JPH0455232Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to an engine control device with a simplified input wiring harness. [Prior Art] An engine control unit (ECU) that controls an electronically controlled fuel injection type engine uses a microcomputer, so a variety of controls are possible. However, on the other hand, as the number of inputs increases, the number of wire harnesses increases, causing problems in terms of cost and safety. Figure 3 shows the engine control system of an automatic car.
Two harnesses for the typical neutral position detection signal Snt and starter energization signal Sst that are input to the ECU
FIG. 2 is an explanatory diagram regarding l ₁ and l ₂ . In the figure, ST is a starter switch, NT is a neutral switch, L is a starter (motor coil), R _U is a pull-up resistor, and R _D is a pull-down resistor. As is well known, the starter L cannot be energized unless the neutral switch NT is turned on. When the starter switch ST is turned on, the neutral signal Snt becomes the battery voltage V _B , and if the switch NT is turned on at this time, the starter signal Sst
is also set to _VB , but if it is off, the signal Sst is grounded (GND) through the low resistance starter L. On the other hand, if switch ST is off, the switch
When NT is on, the signals Snt and Sst are both GND, but when switch NT is off, Snt is open (actually, when Snt is open, it becomes V _B with resistor Ru) and Sst becomes GND. The table below summarizes this.

[Problem that the invention attempts to solve]

Looking at it this way, the inputs in Table 1 are unnecessary for the ECU, but if the signals Snt and Sst are treated as binary values, the 2-bit signals Snt and Sst are essential for distinguishing between the three cases. Yes, (when Snt is open, it becomes _VB at resistor R _U ), so two signal lines l ₁ and l ₂ are required. In Table 1 of this invention,
The neutral signal Snt at is ternary V _B ,
Focusing on GND and open, it is possible to input these three signal states with one signal line. [Means for Solving the Problems] The present invention includes a first switch, one end of which is connected to the power supply side, and one end of which is connected to the low resistance load side, in the energization path from the power supply to the low resistance load. and a second switch whose other end is connected to the other end of the first switch, wherein the potential at the connection point between the first switch and the second switch is connected via a signal line. In an engine control device that receives input from an engine, one end of the signal line is connected to a power source via a pull-up resistor and grounded via a pull-down resistor, and the three potentials generated at the connection point of both resistors are used as two standards. A first state in which the first switch is on and the second switch is on, and a second state in which the first switch is off and the second switch is on, as determined by voltage. and a third state in which the first switch is off and the second switch is off. [Operation] In the first state where the first switch is on and the second switch is on, the potential at the connection point of both resistors becomes the power supply voltage, and when the first switch is off and the second switch is on. In a certain second state, the connection point potential becomes the ground potential. In a third state in which the first switch is off and the second switch is off, the potential at the connection point becomes an intermediate voltage obtained by dividing the power supply voltage by both resistors. The engine control device transmits these three potentials into two through one signal line.
A comparative judgment is made using two reference voltages, and the above three states are identified. This will be explained in detail below with reference to the illustrated embodiments. [Embodiment] Figure 1 shows an embodiment of the present invention, in which the starter switch ST is the first switch and the neutral switch.
NT corresponds to the second switch. One end of the starter switch ST is connected to the battery voltage _VB , and both ends of the neutral switch NT are connected to the other end of the starter switch ST and the starter L, respectively. Only the neutral signal line _l1 is connected to the engine control unit ECU (there is no line equivalent to the starter signal line _l2 in FIG. 3). One end of this signal line _l1 is connected within the control device ECU to the battery voltage _VB by a pull-up resistor _R1 , and to the ground potential GND by a pull-down resistor _R2 . CMP ₁ and CMP ₂ are comparators that determine the potential V _IN at the connection point of the resistors R ₁ and R ₂ using different reference voltages V ₁ and V ₂ . These reference voltages V ₁ and V ₂ have a relationship of 0<V ₁ <V _M <V ₂ <V _B , where _VM = V _B ×R ₂ /R ₁ +R ₂ . In other words, the voltage V _M indicates the open state at the connection point between the starter switch ST and the neutral switch NT, and the pull-up resistor R1 and pull-down resistor R2.
This is a value converted into an intermediate voltage between the battery voltage _VB and the ground potential GND. In this way, the voltage of signal line l1 is the battery voltage
There are three potentials: V _B , ground potential GND, and voltage _VM , but in this example, these potentials are set to the reference voltage V ₁ ,
Distinguish with V ₂ . Figure 2 shows the three values that V _IN can take: 0, V _M ,
The above relationship between V _B and reference voltages V ₁ and V ₂ is shown.
V _IN = 0 when starter switch ST is off and neutral switch NT is on (second state)
It is. V _IN = V _M is when both switches ST and NT are off (the open state mentioned above, that is, the third state)
It is. V _IN =V _B when the switch ST is on (first state). At this time, switch NT
may be off, but since this is an abnormal hardware operation, the control unit ECU ignores this. In other words, when V _IN = V _B , control is performed assuming that switches ST and NT are both on (in this case, starting control).
There is no problem even if you do. The table below shows comparator CMP ₁ ,
CMP ₂ output OUT ₁ , OUT ₂ and switches ST, NT
ON, OFF, and the correspondence with Table 1 are also shown.

[Effect of idea]

As described above, according to the present invention, the states of the first and second switches can be input to the engine control device using a single signal line, which reduces wiring harnesses, reduces costs, and improves safety. There are benefits that can be enhanced.

[Brief explanation of the drawing]

FIG. 1 is a main circuit diagram showing an embodiment of the present invention.
FIG. 2 is an explanatory diagram of its operation, and FIG. 3 is a circuit diagram of a main part of a conventional engine control device. In the figure, ECU is the engine control device, ST is the starter switch, NT is the neutral switch, L is the starter, _l1 is the neutral signal line, _R1 is the pull-up resistor, _R2 is the pull-down resistor, CMP ₁ , CMP ₂
is a comparator.

Claims (1)

[Claims for Utility Model Registration] A first switch, one end of which is connected to the power supply side, and a first switch, one end of which is connected to the low resistance load side, and the other end of which is connected to the low resistance load side, in the current conduction path from the power supply to the low resistance load. An engine control system comprising a second switch connected to the other end of the first switch, in which the potential at the connection point between the first switch and the second switch is input via a signal line. In the device, one end of the signal line is connected to a power supply via a pull-up resistor and grounded via a pull-down resistor, and the three potentials generated at the connection point of both resistors are determined using two reference voltages. a first state in which the first switch is on and the second switch is on; a second state in which the first switch is off and the second switch is on; An engine control device that distinguishes between three states: a switch is off and a third state is where the second switch is off.