JPS6234945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to a control device for controlling the temperature of a glow plug in a diesel engine.

First, a conventional device of this type is shown in FIG.

In the figure, 1 is a key switch, and 2 is a controller, which is composed of an input section 21, a control section 22, an output section 23, and a comparator 24. 3 is a first glow relay controlled by the output of the output section 23, 4 is a second glow relay, 5 is a dropping resistor connected in series to the second glow relay, and 6 is also connected to the register. A sensing resistor 7 is connected in series, a glow plug 7 is provided in each cylinder of the engine and has a positive resistance-temperature characteristic, and 8 is a battery.

FIG. 2 is a timing chart for explaining the operation of the apparatus shown in FIG.

Next, the operation will be explained. key switch 1
At the ON position, the first glow relay 3 is turned ON via the controller 2. As a result, the current from the battery 8 passes through the first glow relay 3 and the sensing resistor 6, and heats the glow plug 7. Next, turn key switch 1 to ST position and start the engine. At this position, the second glow relay 4 is also turned on, and the temperature of the glow plug 7 continues to rise gradually. Furthermore, in this state, when the glow plug 7 rises to the target temperature and the voltage drop of the sensing resistor 6 reaches a predetermined value, the first glow relay 3 is automatically turned off by the controller 2, and the glow is turned off. To energize plug 7,
Due to the second glow relay 4, only the current flows through the resistor 5. Once the engine has finished starting, return key switch 1 to the ON position.
At the same time, the second glow relay 4 is turned off.

By the way, since the conventional glow plug control device is configured as described above, a dedicated sensing resistor 6 is required to detect the resistance value due to temperature change of the glow plug 7, and the communication to the glow plug 8 is required. Since the electric path is divided into two types and two stages: a current-carrying path via the dropping resistor 5 and a current-carrying path not via the register 5, there are many structural parts and the control is complicated. In addition, the voltage drop due to the two resistors 5 and 6 above is:
This causes power loss and is inefficient.Furthermore, even if the current value is reduced by the dropping resistor 5 when the glow plug 7 reaches the specified temperature, the temperature reduction characteristics of the glow plug are extremely dependent on the atmospheric conditions. There were drawbacks such as being unstable and the subsequent temperature becoming completely unstable, which affected engine starting performance.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it is possible to adjust the resistance value corresponding to the temperature change of the glow plug by passing a detection current through the glow plug when the glow plug is de-energized. By detecting the resistance value and controlling the energization time to the glow plug in response to the detected resistance value, the temperature of the glow plug can be easily detected without the need for a special sensing resistor like the conventional device described above. An object of the present invention is to provide a device that can accurately control the temperature of a glow plug with a simple configuration.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

In FIG. 3, an electromagnetic glow relay 3 is provided in series with the current supply path from the battery 8 to the glow plug 7. The controller 2 that controls the glow relay 3 is constructed as follows. That is, 2a is a constant current circuit that supplies a constant current for detection to the glow plug 7, and is a transistor.
Tr ₁ , Tr ₂ , resistance R ₁ , R ₂ , R ₃ constant voltage diode Z ₁
It is composed of a diode _D1 . Reference numeral 2b denotes a constant voltage circuit that supplies a constant voltage VCC to each circuit, and is composed of transistors Tr ₃ , Tr ₄ , Tr ₅ , resistors R ₄ , R ₅ , R ₆ and a constant voltage diode Z ₂ . 2c is an inverting amplifier circuit that inverts and amplifies the voltage drop of the glow plug 7, which includes an operational amplifier OP ₂ , resistors R ₁₇ , R ₁₈ ,
It consists of _R19 , _R20 , _R21 , _R22 diode _D4 . 2d is a temperature level detection circuit that detects the voltage level of the inverting amplifier circuit 2c and generates a fixed-time trigger pulse when the glow plug temperature drops to the lower limit target value, and is an operational amplifier that constitutes a comparison circuit.
OP ₃ resistors R ₂₃ , R ₂₄ , R ₂₅ , R ₂₆ and NOR gate G ₃ , which constitutes a monostable circuit, inverter G ₂ resistor R ₂₇ ,
It consists of R ₂₈ capacitor C ₂ . 2e
is a sensing pulse generation circuit that generates a sensing pulse with a predetermined sensing time width in synchronization with the trigger signal of the temperature level detection circuit 2d and the turning on of the key switch 1, which includes a transistor Tr ₁₀ and resistors R ₂₉ , R ₃₀ , R ₃₁ , R ₃₂ capacitor C ₃ inverter
Consists of G ₄ diodes D ₅ . 2f
is a switch circuit that is opened and closed by the above sensing pulse, and includes transistors Tr ₆ , Tr ₇ , resistor R ₇ ,
It is composed of R ₈ and R ₉ . 2g is a timer circuit that generates an output with a pulse width corresponding to the output voltage of the inverting amplifier circuit 2c applied via the switch circuit 2f in synchronization with the end of the sensing pulse; A capacitor C ₁ that is charged to a voltage, a resistor R ₁₀ that discharges its charge at a predetermined time constant, and an operational amplifier that constitutes a comparator that responds to the charging voltage level.
It is composed of OP ₁ resistors R ₁₂ , R ₁₃ , R ₁₄ and a NOR gate G ₁ . 2h is a drive circuit that drives the glow relay 3 by the output of the timer circuit 2g, and includes transistors Tr ₈ and Tr _{9 and} resistors.
It is composed of R ₁₅ , R ₁₆ electromagnetic relay RL ₁ diodes D ₂ and D ₃ .

Next, the operation of the apparatus thus constructed in FIG. 3 will be explained based on the timing chart in FIG. 4.

First, key switch 1 is turned on as shown in Figure 4A.
When the capacitor C3 of the sensing pulse generating circuit 2e is turned on, the capacitor _C3 of the sensing pulse generating circuit 2e is charged at a predetermined time constant via the resistor _R31 , but until this charging voltage reaches a predetermined level, the output of the inverter _G4 is As shown in FIG. B, it is at H level, and the transistors Tr ₈ and Tr ₉ are turned off via the NOR gate G ₁ to keep the glow relay 3 in the OFF state. On the other hand, the time constant current circuit 2a supplies a predetermined constant current to the glow plug 7, and generates a voltage drop based on the resistance value corresponding to the temperature of the glow plug 7 at this time. The inverting amplifier circuit 2c inverts and amplifies this voltage drop and rapidly charges the capacitor _C1 of the timer circuit 2g to the value of the inverted amplified output voltage at this time via the switch circuit 2f which is turned on by the sensing pulse. (See Figure 4c). This charging voltage is compared with the comparison voltage set by the voltage dividing resistors R ₁₂ and R ₁₃ in the operational amplifier OP ₁ constituting the comparator, and when the charging voltage is larger, an L level output as shown in FIG. 4D is generated. . When the sensing pulse ends, all inputs of the NOR gate _G1 go to L level, so the output goes to H level (see Fig. 4E). Glow relay 3 is turned on via drive circuit 2h (see (See Figure 4F; glow relay 3 has an inherent relay delay).

When the glow relay 3 is turned on, current is directly supplied to the glow plug 7 from the battery 8, the glow plug 7 generates heat, and its temperature gradually rises as shown in FIG. 4H. At this time, the voltage drop across the glow plug 7 reaches the maximum voltage (battery voltage) as shown in FIG.
It stops as shown in Figure G, and the output of the inverting amplifier circuit 2c shows the minimum value. On the other hand, when the switch circuit 2f is turned off due to the end of the sensing pulse, the charge in the capacitor _C1 is discharged with a time constant determined by the resistor _R10 , and the charging voltage becomes
When the voltage drops to the comparison voltage set by R ₁₂ and R ₁₃ ,
The output of operational amplifier _OP1 is inverted to H level and sent to glow relay 3 via NOR gate _G1 and drive circuit 2h.
Turn off the power supply to the glow plug 7. Therefore, during the first energization period of the glow plug 7 after the key switch 1 is turned on, the capacitor _C1 is connected to the glow plug 7 while the sensing pulse is being generated.
By being charged to a value that is inversely proportional to the temperature (resistance value) of the glow plug 7, a period that is inversely proportional to the temperature of the glow plug 7 is exhibited. can be heated.

As the power supply to the glow plug 7 is cut off, the glow plug temperature decreases as shown in Fig. 4H, and the input of the inverting amplifier circuit 2c exhibits a change corresponding to the temperature (Fig. 4 I), and its output becomes an inverting amplifier. and then rises as the temperature decreases. When the output of the inverting amplifier circuit 2c reaches the set comparison voltage corresponding to the lower limit target temperature, the output of the operational amplifier _OP3 constituting the comparator is inverted to the L level as shown in FIG. 4K, and synchronized with this inversion. The temperature detection circuit 2d then generates an H level trigger signal as shown in FIG. 4L. In response to this trigger signal, the transistor Tr ₁₀ of the sensing pulse generation circuit 2e is momentarily turned on to discharge the charge in the capacitor C ₃ and then charge the capacitor via the resistor R ₃₁ to generate a sensing pulse again. During the generation period of this sensing pulse, the temperature of the glow plug 7 is stored as a voltage in the capacitor _C1 of the timer circuit 2g as described above, and when the sensing pulse ends, the glow relay 3 is turned on again for a period corresponding to the amount of charge in the capacitor _C1 . The glow plug 7 is energized. Thereafter, similar operations are repeated to control the temperature of the glow plug 7 to around a temperature slightly higher than the lower limit target temperature, thereby heating the inside of the engine cylinder.

Here, after the glow plug temperature reaches the target temperature, turn the key switch 1 to the St position, supply power to the starter (not shown), and drive the engine. This will enable a reliable engine start, and the engine start will be completed. Then, key switch 1 returns to OFF and the control ends.

In the above explanation, we have explained the case where the glow plug temperature lower limit target is exceeded by the first energization to the glow plug 7, but if this does not occur due to a drop in battery voltage etc., the glow plug 7 is energized. A sensing pulse is generated at the same time as the current is cut off, and the capacitor _C1 is charged in response to the low temperature at that time, and the glow plug 7 is immediately energized and heated until it exceeds the lower limit target temperature.

Further, the glow relay 3 is not limited to an electromagnetic type, but may be a semiconductor relay.

Furthermore, the ON periods of the glow relays mentioned above are all controlled in accordance with the detected temperature of the glow plug 7, but the ON periods from the second time onwards are determined by the target temperature and are almost the same period, so the first of
It is also possible to determine only the ON period in accordance with the detected temperature of the glow plug, and to set it as a predetermined period from the second time onwards.

As described above, this invention provides a glow relay for a glow plug power supply circuit whose resistance value changes depending on the temperature.
For devices that control the temperature of the glow plug through ON-OFF control, when the glow relay is OFF, a detection current is supplied to the glow plug to detect the temperature of the glow plug, and the glow relay is activated in response to this detected temperature. Since the temperature of the glow plug is controlled by determining the ON period, there is no need to insert a special sensing resistor into the power supply circuit of the glow plug, and the configuration can be simplified and power loss can be reduced. In addition, since the ON timing of the glow relay is determined by detecting that the detected temperature mentioned above has fallen to the set temperature, the glow relay is
During the OFF period, the glow plug's temperature drop characteristics with respect to time are extremely unstable depending on the atmospheric condition, but the glow plug's energization is controlled accurately to the lower limit target temperature, and the temperature is maintained with high precision. It has the effect of giving you control. Moreover, since the above detection current for detecting the glow plug temperature during the OFF period of the glow relay is a constant current from the constant current circuit, the glow plug temperature can be accurately detected regardless of power supply voltage fluctuations, and from this point of view, it is highly accurate. This allows for precise temperature control.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing a conventional device, FIG. 2 is a timing chart for explaining the operation of the device shown in FIG. 1, FIG. 3 is an electric circuit diagram showing an embodiment of the device of the present invention, and FIG. 4 3 is a timing chart for explaining the operation of the apparatus. In the figure, 1 is a key switch, 2 is a controller,
3 is a glow relay, 7 is a glow plug, 8 is a battery, 2a is a constant current circuit, 2b is a constant voltage circuit, 2
c is an inverting amplifier circuit, 2d is a temperature level detection circuit,
2e is a sensing pulse generation circuit, 2f is a switch circuit, 2g is a timer circuit, and 2h is a drive circuit. Note that the same reference numerals in the drawings indicate the same or equivalent parts.

Claims (1)

[Claims] 1. The control means includes a glow plug installed in the engine and exhibiting a predetermined resistance-temperature characteristic, a glow relay connected in series to the power supply circuit of the glow plug, and a control means for controlling ON/OFF the glow relay. Temperature detection means for supplying a constant detection current from a constant current circuit to the glow plug during the OFF period of the glow relay to detect a temperature based on the resistance value of the glow plug; and a temperature detected by the temperature detection means. a timer means for determining an ON period of the glow relay in response to the ON period and energizing the glow plug during the ON period; and a timer means for detecting the temperature by the temperature detection means during the OFF period after the ON period of the glow relay. A glow plug control device comprising temperature level detection means for detecting that the temperature has decreased to a set temperature and determining when to turn on the glow relay.