The present invention relates to an engine working machine such as a chain saw and a brush cutter.
A small-sized engine is widely used as a power source for a small-sized working machine such as brush cutters or chain saws.
The engine used for the engine working machine has a small size and a light weight and can obtain a large output, so that operation for a long time can be achieved by supplying fuel thereto. On the other hand, in the engine, it is required to reciprocate a piston through combustion of air-fuel mixture, and therefore, start-up may takes longer than an electric motor. Accordingly, Patent Literature 1 suggests an engine equipped with a manual start-up fuel supplier. In this engine, when a crank shaft is driven by a recoil-type starter, a supply button of the start-up fuel supplier is pressed, so that start-up supplemental fuel is supplied from the start-up fuel supplier to the carburetor. Further, Patent Literature 2 suggests an automatic choke mechanism in which a solenoid valve is assembled into the carburetor.
PTL 1: Japanese Utility-Model Application Laid-Open Publication No. H06-49895
PTL 2: Japanese Patent Application Laid-Open Publication No. 2007-32500
In order to improve startability of the engine, it is general, in the carburetor, to provide a manual choke mechanism or the start-up fuel supplier as described in the Patent Literature 1. When the engine is in a cold time and an outside air temperature is low, an operator who tries to start the engine up operates the choke mechanism or others for starting the engine up. In this manner, an intake air amount is reduced in the carburetor, and besides, a negative pressure is generated therein, so that fuel is forcibly drawn out of the carburetor, and the air-fuel mixture that is taken into a cylinder is thickened. However, in a conventional small-sized engine, the operator manually operates the choke or the start-up fuel supplier. It is accordingly necessary to determine when the timing to operate the choke or others is and how much the amount of operation of the choke or others is, and the determination is burden for the operator. Also, when the operation of the choke or the start-up fuel supplier is inappropriate, the start-up of the engine adversely takes for a long time in some cases. Also, since the automatic choke mechanism of Patent Literature 2 has the configuration in which the solenoid valve is assembled into the carburetor, a problem of increase in a cost of the carburetor arises.
The present invention has been made in view of the above-described background, and its preferred aim is to suppress a cost of the engine working machine and to improve the startability of the engine.
The typical feature of the inventions disclosed in the present application will be briefly described as follows.
In an engine working machine according to one embodiment, the engine working machine drives a working tool by using an engine having: a fuel tank; a carburetor for supplying an air-fuel mixture of fuel supplied from the fuel tank and air into a cylinder; a cylinder through which piston can reciprocate; and a crank case holding the cylinder and forming a crank chamber. The engine working machine is provided with: an additional fuel supplying unit for supplying fuel to the engine separately from the carburetor; and a control unit for controlling operation of the additional fuel supplying unit separately from supply of a start-up fuel.
According to the present invention, since the additional fuel supplying unit is provided separately from the carburetor, the cost of the engine working machine can be suppressed, and the startability of the engine can be improved.
The above and other preferred aims and novel characteristics of the present invention will be apparent from the description of the present specification and the accompanying drawings.
Hereinafter, a first example of the present invention will be explained based on the drawings. Note that the same components are denoted by the same reference symbols in the following drawings, and repetitive explanations thereof will be omitted. Further, the present specification will be explained so that front and back, right and left, and up and down directions are those illustrated in the drawings. While a brush cutter will be exemplified as an engine working machine 1 according to the present example, explanation of an outline shape of this brush cutter will be omitted since the outline shape thereof is the same as that as illustrated in
A decompression mechanism (hereinafter referred to as “decompression”) 31 is provided at a position adjacent to a combustion chamber of the cylinder 11 (at a side surface of the cylinder 11 in
As the start-up device of the engine 10 according to the present example, two systems of a cell motor 106 and a recoil starter 40 are provided. The cell motor 106 and the recoil starter 40 are arranged inside a starter cover 9. The cell motor 106 is rotated by electric power supplied via a connecting wire 102. By the rotation of the cell motor 106, a pinion 77 provided at a rotation shaft 106a is rotated, and a gear 49 meshed with the pinion 77 is rotated. The gear 49 is held by the crank shaft 13 via a bearing 48 so as to be rotatable. When the gear 49 rotates at a high speed, a one-way clutch 78 attached to a part of the gear 49 is protruded radially outward by centrifugal force. And, the one-way clutch 78 protruded radially outward comes in contact with a first drum 79 to rotate the first drum 79, and the first drum 79 rotates the fixed crank shaft 13. The recoil starter 40 has a reel 41 on which a starter rope 42 is wound. By pulling the starter rope 42 by using a starter handle (not illustrated) so as to rotate the reel 41 at a high speed, the one-way clutch 46 is protruded radially outward by centrifugal force. And, the one-way clutch 46 protruded radially outward comes in contact with a second drum 47 so as to rotate the second drum 47. Since the second drum 47 is fixed to the crank shaft 13, the crank shaft 13 is rotated by the rotation of the second drum 47, so that the engine can be started up. The starter rope 42 pulled out from the reel 41 is wound on the reel 41 by restoring force of a spiral spring 43.
A battery housing unit 39 is provided separately from, for example, two grip portions 1009 (see
Inside the battery 80, for example, four lithium ion battery cells (not illustrated) of size 14500 are housed. A shape of a back end portion (lower side in
An insulator 19 is provided between the carburetor 35 and the cylinder 11. The insulator 19 forms an air intake passage and also fixes the carburetor 35. The insulator 19 is attached to the cylinder 11 by using a screw 20. The carburetor 35 is attached to the insulator 19 by using two screws 21 (while
In this manner, the additional fuel supplying device 50 is arranged between the insulator 19 and the carburetor 35. Also, the additional fuel supplying device 50 is provided in the path of the fuel pipe 71 for supplying the fuel. In this manner, a fuel tank having exactly the same shape as that of a conventional device, that is, a fuel tank having two through holes 27b and 27c can be used as it is as the fuel tank 27. Moreover, since it is not necessary to change the configurations of the insulator 19 and the carburetor 35, it is not necessity to change conventional components in order to achieve the present invention, so that the present example can be easily achieved. A filter 72 is provided for preventing suction of dust at a distal end of the fuel pipe 73 on the fuel tank 72 side. Rubber bushes 76a and 76b for preventing leakage of the fuel are provided at the through holes 27b and 27c of the fuel tank 27.
The carburetor 35 is provided with a priming pump 37 for sucking the fuel from the fuel tank 27 to the carburetor 35. When the operator repeatedly pushes the priming pump 37 immediately before the start-up of the engine, the fuel is supplied to the carburetor 35 until the fuel flows to the return pipe 74. The priming pump 37 has a semispherical transparent valve unit. The operator can visually confirm that the fuel reaches the carburetor 35, from the reaching of the fuel to the transparent valve portion. Since the additional fuel supplying device 50 is provided in the middle of the path of the fuel pipe 71 provided for supplying the fuel to the carburetor 35, completion of a sucking operation of the fuel toward the carburetor 35 also means completion of a sucking operation of the fuel toward the additional fuel supplying device 50. In this manner, such a trouble that the fuel has not still reached the additional fuel supplying device 50 in the start-up of the engine 10 can be reliably prevented.
The fuel chamber 57 is arranged above the fixing adaptor 15, a solenoid valve fixing unit 56 is arranged above the fuel chamber 57, and a solenoid valve 51 is arranged above the solenoid valve fixing unit 56. The fuel chamber 57, the solenoid valve fixing unit 56, and the solenoid valve 51 are fixed to the fixing adaptor 15 by using two bolts 61. The solenoid valve fixing unit 56 is provided with a fuel inlet path 60a for supplying the fuel into the additional fuel supplying device 50 and a fuel outlet path 60b for discharging fuel from the inside of the additional fuel supplying device 50. A flow path from the fuel inlet path 60a to the fuel outlet path 60b is arranged to be linear. In this manner, this arrangement does not interfere the fuel supply from the fuel tank 27 to the carburetor 35. The solenoid valve 51 is provided with two lead wires 53.
One end portion of the plunger 54 is held by a movable piece 52. On the other end portion of the plunger 54, the distal end portion 54a formed in a conical shape is formed. The flow path is closed when the distal end portion 54a contacts the plunger abutting portion 58, and the flow path is opened when the distal end portion 54a separates from the plunger abutting portion 58. Also, an amount of additional fuel flowing toward the air-intake path 15a side is adjusted depending on a distance between the distal end portion 54a and the plunger abutting portion 58. A cylindrical protruding portion 56b is formed on the outlet side of the solenoid valve fixing unit 56, and the protruding portion 56b is inserted into a cylindrical space 57a having a predetermined size. An O ring 59a is arranged at a connecting portion between the protruding portion 56b and the cylindrical space 57a for preventing leakage of the fuel from the connecting portion. A protruding portion 57b that extends toward a drain side is formed in the fuel chamber 57, and a flow path 57c is formed inside the protruding portion 57b. The protruding portion 57b of the fuel chamber 57 is attached to a cylindrical attachment hole 15d formed in the fixing adaptor 15. A bottom portion of the attachment hole 15d is opened toward the air-intake path 15a. The air-intake path 15a communicates into the crank chamber. An O ring 59b is arranged at a connecting portion between the protruding portion 57b and the attachment hole 15d for preventing leakage of the fuel from the connecting portion.
The microcomputer 118 is driven at a constant voltage that is supplied by the regulator 116. An output signal of the thermistor 119 that indicates a temperature of the engine 10, a signal that indicates a voltage of the battery 80 caused by the resistors 111 and 112, and an output signal of a rotation detecting coil 105 are inputted to a plurality of A/D converting ports of the microcomputer 118. An engine rotation pulse signal is a signal that indicates an engine rotation speed, that is, a rotation speed of the crank shaft 13, which is a signal that indicates change in magnetic flux of a magnet that rotates with the crank shaft 13. The change in the magnetic flux of the magnet are converted into a voltage by the rotation detecting coil 105, and this voltage signal is inputted to the microcomputer 118 and is detected as the engine rotation pulse signal. In this manner, the microcomputer 118 is functioned as a rotation-speed detecting unit for detecting the engine rotation speed. The microcomputer 118 performs predetermined logic computation using these input values, transmits a gate signal to the FETs 117 and 122, and controls conduction or interruption between a sources and a drain of the FETs 117 and 122.
The FET 121 is a switching element for controlling current supply to the cell motor 106. The source and the drain of the FET 121 are conducted to each other by an instruction of the microcomputer 118 (which is supply of the gate signal). The FET 122 is a switching element for opening the solenoid valve 51. The source and the drain of the FET 122 are conducted to each other by an instruction of the microcomputer 118 (which is supply of the gate signal). When the source and the drain of the FET 122 are conducted to each other, electric power is supplied to the solenoid valve 51 so as to open the solenoid valve 51. As described above, the solenoid valve 51 is provided in vicinity of the carburetor 35 for supplying the fuel into the cylinder 11 of the engine 10.
Next, a fuel supplying condition performed by the carburetor 35 and the additional fuel supplying device 50 in the engine start-up will be explained by using
Next, a fuel supplying condition performed by the carburetor 35 and the additional fuel supplying device 50 in the engine start-up will be explained by using
As illustrated in
Here, it is determined whether to shift to the maintenance mode or not by any one of follows.
(1) A switch (mode switch 128) dedicated for instructing execution of the maintenance mode is provided to execute the maintenance mode in accordance with setting of the mode switch 128.
(2) The microcomputer 118 monitors the change in the engine rotation speed during the stop time, and executes the maintenance mode when it is determined that rotation is difficult to be maintained such that the rotation decreases.
(3) An engine stop period taken from the previous engine stop is calculated, and the maintenance mode is executed when the calculated stop time exceeds a predetermined value.
(4) The shift determination is made when the microcomputer 118 determines to execute the maintenance mode from the above-described conditions or from a different condition from the above-described conditions (such as engine temperature or outside air temperature).
In the present example, the additional fuel is supplied in the maintenance mode by opening the solenoid valve 51 during only one rotation of four rotations of the crank shaft 13. That is, in the maintenance mode, the additional fuel is supplied from the additional fuel supplying device 50 during one rotation of “m” rotations (here, “m is equal to or larger than 2”) of the engine 10. Note that the term of “m” rotations of the engine 10 indicates a term of “m” rotations of the crank shaft 13. In this manner, in the maintenance mode, the fuel is not supplied from the additional fuel supplying device 50 each time when the engine 10 rotates as in the initial start-up mode, but intermittently supplied from the additional fuel supplying device 50. While a relation of “m=4” is set in the present example, the present invention is not limited to this relation but the fuel may be supplied from the additional fuel supplying device 50 at any interval as long as the idling engine rotation speed of the engine 10 can be maintained without supplying the fuel from the carburetor 35. Further, a frequency of the supply of the fuel from the additional fuel supplying device 50 is not always required to be one rotation of “m” rotations (here, “m is equal to or larger than 2”) but may be “n” rotations (here, “m is larger than n”) of “m” rotations (here, “m is equal to or larger than 2”). It is important here to maintain the idling condition normally without the stop of the engine 10. The solenoid valve 51 of the present example is switched into two stages of an open stage and a close stage. Therefore, the amount of fuel that is supplied into the air-intake path from the additional fuel supplying device 50 is adjusted by the length of time required for opening the solenoid valve 51. Here, if an electrically con-trollable adjustment valve which can also control the flow rate is used as the solenoid valve 51, it is also possible to employ a configuration in which a small amount of the fuel is supplied for each rotation in the maintenance mode.
As explained above, in the normal start-up mode, the solenoid valve 51 is turned ON during only initial some rotations in synchronization with the engine rotation pulse signal as illustrated in
For example, while mixed fuel obtained by mixing gasoline and fuel is used as the fuel in a two-cycle engine, this becomes a cause for worsening the startability of the engine if this mixed fuel is left over a long period of time. By degradation of the oil in the mixed fuel, a viscosity of the oil is increased to change the oil into a gum-like texture, which results in such a problem that the inside of the carburetor 35 clogs. It is possible to solve these problems by executing the maintenance mode using the additional fuel supplying device 50.
Next, the series of operations of the engine working machine 1 according to the present invention will now be explained using the flowcharts of
Next, in Step 205, the microcomputer 118 detects a temperature based on an output signal from the thermistor 119. This temperature detection is performed by inputting a voltage that has been divided by the thermistor 119 and the resistor 120 into an A/D converting input terminal of the microcomputer 118. As for a position for arranging the thermistor 119, it may be mounted at a part of the engine 10 when the temperature of the engine 10 is desirably measured, or it may be mounted at the control circuit board 90 when the outside air temperature is desirably measured. In accordance with the detected temperature, the microcomputer 118 determines the number of times of the turning ON of the solenoid valve 51 in the engine start-up and the ON time for once. More specifically, the lower the temperature is, the more the number of times of turning the solenoid valve 51 ON is, and the more the amount of fuel to be added is. For example, in the example of
Next, in Step 206, the microcomputer 118 determines whether a mode switch is necessary or not. This mode switch is to select either the normal start-up mode (during which the additional fuel supplying device 50 is operated in only the initial start-up control as illustrated in
Here, when the operator pulls the starter handle or pushes the starter switch 125 of the cell motor 106, the engine 10 starts to rotate so that an engine rotation pulse signal is generated at the rotation detecting coil 105 each time when one rotation of the engine 10 is performed. When the microcomputer 118 detects the engine rotation pulse signal, the procedure proceeds to Step 210. In Step 210, the FET 122 is turned ON during only the ON time for one rotation determined in Step 205 to open the solenoid valve 51 so as to supply fuel from the additional fuel supplying device 50.
Next, the procedure proceeds to Step 211 to determine whether the number of ON times of the solenoid valve 51 has reached the number of ON times determined in Step 205 or not. If it has not reached the target number of ON times, the procedure returns to Step 209 to stand-by a next engine rotation pulse signal. Steps 209 to 211 are repeated, and the procedure proceeds to Step 212 at the point of time the target number of ON times has been reached.
Next, in Step 212, it is determined whether the maintenance mode is set or not. When the maintenance mode is not set, the procedure proceeds to Step 216 to turn the FET 117 OFF. Since the FET 107 is also turned OFF by turning the FET 117 OFF, the power source of the control circuit is shutdown. When it is determined in Step 212 that the maintenance mode is set, the procedure proceeds to Step 213. The maintenance mode can be divided into two modes of the initial start-up mode for supplying the large amount of fuel for a predetermined period of time at an initial stage as similar to the normal start-up mode and the maintenance mode for continuing the supply of the large amount of fuel without operating the carburetor 35 after the start-up of the engine. After Step 213, the mode is the latter one of the maintenance mode. The microcomputer 118 determines whether the engine rotation pulse signal has been detected a predetermined number of times or not, and the procedure proceeds to Step 214 at a point when it has been detected the predetermined number of times. In Step 214, the FET 122 is turned ON during only the ON time for one rotation in the maintenance mode determined in Step 205 to open the solenoid valve 51 so as to supply fuel from the additional fuel supplying device 50.
Next, the procedure proceeds to Step 215, and it is determined whether the number of ON times of the solenoid valve 51 has reached the number of ON times (three times in the example of
As described above, according to the present example, the additional fuel supplying device 50 is provided separately from the carburetor 35, and therefore, it is possible to supply fuel from the additional fuel supplying device 50 even though the carburetor 35 has the failure, and it is possible to improve the startability of the engine 10. Moreover, since the additional fuel supplying device 50 is provided separately from the carburetor 35, it is possible to employ a conventional carburetor 35 as it is, so that the cost of the engine working machine 1 can be reduced. Further, in the normal start-up mode, supply of fuel from the solenoid valve 51 is successively (once or more within each rotation) performed in addition to fuel supply from the carburetor 35. However, in the maintenance mode, supply of fuel from the solenoid valve 51 is intermittently performed for a predetermined period of time immediately after start-up. By the provision of such a maintenance mode, it is possible to reliably start the engine 10 up and to effectively remove clogging of the carburetor 35. Note that it is determined whether the maintenance mode is executed or not by the operating condition of the mode switch 128 in the flowchart of
In the foregoing, the present invention has been concretely described based on the example. However, it is needless to say that the present invention is not limited to the foregoing example and various modifications and alterations can be made within the scope of the present invention. For example, in the above-described example, the explanation has been made by exemplifying the brush cutter as the example of the engine working machine. However, not only the brush cutter but also other engine working machines such as a cutter, a chain saw, a lawn mower, and a cultivator may be adopted. Moreover, while the above-described example has been explained with the example of the two-cycle engine, an engine working machine equipped with a four-cycle engine may be adopted.
A second example of the present invention will now be explained with reference to the drawings. As similar to the above-described the first example, explanations will be made so that directions in front and back, right and left, and up and down are the directions as illustrated in the drawings also in the second example. Also, members and parts that are identical to the above-described members and parts are denoted by the same reference symbols, and explanations thereof will be omitted. While explanations are made by exemplifying the brush cutter as the example of the engine working machine 501 according to the present example, explanations of the external shape of this brush cutter is omitted since the external shape thereof is identical to that as illustrated in
When the engine 10 is desirably started up, the operator operates to turn the power source switch 110 ON, and then, the operator pulls a starter handle of the recoil starter 40. Although not illustrated in the drawings, it is preferred to provide an LED or others that is lighted in conjunction with the power source switch 110 in vicinity of the power source switch 110. By the provision of such an LED, the operator can easily identify whether the power source switch 110 is in the ON or OFF condition. As described later, since the additional fuel supplying device 50 is automatically turned OFF, it is not necessary for the operator to turn the power source switch 110 OFF. For stopping the engine 10 during driving, the operator pushes a stop switch not illustrated. The stop switch is a so-called kill switch that stops ignition of the engine 10. The stop switch is provided at any position on the engine 10 side (for example, at an upper cover 7).
For example, four lithium ion battery cells (not illustrated) of size 14500 are embedded into a battery 80 that is housed in the battery housing unit 39. A shape of a back end portion (lower side in
The microcomputer 118 is driven at a constant voltage that is supplied by the regulator 116. An output signal of the thermistor 119 that indicates a temperature of the engine 10, a signal that indicates a voltage of the battery 80 caused from the resistors 111 and 112, and an output signal of a rotation detecting coil 105 are inputted to a plurality of A/D converting ports of the microcomputer 118. An engine rotation signal is a signal that indicates an engine rotation speed, that is, the rotation speed of a crank shaft 13, and is a signal that indicates change in magnetic flux of the magnet that rotates with the crank shaft 13. The change in magnetic flux of the magnet is converted into a voltage by the rotation detecting coil 105, and is detected as an engine rotation pulse signal when the voltage signal is inputted to the microcomputer 118. The microcomputer 118 performs a predetermined logic computation using these input values, transmits a gate signal to the FETs 117, 122 and 132, and control conduction and interruption between a source and a drain of the FETs 117, 122 and 132.
The FET 122 is a switching element for opening the solenoid valve 51. The source and the drain of the FET 122 are conducted to each other by an instruction (supply of the gate signal) of the microcomputer 118. When the source and the drain of the FET 122 are conducted to each other, electric power is supplied to the solenoid valve 51 so as to open the solenoid valve 51. By the opening of the solenoid valve 51, additional fuel is supplied to a combustion chamber of the engine 10 separately from the fuel (air-fuel mixture) that is supplied from the carburetor 35. When the supply of the gate signal from the microcomputer 118 stops, the source and the drain of the FET 122 are in a non-conducted condition. In the non-conducted condition between the source and the drain of the FET 122, a plunger 54 (see
In the present example, the microcomputer 118 is started so that the solenoid valve 51 can be driven when the operator turns the power source switch 110 ON in the start-up of the engine. While it is possible to configure the microcomputer 118 to operate full time after the start-up of the engine 10, this adversely results in consumption of power of the battery 80 in this case. The control circuit 91 accordingly has the capacitor 129 as a storage unit for storing power that is generated by the rotation detecting coil 105. When the voltage of the capacitor 129 reaches a predetermined voltage, gate current having a predetermined voltage is carried from the capacitor 129 to the FET 117 so that this condition is maintained in the same condition in which the power source switch 110 is turned ON. In this manner, during the rotation of the engine 10, the microcomputer 118 is activated each time when a predetermined amount of electric charge is stored in the capacitor 129. The activated microcomputer 118 outputs the gate signal to the FET 132 so as to maintain the FET 117 in the ON condition and prevents charging of electric charge to the capacitor 129. The time at which the electric charge of the capacitor 129 reaches a predetermined voltage can be adjusted by a capacitance of the capacitor 129 and the resistor 130. The diodes 126, 127 and 131 are provided for preventing reverse current. In the control circuit 91 of the present example, the microcomputer 118 releases the ON condition of the FET 117 after elapse of a predetermined time to interrupt its own power source. Then, the charging to the capacitor 129 is started by power that is induced by the rotation detecting coil 105. When the charge to the capacitor 129 is completed and the voltage applied from the capacitor 129 to the FET 117 reaches a predetermined voltage, the FET 117 is switched to the ON condition, so that the microcomputer 118 is again activated. In this manner, the microcomputer 118 is periodically activated by the power stored in the capacitor 129. After elapse of a predetermined time after the activation, the microcomputer 118 interrupts its own power source. That is, the microcomputer 118 is in the ON condition for only short time for each constant period. In such a period, for example, the microcomputer 118 is set to be activated every 2 or 3 seconds during the rotation of the engine 10 and is stopped after 1 or 2 seconds so that these ON-OFF conditions of the microcomputer 118 are repeated.
Next, a series of operations of the engine working machine 501 according to the present invention will be explained using the flowcharts of
Next, in Step 1205, the microcomputer 118 detects a temperature based on an output signal from the thermistor 119. This temperature detection is performed by inputting a voltage divided by the thermistor 119 and the resistor 120 to an A/D converting input terminal of the microcomputer 118. As for a position at which the thermistor 119 is arranged, the thermistor 119 may be mounted to, for example, a part of the engine 10 when the temperature of the engine 10 is desirably measured. When the outside air temperature is desirably measured, the thermistor 119 may be mounted to, for example, the control circuit board 90. In accordance with the detected temperature, the microcomputer 118 determines the number of times of turning ON of the solenoid valve 51 (Step 1206). The timing for turning the solenoid valve 51 ON may be determined in accordance with a position of the piston 12 during one rotation of the engine 10 (the solenoid valve is opened and closed only once during one rotation of the engine). The control may be performed so that the solenoid valve 51 is opened intermittently “n” times during “m” rotation of the engine 10 (here, “m is equal to or larger than n”). At this time, the lower the temperature is, the more the number of turning ON of the solenoid valve 51 is, and the more the amount of fuel to be added is. Note that there is a risk that the engine 10 stops, that is, there is a risk that the ignition plug 25 misfires when the solenoid valve 51 is continuously controlled to be opened except for the case in which a large amount of fuel is required for acceleration. It is accordingly important to set an optimal amount of additional fuel in accordance with the condition of combustion. The microcomputer 118 may store optimal values of a relation between the number of times of turning ON of the solenoid valve 51 and the temperature and a relation between the number of times of turning ON of the solenoid valve 51 and the engine rotation speed.
Next, the microcomputer 118 detects whether a rotation signal of the engine 10 has been detected or not (Step 1207), and stands-by until it is detected. The rotation signal of the engine 10 can be detected by the output of the rotation detecting coil 105. Here, when the operator pulls the non-illustrated starter handle of the coil starter 40, the engine 10 starts to rotate, so that an engine rotation signal is generated at the rotation detecting coil 105 each time when one rotation of the engine 10 is performed. When the microcomputer 118 detects the engine rotation signal, the procedure proceeds to Step 1208. In Step 1208, the FET 122 is turned ON for predetermined time to conduct the solenoid valve 51, so that a plunger abutting portion 58 (see
Next, the procedure proceeds to Step 1209 to determine whether the number of times of turning ON of the solenoid valve 51 has reached the predetermined number of times (for example, ten times) or not. When the number has not reached ten times here, the procedure returns to Step 1207 to stand-by the next engine rotation signal. Steps 1207 to 1209 are then repeated, and the procedure proceeds to Step 1210 at a point when the number of times of turning ON of the solenoid valve 51 has reached ten times. Next, the procedure proceeds to Step 1210 so as to monitor the idling rotation speed at the initial stage of the engine start-up. The monitoring of the idling rotation speed from the beginning of the engine start until elapse of predetermined time is for preventing the increase in the rotation speed due to thinning of the fuel concentration inside the cylinder 11. When the engine rotation speed exceeds a previously-set upper limit value (threshold), the procedure proceeds to Step 1211 so as to turn the solenoid valve 51 ON for predetermined time, so that additional fuel is injected so as to thicken the concentration inside the cylinder 11, and further increase in the engine rotation speed of the engine 10 is limited.
The procedure then proceeds to Step 1212, and the microcomputer 118 determines whether predetermined time has elapsed since the engine start or not. Here, if the previously-set predetermined time has not elapsed yet, the procedure returns to step 1210 to monitor the idling rotation speed. If the predetermined time has elapsed, the procedure proceeds to Step 1213. In Step 1213, an increase value of the engine rotation speed per unit time is monitored, and it is determined that the engine 10 is in the accelerating condition if this value exceeds a previously-set reference value. When it is judged that it is in the accelerating condition as described above, the procedure proceeds to Step 1215 to turn the solenoid valve 51 ON for predetermined time, so that additional fuel is injected so as to support a shortage in the fuel, and accelerating property of the engine 10 is improved.
When it is determined in Step 1213 that the previously-set reference value has not been exceeded yet, the procedure proceeds to Step 1214 to monitor the upper limit value of the engine rotation speed. When the engine rotation speed exceeds the previously-set upper value, the procedure proceeds to Step 1215 to turn the solenoid valve 51 ON for predetermined time, so that additional fuel is injected so as to thicken the concentration inside the cylinder 11, and further increase in the engine rotation speed of the engine is limited. This supply of additional fuel at this time is to suppress further increase in the rotation, and may not thicken the concentration as much as the engine rotation speed decreases. Next, the procedure proceeds to Step 1216 so that the microcomputer 118 determines whether predetermined time has elapsed since the activation or not. Here, if the previously-set predetermined time has not elapsed yet, the procedure returns to Step 1213 to monitor the engine rotation speed. If the predetermined time has elapsed, the FETs 117 and 132 are turned OFF (Step 1217). Since the FET 107 is also turned OFF by turning the FET 117 OFF, the power source of the control circuit 91 is once shut down.
Next, since the engine 10 continuously rotates, the engine rotation signal is continuously outputted from the rotation detecting coil 105. That is, power that is induced by the rotation detecting coil 105 is charged to the capacitor 129 via the diode 131 and the resistor 130 (Step 1218). The capacitor 129 is connected to a gate terminal of the FET 117 via the diode 127, and the FET 117 is again turned ON (Step 1219) when the predetermined time has elapsed so that the voltage of the capacitor 129 exceeds a gate ON voltage of the FET 117. Next, when the FET 107 is turned ON (Step 1220), the microcomputer 118 is again activated (Step 1221). The microcomputer 118 turns the FET 117 and 132 ON by supplying the gate signal so that the ON condition of the FET 107 is maintained (Step 1222). By turning the FET 132 ON, the voltage charged to the capacitor 129 is once discharged. The procedure then returns to Step 1213 to control the solenoid valve 51 in accordance with the condition of the engine 10.
During time from time t2 to t3, the control circuit 91 detects whether the engine 10 is in the accelerating condition or not, and it opens the solenoid valve 51 to supply the additional fuel when it is in the accelerating condition. In this manner, acceleration of the engine 10 is promoted. It is determined whether the engine 10 is in the accelerating condition or not by the control circuit 91 by periodically monitoring a variation value of the engine rotation speed per unit time. When the variation value of the engine rotation speed exceeds a previously-set threshold (predetermined value), the control circuit 91 determines that the engine 10 is in the accelerating condition so that the solenoid valve 51 is opened to additionally supply the fuel.
As described above, according to the present example, since the additional fuel supplying device 50 is provided separately from the carburetor 35, it is possible to supply fuel from the additional fuel supplying device 50 for the supplement, and thus to improve the startability of the engine 10. Since the engine rotation speed can be controlled by additionally supplying fuel from the additional fuel supplying device 50, it is possible to suppress the cost while achieving high functionality of the engine working machine 1. As illustrated in
In the foregoing, the present invention has been concretely described based on the example. However, it is needless to say that the present invention is not limited to the foregoing embodiment and various modifications and alterations can be made within the scope of the present invention. For example, the engine working machine has been explained as the brush cutter. However, not only the brush cutter but also other engine working machines such as a cutter, a chain saw, a lawn mower, and a cultivator may be adopted.
Hereinafter, each embodiment of the engine working machine and effects that can be obtained by each embodiment will be collectively described.
An engine working machine according to one embodiment is an engine working machine for driving a working tool using an engine including: a fuel tank; a carburetor for supplying an air-fuel mixture of air and fuel supplied from the fuel tank into a cylinder; a cylinder in which a piston is reciprocatable; and a crank case that holds the cylinder and that forms a crank chamber. The engine working machine is provided with an additional fuel supplying unit for supplying fuel to the engine separately from the carburetor, and a control unit for controlling an operation of the additional fuel supplying unit separately from supply of start-up fuel. In this manner, by the provision of the additional fuel supplying unit separately from the carburetor, it is possible to reduce costs of the engine working machine and to improve startability of the engine.
In an engine working machine according to another embodiment, the control unit supplies additional fuel from the additional fuel supplying unit in the start-up of the engine, and the control unit is provided with the maintenance mode for intermittently supplying additional fuel after a predetermined fuel supply by the additional fuel supplying unit. In this manner, the control unit determines whether the maintenance mode is required immediately after the start-up of the engine or not, and intermittently supplies the additional fuel after the predetermined fuel supply if the maintenance mode is required, so that it is possible to secure startability of the engine even when the carburetor is clogged. Even when it is difficult to maintain rotation of the engine immediately after the start-up of the engine due to the clogging of the carburetor, the fuel is continuously supplied from a fuel supplying route separately from the carburetor, and therefore, the rotation of the engine can be maintained. Further, by the rotation of the engine, clogging of the carburetor can be effectively eliminated by the negative pressure inside the cylinder. Note that the maintenance mode is executed during a predetermined period of time (period of time taken to reach duration, total engine rotation speed, and predetermined temperature) immediately after the start-up of the engine.
In an engine working machine according to another embodiment, the additional fuel supplying unit is provided at a flow path of fuel that is supplied from the fuel tank, and the additional fuel supplying unit has a solenoid valve for controlling fuel supply from the flow path to an air-intake path that extends from the carburetor into the cylinder. In this manner, it is possible to achieve a supply mechanism for additional fuel using a solenoid valve with a simple configuration.
In an engine working machine according to another embodiment, in the maintenance mode, the additional fuel supplying unit supplies additional fuel during “n” rotations (here, “m is larger than n”) of “m” rotations (here, “m is equal to or larger than 2”) of the engine. In this manner, in the maintenance mode, the minimum amount of fuel as much as the engine is not stopped can be supplied.
In an engine working machine according to another embodiment, in the maintenance mode, the additional fuel supplying unit supplies additional fuel for one rotation of “m” rotations (here, “m is equal to or larger than 2”) of the engine. In this manner, in the maintenance mode, the fuel flow rate after start-up of the engine can be set to an optimal value.
In an engine working machine according to another embodiment, in the maintenance mode, the additional fuel supplying unit supplies, to the air-intake path, additional fuel whose amount is less than that of the fuel supply used until the start-up of the engine. In this manner, it is possible to prevent misfire of the engine immediately after start-up.
An engine working machine according to another embodiment is provided with a switch for setting the maintenance mode, and the control unit shifts the condition to the control by the maintenance mode when the switch is turned ON. In this manner, it is possible to reliably execute operation in the maintenance mode with decision of the operator.
An engine working machine according to another embodiment is provided with a rotation-speed detecting unit for detecting the rotation speed of the engine, and the control unit determines whether to shift to the maintenance mode or not based on the engine rotation speed at the start-up of the engine or after the start-up. In this manner, the control unit determines whether to shift to the maintenance mode or not by detecting the engine rotation speed during the start-up control mode or after the start-up control mode. Accordingly, when the rotation speed of the engine decreases down to a predetermined rotation speed or lower after the start-up, it is possible to automatically supply fuel from the solenoid valve through a route different from the carburetor by the maintenance mode. In this manner, it is possible to automatically detect failure of the carburetor and to effectively eliminate the clogged condition of the carburetor.
An engine working machine according to another embodiment is provided with a timer unit for counting stop time of the engine, and the control unit measures the time during which the engine stops by using the timer unit, and shifts the condition to the maintenance mode when the stop time exceeds a predetermined value. In this manner, it is possible to largely improve the startability of the engine after the engine working machine is stored for a long time, and to eliminate clogging of the carburetor.
An engine working machine according to another embodiment is provided with a temperature detecting unit for detecting a temperature of the engine or of outside air, and with a rotation-speed detecting unit for detecting the rotation speed of the engine, and the control unit controls the amount of fuel to be added in accordance with the temperature detected by the temperature detecting unit, and fuel is supplied from the additional fuel supplying unit when the rotation speed of the engine decreases down to a predetermined rotation speed or lower after the start-up of the engine. In this manner, the control unit adjusts the amount of fuel to be added in the start-up in accordance with the detected temperature, and fuel is supplied from the additional fuel supplying unit when the rotation speed of the engine decreases down to a predetermined rotation speed or lower after start-up of the engine. Accordingly, it is possible to stably perform the start-up regardless of the outside air temperature or the engine temperature, and it is also possible to effectively prevent the engine stop immediately after the start-up.
An engine working machine according to another embodiment is provided with a rotation-speed detecting unit for detecting the rotation speed of the engine, and the control unit supplies additional fuel from the additional fuel supplying unit when the engine rotation speed that has been detected by the rotation-speed detecting unit exceeds a predetermined value. In this manner, it is possible to additionally supply fuel from the solenoid valve for thickening the concentration inside the cylinder even when the rotation (rotation speed or rotation-speed increasing rate) of the engine exceeds a predetermined value, so that the rotation of the engine can be controlled. In this manner, the additional fuel supplying unit can be functioned as an automatic choke function, and can be used also for the control of the rotation speed of the engine after the start-up.
In an engine working machine according to another embodiment, the additional fuel supplying unit is for supplying fuel to an air-intake path that extends from the carburetor to the cylinder, and has a solenoid valve, and the control unit controls opening and closing of the solenoid valve based on the rotation speed detected by the rotation-speed detecting unit. In this manner, it is possible to perform the control of the rotation speed of the engine using the different fuel supplying means from the carburetor. This solenoid valve is mainly for achieving the automatic choke function, and therefore, is for performing the rotation control in normal rotation using the automatic choke function from a different point of view.
In an engine working machine according to another embodiment, an insulator that forms the air-intake path is provided between the carburetor and the cylinder, and the additional fuel supplying unit is directly attached to the insulator or attached between the insulator and the carburetor via an attachment adaptor. In this manner, the present invention can be easily performed without changing the carburetor only by providing the attachment adaptor in a conventional engine working machine or by changing the insulator.
An engine working machine according to another embodiment is provided with a centrifugal clutch mechanism for connecting or interrupting transmission of output from the crank shaft of the engine to the working tool, and the control unit opens the solenoid valve so as to supply additional fuel when the rotation speed of the engine increases in the start-up of the engine to come close to the connection rotation speed of the centrifugal clutch mechanism. In this manner, it is possible to suppress the increase in the rotation speed due to thinning of fuel concentration immediately after start-up of the engine, and to prevent unexpected operations of the working tool such as unexpected rotation of a distal end blade due to clutch coupling.
In an engine working machine according to another embodiment, the control unit monitors the idling rotation speed during time taken from start-up of the engine until elapse of predetermined time, and additional fuel is supplied from the solenoid valve when the rotation speed of the engine is a predetermined threshold or higher. In this manner, it is possible to prevent unexpected coupling of the centrifugal clutch.
In an engine working machine according to another embodiment, the control unit opens the solenoid valve so as to supply additional fuel when the engine is in an excess rotation condition so as to exceed the maximum output rotation speed. In this manner, it is possible to reliably prevent further increase in the rotation from the excess rotation condition, to achieve improvement in fuel efficiency and suppression in oscillation and noise, and also to prevent shortening of the life of the engine.
In an engine working machine according to another embodiment, the control unit detects whether the engine is in an accelerating condition or not, and opens the solenoid valve when it is in the accelerating condition so as to supply additional fuel and thus to promote acceleration. In this manner, it is possible to eliminate shortage of fuel in the acceleration and to improve acceleration of the engine.
In an engine working machine according to another embodiment, the control unit additionally supplies fuel from the solenoid valve when a variation value of the rotation speed per unit time detected by the rotation-speed detecting unit exceeds a previously-set predetermined value. In this manner, it is possible to reliably detect whether the engine is in the accelerating condition or not, and to improve acceleration.
An engine working machine according to another embodiment has a rotation detecting coil in which power is generated by the rotation of the engine, and a storage unit for storing power that is generated by the rotation detecting coil, and the control unit is periodically activated by the power of the storage unit, and the control unit interrupts its own power source upon elapse of predetermined time after the activation. In this manner, it is possible to suppress battery consumption.
Number | Date | Country | Kind |
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2012-250223 | Nov 2012 | JP | national |
2013-017973 | Jan 2013 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2013/006684 | 11/13/2013 | WO | 00 |