JPS6233432B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a starting device for a diesel engine, and particularly to a starting device for a diesel engine equipped with a preheating plug.

(Prior Art) In a conventional diesel engine, particularly a diesel engine with a sub-combustion chamber, when starting the engine, a preheating plug is used to preheat the inside of the sub-combustion chamber in order to improve startability.

This preheating plug method only requires heating current to flow from the power supply to the preheating plug via the starter switch.
It has the advantage that the device is simple and the starting operation is easy, but on the other hand, it has the disadvantage that it takes 20 to 30 seconds to preheat the preheating plug, and the preheating startability is extremely poor.

In order to eliminate these drawbacks and shorten the preheating time, as seen in Japanese Utility Model Publication No. 50-2924, the resistance value of the heating element of the preheating plug is reduced to increase the heating current and shorten the preheating time. In addition, there has been an attempt to prevent the heating wire from being oxidized and disconnected by dividing the shaft of the preheating plug into two parts and connecting the two parts with a thermostat. However, when using a thermostat, it is difficult to accurately control the temperature of the heat generating portion, and the contact portion of the thermostat may be welded or contact failure may occur, resulting in a lack of durability.

In addition, a series circuit consisting of a heating element with a low resistance value that will melt immediately if a predetermined rated voltage is continuously applied, and a resistance element whose resistance value is extremely small compared to this resistance value is relayed. A series circuit of a heating element and a resistive element and another two connected in parallel to this are connected to the power supply via contacts.
After the power is turned on, the heating element is rapidly heated to a set temperature, and after the Wheatstone bridge is balanced at the set temperature, the relay contact is disconnected. A heating device has also been developed that repeats this process to maintain the temperature of the heating element at a set temperature.

(Problem to be solved by the invention) Although such a heating device is capable of rapid heating, it is not possible to quickly connect and disconnect relay contacts that have a mechanical structure, so the temperature of the heating element does not reach the set temperature. The drawback was that it rippled around the area, making it difficult to maintain a stable temperature.

Therefore, in order to further avoid such drawbacks,
It has been considered to use a semiconductor switching element instead of a relay contact, but the resistance of the semiconductor switching element itself is much higher than the contact resistance of the relay contact, making it difficult to apply the terminal voltage of the heating element when the power is turned on. It cannot be approached with voltage and therefore cannot be heated rapidly.

An object of the present invention is to provide a diesel engine which can shorten the preheating time as much as possible without complicating the structure of the preheating device of the diesel engine, and which can smooth the temperature change around the set temperature of the preheating plug. The purpose is to provide a starting device for

(Means for Solving the Problems) The present invention provides a preheating plug whose resistance value of a heating element increases as the heating temperature rises, and a preheating plug connected via a detection resistor to control the current to the preheating plug. a parallel circuit of a contact type relay and a transistor, a Wheatstone bridge in which the detection resistor and the heating element of the preheating plug are the two sides of the bridge circuit, and a potential difference between the midpoint of the Wheatstone bridge reaches a set value. a comparator that outputs an output signal when the power is turned on; a first output terminal that outputs an output signal when the power is turned on and stops the output signal upon receiving the output signal of the comparator; and a first output terminal that receives the output signal of the comparator and outputs the output signal. or a preheating plug whose resistance value of the heating element increases as the heating temperature increases, and a detection resistor to control the current to the preheating plug. A Wheatstone bridge in which two sides of the bridge circuit are a parallel circuit of a contact relay and a transistor connected, a starter switch connected in series to a power supply, the detection resistor and a heating element of a preheating plug. , a comparator that generates an output signal when the potential difference at the midpoint of the Wheatstone bridge reaches a set value; and a comparator that generates an output signal at the same time as the starter switch is turned on, and receives the output signal of the comparator and generates the output signal. a control device having a first output terminal to be stopped, and second and third output terminals that receive an output signal of the comparator and output an output signal;
The present invention provides a diesel engine starting device including a starter starting device.

(Function) According to the present invention, the contact type relay of the current control device is controlled on/off by the output signal of the first output terminal of the control device, and the heating current is applied until the preheating plug reaches the set temperature. The transistor is turned on and off using the output signal from the second output terminal to control the current to the preheating plug that has reached the set temperature, and the starter starting device is controlled by the output signal from the third output terminal. be able to.

(Example) Next, an example of the present invention will be described in detail with reference to the drawings.

In the circuit shown in FIG. 1, 1 is a power supply;
Consists of vehicle batteries, etc. 2 is a starter switch, and 3 is a preheating plug, which are usually provided in correspondence with the number of cylinders in the engine, but only one is shown in the figure for the sake of simplicity. 31 is the heating element, and the resistance value R of this heating element 31 has a positive temperature coefficient that increases as the heating temperature increases.

4, 5, and 6 are resistors, and their respective resistance values are r1,
r2 and r3, and r1 in particular is extremely small compared to R, and is usually one-tenth or less of R. The heating element 31 and the resistors 4, 5, and 6 constitute a Wheatstone bridge circuit 7 as shown. A comparator 8 is connected to the intermediate points m ₁ and m ₂ of the bridge circuit 7. The comparator 8 is configured to generate an output signal when the heating temperature of the preheating plug reaches a temperature T ₁ (see Figure 2, G) near the set temperature, the resistance value R increases, and the following formula (1) is established. is set.

r2/r1=r3/R...(1) 9 is the resistor 4 of the Wheatstone bridge circuit 7
is the contact of relay CR ₁ connected to. A transistor 11 is connected to the resistor 4 in parallel with the relay contact 9, and its base side 11a is connected to the second output terminal 13 of the control device 12. 16 is a starter, which is started by closing contact 14 of starter relay _CR2 .

10 is the operating coil of relay CR ₁ , and control device 1
2. 15 is the operating coil of starter relay CR ₂ , which is connected to control device 1.
It is connected to the third output terminal 17 of 2. 18 is an output terminal of the control device 12, which is the output terminal of the starter switch 2.
It is connected to the power source via the starter switch 2 so that the power source voltage is input at the same time as the circuit is closed. 1
9 is an output terminal of the control device 12, to which the output terminal of the comparator 8 is connected. 22 is the transistor 11
is the bias resistance.

The control device 12 causes current to flow through the actuation coil 10 of the relay CR ₁ at the same time as the starter switch 2 is closed, and after a slight time delay as will be described later, the control device 12 causes the relay CR ₁ to close.
It has the function of operating the contact 9 of the comparator 8.
In response to the output signal, relay CR ₁ is deactivated, and activation coil 1 of starter relay CR ₂ is activated.
0 for a certain period of time, starter relay CR ₂
The contact 14 is operated for a certain period of time, and the transistor 11 is turned on and off at certain intervals. Therefore, the control device 12 is constituted by a transmission signal conversion amplifier consisting of a well-known one-shot multi-circuit, a flip-flop circuit, etc. which is also well-known. Further, the control device 12 includes a well-known RC delay circuit, a well-known Schmitt trigger circuit, and a well-known one-shot multi-circuit in order to turn on and off the transistor 11 in response to the output signal of the comparator 8. It has a switching regulator consisting of.

Note that the configuration of the control device 12 may be any configuration that can be appropriately constructed by those skilled in the art as long as it achieves the above-described effects. Heating element 31 of preheating plug 3
It is preferable that the resistance value is 2/3 or less of the resistance value at the set temperature of a preheating plug used in a normal diesel engine of the same type, which is heated to saturation by continuing to apply a voltage until the set temperature is reached.

The configuration of the diesel engine starting device according to the present invention has been described above. Next, the operation of the device will be explained with reference to FIG. 2.

First, when the starter switch 2 is closed to start the engine, a power supply voltage is applied to the input terminal 18 of the control device 12, and the output terminal 20 of the control device 12 excites the operating coil 10 of the relay CR ₁ as described above. An output signal is generated, the actuating coil 10 is excited, and the contact 9 of the relay _CR1 is actuated with a short delay of time _t1 (see C and B in FIG. 2). In addition, the operating coil 10 of relay coil CR ₁
At the same time as the transistor 11 is driven, the transistor 11 is turned on and a current flows, but because of its own resistance value, a large instantaneous current does not flow, and since the time _t1 is very short, there is no possibility that the transistor 11 will be destroyed. Never.

Activation of relay CR ₁ A closes its contacts 9,
A heating current flows through the preheating plug 3 mainly through the circuit: power supply 1 → starter switch 2 → contact 9 of relay CR ₁ → resistor 4 → heating element 31 of preheating plug 3 → power supply 1, and the heating element 31 rapidly heats up. heated. Due to this rapid heating, the temperature of the heating element 31 rises, and when it reaches the temperature T ₁ (see G in Figure 2) near the set temperature, the resistance R of the heating element 31 satisfies the above equation (1). Therefore, the comparator 8 operates and issues an output signal (second
(See figure d).

When the output signal from the comparator 8 is input to the input terminal 19 of the control device 12, the output signal at the output terminal 20 disappears as described above, the operation of the relay CR ₁ is released, and the output terminal 13 is turned off. Since the low level is still maintained, current continues to flow to the base 11a of the transistor 11, and the transistor 1
1 remains on (see E in Figure 2). When the relay CR ₁ is released, the relay contact 9 is opened with a delay of a minute time t ₂ (see B and C in FIG. 2). At the same time, control device 12 emits an output signal from its output terminal 17 for a certain period of time t ₄ , which excites actuating coil 15 of starter relay CR ₂ and activates starter relay CR ₂ . Activation of the starter relay CR ₂ closes its contacts 14 and activates the starter relay 16 (see F in FIG. 2).

Due to the opening of the contact 9 of the relay CR ₁ , the current flowing to the preheating plug 3 takes place only via the transistor 11 . Therefore, the current flowing through the preheating plug is limited by the voltage drop that occurs between the emitter 11b and the collector 11c of the transistor 11, and the heating rate of the heating element 31 is slowed down, preventing accidents such as melting due to overheating of the heating element. It has a preventive effect (see → in Figure 2).

The setting time of the delay circuit in the control device 12 after the output signal of the comparator 8 is input to the control device 12
When time t ₃ has elapsed, a short constant width positive pulse signal is generated from the output terminal 13, so that no base current flows to the base 11a of the transistor 11, and the transistor 11 is turned off. After a short fixed period of time, the pulse signal is turned off and the transistor 11 is turned on. After a short fixed period of time, a positive pulse signal is generated and the transistor 11 is turned off. From then on, the transistor 11 is controlled by the control device 12. With the pulse signal of
(See Figure E). Therefore, the temperature of the heating element 31 changes minutely in the order of →→→, as shown in FIG. 2, and is maintained at almost the same temperature as the set temperature.
Then, the engine starts, the operator turns off the start switch 2, and the series of starting operations ends.

(Effects of the Invention) As described above in detail, the diesel engine starting device according to the present invention includes a preheating plug whose resistance value of the heating element increases as the heating temperature increases;
A parallel circuit of a contact type relay and a transistor connected via a detection resistor to control the current to the preheating plug, and a Wheatstone bridge in which the detection resistor and the heating element of the preheating plug are the two sides of the bridge circuit. a comparator that generates an output signal when the potential difference between the midpoint of the Wheatstone bridge and the Wheatstone bridge reaches a set value; and a comparator that generates an output signal at the same time as power is turned on and stops the output signal upon receiving the output signal of the comparator. a control device having a first output terminal and a second output terminal that receives the output signal of the comparator and outputs an output signal; the contact type relay is turned on by the output signal of the first output terminal of the control device;・Control off and supply heating current until the preheating plug reaches the set temperature, and control the transistor on/off using the output signal of the second output terminal to control the current to the preheating plug that reaches the set temperature. Since this is done by switching from a contact type relay to a transistor, the heating element will melt even if a low resistance heating element is used for the preheating plug, which would melt immediately if the rated voltage was applied continuously for a long time. Therefore, without impairing startability,
The durability of the preheating plug can be ensured.

Furthermore, unlike contact relays, transistors can turn the current on and off quickly, so once the heating element reaches close to the set temperature, it heats up very stably with little ripple due to temperature changes. While ensuring startability and durability, it is also possible to stably maintain the preheating plug at the set temperature.

Moreover, according to the diesel engine starting device of the present invention, the current for heating the heating element to the set temperature is supplied only through the contact type relay with low contact resistance and the detection resistor with low resistance value. A large amount of power can be supplied to the preheating plug immediately after voltage is applied, and the heating element of the preheating plug can be raised to near the preheating set temperature at a speed that is incomparable to conventional methods. After the heating element rises to near the preheating set temperature and the contact type relay is opened, the transistor, which has a considerable resistance to itself,
Since the circuit that heats the heating element is controlled on and off, this transistor limits the current to some extent, preventing excessive current from flowing through the heating element, thereby protecting it.

In other words, by using a contact type relay and a heating element with low resistance at the set temperature, we have solved the drawback that conventional semiconductor switching elements were unable to heat up quickly, and we are now able to control the temperature stably at the set temperature. I'm trying to do what I can. Furthermore, since the starter can be started simply by closing the starter switch, there is no need for a preheating device that is separate from the starting device as in conventional starting aid devices, making it possible to create a starting device with an extremely simple structure and easy operation. It has many excellent effects such as:

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a diesel engine starting device according to the present invention, and FIG. 2 is a time chart for explaining the operation of the device. 1... Power supply, 2... Starter switch, 3... Preheating plug, 31... Heating element, 4, 5, 6... Resistor, 7... Wheatstone bridge circuit, 8... Comparator, 9... Relay contact, 10... Relay operating coil, DESCRIPTION OF SYMBOLS 1...Transistor, 12...Control circuit, 14...Starter relay contact, 15...Starter relay coil, 16...Starter.

Claims (1)

[Claims] 1. A preheating plug whose resistance value of the heating element increases as the heating temperature rises, and a contact type relay and transistor connected via a detection resistor to control the current to the preheating plug. A Wheatstone bridge in which the detection resistor and the heating element of the preheating plug are the two sides of the bridge circuit, and a comparison in which an output signal is generated when the potential difference at the midpoint of the Wheatstone bridge reaches a set value. a first output terminal that outputs an output signal at the same time the power is turned on, receives an output signal from the comparator, and stops the output signal; and a second output terminal that receives an output signal from the comparator and outputs an output signal. a control device having a first output terminal, the contact type relay is controlled on/off by the output signal of the first output terminal of the control device, a heating current is supplied until the preheating plug reaches a set temperature, and a second output terminal is provided. A diesel engine starting device characterized by controlling a transistor on and off using an output signal from a terminal to control current to a preheating plug that reaches a set temperature. 2. A preheating plug whose resistance value of the heating element increases as the heating temperature increases, and a parallel circuit of a contact type relay and a transistor connected via a detection resistor to control the current to the preheating plug; A starter switch connected in series with the power supply, a Wheatstone bridge whose two sides are the detection resistor and the heating element of the preheating plug, and a potential difference between the intermediate point of the Wheatstone bridge reaches a set value. a comparator that emits an output signal when the starter switch is turned on; a first output terminal that emits an output signal at the same time as the starter switch is turned on; and a first output terminal that receives the output signal of the comparator and stops the output signal; A control device having second and third output terminals for receiving and outputting an output signal, and a starter starting device, the control device controlling on/off of a contact type relay with the output signal from the first output terminal of the control device. Then, a heating current is supplied until the preheating plug reaches the set temperature, and the output signal from the second output terminal controls the transistor on and off to control the current to the preheating plug that has reached the set temperature. A starting device for a diesel engine, characterized in that a starter starting device is controlled by an output signal from an output terminal of the diesel engine.