JPH08113049A - Car speed stage switching device of working vehicle - Google Patents

Abstract

PURPOSE: To carry out the simultaneous operation of steering at work time, switching of car speed stages, switching of an advance and a retreat and a work machine lever without shifting both hands to/from each other by arranging a shift up switch, a shift down switch, a hold switch or the like in a grip part of a steering monolever. CONSTITUTION: In a car speed stage switching device of a work vehicle having a speed changer to switch car speed stages to/from each other by plural solenoid valves and a work machine lever to operate a work machine, a steering monolever 10 is arranged in a position on the lateral opposite side of the work machine lever. A shift up switch 3 to shift car speed stages one stage by one stage to high speed from low speed and a shift down switch 4 to shift the car speed stages by one stage by one stage to low speed from high speed are arranged in a grip part of this steering monolever 10. Similarly, an advance- retreat switch 6 and a hold switch 5 to select whether or not a prescribed car speed stage is fixed when the advance-retreat switch 6 is switched to the prescribed car speed stage, are arranged in the grip part of the steering monolever 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle speed stage switching device for a work vehicle, particularly a wheel loader.

[0002]

2. Description of the Related Art A conventional wheel loader has a wheel handle for steering, a gear shift lever and a forward / backward movement lever are mounted beside the handle shaft, and a bucket is raised or lowered, and soil is extracted or discharged. The work equipment lever for performing the above is attached to the side of the driver's seat (usually on the right side). When soil, etc. are collected, transported, and loaded on a truck with such a wheel loader, the following operations are performed.

First, the forward / reverse lever is switched to forward, and in order to travel at a high speed to near the earth and sand, the speed lever is used to switch the vehicle speed stage from the first speed to the second speed or the third speed. Next, while operating the handle with one hand, step on the accelerator to move forward, and with the other hand, operate the work implement lever to prepare for soil sampling of the bucket. When approaching the soil, push the bucket into the soil, and at the same time operate the gear shift lever to decelerate as needed, and finally squeeze into the soil with the maximum force. Must. For this purpose, one hand must be released from the work implement lever, the handle should be grasped, and the shift lever should be operated with the other hand to make the first speed. After that, the handle and the work implement lever are squeezed again, and then the work implement lever is used to gradually raise the bucket to adjust the amount of earth and sand to be put into the bucket and to move forward.

When the inside of the bucket is filled with earth and sand and the bucket is completely lifted upward, traveling is stopped and the forward / reverse lever is switched to reverse. At this time, in order to improve work efficiency, the vehicle speed is often increased from the first speed to the second speed, and if possible, to the third speed. Therefore, before traveling, it is necessary to release the hand from the handle again and operate the gear shift lever. Next, in preparation for loading dirt on the truck, operate the work equipment lever with one hand to raise the bucket to a position where it can travel with the other hand facing up while simultaneously operating the handle with the other hand. Drive backward while changing the.

When the vehicle comes to the fixed position, the traveling is stopped, the forward / reverse lever is switched to forward, and the vehicle travels forward toward the loading position on the truck. When approaching a truck, in order to stop the vehicle at the desired loading location with the optimal vehicle orientation and vehicle speed while raising the bucket to a height at which it can be loaded, operate the work implement lever, handle and shift lever operation. It must be made.

As described above, there are a large number of simultaneous operations such as handle operation, speed change lever operation, work machine lever operation, and forward / backward movement lever operation during operation. It is very difficult to perform this operation quickly, and the skill level of the operator greatly affects the work efficiency. Further, even a skilled operator has a problem in that he is likely to get tired even in a short working time because the number of operations for changing his / her hands is very large.

In order to solve this problem, in the first prior art (Japanese Patent Publication No. 3-30024), there is one in which a changeover switch is provided at the grip portion of the working machine lever. According to this, when the changeover switch is turned on while the vehicle speed stage other than the first speed is being selected for forward movement, the first speed solenoid valve can be forcibly switched to the first speed by energizing the solenoid valve. Further, when the forward / reverse lever is switched to the reverse while the vehicle speed stage other than the first speed is selected in the forward direction and the changeover switch is turned on as described above, energization is switched to the original solenoid valve other than the first speed, It is possible to shift from 1st speed to high speed. In this way, deceleration from the high speed just before entering the soil to the 1st speed can be easily done by the changeover switch on the grip of the work equipment lever, and it is also possible to increase the speed from the 1st speed to the original high speed before and after moving backward. It became possible by switching the advance lever.

In order to solve the above-mentioned problems, in the second prior art (Japanese Patent Laid-Open No. 5-501021), a mono-lever grip for steering is provided with a changeover switch for selecting a vehicle speed stage and a forward / reverse changeover switch. Is proposed. According to this monolever, the steering control of the vehicle can be performed in the same manner as a steering wheel by tilting the whole monolever with one hand to the left and right, and the thumb for the hand operating the monolever can be used to switch the vehicle speed stage changeover switch on the upper surface of the grip of the monolever. The vehicle speed can be selected by switching, and the forward / backward changeover switch on the front face of the grip portion of the monolever can be switched by the index finger and the middle finger of the hand that also operates the monolever.

Therefore, by providing such a monolever and the working lever on the left and right sides of the driver's seat and at positions where it is easy for the operator to operate with one hand, the steering lever and the changeover switch for selecting the vehicle speed stage can be provided. It is possible to operate the forward / reverse switch and the work implement lever simultaneously with both hands, which is an improvement over the conventional method of operating the handle.

[0010]

However, in the above-mentioned first prior art, the forward / reverse switching must be operated by operating the forward / backward lever provided beside the handle shaft. Therefore, in order to operate the forward and backward levers frequently while operating the handle and the work implement lever, the operator must alternately carry these three operating parts with both hands and operate. Had a problem that he was tired easily. Also, for example, when it is necessary to travel at first speed in order to get over the unevenness of the ground when starting in reverse,
After shifting the forward / reverse lever to reverse, change the vehicle speed from the 2nd speed to the 1st speed with the speed change lever, or after changing the vehicle speed from the 2nd speed to the 1st speed with the speed change lever without using the changeover switch, After plunging into, the forward / reverse lever must be moved backward. Since it is necessary to perform such a gear shifting operation while selecting an operation suitable for the work situation, there is also a difficulty in operating both hands.

In the device using the monolever shown in the second prior art, a rotary changeover switch is used as the changeover switch for speed selection. In general, rotary changeover switches have larger outer dimensions than other switches and are often expensive. Further, the lever for operating the speed selection changeover switch needs to have a long lever length in order to reduce the force for rotating the shaft of the switch itself, that is, the operating force. For this reason, the outer diameter of the grip portion of the monolever tends to be large, and the manufacturing cost tends to be high.

In order to solve the above-mentioned problems, the present invention provides a vehicle speed change device for a wheel loader, which is capable of simultaneously performing steering, vehicle speed change, forward / reverse change and working machine lever without changing both hands. Can do the operation,
Also, a vehicle speed change device with improved operability is provided, in which the operating lever for this purpose can be made small and inexpensive, and the vehicle speed after switching between forward and reverse can be quickly switched to a vehicle speed suitable for the working situation. The purpose is to do.

[0013]

In order to achieve the above object, a vehicle speed change device for a work vehicle according to the present invention is provided with a transmission for changing the vehicle speed by a plurality of solenoid valves and a work for operating the work machine. In a vehicle speed change device for a work vehicle having a machine lever, the work machine lever installed in a driver's seat, and a steering mono-lever installed in the driver seat at a position opposite to the work machine lever on the left and right sides to steer the vehicle. 1
0, a shift-up switch 3 mounted on the grip portion of the steering mono-lever 10 for shifting the vehicle speed step by step from low speed to high speed, and a shift-up switch 3 mounted on the grip portion of the steering mono-lever 10, The shift down switch 4 for shifting the gear from high speed to low speed one by one, the forward / reverse switch 6 mounted on the grip portion of the steering monolever 10 for switching between forward, neutral and reverse, and the steering monolever 10. The holding switch 5 is mounted on the grip and selects whether or not the predetermined vehicle speed is fixed when the forward / reverse switch 6 is switched at the predetermined vehicle speed.

When the hold switch 5 is selected on the hold side, the vehicle speed is 1st and the forward / reverse switch 6 is selected.
When the vehicle speed is switched from forward or reverse, the vehicle speed is fixed at 1st speed. When the non-hold side is selected, the vehicle speed is 1st and when the forward / reverse switch 6 is switched from forward or reverse, the vehicle speed is set to 1. It may be set to other than speed.

The shift-up switch 3 is located on the right side of the upper surface of the grip portion of the steering monolever 10 and can be easily operated by the thumb of the left hand when the steering monolever 10 is gripped from the front by the left hand. Mounted in position,
The shift down switch 4 is mounted on the left side of the upper surface of the grip portion of the steering monolever 10 and at a position where the thumb of the left hand can be easily operated when the monolever 10 for steering is gripped from the front by the left hand. The hold switch 5 is mounted on the right side surface of the grip portion of the steering monolever 10 and at a position that can be easily operated by the thumb of the left hand when the steering monolever 10 is gripped from the front by the left hand. The forward / reverse switch 6 is located on the front surface side of the grip portion of the steering monolever 10, and when the steering monolever 10 is gripped from the front by the left hand, it can be easily operated by the index finger or the middle finger of the left hand. May be attached to. Each of these switches according to the present invention is mounted at a position where it is easy to operate with each finger of the left hand.
When the steering monolever 10 is to be operated by the right hand, it is desirable to mount the steering monolever 10 at a position where it can be easily operated by each finger of the right hand.

[0016]

When the shift up switch 3 or the shift down switch 4 is pushed with the thumb of the hand operating the steering mono-lever 10, the vehicle speed is shifted one step to a high speed step or a low speed step each time the push button is pressed. . When the forward / reverse switch 6 is switched by the index finger or the middle finger of the hand operating the steering monolever 10, the traveling direction changes to forward or backward. Therefore, the steering operation, the vehicle speed changeover, and the forward / reverse travel changeover can be performed with one hand, and the operation with the work implement lever can be performed simultaneously. Further, the shift-up switch 3, the shift-down switch 4, and the hold switch 5 are push button switches to form an inexpensive and small steering monolever.

The hold switch 5 selects whether or not the vehicle speed stage after the forward / reverse switch 6 is switched from forward or backward at a predetermined vehicle speed stage, for example, 1st speed is fixed to 1st speed. If you want to travel at a high speed stage in reverse after shifting to first speed immediately before plunging into the soil in forward running, select hold switch 5 to the non-hold side and switch forward / reverse switch 6 from forward to reverse to achieve first speed. From other than 1st speed.
Also, if you want to travel in the first speed in reverse as well, after shifting to the first speed immediately before plunging into the soil in forward running, select the hold switch 5 to the hold side and move the forward / backward switch 6
When is switched from forward to reverse, it is fixed at 1st speed. In this way, the hold switch 5 allows the vehicle speed after the forward / reverse switch 6 is switched from forward or reverse to be quickly selected to suit the working situation.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vehicle speed change device according to the present invention will be described in detail below with reference to the drawings. FIG.
FIG. 1 shows a steering mono-lever 10 of a vehicle speed stage switching device showing a first embodiment according to the present invention. Each switch of this lever is provided at a position where it can be easily operated by the finger of the hand holding the lever. In this embodiment, this lever is configured to be operated by the left hand, but it can be operated by the right hand. Can be configured to.

In FIG. 1, a shift-up switch 3 and a shift-down switch 4 are shift switches provided on the right side and the left side of the upper surface of the grip portion of the steering monolever 10 at positions where it is easy to operate with a thumb. Both are momentary push button switches. Hold switch 5
Is on the right side of the grip of the steering monolever 10,
Similarly, it is an alternate push button switch provided at a position where it is easy to operate with the thumb, and the contact is turned on or off each time it is pushed. The forward / reverse switch 6 is a changeover switch provided on the front surface side of the grip portion of the steering monolever 10 and at a position where it is easy to operate with the index finger or the middle finger.
Select neutral and reverse.

FIG. 2 is a control circuit diagram of a vehicle speed stage switching device showing a first embodiment according to the present invention. In this embodiment, the number of vehicle speed stages is three, but it can be configured in other cases. In this circuit, power is supplied from the battery 1 via the main switch 2. One of the a-contacts of the shift-up switch 3 and the shift-down switch 4 is connected to the power supply line, and the other is connected to the exciting coils of the relay 30 and the relay 40, respectively. Also, the exciting coil of the relay 40 is energized.

The contact 5a of the hold switch 5 turns on when the hold side is selected and turns off when the non-hold side is selected. The contacts 5a of the hold switch 5 are the a contacts 61a and the b contacts 6 of the relay 60 described later.
1b is connected in parallel, and this parallel circuit is connected to the exciting coil of the relay 50. The other side of the parallel circuit is connected to the b contact 31b of the relay 30.
An a contact 41a of the relay 40 and an a contact 81a of a relay 80 described later are connected in series, and this series circuit and an a contact 51a of the relay 50 are further connected in parallel. One of the parallel circuits is connected to the power supply line, and the other is connected to one of the b contacts 31b of the relay 30.

Since the output common terminal of the forward / reverse switch 6 is connected to the power supply line and the neutral output terminal is connected to the exciting coil of the relay 60, the exciting coil of the relay 60 is energized when the neutral is selected. The relay 50
B contact 52b and a b contact 91b of a relay 90 described later are connected in series, and one of the series circuits is connected to the power supply line.
The other end is connected to the exciting coil of the relay 70.

The b contact 42b of the relay 40 and the b contact 32b of the relay 30 are connected in series, and the series circuit and the a contact 82a of the relay 80 are further connected in parallel. One of the parallel circuits is connected to the power supply line, and the other is connected to the relay 80 via the a contact 71a of the relay 70.
It is connected to the exciting coil of. The a-contact 33a of the relay 30 and the a-contact 83a of the relay 80 are connected in series, and the series circuit and the a-contact 92a of the relay 90 are further connected in parallel. One of the parallel circuits is connected to the power supply line, and the other is connected to the exciting coil of the relay 90 via the b contact 43b of the relay 40.

One of the a-contact 53a of the relay 50, the a-contact 72a of the relay 70, and the a-contact 93a of the relay 90 is connected to the power supply line, and the other is connected to the first speed solenoid 100 and the second speed solenoid 110, respectively. And the third speed solenoid 120. Incidentally, the relay 30, the relay 40, the relay 50, the relay 70, the relay 8
The 0 and the relay 90 are well-known relays that are activated when the exciting coil is energized to reverse the contact, and are deactivated when not energized to restore the contact. The relay 60 is a known ratchet relay whose contacts are reversed only when the exciting coil is energized, which will be described in detail later.

Next, the operation of the control circuit in the first embodiment will be described. For convenience of description, the case where the hold switch 5 is selected on the hold side, that is, the case where the contact 5a is on will be described first. FIG. 3 shows a control circuit time chart when the contact 5a is ON, and the operation of the shift up switch 3 and the shift down switch 4 will be described with reference to this.

Immediately after the power is turned on, the shift-up switch 3 and the shift-down switch 4 are not pressed, so that the exciting coils of the relays 30 and 40 are not energized. Therefore, since the a-contact 41a of the relay 40 is off, the exciting coil of the relay 50 is not energized. Similarly, since the a-contact 33a of the relay 30 is off, the exciting coil of the relay 90 is not energized. B contact 52b of relay 50
And energizing the exciting coil of the relay 70 through the series circuit of the b-contact 91b of the relay 90 and the a-contact 53
Only the a contact 72a of the a, a contacts 72a, and a contacts 93a is turned on to drive the second speed solenoid. The 1st speed solenoid 100, the 2nd speed solenoid 110, and the 3rd speed solenoid 120 are solenoids which operate so that the vehicle speed stage corresponding to each may be set. Thus, in this embodiment, the vehicle speed is set to the second speed immediately after the power is turned on.

By energizing the exciting coil of the relay 70, a
The contact 71a is turned on, and the b contact 32b of the relay 30
Since the b contact 42b of the relay 40 is turned on, the exciting coil of the relay 80 is energized. At this time, since the a contact 82a of the relay 80 is turned on, the self-holding circuit of the relay 80 operates.

When the shift-up switch 3 is pressed while the vehicle is in the 2nd speed, the exciting coil of the relay 30 is energized. Even if the b-contact 32b of the relay 30 is turned off, the self-holding circuit of the relay 80 causes the relay 80
Keeps the excitation state, the a-contact 83a remains on. Therefore, the exciting coil of the relay 90 is energized by the series circuit of the a-contact 33a of the relay 30, the a-contact 83a of the relay 80, and the b-contact 43b of the relay 40. By energizing the exciting coil of the relay 90, the relay 90 b
Since the contact 91b is turned off, the energization of the exciting coil of the relay 70 is cut off. Since the exciting coil of the relay 40 is not energized, the a-contact 41a of the relay 40 remains off, and thus the exciting coil of the relay 50 remains unenergized.

Further, since the a contact 71a of the relay 70 is turned off, the energization of the exciting coil of the relay 80 is cut off. Even if the a contact 83a of the relay 80 is turned off, or the shift-up switch 3 is released to release the relay 30.
The excitation coil of the relay is de-energized and the a contact 3 of this relay 30
Even if 3a is turned off, since the a contact 92a of the relay 90 is turned on, the self-holding circuit of the relay 90 operates and the relay 9
0 keeps the excitation state.

Therefore, the a contact 72a of the relay 70 is turned off to stop energizing the second speed solenoid, and the relay 90
The a-contact 93a is turned on to drive the third speed solenoid.
In this way, the vehicle speed stage is set to the third speed.

It is assumed that the downshift switch 4 is pressed next while the vehicle is in the third gear. Since the exciting coil of the relay 40 is energized and the b-contact 43b is turned off, the energization of the exciting coil of the relay 90 is cut off and the self-holding of the relay 90 is released. Since the a contact 81a of the relay 80 is off, even if the a contact 41a of the relay 40 is turned on, the exciting coil of the relay 50 is not energized. Therefore,
B-contact 52b of relay 50 and b-contact 91b of relay 90
The exciting coil of the relay 70 is energized through the series circuit of.

Although the a contact 71a of the relay 70 is turned on,
Since the b contact 42b of the relay 40 is off, the exciting coil of the relay 80 remains de-energized. Therefore, when the shift down switch 4 is released, the excitation coil of the relay 40 is de-energized and the b contact 42b of the relay 40 is turned on, so that the excitation coil of the relay 80 is energized.
Therefore, the a contact 81a of the relay 80 is turned on after the a contact 41a of the relay 40 is turned off.
The exciting coil of is left unenergized. At this time, the a contact 82a of the relay 80 is turned on, so the relay 8
The self-holding circuit of 0 is working. This state is the same as the state immediately after the power is turned on, and the third speed solenoid is deactivated and the second speed solenoid is activated. Therefore, the vehicle speed stage is set to the second speed again.

If the downshift switch 4 is further pressed while the vehicle is in the second gear, the exciting coil of the relay 40 is energized. Even if the b-contact 42b of the relay 40 is turned off, the self-holding circuit of the relay 80 keeps the relay 80 in the excited state.
Remains on. Since the contact 5a of the hold switch 5 is on, the a contact 41a of the relay 40, the a contact 81a of the relay 80, and the b contact 3 of the relay 30.
The exciting coil of the relay 50 is energized by the series circuit with 1b. The energization of the exciting coil of the relay 50 turns off the b-contact 52b of the relay 50, so that the energization of the exciting coil of the relay 70 is cut off. Since the exciting coil of the relay 30 is not energized, the a contact 33 of the relay 30
a remains off, and the exciting coil of the relay 90 remains de-energized.

Further, since the a contact 71a of the relay 70 is turned off, the energization of the exciting coil of the relay 80 is cut off. Even if the a contact 81a of the relay 80 is turned off, or the shift-down switch 4 is released, the relay 40
Even when the energization of the exciting coil is cut off and the a contact 41a of the relay 40 is turned off, the a contact 51a of the relay 50 is turned on, so that the self-holding circuit of the relay 50 operates and the relay 50 keeps the excited state.

Therefore, the a contact 72a of the relay 70 is turned off to stop energizing the second speed solenoid, and the relay 50
The a-contact 53a is turned on to drive the first speed solenoid.
In this way, the vehicle speed stage is set to the first speed.

The operation when the shift-up switch 3 is pressed in the first speed is almost the same as that described above, but will be briefly described. Since the exciting coil of the relay 30 is energized by the shift-up switch 3 and the b contact 31b is turned off, the energization of the exciting coil of the relay 50 is cut off and the self-holding of the relay 50 is released. After that, even if the shift-up switch 3 is released and the b contact 31b of the relay 30 is turned on, the a contact 41a of the relay 40 is turned off, so that the exciting coil of the relay 50 remains unenergized. is there. Since the a contact 83a of the relay 80 is off, even if the a contact 33a of the relay 30 is turned on, the relay 9
The 0 excitation coil is not energized. Therefore, the exciting coil of the relay 70 is energized via the series circuit of the b-contact 52b of the relay 50 and the b-contact 91b of the relay 90.

Although the a contact 71a of the relay 70 is turned on,
Since the b contact 32b of the relay 30 is off, the exciting coil of the relay 80 remains de-energized. Therefore, when the shift-up switch 3 is released, the energization of the exciting coil of the relay 30 is cut off and the b contact 32b of the relay 30 is turned on, so that the exciting coil of the relay 80 is energized.
Therefore, the a contact 83a of the relay 80 is turned on after the a contact 33a of the relay 30 is turned off.
The exciting coil of is left unenergized. At this time, the self-holding circuit of the relay 80 is operating as described above. In this way, the vehicle speed stage is set to the second speed again.

As can be seen from the above description, when the shift up switch 3 or the shift down switch 4 is pressed with the hold switch 5 selected to the hold side,
Each time the vehicle is pushed, the vehicle speed shifts one speed to high speed or low speed.

Next, with the vehicle speed set to the first speed,
Move the forward / reverse switch 6 from forward or reverse to neutral,
Alternatively, the operation when switching from neutral to forward or reverse will be described. Even if the forward / reverse switch 6 is switched to operate the relay 60, the contact 5a of the hold switch 5 connected in parallel with the a-contact 61a and the b-contact 61b of the relay 60 is on, so that the operation of the relay 60 does not occur. It does not substantially affect the operation of the relay 50. That is, even if the forward / reverse switch 6 is switched while the exciting coil of the relay 50 is energized, the exciting coil of the relay 50 remains energized, and the vehicle speed remains the first speed.

As described above, when the hold switch 5 is selected to the hold side, the vehicle speed is fixed at the first speed and the vehicle speed is fixed at the first speed even when the forward / reverse switch 6 is switched. Of. Since the exciting coil of the relay 50 is not energized when the vehicle speed is the second speed or the third speed,
The operating state of the relay 60 does not affect the operation described above. Therefore, even if the forward / reverse switch 6 is switched, the vehicle speed remains the same as the second speed or the third speed.

On the other hand, regarding the operation when the hold switch 5 is selected to the non-hold side, that is, when the contact 5a of the hold switch 5 is off,
This will be described below. In the state where the forward / reverse switch 6 is not switched, the operating state of the relay 60 does not change, so the on / off state of the contact 61a or the contact 61b of the relay 60 also does not change. Therefore, the operation of the relay 50 when the shift up switch 3 or the shift down switch 4 is pressed in this state is the same as the contact 5 of the hold switch 5 until now.
The operation is exactly the same as when a is on. Also,
The other relays are unaffected by the operating state of relay 60. Therefore, in the state in which the forward / reverse switch 6 is not switched, the operation is exactly the same as when the shift up switch 3 or the shift down switch 4 described above is pressed, and therefore the description thereof is omitted here.

When the vehicle speed is set to the second speed or the third speed, the exciting coil of the relay 70 or the relay 90 is energized, and the exciting coil of the relay 50 is not energized. Even if the relay 60 is actuated by switching the switch 6, the operation described so far is not substantially affected as described above. Therefore, the operation at this time is exactly the same as the above description, and the description thereof will be omitted.

Now, a case where the vehicle speed is the first speed and the forward / reverse switch 6 is switched will be described. Relay 60 here
Is a known ratchet relay that operates as shown in FIG. That is, this relay has its contact reversed only when the exciting coil is energized. Therefore, the relay 60 operates only when the forward / reverse switch 6 is switched from forward or reverse to neutral. Times t1 and t2 shown in the time chart of FIG. 4 are the operation time from when the contact b 61b is turned off to when the contact a 61a is turned on when the relay 60 is activated, and the contact a 61a when the relay 60 is activated next time. B contact 61b after turning off
It is the operating time until it turns on. Between t1 and t2, the a contact 61a and the b contact 61b are off, and the contact 5a of the hold switch 5 is also off.
The energization of the exciting coil of the relay 50 of FIG. 2 is cut off.

From the above, the relay 60 is switched every time the forward / reverse switch 6 is switched from forward or reverse to neutral.
The contact is reversed, so that the exciting coil of the relay 50 is de-energized. The operation at this time is as follows in the description in the state where the contact 5a of the hold switch 5 is on.
This is exactly the same as in the case where the vehicle speed is 1st speed and the shift-up switch 3 is pressed to turn off the b-contact 31b of the relay 30.
Therefore, when the vehicle speed is set to the first speed and the vehicle is switched from forward or reverse to neutral, the vehicle speed becomes the second speed.

On the other hand, when the forward / reverse switch 6 is switched from neutral to forward or backward, the contact of the relay 60 is not reversed, so that the operation of the relay 50 and other relays is not affected. Therefore, switching from neutral to forward or reverse when the vehicle speed is set to 1
The vehicle speed remains the same as the first speed.

Generally, the times t1 and t2 shown in the time chart of FIG. 4 are about 20 ms, and the time from the interruption of the energization of the exciting coil of the relay 50 to the return of the contacts is 10 ms or less. Is. To cut off the energization of the exciting coil of the relay 50 and completely restore the contact, the forward / reverse switch 6 is set to the neutral position.
It is necessary to stay for more than 00 ms. In a normal operation, since the switching time of the forward / backward switch 6 takes 200 ms or more, there is no problem in interrupting the energization of the exciting coil of the relay 50.

According to the vehicle speed changeover device of this embodiment, as shown below, steering, vehicle speed changeover, and forward / reverse changeover can be performed with one hand during work, and vehicle speed changeover after forward / reverse changeover can also be carried out in a working condition. You can select a suitable operation. (1) When it is desired to change the vehicle speed after switching from the forward first speed to the reverse speed to a speed other than the first speed a) Operate the steering monolever 10 with the left hand. The thumb of the same hand selects the hold switch 5 to the non-hold side, and the middle finger switches the forward / backward switch 6 to forward. B) Press the shift up switch 3 or shift down switch 4 with the left thumb to set the vehicle speed. While traveling forward, if necessary, the shift up switch 3 or the shift down switch 4 is pushed to shift the vehicle speed.
Operate the work implement lever with your right hand to prepare for the entry of sediment. C) Immediately before entering the earth and sand, press the downshift switch 4 to change the vehicle speed to the 1st speed. Gradually raise the bucket with the work equipment lever (right hand) and move forward. D) After traveling is stopped, the forward / reverse switch 6 (left index finger) is switched to reverse. At this time, the vehicle speed is automatically switched from the first speed to the second speed. E) Move backward while lifting the bucket with the work equipment lever (right hand), and press the shift-up switch 3 (left thumb) to shift the vehicle speed to high speed if necessary.

(2) When it is desired to set the vehicle speed stage to the 1st speed after switching from the 1st forward speed to the reverse speed (a) The steering monolever 10 is operated with the left hand. The hold switch 5 is selected to the hold side with the thumb of the same hand, and the forward / reverse switch 6 is switched to the forward direction with the middle finger. B) Press the shift up switch 3 or shift down switch 4 with the left thumb to set the vehicle speed. While traveling forward, if necessary, the shift up switch 3 or the shift down switch 4 is pushed to shift the vehicle speed.
Operate the work implement lever with your right hand to prepare for the entry of sediment. C) Immediately before entering the earth and sand, press the downshift switch 4 to change the vehicle speed to the 1st speed. Gradually raise the bucket with the work equipment lever (right hand) and move forward. D) After traveling is stopped, the forward / reverse switch 6 (left index finger) is switched to reverse. At this time, the vehicle speed stage remains at the 1st speed. E) Move backward while lifting the bucket with the work equipment lever (right hand), and press the shift-up switch 3 (left thumb) to shift the vehicle speed to high speed if necessary. As described above, according to the hold switch 5, it is possible to select the function for automatically changing the vehicle speed stage during reverse travel according to the operation suitable for the working situation.

Now, the second embodiment according to the present invention will be described below. FIG. 5 is a control circuit diagram of a vehicle speed change device according to a second embodiment of the present invention. Explaining that the circuit configuration of this embodiment is different from that of the first embodiment, the a-contact 61a of the relay 60 is not connected to anything. The other connections are exactly the same. Further, in the present embodiment, the relay 60 is a known relay that operates as shown in FIG. That is, the relay 60 has its contact inverted every time the exciting coil is energized or de-energized. The operation of this embodiment is different from that of the first embodiment so far only when the vehicle is in the first speed with the contact 5a of the hold switch 5 being off and the forward / reverse switch 6 is switched. Will be described.

As shown in FIG. 6, the relay 60 inverts its contact each time the forward / reverse switch 6 is switched from forward or reverse to neutral or from neutral to forward or reverse. Time t3 shown in the time chart of FIG.
Is the time during which the forward / reverse switch 6 remains in the neutral position. During this time t3, the contact b 61b is off and the contact 5a of the hold switch 5 is also off, so that the excitation coil of the relay 50 is deenergized.

From the above, the relay 60 is switched every time the forward / reverse switch 6 is switched from forward or reverse to neutral.
The b-contact 61b is turned off, so that the excitation coil of the relay 50 is de-energized. The operation at this time is exactly the same as in the case where the contact 5a of the hold switch 5 is on, as in the case where the vehicle speed is the first speed and the shift-up switch 3 is pressed to turn off the b contact 31b of the relay 30 in the description. . Therefore, when the forward speed or the reverse speed is switched to the neutral when the vehicle speed is the first speed, the vehicle speed becomes the second speed. In neutral, the b contact and relay of relay 61
Since both the a contacts 5a of the field switch 5 are off,
You cannot shift the vehicle speed to 1st gear. Therefore, even if the vehicle is switched from neutral to forward or reverse, the vehicle speed remains the second speed or the third speed.

In this case, when the forward / reverse switch 6 is switched from forward or reverse when the vehicle speed is the first speed, the speed is always other than the first speed. Therefore, the vehicle speed stage switching device according to the second embodiment is effective when it is necessary to always set the high speed stage at the start of forward or reverse. Since the operation time from energizing the exciting coil of the relay 60 to turning off the contact b is generally 10 ms or less, in this case as well, the switching operation of the normal forward / reverse switch 6 causes the relay 50 to operate. There is no problem in shutting off the energization of the exciting coil.

[0053]

According to the present invention, the handgrip portion of the steering monolever 10 can be operated by operating the working machine lever with one hand and operating the steering monolever 10 with the other hand without releasing the hand from the lever. Shift up switch 3, shift down switch 4, hold switch 5,
Also, since the forward / reverse switch 6 can be operated, it is possible to perform steering, vehicle speed stage switching, forward / backward switching, and simultaneous operation of the work implement lever during work. Further, since the shift-up switch 3, the shift-down switch 4, and the hold switch 5 are small and inexpensive push button switches, the steering monolever 10 can be compact and inexpensive. The effects of the present invention are the same even if the positions at which the shift-up switch 3 and the shift-down switch 4 are mounted are opposite to each other.

Further, according to the present invention, when the hold switch 5 provided on the steering monolever 10 is selected to the non-hold side, the vehicle speed is automatically changed when the forward / reverse switch 6 is switched to the reverse after working at the first forward speed. Therefore, it is possible to set a high speed stage other than the first speed, and the number of times of vehicle speed stage switching operation at the time of reverse travel can be reduced. On the contrary, when the forward / reverse switch 6 is switched to reverse after the work at the first forward speed, in a work situation in which the high speed cannot be achieved, the forward / reverse switch 6 can be simply selected by selecting the hold switch 5 on the hold side. After switching, it will be possible to work at 1st speed.

[Brief description of drawings]

FIG. 1 is an external view of a steering mono-lever of a vehicle speed stage switching device representing a first embodiment according to the present invention.

FIG. 2 is a control circuit diagram of a vehicle speed stage switching device showing a first embodiment according to the present invention.

FIG. 3 is a time chart showing the operation of the control circuit of the vehicle speed stage switching device showing the first embodiment according to the present invention.

FIG. 4 is a time chart showing the operation of the relay 60 in the control circuit of the vehicle speed stage switching device, which represents the first embodiment according to the present invention.

FIG. 5 is a control circuit diagram of a vehicle speed stage switching device showing a second embodiment according to the present invention.

FIG. 6 is a time chart showing the operation of the relay 60 in the control circuit of the vehicle speed stage switching device showing the second embodiment according to the present invention.

[Explanation of symbols]

 1 Battery 2 Main switch 3 Shift up switch 4 Shift down switch 5 Hold switch 6 Forward / backward switch 10 Steering monolever 30-90 Relay 100 1st speed solenoid 110 2nd speed solenoid 120 3rd speed solenoid

Claims (3)

[Claims] 1. A vehicle speed stage switching device for a working vehicle, comprising: a transmission for switching a vehicle speed stage by a plurality of solenoid valves; and a working machine lever for operating a working machine, wherein the working machine lever is installed in a driver's seat. , A steering mono-lever (10) installed on the driver's seat at a position opposite to the working machine lever on the left and right sides to steer the vehicle, and attached to the grip portion of the steering mono-lever (10) to reduce the vehicle speed. Shift switch (3) for shifting from the high speed to the high speed one step, and a shift down switch (4) mounted on the grip portion of the steering monolever (10) for shifting the vehicle speed from the high speed to the low speed by one step. And a forward / reverse switch (6) attached to a grip portion of the steering monolever (10) to switch between forward, neutral and reverse, and the steering monolever (1) 0) Hold switch (5) which is attached to the grip portion and which selects whether or not the predetermined vehicle speed is fixed when the forward / reverse switch (6) is switched at the predetermined vehicle speed. A vehicle speed stage switching device for a working vehicle, which is characterized in that 2. The vehicle speed stage switching device for a work vehicle according to claim 1, wherein the hold switch (5) is selected on the hold side.
When the vehicle speed is the first speed and the forward / reverse switch (6) is switched from forward or reverse, the vehicle speed is fixed at the first speed, and when the non-hold side is selected, the vehicle speed is the first speed and the forward / reverse switch. A vehicle speed stage switching device for a work vehicle, wherein the vehicle speed stage is set to a speed other than the first speed when (6) is switched from forward or reverse. 3. The vehicle speed change device for a work vehicle according to claim 1, wherein the shift-up switch (3) is on the right side of the upper surface of the grip portion of the steering monolever (10), and the steering monolever (10). When the (10) is held from the front with the left hand, it is mounted at a position where it can be easily operated by the thumb of the left hand, and the downshift switch (4) is located on the upper left side of the grip portion of the steering monolever (10). In addition, when the steering monolever (10) is held from the front with the left hand, it is mounted at a position where it can be easily operated by the thumb of the left hand, and the hold switch (5) holds the steering monolever (10). The forward / reverse switch (), which is located on the right side surface of the section and is easily operated by the thumb of the left hand when the steering monolever (10) is held from the front by the left hand. ) Is on the front side of the grip portion of the steering monolever (10), and is located at a position where the steering monolever (10) can be easily operated with the index finger or the middle finger of the left hand when the steering monolever (10) is gripped from the front with the left hand. A vehicle speed stage switching device for a work vehicle, which is mounted.