Lawn mower

Abstract

To reduce engine load more effectively. [Solution] The self-propelled lawnmower 1 comprises a mowing unit 30 having a cutting blade 31 driven by an engine 32, a driving unit 20 that moves using the output of a motor 22, an engine control unit 12 that controls the rotational speed of the engine 32, and a driving control unit 11 that controls the driving speed of the driving unit 20. The driving control unit 11 slows down the driving speed when the engine rotational speed decreases. The engine control unit 12 slows down the target engine rotational speed when the engine rotational speed decreases.

Description

Technical Field

[0001] The present invention relates to a self-propelled lawn mower.

Background Art

[0002] For example, Patent Document 1 describes a self-propelled lawn mower that can travel and mow grass by remote operation by an operator. This lawn mower includes a mowing unit having a mowing blade and a traveling unit for traveling the lawn mower. This lawn mower drives the mowing blade of the mowing unit and drives the traveling unit by the driving force of the mounted engine. Further, when the load on the engine that drives the mowing unit and the traveling unit increases, this lawn mower prevents engine stall by reducing the traveling speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, a lawn mower that drives the mowing blade of the mowing unit by an engine and drives the traveling unit by a motor to travel can be considered. In such a lawn mower, even if the traveling speed is reduced as the load on the engine increases, the load on the engine may not be appropriately reduced.

[0005] Therefore, an object of the present invention is to provide a lawn mower capable of more appropriately reducing the load on the engine of the mowing unit.

Means for Solving the Problems

[0006] The grass trimmer according to the present invention is [1] "a self-propelled grass trimmer (1), comprising: a grass trimming unit (30) having an engine (32) and a cutting blade (31) driven by the engine (32); a driving unit (20) having a motor (22) and driving by the output of the motor (22); an engine control unit (12) that controls the engine rotation speed of the engine (32); and a driving control unit (11) that controls the driving speed of the driving unit (20), wherein the driving control unit (11) slows down the driving speed when the engine rotation speed decreases compared to before the engine rotation speed decreased, and the engine control unit (12) slows down the target engine rotation speed of the engine (32) when the engine rotation speed decreases compared to before the engine rotation speed decreased."

[0007] In this lawnmower (1), if the engine rotation speed decreases due to an increased load on the grass cutting unit (30), in addition to slowing down the travel speed, the target engine rotation speed can also be slowed down. As a result, the lawnmower (1) can more appropriately reduce the load on the engine (32) of the grass cutting unit (30), thereby suppressing engine (32) failure.

[0008] The above-mentioned lawnmower may also be [2] "the lawnmower (1) described in [1] above, wherein the travel control unit (11) slows down the travel speed compared to before the engine speed fell below the first threshold when the engine speed decreases to below a first threshold, and the engine control unit (12) slows down the target engine speed compared to before the engine speed fell below the second threshold when the engine speed decreases to below a second threshold which is smaller than the first threshold."

[0009] For example, slowing down the travel speed may reduce the load on the engine (32) of the grass cutting unit (30), causing the engine speed to return to its original state. In this case, it is considered unnecessary to slow down the target engine speed. Therefore, the grass cutter (1) slows down the target engine speed only when the engine speed decreases further (below the second threshold) after the travel speed has decreased due to the engine speed reduction. This allows the grass cutter (1) to control the target engine speed more appropriately.

[0010] The above-mentioned lawnmower may also be the lawnmower (1) described in [1] or [2] above, wherein the travel control unit (11) slows down the travel speed when the load on the motor (22) is high compared to when the load on the motor (22) is low.

[0011] In this case, the lawnmower (1) can control its travel speed while also taking into account the load on the motor (22). This allows the lawnmower (1) to suppress failures of the motor (22) in addition to the engine (32).

[0012] The above-mentioned lawnmower may also be the lawnmower (1) described in [3] above, wherein the travel control unit (11) calculates the travel speed based on the engine rotation speed and the travel speed based on the load of the motor (22), and controls the travel of the travel unit (20) based on the slower of the travel speeds.

[0013] In this case, the lawnmower (1) can control its travel speed by selecting the more appropriate option from the travel speed based on the engine rotation speed and the travel speed based on the load of the motor (22), from the viewpoint of suppressing failure of the engine (32) and the motor (22).

[0014] The above-mentioned lawnmower may also be the lawnmower (1) described in [3] or [4] above, wherein the travel control unit (11) uses the current value flowing through the motor (22) or the temperature of the motor (22) as the load of the motor (22), and determines that the load of the motor (22) is higher when the current value is high compared to when the current value is low, or determines that the load of the motor (22) is higher when the temperature is high compared to when the temperature is low.

[0015] In this case, the lawnmower (1) can more appropriately determine the load on the motor (22) based on the current flowing through the motor (22) or the temperature of the motor (22), and control the travel speed so as to reduce the load on the motor (22). [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a lawnmower that can more appropriately reduce the load on the engine of the lawnmower unit. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1(a) is a front view showing a schematic configuration of a lawnmower according to the embodiment. Figure 1(b) is a top view showing a schematic configuration of a lawnmower according to the embodiment. [Figure 2] Figure 2 is a block diagram showing the functional configuration of a lawnmower. [Figure 3] Figure 3 shows an example of a load control map stored in the memory unit. [Figure 4] Figure 4 is a flowchart showing the flow of the load control process. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described below with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0019] As shown in FIGS. 1(a) and 1(b), the lawn mower 1 includes tires 21 and a cutting blade 31. In this embodiment, four tires 21 are provided. The lawn mower 1 is a self-propelled device that can travel by rotating the tires 21. The cutting blade 31 is provided on the lower surface of the lawn mower 1. The cutting blade 31 cuts grass and the like growing on the ground by being rotated. The lawn mower 1 is controlled to travel and cut grass, for example, by remote operation by an operator.

[0020] More specifically, as shown in FIG. 2, the lawn mower 1 includes an ECU (Electronic Control Unit) 10, a traveling unit 20, and a grass cutting unit 30. The ECU 10 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). In the ECU 10, various functions are realized by, for example, the CPU executing a program stored in the ROM or the RAM.

[0021] The traveling unit 20 is a mechanism for causing the lawn mower 1 to travel. The traveling unit 20 includes tires 21 and a motor 22. The motor 22 rotates the tires 21. The rotational speed (number of rotations per unit time) of the motor 22 is controlled by the ECU 10. Thus, the traveling unit 20 travels by the output of the motor 22. As described above, four tires 21 are provided in this embodiment. Note that the traveling unit 20 is not limited to including the tires 21. The traveling unit 20 may be configured to rotationally drive, for example, crawlers instead of the tires 21. Further, the traveling unit 20 includes a steering unit that controls steering (the direction of the tires 21), a battery that supplies power to the motor 22, and the like.

[0022] The grass cutting unit 30 is a mechanism for cutting grass. The grass cutting unit 30 includes a cutting blade 31, an engine 32, and a throttle control motor 33. The cutting blade 31 is driven by the engine 32. The throttle control motor 33 controls the opening degree of the throttle of the engine 32. The throttle control motor 33 is controlled by the ECU 10.

[0023] In addition, the lawn mower 1 includes a wireless communication unit and the like that receives a remote operation signal from an operator.

[0024] Functionally, the ECU 10 includes a travel control unit 11, an engine control unit 12, and a map storage unit 13. Here, engine rotation information and motor load information are input to the ECU 10. The engine rotation information is information indicating the current (actual) engine rotation speed of the engine 32. For example, the engine rotation information may be information on the rotation pulses of the engine 32. For example, when the density of the grass cut by the grass cutting unit 30 is high or the grass gets entangled with the cutting blade 31 (the axis of the cutting blade 31), the load on the engine 32 may increase. In this case, the rotation speed of the engine 32 decreases. Also, the rotation speed of the engine 32 slows down as the load on the engine 32 increases. Thus, the engine rotation information represents the current (actual) load on the engine 32.

[0025] The motor load information is information indicating the load on the rotation of the motor 22. The motor load information includes, as the load on the motor 22, the current current value flowing through the motor 22 and the current temperature of the motor 22. The current current value flowing through the motor 22 may be a value measured by a current sensor or the like. The current temperature of the motor 22 may be a value measured by a temperature sensor. For example, when the density or height of the grass is high or the grass gets entangled with the tire 21 (the axis of the tire 21), the load on the motor 22 may increase. In this case, the current value flowing through the motor 22 increases and the temperature of the motor 22 increases. Thus, the motor load information represents the current load on the motor 22.

[0026] The travel control unit 11 controls the travel speed of the travel unit 20. Here, the travel control unit 11 controls the rotational speed of the motor 22 by controlling the power supplied to the motor 22, thereby controlling the travel speed of the travel unit 20. The travel speed controlled by the travel control unit 11 is the maximum speed of the travel unit 20. The lawnmower 1 (travel unit 20) can travel within a range of the travel speed (maximum speed) controlled by the travel control unit 11, based on the operator's operation.

[0027] The driving control unit 11 controls the driving speed of the driving unit 20 based on engine rotation information. Here, if the engine rotation speed decreases, the driving control unit 11 slows down the driving speed compared to before the engine rotation speed decreased. For example, the driving control unit 11 uses an engine rotation speed threshold, and when the engine rotation speed based on the engine rotation information falls below a preset threshold, it slows down the driving speed compared to before the engine rotation speed fell below the threshold. The driving control unit 11 may set multiple thresholds. In other words, the driving control unit 11 may gradually slow down the driving speed each time the engine rotation speed falls below each threshold.

[0028] Furthermore, when the engine speed decreases, the drive control unit 11 only needs to slow down the drive speed of the drive unit 20 to a level at least lower than that of the normal engine speed. In other words, when the engine speed decreases, the drive control unit 11 is not limited to gradually slowing down the drive speed as the engine speed decreases. For example, after the drive speed decreases and the drive speed is slowed down, the drive control unit 11 may increase the drive speed within a range of drive speeds that are slower than those of the normal engine speed.

[0029] Furthermore, the travel control unit 11 controls the travel speed of the travel unit 20 based on the motor load information. Here, the travel control unit 11 slows down the travel speed when the load on the motor 22 is high compared to when the load on the motor 22 is low. The motor load information includes the current value flowing through the motor 22 and the current temperature of the motor 22. The travel control unit 11 determines that the load on the motor 22 is high when the current value is high compared to when the current value is low. The travel control unit 11 also determines that the load on the motor 22 is high when the temperature is high compared to when the temperature is low. The travel control unit 11 determines the load on the motor 22 by combining the current value and temperature of the motor 22.

[0030] For example, the travel control unit 11 uses a threshold value for the motor 22 load, and when the load of the motor 22 based on the motor load information falls below a preset threshold, it slows down the travel speed compared to before the motor 22 load fell below the threshold. The travel control unit 11 may set multiple threshold values. In other words, the travel control unit 11 may gradually slow down the travel speed each time the load of the motor 22 falls below each threshold value.

[0031] In this way, the driving control unit 11 calculates a driving speed based on the engine rotation speed and a driving speed based on the load of the motor 22. The driving control unit 11 controls the movement of the driving unit 20 based on the slower of the two calculated driving speeds.

[0032] In this embodiment, the driving control unit 11 can calculate the driving speed of the driving unit 20 based on the current engine speed by using a load control map that associates a threshold engine speed for determining the load of the engine 32 with the vehicle speed. For example, the driving control unit 11 can use the load control map shown in Figure 3.

[0033] Here, the driving control unit 11 sets the driving speed (maximum speed) of the driving unit 20 to 4 km / h when the load on the motor 22 and / or engine 32 is not high. When the load on the motor 22 and / or engine 32 becomes high, the driving control unit 11 sets the driving speed of the driving unit 20 to a speed of less than 4 km / h. In addition, when the load on the motor 22 and engine 32 is not high, the engine control unit 12 controls the throttle control motor 33 so that the engine rotation speed of the engine 32 is 7000 rpm. In other words, the engine control unit 12 sets the target engine rotation speed of the engine 32 to 7000 rpm when it is not high.

[0034] Specifically, in the example shown in Figure 3, three thresholds are set as engine speed thresholds: a low-load threshold (first threshold), a medium-load threshold, and a high-load threshold (second threshold). As an example, 5500 rpm is set as the low-load threshold, 4500 rpm as the medium-load threshold, and 4000 rpm as the high-load threshold. The load on the engine 32 increases and the engine speed decreases in the order of low-load threshold, medium-load threshold, and high-load threshold.

[0035] For example, if the load on engine 32 increases, the engine speed will decrease below the normal engine speed (7000 rpm). When the engine speed falls below 5500 rpm, the driving control unit 11 slows the driving speed of the driving unit 20 from the normal 4 km / h to 0.5 km / h. If the engine speed then falls below 4500 rpm, the driving control unit 11 sets the driving speed of the driving unit 20 to 1.0 km / h. If the engine speed then falls below 4000 rpm, the driving control unit 11 sets the driving speed of the driving unit 20 to 1.0 km / h (and leaves it unchanged).

[0036] Thus, when the load on the engine 32 increases and the engine speed decreases from the normal state, the driving control unit 11 slows the driving speed of the driving unit 20 from the normal setting of 4 km / h to 0.5 km / h or 1.0 km / h. In the example shown in Figure 3, when the engine speed decreases below the normal state to 5500 rpm or less, the driving speed is set to 0.5 km / h, and when the engine speed decreases further to 4500 rpm or less, the driving speed is increased to 1.0 km / h. In this way, the driving control unit 11 may slightly increase the driving speed if the engine speed decreases further, as long as it is within the range of driving speeds slower than the normal state. Alternatively, the set driving speed may be set to values ​​that decrease sequentially in the order of low load threshold, medium load threshold, and high load threshold.

[0037] Furthermore, the driving control unit 11 may use a load control map similar to the load control map shown in Figure 3, in which thresholds for determining the load of the motor 22 (current threshold, temperature threshold) are associated with the vehicle speed. The driving control unit 11 may then use this load control map to calculate the driving speed of the driving unit 20 based on the load of the motor 22.

[0038] The engine control unit 12 controls the rotational speed of the engine 32. The engine control unit 12 controls the throttle control motor 33 to control the throttle opening of the engine 32. In this way, the engine control unit 12 can control the rotational speed of the engine 32. The engine control unit 12 controls the throttle control motor 33 so that the rotational speed of the engine 32 reaches a set target engine rotational speed.

[0039] The engine control unit 12 controls the rotational speed of the engine 32 based on engine rotation information. Here, if the engine rotation speed decreases, the engine control unit 12 slows down the target engine rotation speed of the engine 32 compared to before the engine rotation speed decreased. For example, the engine control unit 12 uses an engine rotation speed threshold, and when the engine rotation speed based on the engine rotation information falls below a preset threshold, it slows down the target engine rotation speed compared to before the engine rotation speed fell below the threshold. The engine control unit 12 may set multiple thresholds. In other words, the engine control unit 12 may gradually slow down the target engine rotation speed each time the engine rotation speed falls below each threshold.

[0040] In this embodiment, the engine control unit 12 can calculate a target engine speed based on the current engine speed using a load control map that associates a threshold engine speed for determining the load on the engine 32 with a target engine speed. For example, the engine control unit 12 can use the load control map shown in Figure 3. As described above, in normal conditions where the load on the motor 22 and engine 32 is not high, the engine control unit 12 sets the target engine speed to 7000 rpm.

[0041] Specifically, in the example shown in Figure 3, for example, even if the engine speed drops below the normal engine speed (7000 rpm) due to an increased load on the engine 32, the target engine speed is maintained at 7000 rpm until the engine speed falls below 4000 rpm. When the engine speed falls below 4000 rpm, the engine control unit 12 reduces the target engine speed from 7000 rpm to 2000 rpm. In this way, when the load on the engine 32 increases and the engine speed drops below the normal state to 4000 rpm, the engine control unit 12 reduces the target engine speed to a lower level than the normal setting of 7000 rpm.

[0042] Furthermore, when the engine speed decreases to 5500 rpm (first threshold) or below, the driving control unit 11 slows down the driving speed compared to before the engine speed decreased to 5500 rpm or below. On the other hand, when the engine speed decreases to 4000 rpm (second threshold) or below, which is lower than 5500 rpm, the engine control unit 12 slows down the target engine speed compared to before the engine speed decreased to 4000 rpm or below. Thus, the timing at which the driving control unit 11 slows down the driving speed compared to normal and the timing at which the engine control unit 12 slows down the target engine speed compared to normal are different.

[0043] For example, if the engine speed drops below 5500 rpm and the travel speed is reduced, the engine speed may return to its normal state due to reduced resistance from the grass on the cutting blade 31 or the removal of tangled grass. Therefore, even if the travel control unit 11 reduces the travel speed when the engine speed drops below 5500 rpm, the engine control unit 12 maintains the same target engine speed as under normal conditions. Subsequently, if the engine speed does not recover and further decreases to below 4000 rpm, the engine control unit 12 slows the target engine speed down to below normal conditions.

[0044] The map storage unit 13 stores information necessary for various controls performed by the driving control unit 11 and the engine control unit 12. Specifically, the map storage unit 13 stores the load control maps used by the driving control unit 11 and the engine control unit 12.

[0045] Next, the flow of the load control process performed in the ECU 10 will be explained using the flowchart in Figure 4. The ECU 10 starts the process shown in Figure 4 when, for example, the power to the lawnmower 1 is turned ON and the engine 32 is started. Immediately after the engine 32 starts up, the travel control unit 11 sets the travel speed of the travel unit 20 to the normal travel speed (e.g., 4 km / h), and the engine control unit 12 sets the target engine rotation speed to the normal target engine rotation speed (e.g., 7000 rpm). When the process shown in Figure 4 reaches its end, the process starts again from the beginning after a predetermined time. Here, we will explain using the case where control is performed using the load control map stored in the map storage unit 13 as an example.

[0046] As shown in Figure 4, the driving control unit 11 and the engine control unit 12 acquire the current engine speed of the engine 32 based on the engine speed information input to the ECU 10 (S101). Based on the acquired engine speed, the engine control unit 12 acquires the target engine speed of the engine 32. The engine control unit 12 can acquire the target engine speed using the load control map stored in the map storage unit 13. The engine control unit 12 controls the throttle control motor 33 to achieve the acquired target engine speed (S102). If the engine speed is not below the low load threshold of the load control map (5500 rpm or less in the example shown in Figure 3), the engine control unit 12 sets the normal target engine speed (7000 rpm in this case) as the target engine speed and controls the engine to achieve that target engine speed.

[0047] Next, the driving control unit 11 acquires the driving speed V1 of the driving unit 20 based on the engine rotation speed acquired in S101 (S103). Here, the driving control unit 11 can acquire the driving speed V1 based on, for example, a load control map stored in the map storage unit 13. The driving control unit 11 also acquires the current value flowing to the motor 22 and the current temperature of the motor 22 based on the motor load information input to the ECU 10 (S104). The driving control unit 11 acquires the driving speed V2 of the driving unit 20 based on the current value and temperature of the motor 22 (S105). Here, the engine control unit 12 can acquire the driving speed V2 based on, for example, a load control map stored in the map storage unit 13.

[0048] The driving control unit 11 compares the driving speed V1 of the driving unit 20 based on the acquired engine rotation speed with the driving speed V2 of the driving unit 20 based on the current value and temperature of the motor 22 (S106). If the driving speed V1 is smaller than the driving speed V2 (S106: YES), the driving control unit 11 sets the driving speed V1 as the driving speed of the driving unit 20 (S107). On the other hand, if the driving speed V1 is not smaller than the driving speed V2 (S106: NO), the driving control unit 11 sets the driving speed V2 as the driving speed of the driving unit 20 (S108). In other words, in S106 to S108, the driving control unit 11 sets the driving speed of the driving unit 20 (upper limit of the driving speed) to be the smaller of the driving speed V1 of the driving unit 20 based on the engine rotation speed and the driving speed V2 of the driving unit 20 based on the current value and temperature of the motor 22.

[0049] As described above, in this lawnmower 1, if the engine rotation speed decreases due to an increased load on the grass cutting unit 30, in addition to slowing down the travel speed of the travel unit 20, the target engine rotation speed of the engine 32 can also be slowed down. As a result, the lawnmower 1 can more appropriately reduce the load on the engine 32 of the grass cutting unit 30, thereby suppressing engine failure.

[0050] For example, if the travel speed of the travel unit 20 is reduced, the load on the engine 32 of the grass cutting unit 30 decreases, and the engine rotation speed may return to its original state. In this case, it is considered unnecessary to reduce the target engine rotation speed. Therefore, the grass cutter 1 reduces the target engine rotation speed only when the engine rotation speed decreases further (when it falls below the high load threshold) after the travel speed has decreased due to the engine rotation speed. This allows the grass cutter 1 to control the target engine rotation speed more appropriately.

[0051] In the lawnmower 1, the travel control unit 11 slows down the travel speed when the load on the motor 22 is high compared to when the load on the motor 22 is low. In this case, the lawnmower 1 can control the travel speed while taking the load on the motor 22 into consideration. As a result, the lawnmower 1 can suppress failures of the motor 22 in addition to the engine 32.

[0052] The travel control unit 11 calculates a travel speed V1 based on the engine rotation speed and a travel speed V2 based on the load of the motor 22, and controls the travel of the travel unit 20 based on the slower travel speed. In this case, the lawnmower 1 can control the travel speed by selecting the more appropriate of the travel speed V1 based on the engine rotation speed and the travel speed V2 based on the load of the motor 22, from the viewpoint of suppressing failure of the engine 32 and the motor 22.

[0053] The travel control unit 11 determines that the load on the motor 22 is higher when the current flowing through it is high compared to when the current is low. The travel control unit 11 also determines that the load on the motor 22 is higher when the temperature of the motor 22 is high compared to when the temperature is low. In this case, the lawnmower 1 can more appropriately determine the load on the motor 22 based on the current flowing through it and the temperature of the motor 22, and control the travel speed to reduce the load on the motor 22.

[0054] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the driving control unit 11 is not limited to determining the load of the motor 22 based on both the current value flowing through the motor 22 and the temperature of the motor 22. The driving control unit 11 may determine the load of the motor 22 using only one of the current value flowing through the motor 22 or the temperature of the motor 22. [Explanation of symbols]

[0055] 1...grass trimmer, 11...travel control unit, 12...engine control unit, 20...travel unit, 22...motor, 30...grass trimming unit. 31...cutting blade, 32...engine.

Claims

1. A self-propelled lawnmower (1), A grass cutting unit (30) having an engine (32) and a cutting blade (31) driven by the engine (32), A traveling unit (20) having a motor (22) and moving by the output of the motor (22), The engine control unit (12) controls the rotational speed of the engine (32), A travel control unit (11) controls the travel speed of the travel unit (20), Equipped with, When the engine speed decreases, the aforementioned driving control unit (11) slows down the driving speed compared to before the engine speed decreased. The engine control unit (12) of the lawnmower (1) slows down the target engine speed of the engine (32) to the level before the engine speed decreased when the engine speed decreases.

2. When the engine speed decreases to below a first threshold, the driving control unit (11) slows down the driving speed compared to before the engine speed decreased to below the first threshold. The lawnmower (1) according to claim 1, wherein when the engine rotation speed decreases to a second threshold less than the first threshold, the engine control unit (12) slows down the target engine rotation speed compared to before the engine rotation speed fell below the second threshold.

3. The lawnmower (1) according to claim 1 or 2, wherein the travel control unit (11) slows down the travel speed when the load on the motor (22) is high compared to when the load on the motor (22) is low.

4. The lawnmower (1) according to claim 3, wherein the travel control unit (11) calculates the travel speed based on the engine rotation speed and the travel speed based on the load of the motor (22), and controls the travel of the travel unit (20) based on the slower of the travel speeds.

5. The lawnmower (1) according to claim 3, wherein the driving control unit (11) uses the current value flowing through the motor (22) or the temperature of the motor (22) as the load of the motor (22), and determines that if the current value is high, the load on the motor (22) is higher than when the current value is low, or determines that if the temperature is high, the load on the motor (22) is higher than when the temperature is low.

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