Work vehicle

Patent metadata

Field	Value
Publication number	US-10753407-B2
Application number	US-201916296429-A
Country	US
Kind code	B2
Filing date	Mar 8, 2019
Priority date	Nov 28, 2018
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

Abstract

A work vehicle includes a hydraulic main speed change clutch and a Hi-Lo clutch provided to a power transmission device for transmitting power to drive wheels, and a speed change control device configured to control vehicle speed in multi-stage manner by a combination of the main speed change clutch and the hydraulic Hi-Lo clutch. In shift-up operation for changing the speed from a low speed stage range to a high speed stage range in which a high speed clutch is used, before completion of speed change, the high speed clutch pressure is kept at a first pressure (Pa) higher than the low speed clutch pressure while the pressure of the main speed change clutch, which is a speed change source, is kept, so that the power is transmitted by a combination of the high speed clutch and the main speed change clutch, which is a speed change source.

First claim

What is claimed is:

1. A work vehicle comprising:
a power transmission device configured to transmit rotation power from an engine to drive wheels, the power transmission device comprising a plurality of hydraulic main speed change clutches for a plurality of speed change stages and a hydraulic Hi-Lo clutch having a high speed clutch and a low speed clutch and capable of changing a speed at a high speed stage or a low speed stage, and configured to transmit power via the main speed change clutches and the Hi-Lo clutch;
control valves configured to adjust pressed states of the main speed change clutches and the Hi-Lo clutch; and
a speed change control device configured to:
control and change a vehicle speed in a multi-stage manner by the main speed change clutches and the Hi-Lo clutch, and
perform a shift-up operation for changing a speed from a low speed stage range in which the low speed clutch is used to a high speed stage range in which the high speed clutch is used, wherein the speed change control device is configured to decrease a pressure of the low speed clutch while keeping a pressure of the high speed clutch at a first pressure higher than the pressure of the low speed clutch and keep a pressure of a first clutch of the main speed change clutches that is a speed change source, to transmit power by a combination of the high speed clutch and the first clutch, and thereafter decrease the pressure of the first clutch while increasing the pressure of the high speed clutch, which has been kept at the first pressure and increase the pressure of a second clutch of the main speed change clutches that is a speed change destination.

2. The work vehicle according to claim 1 , wherein the speed change control device is configured to:
operate with an initial time for the first clutch, the initial time calculated on the basis of a reference time until the first clutch reaches a predetermined pressure,
supply an operating oil to an oil chamber for operating the second clutch, while the initial time for the first clutch elapses after a speed change instruction, and
operate with a time period in which
a time for which the pressure of the high speed clutch is kept at the first pressure higher than the pressure of the low speed clutch and
the initial time for the first clutch

elapse at the same time.

3. A work vehicle comprising:
a power transmission device configured to transmit rotation power from an engine to drive wheels, the power transmission device comprising a plurality of hydraulic main speed change clutches for a plurality of speed change stages and a hydraulic Hi-Lo clutch having a high speed clutch and a low speed clutch and capable of changing a speed at a high speed stage or a low speed stage, and configured to transmit power via the main speed change clutches and the Hi-Lo clutch;
control valves configured to adjust pressed states of the main speed change clutches and the Hi-Lo clutch; and
a speed change control device configured to
control and change a vehicle speed in a multi-stage manner by the main speed change clutches and the Hi-Lo clutch, and
perform a shift-down operation for changing a speed from a high speed stage range in which the high speed clutch is used to a low speed stage range in which the low speed clutch is used, wherein the speed change control device is configured to keep a pressure of the high speed clutch at a second pressure higher than a pressure of the low speed clutch, decrease a pressure of a first clutch of the main speed change clutches that is a speed change source, while keeping the pressure of the high speed clutch, start a rise in the pressure of a second clutch of the main speed change clutches that is a speed change destination, and thereafter decrease the pressure of the high speed clutch, which has been kept at the second pressure, and increase the pressure of the low speed clutch.

4. The work vehicle according to claim 3 , wherein the speed change control device is configured to:
operate with an initial time for the low speed clutch, the initial time being calculated on the basis of a reference time until the low speed clutch reaches a predetermined pressure,
supply an operating oil to an oil chamber for operating the low speed clutch while the initial time elapses after a speed change instruction, and
decrease the pressure of the first clutch and start a rise in pressure of the second clutch while the initial time for the low speed clutch elapses.

Assignees

• Iseki Agricult Mach

Inventors

• Ono Koki
• Ishida Tomoyuki
• Kajino Yutaka
• Yoshizawa Yuji
• Murakami Tatsuzo

Classifications

• F16H61/04

  Smoothing ratio shift · CPC title

• F16H61/0276

  Elements specially adapted for hydraulic control units, e.g. valves · CPC title

• F16H61/0265

  for gearshift control, e.g. control functions for performing shifting or generation of shift signals · CPC title

• F16D35/00

  Fluid clutches in which the clutching is predominantly obtained by fluid adhesion (F16D37/00 takes precedence {; arrangements of viscous clutches in four-wheel drives - B60K17/3465 and B60K17/351}) · CPC title

• E02F9/226

  Safety arrangements, e.g. hydraulic driven fans, preventing cavitation, leakage, overheating · CPC title