JPH0656146B2 - Diesel engine glow plug controller - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a glow plug control device for controlling the temperature of a glow plug in a diesel engine.

[Conventional technology]

A conventional device of this type is, for example, JP-A-55-1253.
As disclosed in Japanese Patent Laid-Open No. 62-62, a timer in which the generation time of an output signal changes according to the power supply voltage of a glow plug, and a relay connected in series with a power supply circuit of the glow plug to directly apply the power supply voltage to the glow plug , There was a configuration in which the relay was operated by a timer.

In such a glow plug control device, the temperature rising characteristic of the glow plug is approximated by the CR charging circuit, and the temperature equivalent voltage of this charging circuit and the constant voltage set corresponding to the control target temperature are compared by the comparator. By setting the timer to turn off when the voltage is above the set voltage, and charging the CR with the power supply voltage of the glow plug, the timer time is set in inverse proportion to the power supply voltage, and the excess and deficiency of temperature due to the high and low power supply voltage is prevented. The temperature of the glow plug is raised to the predetermined temperature required to start the diesel engine.

[Problems to be solved by the invention]

Since the conventional glow plug control device for a diesel engine is configured as described above, the approximation of the temperature rise characteristic of the glow plug is determined by the CR time constant, and it is difficult to make a complete approximation. Therefore, the temperature control error is large. , It is impossible to control a glow plug having a temperature raising characteristic other than the time constant,
In addition, since the plug temperature before energization is not reflected, there are large variations due to the initial temperature, and further, there is a problem in that the harness resistance and the contact resistance of the switching element change due to changes over time, which causes an error in the temperature control of the glow plug. It was

The present invention has been made to solve the above-mentioned problems, and the glow plug can be used regardless of the initial temperature of the glow plug, the value of the applied voltage, the harness resistance, the contact resistance of the switching element, and the like. The purpose of the present invention is to obtain a glow plug control device for a diesel engine that can accurately control the target temperature.

[Means for solving problems]

A glow plug control device for a diesel engine according to the present invention detects a voltage drop based on temperature with a constant current supply means for supplying a constant current for temperature detection to a glow plug during an open period of an opening / closing element and a constant current supplied. Then, drive time calculation means for calculating the energization time corresponding to the temperature rise of the glow plug corresponding to the detected temperature, and energization of the glow plug corresponding to the glow plug terminal voltage after energization detected by the voltage detection means It is provided with a voltage correction amount calculation means for calculating the correction amount of time, and an opening / closing element drive signal calculation means for determining the driving time of the switching element based on the outputs of the driving time calculation means and the voltage correction amount calculation means. .

[Work]

In the glow plug control device for a diesel engine according to the present invention, the driving time calculating means detects the temperature as a voltage drop of a constant current before energizing the glow plug, and raises the glow plug to a predetermined temperature according to the temperature. The energizing time for the operation is determined. Further, the voltage correction amount calculation means detects the terminal voltage during the energization of the glow plug, determines the correction amount of the energization time based on this voltage, and sequentially performs the voltage correction during the energization period. Is accurately controlled.

〔Example〕

FIG. 1 is an overall configuration diagram of a glow plug control device for a diesel engine according to the present invention. In the figure, 1 is a glow plug equipped in a diesel engine (not shown) and having a predetermined resistance temperature characteristic, 2 is a battery 3 of a DC power source.
Switch element 4 connected in series to a power supply circuit from the switch to the glow plug 1 is a constant current supply means for supplying a detection current to the glow plug 1 during the opening period of the switch element 5 is a detection current. Temperature detecting means for detecting the temperature of the glow plug 1 based on the voltage drop of the glow plug 1, 6 for detecting the terminal voltage of the glow plug 1 during the closing period of the switching element 2, and 7 for the output of the temperature detecting means 5. Driving time calculation means for calculating an energization time for raising the glow plug 1 to a predetermined temperature in accordance with the above, and 8 for calculating a correction amount of the energization time for the glow plug 1 according to the output of the voltage detection means 6. The voltage correction amount calculation means 9 is an opening / closing element drive signal calculation means for determining the driving time of the switching element 2 based on the outputs of the driving time calculation means 7 and the voltage correction amount calculation means 8. The glow plug control device configured as described above first detects the temperature of the glow plug 1 and calculates the basic drive time by the drive time calculation means 7, then supplies power to the glow plug 1, and after the power supply, the terminal of the glow plug 1 The voltage is detected, the voltage correction amount of the basic drive time is calculated by the voltage correction amount calculation means 8, and the basic drive time is subjected to the voltage correction to calculate and determine the energization time to the glow plug 1.

FIG. 2 is a diagram showing a specific embodiment of the glow plug control device according to the present invention. In the figure, 1 is a glow plug, 2
Is a glow relay, which is an opening / closing element, and 3 is a battery.
Reference numeral 10 is a controller corresponding to the configuration of the constant current supply means 4 or the switching element drive signal calculation means 9 shown in FIG. Input circuit 1
2, a microcomputer 15 having an output circuit 13 for giving an output, and an arithmetic logic unit ALU 14 for executing a control procedure corresponding to information input, and a glow relay 2
The output interface 17 for supplying the output signal of the microcomputer 15 to the constant current circuit 16 for supplying the current for temperature detection and the detection current provided by the constant current circuit 16 correspond to the temperature generated in the glow plug 1. The amplifier circuit 18 that amplifies the voltage drop based on the resistance value to a predetermined level, and the output signal of the amplifier circuit 18 and the terminal voltage during the closed period of the glow relay 2 are converted into digital signals and output to the microcomputer 15. And an AD conversion circuit 19 that operates. Further, in the memory 11 of the controller 10, the characteristic of the energization time corresponding to the detected temperature as shown in FIG. 3 and the characteristic of the correction coefficient corresponding to the terminal voltage as shown in FIG. 4 are input and stored in advance. ing.

Next, the operation of the controller 10 will be described based on the flow chart of FIG. First, start and step S
After initializing all the values in the controller 10 in step 1, the microcomputer 15 turns on the constant current circuit 16 via the output interface 17 in step S2, and this constant current circuit 16 turns on a predetermined constant current. It is supplied to the plug 1, and a voltage drop based on the resistance value corresponding to the temperature of the glow plug 1 at this time is generated. Next, in step S3, the amplifier circuit 18 amplifies this voltage drop, transmits it to the AD conversion circuit 19, and the AD conversion circuit 19 digitally encodes the applied voltage value and transmits it to the microcomputer 15.

Further, the microcomputer 15 obtains the given digital value corresponding to the plug temperature via the input circuit 12 and stores it in a predetermined plug temperature register in the memory 11.

Next, in step S4, the drive time of the glow relay 2 is calculated based on the detected temperature. As shown in FIG. 3, the driving time has a characteristic of an energization time for raising the glow plug 1 to a predetermined control target temperature when the voltage of the battery 3 is a predetermined value (for example, 10.5 V). Since it is stored as an input, it is properly calculated even when the initial temperature of the glow plug 1 is different, and this is stored in the memory 11.

Then, in step S5, the constant current circuit 16 is turned off, and the process proceeds to step S6.

At step S6, the glow relay 2 is turned on via the output circuit 13 and the output interface 17, the preheat timer counter defined in the memory 11 is cleared to zero, and the count is updated at predetermined reference time intervals. Start.

Next, in step S7, when the glow relay 2 is turned on, the terminal voltage applied to the glow plug 1 is changed to the AD conversion circuit 1
It is detected in step 9, and it is stored in the voltage register in the memory 11, and the process proceeds to step S8.

In step S8, the drive time correction amount of the glow relay 2 is calculated based on the detected applied voltage and stored in the memory 11. The drive time obtained in step S4 is 3
Is determined as a predetermined value, and the actual terminal voltage of the glow plug 1 changes depending on the size of the electric load and the state of the battery 3, the correction coefficient corresponding to the terminal voltage shown in FIG. Calculation is decided.

Next, in step S9, the voltage of the preheat timer is corrected. This preheat timer counts up every predetermined reference time, and this reference time is changed in inverse proportion to the terminal voltage by the above correction coefficient.If the voltage is high, the reference time is shortened and the timer is timed up quickly, If it is low, the reference time is lengthened and the timer time is extended to control the temperature of the glow plug 1 to a predetermined value without excess or deficiency for different voltages.

In step S10, the value of the counter of the preheat timer is compared with the value determined in step S4 to make a time-up determination. If no time-up is performed, the control in steps S7 to S10 is executed until the time-up is reached, and the temperature of the glow plug 1 Is controlled.

Next, when the preheat timer times up, the process proceeds to step S11, the glow relay 2 is turned off, and the control ends.

Although the switching element 2 for controlling the power supply to the glow plug 1 is a relay in the above embodiment, other switching elements such as a semiconductor transistor and a thyristor may be used, and the same effect as in the above embodiment can be obtained. .

〔The invention's effect〕

As described above, according to the present invention, in the glow plug control device for the diesel engine, the constant current is applied to the glow plug before the glow plug is energized to detect the temperature from the voltage drop, and the drive time is adjusted according to the temperature rising characteristic. Since it is calculated and the terminal voltage of the glow plug is detected after energization and the energization time is corrected according to this terminal voltage, the glow plug will be glowing regardless of the initial temperature and its terminal voltage. This has the effect of accurately controlling the temperature of the plug. Further, since the voltage applied to the glow plug is directly detected, accurate control can be performed without being affected by wiring resistance or the like.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing the structure of a glow plug control device for a diesel engine of the present invention, and FIG. 2 is a block circuit diagram showing an embodiment of a glow plug control device for the same diesel engine, FIGS. FIG. 5 is a characteristic diagram showing the stored contents of the controller in the glow plug control device of the diesel engine, and FIG. 5 is a flow chart showing the operation of the controller. 1 ... Glow plug, 2 ... Switching element, 3 ... Battery, 4 ... Constant current supply means, 5 ... Temperature detection means, 6 ...
... voltage detection means, 7 ... drive time calculation means, 8 ... voltage correction amount calculation means, 9 ... switching element drive signal calculation means. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A glow plug having a predetermined resistance temperature characteristic, which is mounted on a diesel engine, an opening / closing element connected in series to a power supply circuit to the glow plug, and fixed to the glow plug during the opening period of the opening / closing element. Constant current supply means for supplying the detection current, temperature detection means for detecting the temperature of the glow plug based on the voltage drop of the glow plug due to the detection current, terminal voltage of the glow plug during the closing period of the switching element Detecting means, driving time calculating means for calculating the energization time of the glow plug corresponding to the output of the temperature detecting means, and calculating a correction amount of the energization time corresponding to the output of the voltage detecting means. Switching element drive signal for determining the driving time of the switching element based on the outputs of the voltage correction amount calculation means, the drive time calculation means and the voltage correction amount calculation means Glow plug control apparatus diesel engine comprising comprises a calculation means.