JP3242421B2 - Bulldozer automatic transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transmission for a bulldozer.

[0002]

2. Description of the Related Art Conventionally, in a bulldozer provided with a transmission composed of a torque converter with a lock-up device and a gear type transmission with a manual transmission, an operator judges the load on the vehicle and determines the shift speed. Choose and do the work.

[0003]

In the operation of a bulldozer, the load fluctuates very frequently and the range of fluctuation is wide. Therefore, it is impossible to cover the entirety with one speed stage, and a transmission having a plurality of speed stages is required. For this reason, the operator must frequently perform the speed change operation, which is troublesome, and requires skill to properly judge the load and select an appropriate speed position. For this reason, there is a problem that work is often not performed at a gear suitable for the load, and the work efficiency is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an automatic transmission for a bulldozer capable of automatically selecting an optimum speed stage according to a load and performing an efficient operation. It is intended to provide.

[0005]

In order to solve the above-mentioned problems, in an automatic transmission for a bulldozer according to the present invention, a lock for controlling separation and joining of a lock-up device is provided.
Torque control with lock-up device with up control valve
It has a shifter and a shift control valve that controls shifting between speed stages.
, I-th,..., N-th gear-type transmission.
Equipped with a torque converter with lock-up device
Bulldozer that transmits to the gear type transmission via the
Between the i-th stage and the (i + 1) -th stage
When shifting gears, the vertical and horizontal axes indicating traction and running speed are also measured.
Separate the lock-up devices drawn on the same degree graph
A first traction force curve showing the first traction force W1 when the
2 shows the second traction force W2 when the backup device is joined.
In the “W1 ≦ W2” region obtained from the second traction force curve,
In order to automatically connect the lock-up device,
A control signal is sent to the backup control valve and the shift control valve.
And a control device .

[0006]

According to the above arrangement, the first stage,..., The i-th stage,.
The gear type transmission having the n-th speed stage is the i-th speed stage
The first traction force W1 when the lockup device is separated at
And the second traction force W when the lockup device is joined
The vehicle speed when 2 is equal to the vehicle speed is defined as a vehicle speed vi. Actual vehicle speed is car
When the speed is lower or higher than vi,
Machine automatically activates the lock-up device while maintaining the i-th stage.
To separate or join. Further, the gear type transmission is the (i +
1) When the lock-up device is separated at the speed
When the third traction force W3 is equal to the second traction force W2
Is the vehicle speed v (i + 1). The actual vehicle speed is v (i
+1), the gear type transmission is shifted to the i-th stage.
Change the speed and connect the lock-up device. Real car
When the speed is higher than the vehicle speed v (i + 1), the gear type
Speed change to the (i + 1) th gear and lock up
Separate the device. Depends on normal torque converter performance
For example, the second traction force W2 is obtained when the vehicle speed is the vehicle speed vi and the vehicle speed v (i +
1), the first traction force W1 and the third traction force W3
Greater than both. Thus, the lock-up device
Separating / joining and shifting between gear stages of gear type transmission at the same time
Automatically controls for maximum traction at all times
Since the vehicle travels at different speeds, high working efficiency can be maintained. Ma
In addition, the separation and joining of the lock-up device and the shifting between the gears
Gear gear transmission with twice the number of speed stages
Substantially equivalent output characteristics are obtained. This makes it cheap and lightweight
Transmission device can be obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an automatic transmission for a bulldozer according to the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an automatic transmission, wherein 1 is an engine, 2
Is a torque converter, 3 is a lock-up device, 4 is a lock-up control valve for controlling ON-OFF of the lock-up device, and 5 is a forward / reverse lever. 1
0 is a gear type transmission, 11 is a forward clutch, 12
Is a reverse clutch, 13 is a first speed clutch, and 1
4 is a 2nd speed clutch, and 15 is a 3rd speed clutch.
Reference numeral 16 denotes a vehicle speed detector for detecting a transmission output shaft rotation speed, that is, a vehicle speed, reference numeral 17 denotes a horizontal shaft device, and reference numeral 18 denotes a sprocket. Reference numeral 20 denotes a transmission control valve for controlling the transmission, and 2
1 is a reverse clutch valve, 22 is a forward clutch valve, 23 is a third speed clutch valve, 24 is a second speed clutch valve, and 25 is a first speed clutch valve. Reference numeral 26 denotes a control device, which includes a lock-up control valve 4 and a forward-reverse
, A vehicle speed detector 16, a reverse clutch valve 21, a forward clutch valve 22, a third speed clutch valve 23, a second speed clutch valve 24, and a first speed clutch valve 25, respectively.

FIG. 2 shows a running performance curve of a bulldozer.
The vertical axis indicates the tractive force, and the horizontal axis indicates the vehicle speed. The dotted line shows the running performance curve by the torque converter (torque converter).
1 is the first speed, 32 is the second speed, and 33 is the third speed. The solid line is the running performance curve when the lock-up device is turned on,
41 is the first speed, 42 is the second speed, and 43 is the third speed. As is clear from the figure, the performance curve of the torque converter and the performance curve of the lock-up cross each other at points a, b, c, d, and e, and the torque converter first speed 31 shows the maximum traction force in a low speed range from the point a. ,
The first-speed lock-up 41 is between a and b, the second speed 32 is the torque converter between b and c, and the second speed 42 is the lock-up between c and d.
However, between d and e, the torque converter third speed 33 and the lockup third speed 43 show the maximum traction force in the higher speed range than e.

Next, the operation will be described with reference to the flowchart of FIG. In step 102, the forward / reverse lever 5 is operated to move forward or backward. In step 103, the control device 2
It is determined in step 6 whether or not the vehicle is moving forward.
At 4, the control signal is transmitted to the forward clutch valve 22 and the first speed clutch valve 25, and the vehicle is started with the forward clutch ON and the torque converter first speed ON. When the vehicle starts accelerating, at step 105, the vehicle speed V is detected by the vehicle speed detector 16 and a signal is sent to the control device 26.
A of the performance curve of FIG.
The speed v1 at the point is compared with the vehicle speed V. If V ≧ v1 is YES, a control signal is sent to the lockup device 4 in step 107 to turn on the lockup first speed. If V≥v1 is NO in step 106, the process returns to step 104 to maintain the torque converter first speed. Hereinafter, as shown in the flowchart, while the above procedure is repeated, the speed stage of the transmission is switched as the vehicle speed increases. When the vehicle starts and accelerates, control signals for the first speed and the separation are output to the shift control valve 20 and the lock-up control valve 4, respectively, and the vehicle is traveling on the torque converter 1st speed on 31 in FIG. When the vehicle speed V increases and reaches v1, the control signal for the first speed is output to the shift control valve 20, and instead of the separation, the control signal for joining is output to the lock-up control valve 4, and the first-speed control signal is output to the lock-up control valve 4. It travels between a and b on 41 in FIG. Vehicle speed V is v
2, the second speed and separation control signals are transmitted to the shift control valve 20.
2 is output to the lock-up control valve 4 and travels between bc on 32 in FIG. During traveling between bc and 32, when the load increases and the vehicle speed V reaches v2, control signals for the first speed and the joining are output to the shift control valve 20 and the lockup control valve 4 to lock up. Drive in first gear. When the vehicle speed V decreases to v1, the control signal for separation is output to the lock-up control valve 4 while the control signal for the first speed is output to the shift control valve 20, and the vehicle runs at the first speed of the torque converter. As a result, the vehicle always travels along the line of maximum traction indicated by the thick dotted line and the solid line in the performance curve of FIG. In the case of deceleration, the speed stage is switched according to the same procedure.
If the forward / reverse lever is set to reverse in step 102, the result in step 103 is NO, and in step 204, the reverse clutch is turned on and the torque converter first speed is turned on. The following operation is the same as in the forward movement.

[0010]

As described in detail above, the present invention comprises a vehicle speed detector and a control device for transmitting control signals to the lock-up control valve and the shift control valve when the vehicle speed reaches the speed to be shifted. The optimum speed stage is automatically selected . Also, always output the maximum traction force.
Automatically control the separation and joining of the lock-up device
I have. These eliminate the need for complicated shifting operations.
In addition , even if the operator is an unskilled person, the vehicle always runs at the gear position that exhibits the maximum output, and an automatic bulldozer transmission that can maintain high work efficiency can be obtained. Furthermore, while controlling the separation and joining of the lock-up device,
Only by controlling the shift between the shift speeds, it is possible to obtain output characteristics substantially equivalent to those of a large and expensive gear type transmission having twice the number of speed stages. Thus, an inexpensive and lightweight transmission having excellent output characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an automatic transmission according to the present invention.

FIG. 2 is a running performance curve of a bulldozer.

FIG. 3 is a flowchart of an automatic shift.

FIG. 4 is a flowchart of the automatic shift following FIG. 3;

[Explanation of symbols]

 2 Torque converter 3 Lock-up device 4 Lock-up control valve 5 Forward / reverse lever 10 Transmission 16 Vehicle speed detector 20 Shift control valve 26 Control device

Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F16H 61/14 E02F 3/84 B60K 41/22 F16H 59/00-61/12 F16H 61/16-61/24 F16H 63 / 40-63/48

Claims (1)

(57) [Claims] 1. A method for controlling separation and joining of a lock-up device.
Lock-up device with lock-up control valve
Shift control for controlling the shift between the speed converter and the speed converter
, I-th,..., N-th gear type
Torque control with lock-up device
Transmission to the gear type transmission via the barter to make it run freely
In a bulldozer transmission , the traction force is applied when shifting between the i-th stage and the (i + 1) -th stage.
The vertical and horizontal axes indicating the speed and the running speed are also drawn on the same graph with the scale
Traction force W1 when the locked-up device is separated
And the lock-up device
From the second traction force curve showing the second traction force W2 when
The lock-up device automatically in the "W1≤W2" area
The lock-up control valve and the
An automatic transmission for a bulldozer, comprising: a transmission for transmitting a control signal to a transmission control valve .