Sep. 8, 2015, which are herein incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a blowing apparatus including a piezoelectric valve opening and closing a valve using displacement of a piezoelectric element and an optical granular material sorting machine using the blowing apparatus.

BACKGROUND ART

There has conventionally known an optical granular material sorting machine that sorts non-defective products and defective products by blowing granular materials such as grains and resin pellets or removes foreign materials or the like mixed into the granular materials by air blowing.

This type of granular material sorting machine sorts the granular materials falling along a predetermined trajectory from an end portion of a conveying path by removing defective products based on a detection signal indicating the defective products or the like by air blowing.

The above granular material sorting machine blows only the defective products or the like by air from among the granular materials falling continuously and in large quantity. In order to blow only the defective products or the like with high accuracy while keeping other granular materials intact, the blowing apparatus needs to include a valve with excellent responsiveness.

In light of this, there has been proposed a piezoelectric valve that can open and close a valve at high speed using a piezoelectric element (see Patent Literature 1).

The piezoelectric valve uses characteristics of the piezoelectric element having excellent high-speed responsiveness and includes a displacement magnification mechanism that magnifies a small displacement of the piezoelectric element based on lever principle.

In the piezoelectric valve, when a voltage is applied to the piezoelectric element, a displacement in an extending direction of the piezoelectric element is transmitted to a valve body via the displacement magnification mechanism and causes the valve body to quickly move and the piezoelectric valve to open.

Then, in the piezoelectric valve, when the voltage application to the piezoelectric element is canceled, a restoring force of the piezoelectric element trying to return to its original state is transmitted to the valve body via the displacement magnification mechanism and causes the valve body to quickly abut against a valve seat and the piezoelectric valve to close.

Accordingly, the blowing apparatus including the piezoelectric valve includes a blowing nozzle incorporating a plurality of piezoelectric valves arranged in parallel with each other; and a compressed air supply device supplying compressed air to the blowing nozzle. A drive unit selectively drives the plurality of piezoelectric valves to blow the compressed air through each nozzle hole of the blowing nozzle.

Moreover, since the responsiveness at the time of opening and closing the piezoelectric valve is markedly superior to that of the conventional electromagnetic valve, the optical granular material sorting machine using the blowing apparatus can blow off the defective products or the like with high precision and is less likely to blow off the non-defective products.

Furthermore, the piezoelectric element has excellent characteristics such as low energy consumption associated with operation, being suitable for high-speed operation, and reduction in size.

However, since the piezoelectric element is vulnerable to a high-humidity environment, the use of the piezoelectric valve in a high-humidity environment may cause an insulation deterioration which is considered to be caused by migration, leading to burnout.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Accordingly, the present invention has an object to provide a blowing apparatus including a piezoelectric valve opening and closing a valve using displacement of a piezoelectric element, wherein the piezoelectric element is unlikely to cause insulation deterioration leading to burnout during use of the blowing apparatus.

Further, the present invention has an object to provide an optical granular material sorting machine using the blowing apparatus, wherein the piezoelectric element provided in the blowing apparatus is unlikely to cause insulation deterioration leading to burnout during use of the blowing apparatus.

Solution to Problem

In order to achieve the above object, the present invention provides a blowing apparatus comprising:

a piezoelectric valve opening and closing a valve using displacement of a piezoelectric element;

a compressed gas supply unit including a compressor and means of drying compressed gas compressed by the compressor such that a humidity thereof is less than a set value;

a nozzle unit blowing the compressed gas supplied from the compressed gas supply unit through a nozzle hole; and

a flow path unit supplying the compressed gas from the compressed gas supply unit to the nozzle unit, wherein

the compressed gas supplied from the compressed gas supply unit is blown through the nozzle hole of the nozzle unit by opening the piezoelectric valve, the blowing apparatus comprising:

a humidity sensor detecting a humidity of the compressed gas inside the flow path unit; and

a humidity control unit comparing a detected value of the humidity detected by the humidity sensor with a set value, and wherein

if the humidity of the compressed gas inside the flow path unit detected by the humidity sensor is equal to or greater than the set value, the humidity control unit controls replacing of the compressed gas inside the flow path unit with the compressed gas whose humidity is less than the set value and which is supplied from the compressed gas supply unit, before starting to use the blowing apparatus.

It is preferable in the present invention that the humidity control unit repeatedly controls opening and closing of the piezoelectric valve to discharge the compressed gas whose humidity is equal to or greater than the set value through the nozzle hole, thereby to replace the compressed gas inside the flow path unit with the compressed gas supplied from the compressed gas supply unit.

It is preferable in the present invention that a compressed gas discharge valve is provided on the nozzle unit side of the flow path unit, and the humidity control unit controls opening of the discharge valve to discharge the compressed gas whose humidity is equal to or greater than the set value through the discharge valve, thereby to replace the compressed gas inside the flow path unit with the compressed gas supplied from the compressed gas supply unit.

It is preferable in the present invention that the piezoelectric valve comprises a gas pressure chamber receiving the compressed gas supplied from the compressed gas supply unit; and a gas discharge passage discharging the compressed gas from the gas pressure chamber, and the piezoelectric valve further comprises a valve body disposed in the gas pressure chamber and opening and closing the gas discharge passage; a piezoelectric element generating a driving force necessary for operation of the valve body as a displacement; and a displacement magnification mechanism magnifying the displacement of the piezoelectric element to act on the valve body, wherein a voltage is applied to the piezoelectric element to expand the piezoelectric element to open the valve body.

In order to achieve the above object, the present invention provides an optical granular material sorting machine comprising: transfer means of transferring objects to be sorted; optical detection means of detecting objects to be sorted falling from an end portion of the transfer means at a detection position; and a blowing apparatus disposed further below the optical detection means and blowing the objects to be sorted by blowing compressed gas based on a detection result by the optical detection means, wherein

the blowing apparatus is the blowing apparatus according to any one of the above, and if the humidity of the compressed gas inside the flow path unit detected by the humidity sensor is equal to or greater than the set value, the compressed gas inside the flow path unit is replaced with the compressed gas whose humidity is less than the set value and which is supplied from the compressed gas supply unit, before starting to use the blowing apparatus.

Advantageous Effects of Invention

According to the blowing apparatus of the present invention, before starting to use the blowing apparatus, the humidity sensor detects the humidity of the compressed gas inside the flow path unit. If the detected humidity is equal to or greater than the set value, the humidity control unit replaces the compressed gas inside the flow path unit with the compressed gas whose humidity is less than the set value and which is supplied from the compressed gas supply unit. Therefore, the piezoelectric element used in the piezoelectric valve is unlikely to cause insulation deterioration leading to burnout during use of the blowing apparatus.

The blowing apparatus of the present invention is assumed to operate such that the humidity control unit repeats opening and closing of the piezoelectric valve to discharge the compressed gas whose humidity is equal to or greater than the set value through the nozzle hole, thereby to replace a high humidity compressed gas inside the flow path unit with a low humidity compressed gas supplied from the compressed gas supply unit. Then, the surface of the piezoelectric element is heated by expansion and contraction of the piezoelectric element during opening and closing of the piezoelectric valve, thus increasing the surface temperature of the piezoelectric element and resultantly decreasing the relative humidity of the surface of the piezoelectric element. Therefore, even if the high humidity compressed gas inside the flow path unit is discharged through the nozzle hole, the piezoelectric element is unlikely to cause insulation deterioration leading to burnout.

The blowing apparatus of the present invention is assumed to operate such that the compressed gas discharge valve is provided on the nozzle unit side of the flow path unit and the humidity control unit opens the discharge valve to discharge the compressed gas whose humidity is equal to or greater than the set value from the discharge valve thereby to replace the high humidity compressed gas inside the flow path unit with the low humidity compressed gas supplied from the compressed gas supply unit. Then, the high humidity compressed gas inside the flow path unit can be easily discharged.

The optical granular material sorting machine of the present invention is such that the blowing apparatus is the blowing apparatus according to any one of the above and if the humidity of the compressed gas inside the flow path unit detected by the humidity sensor is equal to or greater than the set value, the compressed gas inside the flow path unit is replaced with the compressed gas whose humidity is less than the set value and which is supplied from the compressed gas supply unit, before starting to use the blowing apparatus. Therefore, the piezoelectric element provided in the blowing apparatus is unlikely to cause insulation deterioration leading to burnout during use of the blowing apparatus.

DESCRIPTION OF EMBODIMENT

FIG. 1illustrates a perspective view of a piezoelectric valve.FIG. 2illustrates an exploded assembly view of the piezoelectric valve.FIG. 3illustrates an explanatory view of an actuator.FIG. 4illustrates an explanatory view of a state where the actuator is fixed to a valve seat plate.FIG. 5illustrates a sectional view of the piezoelectric valve, explaining a state where the valve seat plate is disposed in a valve main body.

A piezoelectric valve10includes a valve main body20, a valve seat plate25disposed inside the valve main body20and fixed to the valve main body20, and an actuator30fixed to both surfaces of the valve seat plate25with screws.

The valve main body20is a case whose front surface is opened and includes therein a gas pressure chamber receiving compressed gas supplied from an external compressed gas supply source (unillustrated).

Moreover, the front surface of the valve main body20includes a connector portion50. The front surface of the connector portion50further includes a gas inlet port51for sucking compressed gas into the valve main body20and gas outlet ports52for discharging the compressed gas.

The valve seat plate25includes an attachment portion of the actuator30on both surfaces thereof and a valve seat26abutted by a later-described valve body31of the actuator30. The valve seat plate25includes a gas discharge passage formed to communicate from the valve seat surface of the valve seat26to the outlet ports52being opened in the front surface of the connector portion50.

Moreover, the front surface of the valve seat plate25includes a lid material28for closing the opening of the case. The lid material28includes a gas inlet passage formed to communicate from the inlet port51being opened in the front surface of the connector portion50into the valve main body20.

As illustrated inFIG. 3, the actuator30includes a valve body31made of rubber, preferably, sliding rubber, a piezoelectric element32for generating a driving force necessary for operation of the valve body31as displacement, and a displacement magnification mechanism33for magnifying the displacement of the piezoelectric element32to act on the valve body31.

The displacement magnification mechanism33includes a displacement magnification unit34for magnifying the displacement of the piezoelectric element32, and a displacement transmission unit35for transmitting the displacement of the piezoelectric element32to the displacement magnification unit34, each of which is disposed symmetrically with respect to an axis in the operation direction of the valve body31, herein, a straight line (hereinafter referred to as “center line”) connecting the longitudinal axes of the valve body31and the piezoelectric element32.

The displacement transmission unit35includes a U-shaped base substrate36joined to one end of the piezoelectric element32, and a cap member37joined to the other end of the piezoelectric element32. The piezoelectric element32is disposed in a space of the U-shaped base substrate36, and then the displacement magnification mechanism33is disposed symmetrically about the longitudinal axis of piezoelectric element32.

Here, the piezoelectric element32is located in a space of the U-shaped base substrate36and incorporated between the U-shaped bottom portion of the base substrate36and the cap member37. By plastically deforming the U-shaped bottom portion of the base substrate36, the one end is joined to the U-shaped bottom portion of the base substrate36and the other end is joined to the cap member37.

The displacement magnification unit34includes first and second displacement magnification units34aand34bdisposed symmetrically with respect to the center line.

The first displacement magnification unit34aincludes first and second hinges39and40, a first arm41, and a first leaf spring42. One end of the first hinge39is integrated with an end on one side of the U-shaped base substrate36, and one end of the second hinge40is integrated with the cap member37. An outer end portion of the first arm41is joined to one end of the first leaf spring42, and the other end of the first leaf spring42is joined to a side end portion on one side of the valve body31.

Meanwhile, the second displacement magnification unit34bincludes third and fourth hinges43and44, a second arm45, and a second leaf spring46. One end of the third hinge43is integrated with an end on the other side of the U-shaped base substrate36, and one end of the fourth hinge44is integrated with the cap member37. An outer end portion of the second arm45is joined to one end of the second leaf spring46, and the other end of the second leaf spring46is joined to a side end portion on the other side of the valve body31.

Here, the displacement magnification mechanism33can be integrally molded, for example, by punching out a metal material such as a stainless-steel material.

In the piezoelectric valve10, the actuator30operates such that when power is supplied to the piezoelectric element32in a closed-valve state, the piezoelectric element32expands. The displacement caused by expansion of the piezoelectric element32is expanded by lever principle with the first and third hinges39and43as the fulcrum, the second and fourth hinges40and44as the point of effort, and the outer end portions of the first and second arms41and45as the point of application of force in the displacement magnification mechanism33to largely displace the outer end portions of the first and second arms41and45.

Then, the displacement of the outer end portions of the first and second arms41and45separates the valve body31from the valve seat26via the first and second leaf springs42and46to open the gas discharge passage.

Meanwhile, the actuator30operates such that when the conduction to the piezoelectric element32is released, the piezoelectric element32contracts. Then, the contraction causes the valve body31to be seated on the valve seat26via the displacement magnification mechanism33to close the gas discharge passage.

Then, the blowing apparatus including the piezoelectric valve10will be described.FIG. 6illustrates a control block diagram of the blowing apparatus. The blowing apparatus110includes a compressed gas supply source120including a compressor and a dryer such as a freezing type dryer and an adsorption type dryer for drying gas compressed by the compressor; a regulator122for regulating the pressure of the compressed gas supplied from the compressed gas supply source120; a blowing nozzle130for blowing the compressed gas whose pressure is regulated by the regulator122through a plurality of nozzle holes thereof; and a pipe141and a manifold143serving as a flow path for supplying the compressed gas from the compressed gas supply source to the blowing nozzle130.

The blowing apparatus110includes a plurality of piezoelectric valves10illustrated inFIGS. 1 to 5disposed in parallel in the blowing nozzle130or along the flow path near the blowing nozzle130, and blows the low humidity compressed gas supplied from the compressed gas supply source120through each nozzle hole of the blowing nozzle130by opening and closing the piezoelectric valves10.

In the blowing apparatus110, the pipe141includes a pressure sensor145for detecting the pressure inside the flow path; and a humidity sensor147for detecting the relative humidity of the gas inside the flow path.

Moreover, the blowing apparatus110includes a humidity control device150and a drive unit160. The humidity control device150compares the set value of a humidity that is assumed to be inputted by the operator with the value of the humidity detected by the humidity sensor147. The drive unit160drives opening and closing of the piezoelectric valve10or a later-described discharge valve based on a signal from the humidity control device150.

Before starting to use the blowing apparatus110, the humidity control device150uses a power supply signal of the compressed gas supply source120and a pressure signal of the pressure sensor145as the input signals to compare the set value of the humidity (for example, 30% RH) with the value of the humidity detected by the humidity sensor147in the state where the low humidity compressed gas is supplied from the compressed gas supply source120.

Then, as a result of the comparison by the humidity control device150, if the value of the humidity detected by the humidity sensor147is equal to or greater than the set value (for example, 30% RH), the high humidity compressed gas existing (remaining) inside the flow path is replaced with the compressed gas with low humidity (for example, less than 30% RH) supplied from the compressed gas supply source120, before starting to use the blowing apparatus110.

As described above, the blowing apparatus110replaces the high humidity compressed gas existing inside the flow path with the low humidity compressed gas, before starting to use the blowing apparatus110. Then, the piezoelectric element32used in the piezoelectric valve10is unlikely to cause insulation deterioration leading to burnout during use of the blowing apparatus110.

The blowing apparatus110can discharge the high humidity compressed gas through the nozzle holes of the blowing nozzle130by causing the drive unit160to repeatedly drive opening and closing of the piezoelectric valve10at a high speed (such as about 100 Hz) based on the signal from the humidity control device150.

As described above, the blowing apparatus110needs not have any special device configuration as long as when the high humidity compressed gas existing inside the flow path is replaced with the low humidity compressed gas supplied from the compressed gas supply source120, the high humidity compressed gas is discharged through the nozzle holes of the blowing nozzle130.

Further, blowing apparatus110is assumed to operate such that the drive unit160repeatedly drives opening and closing of the piezoelectric valve10at high speed. Then, the surface of the piezoelectric element32is heated by expansion and contraction of the piezoelectric element32during opening and closing of the piezoelectric valve10, thus increasing the surface temperature of the piezoelectric element32and resultantly decreasing the relative humidity of the surface of the piezoelectric element32. Therefore, even if the high humidity compressed gas existing inside the flow path is discharged through the nozzle holes of the blowing nozzle130, the piezoelectric element32is unlikely to cause insulation deterioration leading to burnout.

Moreover, the blowing apparatus110is configured such that an unillustrated discharge valve such as a magnetic valve is provided on the end portion side of the manifold143. Then, the drive unit160opens the discharge valve based on the signal from the humidity control device150. Thus, the high humidity compressed gas can be discharged from the discharge valve.

As described above, the blowing apparatus110is assumed to operate such that when the high humidity compressed gas existing inside the flow path is replaced with the low humidity compressed gas supplied from the compressed gas supply source120, the high humidity compressed gas is discharged from the discharge valve. Then, the high humidity compressed gas can be easily discharged.

Note that the humidity control device150uses the pressure signal of the pressure sensor145as the input signal to compare the set value with the value detected by the humidity sensor147. Then, if the detected value is equal to or greater than the set value, the remaining gas is replaced with the low humidity gas, before starting to use the blowing apparatus110. This comparison operation between the set value and the detected value may be continuously (in seconds) performed not only before but also after starting to use the blowing apparatus110.

Therefore, even if the humidity of the compressed gas increases due to a failure of a dryer or the like during use of the blowing apparatus110, the blowing apparatus110can be stopped to prevent insulation deterioration phenomena of the piezoelectric element32used in the piezoelectric valve10.

Then, the optical granular material sorting machine using the blowing apparatus110will be described.

FIG. 7is a sectional side view illustrating the simplified internal structure of the essential parts of the optical granular material sorting machine.FIG. 8illustrates a control block diagram of the optical granular material sorting machine.

The optical granular material sorting machine210includes a granular material supply unit including a tank220and a vibrating feeder230disposed at an upper portion thereof. An inclined chute240having a predetermined width is disposed below the granular material supply unit.

Granular materials supplied from the granular material supply unit spread out across the width direction on the inclined chute240and flow down naturally in a continuous manner, and then are released into the air along a predetermined falling trajectory from the lower end thereof.

At least a pair of optical detection devices250aand250bare disposed facing each other before and after the predetermined falling trajectory to image granular materials at a granular material detection position0extending linearly in parallel in the width direction of the inclined chute240. Each of the optical detection devices250aand250bincludes imaging means251aand251bsuch as a CCD camera incorporating a CCD line sensor; illumination means252aand252bsuch as a fluorescent lamp and an LED; and backgrounds253aand253bserving as the background for use in imaging the granular materials.

Moreover, the blowing apparatus110for removing the defective products or the like by blowing the compressed gas is disposed below the granular material detection position O. The blowing apparatus110is illustrated inFIG. 6and includes blowing nozzles130incorporating a plurality of the piezoelectric valves10arranged in parallel with each other; a compressed gas supply source120supplying compressed gas to the blowing nozzle130; and a flow path including a pipe141connecting the compressed gas supply source120and the blowing nozzle130, wherein the flow path includes a pressure sensor145detecting the pressure inside the flow path and a humidity sensor147detecting the relative humidity of the gas inside the flow path.

Furthermore, the optical granular material sorting machine210includes a drive unit272for driving expanding and contracting of the piezoelectric element32of the piezoelectric valve10based on the detection result of the granular materials released from the lower end of the inclined chute240by each of the optical detection devices250aand250b.

In the optical granular material sorting machine210, the granular materials spread out across the width direction on the inclined chute240and flow down naturally in a continuous manner, and then are released into the air along a predetermined falling trajectory from the lower end thereof. Then, the granular materials are imaged at the granular material detection position0by the imaging means251aand251bof the respective optical detection devices250aand250b,and the imaged data is transmitted to the control device260. The control device260identifies the granular materials to remove the defective products or the like based on the imaged data; acquires information about the size and the like of the granular materials; and transmits a discharge signal indicating the defective products or the like to the drive unit272.

The blowing apparatus110selectively drives the plurality of piezoelectric valves10based on the discharge signal transmitted to the drive unit272to blow the compressed gas through each nozzle hole of the blowing nozzle130provided corresponding to each position in the width direction toward the defective products or the like passing through the granular material discharge position E extending linearly in parallel in the width direction of the inclined chute240.

Then, the defective products or the like blown by the air through each nozzle hole of the blowing nozzle130are discharged outside through the defective product outlet port281. Meanwhile, the non-defective products or the like passing along the predetermined falling trajectory as is without being blown off are recovered through the non-defective product outlet port282.

Here, even if the blowing apparatus110is used in the optical granular material sorting machine210, at the time of starting the operation of the optical granular material sorting machine210, before starting to use the blowing apparatus110, as described above, the high humidity compressed gas existing (remaining) inside the flow path can be replaced with the low humidity compressed gas.

In this case, the humidity control unit of the control device260in the optical granular material sorting machine210serves as the humidity control device150of the blowing apparatus110illustrated inFIG. 6.

Thus, as long as the blowing apparatus110replaces the high humidity compressed gas existing inside the flow path with the low humidity compressed gas before starting to use the blowing apparatus110, even if the optical granular material sorting machine210is operated, as described above, the piezoelectric element32used in the piezoelectric valve10is unlikely to cause insulation deterioration leading to burnout during use of the blowing apparatus110.

Moreover, if the humidity sensor147detects a humidity equal to or greater than the set value (for example, 30% RH) during operation of the optical granular material sorting machine210, the control device26issues a warning or stops the operation of the optical granular material sorting machine210, thereby securing the safety of the piezoelectric element32used in the piezoelectric valve10.

Examples of typical granular materials to be sorted by the optical granular material sorting machine include cereal grains, particularly rice grains, but are not necessarily limited to grains, and any materials can be used as long as the materials have a size and mass that can be blown off by air blowing.

It should be noted that the present invention is not limited to the above embodiment, and it is obvious that the configuration can be appropriately modified as long as without departing from the scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention provides a blowing apparatus including a piezoelectric valve opening and closing a valve using displacement of a piezoelectric element and is extremely useful in that the piezoelectric element is unlikely to cause insulation deterioration leading to burnout during use of the blowing apparatus.

Moreover, the present invention provides an optical granular material sorting machine using the blowing apparatus and is extremely useful in that the piezoelectric element provided in the blowing apparatus is unlikely to cause insulation deterioration leading to burnout during use of the blowing apparatus.

REFERENCE SIGNS LIST