JP2819464B2 - Automatic transmission for wheel loader - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic transmission for a wheel loader. 2. Description of the Related Art Wheel loaders are usually used to excavate the ground with a bucket and load it into a dump truck. FIG. 4 shows a series of operation patterns from excavation of the wheel loader to loading on the dump truck. This is the most frequently used operation pattern called so-called V-shave operation. And this V shave operation (operations I to V indicated by arrows)
In order to minimize the working time, the following operation is required. That is, when the wheel loader a advances forward at the second forward speed (F2) toward the ground b at a high speed (driving I) and approaches the ground b (0.5 m to 1.0 m), the tractive force when performing excavation work Plunge into ground b at forward I speed (FI) to increase
II). When the excavation is completed, the wheel loader a is moved backward at the second reverse speed (R2) from the excavation work position (operation III). ). Dump truck c
When the loading operation to the vehicle is completed, the vehicle leaves the dump truck c at R2 at high speed (operation V). However, an automatic transmission vehicle that automatically shifts the transmission speed stage during the above work has already been proposed by the present applicant. In this case, the vehicle starts and runs after switching between F and R (driving I). , III, I
V, V) is always the second speed, and only when the vehicle speed is lower than the set vehicle speed, such as during excavation (driving II), the I-speed shift down is performed. (Problems to be Solved by the Invention) When the above-mentioned work is performed by the conventional automatic transmission (same as that of a passenger car, etc.), even if it is not desired to downshift, when the vehicle speed falls to the set vehicle speed, the vehicle is automatically turned off. For example, 4
The shift down from 3 → 2 → 1st speed causes the following problems. (1) Excavation 1 when loading work such as V shave
I want to work at 2nd speed, except dropping to speed. However, when switching between forward and reverse, the throttle pedal is loosened to reduce the vehicle speed by braking, so the vehicle speed becomes lower than the set value,
Downshifts automatically from 2 to 1st gear. When the gear is shifted down from the second gear to the first gear, the vehicle speed drops sharply and a sudden brake is applied, so that the cargo is spilled and the operator is uncomfortable, and smooth work cannot be performed. (2) When traveling between sites, such as loading a load, if the vehicle is coasted from a medium or high speed and the vehicle is decelerated without using a brake, the vehicle is automatically shifted down according to the dropped vehicle speed. Each time, the load suddenly drops, and the brake is suddenly applied, so that the cargo is spilled, and the operator feels uncomfortable and cannot travel smoothly. SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide an automatic transmission that does not cause a downshift in a voluntary running of an automatic transmission with a throttle pedal loosened. (Means for Solving the Problems) The present invention has been made in view of the above points, and based on a signal indicating a speed stage, electrically changes a speed stage of a transmission to a speed stage indicated by the signal. In a transmission of a wheel loader equipped with an electric transmission control device that performs manual transmission and automatic transmission changeover, when the manual transmission and automatic transmission changeover switch is switched to manual transmission, the transmission shift lever When the vehicle speed stage is selected based on the signal and the automatic speed change is performed, the automatic speed change is not performed when the engine speed is lower than the set speed, and the currently selected speed stage is maintained. When the engine speed becomes higher than the set speed, the setting signal output from the controller is set so that the speed stage is set according to the vehicle speed at that time. Means for operating the transmission shift solenoid valve according to the signal.When switching between forward and reverse during loading work during V-shave operation and voluntary running during running, the throttle pedal is loosened to reduce the engine speed. Utilizing dropping, when the engine speed reaches a certain speed or less,
The currently selected speed stage is maintained to prevent spillage of the load and operator discomfort. (Example) Next, an example of the present invention will be described with reference to the drawings. FIG. 1 (a) is an outline of a vehicle to which the present invention is applied, and employs an electric transmission control for electrically shifting a transmission gear to a gear indicated by the signal based on the signal indicating the gear. The wheel loader is shown. FIG. 1 (b) shows the arrangement of the driver's seat lever in FIG. 1 (a). In these figures, 1 is a directional lever,
Numeral 2 denotes a range lever (these are collectively referred to as a transmission shift lever) for detecting a position by ON / OFF of a contact. Reference numeral 3 denotes a steering handle. Reference numeral 6 denotes a speed stage holding function-fully automatic changeover switch, which is an important point of the present invention.
To detect the ON state. Reference numeral 5 denotes a boom lever, and reference numeral 7 denotes an operator's seat, which is arranged at the driver's seat as shown in FIG. 8 is a transmission shift solenoid valve, and 9 is a controller. FIG. 2 is a block diagram showing the configuration of the controller. In the drawing, a directional position detection sensor 1 ', a range lever position detection sensor 2', an access pedal position detection sensor 3 ', an automatic manual changeover switch 4', and a speed stage holding function-fully automatic changeover switch 6 which are input sides are a controller 9. Connected to the ON-OFF detection circuit 11
The position or ON state is detected by N-OFF. A vehicle speed detection sensor 5 ', which is also an input side, and an engine rotation sensor 6' are connected to a rotation detection circuit 12 of the controller 9. Each of these detection means and switches on the input side and the transmission shift solenoid valve 8 on the output side
The controller 9 is interposed between the controller 9 and the controller 9. The controller 9 includes the detection circuits 11 and 12 as described above, and further includes a CPU.
It has a program memory 15, a transmission shift solenoid valve drive circuit 16, and provides an appropriate setting signal calculated by the CPU 14 based on each input signal to the transmission shift solenoid valve 8 as an output. According to the present invention, as described above, during the coasting operation during the forward / reverse switching of the loading operation time of the V-shave or the like and during coasting during traveling, the engine rotation is reduced to a predetermined rotation speed by using the throttle pedal being loosened. When the number is less than the number, the currently selected speed stage is maintained. FIG. 3 shows the operation in a flowchart.
The automatic manual switch 4 'performs a so-called manual shift in which the speed stage is selected depending on the position of the range lever 2 whether it is automatic or manual, and in the case of manual. (Refer to A) In the case of the automatic mode, automatic shifting is performed as shown in B, and upshifting and downshifting are performed according to vehicle speed. As for A and B, there is no difference from the conventional one. The present invention is characterized in that a portion indicated by X is added. When an automatic shift is selected in the control flow of FIG. 3, a control circuit such as X is entered. That is, the automatic shifting here is to perform a control like X, and does not include the normal automatic shifting (the vehicle speed is determined only by the vehicle speed). In this manner, when the engine speed is lower than the set speed (including the case where the speed is changed from the high speed to the low speed), the currently selected speed stage is maintained without performing the automatic shift and the engine speed is maintained. When the speed becomes larger than the set rotation speed from the low speed rotation, the speed stage is selected at that time according to the vehicle speed. If you are now running in 3rd or 4th speed, loosen the throttle pedal and enter coasting, and the vehicle stops or reach a vehicle speed close to it, when you depress the throttle again and accelerate again, the speed remains at 3 or 4 speed If so, acceleration is poor and smooth driving cannot be performed. Therefore, the vehicle speed is re-accelerated at a certain vehicle speed or lower, and when the engine speed becomes equal to or higher than the set engine speed, the vehicle automatically shifts down to the second speed stage of 4 → 2 or 3 → 2 to enable smooth running. . Note that the second gear is used instead of the first gear. The first gear is set with a reduction ratio so that the required large traction force can be obtained during excavation, and the normal gear is set so that it starts from the second gear. Because it is. When the present invention is implemented, in addition to the conventional manual shift-automatic shift switch 4 ', when the automatic shift is selected, the function of the present invention and the conventional automatic shift are added to the operator. Is provided near the wrist rest (handstand), or the above two switches are integrated in the same place to select a manual shift, a conventional automatic shift, and three modes of the function of the present invention. A switch may be provided. Further, the present invention is applicable to both automatic transmission vehicles and both automatic transmission and manual transmission vehicles, and is also applicable to two-speed automatic exchange vehicles and 1234... Automatic transmission. Of course, the throttle pedal opening may be used instead of sensing the engine rotation. (Effects of the Invention) The present invention is configured as described above in detail, and utilizes the forward switching of the loading operation during the V-shave operation, and the reduction of the engine speed by loosening the throttle pedal during the voluntary operation during the operation. Then, when the engine speed reaches a predetermined speed or less, while maintaining the currently selected speed stage,
When the number of revolutions becomes equal to or higher than the predetermined number of revolutions, an automatic transmission that sets a speed stage according to the vehicle speed at that time can be obtained. Therefore, the present invention completely eliminates a situation in which the load was spilled due to a sudden brake being applied due to a downshift and the operator was uncomfortable, and a smooth work can be performed. it can.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (a) is a schematic view of a vehicle to which the present invention is applied, FIG. 1 (b) is a layout view of a driver seat lever of FIG. 1 (a), FIG. FIG. 3 is a block diagram of the configuration of the controller according to the present invention, FIG. 3 is an operation flowchart of the present invention, and FIG. 4 is an explanatory diagram showing an operation pattern from the excavation of the wheel loader to the loading operation onto the dump truck. 4 Wrist rest 6 Speed stage hold-fully automatic switch 8 Transmission solenoid valve 9 for shift shift Controller 11 ON / OFF detection circuit 12 Rotation detection circuit 14 CPU 16 Transmission Solenoid valve drive circuit for

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Claims (1)

(57) [Claims] A transmission for a wheel loader equipped with an electric transmission control device for electrically shifting the transmission speed stage to the speed stage indicated by the signal based on the signal indicating the speed stage, and having a manual shift-automatic shift switch When the manual shift-automatic shift switch is switched to manual shift, the vehicle speed is selected based on a signal from the transmission shift lever, and when the automatic shift is switched, the engine speed is set to the set speed. If the engine speed is lower than the number, the currently selected speed stage is maintained without performing automatic gear shifting, and if the engine speed is higher than the set speed, the speed stage is set according to the vehicle speed at that time. Means for operating the transmission shift solenoid valve according to the setting signal output from the controller. Characterized Rukoto, automatic transmission wheel loader.