Patent Publication Number: US-2021161064-A1

Title: Working machine

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority to and the benefit of PCT/JP2018/031395 filed on Aug. 24, 2018, the entire disclosure of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a working machine that performs a work mainly based on power of a battery. 
     BACKGROUND ART 
     Some of working machines include a batter such as a lithium ion battery (see PTL 1). Since a user may not use a working machine for a relatively long period, a battery down may occur. Therefore, the user may not be able to use the working machine at a desired timing. As a measure against the battery down, it is considered to detach the battery in advance from the working machine. However, it is often complicated for the user to attach/detach the battery, which may increase the load on the user. 
     CITATION LIST 
     Patent Literature 
     PTL 1: U.S. Pat. No. 9,127,658 
     SUMMARY OF INVENTION 
     Technical Problem 
     The object of the present invention can relatively easily prevent a battery down of a working machine while improving the usability of the working machine. 
     Solution to Problem 
     The first aspect of the present invention is related to a working machine, and the working machine is a working machine with a working unit configured to perform a work, comprising a battery and a control unit, wherein the control unit has, as operation modes, a normal mode in which the working unit is operable based on power of the battery, and a power saving mode in which the working unit is made inoperable by limiting some of functions, as compared with the normal mode, and power consumption of the battery is suppressed, as compared with the normal mode. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to appropriately prevent the battery down of a working machine. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view for explaining an example of the arrangement of a working machine; 
         FIG. 2  is a block diagram for explaining an example of the arrangement of the working machine; 
         FIG. 3  is a block diagram for explaining an example of the arrangement of a control unit; 
         FIG. 4  is a view for explaining an example of the operation mode of the control unit; 
         FIG. 5A  is a flowchart for explaining an example of a control form by the control unit; and 
         FIG. 5B  is a flowchart for explaining an example of the control form by the control unit. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will now be described with reference to the accompanying drawings. Note that the drawings are schematic views showing a structure or an arrangement according to the embodiment, and the dimensions of members shown in the drawings do not necessarily reflect real dimensions. The same reference numerals denote the same elements in the drawing, and a description of repetitive contents will be omitted in this specification. 
       FIG. 1  is a perspective view of a working machine  1  according to an embodiment.  FIG. 2  is a block diagram showing an example of the arrangement of the working machine  1 . The working machine  1  includes a working unit  11 , a traveling unit  12 , a control unit  13 , and a battery  14  in a main body portion  10 . The working machine  1  further includes an operation unit  15  in an extended portion  18  extended from the main body portion  10  to the rear and upper sides. 
     In this embodiment, the working unit  11  includes a working mechanism  111 , a power unit  112 , a starter  113 , and a grass bag  114 . The working mechanism  111  is a mechanism for implementing a predetermined work. In this embodiment, the working mechanism  111  is a disc-shaped blade (see  FIG. 1 ) rotatably arranged in the lower portion of the main body portion  10 , thereby making it possible to perform lawn mowing as an example of a work (the working machine  1  can also be called a lawn mower). In this embodiment, the power unit  112  is an internal combustion engine (engine), which serves as a power source that generates power (rotation) to drive the working mechanism  111  (see  FIG. 2 ). A transmission such as HST (Hydro-Static Transmission) may be provided as part of the power unit  112 /in addition to the power unit  112 . The starter  113  starts the power unit  112  in response to a signal from the control unit  13  (to be described later) (see  FIG. 2 ). The grass bag  114  is a storage portion that stores a lawn mowed by the working mechanism  111 , and is detachably arranged in the rear portion of the main body portion  10  (see  FIG. 1 ). With this arrangement, the working unit  11  can execute a work in a predetermined work region. 
     The traveling unit  12  includes a pair of front wheels and a pair of rear wheels each rotatably arranged in the lower portion of the main body portion  10 , thereby supporting the main body portion  10  (see  FIG. 1 ). The traveling unit  12  can make the working machine  1  travel by receiving power from the power unit  112 . An end portion of the extended portion  18  is formed as a grip portion (handle bar)  181  like a bar (see  FIG. 1 ), and the user can perform a work while pushing the working machine  1  by gripping the grip portion  181 . The working machine  1  can also be called a walking type working machine, a walking type lawn mower, or the like. 
     The operation unit  15  accepts, from the user, an input operation of controlling the operating state of the working unit  11 . The operation unit  15  is provided at a position where the user readily operates it. In this embodiment, the operation unit  15  includes a lever type operator  151  and a button type operator  152 , both of which are arranged in the extended portion  18 , particularly, in the grip portion  181  or its periphery (see  FIG. 1 ). In this embodiment, the lever type operator  151  is pivotably juxtaposed with the bar-like grip portion  181 . The user inputs an operation by making the lever type operator  151  pivot. In this embodiment, the button type operator  152  is a push button type switch of an automatic return type arranged in one end portion of the grip portion  181 . The user inputs an operation by pressing the button type operator  152 . Note that the input operation to the operation unit  15  by the user is transmitted as an electrical signal to the control unit  13  (to be described later) via a cable, a wire, or the like. 
     Although details will be described later, this embodiment assumes that the working unit  11  is set in the operating state when the user operates the button type operator  152  while operating the lever type operator  151 . That is, even if the user presses the button type operator  152  without making the lever type operator  151  pivot, the working unit  11  is not set in the operating state. The operation form in which the user operates the button type operator  152  while operating the lever type operator  151  is also called a two-step operation or the like, and is advantageous in ensuring safety when operating the working unit  11 . 
     After the working unit  11  is set in the operating state, the user can perform a work using the working unit  11  in the operating state by making the working machine  1  travel while maintaining the lever type operator  151  in an operated state (a state in which the lever type operator  151  is made to pivot). Furthermore, the user can set the working unit  11  in a stop state at a desired timing by releasing the operation of the lever type operator  151  (for example, by releasing the hand from the lever type operator  151 ). In this embodiment, assume that in the stop state of the working unit  11 , the power unit  112  is in a stop state and the working mechanism  111  is also in a stop state. 
     As another embodiment, the working mechanism  111  and the power unit  112  can mechanically be coupled by a clutch, and coupling/releasing of the clutch may be controllable by the lever type operator  151 . For example, the clutch is set in a coupled state by operating the lever type operator  151 , and is set in a released state by releasing the operation. In this case, in accordance with releasing of the operation of the lever type operator  151 , transmission of power of the power unit  112  to the working mechanism  111  can be interrupted without stopping the power unit  112 . 
     The operation unit  15  can further include another operator. Examples of the other operator are an operator for adjusting the height of the disc-shaped blade as the working mechanism  111 , an operator for changing the output level of the power unit  112 , and an operator for breaking the traveling unit  12 . 
     The control unit (control apparatus)  13  is an electric component that receives power from the battery  14 , and performs control of each element of the working machine  1 , for example, driving control of the working unit  11  based on the input operation to the operation unit  15  by the user. The control unit  13  can include, for example, a wiring portion for implementing electrical connection between the elements in addition to one or more mount substrates on which electronic components are implemented. Examples of the electronic components are semiconductor devices such as an ASIC (Application Specific Integrated Circuit) and PLD (Programmable Logic Device). Examples of the wiring portion are a wire harness, FPC (Flexible Printed Circuit), and CoF (Chip on Film). 
     Although details will be described later, in this embodiment, the control unit  13  includes a signal processing circuit unit  130 , detection circuit units  131  and  132 , a starting circuit unit  133 , and a power supply circuit unit  134  (see  FIG. 2 ). Note that in this specification, a circuit unit indicates an element to which one or more passive elements or active elements are electrically connected to be able to implement a predetermined function. Thus, each circuit unit may be separated into some parts and provided or may be provided close to another circuit unit. 
     The signal processing circuit unit  130  is an MCU (Micro Controller Unit) or MPU (Micro Processing Unit) that performs signal processing for system control of the overall working machine  1  based on the power of the battery  14 . As the signal processing circuit unit  130 , for example, a predetermined battery management IC (Integrated Circuit) such as RAJ240100 (Renesas Electronics) can be used. 
     As the detection circuit unit  131 , one or more input circuit ICs that make it possible to detect an operation input to the lever type operator  151  can be used. The detection circuit unit  131  supplies, using a voltage V 1 ′, an electrical signal, indicating that an operation has been input to the lever type operator  151 , as a detection signal De 1  to the signal processing circuit unit  130 . 
     As the detection circuit unit  132 , one or more input circuit ICs that make it possible to detect an operation input to the button type operator  152  can be used. The detection circuit unit  132  supplies, using a voltage V 2  different from the voltage V 1 ′, an electrical signal, indicating that an operation has been input to the button type operator  152 , as a detection signal De 2  to the signal processing circuit unit  130 . 
     In response to the reception of the detection signals De 1  and De 2 , the signal processing circuit unit  130  outputs a start signal St 1  to the starting circuit unit  133 , thereby making the power unit  112  start using the starter  113 . The power of the power unit  112  is transmitted to the working mechanism  111 , and the working mechanism  111  is set in a driving state, that is, the working unit  11  is set in the operating state. 
     As the power supply circuit unit  134 , a power supply IC including a DC-DC converter can be used. The power supply circuit unit  134  generates one or more power supply voltages based on a voltage V 1  of the battery  14 , and supplies them to the signal processing circuit unit  130 . For example, the power supply circuit unit  134  is configured to supply the voltage V 1 ′ to the detection circuit unit  131 . The voltage V 1 ′ may be equal to the voltage V 1  or may have a different value. In this embodiment, assume that while the remaining amount of the battery  14  is sufficient, the voltage V 1 ′ is continuously supplied to the detection circuit unit  131 . Note that if the voltage V 1 ′ is equal to the voltage V 1 , the voltage V 1  may be supplied directly from the battery  14  to the detection circuit unit  131 . To simplify the description, a representation “voltage (power supply voltage)” has been used. However, a representation “power” may be used in consideration of a current component such as a driving current. 
     Assume that the signal processing circuit unit  130  incorporates a regulator, can generate the voltage V 2  based on the voltage V 1 ′, and can supply power P 2  to the detection circuit unit  132 . In other words, the detection circuit unit  132  is arranged electrically independent of the detection circuit unit  131 . Although details will be described later, the control unit  13  has a normal mode and a power saving mode as operation modes. In the normal mode, the voltage V 2  is supplied to the detection circuit unit  132 . In the power saving mode, supply of the voltage V 2  to the detection circuit unit  132  is suppressed. 
     As the battery  14 , a chargeable secondary battery such as a lithium ion battery or nickel hydrogen battery can be used. Although a detailed description will be omitted in this specification, the control unit  13  can also charge the battery  14  using power generated by regenerative braking of the power unit  112 . 
       FIG. 3  is a block diagram showing details of the arrangement of the control unit  13 . The signal processing circuit unit  130  includes a calculation unit  1301 , a storage unit  1302 , and an interface unit  1303 . The calculation unit  1301  and the storage unit  1302  perform signal processing based on a predetermined program. The interface unit  1303  includes a plurality of portions corresponding to a plurality of elements that exchange a signal or voltage with the signal processing circuit unit  130 , and in this embodiment, includes portions  1303 A to  1303 D. The portion  1303 A receives, as an input to the signal processing circuit unit  130 , the signal De 1  from the detection circuit unit  131 . The portion  1303 B outputs the voltage V 2  to the detection circuit unit  132 , and receives, as an input to the signal processing circuit unit  130 , the signal De 2  from the detection circuit unit  132 . The portion  1303 C outputs the signal SU to the starting circuit unit  133 . The portion  1303 D receives, as an input to the signal processing circuit unit  130 , the voltage V 1  from the power supply circuit unit  134 . 
     The detection circuit unit  131  includes an input terminal IN 1 , an output terminal OUT 1 , a rectifier element D 11 , a transistor T 11 , resistance elements R 11 , R 12 , and R 13 , and a capacitor C 11 . The input terminal IN 1  is connected to the cathode of the rectifier element D 11 . In this embodiment, as the transistor T 11 , a PNP type bipolar transistor is used. The emitter of the transistor T 11  is connected to the voltage V 1 ′, and the collector of the transistor T 11  is connected to the output terminal OUT 1 . One end of the resistance element R 11  is connected to the anode of the rectifier element D 11 , and the other end of the resistance element R 11  is connected to the base of the transistor T 11 . One end of the resistance element R 12  is connected to the anode of the rectifier element D 11 , and the other end of the resistance element R 12  is connected to the voltage V 1 ′. One end of the resistance element R 13  is connected to the output terminal OUT 1 , and the other end of the resistance element R 13  is grounded. One end of the capacitor C 11  is connected to the voltage V 1 ′, and the other end of the capacitor C 11  is connected to the base of the transistor T 11 . 
     With this arrangement, the detection circuit unit  131  outputs, using the voltage V 1 ′, the detection signal De 1  indicating that an operation has been input to the lever type operator  151 . The signal processing circuit unit  130  receives the detection signal De 1  by the portion  1303 A of the interface unit  1303 . 
     The detection circuit unit  132  includes input terminals IN 2  and IN 2 ′, output terminals OUT 2  and OUT 2 ′, a rectifier element D 21 , a transistor T 21 , resistance elements R 21 , R 22 , and R 23 , a capacitor C 21 , a starting circuit unit UN 21 , and an OR circuit unit OR 21 . In the detection circuit unit  132 , the voltage V 2  is used instead of the voltage V 1 ′. 
     The input terminal IN 2 , the output terminal OUT 2 , the rectifier element D 21 , the transistor T 21 , the resistance elements R 21 , R 22 , and R 23 , and the capacitor C 21  are integrated as a normal input circuit unit  1321 , and are arranged in the same arrangement as that of the detection circuit unit  131 . That is, the input terminal IN 2 , the output terminal OUT 2 , the rectifier element D 21 , the transistor T 21 , the resistance elements R 21 , R 22 , and R 23 , and the capacitor C 21  correspond to the input terminal IN 1 , the output terminal OUT 1 , the rectifier element D 11 , the transistor T 11 , the resistance elements R 11 , R 12 , and R 13 , and the capacitor C 11 , respectively. 
     With this arrangement, the detection circuit unit  132  outputs, using the voltage V 2 , the detection signal De 2  indicating that an operation has been input to the button type operator  152 . The signal processing circuit unit  130  receives the detection signal De 2  by the portion  1303 B of the interface unit  1303 . 
     The input terminal INT, the output terminal OUT 2 ′, the starting circuit unit UN 21 , and the OR circuit unit OR 21  are integrated as a temporary input circuit unit  1322 , which is arranged in parallel with the normal input circuit unit  1321 . The input terminal of the starting circuit unit UN 21  is connected to the output terminal OUT 2 , and the output terminal of the starting circuit unit UN 21  is connected to one input terminal of the OR circuit unit OR 21 . The input terminal INT is an electrode electrically connectable to an external power supply (a power supply different from the battery  14 ), as needed, and is connected to the other input terminal of the OR circuit unit OR 21 . The output terminal OUT 2 ′ is connected to the output terminal of the OR circuit unit OR 21 . This makes it possible to supply, using the external power supply (without using the battery  14 ), to the signal processing circuit unit  130 , the detection signal indicating that the operation has been input to the button type operator  152 . 
     By individually providing the voltage V 1 ′ of the detection circuit unit  131  and the voltage V 2  of the detection circuit unit  132 , the working unit  11  can be operated under a condition under which each voltage is supplied. This is equivalent to making it possible to start a work when all the individual circuit units can operate normally, and it is thus possible to improve safety when the working machine  1  is used with the relatively simple arrangement. 
       FIG. 4  is a state transition diagram concerning the control unit  13 . The control unit  13  is set in the operating state based on power from the battery  14 , and has, as the operation modes, the normal mode and the power saving mode. The normal mode is a mode in which the working unit  11  is operable based on the power of the battery  14 . The power saving mode in a mode in which some of the functions of the control unit  13  are limited, as compared with the normal mode, and thus the working unit  11  is made inoperable and the power consumption of the battery  14  is suppressed, as compared with the normal mode. 
     The limitation of some functions of the control unit  13  in the power saving mode can be implemented by setting, to an inactive state, an element in the control unit  13  associated with the operation of the working unit  11 , for example, by suppressing supply of the power supply voltage to the element or limiting a bias current in the element. In the power saving mode according to this embodiment, supply of the voltage V 2  to the detection circuit unit  132  is suppressed, generation of the voltage V 2  in the signal processing circuit unit  130  is suppressed, and supply of the power supply voltage to the portions  1303 B and  1303 C of the interface unit  1303  is suppressed. Calculation processing by the calculation unit  1301  and its associated readout/write from/in the storage unit  1302  are not performed. Therefore, according to this embodiment, the maximum consumed current amount of the control unit  13  is about 5 [mA] in the normal mode but is about 50 [μA] in the power saving mode. 
     In a predetermined case, for example, a case in which power from the battery  14  is substantially zero/is not sufficient, the control unit  13  is in the stop state as a state in which all the functions are limited. The stop state is a state in which the system of the control unit  13  is down and a state in which the control unit  13  has substantially no power consumption (has a maximum consumed current amount less than 1 [μA]. Note that in correspondence with the stop state, the normal mode may be called an active state or the like, and the power saving mode may be called a partially active state, a sleep state, or the like. 
     In this embodiment, the control unit  13  in the stop state shifts to the normal mode when a condition A 11  is satisfied. As an example of the condition A 11 , (i) in a state in which the remaining amount of the battery  14  is larger than a reference value, (ii) a state in which the lever type operator  151  is operated is set. When the control unit  13  is set in the normal mode, the signal processing circuit unit  130  generates the voltage V 2 , and supplies it to the detection circuit unit  132 . This allows the detection circuit unit  132  to detect an input operation to the button type operator  152  by the user. When the user operates the button type operator  152 , the control unit  13  sets the working unit  11  in the operating state. 
     Furthermore, the control unit  13  in the normal mode shifts to the power saving mode when a condition A 12  is satisfied. As an example of the condition A 12 , (i) in a state in which the remaining amount of the battery  14  is larger than the reference value, (ii) a state in which the operation of the lever type operator  151  is released is set. When the control unit  13  is set in the power saving mode, the signal processing circuit unit  130  suppresses supply of the voltage V 2  to the detection circuit unit  132 . This disables the detection circuit unit  132  from detecting the input operation to the button type operator  152  by the user. 
     Furthermore, the control unit  13  in the power saving mode is set in the stop state when a condition A 13  is satisfied. As an example of the condition A 13 , (i) the remaining amount of the battery  14  is or becomes smaller than the reference value. 
     Furthermore, the control unit  13  in the power saving mode shifts to the normal mode when a condition A 14  is satisfied. As an example of the condition A 14 , (i) in a state in which the remaining amount of the battery  14  is larger than the reference value, (ii) a state in which the lever type operator  151  is operated is set. 
     Furthermore, the control unit  13  in the normal mode is set in the stop state when a condition A 15  is satisfied. As an example of the condition A 15 , (i) the remaining amount of the battery  14  is or becomes smaller than the reference value. 
       FIG. 5A  is a flowchart for explaining the control form of the control unit  13  based on the input operation to the operation unit  15  by the user. When the user attempts to use the working machine  1  (before the lever type operator  151  is operated), the control unit  13  is generally in the state of the power saving mode or the stop state. For example, if the remaining amount of the battery  14  is sufficient (larger than the reference value), the control unit  13  is in the power saving mode. Note that the remaining amount of the fuel (gasoline) of the power unit  112  is sufficient, and thus the user can perform a necessary work sufficiently after setting the working unit  11  in the operating state by operating the operation unit  15 . 
     In step S 1000  (to be simply referred to as “S 1000 ” hereinafter) (the same applies to other steps), it is determined whether the remaining amount of the battery  14  is smaller than the reference value. For example, the power supply circuit unit  134  can evaluate the remaining amount of the battery  14 , and the control unit  13  can perform the determination processing based on a signal of the power supply circuit unit  134  indicating the evaluation result. If the remaining amount of the battery  14  is smaller than the reference value, the process advances to S 1010 ; otherwise, the process advances to S 1020 . In S 1010 , the control unit  13  is set in the stop state by making the system of the control unit  13  down, thereby ending this flowchart. 
     In S 1020 , it is determined whether the lever type operator  151  has been operated. If the lever type operator  151  has been operated, that is, the signal processing circuit unit  130  receives the detection signal De 1  from the detection circuit unit  131 , the process advances to S 1030 ; otherwise, the process returns to S 1000 . 
     In S 1030 , the control unit  13  shifts to the normal mode. In S 1020 , the control unit  13  is often in the power saving mode. However, the control unit  13  is in the stop state, for example, immediately after the battery  14  is replaced. In this case, in S 1030 , the control unit  13  shifts from the stop state to the normal mode. 
     In S 1040 , it is determined whether the operation of the lever type operator  151  has been released, that tis, whether the lever type operator  151  operated in S 1020  has been returned to an original state. If the operation of the lever type operator  151  has been released, the process advances to S 1050 ; otherwise, the process advances to S 1060 . In S 1050 , the control unit  13  shifts to the power saving mode, and the process returns to S 1000 . 
     In S 1060 , it is determined whether a predetermined period has elapsed since the operation of the lever type operator  151 . For example, the signal processing circuit unit  130  incorporates a counter (measurement unit) that measures an elapsed time since reception of the detection signal De 1 , and the control unit  13  can perform the determination processing based on the measurement result. If the predetermined period has elapsed, the process advances to S 1010 ; otherwise, the process advances to S 1070 . 
     As a case in which the process advances from S 1060  to S 1010 , a case is considered in which a state in which the lever type operator  151  is operated is fixed due to an unexpected reason such as a wrong use form by the user. In this case, the control unit  13  remains in the normal mode, and the power of the battery  14  is wastefully consumed, causing the battery down. To cope with this, if the predetermined period has elapsed since the operation of the lever type operator  151 , the control unit  13  is set in the stop state, thereby appropriately preventing the battery down. 
     In S 1070 , it is determined whether the button type operator  152  has been operated. If the button type operator  152  has been operated, that is, the signal processing circuit unit  130  receives the detection signal De 2  from the detection circuit unit  132 , the process advances to S 1080 ; otherwise, the process returns to S 1040 . 
     In S 1080 , the working unit  11  is set in the operating state. That is, the signal processing circuit unit  130  outputs the start signal St 1  to the starting circuit unit  133 , and starts the power unit  112  using the starter  113  (see  FIG. 2 ). 
       FIG. 5B  is a flowchart for explaining the operating state of the working unit  11  as an example of contents in S 1080  above. In S 1081 , it is determined whether the remaining amount of the battery  14  is smaller than the reference value. If the remaining amount of the battery  14  is smaller than the reference value, the process advances to S 1084 ; otherwise, the process advances to S 1082 . Note that S 1081  can be implemented in the same procedure as in S 1000 . 
     In S 1082 , it is determined whether the remaining amount of the fuel of the power unit  112  is smaller than the reference value. If the remaining amount of the fuel is smaller than the reference value (in general, the fuel is used up), it is determined that a work cannot be continued and the process advances to S 1085 ; otherwise, the process advances to S 1083 . 
     In S 1083 , it is determined whether the work load of the working unit  11  is larger than a reference value. If the work load of the working unit  11  is larger than the reference value, it is determined that the work cannot be continued and the process advances to S 1085 ; otherwise, the process advances to S 1090 . Note that examples of a condition for determining that the work load of the working unit  11  is larger than the reference value are generation of torque equal to or higher than an allowable value in the power unit  112 , and the amount of lawn (mowed lawn) in the grass bag  114  becoming equal to or larger than an allowable amount. 
     Since it is determined in S 1081  that the remaining amount of the battery  14  is smaller than the reference value, the control unit  13  is set in the stop state in S 1084  as in S 1010 , thereby ending this flowchart. 
     Since it is determined in S 1082  or S 1083  that the work cannot be continued, in S 1085  the working unit  11  is stopped, that is, the power unit  112  is stopped to stop the working mechanism  111 . Note that the lever type operator  151  remains in the operated state at this time, and thus the control unit  13  remains in the normal mode. 
     In S 1090 , it is determined whether the operation of the lever type operator  151  has been released. If the operation of the lever type operator  151  has been released, the process advances to S 1100 ; otherwise, the process returns to S 1080 . In S 1100 , the control unit  13  shifts to the power saving mode, and then the process returns to S 1000 . For example, if the operation of the lever type operator  151  is released while the working unit  11  is operated, the control unit  13  stops the working unit  11  while shifting to the power saving mode. For example, if the operation of the lever type operator  151  is released after the working unit  11  is stopped in S 1085 , the control unit  13  shifts to the power saving mode in response to the releasing of the operation. 
     Summarizing the above flowcharts, the user can start a work safely by performing a two-step operation of operating the button type operator  152  while operating the lever type operator  151 . The operation mode (normal mode/power saving mode) of the control unit  13  is switched by an input operation to the lever type operator  151  as the first step of the two-step operation. That is, the control unit  13  shifts to the normal mode when the lever type operator  151  is operated, thereby setting a state in which the control unit  13  stands by for an input operation to the button type operator  152  as the second step, that is, a state in which preparation for the operation of the working unit  11  is complete. Furthermore, the control unit  13  shifts to the power saving mode when the operation of the lever type operator  151  is released, thereby making it possible to relatively easily (with a relatively small number of operations) suppress the power consumption of the battery  14  by the control unit  13 . After the start of the work, the user can end/abort the work by releasing the operation of the lever type operator  151  as necessary/in accordance with completion of the work. In this case as well, it is possible to relatively easily make the control unit  13  shift to the power saving mode. 
     In general, the working machine is often used in a season in which a lawn grows easily, and the use frequency can vary depending on, for example, the season. Therefore, the working machine may be stored in a storage and may not be used for a relatively long period. In this case, the battery down of the working machine may occur. 
     The working machine  1  according to this embodiment includes the control unit  13  having, as the operation modes, the normal mode and the power saving mode. The normal mode is a mode in which the working unit  11  is operable based on power of the battery  14 . The power saving mode is a mode in which some functions are limited, as compared with the normal mode, to make the working unit  11  inoperable and the power consumption of the battery  14  is suppressed, as compared with the normal mode. According to this embodiment, if the working machine  1  is not used for a relatively long period, it is possible to appropriately prevent the battery down by setting the control unit  13  in the power saving mode. Furthermore, even if it is expected not to use the working machine  1  for a relatively long period, the user is not forced to detach the battery  14 , and thus the usability of the working machine  1  is also improved. 
     According to this embodiment, since the operation mode of the control unit  13  is switched based on an input operation to the operation unit  15  by the user for controlling operating state of the working unit  11 , it is unnecessary to newly provide a dedicated operation unit for switching the operation mode. Therefore, according to this embodiment, the battery down can be prevented with a relatively simple arrangement. In this embodiment, the operation unit  15  includes the lever type operator  151  and the button type operator  152 , and the user can set the working unit  11  in the operating state by operating the button type operator  152  while operating the lever type operator  151 . This two-step operation allows the user to start a work safely, and it is also possible to prevent the battery down relatively easily. 
     According to this embodiment, since the operation of the second step of the two-step operation cannot be detected unless the operation of the first step is performed, safety of control by the control unit  13  can be improved. The control unit  13  is applicable to various applications in which the two-step operation is preferable, and the control target is not limited to the constituent components of the working machine  1 . 
     The present invention is not limited to some examples described above and contents of the embodiment may partially be modified without departing from the scope of the invention. In addition, individual terms described in this specification are merely used for the purpose of explaining the present invention, and the present invention is not limited to the strict meanings of the terms, as a matter of course, and can also incorporate their equivalents. For example, the embodiment has explained, as a preferable example of the working machine  1 , a lawn mower that performs lawn mowing. However, an outline of the working machine  1  includes various working vehicles, and can include, for example, a snowplow that performs snow removing as a work as well as an agricultural working machine such as a cultivator. 
     The features of the above-described embodiment will be summarized below. 
     The first aspect is related to a working machine (for example 1), and the working machine is a working machine with a working unit (for example, 11) configured to perform a work, comprising a battery (for example, 14) and a control unit (for example, 13), wherein the control unit has, as operation modes, a normal mode in which the working unit is operable based on power of the battery, and a power saving mode in which the working unit is made inoperable by limiting some of functions, as compared with the normal mode, and power consumption of the battery is suppressed, as compared with the normal mode. 
     According to the first aspect, it is possible to appropriately prevent a battery down that can be caused when the working machine has not been used for a relatively long period. In addition, since it is unnecessary to detach the battery, it is possible to improve the usability of the working machine. 
     In the second aspect, the working machine further comprises an operation unit (for example, 15) configured to accept an operation of controlling an operating state of the working unit, wherein the control unit changes the operation mode based on the operation input to the operation unit. 
     According to the second aspect, since it is possible to switch the operation mode by an operation performed when operating the working unit, it is unnecessary to newly provide a dedicated operation unit for switching the operation mode. Therefore, the battery down can be prevented with a relatively simple arrangement. 
     In the third aspect, the operation unit includes a first operator (for example, 151) and a second operator (for example, 152), and the working unit is set in the operating state when a user operates the second operator while operating the first operator. 
     According to the third aspect, since the working unit can be set in the operating state by, for example, pressing a button type operator as the second operator while pulling a lever type operator as the first operator (by a so-called two-step operation), it is possible to start the work safely while improving the usability. 
     In the fourth aspect, the working machine further comprises a main body portion (for example, 10) to which the working unit is attached, and an extended portion (for example, 18) extended from the main body portion to a rear side and an upper side to be grippable by the user, wherein both the first operator and the second operator are provided in the extended portion. 
     According to the fourth aspect, since the first and second operators are provided at positions where the user readily operates them, it is possible to further improve the usability. 
     In the fifth aspect, when the user releases the operation of the first operator, the control unit is set in the power saving mode. 
     According to the fifth aspect, since the control unit is set in the power saving mode when releasing the operation of the first step of the two-step operation, it is possible to prevent the battery down relatively easily (with a relatively small number of operations). 
     In the sixth aspect, when a remaining amount of the battery becomes smaller than a reference value, the control unit is set in a stop state in which all the functions are limited. 
     According to the sixth aspect, a state in which the control unit has substantially no power consumption is set by limiting all the functions of the control unit (by making the system of the control unit down). 
     In the seventh aspect, if the user has not operated the second operator for a predetermined period in a state in which the first operator is operated, the control unit is set in the stop state. 
     According to the seventh aspect, it is possible to prevent the control unit from being maintained in the normal mode due to a wrong use form or the like. Note that a value (for example, several tens of sec to several min or more) sufficiently larger than a time generally required to perform the two-step operation is set as the predetermined period. 
     In the eighth aspect, when the user operates the first operator, the control unit is set in the normal mode. 
     According to the eighth aspect, the control unit can be set in the normal mode relatively easily by performing the operation of the first step of the two-step operation, thereby completing preparation for the operation of the working unit. Note that a case in which the control unit is set in the normal mode includes a case in which the control unit shifts from the power saving mode to the normal mode, and a case in which the control unit returns from the stop mode to the normal mode. In the latter case, a signal indicating that the operation of the first step has been performed acts as a signal indicating a return instruction to the control unit. 
     In the ninth aspect, the control unit includes a first detection circuit unit (for example,  131 ) configured to detect, using a first voltage (for example, V 1 ′), an operation input to the first operator, and a second detection circuit unit (for example,  132 ) arranged electrically independent of the first detection circuit unit, and configured to detect, using a second voltage (for example, V 2 ) different from the first voltage, an operation input to the second operator. 
     According to the ninth aspect, since the working unit is operable under a condition under which each of the first and second voltages is supplied, it is possible to improve safety when used with the relatively simple arrangement. 
     In the 10th aspect, the control unit further includes a signal processing circuit unit (for example,  130 ) configured to perform predetermined signal processing by receiving, from the first detection circuit unit and the second detection circuit unit, detection signals (for example, De 1 , De 2 ) indicating that the operations have been input to the first operator and the second operator, respectively, and the signal processing circuit unit generates the second voltage using the first voltage, and supplies the second voltage to the second detection circuit unit. 
     According to the 10th aspect, it is possible to appropriately implement the ninth aspect. 
     In the 11th aspect, the first voltage is a voltage of the battery. 
     According to the 11th aspect, it is possible to appropriately implement the ninth aspect. 
     In the 12th aspect, the working unit includes a working mechanism (for example,  111 ) configured to execute the work, and a power unit (for example,  112 ) configured to generate power to be supplied to the working mechanism. 
     According to the 12th aspect, each of the above-described aspects can preferably be applied to the working machine including the working mechanism and the power unit configured to supply power to the working mechanism. 
     In the 13th aspect, when the user operates the first operator, the control unit is set in the normal mode and can detect the operation input to the second operator, when the user operates the second operator while operating the first operator, the control unit sets the working unit in the operating state, and when the user releases the operation of the first operator, the control unit stops the working unit and is set in the power saving mode. 
     According to the 13th aspect, it is possible to implement both switching of the operation mode and the operation of the working unit in the two-step operation, and also set the control unit in the power saving mode relatively easily when the work ends or is aborted. 
     In the 14th aspect, the working machine is a walking type working machine (for example, 1). 
     According to the 14th aspect, each of the above-described aspects can be applied to a known walking type working machine appropriately. 
     The 15th aspect is related to a control apparatus (for example, 13), and the control apparatus is a control apparatus for controlling a control target (for example,  11 ) by receiving a first voltage (for example, V 1 ′) from a battery (for example,  14 ), comprising a first detection circuit unit (for example,  131 ) configured to output a first detection signal (for example, De 1 ) using the first voltage, a second detection circuit unit (for example,  132 ) configured to output a second detection signal (for example, De 2 ) using a second voltage (for example, V 2 ) different from the first voltage, and a signal processing circuit unit (for example,  130 ) configured to perform signal processing of controlling the control target based on the first detection signal and the second detection signal, wherein a normal mode and a power saving mode in which power consumption of the battery is suppressed, as compared with the normal mode are included as operation modes, and the signal processing circuit unit generates, in the normal mode, the second voltage based on the first voltage and supplies the second voltage to the second detection circuit unit, and suppresses the supply in the power saving mode. 
     According to the 15th aspect, since, in the embodiment, the operation of the second step of the two-step operation cannot be detected unless the operation of the first step is performed, safety of control can be improved. The control apparatus is usable in various applications in which the two-step operation is preferable. For example, the control apparatus may be used to control an industrial robot, a manipulator, and the like for the purpose of, for example, improvement of safety. 
     The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention, the following claims are made.