Patent Description:
Weighing apparatus are known which, as in patent document <NUM> (<CIT>) for example, convey an article and measure the weight of the article as it is being conveyed.

In such weighing apparatus, sometimes defects occur in the weighing due, for example, to degradation of constituent devices over time. Because there are multiple factors that give rise to defects, it usually requires a long amount of time to identify the cause. To address this, patent document <NUM> (<CIT>) discloses acquiring a weigh signal output by a detection unit when a conveyance unit is driven in a state in which there is no article on the conveyance unit in regard to a single conveyance speed, calculating variance per vibration component, and identifying the defective area of a rotational component based on the calculation result.

<CIT> discloses an article inspection apparatus capable of accurately adjusting a carry-in interval of an inspection object.

However, because there are numerous factors that give rise to defects in the weighing, the method of patent document <NUM> (<CIT>) sometimes has difficulty accurately inferring the factor from among various defect factors.

It is an object of the present invention to provide a weighing apparatus that conveys an article and weighs the article as it is being conveyed, the weighing apparatus being able to accurately infer defect factors.

A weighing apparatus of a first aspect measures the weight of an article while conveying the article. The weighing apparatus includes a conveyance unit that conveys the article, a detection unit, and a control unit. The conveyance unit has a variable conveyance speed. The detection unit is configured to detect the weight of the conveyance unit or, in a case where the conveyance unit is conveying the article, the weight of the conveyance unit and the weight of the article on the conveyance unit and outputs a weigh signal. The control unit is configured to generate statistical information from the weigh signals output by the detection unit in a state in which there is no article on the conveyance unit in regard to each of plural conveyance speeds. The control unit is configured to determine and output candidates for defect factors based on the statistical information for each of the conveyance speeds.

In the weighing apparatus of the first aspect, as candidates for defect factors are determined based on the statistical information obtained in regard to the plural conveyance speeds, candidates for defect factors can be accurately inferred in a case where a defect is occurring in the weighing. For that reason, a worker maintaining the weighing apparatus can eliminate the defect in a short amount of time.

A weighing apparatus of a second aspect is the weighing apparatus of the first aspect, wherein the statistical information generated by the control unit include statistical information generated from the weigh signal output from the detection unit in a state in which there is no article on the conveyance unit in a case where the conveyance speed is zero.

In the weighing apparatus of the second aspect, candidates for defect factors in the weighing apparatus are determined based on the statistical information obtained in a case where the conveyance speed is zero, that is, while the conveyance unit is stopped. Therefore, candidates for defect factors can be inferred particularly accurately in a case where a defect is occurring in the weighing. For that reason, a worker maintaining the weighing apparatus can eliminate the defect in a short amount of time.

A weighing apparatus of a third aspect is the weighing apparatus of the second aspect, wherein the defect factors include at least one of defect factors relating to the installation state of the weighing apparatus and defect factors relating to the installation environment of the weighing apparatus.

In the weighing apparatus of the third aspect, the potential for not only defects in constituent parts of the weighing apparatus but also other types of defects can be detected, and the amount of time a worker maintaining the weighing apparatus needs to identify the cause of a defect can be shortened.

A weighing apparatus of a fourth aspect is the weighing apparatus of any of the first aspect to the third aspect, wherein the control unit has plural filters with mutually different characteristics which are configured to be used to filter the weigh signals. The control unit is configured to generate the statistical information from signals obtained by filtering, with each of the plural filters, the weigh signal output by the detection unit in a state in which there is no article on the conveyance unit in regard to each of the plural conveyance speeds. The control unit is configured to determine and output the candidates for defect factors based on the statistical information for each of the conveyance speeds and for each of the filters.

In the weighing apparatus of the fourth aspect, as candidates for defect factors are determined using the statistical information obtained from signals obtained by processing signals with different filters, candidates for defect factors can be accurately inferred in a case where a defect is occurring in the weighing. For that reason, a worker maintaining the weighing apparatus can eliminate the defect in a short amount of time.

A weighing apparatus of a fifth aspect is the weighing apparatus of the fourth aspect and further includes a storage unit. In the storage unit, standards for the statistical information are stored for each of the conveyance speeds and for each of the filters. The control unit is configured to determine and output the candidates for defect factors based on results of a comparison of the generated statistical information for each of the conveyance speeds and for each of the filters with the standards for the corresponding conveyance speeds and filters stored in the storage unit.

In the weighing apparatus of the fifth aspect, candidates for defect factors can be accurately inferred by comparing the generated statistical information with the standards.

A weighing apparatus of a sixth aspect is the weighing apparatus of the fifth aspect, wherein the statistical information generated from signals obtained by filtering, with each of the plural filters, the weigh signals output by the detection unit in a state in which there is no article on the conveyance unit in regard to each of the plural conveyance speeds at the time of a test operation of the weighing apparatus are stored as the standards in the storage unit.

In the weighing apparatus of the sixth aspect, the statistical information obtained at the time of a test operation of the weighing apparatus are used as the standards, so candidates for defect factors can be inferred based on characteristics unique to each weighing apparatus.

A weighing apparatus of a seventh aspect is the weighing apparatus of any of the first aspect to the sixth aspect, wherein the statistical information includes at least one of standard deviation, dispersion, a difference between a maximum value and a minimum value, a maximum value, and a minimum value.

In the weighing apparatus of the present invention, as candidates for defect factors are determined based on the statistical information obtained in regard to the plural conveyance speeds, candidates for defect factors can be accurately inferred in a case where a defect is occurring in the weighing. For that reason, a worker maintaining the weighing apparatus can eliminate the defect in a short amount of time.

A weighing apparatus <NUM> pertaining to an embodiment of the weighing apparatus of the invention will be described with reference to the drawings.

The overall configuration of the weighing apparatus <NUM> will be described with reference to <FIG>. <FIG> is a schematic front view of the weighing apparatus <NUM> seen from the front. <FIG> is a block diagram of the weighing apparatus <NUM>. <FIG> is a schematic plan view of main parts of the weighing apparatus <NUM> seen from above.

The weighing apparatus <NUM> is a weighing apparatus that weighs an article P while conveying the article P.

As shown in <FIG>, the weighing apparatus <NUM> mainly has a conveyance device <NUM> and a detection device <NUM>. The weighing apparatus <NUM> also has a control device <NUM> (see <FIG>) that controls the operations of the conveyance device <NUM> and the detection device <NUM>.

It will be noted that the control device <NUM> has, in addition to the function of controlling the operations of the conveyance device <NUM> and the detection device <NUM>, the function of determining whether there is a defect in the weighing by the weighing apparatus <NUM>. Moreover, in a case where there is a defect in the weighing by the weighing apparatus <NUM>, the control device <NUM> has the function of determining candidates for defect factors in the weighing apparatus <NUM> and outputting the determined candidates for defect factors in the weighing apparatus <NUM>.

The conveyance device <NUM> receives and conveys the article P, which is supplied from an upstream process not shown in the drawings (e.g., a process to manufacture the article P). Specifically, the conveyance device <NUM> conveys the article P to a place where its weight is detected by the detection device <NUM>.

The detection device <NUM> detects the weight of the article P conveyed by the conveyance device <NUM> and outputs a weigh signal corresponding to the detected weight to the control device <NUM>. The control device <NUM> calculates a weight W of the article P based on the weigh signal that was output when the detection device <NUM> detected the weight of the article P. Moreover, the control device <NUM> determines whether or not the calculated weight W of the article P is within an allowable weight range. What is meant by an expression that "the weight W of the article P being within an allowable weight range" is the weight of the article P is equal to or greater than an allowable minimum weight and equal to or less than an allowable maximum weight.

For example, a sorting device not shown in the drawings is disposed downstream of the weighing apparatus <NUM> is disposed. The sorting device sorts the article P based on the weight W of the article P calculated by the control device <NUM>. For example, in a case where the weight W of the article P is outside the allowable weight range, the sorting device removes the article P from the conveyance line of the article P.

The weighing apparatus <NUM> will be described in detail below.

It will be noted that in the following description expressions such as "front", "rear", "upper", "lower", "right", and "left" may be used when describing directions and positional relationships. Expressions such as "front", "rear", "upper", "lower", "right", and "left" follow the directions indicated by the arrows in the drawings unless otherwise specified.

The conveyance device <NUM> conveys the article P along a conveyance direction A1 (see <FIG> and <FIG>).

The conveyance device <NUM> includes a first conveyor <NUM> and a second conveyor <NUM> as well as a first drive unit 18a and a second drive unit 18b. The first drive unit 18a and the second drive unit 18b are, for example, motors.

In the conveyance device <NUM>, as shown in <FIG> and <FIG>, the first conveyor <NUM> and the second conveyor <NUM> are arranged in this order from upstream in the conveyance direction A1 of the article P.

As shown in <FIG>, among the first conveyor <NUM> and the second conveyor <NUM>, the first conveyor <NUM> is disposed upstream in the conveyance direction A1. The first conveyor <NUM> functions as an intake conveyor that introduces to the weighing apparatus <NUM> the article P conveyed from the process upstream of the weighing apparatus <NUM>. The first conveyor <NUM> conveys the article P in the conveyance direction A1 and hands over the article P to the second conveyor <NUM>.

The first conveyor <NUM> includes a first conveyor belt 12a (see <FIG>). The first conveyor belt 12a is, for example, a flat belt. The first conveyor belt 12a is entrained about a drive roller 122a and a follower roller 122b, and the first conveyor <NUM> conveys the article P on the first conveyor belt 12a in the conveyance direction A1 as a result of the first drive unit 18a driving the drive roller 122a.

As shown in <FIG>, among the first conveyor <NUM> and the second conveyor <NUM>, the second conveyor <NUM> is disposed downstream in the conveyance direction A1. The second conveyor <NUM> receives the article P conveyed by the first conveyor <NUM> and conveys it. The detection device <NUM> detects the weight of the article P as it is being conveyed by the second conveyor <NUM> and outputs the weigh signal. The second conveyor <NUM> conveys the article P in the conveyance direction A1 and hands over the article P to a process downstream of the weighing apparatus <NUM> (e.g., the sorting device not shown in the drawings).

The second conveyor <NUM> includes a second conveyor belt 14a (see <FIG>). The second conveyor belt 14a is, for example, a flat belt. The second conveyor belt 14a is entrained about rollers 144a and 144b, and the second conveyor <NUM> conveys the article P on the second conveyor belt 14a in the conveyance direction A1 as a result of the second drive unit 18b driving the roller (drive roller) 144a.

It will be noted that the first conveyor <NUM> and the second conveyor <NUM> have a variable conveyance speed. In other words, the motors of the first drive unit 18a and the second drive unit 18b have a variable rotational speed.

The detection device <NUM> will be described with further reference to <FIG> is a schematic configuration diagram of the second conveyor <NUM> of the conveyance device <NUM> and the detection device <NUM>.

As shown in <FIG> and <FIG>, the detection device <NUM> mainly has a sensor <NUM> and a load cell <NUM> serving as an example of a detection unit (a weight sensor).

The sensor <NUM> detects that the article P conveyed by the first conveyor <NUM> has reached the second conveyor <NUM>. The sensor <NUM> is, for example, a photoelectric sensor. However, the type of the sensor <NUM> is not limited to a photoelectric sensor and may be any type as long as it is a sensor that can detect the arrival of the article P at the second conveyor <NUM>.

The control device <NUM> detects the timing when the entire article P is on the second conveyor belt 14a based on the detection result of the sensor <NUM>, a conveyance speed V of the conveyance device <NUM>, and a length L1 of the article P in the conveyance direction A1. The control device <NUM> calculates the weight W of the article P based on a weigh signal output by the load cell <NUM> while the entire article P is on the second conveyor belt 14a.

The load cell <NUM> includes a spring element 28a that becomes deformed in proportion to force acting thereon and a strain gauge (not shown in the drawings) that is adhered to the spring element 28a, converts strain into an electrical signal (this signal is called a weigh signal), and outputs the electrical signal. In short, the load cell <NUM> sends a weigh signal corresponding to the force acting thereon. The load cell <NUM> is housed inside a case <NUM> disposed under the second conveyor <NUM> (see <FIG>).

Weight detection by the load cell <NUM> will be described. In describing weight detection by the load cell <NUM>, details about the structure of the second conveyor <NUM> of the conveyance device <NUM> will first be described.

The second conveyor <NUM> mainly has, in addition to the second conveyor belt 14a, a frame <NUM> as well as a drive roller 144a and a follower roller 144b (see <FIG>).

The frame <NUM> of the second conveyor <NUM> is supported by brackets <NUM> that extend upward from the case <NUM>. The case <NUM>, as shown in <FIG>, is secured to a frame <NUM> of the weighing apparatus <NUM>.

The drive roller 144a and the follower roller 144b, as shown in <FIG>, are provided on both ends of the frame <NUM>. The drive roller 144a and the follower roller 144b are supported by the frame <NUM> so as to be freely rotatable. The second conveyor belt 14a is entrained about the drive roller 144a and the follower roller 144b. The second drive unit 18b drives the drive roller 144a, whereby the second conveyor belt 14a rotates and the second conveyor <NUM> conveys the article P on the second conveyor belt 14a in the conveyance direction A1.

Because of this structure, the load cell <NUM> detects the weight of the second conveyor <NUM> (the force that the second conveyor <NUM> exerts on the load cell <NUM>), which serves as a conveyance unit, and outputs a weigh signal when the article P is not on the second conveyor belt 14a. It will be noted that, here, the weight of the second conveyor <NUM> is generally the total weight of the frame <NUM>, the drive roller 144a and the follower roller 144b, and the second conveyor belt 14a. Furthermore, when the second conveyor belt 14a is conveying the article P, the load cell <NUM> detects the weight of the second conveyor <NUM> and the weight of the article P on the second conveyor <NUM> and outputs a weigh signal.

The control device <NUM> controls the operations of each part of the weighing apparatus <NUM>. Furthermore, the control device <NUM> performs a process to calculate the weight W of the article P based on the weigh signal sent by the detection device <NUM>.

Furthermore, the control device <NUM> has the function of determining whether there is a defect in the weighing by the weighing apparatus <NUM>. Moreover, the control device <NUM> has the function of determining candidates for defect factors in the weighing apparatus <NUM> and outputting the determined candidates for defect factors in the weighing apparatus <NUM> in a case where there is a defect in the weighing by the weighing apparatus <NUM>.

Although this should not be construed as limiting the disposition of the control device <NUM>, the control device <NUM> may be installed in a body portion 100a of the weighing apparatus <NUM>. The body portion 100a of the weighing apparatus <NUM> is disposed on the side of the conveyance device <NUM> and is provided with an input device <NUM> and an output device <NUM> described later.

The control device <NUM> of this embodiment mainly includes a CPU, a memory including a ROM, a RAM, and/or an auxiliary storage device (e.g., flash memory), and various electronic circuits. The control device <NUM> controls the operations of each part of the weighing apparatus <NUM> and performs various processes as a result of the CPU reading and executing programs stored in the memory.

It will be noted that the configuration of the control device <NUM> described here is merely an example of the configuration of the control device <NUM>, and the same functions as those of the control device <NUM> of this embodiment may be realized by hardware such as a logic circuit or may be realized by a combination of hardware and software.

Furthermore, the control device <NUM> may be realized by one device or may be realized by plural devices. For example, the control device <NUM> may have a control device installed in the body portion 100a and a device installed in a place separate from the body portion 100a and communicably connected to the control device. The control device installed in the body portion 100a and the device outside the body portion 100a may work together to function as the control device <NUM> described here.

The control device <NUM> is electrically connected to the first drive unit 18a and the second drive unit 18b of the conveyance device <NUM> and the sensor <NUM> and the load cell <NUM> of the detection device <NUM>.

The control device <NUM> is also electrically connected to the input device <NUM> and the output device <NUM> provided in the body portion 100a (see <FIG>). The input device <NUM> receives various types of commands input by an operator of the weighing apparatus <NUM> and various types of information input by the operator. For example, the input device <NUM> is a touch panel display. The commands and information input to the input device <NUM> are sent to the control device <NUM>. The output device <NUM> is controlled by the control device <NUM> and outputs various types of information. For example, the output device <NUM> is a display that displays various types of information. In other words, in this embodiment, a touch panel display functions as the input device <NUM> and the output device <NUM>.

It will be noted that the input device and the output device are not limited to the device exemplified here. For example, the input device may be a device that receives commands and information sent from a mobile device (not shown in the drawings) operated by the operator or the like of the weighing apparatus <NUM> or a central control unit (not shown in the drawings) higher than the weighing apparatus <NUM>, or switches provided on the weighing apparatus <NUM>. Furthermore, the output device may be a device that outputs (sends) various types of information to a mobile device (not shown in the drawings) which the operator or the like of the weighing apparatus <NUM> has or to a central control unit (not shown in the drawings) higher than the weighing apparatus <NUM>.

The memory of the control device <NUM> includes a storage unit <NUM> that stores various types of information. Examples of the information stored in the storage unit <NUM> will be described later.

The CPU of the control device <NUM> functions as a control unit <NUM> and an acquisition unit <NUM> by reading and executing programs stored in the memory.

The acquisition unit <NUM> acquires various types of information input to the input device <NUM>. The various types of information acquired by the acquisition unit <NUM> are stored in the storage unit <NUM>.

The information acquired by the acquisition unit <NUM> includes, for example, a prescribed weight Wt of the article P conveyed by the conveyance device <NUM>. The prescribed weight Wt is, in other words, the weight that the article P should normally have (the target weight of the article P).

Furthermore, the information acquired by the acquisition unit <NUM> includes the length L1 of the article P conveyed by the second conveyor <NUM>. Here, the length L1 of the article P conveyed by the second conveyor <NUM> is the length of the article P in the conveyance direction A1 in a state in which the article P is conveyed by the second conveyor <NUM>.

Although the prescribed weight Wt of the article P and the length L1 of the article P are each input to the input device <NUM> in this embodiment, the configuration of the weighing apparatus <NUM> are not limited to this. For example, the information of the prescribed weight Wt of the article P and the length L1 of the article P may be stored for each type of the article P in the storage unit <NUM>, and the acquisition unit <NUM> may acquire an identifier that identifies the type of the article P and is input to the input device <NUM>. When the weighing apparatus <NUM> is configured in this way, the acquisition unit <NUM> can acquire the prescribed weight Wt of the article P and the length L <NUM> of the article P by referencing the storage unit <NUM>.

Furthermore, the information acquired by the acquisition unit <NUM> includes a conveyance speed V at which the article P is conveyed by the conveyance device <NUM> when the weighing apparatus <NUM> weighs the article P. It will be noted that the acquisition unit <NUM> may acquire, as the information of the conveyance speed V at which the article P is conveyed by the conveyance device <NUM>, information with which the conveyance speed V of the article P can be identified (e.g., the rotational speed of the motor of the second drive unit 18b).

When the weighing apparatus <NUM> weighs the article P, the control unit <NUM> controls the operations of the weighing apparatus <NUM> based on the commands input to the input device <NUM> and the information acquired by the acquisition unit <NUM>, such as the prescribed weight Wt of the article P, the length L1 of the article P, and the conveyance speed V at which the article P is conveyed by the conveyance device <NUM>.

For example, when an operation command is input to the input device <NUM>, the control unit <NUM> controls the operations of the first drive unit 18a and the second drive unit 18b so that the speed at which the article P is conveyed by the first conveyor <NUM> and the second conveyor <NUM> becomes the conveyance speed V acquired by the acquisition unit <NUM>.

Furthermore, for example, the control unit <NUM> calculates the weight W of a given article P based on the weigh signal output by the load cell <NUM> when that article P is being conveyed by the second conveyor <NUM>. Specifically, the control unit <NUM> detects the timing when the entire article P is on the second conveyor belt 14a based on the detection result of the sensor <NUM>, the conveyance speed V of the conveyance device <NUM>, and the length L1 of the article P. The control unit <NUM> calculates the weight W of the article P based on the weigh signal output by the load cell <NUM> while the entire article P is on the second conveyor belt 14a. The calculation of the weight W of the article P by the control unit <NUM> will be described later.

Furthermore, for example, the control unit <NUM> determines whether the weight of the article P it has calculated is within the allowable weight range. For example, the control unit <NUM> determines whether the weight W of the article P it has calculated is a value between the allowable minimum weight (prescribed weight Wt of article - α) and the allowable maximum weight (prescribed weight Wt of article + β) (α and β are set numerical values). The control unit <NUM> determines that the article P is an accepted article when the weight W of the article P it has calculated is within the allowable weight range and determines that the article P is a rejected article if the weight W of the article P it has calculated is outside the allowable weight range.

Furthermore, for example, the control unit <NUM> determines whether there is a defect in the weighing by the weighing apparatus <NUM>. Moreover, in a case where there is a defect in the weighing by the weighing apparatus <NUM>, the control unit <NUM> determines candidates for defect factors in the weighing apparatus <NUM> and outputs the candidates for defect factors in the weighing apparatus <NUM> it has determined.

The process by which the control unit <NUM> calculates the weight W of the article P will be described. First, a configuration of the control device <NUM> for the weight calculation process will be described with reference to <FIG> is a block diagram of a configuration of the control device <NUM> for the weight calculation process.

The control device <NUM> includes an amp <NUM>, an analog filter <NUM>, and an A/D converter <NUM>. Furthermore, the control unit <NUM> includes a signal processing unit <NUM> as a functional unit for the process for calculating the weight of the article P.

The amp <NUM> amplifies the weigh signal input from the load cell <NUM> and outputs the amplified signal to the analog filter <NUM>. The analog filter <NUM> removes unwanted highfrequency components from the amplified signal and outputs an analog signal. The A/D converter <NUM> converts the analog signal output from the analog filter <NUM> to a digital signal and outputs the digital signal to the signal processing unit <NUM>. The signal processing unit <NUM> filters the digital signal using a predetermined finite impulse response (FIR) filter (hereinafter simply called a filter). In short, the signal processing unit <NUM> uses the predetermined filter to filter the weigh signal that has been preprocessed by the amp <NUM>, the analog filter <NUM>, and the A/D converter <NUM> (hereinafter the weigh signal after being preprocessed will be called the weigh signal of the load cell <NUM>). The control unit <NUM> calculates the weight W of the article P based on the weigh signal of the load cell <NUM> filtered by the signal processing unit <NUM>.

It will be noted that, as mentioned above, in a case where the second conveyor belt 14a is conveying the article P, the load cell <NUM> detects the weight of the second conveyor <NUM> and the weight of the article P on the second conveyor <NUM> and outputs a weigh signal. For that reason, if, in a case where the second conveyor belt 14a is conveying the article P, the control unit <NUM> were to calculate the weight based on the weigh signal from the load cell <NUM>, the control unit <NUM> would calculate the total weight of the second conveyor <NUM> and the article P. Therefore, before the control unit <NUM> actually starts measuring the weight of the article P, the control unit <NUM> implements a process to derive a zero point based on the weigh signal output by the load cell <NUM> in a state in which the article P is not on the second conveyor belt 14a. In other words, before the control unit <NUM> actually starts measuring the weight of the article P, the control unit <NUM> implements in advance a process to calculate the weight of the second conveyor <NUM> that should be subtracted from the total weight of the second conveyor <NUM> and the article P on the second conveyor <NUM>.

It will be noted that the reason the signal processing unit <NUM> filters the weigh signal of the load cell <NUM> is the weigh signal of the load cell <NUM> includes noise caused by the natural vibration of the weighing apparatus <NUM> (vibration caused by shock when the article P is handed over to the second conveyor <NUM>) and rotational vibration of the motors (e.g., the motor used as the second drive unit 18b) and the rollers (e.g., the drive roller 144a and the follower roller 144b of the second conveyor <NUM>) used by the weighing apparatus <NUM>.

This will be described with reference to <FIG>. The weigh signal of the load cell <NUM> is a signal that includes a vibration component with a relatively large amplitude (noise) as indicated by the dashed line in <FIG>. The weight of the article P cannot be accurately calculated from the weigh signal that includes this vibration component. Therefore, the signal processing unit <NUM> uses the predetermined filter to filter (reduce the noise in) the weigh signal of the load cell <NUM> to extract a signal with little noise (generally, a signal representing just the force the article P exerts on the load cell <NUM>) such as indicated by the solid line in <FIG>.

The control unit <NUM> calculates the weight W of the article P based on the value of the difference between the weigh signal after being filtered by the signal processing unit <NUM> and the zero point. Specifically, the control unit <NUM> calculates the weight W of the article P based on the value of the difference between the weigh signal in the period in which the entire article P is on the second conveyor belt 14a (the weigh signal in the plateau portion of the solid line in <FIG>) and the weigh signal in the period in which the article P is not on the second conveyor belt 14a.

It will be noted that the frequency of the noise included in the weigh signal of the load cell <NUM> varies depending on various conditions.

For example, the frequency of the natural vibration of the weighing apparatus <NUM> is a relatively large frequency of about <NUM> to <NUM>. The frequency of the natural vibration varies depending on, for example, a length Lc1 of the second conveyor <NUM> in the conveyance direction A1 of the conveyance device <NUM>, a length Lc2 of the second conveyor <NUM> in the direction orthogonal to the conveyance direction A1 of the conveyance device <NUM> (see <FIG>), the prescribed weight Wt of the article P, and the length L1 of the article P in the conveyance direction A1.

Furthermore, the frequency of the rotational vibration of the motors and rollers is a frequency of about <NUM> to <NUM>. The frequency of the rotational vibration varies depending on, for example, the conveyance speed V of the article P (the conveyance speed of the second conveyor belt 14a), the length Lc1 of the second conveyor <NUM> in the conveyance direction A1 of the conveyance device <NUM>, the length Lc2 of the second conveyor <NUM> in the direction orthogonal to the conveyance direction A1 of the conveyance device <NUM>, the diameter of the drive roller 144a and the follower roller 144b, the number of teeth of the drive roller 144a, the number of teeth of the motor used as the second drive unit 18b, the number of teeth of a timing belt 144c of the second conveyor <NUM>, and the perimeter of the second conveyor belt 14a.

For example, the frequency of the vibration of the rollers is calculated by the conveyance speed [m/s] of the second conveyor belt 14a / the roller diameter [m] × π. For example, the frequency of the vibration of the motors is calculated by the frequency of the vibration of the rollers × the number of teeth of the rollers / the number of teeth of the motors. For example, the frequency of the vibration of the timing belt is calculated by the frequency of the vibration of the rollers × the number of teeth of the rollers / the number of teeth of the timing belt. For example, the frequency of the vibration of the second conveyor belt 14a (flat belt) is calculated by the conveyance speed [m/s] of the second conveyor belt 14a / the perimeter [m] of the second conveyor belt 14a.

Furthermore, sometimes the frequency of disturbances such as vibration in the floor of the factory is a relatively small frequency of <NUM> or less.

Because the frequency of noise included in the weigh signal of the load cell <NUM> can vary depending on various conditions in this way, the signal processing unit <NUM> is configured to variably set filters it uses for filtering. In other words, the control device <NUM> of the weighing apparatus <NUM> has plural filters with mutually different characteristics that the signal processing unit <NUM> uses to filter the weigh signal. The reason that the signal processing unit <NUM> variably sets the filters it uses for filtering is that there is not a single filter that can sufficiently reduce noise in all frequency bands among the filters used by the signal processing unit <NUM>.

It will be noted that the filters settable by the control device <NUM> include filters that can sufficiently reduce noise equal to or greater than predetermined frequencies. Although this is not intended to be limiting, the plural filters that the control device <NUM> has include, for example, a filter A that can sufficiently reduce noise equal to or greater than <NUM> from the weigh signal, a filter B that can sufficiently reduce noise equal to or greater than <NUM> from the weigh signal, a filter C that can sufficiently reduce noise equal to or greater than <NUM> from the weigh signal, and a filter D that can sufficiently reduce noise equal to or greater than <NUM> from the weigh signal. Here, "can sufficiently reduce noise equal to or greater than predetermined frequencies" refers, for example, to a filter that can reduce to a predetermined reduction ratio or less the amplitude of a signal equal to or greater than a predetermined frequency.

Furthermore, the filters settable by the signal processing unit <NUM> include a combination filter. Here, a combination filter is a filter created by combining a plurality of filters which each forms a base. By using a combination filter to perform filtering, noise with a frequency equal to or greater than a given frequency can be sufficiently (e.g., to <NUM>/<NUM>,<NUM> or less) reduced, and also in regard to frequencies smaller than that frequency, noise may be reduced to a relatively great extent the amplitude of a predetermined frequency.

The filters that the signal processing unit <NUM> uses when the weighing apparatus <NUM> weighs the article P are, for example, set (selected) by a technician so that noise included in the weigh signal is reduced while the technician performs a test operation. Alternatively, the filters that the signal processing unit <NUM> uses when the weighing apparatus <NUM> weighs the article P may be automatically set by the control unit <NUM> based, for example, on the results of the test operation.

The control device <NUM> acquires the weigh signal output by the load cell <NUM>, determines whether a defect in weighing is occurring in the weighing apparatus <NUM>, and determines and outputs candidates for defect factors. This series of processes is called a diagnostic process.

The diagnostic process performed by the control device <NUM> will be described.

The main processes in the diagnostic process include a process for determining whether a defect in weighing is occurring in the weighing apparatus <NUM> and a process for determining and outputting candidates for defect factors in a case where a defect in weighing is occurring. In the control device <NUM>, particularly the control unit <NUM> determines whether a defect in weighing is occurring in the weighing apparatus <NUM>. Specifically, the control unit <NUM> determines whether vibration that adversely affects or has the potential to adversely affect the weighing precision of the weighing apparatus <NUM> exists in the weighing apparatus <NUM>. Furthermore, in the control device <NUM>, in a case where the control unit <NUM> determines that there is a defect in the weighing by the weighing apparatus <NUM>, the control unit <NUM> determines candidates for defect factors. In a case where the control unit <NUM> determines that there is a defect in the weighing apparatus <NUM>, the control unit <NUM> outputs to the output device <NUM> the candidates for defect factors it has determined.

It will be noted that defect factors that the control unit <NUM> is able to determine as candidates include defects (failures, degradation over time, poor maintenance, etc.) in the weighing apparatus <NUM>. Failures in the weighing apparatus <NUM> include, for example, damage to the rollers 144a and 144b of the second conveyor <NUM>. Degradation of the weighing apparatus <NUM> over time includes, for example, wear of the second conveyor belt 14a. Poor maintenance of the weighing apparatus <NUM> includes, for example, improper adjustment of the tension in the second conveyor belt 14a and adhesion of dirt to the second conveyor belt 14a.

Furthermore, defect factors that the control unit <NUM> is able to determine as candidates may also include improper states of installation of the weighing apparatus <NUM>. Improper states of installation of the weighing apparatus <NUM> include, for example, a state in which one or more legs <NUM> (see <FIG>) of the frame <NUM> supporting the conveyance device <NUM> and the detection device <NUM> do not touch the surface where the weighing apparatus <NUM> is installed. In other words, improper states of installation of the weighing apparatus <NUM> include a state in which any of the legs <NUM> of the frame <NUM> is not supporting the conveyance device <NUM> and the detection device <NUM>.

Furthermore, defect factors that the control unit <NUM> is able to determine as candidates may include defects relating to the installation environment of the weighing apparatus <NUM>. Defects relating to the installation environment of the weighing apparatus <NUM> include, for example, vibration in the floor in the place where the weighing apparatus <NUM> is installed. Furthermore, defects relating to the installation environment of the weighing apparatus <NUM> include, for example, air currents (e.g., strong air currents generated by an air conditioning system, etc.) in the place where the weighing apparatus <NUM> is installed.

The control device <NUM> executes the diagnostic process when, for example, a command to diagnose the weighing apparatus <NUM> is input to the input device <NUM>. Furthermore, the control device <NUM> may execute the diagnostic process at predetermined timings in addition to, or instead of, the condition of a command to diagnose the weighing apparatus <NUM> being input to the input device <NUM>. For example, the control device <NUM> may execute the diagnostic process each time the weighing apparatus <NUM> is switched on. Furthermore, for example, the control device <NUM> may execute the diagnostic process each time a command for the weighing apparatus <NUM> to operate is input to the input device <NUM>.

A specific example of the diagnostic process executed by the control device <NUM> will be described with reference to the flowchart of <FIG>.

The control device <NUM> executes the diagnostic process based, for example, on the flowchart of <FIG> when a predetermined condition such as described above (e.g., the condition where a command to diagnose the weighing apparatus <NUM> is input) is met.

In step S <NUM>, the control device <NUM> acquires the weigh signal output by the load cell <NUM> in a predetermined amount of time (e.g., several tens of seconds) in a state in which there is no article P on the second conveyor <NUM> and the conveyance speed of the second conveyor <NUM> is zero (i.e., a state in which the second conveyor <NUM> is stopped). More specifically, the control device <NUM> acquires the weigh signal that is output by the load cell <NUM> in the predetermined amount of time in a state in which the conveyance speed of the second conveyor <NUM> is zero and there is article on the second conveyor <NUM> and then has been amplified by the amp <NUM> and processed by the analog filter <NUM> and the A/D converter <NUM> (to avoid redundant description, hereinafter this signal will sometimes be called the weigh signal of the load cell <NUM>). The weigh signal of the load cell <NUM> acquired by the control device <NUM> is stored in the storage unit <NUM>.

It will be noted that at this time the conveyance device <NUM> is not operating and the conveyance device <NUM> produces no vibration, so the load cell <NUM> detects, for example, vibration in the floor of the factory and disturbances such as air currents blowing against the second conveyor <NUM>. Particularly in a case where the installation state of the weighing apparatus <NUM> is improper such that any of the legs <NUM> of the frame <NUM> is hovering above the floor surface and the weighing apparatus <NUM> easily shakes, the load cell <NUM> tends to detect vibration, even relatively small disturbances such as relatively small vibrations in the floor of the factory.

Next, in step S2, the control device <NUM> operates the second conveyor <NUM> at a conveyance speed Va [m/s] in a state in which there is no article on the second conveyor <NUM> (without the article P being supplied to the second conveyor <NUM>). In other words, the control device <NUM> controls the operation of the second conveyor <NUM> so as to operate just the second conveyor belt 14a at the conveyance speed Va without the second conveyor <NUM> conveying an article. It will be noted that at this time the control device <NUM> may also simultaneously operate the first conveyor <NUM> at, for example, the conveyance speed Va.

Next, in step S3, the control device <NUM> acquires the weigh signal output by the load cell <NUM> in a predetermined amount of time (e.g., several tens of seconds) in a state in which there is no article on the second conveyor <NUM> and the second conveyor <NUM> is being operated at the conveyance speed Va. More specifically, the control device <NUM> acquires the weigh signal that is output by the load cell <NUM> in the predetermined amount of time in a state in which the second conveyor <NUM> is being operated at the conveyance speed Va without conveying the article P and then has been amplified by the amp <NUM> and processed by the analog filter <NUM> and the A/D converter <NUM> (to avoid redundant description, hereinafter this signal will sometimes be called the weigh signal of the load cell <NUM>). The weigh signal of the load cell <NUM> acquired by the control device <NUM> is stored in the storage unit <NUM>.

Next, in step S4, the control device <NUM> operates the second conveyor <NUM> at a conveyance speed Vb [m/s] in a state in which there is no article on the second conveyor <NUM> (without the article P being supplied to the second conveyor <NUM>). The conveyance speed Vb is a higher speed than the conveyance speed Va. For example, the conveyance speed Vb is twice the conveyance speed Va, although this is not intended to be limiting. In other words, the control device <NUM> controls the operation of the second conveyor <NUM> so as to just operate the second conveyor belt 14a at the conveyance speed Vb without the second conveyor <NUM> conveying an article. It will be noted that at this time the control device <NUM> may also simultaneously operate the first conveyor <NUM> at, for example, the conveyance speed Vb.

Next, in step S5, the control device <NUM> acquires the weigh signal output by the load cell <NUM> in a predetermined amount of time (e.g., several tens of seconds) in a state in which there is no article P on the second conveyor <NUM> and the second conveyor <NUM> is being operated at the conveyance speed Vb. More specifically, the control device <NUM> acquires the weigh signal that is output by the load cell <NUM> in the predetermined amount of time in a state in which the second conveyor <NUM> is being operated at the conveyance speed Vb without conveying the article P and then has been amplified by the amp <NUM> and processed by the analog filter <NUM> and the A/D converter <NUM> (to avoid redundant description, hereinafter this weigh signal will sometimes be called the weigh signal of the load cell <NUM>). The weigh signal of the load cell <NUM> acquired by the control device <NUM> is stored in the storage unit <NUM>.

It will be noted that in step S3 and step S5, ideally the load cell <NUM> does not detect anything because the second conveyor <NUM> is not conveying an article. However, in reality, the load cell <NUM> may detect disturbances such as vibration in the floor of the factory and air currents blowing against the second conveyor <NUM>, and also vibration produced by the conveyance device <NUM>.

Next, in step S6, the signal processing unit <NUM> of the control device <NUM> filters, with the plural filters, each of the weigh signals of the load cell <NUM> acquired in step S1, step S3, and step S5. For example, in step S6, the signal processing unit <NUM> filters, with the four filters A to D, each of the weigh signals of the load cell <NUM> (three weigh signals of the load cell <NUM>) acquired in step S1, step S3, and step S5. Although this is not intended to be limiting, for example, filter A is a filter that can sufficiently reduce noise of <NUM> or more, filter B is a filter that can sufficiently reduce noise of <NUM> or more, filter C is a filter that can sufficiently reduce noise of <NUM> or more, and filter D is a filter that can sufficiently reduce noise of <NUM> or more. Consequently, the weigh signals of the load cell <NUM> processed by filter A generally include only signals with a frequency smaller than <NUM>. The weigh signals of the load cell <NUM> processed by filter B generally include only signals with a frequency small than <NUM>. The weigh signals of the load cell <NUM> processed by filter C generally include only signals with a frequency smaller than <NUM>. The weigh signals of the load cell <NUM> processed by filter D generally include only signals with a frequency smaller than <NUM>. Here, the signal processing unit <NUM> processes, with the four filters A to D, each of the three weigh signals of the load cell <NUM>, so a total of twelve filtered signals are obtained. The filtered signals are stored in the storage unit <NUM>.

Next, in step S7, the control unit <NUM> generates statistical information in regard to each of the plural signals (in this embodiment, the signals in the cases where the conveyance speed is zero (while conveyance is stopped), the conveyance speed is Va, and the conveyance speed is Vb) that have been filtered by each of the plural filters A to D and are stored in the storage unit <NUM>. The statistical information here is, for example, at least one (one type) of the standard deviation, the dispersion, the difference between the maximum value and the minimum value, the maximum value, and the minimum value of each weigh signal after being filtered. Preferably, the statistical information includes at least one of the standard deviation, the dispersion, and the difference between the maximum value and the minimum value of each weigh signal after being filtered. It will be noted that the control unit <NUM> may generate just one type of statistical information, or may generate plural types of statistical information, for each of the plural weigh signals that have been filtered by each of the plural filters A to D and are stored in the storage unit <NUM>.

Next, in step S8, the control unit <NUM> compares, with standards for the statistical information that are stored for each of the conveyance speeds and for each of the filters in the storage unit <NUM>, the statistical information generated in regard to each of the plural signals filtered by each of the plural filters A to D.

The process of comparing the statistical information with the standards for the statistical information executed by the control unit <NUM> will be described by way of a specific example. Here, a case will be supposed where the control unit <NUM> generates the dispersion and the difference between the maximum value and the minimum value as the statistical information and compares the statistical information with the standards for the statistical information.

It will be noted that, as a premise for performing step S8, combinations of standard values for dispersions and standard values for differences between maximum values and minimum values are stored in the storage unit <NUM> in regard to combinations of the three types of conveyance speeds (the conveyance speed of zero, the conveyance speed Va, and the conveyance speed Vb) and the four filters (filter A to filter D).

It will be noted that these sets of information stored in the storage unit <NUM> may be, for example, dispersions and differences between maximum values and minimum values by conveyance speed and by filter calculated from simulations on a computer and/or theoretical calculations. Furthermore, these sets of information stored in the storage unit <NUM> may be, for example, dispersions and differences between maximum values and minimum values by conveyance speed and by filter obtained by the same method as steps S <NUM> to S7 using a tester of a weighing apparatus <NUM> known to have no defects (an apparatus separate from the weighing apparatus <NUM> to be diagnosed).

Alternatively, these sets of information stored in the storage unit <NUM> may, for example, be dispersions and differences between maximum values and minimum values by conveyance speed and by filter that is generated from signals obtained by filtering, with each of the plural filters A to D, the weigh signals output by the load cell <NUM> in regard to each of the plural conveyance speeds in a state in which there is no article P on the second conveyor <NUM> at the time of a test operation of the weighing apparatus <NUM> (the weighing apparatus <NUM> to be diagnosed itself and which is known to have no defects).

Furthermore, for example, dispersions and differences between maximum values and minimum values of the weigh signals obtained by the same method as steps S1 to S7 using the tester of the weighing apparatus <NUM>, for example, may be stored as defaults in the storage unit <NUM>. Additionally, dispersions and differences between maximum values and minimum values of the weigh signals obtained by the same method as steps S1 to S7 at the time of a test operation of the weighing apparatus <NUM> to be diagnosed may be stored in the storage unit <NUM> after the test operation.

In step S8, the control unit <NUM> compares the dispersions and the differences between the maximum values and the minimum values generated from the signals filtered by each filter in regard to each conveyance speed with the combinations of the standard values for the dispersions and the standard values for the differences between the maximum values and the minimum values stored in the storage unit <NUM> and associated with the corresponding conveyance speeds and the corresponding filters. Then, the control unit <NUM> determines, in a case where the dispersion generated from the signals filtered by each filter in regard to each conveyance speed is greater by a predetermined value or more than the standard value for the dispersion or in a case where the difference between the maximum value and the minimum value generated from the signals filtered by each filter in regard to each conveyance speed is greater by a predetermined value or more than the standard value for the difference between the maximum value and the minimum value, that there is an abnormality in this set of statistical information (the set of statistical information deviates from the normal value). It will be noted that the control unit <NUM> may also determine, in a case where the dispersion generated from the signals filtered by each filter in regard to each conveyance speed is greater by the predetermined value or more than the standard value for the dispersion and the difference between the maximum value and the minimum value generated from the signals filtered by each filter in regard to each conveyance speed is greater by the predetermined value or more than the standard value for the difference between the maximum value and the minimum value, that there is an abnormality in this set of statistical information.

It will be noted that, for example, in a case where the statistical information is the maximum value, the control unit <NUM> may determine, in a case where the maximum value is greater by a predetermined value or more than the standard value, that there is an abnormality in the set of statistical information. Furthermore, for example, in a case where the statistical information is the minimum value, the control unit <NUM> may determine, in a case where the minimum value is smaller by a predetermined value or more than the standard value, that there is an abnormality in the set of statistical information.

In step S8, the control unit <NUM> executes this kind of comparison of the statistical information with the standards for the statistical information in regard to each of the combinations of the three types of conveyance speeds, the conveyance speed of zero, the conveyance speed Va, and the conveyance speed Vb, and the four filters, filter A to filter D. In this embodiment, the control unit <NUM> executes the comparison of the statistical information with the standards for the statistical information in regard to twelve combinations of the conveyance speeds and the filter types.

Next, in step S9, the control unit <NUM> determines whether there is a set of statistical information in which there is an abnormality in the plural sets of statistical information generated for each of the combinations of the conveyance speeds and the filter types (in this embodiment, in twelve sets of statistical information). If there is a set of statistical information in which there is an abnormality, the diagnostic process proceeds to step S <NUM>, and if there is not a set of statistical information in which there is an abnormality, the diagnostic process proceeds to step S20.

In step S10, the control unit <NUM> determines candidates for defect factors based on the plural sets of statistical information generated for each of the combinations of the conveyance speeds and the filter types. Specific examples will be described with reference to <FIG>.

For example, as shown in <FIG>, in a case where the control unit <NUM> determines that the statistical information generated from the signals obtained by filtering, with each of filter B, filter C, and filter D, the weigh signal of the load cell <NUM> at least in a case where the conveyance speed is zero (a case where the second conveyor <NUM> is stopped) are abnormal, the control unit <NUM> determines that a defect relating to the installation environment of the weighing apparatus <NUM> and an improper installation state of the weighing apparatus <NUM> are candidates for defect factors in the weighing apparatus <NUM>.

For example, as shown in <FIG>, let it be assumed that the control unit <NUM> determines that the sets of statistical information generated from the signals obtained by filtering, with each of filter B, filter C, and filter D, the weigh signal of the load cell <NUM> in a case where the conveyance speed is zero are normal. In contrast, let it be assumed that the control unit <NUM> determines that the sets of statistical information generated from the signals obtained by filtering, with filter A, the weigh signals of the load cell <NUM> in a case where the conveyance speeds are Va and Vb are abnormal. In this case, the control unit <NUM> determines that degradation over time or poor maintenance of the second conveyor belt 14a are candidates for defect factors in the weighing apparatus <NUM>. The reason the control unit <NUM> makes this determination is that it is inferred that there are no problems in the installation environment of the weighing apparatus <NUM> and the installation state of the weighing apparatus <NUM> because there are no abnormalities in the sets of statistical information in the case where the conveyance speed is zero, and vibration having a relatively low frequency tends to occur in a case where there is a defect in the second conveyor belt 14a (a flat belt).

For example, as shown in <FIG>, let it be assumed that the control unit <NUM> determines that the sets of statistical information generated from the signals obtained by filtering, with filter B, filter C, and filter D, the weigh signal of the load cell <NUM> in a case where the conveyance speed is zero are normal. Moreover, let it be assumed that the control unit <NUM> determines that the set of statistical information generated from the signal obtained by filtering, with filter D, the weigh signal of the load cell <NUM> in a case where the conveyance speed is Vb is abnormal. Furthermore, let it be assumed that the control unit <NUM> determines that the sets of statistical information generated from the signals obtained by filtering, with filter C and filter D, the weigh signal of the load cell <NUM> when the conveyance speed is Va are abnormal. In this case, the control unit <NUM> determines that damage to the rollers 144a and 144b or damage to the drive second drive unit 18b are candidates for defect factors in the weighing apparatus <NUM>. The reason the control unit <NUM> makes this determination is that it is inferred that there are no problems in the installation environment of the weighing apparatus <NUM> or the installation state of the weighing apparatus <NUM> because there are no abnormalities in the sets of statistical information in a case where the conveyance speed is zero, and vibrations having a relatively low frequency tend to occur in a case where there is a defect in the rollers 144a and 144b or the second drive unit 18b.

It will be noted that the motor serving as the second drive unit 18b may have a function of detecting damage to itself and outputting the detection result to the control device <NUM>. In this case, if there is a problem in the second drive unit 18b, the abnormality in the second drive unit 18b is reported to the control device <NUM>. For that reason, in this case, even if results such as those in <FIG> are obtained, the control unit <NUM> may exclude damage to the second drive unit 18b from the candidates for defect factors in the weighing apparatus <NUM> if there is no report of an abnormality from the second drive unit 18b.

When the determination of defect factors ends in step S10, the control unit <NUM> outputs to the output device <NUM> the candidates for defect factors in the weighing apparatus <NUM> it determined in step S10 (step S11). For example, the control unit <NUM> displays, on a display serving as the output device <NUM>, the candidates for defect factors in the weighing apparatus <NUM> it determined in step S10. In another example, the control unit <NUM> may send, to a mobile device or the like operated by the operator or the like of the weighing apparatus <NUM>, information about the candidates for defect factors in the weighing apparatus <NUM> it determined in step S10.

In step S20, the control unit <NUM> determines that there are no defects in the weighing apparatus <NUM>. Then, in step S21, the control unit <NUM> outputs to the output device <NUM> an indication that there are no defects in the weighing apparatus <NUM>.

It will be noted that the diagnostic process described above is merely an example and can be appropriately changed.

For example, the order of step S1 to step S5 can be appropriately changed. For example, step S2 and step S3 may be executed first, followed by step S4 and step S5 and finally step S1. Alternatively, step S4 and step S5 may be executed first, followed by step S2 and step S3 and finally step S1.

Furthermore, in the flowchart of <FIG>, the filtering of the weigh signals of the load cell <NUM> acquired in steps S1, S3, and S5 is performed in one go in step S6, but the filtering is not limited to this. For example, the signal processing unit <NUM> may perform filtering right after the weigh signal of the load cell <NUM> is acquired in each of steps S1, S3, and S5. Furthermore, the process of acquiring the sets of statistical information of step S7 may also be performed right after the weigh signals of the load cell <NUM> are each filtered.

Furthermore, in the above embodiment, the determination result indicating that there are no defects is output to the output device <NUM> in step S21 even in a case where there are no defects in the weighing apparatus <NUM>, but the diagnostic process is not limited to this aspect. For example, the processes of step S20 and step S21 may also be omitted.

Furthermore, in the flowchart of <FIG>, the weighing apparatus <NUM> only changes the conveyance speed in three stages, zero, Va, and Vb, but the weighing apparatus <NUM> is not limited to this and may also change the conveyance speed in four or more stages. By changing the conveyance speed in multiple stages, it becomes easier to more accurately determine candidates for defect factors from numerous defect factors.

Furthermore, in the above description, the weighing apparatus <NUM> uses four types of filters in the diagnostic process, but the number of filter types is not limited to this, and the weighing apparatus <NUM> may also use two types, three types, or five or more types of filters to filter the weigh signals of the load cell <NUM>.

Moreover, in the flowchart described with reference to <FIG>, the control device <NUM> filters, with the plural filters A to D, one weigh signal when the conveyance speed is zero, filters, with the plural filters A to D, one weigh signal when the conveyance speed is Va, and filters, with the plural filters A to D, one weigh signal when the conveyance speed is Vb. However, the control device <NUM> is not limited to this and may, as shown in <FIG>, directly filter, with any of the plural filters A to D, the weigh signals of the load cell <NUM> acquired when the conveyance speed is zero, Va, and Vb. In other words, the control device <NUM> may simultaneously perform step S1 and step S6 in <FIG>as step S1a, simultaneously perform step S2, step S3, and step S6 in <FIG> as step S2a, and simultaneously perform step S4, step S5, and step S6 in <FIG> as step S3a. It will be noted that processes from step S7 on in <FIG> are the same as those in <FIG>, so description thereof will be omitted.

(<NUM>-<NUM>)
The weighing apparatus <NUM> of the above embodiment measures the weight of the article P while conveying the article P. The weighing apparatus <NUM> includes the second conveyor <NUM> serving as an example of a conveyance unit that conveys the article P, the load cell <NUM> serving as an example of a detection unit, and the control unit <NUM>. The second conveyor <NUM> has a variable conveyance speed. The load cell <NUM> detects the weight of the second conveyor <NUM> or, in a case where the second conveyor <NUM> is conveying the article P, the weight of the second conveyor <NUM> and the weight of the article P on the second conveyor <NUM> and outputs a weigh signal. The control unit <NUM> generates statistical information from the weigh signals output by the load cell <NUM> in a state in which there is no article on the second conveyor <NUM> in regard to each of the plural conveyance speeds. The control unit <NUM> determines and outputs candidates for defect factors based on the statistical information for each of the conveyance speeds.

In this weighing apparatus <NUM>, as candidates for defect factors are determined based on the statistical information obtained in regard to the plural conveyance speeds Va and Vb, candidates for defect factors can be accurately inferred in a case where a defect is occurring in the weighing. For that reason, a worker maintaining the weighing apparatus <NUM> can eliminate the defect in a short amount of time.

(<NUM>-<NUM>)
In the weighing apparatus <NUM> of the above embodiment, the statistical information generated by the control unit <NUM> include statistical information generated from the weigh signal output by the load cell <NUM> in a state in which there is no article on the second conveyor <NUM> in a case where the conveyance speed is zero.

In this weighing apparatus <NUM>, candidates for defect factors in the weighing apparatus <NUM> are determined based on the statistical information obtained in a case where the conveyance speed is zero, that is, while the second conveyor <NUM> is stopped. Therefore, candidates for defect factors can be inferred particularly accurately in a case where a defect is occurring in the weighing. For that reason, a worker maintaining the weighing apparatus <NUM> can eliminate the defect in a short amount of time.

(<NUM>-<NUM>)
In the weighing apparatus <NUM> of the above embodiment, the defect factors include at least one of defect factors relating to the installation state of the weighing apparatus <NUM> and defect factors relating to the installation environment of the weighing apparatus <NUM>.

In this weighing apparatus <NUM>, the potential for not only defects in constituent parts of the weighing apparatus <NUM> but also other types of defects can be detected, and the amount of time that a worker maintaining the weighing apparatus <NUM> needs to identify the cause of a defect can be shortened.

(<NUM>-<NUM>)
In the weighing apparatus <NUM> of the above embodiment, the control unit <NUM> has plural filters with mutually different characteristics which are configured to be used to filter the weigh signals. The control unit <NUM> generates the statistical information from signals obtained by filtering, with each of the plural filters, the weigh signals output by the load cell <NUM> in a state in which there is no article on the second conveyor <NUM> in regard to each of the plural conveyance speeds (in this embodiment, the conveyance speed of zero, the conveyance speed Va, and the conveyance speed Vb). For example, in the above embodiment, the control unit <NUM> generates the statistical information from signals obtained by filtering, with each of the four types of filters A to D, the weigh signals output by the load cell <NUM> in a state in which there is no article on the second conveyor <NUM> in regard to each of the plural conveyance speeds. The control unit <NUM> determines and outputs the candidates for defect factors based on the statistical information for each of the conveyance speeds and for each of the filters.

In this weighing apparatus <NUM>, as candidates for defect factors are determined using the statistical information obtained from signals obtained by processing signals with different filters, candidates for defect factors can be accurately inferred in a case where a defect is occurring in the weighing. For that reason, a worker maintaining the weighing apparatus <NUM> can eliminate the defect in a short amount of time.

(<NUM>-<NUM>)
The weighing apparatus <NUM> of the above embodiment has the storage unit <NUM>. In the storage unit <NUM>, standards for the statistical information are stored for each of the conveyance speeds and for each of the filters. The control unit <NUM> determines and outputs the candidates for defect factors based on results of a comparison of the generated statistical information for each of the conveyance speeds and for each of the filters with the standards for the corresponding conveyance speeds and filters stored in the storage unit <NUM>.

In this weighing apparatus <NUM>, candidates for defect factors can be accurately inferred by comparing the generated statistical information with the standards.

(<NUM>-<NUM>)
In the weighing apparatus <NUM> of the above embodiment, the statistical information generated from signals obtained by filtering, with each of the plural filters, the weigh signal output by the load cell <NUM> in a state in which there is no article on the second conveyor <NUM> in regard to each of the plural conveyance speeds at the time of a test operation of the weighing apparatus <NUM> may be stored as the standards in the storage unit <NUM>.

In this weighing apparatus <NUM>, the statistical information obtained at the time of a test operation of the weighing apparatus <NUM> are used as the standards, so candidates for defect factors can be inferred based on characteristics unique to each weighing apparatus <NUM>.

(<NUM>-<NUM>)
In the weighing apparatus <NUM> of the above embodiment, the statistical information includes at least one of standard deviation, dispersion, the difference between a maximum value and a minimum value, a maximum value, and a minimum value.

In the above embodiment, the statistical information generated from the weigh signals output by the load cell <NUM> in a state in which the conveyance speed is zero (i.e., the second conveyor <NUM> is stopped) and there is no article on the second conveyor <NUM> are utilized in the diagnostic process, but the statistical information utilized in the diagnostic process are not limited to this.

In other words, the statistical information utilized in the diagnostic process may also be just the statistical information generated from the weigh signals output by the load cell <NUM> in a state in which the second conveyor <NUM> is operating and there is no article on the second conveyor <NUM>.

It will be noted that in a case where a defect is occurring in the weighing due to a defect relating to the installation environment of the weighing apparatus <NUM> and an improper installation state of the weighing apparatus <NUM>, there will not be a large difference in the vibration component affecting weighing even when the conveyance speed is changed. For that reason, by observing such phenomena, it can be determined that defects relating to the installation environment of the weighing apparatus <NUM> and an improper installation state of the weighing apparatus <NUM> are candidates for defect factors even without using the statistical information generated from the weigh signals output by the load cell <NUM> in a state in which the conveyance speed is zero and there is no article on the second conveyor <NUM>.

In the above embodiment, at the time of the diagnostic process, the conveyance speed of the second conveyor <NUM> is varied between the conveyance speed Va and the conveyance speed Vb and the statistical information generated from the weigh signals output by the load cell <NUM> in a state in which there is no article on the second conveyor <NUM> in regard to each of the conveyance speeds Va and Vb are used in the diagnostic process. However, the statistical information used in the diagnostic process are not limited to this, and in the diagnostic process just the statistical information generated from the weigh signals of the load cell <NUM> when the conveyance speed of the second conveyor <NUM> is zero and the statistical information generated from the weigh signals of the load cell <NUM> when the conveyance speed of the second conveyor <NUM> is the conveyance speed Va may also be used. However, in order to accurately determine candidates for defect factors, it is preferred to vary the conveyance speed at the time of operation of the second conveyor <NUM> in two stages or more and use the statistical information generated from the weigh signals output by the load cell <NUM> in a state in which there is no article on the second conveyor <NUM> in regard to each of the conveyance speeds.

In the above embodiment, an example is described where plural filters are utilized at the time of the diagnostic process, but the number of filters is not limited to this, and just one filter may be used in the diagnostic process. Even in a case such as this, the statistical information can be generated from the weigh signals output by the load cell <NUM> in a state in which there is no article on the second conveyor <NUM> in regard to each of the plural conveyance speeds, and candidates for defect factors can be determined based on the statistical information for each of the conveyance speeds.

For example, the frequency of vibration of the rollers 144a and 144b of the second conveyor <NUM> and the frequency of vibration of the second conveyor belt 14a vary depending on the conveyance speed of the second conveyor <NUM>. For that reason, in a case where a defect is occurring in the rollers 144a and 144b and/or the second conveyor belt 14a of the second conveyor <NUM>, even in a case where just one filter is used, depending on the conveyance speed of the second conveyor <NUM>, vibration is strongly detected in the signals after being filtered or vibration is seldom detected in the signals after being filtered. By observing such phenomena, candidates for defect factors can be determined even using just one type of filter.

Furthermore, the control unit <NUM> need not utilize filters in the diagnostic process. For example, the control unit <NUM> may implement a frequency analysis on the weigh signals output by the load cell <NUM> in a state in which no article is on the second conveyor <NUM> in regard to each of the plural conveyance speeds, generate the statistical information for each frequency band, and determine and output candidates for defect factors based on the statistical information it has generated.

The weighing apparatus <NUM> has the conveyance device <NUM>, the detection device <NUM>, and the control device <NUM>, but the weighing apparatus <NUM> may also be an apparatus having configurations other than these. For example, in the above embodiment, an example is described where a sorting device separate from the weighing apparatus <NUM> is disposed downstream of the weighing apparatus <NUM>, but the weighing apparatus <NUM> may also have a sorting mechanism that sorts the articles P based on the weighing results of the articles P.

In the above embodiment, a FIR filter was described as an example of the filter, but the filter type is not limited to a FIR filter and may be another type of filter capable of filtering the weigh signals.

In the above embodiment, the weighing apparatus <NUM> including the load cell <NUM> having a strain gauge as a detection unit (weight sensor) is described. However, the type of detection unit that the weighing apparatus has is not limited to a load cell using a strain gauge. For example, the load cell <NUM> may also be a hydraulic load cell or a pneumatic load cell. Furthermore, the detection unit may also be a weigh sensor other than a load cell type, such as a tuning fork vibration type of weight sensor, an electromagnetic balance type of weight sensor, or a capacitive type of weight sensor.

The present invention can be widely applied to weighing apparatus that weigh an article as it is being conveyed, and is therefore useful.

Claim 1:
A weighing apparatus (<NUM>) configured to measure the weight of an article while conveying the article, the weighing apparatus comprising:
a conveyance unit (<NUM>) configured to convey the article and having a variable conveyance speed;
a detection unit (<NUM>) configured to detect a weight of the conveyance unit or, in a case where the conveyance unit is conveying the article, a weight of the conveyance unit and a weight of the article on the conveyance unit, the detection unit configured to output a weigh signal; and characterised by:
a control unit (<NUM>) configured to generate statistical information from the weigh signals output by the detection unit in a state in which there is no article on the conveyance unit in regard to each of a plurality of the conveyance speeds, the control unit configured to determine and output candidates for defect factors based on the statistical information for each of the conveyance speeds.