We continue the story about the automatic transmission MRPA. The first part of the article talked about the mechanical structure of this box. This part of the article will focus on the electronic control of the gearbox..
The automatic transmission electronic control system includes: an electronic control unit, sensors and solenoid valves. Gear changes and torque converter lock-out are carried out at the command of the control unit. The control unit receives signals (information about the state of the elements) from sensors, switches and other control devices. The unit processes the received information and, in accordance with the program, provides control signals to the actuators of the engine control system and automatic transmission. Automatic transmission actuators are solenoid valves for gear shifting, pressure control and torque converter lock-up.
Signals of the electronic automatic transmission control system.
An arrangement of elements of an automatic transmission control system. 1 – engine control unit and automatic transmission, 2 – diagnostic connector, 3 – selector lever lock solenoid valve, 4 – manual shift mode sensor, 5 – safety block-
carriers in the cabin, 6 – fuse No. 9, 7 – fuse No. 10, 8 – fuse No. 5,
9 – pressure sensor of the working fluid in the clutch circuit 2, 10 – speed sensor of the output shaft of the gearbox, 11 – speed sensor of the input shaft of the gearbox, 12 – e / m pressure control valve “A”, 13 – start inhibit switch, 14 – pressure sensor of the working fluid in the clutch circuit 3, 15 – e / m gear shift valve “C”,
16 – e / m gearshift valve “E”, 17 – e / m gearshift valve “B”, 18 – e / m gearshift valve “A”, 19 – automatic transmission fluid temperature sensor, 20 – e / m valve “D” gear changes, 21 – e / m pressure control valves “B” and “C”.
Gear shift control
The electronic control unit constantly monitors the state of the automatic transmission elements and determines which gear should be engaged, then sends control signals to the solenoid valves “A”, “B”, “C”, “D” or “E” of the gear shift.
The gearshift logic control system is designed to control gearshifts at selector positions “D” or “D3”. The electronic control unit compares the real conditions of movement (based on the signals of the sensors) with the states recorded in the memory of the unit and, depending on the situation, sends control signals for making up or down switching.
When shifting gears, the electronic control unit switches on or off (OFF) certain solenoid valves (A, B, C, D or E). The combination of on and off valves is shown in the table “Solenoid valve operation when shifting gears”.
Table. Shifting solenoid valves.
|Selector position||Gear engaged||Solenoid Valve Status|
|D, D3, M||Switching from position “N”||Off||On||On||Off||Off|
|First gear engaged||On||On||On||Off||Off|
|Shift between first and second gear||Off||On||On||Off||Off|
|Second gear included||Off||On||Off||On||Off|
|Shift between second and third gear||Off||On||On||On||Off|
|Third gear engaged||Off||Off||On||Off||Off|
|D, M||Shift between third and fourth gear||Off||Off||Off||Off||Off|
|Fourth gear engaged||On||Off||Off||Off||Off|
|Shift between fourth and fifth gear||On||Off||Off||On||Off|
|R||Switching from position “P” or “N”||Off||On||Off||Off||On|
|Reverse gear engaged||On||On||Off||Off||On|
|Reversing Prohibition Control||On||On||Off||Off||Off|
|P||Parking Mode Enabled||Off||On||Off||Off||On|
|N||Neutral gear engaged||Off||On||On||Off||Off|
Gear Shift Logic
When the car is moving uphill on a winding road with the selector position “D”, the electronic control unit increases the range of permissible speeds for the gear selected. This is to prevent frequent gear changes (between the second and third or between the third and fourth, as well as between the fourth and fifth). Thus, the car can move smoothly. The gearshift program recorded in the control unit automatically engages the most suitable gear and sets the appropriate speed deviation.
While the vehicle is moving downhill with the selector position “D”, the electronic control unit increases the speed value for upshift to increase the range of permissible speeds for the selected gear. Such control, combined with engine braking, gives the most smooth movement. There are three shift modes on the downhill and their corresponding speed range. When driving downhill in fourth gear and depressing the brake pedal, the gear changes to the lowest permissible gear. Acceleration will shift to higher gear.
The electronic control unit controls the solenoid valves A, B and C. When shifting gears, the pressure is controlled by solenoid valves (A, B and C) to ensure smooth engagement (disengagement) of the couplings.
The electronic control unit monitors the state of the elements (by sensor signals), processes the received data and issues control signals to the solenoid valves A, B and C.
Torque Converter Lockout Control
The shift solenoid valve “E” controls the hydraulic valve responsible for turning the torque converter lockout on / off. The electronic control unit controls the torque converter lockout by means of the shift solenoid valve “E” and the pressure control solenoid valve “A”. When the shift solenoid valve “E” is turned on, the torque converter lock-up starts. To control the degree of blocking, using the pressure control solenoid valve “A”, the pressure of the working fluid supplied to the hydraulic lock-on valve is adjusted.
The torque converter lock is engaged in second, third, fourth and fifth gears in the “D” range, in second and third gears in the “D3” band, and also in third, fourth and fifth gears in the “M” band.
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