JPH0241334Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rotational speed control device for controlling the rotational speed of an internal combustion engine to a set level.

[Prior Art] As a rotational speed control device for an internal combustion engine, a deviation signal is obtained from a speed setting signal generated in accordance with the position of an accelerator operating member and a detection signal of the actual rotational speed, and the deviation signal is set to zero. Some systems control the supply of fuel to an internal combustion engine to ensure safety, and also stop the rotation of the engine if an abnormal condition occurs. As a rotational speed control device for an internal combustion engine that takes such safety measures, for example, the device described in Japanese Utility Model Application No. 58-9935 is known. FIG. 4 schematically shows the configuration of the device, in which 1 is an internal combustion engine, 2 is a speed detection circuit that detects the rotational speed (rpm) of the engine and outputs a speed detection signal Vn; 3 is an accelerator position detector that detects the position of the accelerator operating member, and 4 is a speed setting signal using the output of accelerator position detector 3 as input.
This is a speed setting signal output circuit that outputs Vno. 5
is an electric actuator that operates a means for adjusting the supply of fuel to the internal combustion engine, and this actuator is supplied with a drive current from the battery 6, and is used to adjust the injection amount of the fuel injection pump according to the magnitude of the drive current. Adjust the amount of fuel supplied to the engine by operating the valve (for diesel engines) or the butterfly valve of the carburetor (for gasoline engines). Reference numeral 7 denotes an actuator drive circuit consisting of a transistor Tr1, and this drive circuit causes a drive current of a predetermined magnitude to flow through the actuator 5 in response to a control signal Vd. Reference numeral 8 denotes an arithmetic circuit that receives the speed setting signal Vno and the speed setting signal Vn as input and outputs a control signal Vd for controlling the actuator drive circuit 7 so as to make the deviation between the actual rotational speed and the set rotational speed of the internal combustion engine zero. be.

Reference numeral 9 denotes a safety circuit that stops the engine when an abnormal condition occurs. This circuit receives, for example, a water temperature abnormality detection signal output by the water temperature sensor 10 when the temperature of the engine cooling water rises abnormally, and the engine lubricating oil level. The actuator drive circuit is configured to take as input the oil level abnormality detection detection signal outputted by the oil level sensor 11 when the oil level has decreased abnormally, and to reduce the drive current to the actuator 5 to zero when any of these abnormality detection signals is generated. 7 and engine 1
Stop the fuel supply to.

In the above-mentioned rotational speed control device for an internal combustion engine, the actuator 5 is configured to reduce to zero the deviation between the speed detection signal Vn indicating the rotational speed of the engine and the speed setting signal Vno indicating the set rotational speed determined by the position of the accelerator operating member. Since a driving current is applied to the engine, the rotational speed of the engine is controlled to maintain the speed set by the accelerator operating member. Furthermore, when the engine overheats or the oil level drops, the safety circuit 9 operates to stop the fuel supply to the engine, thereby stopping the engine and preventing the engine from operating in an abnormal state. .

In addition, as a control device that has the function of protecting the internal combustion engine from overspeeding, as shown in Japanese Patent Publication No. 53-45861, when the rotational speed of the internal combustion engine enters an abnormal range, the engine rotational speed adjustment element is activated. It is known that the operating function of the servo motor to be operated is canceled so that the internal combustion engine can thereafter be operated manually.

Furthermore, as shown in JP-A-58-126435, an overspeed prevention device for an internal combustion engine that controls the rotational speed of the internal combustion engine so that it does not exceed a speed limit is configured to prevent the internal combustion engine from exceeding a speed limit when the temperature of the internal combustion engine increases abnormally. It is also known that the engine is protected by lowering the set speed limit.

[Problems to be solved by the invention] According to the conventional device shown in Fig. 4, the engine stops immediately when an abnormal condition occurs, so the engine can be protected. In some cases, it may not be desirable to immediately stop the engine when an abnormality occurs. For example, when an engine is used as a power source for agricultural machinery such as a rice transplanter or a tractor, it is often impossible to repair the engine at the work site.
It is often necessary to drive the machine to a repair shop. Furthermore, in the case of marine engines, there is a risk of shipwreck if the engine suddenly stops at sea.

Furthermore, in the device shown in Japanese Patent Publication No. 53-45861,
Although it is possible to continue operation by manual operation in the event of an abnormality, this device does not have a means to limit the rotation speed to a safe range when operating by manual operation when an abnormality occurs. Incorrect operation may cause damage to the engine.

Furthermore, in a diesel engine, the engine is stopped by stopping the supply of fuel to the engine, so the movable range of the rotational speed adjustment element is set from a fuel cutoff position to a maximum supply amount position. In such a case, if the servo motor operation function is canceled when an abnormality occurs, as described in Japanese Patent Publication No. 53-45861, the fuel supply to the engine will be stopped and the engine will stop, making manual operation impossible. become unable.

Furthermore, as in JP-A No. 58-126435, if the rotation speed limit of the overspeed prevention device is lowered when an abnormality occurs, it is possible to continue operation by manual operation, but in this case, the following There are problems like this.

In other words, if the overspeed prevention device is configured to prevent overspeed by causing the engine to misfire when the speed exceeds the limit rotation speed, manual operation may not be performed effectively when the speed limit drops when an abnormality occurs. If this occurs, the engine may frequently misfire, causing unburned gas to burn in the muffler and causing an explosion sound, or the spark plug to become wet with unburned gas, causing a misfire and causing the engine to stop. There is. In addition, if the overspeed prevention device is configured to prevent overspeed by stopping the supply of fuel to the engine when the engine speed exceeds the limit rotation speed, it is prohibited to operate in a manner that exceeds the reduced limit rotation speed. In this case, a large engine brake is suddenly applied and then suddenly restored, resulting in extremely large rotational fluctuations, which is unfavorable from a safety standpoint.

The purpose of this invention is to reduce the rotational speed of the engine to a safe speed when an abnormal condition occurs, so that the engine can be operated without causing abnormalities such as explosion noise, ignition errors, and large rotational fluctuations. An object of the present invention is to provide a rotation speed control device for an internal combustion engine that can stably continue.

[Means for Solving the Problems] The present invention will be explained with reference to FIG. 1 showing an embodiment thereof. In the figure, 1 is an internal combustion engine, 2 is a speed detection circuit, and this detection circuit The rotational speed of the engine 1 is detected and a speed detection signal Vn is output.
3 is an accelerator position detector that detects the position of an accelerator operating member that sets the speed of the internal combustion engine 1, and 4 is an input that receives the output of the accelerator position detector 3 and outputs a speed setting signal Vno corresponding to the position of the accelerator operating member. This is a speed setting signal output circuit. 5 is an electric actuator that operates the means for adjusting the amount of fuel supplied to the engine 1; engine) to control the supply of fuel to engine 1. 7 is an actuator drive circuit, and this drive circuit adjusts the drive current of the actuator 5 by inputting the control signal Vd. 8 is an arithmetic circuit which receives the speed setting signal Vno and the speed detection signal Vn and controls the actuator drive circuit 7 so as to make the deviation between the actual rotational speed of the internal combustion engine 1 and the set rotational speed zero. Supply signal Vd.

The present invention provides, in such a rotational speed control device for an internal combustion engine, a speed setting signal that limits the speed setting signal Vno to a magnitude corresponding to a safe low speed when an abnormal condition occurs in the internal combustion engine 1 or its attached devices. It is characterized in that a limiting circuit 12 is provided.

[Operation of the invention] In the above control device, the control operation for maintaining the rotational speed of the engine at a set rotational speed corresponding to the position of the accelerator operating member is similar to that of conventional control devices.

When an abnormality occurs such as an abnormal rise in engine cooling water temperature or a drop in oil level, the speed setting signal limiting circuit 12 lowers the speed setting signal Vno to a low speed that does not interfere with continued operation of the engine. Limit it to an appropriate size.

Therefore, even if an abnormality occurs, stable operation can be continued at low speed without stopping the engine, and the engine can only be stopped after moving the machine to a safe location or a location where repairs can be made. be able to.

In this case, no matter how you operate the accelerator operating member, the engine is supplied with fuel determined by the limited speed setting signal, and the engine rotational speed is limited to a safe range, ensuring that the engine is protected. can be achieved. Further, since the fuel supply is not stopped no matter how the accelerator operating member is operated, there is no possibility that a large engine brake will suddenly be applied to the internal combustion engine and large rotational fluctuations will occur.

When implementing this invention, the level at which each sensor that detects an abnormal condition performs its detection operation is set on the safe side so that the engine can be operated at low speed even after an abnormality is detected by the sensor. I'll keep it. For example, in a sensor that detects oil level abnormalities,
The sensor is configured to perform a detection operation when the oil level or oil remains at a level that allows the engine to operate at low speed.

Note that if there is an abnormal condition that requires stopping the engine, a circuit may be provided to stop the engine when the abnormal condition occurs. That is, the present invention does not in any way preclude the use of conventional safety circuits.

Furthermore, instead of using the conventional safety circuit, the speed setting signal can be set to zero when an abnormal condition occurs that requires the engine to be stopped immediately.

[Embodiments] Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, in which parts equivalent to those of the apparatus shown in FIG. 4 are given the same reference numerals.

In this embodiment, the speed detection circuit 2 includes a rotation speed detection sensor that is attached to the engine and outputs a detection signal with a frequency proportional to the rotation speed, and a frequency-voltage converter that converts the output frequency of the sensor into voltage. As shown in FIG. 2, this speed detection circuit outputs a speed detection signal Vn that changes in proportion to the rotational speed N (rpm) of the engine.

The actuator 5 is driven by an electric drive means such as a motor or an electromagnetic plunger.
It is connected via a suitable mechanism to regulating means for regulating the amount of fuel supplied to the engine.

Actuator drive circuit 7 is transistor Tr ₁
The drive current to the actuator 6 is adjusted by the transistor _Tr1 , and the drive current to the actuator 6 is adjusted.
By adjusting the position of the engine, the amount of fuel supplied to the engine can be adjusted.

The accelerator position detector 3 includes a potentiometer P whose slider a is interlocked with an accelerator operating member (not shown). One end of the potentiometer P is grounded via a resistor Ri, and a terminal led out from a slider a of the potentiometer P is connected to a positive phase input terminal of an operational amplifier OP. The output terminal and the negative phase input terminal of the operational amplifier OP are connected to each other to constitute a voltage follower circuit, and the operational amplifier constitutes a speed setting signal output circuit 4.

The other end of potentiometer P is connected to the collector of PNP transistor Tr ₂ , and transistor Tr ₂
The emitter is connected via a resistor Ro to a constant voltage power supply that outputs a DC constant voltage Ed. A resistor Rb is connected in parallel between the collector and emitter of the transistor _{Tr 2} , and a series circuit of the output contact of the water temperature sensor 10 and the output contact of the oil level sensor 11 is connected in parallel between the base and emitter of the transistor Tr 2. There is. The contacts of these sensors 10 and 11 close when the engine cooling water temperature and oil level are normal, respectively, and make the transistor Tr ₂ conductive, and when the cooling water temperature rises abnormally or the engine oil level increases, When the contact point of any sensor opens due to an abnormal drop, the transistor Tr ₂ is cut off.

In this embodiment, the transistor Tr ₂ and the resistor Ro,
A speed setting signal limiting circuit 12 is configured by Rb.

Next, to explain the operation of the above embodiment, in FIG. 1, the speed detection circuit 2 detects the rotational speed (rpm) of the internal combustion engine, and generates a speed detection signal Vn corresponding to the rotational speed (see FIG. 2). is given to the arithmetic circuit 8.

On the other hand, the contacts constituting the water temperature sensor 10 are closed when the temperature of the engine cooling water is below the set value.
Opens when the temperature exceeds the set value. Further, the oil level sensor 11 is closed when the oil level is above a set value, and opens when the oil level is lower than the set value.

Note that the temperature at which the water temperature sensor 10 performs the detection operation (in this example, the contacts open) is set to be low in consideration of safety. That is, the temperature at which the contact of the water temperature sensor 10 opens is not set to a temperature so low that it is necessary to immediately stop the operation of the engine when the sensor performs a detection operation, but rather the temperature at which the contact point of the water temperature sensor 10 opens is set to a temperature that is as low as possible so that it is necessary to immediately stop operation of the engine when the sensor 10 performs a detection operation. Set the temperature to a level that allows the engine to operate at low speeds. Similarly, the setting level at which the oil level sensor 11 performs the detection operation (in this example, the contact opens) is set high in consideration of safety.

Under normal conditions, these contacts are both closed and transistor Tr ₂ is conducting. Therefore, a resistor Ro and a transistor are connected from a constant voltage power supply (not shown).
A current flows through Tr ₂ , the potentiometer P, and the resistor Ri, and an accelerator position detection voltage corresponding to the accelerator position is output between the end of the potentiometer P on the resistor Ri side and the slider a. This detected voltage is amplified by the operational amplifier OP and given to the operational circuit 8 as the speed setting signal Vno. The arithmetic circuit 8 supplies a control signal Vd to the actuator drive circuit 7 so as to make the difference between the speed setting signal and the speed detection signal zero. This causes the actuator 6 to operate the fuel adjustment means to match the engine rotational speed to the set rotational speed.

In the above device, when the contacts of sensors 10 and 11 are both closed and transistor Tr ₂ is conductive, the speed setting signal Vno is
The voltage drop between the collector and emitter of Tr ₂ is set to zero,
The output voltage of the constant voltage power supply circuit is Ed, the resistance value of the resistor Ro is ro, and the overall resistance value of the potentiometer P is
rs, the resistance value between the end of the resistor Ri side of the potentiometer P and the slider is ra (0≦ra≦rs), the resistance value of the resistor Ri is ri, and the resistance value of the resistor Rb is rb. amplifier OP
When the gain of is K, it is given by Vno=K・Ed(ri+ra)/(ro+rs+ri)...(1).

On the other hand, when one of the sensors detects an abnormality and transistor Tr2 is cut off, a resistor Rb is inserted between the resistor Ro and the potentiometer P, so the speed setting signal Vno becomes Vno=K・Ed(ri+ra)/(ro+rb+rs+ri)...(2) The magnitude of the speed setting signal Vno is determined by the resistance Rb
The resistance value rb reduces the current flowing through the potentiometer P by the amount limited. In this embodiment, the maximum value of the speed setting signal Vno (the value when ra = rs) when the transistor Tr2 is cut off can be used to allow the engine to operate in a state where an abnormality is detected by the sensor 10 or 11. The resistance value of the resistor Rb is set so as to limit the speed to a sufficiently low speed.

Therefore, when the sensor 10 or 11 detects an abnormality, the rotational speed of the engine is limited to a speed that is low enough to allow continued operation under the abnormal condition. In this state, even if the accelerator operating member is operated to increase the speed until the slider of the potentiometer P is displaced to the position ra = rs, the rotational speed of the engine will not exceed the set limit speed. Since it does not rise, operation can be continued without damaging the engine. Further, the driver can know that some kind of abnormality has occurred since the rotational speed of the engine does not increase even if the accelerator operating member is operated to the speed increasing side.

In the embodiment described above, a circuit can be added that displays the details of the abnormality by operating display means such as light emitting diodes provided corresponding to each sensor when the sensor performs a detection operation. In addition, two sensors are installed to detect abnormal conditions (in the above example, an abnormal increase in water temperature and an abnormal decrease in oil level).
By providing two different types, it is possible to detect abnormal conditions that allow engine operation at low speeds and abnormal conditions that require immediate stopping of engine operation, and allow engine operation at low speeds. When an abnormal condition is detected, the speed setting signal limiting circuit 12 as in the above embodiment is operated, and when an abnormal condition that requires stopping the engine is detected, the speed setting command signal Vno is set to zero. Alternatively, similarly to the device shown in FIG. 4, the actuator drive circuit 7 may be controlled to stop the supply of electricity to the actuator 5, thereby stopping the fuel supply and stopping the engine.
In the above embodiment, in order to set the speed setting signal Vno to zero, for example, the positive phase input terminal of the operational amplifier OP is provided with a switch means that closes when an abnormal condition that requires stopping the engine is detected. All you have to do is short-circuit the terminal and ground.
Furthermore, in order to stop the electric charge being applied to the actuator 5, a switch means that closes when an abnormal state is detected is provided, and the switch means short-circuits between the base and emitter of the transistor Tr ₁ of the actuator drive circuit 7, so that the transistor Tr ₁ All you have to do is keep it shut off.

In the above example, the speed limiting circuit is activated when an abnormal state of the engine is detected, but the speed setting signal limiting circuit may also be activated when an abnormality occurs in an attached device of the engine. . FIG. 3 shows an embodiment in which the rotational speed of the engine is reduced when the connector connecting the rotational speed control device and the accelerator position detector 3 is disconnected. Position detector 3
This is a connector for connecting the speed setting signal output circuit 4 to the speed setting signal output circuit 4. In this example, resistors R ₀ , R ₁ and R ₂ are connected between the positive output terminal of a constant voltage power supply (not shown) and the ground.
are connected in series with resistor R ₂ facing the ground side, and the voltage across resistor R ₂ is input to the positive phase input terminal of operational amplifier OP. One end of the potentiometer P constituting the accelerator position detector 3 is connected to the connection point of the resistors _R0 and _R1 via the contact 20a of the connector 20, and the slider a of the potentiometer P
is connected to the connection point of the resistors R ₁ and R ₂ via the contact 20b of the connector 20. Further, the other end of the potentiometer P is connected to one end of a resistor Ri via a contact 20c of the connector 20, and the other end of the resistor Ri is grounded. In this example, the resistances R ₀ ,
A speed setting signal limiting circuit 12 is configured by R ₁ and R ₂ . The other configurations are similar to the embodiment shown in FIG.

In the embodiment shown in FIG. 3, the resistance values of resistors R ₀ , R ₁ , R ₂ and Ri are r ₀ r ₁ , r ₂ and ri, respectively, and r ₁
and r ₂ are sufficiently larger than the total resistance value rs of the potentiometer, the speed setting signal Vno when the connector 20 is normally connected is given by the above equation (1). Also, due to vibration etc., the connector 2
The speed setting signal Vno when the value deviates from 0 is given by: Vn ₀ =K·Ed·r ₂ /(r ₀ +r ₁ +r ₂ ) (3). Here, if r ₁ , r ₂ >> r ₀ , Vn ₀ = K・Ed・r ₂ / (r ₁ + r ₂ ) …(4) Therefore, Vn ₀ in equation (4) is a sufficiently safe low speed. By setting r ₁ and r ₂ to have a size corresponding to , it is possible to limit the speed to a low speed when the connector is disconnected.

In the embodiment shown in Figure 2, when detecting an abnormality in water temperature or oil level and limiting the speed, the resistance
A parallel circuit consisting of the collector-emitter circuit of transistor Tr ₂ shown in Figure ₁ and resistor Rb is inserted between R ₀ and resistor R 1 to shut off the transistor when the sensor performs a detection operation. Just do it like this.

[Effects of the invention] As described above, according to the invention, even if an abnormality occurs, it is possible to continue operation at low speed without stopping the engine, so the machine can be moved to a safe place or repaired. The advantage is that the engine can be stopped after being moved to a possible location.

Furthermore, according to the present invention, when an abnormality occurs, the engine can continue to operate stably within a safe speed range no matter how the accelerator operating member is operated, thereby ensuring the protection of the engine. can be achieved.

Furthermore, with the speed setting signal limited to a size corresponding to a safe low speed, the fuel supply to the engine will not be stopped no matter how you operate the accelerator operating member, so if the engine suddenly becomes larger It is possible to prevent a dangerous situation such as when the brake is hard and a large rotational fluctuation occurs.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a diagram showing the characteristics of the speed detection circuit used in the same embodiment, and Fig. 3 shows the main parts of another embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of a conventional device. 1...Internal combustion engine, 2...Speed detection circuit, 3...
Accelerator-detector, 5... Actuator, 6...
...Battery, 7...Actuator drive circuit, 8
... Arithmetic circuit, 10 ... Water temperature sensor, 11 ... Oil level sensor, 12 ... Speed setting signal limiting circuit, P ... Potentiometer, Ro, Rb, Ri ...
Resistor, Tr ₂ ...transistor.

Claims (1)

[Scope of utility model registration request] an electric actuator that operates means for adjusting the amount of fuel supplied to the internal combustion engine; an actuator drive circuit that adjusts the drive current of the actuator according to a control signal; and a speed detection device that detects the rotational speed of the internal combustion engine. a speed detection circuit that outputs a signal, an accelerator position detector that detects the position of an accelerator operating member that sets the speed of the internal combustion engine, and a speed setting signal that receives the output of the accelerator position detector as input and outputs a speed setting signal. an output circuit; and an arithmetic circuit that receives the speed setting signal and the speed detection signal as input and supplies a control signal to the actuator drive circuit so as to make the deviation between the actual rotational speed of the internal combustion engine and the set rotational speed zero. A rotational speed control device for an internal combustion engine, comprising a speed setting signal limiting circuit that limits the speed setting signal to a magnitude corresponding to a safe low speed when an abnormal condition occurs in the internal combustion engine or its auxiliary equipment. A rotation speed control device for an internal combustion engine, characterized by: