JP2572576B2 - Stroke end control device for lift cylinder in bulldozer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a stroke end control device for a lift cylinder in a bulldozer.

[Conventional technology and its problems]

In a bulldozer, when the blade in a tilted state is moved up and down, the left or right lift cylinder reaches the stroke end first depending on the tilt direction. For this reason, the cylinder on the side that has not reached the stroke end further attempts to expand and contract, so that the blade, the radiator guard, and the like connected to the cylinder are twisted.

For this reason, conventionally, a piston valve is provided in the lift cylinder, and the piston valve is operated near the stroke end to reduce the differential pressure between the bottom side and the piston rod side inside the lift cylinder, thereby reducing the thrust of the cylinder. , To reduce torsion. However, since the blade is held by the differential pressure inside the lift cylinder, this differential pressure cannot be extremely reduced by the piston valve. Therefore, there is a problem that the twist at the stroke end cannot be reduced to a certain extent. Further, since the piston valve is provided in the lift cylinder, there is a disadvantage that the structure of the cylinder is complicated. Furthermore, since the speed is determined by the expansion / contraction speed of the blade raising / lowering cylinder and the discharge amount of the hydraulic pump, the blade rotation speed is increased near the blade maximum raising position due to the rotation link ratio of the cylinder, and the shock at the stroke end is increased. There was also.

Therefore, the present invention provides a lift cylinder stroke end control device for a bulldozer that eliminates cylinder thrust when the lift cylinder reaches the stroke end and does not generate an impact at the time of stoppage due to pressure oil flow correction near the stroke end. The purpose is to provide.

[Means for solving the problem]

The present invention provides a detecting means for detecting that a blade in a tilted state is near the limit of an elevating range, and a pair of lift cylinders for elevating the blade when detecting that the blade is near the limit of an elevating range. Control means for gradually decreasing the flow rate of the pressure oil being fed to the pump.

[Action]

According to the present invention, when the blade in the tilted state is near the limit of the elevating range, the lift cylinder gradually stops near the stroke end in order to gradually decrease the flow rate of the pressure oil being fed to the lift cylinder.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of a stroke end control device for a lift cylinder according to the present invention. The lift cylinder 1 and the lift cylinder 2 in this embodiment are respectively mounted on the left and right sides of a radiator guard 3 of a bulldozer as shown in FIG. 2, and each of the piston rods 4 and 5 of these cylinders 1 and 2 The tip is connected to the back of the blade 6. In each of the lift cylinders 1 and 2, the oil chambers on the bottom side are connected to each other via an oil passage 7 and the oil chambers on the piston rod side are connected to each other via an oil passage 8, so that the same It expands and contracts at the stroke speed. When the blade 6 is tilted and tilted as shown in FIG. 2, when the blade 6 is raised, the lift cylinder 2 reaches the stroke end first, and when the blade 6 is lowered, the lift cylinder 1 moves first. Reaches the stroke end.

Now, when the operating section 9 is operated to instruct a rising speed of the blade 6, for example, a command signal indicating the rising speed of the blade 6 is applied to the operating valve controller 10 from the operating section 9. When the command signal is input, the operation valve controller 10 sends pressure oil to the oil passage 8 at a flow rate corresponding to the commanded rising speed. Accordingly, each of the lift cylinders 1 and 2 is shortened at a stroke speed corresponding to the flow rate of the pressure oil fed, and as a result, the blade 6 is raised at the commanded rising speed.

At this time, the flow rate correction controller 11 performs the control shown in the flowchart of FIG. First, the stroke sensor 12 and the stroke sensor 13 (for example, magnescale) detect the stroke lengths SL and SR of the lift cylinders 1 and 2, respectively, and output signals indicating the stroke lengths SL and SR to the flow rate correction controller. Add to 11. When these signals are input (step 101), the flow rate correction controller 11 obtains the distances LL and LR to the stroke end on the bottom side of each of the lift cylinders 1 and 2 based on the stroke lengths SL and SR, A change in the stroke length SL is differentiated with respect to time to obtain a stroke speed V (SL).

Next, the flow rate correction controller 11 compares the obtained distances LL and LR to determine which is shorter (step 10).
3) If the distance LL is shorter, LL = L (step 10).
4) If the distance LR is shorter, LR = L is set (step 105). Here, for example, the distance LR is shorter and LR = L.
L, the distance L is compared with a predetermined distance ΔL from the stroke end, and the lift cylinder 2
It is determined whether or not the piston has reached the vicinity of the stroke end (step 106). If the piston of the lift cylinder 2 has not reached the distance ΔL, the processing from step 101 is repeated, and if the piston has reached the distance ΔL, the flow rate correction value M = f (L, V) of the pressure oil is obtained (step 107). As shown in the graph of FIG. 3, the flow rate correction value M determines the flow rate of the pressure oil corresponding to the stroke speed V by the distance ΔL.
Shows that the distance gradually decreases with the distance L from the time point. When obtaining the flow rate correction value M, the flow rate correction controller 11 adds a modulated signal indicating the flow rate correction value M to the operation valve controller 10. When the modulating signal is input, the operating valve controller 10 sends pressure oil of a flow rate corresponding to the modulating signal to the oil passage 8 instead of the command signal from the operating section 9. Therefore, each of the lift cylinders 1 and 2 is gradually reduced from the stroke speed V.

Further, the flow rate correction controller 11 compares the distance L with a preset distance ΔL ′ (∠ΔL) from the stroke end to determine whether the piston of the lift cylinder 2 has reached just before the stroke end ( Step 10
8). Then, the piston of the lift cylinder 2 has a distance Δ
If the distance has not reached L ', the processing from step 101 is repeated, and if the distance has reached the distance ΔL', it is determined that the pressure oil supply is stopped (step 109). When the flow rate correction controller 11 determines to stop the pressure oil pumping, it adds a signal indicating this determination to the operation valve controller 10. When this signal is input, the operation valve controller 10 stops the pressure oil supply to the oil passage 8 as shown in the graph of FIG. Therefore, each of the lift cylinders 1 and 2 stops when the piston of the lift cylinder 2 reaches the distance ΔL ′.

When the piston of the lift cylinder 2 reaches the distance ΔL when the blade 6 is lifted in this way, the flow rate of the pressurized oil fed to the lift cylinders 1 and 2 is reduced.
Is gradually decreased with the distance L, and when the piston of the lift cylinder 2 reaches the distance ΔL ′, the pressure oil supply to the lift cylinders 1 and 2 is stopped. Therefore, each of the lift cylinders 1 and 2 is decelerated and stopped as the piston of the lift cylinder 2 approaches the stroke end, so that no impact is generated, and there is no cylinder thrust at the stroke end. Note that depending on the tilt state,
When the blade 6 is raised, the lift cylinder 1 reaches the stroke end. Even in such a case, the flow rate correction of the pressure oil is performed according to the flowchart of FIG.

FIG. 5 is a block diagram showing another embodiment of the stroke end control device according to the present invention. In this embodiment, the stroke sensors 12 and 13 in the apparatus shown in FIG.
Instead, a rotation angle sensor 41 and a rotation angle sensor 42 for detecting the rotation angle of an I frame (not shown) supporting the blade 6 are provided. These rotation angle sensors 41
Reference numerals 42 are respectively attached to the shafts that support the C frame on the left and right sides of the vehicle body, and detect the respective rotation angles on the left and right sides of the C frame.

Now, for example, when the blade 6 is raised with the blade 6 tilted as shown in FIG. 1, the flow rate correction controller 11 performs the control shown in the flowchart of FIG. First, the flow rate correction controller 11
It is determined that the blade 6 has been raised based on the input of the detection outputs of steps (a) and (b) (step 201). Next, the flow rate correction controller 11
Based on the rotation angles on the left and right sides of the C frame detected by the rotation angle sensors 41 and 42, the center of the blade 6 as shown in FIG. Lift amount ι and tilt amount t in the ascending direction
(Step 202). Then, the flow rate correction controller 11 obtains the lift range ιmax specified according to the tilt amount t, and obtains the lift possibility ι ′ in the upward direction by subtracting the lift amount ι in the upward direction from the lift range ιmax (step 203). Note that the liftable amount ι ′ varies with the tilt amount t as shown in the graph of FIG. Further, the flow rate correction controller 11 compares the lift amount ι in the ascending direction with the lift amount ι ′ (step 20).
4) If ι <ι ′, the processing from step 201 is repeated, and if ι ≧ ι ′, the flow rate correction of the pressure oil which decreases in accordance with the lift amount ι as shown by the cliff in FIG. 7 Value Q
And a modulation signal indicating the correction value Q is added to the operation valve controller 10. When the modulating signal is input, the operating valve controller 10 obtains the product of the correction value Q and the flow rate of the pressure oil indicated by the command signal from the operating section 9, and the product is indicated by the product decreasing in accordance with the lift amount. A flow of pressurized oil is pumped into the oil passage 8. Therefore, each cylinder 1,
In the case of 2, the stroke speed is gradually reduced as the blade 6 rises and stops. Similarly, when lowering the blade 6, the lift amount ι in the descending direction and the liftable amount ι ′ in the descending direction are obtained, and if ι ≧ ι ′, the pressure of the flow rate decreasing corresponding to the lift amount ι is determined. By pumping the oil to the oil passage 7, each of the lift cylinders 1 and 2 is gradually stopped. Therefore, even if one of the lift cylinders 1 and 2 reaches the stroke end, no impact occurs and no twisting occurs. In this embodiment, the left and right rotation angles of the I frame are respectively detected. However, the present invention is not limited to this, and tilt angle sensors are attached to the left and right sides of the I frame, respectively. The posture of the I frame may be detected, and the lift amount and the tilt amount of the blade may be obtained based on the detected posture.

〔The invention's effect〕

As described above, according to the present invention, if the blade in the tilted state is near the limit of the elevating range, the lift cylinder gradually stops near the stroke end. Thus, it is possible to provide a stroke end control device for a lift cylinder in a bulldozer, which does not cause the radiator guard or the like to be twisted. Further, since there is no need to provide a piston valve in the lift cylinder, the cylinder can be of a simple structure.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the apparatus according to the present invention, FIG. 2 is a diagram showing an outline of a bulldozer, and FIG.
FIG. 4 is a flowchart showing a control process of a flow rate correction controller in the embodiment shown in FIG. 4, FIG. 4 is a graph showing a flow rate characteristic of pressurized oil fed to a lift cylinder in the embodiment shown in FIG. 1, and FIG. FIG. 6 is a block diagram showing another embodiment of the apparatus according to the present invention, FIG. 6 is a flowchart showing a control process of the flow rate correction controller in the embodiment shown in FIG. 5, and FIG. 7 is a blade in the bulldozer shown in FIG. FIG. 8 is a graph showing the characteristics of the pressure oil flow rate correction value in the embodiment shown in FIG. 1,2 ... lift cylinder, 3 ... radiator card, 4,5 ...
... piston rod, 6 ... blade, 7, 8 ... oil passage, 9
…… Operating unit, 10 ………………………………………………………………………………………………………………… 11,11
... Rotation angle sensor.

Claims (2)

(57) [Claims] 1. A first determination for determining which of a pair of lift cylinders reaches a stroke end first before a blade is lifted and before the pair of lift cylinders reaches near a stroke end. Means for determining that the tilted blade is near the limit of the ascending / descending range by determining that the lift cylinder determined to reach the stroke end earlier by the first determination means has entered the vicinity of the stroke end. A second determining means for determining, and when the second determining means determines that the blade is near the limit of the ascending and descending range, the pressure being fed to a pair of lift cylinders for ascending and descending the blade Control means for gradually reducing the flow rate of oil; and a straw for a lift cylinder in a bulldozer. End controller. Detecting means for detecting a lift amount and a tilt amount of the blade; determining a lift range of the blade based on the detected tilt amount; and determining the lift range and the detected lift amount based on the determined lift range and the detected lift amount. Determining means for determining the liftable amount based on the liftable amount based on the determined liftable amount, and determining that the blade is near the limit of the lifting range by the determining means; Control means for gradually decreasing the flow rate of pressurized oil being pumped to a pair of lift cylinders for raising and lowering the blades. apparatus.