Lubrication Monitoring System

Abstract

The present disclosure relates to a lubrication monitoring system (15) configured to monitor a supply of lubricant in a handheld cutting tool (1) having a cutting unit (3,5). A lubricant tank (41) and a conduit (45) are configured to deliver a flow of lubricant from the tank (41) to the cutting unit (3,5). The lubrication monitoring system (15) comprises a heating element (29) and a sensor arrangement (31,33), the heating element (29) configured to heat the flow of lubricant. The sensor arrangement comprises a first sensor (31) disposed in the flow upstream of the heating element (29) and a second sensor (33) disposed in the flow downstream of the heating element. The lubrication monitoring system outputs a monitoring signal based on a sensed temperature difference between the first sensor (31) and the second sensor (33).

Description

[Technical Field]

[0001] The present disclosure relates to a lubrication monitoring system configured to monitor a supply of lubricant in a handheld cutting tool having a cutting unit, the lubrication monitoring system configured with a lubricant reservoir and a conduit for delivering a flow of lubricant from the reservoir to the cutting unit, the lubrication monitoring system including a heating element and a sensor arrangement, the heating element configured to heat the flow. [Background technology]

[0002] An example of such a monitoring system is disclosed in US Pat. No. 5,699,499. A lubrication system includes a tank and a conduit for conveying lubricant from the tank to a cutting unit of a cutting tool. A heating element and a control unit are provided, the heating element heating a portion of the lubrication system and the control unit monitoring the supply of lubricant detected by a change in temperature of the portion of the lubrication system.

[0003] One common problem with this type of system is improving the reliability of the monitoring of the lubricant supply. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 088891 Summary of the Invention [Problem to be solved by the invention]

[0005] Accordingly, it is an object of the present disclosure to provide a lubrication monitoring system having improved reliability for monitoring the supply of lubricant. [Means for solving the problem]

[0006] This object is achieved by a lubrication monitoring system as set forth in claim 1. More specifically, in a lubrication monitoring system of the first-mentioned type, the sensor arrangement comprises a first sensor arranged upstream of the heating element in the flow and a second sensor arranged downstream of the heating element. The lubrication monitoring system outputs a monitoring signal based on the detected temperature difference between the first and second sensors. This ensures that the lubricant flow is monitored with minimal influence, for example, by changes in ambient temperature.

[0007] The configuration may include a sensor canister that defines a lubricant flow path from the input to the output, and a circuit board that fits inside the sensor canister and holds the heating element and the first and second sensors so that they extend into the flow path, thereby efficiently connecting the heating element and sensors to the flow of lubricant. The sensor canister may further include a connector channel, separate from the flow path, through which a cable connecting to the circuit board extends.

[0008] Typically, the sensor container may be sealed by a molded resin on top of the circuit board. The first and second sensors may be NTC resistors.

[0009] The present disclosure further contemplates a lubrication monitoring system configured to monitor a supply of lubricant in a handheld cutting tool having a cutting unit, wherein a lubricant reservoir and a conduit are configured to deliver a flow of lubricant from the reservoir to the cutting unit, the lubricant monitoring system including a sensor arrangement that outputs a lubricant monitoring signal to a control unit in response to the lubricant flow. The monitoring system is configured to output the lubricant monitoring signal in the form of a periodic voltage change upon detecting a lubricant flow exceeding a predetermined threshold. This ensures that the absence of the periodic voltage change is easily detectable by the control unit, thereby ensuring reliable transmission of lubricant flow information.

[0010] The control unit may be configured to detect a constant low voltage when the lubricant flow is insufficient and a constant high voltage when the monitoring system is disconnected, thereby enabling the control unit to distinguish between these two fault conditions.

[0011] The present disclosure further contemplates a handheld cutting tool having a cutting unit, wherein a lubricant reservoir and a conduit are configured to deliver a flow of lubricant from the lubricant reservoir to the cutting unit, and wherein the handheld cutting tool further comprises a lubrication monitoring device configured to monitor the flow of lubricant. The lubricant reservoir comprises an outer recess, and the lubrication monitoring unit is disposed in the recess. This provides the possibility of manufacturing a complete lubrication unit that can be efficiently integrated into an assembly line.

[0012] Typically, the lubrication monitoring unit may be fitted into the recess using a snap fit for ease of assembly. In any of the scenarios outlined above, the tool may typically be a battery-operated chainsaw. [Brief explanation of the drawings]

[0013] [Figure 1] A diagram showing a chainsaw. [Figure 2A] First exploded view of the oil sensor unit. [Figure 2B] Second exploded view of the oil sensor unit. [Figure 2C] 1 is a diagram showing the structure of an oil sensor and the supply of oil to a saw chain; [Figure 3] FIG. 10 is a diagram showing an oil sensor mounted on an oil tank. [Figure 4A] 1 shows an oil sensor in communication with a chainsaw control unit. [Figure 4B] 1 shows an oil sensor in communication with a chainsaw control unit. [Figure 4C]1 shows an oil sensor in communication with a chainsaw control unit. [Figure 4D] 1 shows an oil sensor in communication with a chainsaw control unit. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present disclosure relates to a lubrication monitoring system for a chainsaw, and to a chainsaw including such a system. An example of a chainsaw 1 is shown in FIG. 1. The chainsaw includes a guide bar 3 carried by a saw chain 5 driven by a motor inside a chainsaw housing 6. The chainsaw is operated by a user holding its handle 7. In the illustrated case, the chainsaw is powered by a replaceable battery 8 secured in a battery compartment 10.

[0015] During operation, the saw chain 5 is lubricated by a steady but small flow of lubricant (such as mineral oil or vegetable oil) to ensure that the saw chain 5 progresses smoothly on the guide bar 3 and that the individual saw chain links can pivot relative to one another without significant friction. The oil is supplied from a lubricant tank, the cap 13 of which is shown in Figure 1. The flow of lubricant may be achieved by a pump that operates based on the chainsaw motor speed to provide a flow that varies slightly based on speed.

[0016] While the present disclosure is applicable in principle to both electric chainsaws and chainsaws powered by an internal combustion engine (ICE), it is particularly advantageous with respect to electric chainsaws (whether battery-operated or connected to a cable power outlet). In an ICE-powered chainsaw, the oil tank may be sized so that the lubricant tank is nearly empty at the same time as the gas tank, meaning that a skilled user can simultaneously replenish both fluid supplies. On the other hand, in a battery-operated saw, the battery 8 typically needs to be replaced and / or recharged more quickly, possibly sooner as the battery ages. In a saw powered from a power outlet, the saw can essentially operate indefinitely. Therefore, in an electric saw, there is no trigger to replenish the lubricant supply, and therefore it may be useful to monitor the lubricant flow and warn the user before the saw chain 5 dries out. However, even in an ICE-operated chainsaw, it may be useful to monitor the lubricant flow, as the lubricant flow may be blocked, for example, by contamination.

[0017] Accordingly, the present disclosure describes an improved lubrication monitoring system that can be used in this context. Figure 2A shows a first exploded view of a lubrication monitoring sensor unit 15. The sensor unit 15 includes an inlet 17 to a sensor receptacle 21 and an outlet 19 from the sensor receptacle 21. A circuit board 23 that includes an electrical system is fitted to the sensor receptacle 21. The sensor receptacle 21 includes a lubricant flow path 25. When the circuit board 23 is fitted to the receptacle 21, a closed path is formed by the lubricant flow path 25 from the receptacle inlet 17 to the outlet 19.

[0018] Separate from the flow path 25, the sensor container 21 further includes a connector channel 27 through which a cable connecting to the circuit board 23 can pass. The sensor container 21 can typically be manufactured by injection molding a plastic material. The sensor container 21 may be further closed by a lid not shown in FIG. 2A , and the remaining space above the circuit board 23 may be filled with molded resin to seal the interior of the container 21.

[0019] FIG. 2B shows a second exploded view of the lubrication monitoring sensor unit 15, exposing the bottom of the circuit board 23. The circuit board 23, as best seen in the enlarged portion of FIG. 2B, includes a heating element 29 on its bottom side that extends into the lubricant passages 25 to heat the lubricant therein. Such a heating element 29 may be useful, for example, in very cold climates where the lubricant may otherwise become too viscous to be properly delivered to the saw chain. Typically, the heating element 29 is a power resistor capable of generating approximately 0.5 W when powered by approximately 9 V DC.

[0020] The bottom side further comprises a first temperature sensor 31 and a second temperature sensor 33, which also extend into the lubricant flow path 25. The first sensor 31 is located upstream of the heating element 29 in the lubricant flow, and the second sensor 33 is located downstream of the heating element 29. Typically, the temperature sensors 31 and 33 may comprise NTC resistors, which may be identical. However, those skilled in the art will recognize several other types of temperature sensors that are possible in this context, such as PTC resistors, RTD resistors, thermocouples, etc.

[0021] FIG. 2C shows a schematic diagram of the structure of the lubrication monitoring and sensing arrangement and the supply of lubricant to the saw chain 5 on the guide bar 3. A lubricant tank 41 is provided for storing lubricant 43. The lubricant 43 may be replenished through an opening covered by the aforementioned cap 13. A conduit 45 connects the lubricant tank to the guide bar 3 at a location close to the saw chain 5. Such a conduit may include multiple tubes as shown. A lubricant pump 47 (e.g., with an impeller) supplies a quantity of oil to the saw chain 5. As mentioned above, a portion of the lubricant conduit comprises the lubricant monitoring unit 15, and the heating element 29 and the first and second temperature sensors 31, 33 reach into the lubricant flow.

[0022] Because one sensor 31 is located upstream of heating element 29 and the other 33 is located downstream of heating element 29, the other sensor 33 may sense a higher temperature if there is a significant flow of lubricant through conduit 45. Thus, lubrication monitoring unit 15 may output a monitoring signal based on the sensed temperature difference between first sensor 31 and second sensor 33. For example, monitoring unit 15 may be in communication with chainsaw control unit 49 as shown, and may communicate, for example, an OK signal as long as the lubricant flow is acceptable, or may communicate an estimated lubricant flow or the temperature difference itself.

[0023] As long as the lubricant reservoir 41 has a remaining amount of lubricant 43, the lubricant flow is not interrupted, and the lubricant pump 47 is functioning, there may be a significant temperature difference detected between the first sensor 41 and the second sensor 43. However, if this difference falls below a predetermined threshold, it may be assumed that the saw chain is not sufficiently lubricated. If this difference falls below a predetermined threshold, the control system 49 to which the lubrication monitoring unit 15 is connected may generate a fault indication and / or disable or limit operation of the saw to prevent damage or deterioration to the saw chain 5 or other components of the chainsaw 1.

[0024] In comparison to the first-mentioned known lubrication monitoring system in which temperature changes are detected, this configuration is less affected by changes in ambient temperature, for example, since changes in ambient temperature will similarly change the temperature readings of both sensors but will not change the temperature difference, thereby improving reliability.

[0025] 3 shows the lubrication monitoring sensor unit 15 mounted on the oil tank 41. Locating the lubrication monitoring unit 15 integrally with the lubricant tank 41 has been found to be advantageous as it simplifies the manufacture, maintenance and repair of the chainsaw 1. In the present disclosure, it is proposed to provide the lubricant tank 41 with an outer recess 51 that can be occupied by the lubricant monitoring unit 15. The lubricant tank 41 may be formed, for example, from two parts, both made of plastic by injection molding, with the outer recess 51 formed in one of them as part of a mold.

[0026] 3, the lubricant conduit 45 may be formed by a first pipe 53 connecting the lubricant tank 41 to the input 17 of the lubricant monitoring unit 15, a second pipe 55 connecting the output 19 of the lubricant monitoring unit 15 to the lubricant pump 47, and a third pipe 57 connecting the lubricant pump 47 to a nozzle 59 configured to be placed on the guide bar 3 of the chainsaw 1. Thus, as shown, the lubrication system may be provided as a whole assembled unit.

[0027] Typically, a form-fit configuration may be provided so that the lubrication monitoring unit 15 can be attached to the recess 51 of the lubricant tank 41 by sliding the lubrication monitoring unit 15 into the recess 51 using a snap-fit ​​locking structure.

[0028] FIG. 4A shows the lubrication monitoring sensor 15 unit in communication with the chainsaw's control unit 49. FIG. 4B shows the lubrication monitoring sensor 15 measuring acceptable lubricant flow and therefore communicating an OK signal. This is done by using, for example, a switching circuit to provide the control unit 49 with an output that varies between high and low states in terms of a voltage forming a square wave. When the lubricant reservoir 41 is empty, the flow ceases and there is no longer a temperature difference between the sensors 31 and 33 because there is no lubricant flow above the heating element 29. At this time, the lubrication monitoring sensor 15 may output a constant low voltage, as shown in FIG. 4C, which is detected by the control unit 49, which can then disable the chainsaw, for example, and provide a visual warning to the user, for example, using a user interface.

[0029] A third condition is shown in FIG. 4D , in which the lubrication monitoring sensor 15 is disconnected or the cable between the lubrication monitoring sensor 15 and the control unit 49 is faulty. In that case, for example, a pull-up resistor at the input of the control unit 49 can force the input to a constant high state, which the control unit can detect as a fault indication and provide a visual warning, for example, using a user interface. Because of the above configuration, the lubrication monitoring sensor 15 actively notifies the control unit whether lubrication flow is sufficient, and the control unit can detect both insufficient flow and a faulty sensor connection using a very simple communication scheme. However, it may be possible to apply other, more complex communication protocols (such as a Controller Area Network (CAN) bus protocol or a protocol that varies switching frequency depending on flow) with the hardware shown in FIGS. 1-3 .

[0030] The invention is not limited to the described embodiments but may be varied and modified in various ways within the scope of the appended claims.

Claims

1. A lubrication monitoring arrangement (15) configured to monitor the supply of lubricant in a handheld cutting tool (1) having cutting units (3, 5), comprising: a lubricant tank (41) and a conduit (45) configured to deliver a flow of lubricant from the lubricant tank (41) to the cutting unit (3, 5); the lubrication monitoring arrangement (15) comprises a heating element (29) and a sensor arrangement (31, 33), the heating element (29) being configured to heat the flow; the sensor arrangement comprises a first sensor (31) arranged in the flow upstream of the heating element (29) and a second sensor (33) arranged in the flow downstream of the heating element (29), and the lubrication monitoring arrangement (15) outputs a monitoring signal based on a detected temperature difference between the first sensor (31) and the second sensor (33); The lubrication monitoring arrangement (15) further comprises a sensor container (21) that forms a lubricant flow path (25) from an input portion (17) to an output portion (19), and a circuit board (23) that is fitted inside the sensor container (21) and that holds the heating element (29) and the first and second sensors (31, 33) so as to reach into the lubricant flow path (25); The lubrication monitoring arrangement, wherein the sensor container (21) further comprises a connector channel (27) separate from the lubricant flow path (25) through which a cable connecting to the circuit board passes.

2. A lubrication monitoring configuration as described in claim 1, further comprising a lid that closes the sensor container (21).

3. 2. The lubrication monitoring arrangement according to claim 1, wherein the interior of the sensor container (21) is sealed by a molded resin filled on top of the circuit board (23).

4. 2. The lubrication monitoring arrangement of claim 1, wherein the first sensor and the second sensor (31, 33) are NTC resistors.

5. A battery-operated chainsaw comprising a lubrication monitoring arrangement according to any one of claims 1 to 4.

6. A lubrication monitoring system (15, 49) configured to monitor the supply of lubricant in a handheld cutting tool (1) having a cutting unit (3, 5), comprising: a lubricant tank (41) and a conduit (45) configured to deliver a flow of lubricant from the lubricant tank (41) to the cutting unit (3, 5); the lubrication monitoring system (15) comprises a sensor arrangement (31, 33) and outputs a lubrication monitoring signal to a control unit (49) in response to the lubricant flow; the lubrication monitoring system is configured to output a lubrication monitoring signal in the form of a periodic voltage change when detecting a lubricant flow exceeding a predetermined threshold; The lubrication monitoring system (15) further comprises a sensor container (21) that forms a lubricant flow path (25) from an input portion (17) to an output portion (19), and a circuit board (23) that fits inside the sensor container (21) and holds the sensor arrangement (31, 33) so that it reaches into the lubricant flow path (25), The lubrication monitoring system further comprises a connector channel (27) separate from the lubricant flow path (25) for a cable to be connected to the circuit board.

7. 7. The lubrication monitoring system of claim 6, wherein the control unit (49) is configured to detect a constant low voltage when the lubricant flow is insufficient and a constant high voltage when the sensor arrangement is disconnected.

8. A battery-operated chainsaw comprising a lubrication monitoring system according to claim 6 or 7.

9. A handheld cutting tool (1) comprising a cutting unit (3, 5) and a lubrication monitoring arrangement according to claim 1 or a lubrication monitoring system according to claim 6, The handheld cutting tool, wherein the lubricant reservoir (41) comprises an outer recess (51), and the lubrication monitoring arrangement or the lubrication monitoring system is arranged in the recess.

10. A handheld cutting tool as described in Claim 9, wherein the lubrication monitoring configuration or the lubrication monitoring system is fitted into the recess (51) using a snap fit.

11. 10. The handheld cutting tool of claim 9, which is a battery-operated chainsaw.

12. A handheld cutting tool as described in claim 10, which is a battery-operated chainsaw.

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