Patent Description:
There is known a gas compressor that generates compressed gas used as a power source of a production line or an air source for a machine tool, a press machine, an air blower, or the like. The gas compressor includes a compressor body that compresses the gas in a compression chamber formed by a casing, and is configured to discharge the compressed gas from a discharge port to a gas tank via a discharge pipe. In addition, there is a package-type gas compressor in which a compressor body, a motor that drives the compressor body, a control circuit, an operation panel, and the like are integrated into a package to save space. In such a gas compressor or other fluid machines having the same configuration, in order to extend the product life, it is necessary to detect wear of the fluid machine body and to then perform maintenance before occurrence of damage.

There is Patent Document <NUM> as the background art of the present invention. In Patent Document <NUM>, cooling fans <NUM> and <NUM> that are driven together with a compressor body <NUM> by a motor <NUM>, an unload mechanism <NUM> that switches the compressor body <NUM> between a normal operation and a no-load operation, and a temperature sensor <NUM> that measures the ambient temperature of the compressor body <NUM> as an in-box temperature T1 are provided inside a soundproof box <NUM>. When the in-box temperature T1 exceeds an upper limit temperature H, the compressor body <NUM> is switched to the no-load operation by a CPU <NUM> or the like, and when the in-box temperature T1 is a return temperature L or less, the compressor body <NUM> returns to the normal operation. Accordingly, during no-load operation, control is performed such that the temperature inside the soundproof box <NUM> can be decreased by the cooling fans <NUM> and <NUM> while the heat generation amount of the compressor body <NUM> is suppressed, and a malfunction of a thermal relay <NUM> and the like caused by high temperature can be prevented. Patent document <NUM> discloses a compressor composed of a fixed scroll, a turning scroll, a drive shaft, and is controlled by a control unit. Patent document <NUM> discloses a method which involves turning a delivery of a medium to a system on and off depending on a temperature signal and switching a feed off if a temperature signal exceeds a temperature limit.

In a compressor described in Patent Document <NUM>, the temperature determined to be abnormal in an operating state where the heat generation amount is large is set to the upper limit temperature H, and for example, even when abnormal heat generation occurs during operation in a state where the temperature of the compressor is not increased, such as during operation in a low pressure state or when the rotation speed is controlled at high speed by an inverter, abnormality cannot be detected.

The above cited problems are solved in accordance with the appended claims. In particular, there is provided a fluid machine according to the subject-matter of claim <NUM>.

According to the present invention, even during operation in a state where the temperature is not increased, abnormal heat generation can be detected.

In the present embodiment, as a compression method of a compressor body, a scroll compressor in which a compression chamber is formed between a fixed scroll and an orbiting scroll and which takes orbiting motion to compress air will be described as an example.

<FIG> is a cross-sectional view of the compressor body in the present embodiment. In the compressor illustrated in <FIG>, power is transmitted from a motor including a stator <NUM> and a rotor <NUM> to the compressor including an orbiting scroll <NUM> and a fixed scroll <NUM> via a shaft <NUM>. The rotation speed of the motor changes at the frequency of voltage output from an inverter <NUM>. The power from the shaft <NUM> is transmitted to a cooling fan <NUM>, and the cooling fan <NUM> delivers generated cooling air to cooling fins of the orbiting scroll <NUM> and the fixed scroll <NUM> via a duct (not illustrated) to cool the compressor. A temperature sensor <NUM> is disposed at a distal end of the cooling fin of the fixed scroll <NUM>, and uses a measured temperature to detect abnormality of the compressor and to issue a notification when the abnormality is detected.

Temperature information measured by the temperature sensor <NUM> or a temperature sensor <NUM> provided in the compressor body, or information such as a current value measured by an ammeter provided in the inverter <NUM> is input to a control unit <NUM>. The frequency of voltage output from the inverter <NUM> is controlled by the control unit.

<FIG> is schematic graphs of a relationship between the frequency of voltage output from the inverter <NUM> and temperature measured by the temperature sensor <NUM>, and a relationship between pressure discharged from the compressor and the temperature measured by the temperature sensor <NUM> in the first embodiment. <FIG> shows a relationship between a frequency f and a temperature T, and <FIG> shows a relationship between a pressure P and the temperature T.

As shown in <FIG>, the frequency f changes between a lowest frequency <NUM> and a highest frequency <NUM> such that pressure is constant when the air amount of compressed air to be discharged is changed. When the frequency f decreases, the rotation speed of the cooling fan rotating on the shaft <NUM> similar to the compressor decreases, so that the air amount of cooling air decreases and accordingly, the temperature T of the compressor rises. The relationship changes as indicated by <NUM>, and when the frequency f decreases, the temperature T of the compressor rises.

In addition, the relationship between the pressure P and the temperature T is as shown in <FIG>, and the pressure changes from <NUM> MPa to a highest pressure <NUM>. When the pressure P increases, the temperature of the fixed scroll <NUM> rises with a rise in temperature of the compressed air, and the temperature T also rises. A product in the related art controls a threshold value with respect to the frequency f and the pressure P to a fixed value as indicated by <NUM>. For this reason, there is a possibility that even when the frequency f increases or the pressure decreases, the product in the related art cannot detect abnormality until the temperature rises to <NUM>, and there is a delay in dealing with abnormality occurring in the compressor. For this reason, the threshold value is made to depend on the frequency and the pressure as indicated by <NUM> and <NUM>, and control is performed such that abnormality can be detected early.

A method for determining a threshold value T(f) corresponding to the frequency f is represented by equation (<NUM>) where the threshold value is a value obtained by adding a constant value to a normal temperature To(f), equation (<NUM>) where the threshold value is expressed as a function of the frequency f using arbitrary coefficients k and β, or the like, and more generally, may be represented by equation (<NUM>). <MAT> <MAT> <MAT>.

A method for determining a threshold value T(P) corresponding to the pressure P is represented by equation (<NUM>) where the threshold value is a value obtained by adding a constant value to a normal temperature To(P), equation (<NUM>) where the threshold value is expressed as a function of the pressure P using arbitrary coefficients m and β, or the like, and more generally, may be represented by equation (<NUM>). <MAT> <MAT> <MAT>.

In <FIG>, the methods for determining the threshold values shown in <FIG> are simplified. In methods for determining threshold values shown in <FIG>, the frequency and the pressure each are divided into ranges, and the threshold values each are changed to constant threshold values in a stepwise manner for each range as indicated by <NUM> and <NUM>. Threshold values <NUM> and <NUM> are larger than the values of normal temperatures <NUM> and <NUM>. When the range is divided, the size of the range may be divided according to a portion even in a certain range. In addition, the number of divisions is also arbitrary.

In <FIG>, the threshold values of the temperature are mapped with respect to the pressure and the frequency. When the threshold value is actually determined, the threshold value is required to be determined based on both the pressure and the frequency, so that the threshold value within the range of each pressure and frequency is used as a value for determining temperature abnormality. When the frequency or the pressure changes, the threshold value is accordingly changed. For example, when an operation is performed at a frequency of <NUM> and a pressure of <NUM> MPa, the threshold value is <NUM>. When the frequency does not change from this point and the pressure rises to <NUM> MPa, the threshold value is changed to <NUM> and a determination is performed. Here, the unit Kelvin (K) is a measured temperature which is relative to the ambient temperature (air temperature) of the compressor, and in the case of <NUM>, the measured temperature is <NUM> higher than the ambient temperature.

<FIG> shows a relationship between a temperature of the compressor <NUM> when temperature is measured in a portion of <NUM> in <FIG>, a discharge temperature <NUM>, and an operating state of the compressor <NUM>. In a period from t1 to t2 in <FIG> for which the compressor is stopped, since gas is not compressed, the discharge temperature <NUM> decreases, but the temperature of the compressor <NUM> rises due to heat transfer from the highest temperature location inside the compressor since the cooling fan <NUM> is stopped. When an operation starts at t2, the discharge temperature rises again and the temperature of the compressor is cooled by the cooling fan, so that the temperature decreases. However, it takes up to t3 for the temperature to decrease until the operation is continuously performed. Namely, it is normal that the temperature in a period from t1 to t3 is higher than that in a steady state, and when a determination on temperature abnormality is performed in the range, the temperature may exceed the threshold value. For this reason, in the present embodiment, a determination is not performed in the range from t1 to t3.

<FIG> shows a graph of time change of a relationship between a temperature rise value <NUM> of the compressor and a threshold value <NUM> when a pressure <NUM> and a frequency <NUM> change. The amount of a change in threshold value is adjusted depending on whether the threshold value is increased or decreased, so that the possibility of erroneous detection can be reduced.

In this control, when the threshold value is increased as at time t1, since the threshold value is a threshold value of <NUM> at time t1 as indicated by a threshold value increase <NUM>, the threshold value is immediately increased to <NUM> K. On the other hand, when the threshold value is decreased as at time t2, control is performed such that as indicated by threshold value decrease <NUM>, the threshold value is not immediately decreased to a threshold value of <NUM> at time t2, but the threshold value is decreased over time in a stepwise manner, linearly, or non-linearly. The reason is that since it takes time for the temperature of the compressor to decrease, when the threshold value is immediately decreased, there is a possibility of detecting abnormality of the compressor even though there is no abnormality.

<FIG> is a flowchart to determine temperature abnormality of the compressor. After the frequency and the pressure are acquired, at step <NUM>, a provisional threshold value is acquired from the threshold value map shown in <FIG>. When the provisional threshold value is larger than a current threshold value at step <NUM>, a temperature abnormality determination <NUM> is performed with the provisional threshold value set to a new threshold value <NUM>. When the provisional threshold value is smaller than the threshold value at step <NUM>, a determination <NUM> is performed while the threshold value is decreased by <NUM> at certain time intervals up to the provisional threshold value as at step <NUM>. If a pressure rise or a frequency decrease occurs in the middle of step <NUM> and the provisional threshold value is larger than the threshold value in the determination at step <NUM>, the process of decreasing the threshold value by <NUM> at the certain time intervals up to the provisional threshold value is stopped, and a determination on temperature abnormality is performed with the provisional threshold value set to the threshold value.

Since the threshold value is not set to a fixed value and is changed according to the pressure and the frequency as described above, the accuracy of detecting a temperature rise caused by wear of the compressor is further improved, and maintenance can be performed before damage occurs due to the wear of the compressor.

In <FIG>, the method for using the threshold value map to acquire the threshold value is adopted; however, when a method for acquiring the threshold value by calculation is adopted, the provisional threshold value is calculated at step <NUM> and a third step of step <NUM> of acquiring the provisional threshold value, so that the same control can be performed.

Incidentally, in the present embodiment, the inverter machine has been described as a target; however, a compressor which is subjected to constant speed control without using the inverter may be used, and in that case, only the threshold value is changed for a change in pressure, so that similarly, a determination can be performed with high detection accuracy.

In addition, in the present embodiment, an example where the threshold value is changed according to the pressure and the frequency has been described; however, the threshold value in the claimed invention can be changed at least according only to the pressure.

<FIG> shows the discharge temperature of the compressor when pressure changes, the discharge temperature being measured in a discharge port for the compressed gas by the temperature sensor <NUM> in <FIG>. The discharge temperature depends on the pressure, and when the pressure increases, the discharge temperature also increases. A method for determining a threshold value T'(P) of <NUM> corresponding to the pressure P is represented by equation (<NUM>) where the threshold value is a value obtained by adding a constant value to a normal temperature To'(P) of <NUM>, equation (<NUM>) where the threshold value is expressed as a function of the pressure P using the arbitrary coefficients m and β, or the like, and more generally, may be represented by equation (<NUM>). <MAT> <MAT> <MAT>.

In <FIG>, the method for determining the threshold value shown in <FIG> is simplified similar to <FIG>. In the method for determining the threshold value shown in <FIG>, the pressure is divided into ranges, and the threshold value is set to a constant threshold value for each range as indicated by <NUM>. A threshold value <NUM> is larger than the value of a normal temperature <NUM>. When the range is divided, the size of the range may be divided according to a portion even in a certain range. In addition, the number of divisions is also arbitrary.

<FIG> is a flowchart to determine abnormality of the compressor according to the discharge temperature. Since the discharge temperature is obtained by directly measuring the temperature of compressed air, the discharge temperature reacts more sensitively to a change in pressure than when heat transfer is measured in the first embodiment. For this reason, the flow is more simplified than measuring the temperature of the compressor, and is a flow in which the pressure is acquired at step <NUM>, the threshold value is determined from a threshold value map at step <NUM>, and a determination on temperature abnormality is performed at step <NUM>.

<FIG> shows a method by measuring a current value when pressure changes. Since the current value input into the motor is power used to compress gas, when the pressure increases, the current value also increases. Therefore, when a current value I acquired from the ammeter (not shown) provided in the inverter <NUM> exceeds a threshold value I(P), the control unit <NUM>.

A method for determining a threshold value I(P) of <NUM> corresponding to the pressure P is represented by equation (<NUM>) where the threshold value is a value obtained by adding a constant value to a normal current value Io(P) of <NUM>, equation (<NUM>) where the threshold value is expressed as a function of the pressure P using the arbitrary coefficients m and β, or the like, and more generally, may be represented by equation (<NUM>). <MAT> <MAT> <MAT>.

In <FIG>, the method for determining the threshold value shown in <FIG> is simplified similar to <FIG>. In the method for determining the threshold value shown in <FIG>, the pressure is divided into ranges, and the threshold value is set to a constant threshold value for each range as indicated by <NUM>. A threshold value <NUM> is larger than the value of a normal current <NUM>. When the range is divided, the size of the range may be divided according to a portion even in a certain range. In addition, the number of divisions is also arbitrary.

<FIG> is a flowchart to determine abnormality of the compressor according to the current value. Since the current value is directly affected by compressed air, the current value reacts more sensitively to a change in pressure than when heat transfer is measured in the first embodiment. For this reason, the flow is more simplified than measuring the temperature of the compressor, and is a flow in which the pressure is acquired at step <NUM>, the threshold value is determined from a threshold value map at step <NUM>, and a determination on abnormality is performed at step <NUM>.

<FIG> shows a method by measuring an input power value when pressure changes. The input power value is a value dependent on the pressure similar to the third embodiment, and when the pressure increases, the input value also increases. A method for determining a threshold value W(P) of <NUM> corresponding to the pressure P is represented by equation (<NUM>) where the threshold value is a value obtained by adding a constant value to a normal input value W(P) of <NUM>, equation (<NUM>) where the threshold value is expressed as a function of the pressure P using the arbitrary coefficients m and β, or the like, and more generally, may be represented by equation (<NUM>). <MAT> <MAT> <MAT>.

In <FIG>, the method for determining the threshold value shown in <FIG> is simplified similar to <FIG>. In the method for determining the threshold value shown in <FIG>, the pressure is divided into ranges, and the threshold value is set to a constant threshold value for each range as indicated by <NUM>. A threshold value <NUM> is larger than the value of a normal input power <NUM>. When the range is divided, the size of the range may be divided according to a portion even in a certain range. In addition, the number of divisions is also arbitrary.

<FIG> is a flowchart to determine abnormality of the compressor according to the input value. Since the input value is obtained by directly measuring compressed air, the input value reacts sensitively to a change in pressure. For this reason, the flow is more simplified than measuring the temperature of the compressor, and is a flow in which the pressure is acquired at step <NUM>, the threshold value is determined from a threshold value map at step <NUM>, and a determination on abnormality is performed at step <NUM>.

Incidentally, equations (<NUM>), (<NUM>), (<NUM>), (<NUM>), and (<NUM>) use an equation such as a quadratic function and an exponential function according to a distribution of the normal temperature, current, or power, or a value that matches the tendency of equations (<NUM>), (<NUM>), (<NUM>), (<NUM>), and (<NUM>) stored in a storage unit can be also used.

Claim 1:
A fluid machine comprising:
a fluid machine body;
a motor that drives the fluid machine body;
a temperature sensor (<NUM>, <NUM>) that measures a temperature of the fluid machine body; and
a control unit that controls the fluid machine body,
characterized in that
the control unit is configured to change a temperature threshold value based on a pressure of a fluid discharged by the fluid machine body, and to issue a notification when the temperature measured by the temperature sensor (<NUM>, <NUM>) exceeds the temperature threshold value.