Honda Pilot: A/T System Description - Clutches and Gears

The six speed automatic transmission applies hydraulic pressure to the clutches to engage or disengage the gears. When hydraulic pressure is introduced into the clutch drum, the clutch piston moves and presses the steel plates and the clutch discs. Power is then transmitted through the engaged clutch pack to its gear mounted on the shaft. Likewise, when the hydraulic pressure is bled from the clutch drum, the piston releases the steel plates and the clutch discs. Then the steel plates rotate with the clutch drum, and the clutch discs rotate with gear on the shaft. The clutch discs are released from the steel plates. This allows the clutch disc to spin independently, transmitting no power.

Transmission Cutaway View

With AWD

Without AWD

1st Clutch

he 1st clutch engages/disengages 1st gear, and is located at the right end of the secondary shaft. The 1st clutch is supplied hydraulic pressure through the secondary shaft by a circuit connected to the internal hydraulic circuit.

2nd Clutch

The 2nd clutch engages/disengages 2nd gear, and is located at the left end of the secondary shaft. The 2nd clutch is joined back-to- back to the 5th clutch. The 2nd clutch is supplied hydraulic pressure through the secondary shaft by a circuit connected to the internal hydraulic circuit.

3rd Clutch

The 3rd clutch engages/disengages 3rd gear, and is located at the left end of the mainshaft. The 3rd clutch is joined back-to-back to the 6th clutch. The 3rd clutch is supplied hydraulic pressure through the mainshaft by a circuit connected to the internal hydraulic circuit.

4th Clutch

The 4th clutch engages/disengages 4th gear, and is located at the right end of the third shaft. The 4th clutch is supplied hydraulic pressure through the third shaft by a circuit connected to the internal hydraulic circuit. The vehicle also moves backward when the 4th clutch is engaged while the reverse selector hub engages with the reverse gear.

5th Clutch

The 5th clutch engages/disengages 5th gear, and is located at the left end of the secondary shaft. The 5th clutch is joined back-to- back to the 2nd clutch. The 5th clutch is supplied hydraulic pressure through the secondary shaft by a circuit connected to the internal hydraulic circuit.

6th Clutch

The 6th clutch engages/disengages 6th gear, and is located at the left end of the mainshaft. The 6th clutch is joined back-to-back to the 3rd clutch. The 6th clutch is supplied hydraulic pressure through the mainshaft by a circuit connected to the internal hydraulic circuit.

One-Way Clutch

The one-way clutch is located between the countershaft 1st gear and the park gear. The park gear is splined with the countershaft.

The countershaft 1st gear engages the outer race surface of the one-way clutch, and the park gear engages the inner race surface of the one-way clutch. The one-way clutch locks when power is transmitted from the secondary shaft 1st gear to the countershaft 1st gear. The 1st clutch and 1st gear remain engaged in 1st, 2nd, 3rd, 4th, 5th, and 6th gear ranges in D or D4 driving mode. However, the one-way clutch disengages when the 2nd, 3rd, 4th, 5th, or 6th clutches and gears are applied in D or D4 driving mode. This is because the rotational speed of the countershaft exceeds that of 1st gear, which causes the one-way clutch to free-wheel with the 1st clutch still engaged.

Gear operation

Gears on the mainshaft:

• 3rd gear is engaged/disengaged with the mainshaft by the 3rd clutch.
• 6th gear is engaged/disengaged with the mainshaft by the 6th clutch.
• 4th gear is splined with the mainshaft and rotates with the mainshaft.

Gears on the secondary shaft:

• 1st gear is engaged/disengaged with the secondary shaft by the 1st clutch.
• 2nd gear is engaged/disengaged with the secondary shaft by the 2nd clutch.
• 5th gear is engaged/disengaged with the secondary shaft by the 5th clutch.
• Idler gear is splined with the secondary shaft, and rotates with the secondary shaft.

Gears on the third shaft:

• 4th gear is engaged/disengaged with the third shaft by the 4th clutch.
• Reverse selector hub is splined with the third shaft and rotates with the third shaft.
• Reverse selector on the reverse selector hub switches between the reverse gear and 6th gear.

Gears on the countershaft:

• Final drive gear is integral with the countershaft.
• 2nd gear, 5th gear, and park gear are splined with the countershaft, and rotate with the countershaft.
• 1st gear is engaged with the park gear splined with the countershaft by the one-way clutch when accelerating. It is disengaged from the park gear by the one-way clutch when decelerating.

Gears on the idler gear shaft:

• Idler gear is press-fitted with the idler gear shaft, and rotates with the idler gear shaft.
• Idler gear is engaged with the mainshaft 4th gear and the secondary shaft idler gear, and transmits the mainshaft rotation to the secondary shaft.

A/T System Description - Clutches and Gears

Input shaft revolution decreases or increases by transferring to some of planetary gear sets and/or clutches, and it is output to the differential assembly through the spur pinion driven by the planetary carrier on planetary gear set 4.

Clutch

Dog clutches A and F use dog type clutch that can be operate in low oil pressure condition. Clutches B, C, D, and E use a multi-disk clutch. Dog clutch A is interconnected between the input shaft and ring gear on planetary gear set 1/the sun gear on planetary gear set 2. Clutch B is interconnected between the input shaft and sun gear on planetary gear set 1. Clutch C has a role to brake and it is interconnected between the sun gear on planetary gear set 1 and the transmission housing. Clutch D has a role to brake and it is interconnected between the ring gear on planetary gear set 2 and the transmission housing. Clutch E is interconnected between the input shaft and the planetary carrier on planetary gear set 3/the ring gear on planetary gear set 4. Dog clutch F has a role to brake and it is interconnected between the sun gear on planetary gear set 3/4 and the transmission housing.

Clutch Connecting Condition Chart

Planetary Gear Set

Planetary gear set 1 and 2 are arranged they are overlapping. The ring gear of planetary gear set 1 and the sun gear of planetary gear set 2 are in a integral structure, and planetary carrier 1 and 2 that have four planetary pinions in their own respectively are common part.

Planetary gear set 3 and 4 are arranged in parallel. The planetary carrier of the planetary gear set 3 and the ring gear of the planetary gear set 4 are in a integral structure and the sun gear of planetary gear set 3 and 4 are common part.

Planetary Gear Operation

The following explanations is an example of a general planetary gear set operation.

Deceleration

The input of the ring gear is transmitted to the planetary pinion. The Planetary pinion rotates and revolves around the sun gear because the sun gear is blocked. The Planetary carrier is rotated by the planetary pinion revolution in the same direction of the input, and the rotation speed decelerates compared to the initial input speed.

Direct Connection

If the ring gear and planetary carrier are rotated in the same speed as an input, the planetary pinion would not rotate and the ring gear and planetary carrier would rotate as a set because the ring gear and planetary carrier revolution are synchronizing. When the sun gear is not blocked, the planetary carrier is rotated integrated with ring gear and sun gear to the same direction and the same speed as an input. Even if the ring gear and the sun gear are rotated in the same speed, the planetary carrier is integrally rotated.

Acceleration

The input of the ring gear and the sun gear are transmitted to the planetary pinion. If the sun gear rotation speed is higher than that of the ring gear, the planetary pinion is rotated by the sun gear in reverse direction of the input. In this case, the planetary carrier is rotated by the planetary pinion in the same direction of the input.

The planetary carrier rotation speed accelerates compared to the initial input speed because the planetary carrier is rotated by the ring gear, and also rotated by the planetary pinion.

Reverse

The input of the sun gear is transmitted to the planetary pinion. The planetary pinion is rotated in the reverse direction of the input, and revolved around the sun gear in the reverse direction of the input because the planetary carrier is blocked. The ring gear is rotated by the planetary pinion revolution in the forward direction of the planetary pinion, and the rotation speed decelerates compared to the initial input speed.

In this automatic transmission, the planetary carrier is not blocked and ring gear is rotated to the reverse direction of the sun gear by another planetary gear set and its revolution speed accelerates compared to the sun gear.

A/C System Description - OverviewA/T System Description - Electronic Control System