JP2010096017A - Engine control circuit for working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure the function of a hydraulic lock lever and an engine stop switch with a simple configuration in a control circuit controlling the start and operation condition of an engine in relation with an engine control circuit for a working machine. <P>SOLUTION: The engine control circuit includes a starter motor 3 starting the engine, a neutral start relay 4 connecting a controlled side circuit 4b by energization to a controlling side circuit 4a and selecting whether the starter motor 3 is to be operated, a coil power source 5 which is a control power source of the neutral start relay 4, and a first electric circuit 6 connecting the controlling side circuit 4a of the neutral start relay 4 and the coil power source 5. A neutral limit switch 7 and a second shutdown switch 8 are interposingly mounted in series on the first electric circuit 6 and the first electric circuit 6 is connected/disconnected according to the operating position of the hydraulic lock lever 1 and the engine stop switch 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine control circuit for a work machine provided with a button for stopping an engine in addition to a hydraulic lock lever and a key switch for locking the operation of hydraulic equipment of the work machine.

An engine emergency stop button and a hydraulic lock lever are provided in a cab of a conventional work machine as a safety device for stopping the operation of the work machine in an emergency.
For example, Patent Document 1 describes a safety device that detects an error that requires an emergency stop of a work machine with an error monitor and performs control to make an engine stop emergency with an engine stop solenoid. With this technology, not only when the error monitor detects an error spontaneously but also when the operator operates the engine stop switch, the engine stop solenoid can be operated to stop the engine. Yes.

Patent Document 2 discloses a technique for cutting off the supply of pressure oil to the hydraulic actuator by changing the hydraulic lock lever provided on the driver's seat of the work machine from the unlocked posture to the locked posture. . In this technology, the hydraulic actuator is permitted to operate while the hydraulic lock lever is operated to the unlocked position, and the engine start (when stopped) is prohibited, while the hydraulic lock lever is operated to the locked position. In this state, the operation of the hydraulic actuator is prohibited and the engine is allowed to start. That is, by adopting a mechanism in which the engine is started only in a state where the hydraulic system is locked, a problem that the work machine unexpectedly operates immediately after the engine is started is prevented.
Japanese Patent Laid-Open No. 10-47094 JP 2000-54436 A

  By the way, the emergency stop control of the engine by the engine stop switch and the start control of the engine by the hydraulic lock lever are common in the function of stopping the engine (holding the stopped state). Therefore, it is conceivable that the respective control circuits are not provided independently, but the circuits are partially shared. Specifically, it is a control circuit as shown in FIG.

The control circuit 30 includes a control circuit that controls the starter motor 23 of the engine and the fuel supply solenoid 33 that supplies fuel to the engine according to the operation states of the hydraulic lock lever 21, the engine stop switch 22, and the engine key switch 29. It is shown.
The neutral limit switch 27 is a one-circuit one-contact type switch that connects and disconnects the circuit according to the operation position of the hydraulic lock lever 21. Here, it is assumed that the circuit is connected when the hydraulic lock lever 21 is operated to the locked position, and is disconnected when the hydraulic lock lever 21 is operated to the unlocked position. The circuit in which the neutral limit switch 27 is interposed is connected to a coil of a control side circuit 24a of the neutral start relay 24 described later.

  The second shutdown switch 28 is a one-circuit two-contact slide switch that is switched according to the on / off state of the engine stop switch 22. Of the two contacts selected by the second shutdown switch 28, one corresponding to the OFF position is connected to the fuel supply solenoid 33. In other words, if this contact point is selected, the engine starts and operates. Further, a circuit that continues to a coil of a control side circuit 24a of the neutral start relay 24 described later is formed on the other contact side corresponding to the ON position.

The key switch 29 is a general engine key switch that switches between starting and stopping the engine by inserting and rotating the engine key. FIG. 7 illustrates the case where a two-circuit, three-contact slide switch is used.
The starter motor 23 is connected to a starter power source 32 as a power source via a start relay 31. The start relay 31 is a relay having a function of closing (connecting) the controlled side circuit 31b when a coil interposed in the control side circuit 31a is excited. When the coil of the control side circuit 31a is not excited, the circuit of the controlled side circuit 31b is opened (disconnected) to prohibit the operation of the starter motor 23.

  Further, a neutral start relay 24 is interposed on a circuit connecting the key switch 29 and the coil of the control side circuit 31a of the start relay 31. The neutral start relay 24 is activated when the neutral limit switch 27 is joined or when the other contact point of the engine stop switch 22 is selected, and the coil of the control side circuit 24a is excited. 31 has a function of disconnecting the controlled side circuit 24b connected to the control side circuit 31a. As shown in FIG. 7, the neutral limit switch 27 and the second shutdown switch 28 are connected in parallel to the neutral start relay 24.

  That is, when the hydraulic lock lever 21 is operated to the unlock position or when the engine stop switch 22 is operated to the on position, the coil of the control side circuit 24a of the neutral start relay 24 is excited. Therefore, even if the key switch 29 is operated to the start position, the coil of the control side circuit 31a of the start relay 31 cannot be excited, and the starter motor 23 is not activated. Therefore, restart of the stopped engine can be prevented.

  On the other hand, when the hydraulic lock lever 21 is operated to the locked position and the engine stop switch 22 is operated to the off position, the coil of the control side circuit 24a of the neutral start relay 24 is in a non-excited state. When the key switch 29 is operated to the start position, the coil of the control side circuit 31a of the start relay 31 is excited and the starter motor 23 is activated. Therefore, the engine can be started.

As described above, the neutral limit switch 27 and the second shutdown switch 28 are connected in parallel to the neutral start relay 24 that selects whether the starter motor 23 can be operated. The engine can be started and controlled in accordance with the operation state of the switch 22.
However, if the neutral limit switch 27 and the second shutdown switch 28 are connected in parallel, the circuit is closed on the upstream side of the neutral start relay 24 when both switches 27 and 28 are connected to the circuit. In order to secure the difference, it is necessary to rectify the diode 35 on the circuit. In addition, there is a problem that the configuration of the entire circuit is somewhat complicated and the cost cannot be reduced.

  The present invention has been made in view of such problems, and in a control circuit for controlling engine start and operation states, the functions of a hydraulic lock lever and an engine stop switch can be secured with a simple configuration. An object of the present invention is to provide an engine control circuit for a work machine.

  In order to achieve the above object, the engine control circuit of the work machine according to the first aspect of the present invention is switchable between a lock position for blocking pressure oil supply to the hydraulic actuator and a lock release position for allowing the pressure oil supply. An engine control circuit for a work machine having a hydraulic lock lever provided on the engine and an engine stop switch for emergency stop of the engine, a starter motor for supplying driving force when starting the engine, a control side circuit, and a controlled circuit A neutral start relay having a side circuit, connecting the controlled side circuit by energizing the control side circuit, and selecting whether or not the starter motor can be driven, and a coil serving as a control power source for the neutral start relay A power source, a first electric circuit connecting the control side circuit and the coil power source in the neutral start relay, A neutral limit switch interposed on one electric circuit and connecting / disconnecting the first electric circuit according to an operation position of the hydraulic lock lever, and closer to the coil power source than the neutral limit switch on the first electric circuit And a second shutdown switch that connects and disconnects the first electric circuit according to the operating position of the engine stop switch, and the neutral limit switch and the second shutdown switch are connected in series on the first electric circuit. It is characterized by being.

The neutral limit switch and the second shutdown switch only need to function as a so-called on / off switch of at least one circuit and one contact type. For example, a part of a multi-circuit multi-contact slide switch can be used as an on / off switch.
The neutral start relay, the main relay, and the start relay are configured as general relays having a coil in the control side circuit and connecting or disconnecting the controlled side circuit by excitation of the coil. The correspondence between the excitation state of the coil and the connection / disconnection state on the controlled circuit side is arbitrary.

  An engine control circuit for a work machine according to a second aspect of the present invention, in addition to the configuration according to the first aspect, is provided separately from the engine stop switch, and the neutral limit switch and the An engine key switch connected in series with a second shutdown switch, and a second electric circuit for connecting the coil power supply and the controlled circuit of the neutral start relay when the engine key switch is operated to a start position Is further provided.

  An engine control circuit for a work machine according to a third aspect of the present invention branches from between the neutral limit switch and the second shutdown switch on the first electric circuit in addition to the configuration according to the first or second aspect. The formed branch circuit, a fuel control solenoid that controls the amount of fuel injection supplied to the engine, and a fuel control solenoid that is installed on the branch circuit and selects whether the fuel control solenoid can be driven by energizing the branch circuit. And a main relay.

  An engine control circuit for a work machine according to a fourth aspect of the present invention includes, in addition to the configuration according to any one of the first to third aspects, a starter power source that is a drive power source for the starter motor, and the starter motor. A starter circuit connecting between the motor and the starter power supply, and a start relay interposed on the starter circuit, and the neutral start relay excites the coil of the start relay when the control side circuit is energized. And the starter motor is connected to operate.

According to the engine control circuit (claim 1) of the working machine of the present invention, the neutral start relay can be accurately driven with a simple configuration by connecting the neutral limit switch and the second shutdown switch in series. For example, the diode can be omitted as compared with the case where they are connected in parallel.
According to the engine control circuit for a work machine of the present invention (Claim 2), when the key switch is operated to the start position in a state where the neutral limit switch and the second shutdown switch are connected together. In addition, the starter motor is operated by the neutral start relay. If either the neutral limit switch or the second shutdown switch is disconnected, the starter motor does not operate even if the key switch is operated to the start position.

  According to the engine control circuit of the work machine of the present invention (Claim 3), a neutral circuit is formed by controlling the fuel control solenoid by forming a branch circuit from the downstream side of the second shutdown switch on the first electric circuit. Regardless of the operation state of the relay, the fuel injection amount of the engine can be controlled. For example, even if the neutral limit switch is disconnected during operation of the engine, the operation of the engine (that is, idle operation) can be continued.

  Further, according to the engine control circuit of the work machine of the present invention (claim 4), the circuit for supplying electric power to the starter motor and the circuit for controlling the operation of the starter motor can be separated.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 5 are diagrams for explaining an engine control circuit of a work machine according to an embodiment of the present invention, and FIG. 1 is a circuit diagram schematically showing the overall configuration of the engine control circuit. FIG. 4 is a circuit diagram schematically showing the energization state of the engine control circuit, where (a) shows a state at the time of normal engine start, and (b) shows a state in which the engine start is prohibited by a hydraulic lock lever. It is. 3 is also a circuit diagram schematically showing the energization state of the engine control circuit as in FIG. 2, wherein (a) is a state where the key switch is turned off, and (b) is a state where the engine is stopped by the engine stop switch. This shows a state where starting is prohibited.

  FIG. 4 is a perspective view schematically showing a cab of a hydraulic excavator to which the engine control circuit is applied, and FIG. 5 is a perspective view showing an overall configuration of the hydraulic excavator. FIG. 6 is a circuit diagram illustrating an engine control circuit as a modification of the present invention. FIG. 6A is a circuit diagram in which the periphery of the starter motor of the circuit shown in FIG. 1 is changed, and FIG. 6B is a circuit diagram shown in FIG. It is the circuit diagram which changed the surroundings of the fuel supply solenoid of a circuit.

[1. overall structure]
The engine control circuit according to the present invention is applied to a hydraulic excavator 40 shown in FIG.
The hydraulic excavator 40 includes a lower traveling body 41 equipped with a crawler type traveling device, and an upper revolving body 42 that is rotatably mounted on the lower traveling body 41. A working device 43 such as a boom and an arm and a cab 44 on which an operator rides are provided on the front side of the upper swing body 42, and a counterweight having a shape along the wall surface is provided at the rear end portion of the upper swing body 42. 45 is provided. An engine room 46 is provided immediately before the counterweight 45. Inside the engine room 46, an engine 47 that is a drive source of the excavator 40 is disposed.

As shown in FIG. 4, an operating lever for driving a working device such as a boom or an arm mounted on the hydraulic excavator and a seat 48 on which an operator is seated are provided inside the cab 44. A hydraulic lock lever 1, an engine stop switch 2 and a key switch 9 are fixed below the seat 48.
The hydraulic lock lever 1 is a safety device for cutting off (locking, that is, temporarily stopping) the supply of pressure oil to various hydraulic actuators mounted on the excavator 40 or allowing the supply of pressure oil. . The hydraulic lock lever 1 is pivotally attached to the console on the side of the seat 48 so that the unlocked posture and the locked posture can be taken, and can be transformed into two kinds of positions. It has become. Of these deformed positions, as shown in FIG. 4, the position lowered downward is called a lock position, and the position horizontally lifted forward of the console is called a lock release position. In the hydraulic excavator 40, when the hydraulic lock lever 1 is in the locked position lowered, the pilot pressures of the operation levers corresponding to all the hydraulic actuators provided in the work device 43, the lower traveling body 41, and the like are locked. It has come to be. Further, when the hydraulic lock lever 1 is lifted and is in the unlocked position, the supply of pressure oil is allowed and the pilot pressure is transmitted to each hydraulic actuator. With such a mechanism, for example, even if an operator accidentally touches the operation lever when getting on and off, the working device 43 is not unexpectedly operated if the hydraulic lock lever 1 is lowered.

  Further, when the hydraulic lock lever 1 is in the unlocked position, the stopped engine 47 cannot be started. That is, the engine 47 is started only in a state where the hydraulic lock lever 1 is in the locked position where it is lowered. As described above, this mechanism prevents malfunction of the hydraulic actuator when the engine 47 is started.

  The engine stop switch 2 is an on / off switch for urgently stopping the engine 47. The engine stop switch 2 is fixed to the entrance side (the right side in FIG. 4) at the bottom of the seat 48 so that the hand can be reached from the outside of the cab 44. It is installed. As means for stopping the engine 47, two types of means, that is, the key switch 9 used during normal stop and the engine stop switch 2 are provided. In this embodiment, when the engine stop switch 2 is turned on, the operating engine 47 is stopped and starting (restarting) is prevented.

  The key switch 9 is a so-called ignition key switch that can start and stop the engine by inserting and rotating the engine key. The key switch 9 is operated at the off position corresponding to the stop state of the engine 47 and when the engine 47 is started. A plurality of operation positions are provided, such as a start position, an on position that is a position during engine operation after start (for example, after a complete explosion), and an accessory position that energizes only electrical components. Hereinafter, in the present embodiment, focusing on the operation of the engine 47, a two-circuit, three-contact type slide switch having three positions of an off (OFF) position, a start (ST) position, and an on (ON) position as the key switch 9 However, it should be noted that the type and number of operation positions are not limited to this.

[2. Circuit configuration]
The engine control circuit 10 according to the present invention will be described in detail. As shown in FIG. 1, the engine control circuit 10 includes a starter motor 3 that supplies a driving force when the engine 47 is started, a neutral start relay 4 that selects whether the starter motor 3 can be driven, and its control A power source 5 (coil power source) that is a power source is provided, and a neutral limit switch 7 and a second shutdown switch 8 that operate according to respective operation positions of the hydraulic lock lever 1 and the engine stop switch 2 are configured. .

The power source 5 has a function as a control power source for exciting the coil of the neutral start relay 4. Hereinafter, the circuit connecting the coil of the neutral start relay 4 and the power source 5 is referred to as the first electric circuit 6.
The neutral start relay 4 includes a control side circuit 4a and a controlled side circuit 4b in which a coil is interposed. When the coil is excited by energization of the control side circuit 4a, the controlled side circuit 4b is turned on. It is a relay to be connected. A first electric circuit 6 is connected to the control side circuit 4a. On the other hand, a circuit connected to the controlled circuit 4b is referred to as a second electric circuit 15. The neutral start relay 4 receives an exciting current from the first electric circuit 6 connected to the control side circuit 4a, and connects the second electric circuit 15 connected to the controlled side circuit 4b to energize it. Thus, the starter motor 3 is operated. On the other hand, in a state where some part of the first electric circuit 6 is opened (cut), the second electric circuit 15 is not energized and the starter motor 3 does not operate. Therefore, the neutral start relay 4 functions to select whether or not the starter motor 3 can be driven according to the energization state of the first electric circuit 6.

On the first electric circuit 6, a neutral limit switch 7 and a second shutdown switch 8 are arranged in series.
The neutral limit switch 7 is a one-circuit one-contact type that opens (cuts) the circuit when the hydraulic lock lever 1 is operated to the unlocked position and closes (connects) when the hydraulic lock lever 1 is operated to the locked position. On / off switch. Similarly, the second shutdown switch 8 is also a one-circuit one-contact type that opens (disconnects) the circuit when the engine stop switch 2 is turned on and closes (connects) the circuit when it is operated to the off position. This is an on / off switch. For example, when the operator wants to stop the engine 47 urgently, the engine stop switch 2 is turned on.

  Between the second shutdown switch 8 and the power supply 5 on the first electric circuit 6, the key switch 9 is interposed. Specifically, one system from the power source 5 is connected to the input side of the key switch 9, while two systems of the first electric circuit 6 and the second electric circuit 15 are connected to the output side. When the key switch 9 is operated to the start position, both the first electric circuit 6 and the second electric circuit 15 are closed (connected) and then automatically turned on by a built-in biasing means such as a spring (not shown). It is configured to move to the position and close (connect) only the first electric circuit 6 or to open (disconnect) both the first electric circuit 6 and the second electric circuit 15 when operated to the off position. Yes.

The second electric circuit 15 is a circuit connected to the controlled side circuit 4b in the neutral start relay 4 and operates the starter motor 3 connected to the control side circuit 11a in the start relay 11 described later. It is a circuit for.
The engine control circuit 10 is provided with a starter power supply 12 as a drive power supply for the starter motor 3. Note that the power supply 5 may be used instead of the starter power supply 12. Here, a circuit that connects the starter power supply 12 and the starter motor 3 is referred to as a starter circuit 16. A start relay 11 is interposed on the starter circuit 16. Similarly to the neutral start relay 4, the start relay 11 includes a control side circuit 11a and a controlled side circuit 11b. When the coil is excited by energizing the control side circuit 11a, the controlled side circuit 11b is To connect.

  The aforementioned second electric circuit 15 is connected to the control side circuit 11a of the start relay 11, and the starter circuit 16 is connected to the controlled side circuit 11b. As a result, when the second electric circuit 15 is energized, the start relay 11 closes (connects) the starter circuit 16 and operates the starter motor 3. That is, in this case, the stopped engine 47 is started (restarted).

  A branch circuit 17 is branched from the neutral limit switch 7 and the second shutdown switch 8 in the first electric circuit 6. The branch circuit 17 is connected to the main relay 14. Similarly to the start relay 11, the main relay 14 includes a control side circuit 14a and a controlled side circuit 14b. When the coil is excited by energizing the control side circuit 14a, the controlled side circuit 14a is also provided. 14b is connected. The branch circuit 17 is connected to the control side circuit 14a. On the other hand, on both sides of the controlled-side circuit 14b, lines that are branched from the power source 5 and communicate with the fuel supply solenoid (solenoid valve) 13 are connected. The fuel supply solenoid 13 has a function of receiving fuel supplied from the power source 5 and supplying fuel to the engine 47. Thus, when the fuel supply solenoid 13 is energized, fuel is constantly supplied to the engine 47 so that the operation of the engine 47 is continued.

[3. Control action]
[A. Normal engine start]
FIG. 2A schematically shows an energized state of the engine control circuit 10 at the time of normal engine start. Hereinafter, in FIGS. 2 (a) and 2 (b) and FIGS. 3 (a) and 3 (b), energized lines are indicated by bold lines. The normal engine start here is a case where the following conditions are satisfied.
・ Hydraulic lock lever 1 is operated to the locked position ・ Engine stop switch 2 is operated to the off position ・ Key switch 9 is operated to the start position

  In this case, since the neutral limit switch 7 and the second shutdown switch 8 are both closed (connected), the power from the power source 5 is supplied to the control side circuit 4a of the neutral start relay 4 through the first electric circuit 6. The As a result, the coil of the neutral start relay 4 is excited, and the controlled circuit 4b is closed (connected). Furthermore, the power supplied to the second electric circuit 15 by the operation of the key switch 9 to the start position is also supplied to the control side circuit 11a of the start relay 11, and the controlled side circuit 11b of the start relay 11 is also controlled. Closed (connected). Therefore, the starter power supply 12 and the starter motor 3 are connected, and the engine 47 is started.

  Even if the key switch 9 is moved to the ON position, energization to the first electric circuit 6 is ensured, so that power from the power source 5 is supplied to the control side circuit 14a of the main relay 14 via the branch circuit 17. Is done. Thereby, the coil of the main relay 17 is excited and the controlled circuit 14b is closed (connected). Accordingly, the power source 5 and the fuel supply solenoid 13 remain connected, and the engine 47 continues to operate and enters an idling state.

[B. When hydraulic lock lever is operated to unlock position]
FIG. 2B shows the energization state of the engine control circuit 10 when the engine 47 is to be started with the hydraulic lock lever 1 being operated to the unlock position. Here, it is assumed that the following conditions are satisfied.
・ Hydraulic lock lever 1 is operated to unlock position ・ Engine stop switch 2 is operated to OFF position ・ Key switch 9 is operated to start position In this case, the second shutdown switch 8 is closed (connected) However, the neutral limit switch 7 is opened (disconnected). Thereby, the neutral start relay 4 is not excited, and the power supply to the control side circuit 11a of the start relay 11 is also cut off. Therefore, the starter circuit 16 is cut off and the engine 47 is not started.

  Note that, as an energized state similar to this, a case where the key switch 9 is operated to the on position can be considered. That is, this is a case where the hydraulic lock lever 1 is operated to the unlock position while the engine 47 is in operation. In such a case, since the power supply to the main relay 17 via the branch circuit 17 is continued, the operation of the engine 47 is maintained as it is.

[C. When the key switch is moved to the off position]
FIG. 3A shows the energized state when the key switch 9 is operated to the off position during the operation of the engine 47. Here, it is assumed that the following conditions are satisfied.
The hydraulic lock lever 1 is operated to the locked position. The engine stop switch 2 is operated to the off position. The key switch 9 is operated to the off position. In this case, the neutral limit switch 7 and the second shutdown switch 8 are operated. Regardless of the operation state, both the first electric circuit 6 and the second electric circuit 15 are opened (disconnected). Therefore, the start relay 11 does not operate and the engine 47 does not start.

  Further, when the key switch 9 is operated from the on position to the off position, the power supply to the main relay 17 via the branch circuit 17 is cut off, so that the controlled side circuit 14b of the main relay 14 is The fuel supply by the fuel supply solenoid 13 is stopped. Therefore, the engine 47 is stopped. That is, the engine 47 can be stopped by turning off the general key switch 9.

[D. When the engine stop switch is operated to the on position]
FIG. 3B shows the energization state of the engine control circuit 10 when the engine 47 is to be started with the engine stop switch 2 being operated to the on position. Here, it is assumed that the following conditions are satisfied.
• The hydraulic lock lever 1 is operated to the locked position.
The engine stop switch 2 is operated to the on position. The key switch 9 is operated to the start position. In this case, the second shutdown switch 8 is opened (disconnected), and the neutral start relay 4 is not excited. 11, the power supply to the control side circuit 11a is cut off. Therefore, the starter circuit 16 is cut off and the engine 47 is not started.

  Further, as an energized state similar to this, there may be a case where the engine stop switch 2 is operated to the on position while the key switch 9 is operated to the on position (while the engine 47 is in operation). As shown in FIG. 3B, when the second shutdown switch 8 is opened (disconnected), the energization to the branch circuit 17 is also cut off, so that the main relay 14 is not excited and is supplied to the fuel supply solenoid 13. Is interrupted. Therefore, the fuel supply by the fuel supply solenoid 13 is stopped and the engine 47 is stopped. That is, regardless of the operation position of the hydraulic lock lever 1, the engine 47 can be stopped by pressing the engine stop switch 2.

[E. Correspondence between starting conditions and control details]
Table 1 shows a correspondence relationship between the operation positions of the hydraulic lock lever 1, the engine stop switch 2 and the key switch 9 set in the hydraulic excavator 40 and the state of the engine 47.
Regarding the operation during the operation of the engine 47, the engine 47 stops when the engine stop switch 2 is operated to the ON position or when the key switch 9 is operated to the OFF position. The engine 47 is not stopped by the operation of the hydraulic lock lever 47.

  On the other hand, regarding the operation at the start of the engine 47 that is stopped, the hydraulic lock lever 1 is in the lock position, the engine stop switch 2 is operated in the off position, and the key switch 9 is operated in the start position. The engine 47 will be started only when it is done.

  When the functions of the electric circuits in the engine control circuit 10 are summarized, the first electric circuit 6 can be said to be an electric circuit having a function of operating the starter motor 3 when the engine start condition is satisfied. On the other hand, the second electric circuit 15 can be said to be an electric circuit responsible for driving the starter motor 3 that is necessary only when the engine 47 is started. The branch circuit 17 is an electric circuit having a function of supplying fuel to the engine 47 and maintaining the operation state. The starter circuit 16 is an electric circuit that actually supplies driving power to the starter motor 3.

[4. effect]
According to the engine control circuit 10, the first electric circuit 6 has a simple configuration in which the limit switch 7, the second shutdown switch 8, and the key switch 9 related to the engine start condition are arranged in series on the first electric circuit 6. As a result, it is possible to reliably grasp that the start condition of the engine 47 is satisfied, and the stopped engine 47 can be started. Thus, the neutral start relay 4 can be accurately driven with a simple configuration.

Further, compared with a control circuit as shown in FIG. 7 (that is, a circuit in which the neutral limit switch 7 and the second shutdown switch 8 are connected in parallel to the neutral start relay 4), the rectifying diode 35 is not required. In addition, the entire electric circuit configuration can be simplified, and the cost can be reduced.
Further, the branch circuit 17 is formed from the downstream side of the second shutdown switch 8 on the first electric circuit 6 to control the operation of the fuel supply solenoid 13, so that the engine 47 can be operated regardless of the operation state of the neutral limit switch 7. The fuel injection amount can be controlled. For example, even if the hydraulic lock lever 1 is operated during the operation of the engine 47, the operation of the engine 47 (that is, idle operation) can be continued.

  In this embodiment, since the key switch 9 is also connected in series to the first circuit 6, the starter motor 3 can be easily controlled according to the operation state of the key switch 9. For example, when the neutral limit switch 7 and the second shutdown switch 8 are both connected and the key switch 9 is operated to the start position, the neutral start relay 4 is excited and the starter motor 3 is activated. If one of the neutral limit switch 7 and the second shutdown switch 8 is disconnected, the starter motor 9 does not operate even if the key switch 9 is operated to the start position.

  In addition, since the key switch 9 is interposed upstream of the second shutdown switch 8 (that is, between the power supply 5 and the second shutdown switch 8), when the key switch 9 is turned off while the engine 47 is in operation. The engine 47 can be stopped by interrupting the energization of the branch circuit 17. Thus, it can be set as a structure which does not have trouble in a function as a general engine key switch.

  In addition, since the start relay 11 is interposed on the starter circuit 16 for driving the starter motor 3, the operation of the starter motor 3 is controlled by exciting the start relay 11. The power supply circuit and the control circuit of the starter motor 3 can be separated.

[5. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, the correspondence between the presence / absence of energization of the control side circuits 4a, 11a, and 14a in the neutral start relay 4, the start relay 11, and the main relay 14 and the connection / disconnection state of the controlled side circuits 4b, 11b, and 14b is As long as the function described in Table 1 is fulfilled, it may be changed as appropriate. For example, the neutral start relay 4 is configured to disconnect the controlled side circuit 4b when the control side circuit 4a is energized, and the start relay 11 is configured to connect the controlled side circuit 11b when the control side circuit 11a is not energized. If the configuration is such that the power of the starter power supply 12 is supplied to the starter circuit 16 only when the key switch 9 is operated to the start position, an engine control circuit having the same effects as in the above-described embodiment can be achieved. .

There are two types of relays with different combinations of connection and disconnection states of the control side circuit and the controlled side circuit. Therefore, a combination of a plurality of relays can be changed as appropriate.
In the above-described embodiment, the power source 5 and the starter power source 12 are provided separately. However, if conditions such as a necessary voltage required for the starter motor 3 are not taken into consideration, the power of the starter motor 3 is supplied to the power source 5. It can be considered that the configuration is introduced from the above.

  In this case, as shown in FIG. 6A, the start relay 11 may be omitted, and the neutral start relay 4 may directly select whether or not the starter motor 3 can be operated. Here, by arranging the starter motor 3 on the second electric circuit 15 in the above-described embodiment, the functions described in Table 1 above can be ensured, and the same effects as the above-described embodiment. Will be played.

Alternatively, as shown in FIG. 6B, the main relay 14 may be omitted and the fuel injection solenoid 13 may be disposed on the branch circuit 17. Even in such a circuit, the same effects as those of the above-described embodiment can be obtained.
It is also conceivable that the key switch 9 and the second electric circuit 15 are removed from the engine control circuit 10 by using a known technique for controlling the start and stop of the engine 47 with the key switch 9. That is, the control circuit of the engine 47 by the key switch 9 and the control circuit of the engine 47 by the neutral limit switch 7 and the second shutdown switch 8 may be separated and controlled in a double manner.

  Further, in the above-described embodiment, the electric component arrangement structure is applied to the hydraulic excavator 40. However, the application target of the present invention is not limited to this, and the hydraulic lock lever 1 such as a crane device or a wheel loader is used. In addition, the present invention can be applied to all work machines provided with an emergency engine stop switch 2.

It is a circuit diagram showing typically the whole composition of the engine control circuit of the working machine concerning one embodiment of the present invention. It is a circuit diagram which shows typically the energized state of the engine control circuit of the working machine which concerns on one Embodiment of this invention, (a) shows the state at the time of normal engine starting, (b) is an engine by a hydraulic lock lever. This shows a state in which the starting is prohibited. It is a circuit diagram showing typically the energized state of the engine control circuit of the work machine concerning one embodiment of the present invention, (a) shows the state where the key switch was turned off, and (b) shows the engine by the engine stop switch. This shows a state in which the starting is prohibited. 1 is a perspective view schematically showing a cab of a hydraulic excavator to which an engine control circuit for a work machine according to an embodiment of the present invention is applied. 1 is a perspective view showing an overall configuration of a hydraulic excavator to which an engine control circuit for a work machine according to an embodiment of the present invention is applied. FIG. 2 is a circuit diagram illustrating an engine control circuit of a work machine as a modification of the present invention, in which (a) is a circuit diagram in which the periphery of the starter motor 3 of the circuit shown in FIG. FIG. 5 is a circuit diagram in which the periphery of a fuel supply solenoid 13 is changed. It is the circuit diagram illustrated as an engine control circuit of the conventional working machine.

Explanation of symbols

1 Hydraulic lock lever 2 Engine stop switch 3 Starter motor 4 Neutral start relay 5 Power supply (coil power supply)
6 First Electric Circuit 7 Neutral Limit Switch 8 Second Shutdown Switch 9 Key Switch 10 Engine Control Circuit 11 Start Relay 12 Starter Power Supply 13 Fuel Supply Solenoid 14 Main Relay 15 Second Electric Circuit 16 Starter Circuit 17 Branch Circuit

Claims (4)

A work machine comprising a hydraulic lock lever that is switchable to a lock position that interrupts the supply of pressure oil to the hydraulic actuator, and a lock release position that allows the supply of pressure oil, and an engine stop switch that stops the engine urgently In the engine control circuit of
A starter motor for supplying driving force when starting the engine;
A neutral start relay having a control side circuit and a controlled side circuit, connecting the controlled side circuit by energizing the control side circuit, and selecting whether or not to drive the starter motor;
A coil power source that is a power source for controlling the neutral start relay;
A first electric circuit for connecting between the control side circuit and the coil power supply in the neutral start relay;
A neutral limit switch interposed on the first electric circuit and connecting / disconnecting the first electric circuit according to an operation position of the hydraulic lock lever;
A second shutdown switch that is interposed closer to the coil power source than the neutral limit switch on the first electric circuit, and connects and disconnects the first electric circuit according to the operation position of the engine stop switch,
An engine control circuit for a work machine, wherein the neutral limit switch and the second shutdown switch are connected in series on the first electric circuit. An engine key switch provided separately from the engine stop switch and connected in series with the neutral limit switch and the second shutdown switch on the first electric circuit;
2. The apparatus according to claim 1, further comprising a second electric circuit that connects the coil power source and the controlled circuit of the neutral start relay when the engine key switch is operated to a start position. The engine control circuit of the described working machine. A branch circuit formed by branching between the neutral limit switch and the second shutdown switch on the first electric circuit;
A fuel control solenoid for controlling a fuel injection amount supplied to the engine;
The work machine according to claim 1, further comprising: a main relay that is interposed on the branch circuit and that selects whether the fuel control solenoid can be driven by energizing the branch circuit. Engine control circuit. A starter power source that is a power source for driving the starter motor;
A starter circuit for connecting the starter motor and the starter power supply;
A start relay interposed on the starter circuit,
The neutral start relay is connected to excite a coil of the start relay to operate the starter motor when the control side circuit is energized. The engine control circuit of the work machine as described in the item.

Images