Snowblower

Abstract

To suppress rotating parts from being damaged while suppressing workload increase of operators.SOLUTION: A snow blower 1 includes an operating part 34 that performs snow removing work, a drive source 10 that rotates the operating part 34, a friction clutch 44 that is provided in a rotation transmission path P from the drive source 10 to the operating part 34, idles and cuts off the transmission of rotation from the driving source 10 to the operating part 34 when a torque of a predetermined value or more is applied, and a control device 74 that controls the operation of the drive source 10 based on the estimated temperature of the friction clutch 44.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a snow remover.

Background Art

[0002] Conventionally, a snow remover including a working part (for example, an auger claw) that performs a snow removal operation and a drive source (for example, an internal combustion engine or an electric motor) that rotates the working part is known.

[0003] In such a snow remover, the working part may lock when it bites into obstacles such as small stones and ice blocks or gets caught on a step of the snow removal surface (that is, the working part may become unable to rotate). If the transmission of rotation from the drive source to the working part continues in a state where the working part is locked like this, a large load is applied to the rotating parts (for example, a shaft and an auger claw) that constitute the snow remover, and there is a risk of causing damage to the rotating parts.

[0004] Therefore, a snow remover provided with a vulnerable part (for example, a shear bolt) in the rotational transmission path from the drive source to the working part is known (see Patent Document 1). In such a snow remover, when the working part locks and a torque exceeding a predetermined value is applied to the vulnerable part, the vulnerable part breaks, and the transmission of rotation from the drive source to the working part is interrupted. Thereby, damage to the rotating parts is suppressed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the snow remover as described above, if the vulnerable part is frequently damaged, the operator may have to frequently perform the replacement work of the vulnerable part in the snow, and there is a risk of increasing the burden on the operator.

[0007] In view of the above background, the present invention aims to provide a snowblower that can suppress damage to rotating parts while suppressing an increase in the burden on the operator. [Means for solving the problem]

[0008] To solve the above problems, one aspect of the present invention is a snowblower (1) comprising: a work unit (34) for performing snow removal work; a drive source (10) for rotating the work unit; a friction clutch (44) provided in a rotation transmission path (P) from the drive source to the work unit, which slips when torque exceeds a predetermined value and interrupts the transmission of rotation from the drive source to the work unit; and a control device (74) that controls the operation of the drive source based on the estimated temperature of the friction clutch.

[0009] In this embodiment, when the working part locks up, the friction clutch can interrupt the transmission of rotation from the drive source to the working part. This suppresses excessive load on the rotating parts that make up the snowblower and prevents damage to the rotating parts. Furthermore, by interrupting the transmission of rotation from the drive source to the working part with the friction clutch, the transmission of rotation from the drive source to the working part can be interrupted without damaging any parts. This prevents an increase in the burden on the operator due to the work of replacing damaged parts.

[0010] Furthermore, by controlling the operation of the drive source based on the estimated temperature of the friction clutch, overheating of the friction clutch can be suppressed. This prevents changes in the frictional force on the surface of the friction clutch components due to overheating, thereby improving the stability of the friction clutch's operation.

[0011] In the above embodiment, the control device may store a temperature change map (M1) that defines the relationship between the number of free rotations of the friction clutch per unit time and the amount of temperature change of the friction clutch per unit time, and calculate an estimated temperature of the friction clutch based on the temperature change map (step ST4).

[0012] According to this embodiment, the estimated temperature of the friction clutch can be calculated without using a dedicated temperature sensor. Therefore, the complexity of the snowblower's configuration can be suppressed.

[0013] In the above embodiment, the snowblower further comprises a drive rotation speed detection unit (71) that detects the drive rotation speed, which is the number of rotations of the drive source per unit time; a work rotation shaft (43) that transmits the rotation of the friction clutch to the work unit; and a work rotation speed detection unit (72) that detects the work rotation speed, which is the number of rotations of the work rotation shaft per unit time. The control device may calculate the number of free rotations of the friction clutch per unit time based on the drive rotation speed and the work rotation speed, and calculate the estimated temperature of the friction clutch by referring to the temperature change map based on the number of free rotations of the friction clutch per unit time (step ST4).

[0014] According to this embodiment, the number of free rotations of the friction clutch per unit time can be accurately calculated. Therefore, the estimated temperature of the friction clutch can be accurately calculated.

[0015] In the above embodiment, the control device may perform an operation stop process to stop the operation of the drive source when the estimated temperature of the friction clutch reaches a predetermined operation stop temperature (step ST7).

[0016] According to this embodiment, overheating of the friction clutch can be suppressed more effectively. Therefore, the stability of the friction clutch's operation can be further improved.

[0017] In the above embodiment, the control device may set the operating stop temperature based on the rotational speed of the drive source per unit time at the start of free rotation of the friction clutch (ST5).

[0018] According to this embodiment, the operating shutdown temperature can be appropriately set based on the rotational speed of the drive source per unit time at the start of free rotation of the friction clutch. Therefore, the timing for executing the operating shutdown process can be appropriately determined.

[0019] In the above aspect, after executing the operation stop process, the control device may prohibit the restart of the drive source until the estimated temperature of the friction clutch drops to an operation permission temperature lower than the operation stop temperature (step ST9).

[0020] According to this aspect, it is possible to suppress the temperature of the friction clutch from reaching the operation stop temperature repeatedly within a short period. Therefore, overheating of the friction clutch can be more effectively suppressed.

[0021] In the above aspect, when the control device detects the idling of the friction clutch (step ST11: Yes), it executes an operation stop process to stop the operation of the drive source (step ST13), and after executing the operation stop process, it may prohibit the restart of the drive source until the estimated temperature of the friction clutch drops to a predetermined operation permission temperature (steps ST17, ST18).

[0022] According to this aspect, overheating of the friction clutch can be more effectively suppressed. Therefore, the operating stability of the friction clutch can be further enhanced.

[0023] In the above aspect, the control device stores a temperature decrease amount map (M2) that defines the relationship between the length of the idling stop period, which is the period during which the idling of the friction clutch has stopped, and the temperature decrease amount of the friction clutch, and may calculate the estimated temperature of the friction clutch based on the temperature decrease amount map while prohibiting the restart of the drive source (step ST8).

[0024] According to this aspect, the estimated temperature of the friction clutch can be accurately calculated based on the length of the idling stop period. Therefore, the timing for permitting the restart of the drive source can be appropriately determined.

[0025] In the above aspect, the snow remover further includes an output device (73) that outputs information to an operator, and when the control device executes the operation stop process a predetermined number of times or more within a predetermined time, the control device may cause the output device to output warning information.

[0026] According to this aspect, it is possible to make the operator recognize that the operation stop process is frequently executed, and prompt the operator to remove the cause of the operation stop process (for example, obstacles such as small stones or ice blocks that the working part has bitten into). Thereby, it is possible to suppress failures of the friction clutch and the working part.

Effects of the Invention

[0027] According to the above aspect, it is possible to provide a snow remover capable of suppressing an increase in the burden on an operator while suppressing damage to rotating parts.

Brief Description of the Drawings

[0028] [Figure 1] Side view showing a snow remover according to a first embodiment of the present invention [Figure 2] Perspective view showing a part of a rotational transmission device according to a first embodiment of the present invention [Figure 3] Schematic view showing a snow remover according to a first embodiment of the present invention [Figure 4] Graph showing a temperature rise amount map according to a first embodiment of the present invention [Figure 5] Graph showing a temperature drop amount map according to a first embodiment of the present invention [Figure 6] Flowchart showing temperature rise suppression control according to a first embodiment of the present invention [Figure 7] Graph exemplifying changes in the estimated temperature of a friction clutch according to a first embodiment of the present invention [Figure 8] Flowchart showing temperature rise suppression control according to a second embodiment of the present invention [Figure 9] Flowchart showing temperature estimation processing according to a second embodiment of the present invention

Modes for Carrying Out the Invention

[0029] (First Embodiment) <Snowblower 1> Hereinafter, a snowblower 1 according to the first embodiment of the present invention will be described with reference to the drawings. Hereinafter, terms indicating directions such as front and back, left and right, up and down will be used based on the direction as seen from the perspective of the operator operating the snowblower 1. The arrow Fr appropriately attached to each figure indicates the front of the snowblower 1.

[0030] First, with reference to Figure 1, let's explain the overall configuration of snowblower 1.

[0031] Snowblower 1 is a walk-behind type snowblower in which an operator walks behind it to perform snow removal work. Snowblower 1 has a frame 3 that forms its structure, a pair of travel devices 4 provided on both the left and right sides of the frame 3 (only the travel device 4 provided on the left side of the frame 3 is shown in Figure 1), a handle device 5 provided at the rear of the frame 3, a blower device 6 provided at the front of the frame 3, an auger device 7 provided in front of the blower device 6, and a rotation transmission device 8 provided in the center of the frame 3.

[0032] An internal combustion engine (an example of a drive source: hereinafter referred to as "engine 10") is supported on the upper part of the aircraft body 3. The engine 10 has a crankshaft 11 that is rotatable around an axis extending in the front-rear direction. In other embodiments, the crankshaft 11 may also be rotatable around an axis extending in the vertical direction. The engine 10 has an ignition device 12 for igniting the fuel-air mixture. The ignition device 12 employs a CDI (Capacitor Discharge Ignition) system. In other embodiments, the ignition device 12 may employ a system other than the CDI system (for example, a transistor system).

[0033] Each running gear 4 includes a running motor 14, a drive wheel 15 connected to the running motor 14, a driven wheel 16 located behind the drive wheel 15, and a crawler belt 17 wrapped around the drive wheel 15 and the driven wheel 16. In other embodiments, the driven wheel 16 may be located in front of the drive wheel 15.

[0034] The handle device 5 has left and right arms 20 (only the left arm 20 is shown in Figure 1) extending upward and rearward from the lower part of the machine body 3, and input devices 21 attached to the upper ends of the left and right arms 20. A grip 20a for the operator to grasp is provided at the upper end of each arm 20. The input device 21 is a device that receives input operations from the operator. The input device 21 includes, for example, a travel lever 22 that receives travel operations for the snowblower 1, and a snow removal switch 23 that receives operation operations for the blower device 6 and the auger device 7.

[0035] The blower device 6 includes a blower housing 26 fixed to the front of the machine body 3, a blower 27 housed in the blower housing 26, and a chute 28 extending upward from the upper end of the blower housing 26.

[0036] The auger device 7 includes an auger housing 31 fixed to the front of the blower housing 26, a transmission 32 housed in the auger housing 31, an auger shaft 33 rotatably supported by the auger housing 31, and an auger claw 34 (an example of a working part) attached to the auger shaft 33. The auger claw 34 includes a first claw portion that rotates in one direction when viewed from the side, and a second claw portion that rotates in the opposite direction when viewed from the side. In other embodiments, the auger claw 34 may consist only of a claw portion that rotates in one direction when viewed from the side. A weak point 35 (e.g., a shear bolt) is provided between the auger shaft 33 and the auger claw 34. The weak point 35 is configured to break when a torque exceeding a predetermined value is applied, thereby interrupting the transmission of rotation from the auger shaft 33 to the auger claw 34.

[0037] The rotational transmission device 8 connects the crankshaft 11 to the blower 27 and the transmission 32, and is configured to transmit the rotation of the crankshaft 11 to the blower 27 and the transmission 32. The rotational transmission device 8 constitutes part of the rotational transmission path P from the engine 10 to the auger claws 34. Details of the rotational transmission device 8 will be described later.

[0038] Next, we will explain the overall operation of snowblower 1.

[0039] When an operator controls the snowblower 1 using the travel lever 22 on the input device 21, the travel motors 14 of each travel device 4 rotate. The rotation of the travel motors 14 is transmitted to the crawler belts 17 via the drive wheels 15, causing the crawler belts 17 to rotate. This causes the snowblower 1 to move.

[0040] Furthermore, when the operator operates the blower device 6 and auger device 7 using the snow removal switch 23 on the input device 21, the crankshaft 11 of the engine 10 rotates. The rotation of the crankshaft 11 is transmitted to the blower 27 via the rotation transmission device 8, causing the blower 27 to rotate. The rotation of the crankshaft 11 is also transmitted to the auger claws 34 via the rotation transmission device 8, the transmission 32, and the auger shaft 33, causing the auger claws 34 to rotate. When the auger claws 34 rotate, the snow in front of the snowblower 1 is crushed by the auger claws 34 and collected in the center of the auger housing 31 in the left-right direction. In other words, snow removal is performed by the auger claws 34. The snow collected in the center of the auger housing 31 in the left-right direction is introduced into the blower housing 26 and projected in the desired direction via the chute 28 by the blower 27.

[0041] <Rotational transmission device 8> Next, the configuration of the rotary transmission device 8 will be described.

[0042] Referring to Figures 2 and 3, the rotational transmission device 8 comprises a reduction mechanism 41, a driven shaft 42, a working rotation shaft 43, a friction clutch 44, and a mounting member 45.

[0043] The reduction mechanism 41 includes a drive pulley 52 attached to the crankshaft 11 of the engine 10 via an electromagnetic clutch 51, a driven pulley 53 positioned below the drive pulley 52, and a transmission belt 54 wrapped around the drive pulley 52 and the driven pulley 53. The electromagnetic clutch 51 switches the connection state / disconnection state between the crankshaft 11 and the drive pulley 52.

[0044] The driven shaft 42 extends in the front-rear direction. The driven shaft 42 is fixed to the driven pulley 53 of the reduction mechanism 41. This allows the driven shaft 42 to rotate integrally with the driven pulley 53.

[0045] The working rotation shaft 43 extends in the front-rear direction. The working rotation shaft 43 is arranged coaxially with the driven shaft 42. The working rotation shaft 43 is connected to the transmission 32 of the auger device 7. A fixing piece 56 is fixed to the outer circumference of one end of the working rotation shaft 43. A pair of gear sections 57 and a pair of detection sections 58 are provided on the outer circumference of the fixing piece 56 at circumferential intervals.

[0046] The friction clutch 44 includes a first drive friction member 61, a second drive friction member 62, a driven friction member 63, and a plurality of biasing members 64. Note that the second drive friction member 62 and the plurality of biasing members 64 are not shown in Figure 3.

[0047] The first drive friction member 61 is disc-shaped. The first drive friction member 61 is fitted onto the driven pulley 53 and / or the driven shaft 42. As a result, the first drive friction member 61 can rotate integrally with the driven pulley 53 and the driven shaft 42.

[0048] The second drive friction member 62 is disc-shaped. The second drive friction member 62 is attached to the driven pulley 53 via a plurality of fastening members 66, which consist of bolts 66a and nuts 66b. As a result, the second drive friction member 62 can rotate integrally with the driven pulley 53 and the driven shaft 42.

[0049] The driven friction member 63 is disc-shaped. The driven friction member 63 is positioned between the first and second drive friction members 61 and 62 and is in contact with them. An inner circumference gear 67 is provided on the inner circumference of the driven friction member 63. The inner circumference gear 67 meshes with a pair of gear portions 57 provided on the fixing piece 56 of the working rotation shaft 43. As a result, the driven friction member 63 can rotate integrally with the working rotation shaft 43.

[0050] Each biasing member 64 is composed of a coil spring. The biasing members 64 are attached to the fastening member 66. The biasing members 64 bias the second drive friction member 62 toward the first drive friction member 61 via the fastening member 66. As a result, the first and second drive friction members 61 and 62 are pressed against the driven friction member 63.

[0051] The mounting member 45 is attached to the machine body 3 (see Figure 1) via a fastening member (not shown). The mounting member 45 holds a bearing (not shown) for supporting the working rotation shaft 43.

[0052] Next, the operation of the rotary transmission device 8 will be explained.

[0053] When the engine 10 starts and the crankshaft 11 rotates, the rotation of the crankshaft 11 is transmitted to the driven shaft 42 and the first and second drive friction members 61 and 62 via the reduction mechanism 41, causing the driven shaft 42 and the first and second drive friction members 61 and 62 to rotate together. At this time, the rotation of the crankshaft 11 is reduced by a predetermined reduction ratio by the reduction mechanism 41.

[0054] If the auger claws 34 are not locked and the torque applied to the friction clutch 44 is less than a predetermined value, the rotation of the first and second drive friction members 61 and 62 is transmitted to the driven friction member 63, causing the driven friction member 63 to rotate. The rotation of the driven friction member 63 is transmitted to the auger claws 34 via the work rotation shaft 43, the transmission 32, and the auger shaft 33.

[0055] On the other hand, when the auger claws 34 lock and the torque applied to the friction clutch 44 exceeds a predetermined value, the rotation of the first and second drive friction members 61 and 62 is not transmitted to the driven friction member 63, and the first and second drive friction members 61 and 62 rotate freely relative to the driven friction member 63. In other words, when the torque applied to the friction clutch 44 exceeds a predetermined value, the friction clutch 44 rotates freely. This interrupts the transmission of rotation from the engine 10 to the auger claws 34. Note that the minimum torque at which the friction clutch 44 rotates freely is set lower than the torque at which the fragile part 35 breaks.

[0056] <Control system for snowblower 1> Next, we will describe the control system of the snowblower 1.

[0057] Referring to Figure 3, in addition to the above components, the snowblower 1 includes a drive rotation speed detection unit 71, a work rotation speed detection unit 72, an output device 73, and a control device 74.

[0058] The drive speed detection unit 71 is provided in the ignition device 12 of the engine 10. The drive speed detection unit 71 detects the rotational speed of the engine 10 per unit time (hereinafter referred to as "drive speed") based on the ignition pulse signal output from the ignition device 12 when igniting the fuel-air mixture. In other embodiments, the drive speed detection unit 71 may also detect the drive speed based on a signal other than the ignition pulse signal (for example, the rotation signal of the crankshaft 11). The drive speed detection unit 71 outputs the detected drive speed to the control device 74.

[0059] Referring to Figure 2, the working rotation speed detection unit 72 is attached to the mounting member 45 of the rotation transmission device 8. The working rotation speed detection unit 72 is composed of, for example, a pulser coil (pickup coil). In other embodiments, the working rotation speed detection unit 72 may be composed of a detection device other than a pulser coil (for example, a rotary encoder). The working rotation speed detection unit 72 detects the rotation speed of the working rotation shaft 43 per unit time (hereinafter referred to as "working rotation speed") by detecting the rotational position of a pair of detectable parts 58 provided on the fixing piece 56 of the working rotation shaft 43. The working rotation speed detection unit 72 outputs the detected working rotation speed as a voltage waveform to the control device 74.

[0060] The output device 73 is provided, for example, in the steering wheel device 5 (see Figure 1). Based on signals from the control device 74, the output device 73 outputs various information to the occupant. The output device 73 includes, for example, a warning light, a speaker, an LCD screen, etc.

[0061] The control device 74 is an electronic control unit (ECU) that includes an arithmetic processing unit (CPU, MPU, or other processor) and a memory device (ROM, RAM, or other memory). The control device 74 may be configured as a single piece of hardware, or as a unit consisting of multiple pieces of hardware.

[0062] The control device 74 is connected to the ignition device 12 of the engine 10. The control device 74 controls the ignition of the air-fuel mixture by the ignition device 12 by outputting a control signal to the ignition device 12. In this way, the control device 74 controls the operation of the engine 10. For example, when the engine 10 is running, if the working rotation speed detection unit 72 does not detect a working rotation speed of a predetermined number or more, the control device 74 outputs an operation stop signal to the ignition device 12, thereby stopping the ignition of the air-fuel mixture by the ignition device 12. In this way, the control device 74 stops the operation of the engine 10.

[0063] Referring to Figure 4, the control device 74 stores a temperature rise map M1 (an example of a temperature change map). The temperature rise map M1 defines the relationship between the number of free rotations of the friction clutch 44 per unit time (hereinafter referred to as "number of free rotations of the friction clutch 44") and the temperature rise of the friction clutch 44 per unit time (hereinafter referred to as "temperature rise of the friction clutch 44"). The temperature rise map M1 is set such that the temperature rise of the friction clutch 44 increases as the number of free rotations of the friction clutch 44 increases. The temperature rise map M1 may be in graph format (see Figure 4) or in a format other than graph format (for example, table format).

[0064] Referring to Figure 5, the control device 74 stores a temperature drop map M2. The temperature drop map M2 defines the relationship between the length of the idle stop period and the temperature drop of the friction clutch 44. Here, the idle stop period is the period during which the friction clutch 44 is not free-spinning. The temperature drop map M2 is set so that the longer the idle stop period, the greater the temperature drop of the friction clutch 44. The temperature drop map M2 may be in graph format (see Figure 5) or in a format other than graph format (for example, table format).

[0065] <Temperature rise suppression control> Next, the temperature rise suppression control performed by the control device 74 will be described with reference to Figure 6. The temperature rise suppression control is a control to suppress the temperature rise of the friction clutch 44. For example, the temperature rise suppression control is repeatedly performed from immediately after the engine 10 is started.

[0066] When the temperature rise suppression control is started, the control device 74 determines whether or not slippage of the friction clutch 44 is occurring based on the drive speed output from the drive speed detection unit 71 and the work speed output from the work speed detection unit 72 (step ST1). For example, the control device 74 calculates the rotational speed of the driven pulley 53 and the driven shaft 42 (hereinafter referred to as "driven speed") by multiplying the drive speed by the reduction ratio of the reduction mechanism 41, and determines that slippage of the friction clutch 44 is occurring if there is a difference of a predetermined value or more between the driven speed and the work speed.

[0067] If it is determined that the friction clutch 44 is not slipping (step ST1: No), the control device 74 calculates the estimated temperature of the friction clutch 44 (step ST2). For example, the control device 74 calculates the temperature drop of the friction clutch 44 by referring to the temperature drop map M2 based on the length of the slip-stop period. Next, the control device 74 calculates the estimated temperature of the friction clutch 44 by subtracting the temperature drop from the first reference temperature. In the first temperature rise suppression control performed after the engine 10 starts, the control device 74 may set the above first reference temperature based on a predetermined detected value (e.g., ambient temperature). Alternatively, in the first temperature rise suppression control performed after the engine 10 starts, the control device 74 may set the above first reference temperature to the ambient temperature of the friction clutch 44 determined by the exhaust heat of the engine 10. On the other hand, in the temperature rise suppression control performed for the second time or later after the engine 10 has started, the control device 74 may set the estimated temperature of the friction clutch 44 calculated in the previous temperature rise suppression control (for example, the last temperature rise suppression control in which it was determined that slippage of the friction clutch 44 was occurring) to the above-mentioned first reference temperature.

[0068] On the other hand, if it is determined that the friction clutch 44 is slipping (step ST1: Yes), the control device 74 obtains the slipping start rotation speed (step ST3). Here, the slipping start rotation speed is the drive rotation speed at which the friction clutch 44 starts slipping.

[0069] Next, the control device 74 calculates the estimated temperature of the friction clutch 44 (step ST4). For example, the control device 74 calculates the driven rotation speed by multiplying the driving rotation speed by the reduction ratio of the reduction mechanism 41. Next, the control device 74 calculates the number of free rotations of the friction clutch 44 by subtracting the working rotation speed from the driven rotation speed. Next, the control device 74 calculates the temperature rise of the friction clutch 44 by referring to the temperature rise map M1 based on the number of free rotations of the friction clutch 44. Next, the control device 74 calculates the estimated temperature of the friction clutch 44 by adding the temperature rise to the second reference temperature. In the first temperature rise suppression control performed after the engine 10 starts, the control device 74 should set the second reference temperature based on a predetermined detected value (e.g., ambient temperature). On the other hand, in the second and subsequent temperature rise suppression control performed after the engine 10 starts, the control device 74 should set the estimated temperature of the friction clutch 44 calculated in the previous temperature rise suppression control to the second reference temperature.

[0070] Next, the control device 74 sets the operating shutdown temperature based on the idle speed at which idling begins (step ST5). For example, the control device 74 sets a lower operating shutdown temperature the higher the idle speed at which idling begins.

[0071] Next, the control device 74 determines whether the estimated temperature of the friction clutch 44 is above the operating stop temperature (step ST6). That is, the control device 74 determines whether the estimated temperature of the friction clutch 44 has reached the operating stop temperature. If the estimated temperature of the friction clutch 44 is below the operating stop temperature (step ST6: No), the control device 74 terminates the temperature rise suppression control.

[0072] On the other hand, if the estimated temperature of the friction clutch 44 is above the operating stop temperature (step ST6: Yes), the control device 74 performs an operation stop process (step ST7). In the operation stop process, the control device 74 outputs an operation stop signal to the ignition device 12, thereby stopping the ignition of the air-fuel mixture by the ignition device 12. As a result, the control device 74 stops the operation of the engine 10. In other embodiments, if the estimated temperature of the friction clutch 44 is above the operating stop temperature (step ST6: Yes), the control device 74 may reduce the upper limit of the drive speed instead of performing the operation stop process.

[0073] Furthermore, when the friction clutch 44 is idling, the higher the rotational speed at which idling begins, the faster the temperature rise of the friction clutch 44, and the greater the degree of damage to the friction clutch 44. Therefore, as described above, the control device 74 sets the operating stop temperature lower the higher the rotational speed at which idling begins (step ST5). As a result, the higher the rotational speed at which idling begins, the earlier the estimated temperature of the friction clutch 44 will rise above the operating stop temperature (step ST6: Yes), and the operating stop process can be executed (step ST7). This makes it possible to suppress damage to the friction clutch 44.

[0074] Next, the control device 74 calculates the estimated temperature of the friction clutch 44 (step ST8). For example, the control device 74 calculates the temperature drop of the friction clutch 44 by referring to the temperature drop map M2 based on the length of the idle stop period. Next, the control device 74 calculates the estimated temperature of the friction clutch 44 by subtracting the temperature drop of the friction clutch 44 from the third reference temperature. In step ST8, which is executed for the first time after the operation stop process, the control device 74 may set the estimated temperature of the friction clutch 44 calculated in step ST4 as the third reference temperature. On the other hand, in step ST8, which is executed for the second time or later after the operation stop process, the control device 74 may set the estimated temperature of the friction clutch 44 calculated in the previous step ST8 as the third reference temperature.

[0075] Next, the control device 74 determines whether the estimated temperature of the friction clutch 44 is below the operating permission temperature (step ST9). The operating permission temperature is set lower than the operating stop temperature. If the estimated temperature of the friction clutch 44 is not below the operating permission temperature (step ST9: No), the control device 74 returns to step ST8 and recalculates the estimated temperature of the friction clutch 44. In this way, after executing the operation stop process, the control device 74 prohibits the restart of the engine 10 until the estimated temperature of the friction clutch 44 drops to the operating permission temperature.

[0076] On the other hand, if the estimated temperature of the friction clutch 44 falls below the operating permission temperature (step ST9: YES), the control device 74 permits the restart of the engine 10 (step ST10) and terminates the temperature rise suppression control.

[0077] Furthermore, if the control device 74 executes the operation stop process more than a predetermined number of times within a predetermined time, it will cause the output device 73 to output warning information. For example, if the output device 73 includes a warning light, the control device 74 may turn on the warning light. If the output device 73 includes a speaker, the control device 74 may generate a warning sound from the speaker. If the output device 73 includes a liquid crystal screen, the control device 74 may display a warning message on the liquid crystal screen.

[0078] <Estimated temperature change of friction clutch 44> Next, we will explain the estimated temperature change of the friction clutch 44, using the case where the friction clutch 44 repeatedly slips as an example.

[0079] Referring to Figure 7, if the friction clutch 44 slips during the period between time t1 and time t2, the estimated temperature of the friction clutch 44 rises (see step ST4 of the temperature rise suppression control). However, at time t2, the estimated temperature of the friction clutch 44 has not reached the operating stop temperature, so the engine 10 does not stop operating (see step ST6 of the temperature rise suppression control).

[0080] When the free-spinning of the friction clutch 44 stops during the period between time t2 and time t3, the estimated temperature of the friction clutch 44 decreases (see step ST2 of the temperature rise suppression control).

[0081] If the friction clutch 44 slips during the period between time t3 and time t4, the estimated temperature of the friction clutch 44 rises (see step ST4 of the temperature rise suppression control). However, at time t4, the estimated temperature of the friction clutch 44 has not reached the operating stop temperature, so the engine 10 does not stop operating (see step ST6 of the temperature rise suppression control).

[0082] When the free-spinning of the friction clutch 44 stops during the period between time t4 and time t5, the estimated temperature of the friction clutch 44 decreases (see step ST2 of the temperature rise suppression control).

[0083] If the friction clutch 44 slips during the period between time t5 and time t6, the estimated temperature of the friction clutch 44 rises (see step ST4 of the temperature rise suppression control). At time t6, the estimated temperature of the friction clutch 44 reaches the shutdown temperature, so the shutdown process is executed and the engine 10 is stopped (see steps ST6 and ST7 of the temperature rise suppression control).

[0084] During the period between time t6 and time t7, restarting the engine 10 is prohibited, and since no slippage occurs in the friction clutch 44, the estimated temperature of the friction clutch 44 decreases (see step ST8 of the temperature rise suppression control). When the estimated temperature drops to the operating permission temperature at time t7, restarting the engine 10 is permitted (see step ST10 of the temperature rise suppression control).

[0085] In this embodiment, the difference ΔT between the friction limit temperature (the temperature at which the frictional force on the surfaces of each friction member 61-63 begins to change) and the shutdown temperature is set to be sufficiently larger than the maximum rise in the estimated temperature of the friction clutch 44 per unit time. Therefore, it is possible to reliably prevent the estimated temperature of the friction clutch 44 from reaching the friction limit temperature.

[0086] <Effects> As described above, in this embodiment, the minimum torque at which the friction clutch 44 slips is set lower than the torque at which the fragile part 35 breaks. Therefore, the friction clutch 44 slips before the fragile part 35 breaks, interrupting the transmission of rotation from the engine 10 to the auger claw 34. This allows the transmission of rotation from the engine 10 to the auger claw 34 to be interrupted without damaging any parts, thus reducing the burden on the worker that would otherwise be incurred by replacing the damaged fragile part 35.

[0087] On the other hand, if the friction clutch 44 slips frequently, it can overheat, causing the friction force on the surfaces of the components of the friction clutch 44 (each friction member 61-63) to change. When this happens, the friction clutch 44 may malfunction or its operation may be delayed. Therefore, the control device 74 controls the operation of the engine 10 based on the estimated temperature of the friction clutch 44. This suppresses changes in the friction force on the surfaces of the components of the friction clutch 44 due to overheating, thereby improving the stability of the friction clutch 44's operation.

[0088] <Other variations> In the above embodiment, the temperature rise map M1 (an example of a temperature change map) defines only the relationship between the number of free rotations of the friction clutch 44 and the temperature rise of the friction clutch 44. On the other hand, in other embodiments, the temperature change map may define not only the relationship between the number of free rotations of the friction clutch 44 and the temperature rise of the friction clutch 44, but also the relationship between the number of free rotations of the friction clutch 44 and the temperature decrease of the friction clutch 44. In this case, the temperature decrease map M2 may be omitted.

[0089] In the above embodiment, the engine 10 is used as the drive source for rotating the auger claws 34. On the other hand, in other embodiments, an electric motor may be used as the drive source for rotating the auger claws 34, or both the engine 10 and the electric motor may be used.

[0090] In the above embodiment, a drive motor 14 is used as the drive source for driving the crawler belts 17 of each drive device 4. On the other hand, in other embodiments, an internal combustion engine may be used as the drive source for driving the crawler belts 17 of each drive device 4, or both an internal combustion engine and a drive motor 14 may be used.

[0091] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to Figures 8 and 9. Note that, aside from the temperature rise suppression control performed by the control device 74, the second embodiment is the same as the first embodiment described above, and therefore will not be explained further.

[0092] <Temperature rise suppression control> Referring to Figure 8, when the temperature rise suppression control is started, the control device 74 determines whether or not to detect slippage of the friction clutch 44 based on the drive speed output from the drive speed detection unit 71 and the work speed output from the work speed detection unit 72 (step ST11). For example, the control device 74 detects slippage of the friction clutch 44 if there is a difference of a predetermined value or more between the aforementioned driven speed calculated based on the drive speed and the work speed.

[0093] If the friction clutch 44 does not slip (step ST11: No), the control device 74 performs a temperature estimation process (details described later) (step ST12), and then returns to step ST11 to determine again whether or not to detect the slippage of the friction clutch 44.

[0094] On the other hand, if slippage of the friction clutch 44 is detected (step ST11: Yes), the control device 74 performs an operation stop process (step ST13). In the operation stop process, the control device 74 outputs an operation stop signal to the ignition device 12, thereby stopping the ignition of the air-fuel mixture by the ignition device 12. As a result, the control device 74 stops the operation of the engine 10 and cuts off the power.

[0095] Next, the control device 74 calculates the temperature rise of the friction clutch 44 by referring to the temperature rise map M1 based on the number of free rotations of the friction clutch 44. Then, the control device 74 updates the estimated temperature of the friction clutch 44 by adding the calculated temperature rise to the current estimated temperature of the friction clutch 44 (step ST14).

[0096] Next, the control device 74 performs temperature estimation processing (step ST15). Furthermore, the control device 74 determines whether the operator has instructed the engine 10 to restart based on the operator's input to the input device 21 (step ST16). If the operator has not instructed the engine 10 to restart (step ST16: No), the control device 74 returns to step ST15 and performs the temperature estimation processing again.

[0097] On the other hand, if the operator instructs the engine 10 to be restarted (step ST16: Yes), the control device 74 determines whether the estimated temperature of the friction clutch 44 is below the predetermined operating permission temperature (step ST17). If the estimated temperature of the friction clutch 44 exceeds the operating permission temperature (step ST17: No), the control device 74 prohibits the restart of the engine 10 (step ST18) and returns to step ST15 to perform the temperature estimation process again.

[0098] On the other hand, if the estimated temperature of the friction clutch 44 is below the operating permission temperature (step ST17: Yes), the control device 74 permits the restart of the engine 10 (step ST19) and terminates the temperature rise suppression control.

[0099] <Temperature estimation process> Next, the temperature estimation process described above (steps ST12 and ST15) will be explained.

[0100] Referring to Figure 9, when the temperature estimation process is started, the control device 74 calculates the temperature drop of the friction clutch 44 by referring to the temperature drop map M2 based on the length of the idle stop period. Next, the control device 74 updates the estimated temperature of the friction clutch 44 by subtracting the calculated temperature drop of the friction clutch 44 from the current estimated temperature of the friction clutch 44 (step ST21).

[0101] Next, the control device 74 determines whether the estimated temperature of the friction clutch 44 is higher than the ambient temperature (step ST22). If the estimated temperature of the friction clutch 44 is higher than the ambient temperature (step ST22: Yes), the control device 74 returns to the temperature rise suppression control while maintaining the current estimated temperature of the friction clutch 44 and executes step ST11 or ST16.

[0102] On the other hand, if the estimated temperature of the friction clutch 44 is below the ambient temperature (step ST22: No), the control device 74 sets the estimated temperature of the friction clutch 44 to the ambient temperature (step ST23), then returns to the temperature rise suppression control and executes step ST11 or ST16.

[0103] <Effects> In the second embodiment, when the control device 74 detects slippage of the friction clutch 44, it executes an operation stop process to stop the operation of the engine 10, and after executing the operation stop process, it prohibits restarting the engine 10 until the estimated temperature of the friction clutch 44 drops to the operating permission temperature. This makes it possible to more effectively suppress overheating of the friction clutch 44. As a result, the stability of the operation of the friction clutch 44 can be further improved.

[0104] This concludes the description of specific embodiments, but the present invention is not limited to the above embodiments or modifications and can be broadly modified and implemented. [Explanation of Symbols]

[0105] 1: Snowblower 10: Engine (an example of a power source) 34: Auger claws (an example of a working part) 43: Working rotation axis 44: Friction clutch 71: Drive speed detection unit 72: Working rotation speed detection unit 73: Output device 74: Control device M1: Temperature rise map (an example of a temperature change map) M2: Temperature drop map P: Rotational transmission path

Claims

1. The work department that carries out snow removal work, A drive source for rotating the aforementioned work section, A friction clutch is provided in the rotational transmission path from the drive source to the work unit, which slips when a torque exceeding a predetermined value is applied, thereby interrupting the transmission of rotation from the drive source to the work unit. The system includes a control device that controls the operation of the drive source based on the estimated temperature of the friction clutch, The control device is a snowblower that, when the estimated temperature of the friction clutch reaches a predetermined operating stop temperature, executes an operation stop process to stop the operation of the drive source.

2. The snowblower according to claim 1, wherein the control device stores a temperature change map that defines the relationship between the number of free rotations of the friction clutch per unit time and the amount of temperature change of the friction clutch per unit time, and calculates the estimated temperature of the friction clutch based on the temperature change map.

3. A drive speed detection unit that detects the drive speed, which is the number of rotations of the drive source per unit time, A working rotating shaft that transmits the rotation of the friction clutch to the working part, The system further includes a work rotation speed detection unit that detects the work rotation speed, which is the number of rotations of the work rotation axis per unit time, The snowblower according to claim 2, wherein the control device calculates the number of free rotations of the friction clutch per unit time based on the drive rotation speed and the working rotation speed, and calculates the estimated temperature of the friction clutch by referring to the temperature change map based on the number of free rotations of the friction clutch per unit time.

4. The snowblower according to claim 1, wherein the control device sets the operating stop temperature based on the rotational speed of the drive source per unit time at the start of free rotation of the friction clutch.

5. The snowblower according to claim 1 or 4, wherein the control device, after executing the operation stop process, prohibits the restart of the drive source until the estimated temperature of the friction clutch drops to an operating permit temperature lower than the operation stop temperature.

6. A work unit for performing snow removal work, A drive source for rotating the aforementioned work section, A friction clutch is provided in the rotational transmission path from the drive source to the work unit, which slips when a torque exceeding a predetermined value is applied, thereby interrupting the transmission of rotation from the drive source to the work unit. The system includes a control device that controls the operation of the drive source based on the estimated temperature of the friction clutch, The control device, upon detecting slippage of the friction clutch, executes an operation stop process to stop the operation of the drive source, and after executing the operation stop process, prohibits the restart of the drive source until the estimated temperature of the friction clutch drops to a predetermined operating permit temperature for the snowblower.

7. The snowblower according to claim 5 or 6, wherein the control device stores a temperature drop map that defines the relationship between the length of the free-spinning stop period, which is the period during which the free-spinning of the friction clutch is stopped, and the temperature drop of the friction clutch, and calculates the estimated temperature of the friction clutch based on the temperature drop map while the restart of the drive source is prohibited.

8. It is further equipped with an output device that outputs information to the worker, The snowblower according to any one of claims 1, 4 to 7, wherein the control device outputs warning information to the output device when the operation stop process is performed a predetermined number of times or more within a predetermined time.

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