JPH0444856Y2 - - Google Patents

Description

[Detailed explanation of the idea]

(Industrial Application Field) The present invention relates to a control device for a diesel engine that uses a microcomputer to control energization of a glow plug. (Prior Art) In recent years, there has been a trend toward practical use of control devices that use microcomputers to control not only the operation of diesel engines but also the starting of the engines. By the way, when starting the engine is to be controlled by a microcomputer, the starter motor becomes a load on the battery in addition to the glow plug when starting the engine, so the terminal voltage of the battery drops extremely and the microcomputer starts operating. There was a risk that the system would become inoperable and the predetermined control would be temporarily interrupted. In order to overcome such problems, for example, means for detecting that the power supply voltage has fallen below the normal operating voltage of the control computer and means for detecting the starting state of the engine are provided, and the detection results of these means are In response to this, a device has been proposed in which, when the power supply voltage drops below the above voltage at the time of starting the engine, preheating control of the glow plug is performed by an appropriate backup means in place of the above control computer (Japanese Patent Application Laid-Open No. (See Publication No. 59-68568). In addition, there is a device that compares the input voltage Vin and output voltage Vout of the regulator and forcibly turns on the glow relay circuit when the value of Vin-Vout is less than a predetermined value (Japanese Patent Laid-Open No. 59-65574). (see official bulletin) have also been proposed. (Problem to be solved by the invention) In all of the above-mentioned conventional devices, when the value of the power supply voltage falls below a predetermined level,
Instead of preheating control by a microcomputer, the preheating operation of the glow plug is ensured by an appropriate backup means. However, in such conventional diesel engine control devices, the minimum operating voltage of the microprocessor varies considerably, so the voltage level for switching to the backup means must be set relatively high. It will happen. As a result, there are many situations in which the microprocessor is forcibly switched to a predetermined backup control even though the microprocessor is still in a sufficient operating condition, making it difficult to fully utilize the microprocessor's capabilities. The problem is that it cannot be done. Furthermore, in conventional devices, the required detection circuit must be installed externally to detect a drop in power supply voltage, which increases the number of parts and increases assembly and adjustment costs. It also has (Purpose of the invention) Therefore, the present invention aims to reduce the impedance of a predetermined output port when the starter switch is turned on while performing glow plug preheating control, the battery voltage drops, and the microprocessor stops operating. It is an object of the present invention to provide a control device for a diesel engine in which backup control can be switched according to the capacity of each microprocessor used without increasing the circuit scale. The purpose is (Means for Solving the Problems) In order to achieve the above-mentioned purpose, the diesel engine control device according to the present invention is a diesel engine control device configured to perform glow plug preheating control. It has a first output port and a second output port that are provided separately from each other and enter a high impedance state when the glow plug becomes inoperable, and receives a control signal for preheating control of the glow plug from the second output port. a microprocessor for outputting an output, a means for outputting a starting signal indicating that the diesel engine is in a starting state, a relay means for turning on/off energization to the glow plug, and a first output port in a high impedance state,
In addition, when the diesel engine is in a starting state, the first output port outputs a signal for energizing the glow plug regardless of the control signal from the second output port.
The circuit has a circuit and is provided separately from the first circuit, and when the second output port is not in a high impedance state, a signal for energizing the glow plug is sent in response to a control signal from the second output port. The control circuit includes a second circuit for outputting an output, and a control circuit that supplies an output signal of the first circuit or the second circuit to the relay means as a relay drive signal. (Function) In the present invention, the starter switch is turned on while the glow plug preheating control is being executed, and when the engine is started, the battery terminal voltage decreases, and this decrease in battery voltage is controlled. If the microprocessor for
At the same time, the impedance of a predetermined output port of the microprocessor increases. Therefore,
Regardless of control signals from the microprocessor, proper energization of the glow plug is ensured during cranking. As a result, the backup control can be switched according to the capabilities of the individual microprocessor being used without increasing the circuit scale, and the precision and responsiveness of the backup control has been significantly improved. A control device is realized. (Example) Hereinafter, the present invention will be explained based on the drawings. 1 to 3 are diagrams showing an embodiment of the present invention. First, the configuration will be explained. In FIG. 1, 1 is a diesel engine control device, and the diesel engine control device 1 includes a microprocessor 2.
The microprocessor 2 controls the preheating current supplied from the battery 3 to the glow plugs 4 ₁ to 4 ₄ and controls the predetermined operation of the diesel engine (not shown). Batsuteri 3
A power switch 5 is provided on the positive side of the
The terminal voltage V _B of the battery 3 is supplied via the power switch 5 to a constant voltage circuit 6, and the stabilized voltage V _ST stabilized here is supplied to the power input terminal 2a of the microprocessor 2. Terminal voltage V _B
is also input to the power-on reset circuit 8, and in response to the power switch 5 being turned on, the power-on reset circuit 8 sets the level of its output line 8a to "L" for a predetermined short period of time. This is a known circuit that operates as follows. The block designated by numeral 9 is connected to terminal 2 of microprocessor 2.
This is a program runaway detection circuit that operates in response to the program run signal PR output from the program run signal PR, and when the program run signal PR is output normally, the level of the output line 9a becomes "H".
When the program run signal PR is not output normally, the level of the output line 9a becomes "L". Each output line 8a and 9a has an input AND gate 1
The output line 10a of the AND gate 10 is connected to the reset terminal R of the microprocessor 2. In the illustrated embodiment, the microprocessor 2 is configured to be reset when the level of its reset terminal R becomes "L", and at least one of a program runaway or power-on condition occurs. When the microprocessor 2 is reset, the microprocessor 2 is reset. Glow plug 4 ₁ by microprocessor 2
In order to execute the energization control calculation for preheating of 4 to ₄ , the input terminal 2c of the microprocessor 2 is connected to the
In addition to being applied with a starting signal ST given by the closing of the starter switch 11, a sensor unit K sends data D regarding the operating conditions of the engine.
has been entered. Microprocessor 2 has
A control program necessary for preheating control of the glow plugs 4 ₁ to 4 ₄ is stored, and predetermined control calculations are performed in response to data D and a start signal ST. The microprocessor 2 has output terminals 2d and 2e that enter a high impedance state when it becomes impossible to continue normal operation due to a drop in the voltage applied to the power input terminal 2a. This output terminal 2
A control signal CS for controlling the energization of the glow plugs 4 ₁ to 4 ₄ is output from e. Therefore, the output terminal 2d constitutes the first output port of the present application, and the output terminal 2e constitutes the second output port of the present application.
The microprocessor 2 is configured to execute calculations for controlling the preheating of the glow plug as well as for controlling the operation of the engine, but since this has little relation to the present invention, a detailed explanation will be omitted. . The control signal CS and the start signal ST are input to a control circuit 13 for controlling a glow plug relay 12 that turns on and off preheating current supplied from the battery 3 to the glow plugs _{4 1} to 4 ₄ . In the control circuit 13, OP1 and OP2 are differential amplifiers,
T ₁ , T ₂ are transistors, R ₁ to _{R 16} are resistors, D ₁ ,
D ₂ , D ₃ and D ₄ are diodes, OP1,
OP2 consists of the same package. differential amplifier
OP1 and OP2 are supplied with terminal voltage V _B as a power supply voltage via power switch 5 and resistor R ₁₀ , and resistors R ₂ and OP1 are connected to the inverting input terminal side of OP1.
A first bias circuit 15 consisting of R ₃ is provided. On the other hand, there is a resistor on the non-inverting input terminal side.
A second bias circuit 16 consisting of R ₄ and R ₅ is provided. First and second bias circuits 15,1
A stabilizing voltage _VST is applied to the differential amplifier OP1, and a predetermined bias voltage is applied by the first and second bias circuits 15 and 16 to the inverting input terminal and the non-inverting input terminal of the differential amplifier OP1. ing. And the output terminal of differential amplifier OP1 is diode D ₃
It is connected to the output of the constant voltage circuit 6 via a resistor R ₇ and to its non-inverting input terminal via a resistor R ₈ . Resistor R ₂ , which determines the operating state of the differential amplifier OP1,
The values of R ₃ , R ₄ , R ₅ , and R ₆ are such that when the level of the start signal ST is "L" and the output port 2d is in a high impedance state, the level of the non-inverting input terminal is slightly higher than the level of the inverting input terminal. and its output level is set to be "H" (second
(see figure). Further, on the inverting input terminal side of the differential amplifier OP2, a voltage dividing circuit 17 consisting of resistors R ₁₃ and R ₁₄ is connected.
is provided, and its non-inverting input terminal side is connected to the output terminal 2e of the microprocessor 2 via a resistor _R16 . A stabilizing voltage V _ST is applied to the resistor R ₁₃ of the voltage divider circuit 17.
The values of R ₁₃ and R ₁₄ are determined so that when the output port 2e is in high impedance, the level of the inverting input terminal is slightly lower than the level of the non-inverting input terminal, and the output level becomes "H". (See Figure 3). On the other hand, since the starting signal ST is applied to its inverting input terminal via the voltage divider formed by resistors R ₁ and R ₆ and the diode D ₁ , the starting signal ST is
When the level of ST is "L", the diode _D1 is in a reverse bias state and the operation of the differential amplifier OP1 is not affected. The voltage divider formed by resistors R ₁ and R ₆ is configured so that the voltage applied to the anode of diode D ₁ is sufficiently higher than the potential on its cathode side when the level of starting signal ST becomes "H". Since the values of resistors R ₁ and R ₆ are determined in , when the output port 2d is in a high impedance state, the output of the differential amplifier OP1 changes in response to the level of the start signal ST becoming "H". Level is "L"
becomes. Therefore, if the output port 2d is in a high impedance state, the output level of the differential amplifier OP1 changes according to the level of the start signal ST.
Here, if the level of the output signal of 2d is "H", the output level of the differential amplifier OP1 is always "H" no matter what the level of the start signal ST is.
(In other words, since the output of 2d is programmed to always be "H", the only possible states of the output of 2d are "H" and "high impedance"). In response to the output level of the differential amplifiers OP1 and OP2 becoming "L", the amplifier circuit 18 consisting of transistors T ₁ and T ₂ and resistors R ₉ and R ₁₁ activates the relay coil of the glow plug relay 12. This is a circuit for supplying sufficient excitation current to switch 12a to turn on relay switch 12b. Therefore, differential amplifier OP1, resistors R ₁ to R ₈ , R ₁₀ , and diodes
D ₁ and D ₃ constitute the first circuit C1 of the present application, and differential amplifier OP2, resistors R ₁₃ and R ₁₄ , and diode D ₄ constitute the second circuit C2 of the present application. Here, the diode _D2 is a diode for preventing the back electromotive voltage generated in the relay coil 12a due to the switching operation of the transistor _T2 from being applied to the transistor _T2 . If the glow plug has not yet reached the predetermined temperature, the lamp display device 1 is activated by the display signal IS output from the microprocessor 2.
9 is differentially actuated to turn on an indicator lamp (not shown). When the temperature of the glow plug reaches a predetermined temperature, the indicator lamp is turned off by the indicator signal IS. The reference numeral 14 designates a starter relay, which is activated in response to the closing of the starter switch 11 to control the supply of drive current to a starter motor (not shown). Next, the operation will be explained. First, when the power switch 5 is turned on, the voltage of the battery 3 is applied to the control circuit 1 via the power switch 5.
At the same time, the stabilized voltage V _ST from the constant voltage circuit 6 is supplied to the microprocessor 2 and part of the control circuit 13 . At this time, the power-on reset circuit 8 is activated to reset the microprocessor 2. After this, the microprocessor 2 executes a control program for preheating control, and outputs a control signal CS according to the result to the output port 2.
Output from e. When the level of the control signal CS output in accordance with the preheating control calculation result in the microprocessor 2 reaches the "L" level state indicating a command to execute the preheating operation, as already explained, the inverting input terminal of the differential amplifier OP2 becomes lower than the level of its non-inverting input terminal, the output level of the differential amplifier OP2 becomes "L", and the relay switch 12b is closed. As a result, a preheating current is applied to each of the glow plugs ₄₁ to ₄₄ , and when the glow plug temperature reaches a startable value, the lamp display device 19 is activated in response to the display signal IS output from the microprocessor 2.
is activated, notifying the completion of preheating the glow plug. Thereafter, when the starter switch 11 is closed by the operator, the starter relay 14 is energized and a starter motor (not shown) is operated. The level of the control signal CS remains "L" even during engine cranking operation by the starter motor.

[Table] As described above, according to the above configuration, the microprocessor 2 performs the control operation until the power supply voltage reaches the unique lowest differential voltage that brings the output port 2d into the high impedance state. The characteristics of the microprocessor 2 can be maximized without making any individual adjustments depending on the characteristics of the microprocessor 2. Further, the control of the glow plug relay 12 before and after the drive signal of the microprocessor 2 is lowered is controlled by the separate first and second circuits C1 according to the outputs from the respective separate output ports 2d and 2e. , C2. Therefore, it is easy to distinguish the signal level in each circuit, and the accuracy of backup control can be significantly improved.In addition, it is no longer necessary to switch the output signal of the output port, and the responsiveness of backup control is significantly improved. can do. (Effects) According to the present invention, when the starter switch is turned on while the glow plug preheating control is being executed, and the battery voltage drops and the microprocessor stops operating, the impedance of the specified output port increases. Even if there are variations in the operating voltage characteristics of the microprocessor,
Even without making individual adjustments in consideration of this variation, backup processing for glow plug preheating control during cranking can be reliably performed in accordance with the capabilities of the individual microprocessors used. As a result, if the battery voltage drops,
The preheating limit of the glow plug is controlled by the microprocessor to the limit of the capability of each microprocessor used, which significantly improves the performance compared to the conventional one. Since no circuit means is required, a significant reduction in cost can be expected, and a high-performance, low-cost control device can be realized. Furthermore, since the first and second output ports are provided separately, and the first and second circuits are provided separately, the accuracy and responsiveness of backup control can be significantly improved.

[Brief explanation of the drawing]

1 to 3 are diagrams showing one embodiment of the diesel engine control device according to the present invention, FIG. 1 is its circuit diagram, and FIG. 2 explains the action of the output terminal 2d of the microprocessor. FIG. 3 is a timing chart for explaining the operation of the output terminal 2e of the microprocessor. 1... Diesel engine control device, 2... Microprocessor, 2d... Output port (first output port), 2e... Output port (second output port), 3... Battery, 4 ₁ to 4 ₄ ... Glow plug, 6 ... Constant voltage circuit, 11 ... Starter switch, 12 ... Glow plug relay, 13 ... Control circuit, C1 ... First circuit, C2 ... Second circuit,
CS...Control signal, ST...Starting signal, V _ST ...Stabilizing voltage, V _B ...Terminal voltage.

Claims (1)

[Scope of utility model registration request] In a diesel engine control device configured to perform preheating control of glow plugs, two separate first and second glow plugs are provided, each of which enters a high impedance state when it becomes inoperable due to a drop in drive voltage.
an output port and a second output port;
a microprocessor that outputs a control signal for preheating control of the glow plug from an output port;
means for outputting a starting signal indicating that the diesel engine is in a starting state; a relay means for turning on/off energization to the glow plug; and a first output port is in a high impedance state, and the diesel engine is in a starting state. In the case where the glow plug is provided with a first circuit that outputs a signal for energizing the glow plug regardless of the control signal from the second output port, the second output It has a second circuit that outputs a signal for energizing the glow plug when the port is not in a high impedance state in response to a control signal from the second output port, and the output signal of the first circuit or the second circuit is A control device for a diesel engine, comprising: a control circuit that provides a relay drive signal to a relay means.