JP2010240541A - Filter clogging detector of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter clogging detector which eliminates the need of a flowmeter, uses an inexpensive pressure detection means, and surely detects clogging of a filter. <P>SOLUTION: The filter clogging detector uses a pressure switch 11 to be operated when a differential pressure of a hydraulic fluid between before and after the hydraulic fluid of a reference flow rate passes through the filter 5 is equal to or higher than a clogging reference value indicating the clogging of the filter 5. The oil temperature/flow rate characteristics indicating the relation between an oil temperature T and the reference flow rate Qs are stored beforehand in a controller 9, a pump flow rate is adjusted to the reference flow rate Qs corresponding to the detected oil temperature T, and the clogging of the filter 5 is detected by the operation condition of the pressure switch 11 at the time. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a filter clogging detection device that detects clogging of a filter that filters hydraulic oil in a construction machine such as a hydraulic excavator.

  Conventionally, as shown in Patent Document 1, as a device of this type, the relationship between the oil temperature for each flow rate and the differential pressure before and after the filter that serves as a criterion for determining filter clogging at that oil temperature is previously mapped. When the flow rate of hydraulic oil passing through the filter, temperature (oil temperature), and differential pressure are detected, and the detected differential pressure is higher than the stored value obtained from the above map It is known that an alarm is issued if the filter is clogged.

JP 58-84015 A

  However, according to the above known technique, since the pressure must be detected in a wide pressure range corresponding to the flow rate change in the entire flow rate range, there is a possibility that the detection accuracy is deteriorated and clogging cannot be detected accurately.

  In addition, an expensive flow meter is required, and since only an expensive pressure sensor having a wide pressure range can be used as the pressure detection means, there is a problem that the equipment cost increases.

  Therefore, the present invention provides a filter clogging detection device for a construction machine that can reliably detect clogging of a filter while reducing the equipment cost.

  The invention according to claim 1 is a variable displacement hydraulic pump as a hydraulic source of a hydraulic actuator, a pump regulator for controlling the discharge flow rate of the hydraulic pump, and a return line to the tank for the hydraulic oil discharged from the hydraulic pump. In the filter clogging detection device for a construction machine provided with a filter for filtering at the oil temperature detecting means for detecting the temperature of the hydraulic oil passing through the filter, the oil temperature detected by the oil temperature detecting means is input. Control means, and pressure detection means for detecting a differential pressure before and after the filter. The control means stores an oil temperature / flow rate characteristic representing a reference flow rate for each oil temperature in advance, and The oil temperature detected by the temperature detecting means is compared with the oil temperature / flow rate characteristic to calculate a corresponding reference flow rate, and the hydraulic pressure pump is calculated by the pump regulator. The clogging reference is set as a value indicating the clogging of the filter with respect to the differential pressure when the hydraulic oil of the reference flow rate passes through the filter. The filter is clogged on the basis of a comparison between the value and the actual value detected by the pressure detecting means.

  According to a second aspect of the present invention, in the configuration of the first aspect, as the pressure detecting means, a pressure switch that operates when the differential pressure of the filter is equal to or more than the clogging reference value is used. Is configured to detect clogging.

  According to a third aspect of the present invention, in the configuration of the first or second aspect, a bypass check valve that opens at a set pressure is connected in parallel to the filter, and the clogging reference value is lower than a set pressure of the bypass check valve. It is set.

  According to a fourth aspect of the present invention, in the configuration according to any one of the first to third aspects, the control means stores a relationship between an oil temperature and a reference flow rate in a flow rate range equal to or less than a maximum discharge flow rate of the hydraulic pump. is there.

  According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, the control means is configured to provide a reference flow rate for each type of hydraulic oil based on oil temperature / flow rate characteristics of a plurality of types of hydraulic oil having different viscosities. Is configured to calculate.

  A sixth aspect of the present invention is the configuration according to any one of the first to fifth aspects, wherein the control means is provided for each type of filter based on oil temperature / flow rate characteristics for a plurality of types of filters having different oil temperature / flow rate characteristics. The reference flow rate is configured to be calculated.

  A seventh aspect of the present invention is the configuration according to any one of the first to sixth aspects, wherein the control means stores a plurality of oil temperature / flow rate characteristics corresponding to the degree of clogging of the filter and selects the selected oil The reference flow rate is calculated based on the temperature / flow rate characteristics.

  The invention according to claim 8 is the configuration according to any one of claims 1 to 7, wherein the control means stores a plurality of oil temperature / flow rate characteristics according to the degree of clogging of the filter, The current clogging degree is changed based on the pressure detected by the pressure detection means under the changing reference flow rate by changing between reference flow rates at a plurality of oil temperature / flow rate characteristics according to the clogging degree of the filter. It is configured to detect.

  According to the present invention, the oil temperature / flow rate characteristic representing the relationship between the oil temperature and the reference flow rate is stored in advance, the pump flow rate is adjusted to the reference flow rate according to the detected oil temperature, and the filter at that time Since it is configured to detect clogging of the filter based on the differential pressure, the pressure detecting means may detect pressure in a narrow range only in the vicinity of the clogging reference value.

  For this reason, it is possible to increase the accuracy of pressure detection and reliably detect clogging of the filter.

  In addition, an expensive flow meter is not required, and an inexpensive one having a narrow pressure range to be detected as the pressure detecting means as described above can be used. Therefore, compared with the known technique disclosed in Patent Document 1. The equipment cost is much cheaper.

  In particular, according to the invention of claim 2 in which an on / off type pressure switch is used instead of a pressure sensor, the effect of this point becomes remarkable.

  In the second aspect of the invention, the pressure switch may be set to operate when the filter is completely clogged (clogged state that requires immediate filter replacement), or a certain degree of clogging (for example, clogging degree 80%). Or 60%), the pressure switch may be set to operate.

  By the way, a bypass check valve is generally connected to the filter in parallel for oil escape when it is completely clogged.

  In this case, in the known technique, the bypass check valve opens at a low temperature when the viscosity of the oil becomes high, and there is a possibility that clogging of the filter cannot be detected.

  In this regard, according to the third aspect of the invention, the clogging reference value is set to a value lower than the set pressure of the bypass check valve, so that clogging can be reliably detected even at low temperatures.

  On the other hand, the reference flow rate may theoretically be the maximum flow rate of the pump, but in practice, the maximum flow rate may not be reached. Therefore, the reference flow rate is set to the maximum flow rate or less as in the invention of claim 4. Is desirable.

  According to the invention of claim 5, it can be used for a plurality of types of hydraulic oils having different viscosities, and according to the invention of claim 6, it can be used for a plurality of types of filters having different oil temperature / flow rate characteristics. Even if the hydraulic oil and the filter are different or different hydraulic oil and filter are used in the same machine, the clogging can be reliably detected.

  According to the seventh aspect of the present invention, it is possible to detect the presence or absence of clogging at a degree selected from among a plurality of clogging degrees (for example, 100%, 80%, 60%).

  According to the eighth aspect of the present invention, it is possible to detect the current degree of clogging by changing the reference flow rate between reference flow rates at a plurality of oil temperature / flow rate characteristics corresponding to the degree of clogging.

It is a figure which shows the circuit structure and block structure of the filter clogging detection apparatus which concern on basic embodiment of this invention. It is a figure which shows the characteristic of the oil temperature / reference | standard flow volume memorize | stored in the controller of the apparatus. It is a figure which shows the characteristic of the reference | standard flow volume and the differential pressure before and behind a filter similarly. It is a flowchart for demonstrating the clogging detection effect | action by the same apparatus. It is a figure which shows the characteristic of the oil temperature / reference | standard flow volume about several types of hydraulic fluid memorize | stored in the controller of the filter clogging detection apparatus which concerns on 1 of other embodiment of this invention. It is a figure which shows the characteristic of the oil temperature / reference | standard flow rate memorize | stored in the controller of the filter clogging detection apparatus which concerns on 2 of other embodiments of this invention. It is a figure which shows the characteristic of the oil temperature / reference | standard flow volume for every some clogging degree memorize | stored in the controller of the filter clogging detection apparatus which concerns on 3 of other embodiment of this invention.

Basic embodiment (see FIGS. 1 to 4)
FIG. 1 shows a circuit configuration and a block configuration of an embodiment apparatus taking a hydraulic cylinder circuit as an example.

  Reference numeral 1 denotes a variable displacement hydraulic pump. Pressure oil (operating oil) discharged from the hydraulic pump 1 is supplied to the hydraulic cylinder 3 via the control valve 2, and is supplied from the hydraulic cylinder 3 or via the relief valve 4. Is returned to the tank 6 through the filter 5.

  The filter 5 is connected in parallel with a bypass check valve 7 for allowing oil to escape to the tank 6 when it is completely clogged.

  The discharge flow rate of the hydraulic pump 1 is adjusted by a pump regulator 8, and the pump regulator 8 is controlled based on a command from a controller 9 as control means.

  In this apparatus, an oil temperature sensor (oil temperature detecting means) 9 that detects the temperature T of the hydraulic oil passing through the filter 5, and a pressure switch 11 that is turned on / off according to the differential pressure ΔP before and after the filter 5; The oil temperature signal from the oil temperature sensor 9 is input to the controller 9.

  As shown in FIG. 2, the pressure switch 11 has a differential pressure ΔP before and after the filter at a predetermined reference flow rate Qs out of the flow rate passing through the filter 5 greater than or equal to a clogging reference value ΔPs indicating clogging of the filter 5. When the pressure switch 11 is turned on, the display alarm means 12 is activated (for example, monitor display and buzzer operation).

  In this embodiment, the differential pressure reference value ΔPs is set to indicate complete clogging of the filter 5 (a state that requires immediate replacement at a clogging degree of 100%).

  By the way, in the configuration of this embodiment in which the bypass check valve 7 is connected in parallel to the filter 5, even when the filter 5 is not clogged, the bypass check valve 7 is opened at a low temperature when the oil viscosity is high. May end up. For this reason, if the differential pressure reference value ΔPs is set to a value equal to or higher than the pressure (set pressure) at which the bypass check valve 7 opens, clogging may not be detected.

  Therefore, in this embodiment, the differential pressure reference value ΔPs is set to a value lower than the pressure (set pressure) at which the bypass check valve 7 opens.

  On the other hand, as shown in FIG. 3, the controller 9 stores the characteristics of the oil temperature T and the reference flow rate Qs as a map, and calculates the reference flow rate Qs corresponding to the oil temperature T detected by the oil temperature sensor 9.

  The reference flow rate Qs may theoretically be the maximum flow rate of the pump, but in practice, the pump flow rate may not reach the maximum flow rate, so the reference flow rate Qs is set within a range A that is less than or equal to the maximum flow rate. Is desirable.

  The controller 9 also receives a signal from a key switch 13 for starting / stopping an engine (not shown) that is a drive source of the hydraulic pump 1.

  The operation of the entire apparatus including the operation of the controller 9 will be described with reference to the flowchart of FIG.

  In step S1, it is determined whether or not the key switch 13 is on (engine start). If YES, the oil temperature T is read in step S2.

  In step S3, a reference flow rate Qs corresponding to the detected oil temperature T is calculated from the characteristics of the oil temperature / reference flow rate in FIG. 3, and in step S4, the filtered flow rate is set to the calculated reference flow rate Qs. The pump flow rate is adjusted by the pump regulator 8.

  In step S5, the differential pressure is detected by the pressure switch 11, that is, the on / off operation of the pressure switch 11 is performed. In step S6, the display alarm means 12 is activated when the pressure switch is on, and inactive when the pressure switch is off. Will remain.

  Therefore, the operator only needs to replace the filter based on the operation / non-operation of the display alarm means 12 or enter a normal operation.

  Thus, while using the pressure switch 11 that operates when the differential pressure ΔP before and after the filter when the hydraulic oil of the reference flow rate Qs passes through the filter 5 is equal to or greater than the clogging reference value indicating clogging of the filter 5, An oil temperature / flow rate characteristic representing the relationship between the oil temperature T and the reference flow rate Qs is stored in the controller 9 in advance, and the pump flow rate is adjusted to the reference flow rate Qs corresponding to the detected oil temperature. Since the filter 5 is detected to be clogged according to the operating state of the pressure switch 11, only the oil temperature sensor 9 and the pressure switch 11 need be provided as detection means.

  That is, an expensive flow meter such as the known technique described in Patent Document 1 is not necessary, and an on / off type pressure switch 11 may be used instead of an expensive pressure sensor having a wide pressure range. For this reason, compared with a well-known technique, an installation cost can be remarkably cheap.

  In addition, clogging can be reliably detected depending on the operating state of the pressure switch 11 under the reference flow rate Qs.

  Further, since the clogging reference value ΔPs is set to a value lower than the set pressure of the bypass check valve 7, clogging can be reliably detected even at low temperatures.

Other Embodiments (1) As shown in FIG. 5, the oil temperature / flow rate characteristics of a plurality of types of hydraulic oils having different viscosities are stored in the controller 9, and among these, the operation actually used in the machine The type of oil may be selected by hydraulic oil selection means, the reference flow rate Qs may be calculated based on the oil temperature / flow rate characteristics of the selected hydraulic oil, and clogging may be detected.

  If it carries out like this, it can respond to several types of hydraulic fluid from which a viscosity differs, and the kind of hydraulic fluid which can be used increases.

  (2) The clogging detection may be performed by calculating the reference flow rate Qs for each type of the filter 5 based on the oil temperature / flow rate characteristics of the plurality of types of filters 5.

  In this case, for example, the controller 9 stores the oil temperature / flow rate characteristics for each type of the filter 5, and the type of the filter 5 that is actually used in the machine is selected by the filter selection means from among these. The reference flow rate Qs may be calculated based on the oil temperature / flow rate characteristic of the filter 5 to detect clogging.

  Alternatively, since the differential pressure ΔP is proportional to the viscosity and flow rate of the hydraulic oil, as shown in FIG. 6, one oil temperature / flow rate characteristic is stored in the controller 9, and the oil temperature T1 at one point and the reference By performing an approximation process for substituting the characteristics of the flow rate Qs1, one characteristic may correspond to a plurality of types of filters 5.

  (3) In the basic embodiment, the filter 5 is completely clogged (the degree of clogging is 100%). However, as shown in FIG. 7, the degree of clogging of the filter (100%, 80% in the figure, A plurality of oil temperature / flow rate characteristics according to three examples of 60% are stored, the reference flow rate Qs is calculated based on the oil temperature / flow rate characteristics selected by the clogging degree selection means, and clogging occurs. You may comprise so that a detection may be performed.

  (4) The reference flow rate Qs is configured to change between the reference flow rates Qs1, Qs2,. However, the present clogging degree may be detected based on the operating state of the pressure switch 11 under the changing reference flow rate.

  Note that this method may be used in combination with the basic embodiment shown in FIGS. 1 to 4 so as to monitor the subsequent complete clogging after detecting the degree of clogging.

  (5) Instead of the pressure switch 11 of the basic embodiment, a pressure sensor may be used as pressure detection means for detecting the differential pressure before and after the filter.

  Even in this case, since the pressure sensor only needs to detect the pressure within a narrow range only in the vicinity of the clogging reference value ΔPs, the pressure detection accuracy can be increased and the clogging of the filter 5 can be reliably detected.

  Moreover, an inexpensive pressure sensor having a narrow pressure range to be detected can be used as compared with the pressure sensor used in the known technique disclosed in Patent Document 1. That is, the equipment cost is low as in the basic embodiment.

  Even when this pressure sensor is used, the configurations of (1) to (5) of the basic embodiment and the other embodiments described above can be employed.

  In this case, in the basic embodiment (FIG. 1), the display / alarm means 12 is directly operated based on the operation of the pressure switch 11, whereas when a pressure sensor is used, the pressure signal from the sensor is used. May be input to the controller 9 and an operation signal may be output from the controller 9 to the display / alarm means 12. Alternatively, the display / alarm unit 12 itself may be provided with a function of converting a sensor signal into an operation signal.

  (6) In the above embodiment, the differential pressure before and after the filter 5 is detected. However, when the pressure after the filter 5 is extremely small, only the pressure before the filter is detected by the pressure switch 11 or the pressure sensor. You may make it detect. In this case as well, there is no change in detecting the differential pressure before and after the filter.

1 Hydraulic pump 5 Filter 7 Pump regulator 8 Controller (control means)
9 Oil temperature sensor 10 Pressure switch 11 Display / alarm means A Range below the pump maximum flow rate Qs Reference flow rate T Oil temperature ΔP Differential pressure ΔPs Differential pressure reference value

Claims (8)

  A variable displacement hydraulic pump as a hydraulic source of the hydraulic actuator, a pump regulator for controlling the discharge flow rate of the hydraulic pump, and a filter for filtering the hydraulic oil discharged from the hydraulic pump through a return line to the tank In the filter clogging detection device for a construction machine, the oil temperature detecting means for detecting the temperature of the hydraulic oil passing through the filter, the control means for inputting the oil temperature detected by the oil temperature detecting means, and the filter Pressure detecting means for detecting a differential pressure before and after the oil pressure. The control means stores in advance an oil temperature / flow rate characteristic representing a reference flow rate for each oil temperature, and is detected by the oil temperature detecting means. The oil temperature and the oil temperature / flow rate characteristic are collated to calculate a corresponding reference flow rate, and the pump regulator regulates the discharge flow rate of the hydraulic pump. The clogging reference value set as a value indicating the clogging of the filter and the pressure detection with respect to the differential pressure when the hydraulic oil of the reference flow rate passes through the filter. A filter clogging detection device for a construction machine, characterized in that the filter clogging is detected based on a comparison with an actual value detected by the means.   A pressure switch that operates when the differential pressure of the filter is equal to or higher than the clogging reference value is used as the pressure detection means, and the clogging of the filter is detected by the operation of the pressure switch. The filter clogging detecting device for construction machinery according to claim 1.   3. The construction according to claim 1, wherein a bypass check valve that opens at a set pressure is connected in parallel to the filter, and the clogging reference value is set to a value lower than a set pressure of the bypass check valve. Machine filter clogging detection device.   The said control means memorize | stores the relationship between oil temperature and a reference | standard flow volume in the flow rate range below the maximum discharge flow volume of the said hydraulic pump, The construction machine of any one of Claims 1-3 characterized by the above-mentioned. Filter clogging detection device.   The said control means is comprised so that the reference | standard flow volume for every kind of hydraulic oil may be calculated based on the oil temperature / flow volume characteristic about several types of hydraulic oil from which a viscosity differs. The filter clogging detection device for a construction machine according to any one of the preceding claims.   The control means is configured to calculate a reference flow rate for each filter type based on oil temperature / flow rate characteristics for a plurality of types of filters having different oil temperature / flow rate characteristics. The filter clogging detection device for a construction machine according to any one of 5.   The control means is configured to store a plurality of oil temperature / flow rate characteristics corresponding to the degree of clogging of the filter and calculate a reference flow rate based on the selected oil temperature / flow rate characteristics. The filter clogging detection device for a construction machine according to any one of claims 1 to 6.   The control means stores a plurality of oil temperature / flow rate characteristics according to the degree of clogging of the filter, and sets the reference flow rate as a reference with a plurality of oil temperature / flow rate characteristics according to the degree of clogging of the filter. 8. The method according to claim 1, wherein the current degree of clogging is detected based on the pressure detected by the pressure detection means under the changing reference flow rate. 2. The filter clogging detection device for a construction machine according to claim 1.

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