JP6247573B2 - Hydraulic actuator - Google Patents

Description

  The present invention relates to a hydraulic actuator.

  A hydraulic device such as a tilt device that lifts and lowers a snow removal working part of a snowplow and a trim / tilt device that tilts a ship propulsion device with respect to a ship, a cylinder device that expands and contracts by supply and discharge of hydraulic fluid such as oil, and a cylinder device And a tank for storing the working fluid and a tank for storing the working fluid (see, for example, Patent Document 1).

JP 2003-97504 A

Here, for example, a hydraulic actuator used in a snowplow is disposed between the main body and the movable snow removal working unit. However, when performing snow removal work, the snow removal working unit is frequently raised and lowered relative to the main body. Therefore, the expansion / contraction operation of the cylinder device is frequently repeated. For this reason, the problem that the temperature of hydraulic fluid rises by the heat_generation | fever of the pump which supplies / discharges hydraulic fluid to a cylinder apparatus arises.
This problem of heat generation is not limited to the hydraulic actuators used in the above-mentioned snowplow, and can be applied to other hydraulic actuators as long as the cylinder device is frequently expanded and contracted. Can happen.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a hydraulic actuator capable of suppressing an increase in the temperature of hydraulic fluid used for expansion and contraction of a cylinder device.

The present invention is partitioned into a first chamber and a second chamber by a piston, elongation by hydraulic fluid supplied to said first chamber, and a cylinder device which shrinks by being supplied to the second chamber, before Symbol A main body provided with a pump device for delivering hydraulic fluid, a tank for storing the hydraulic fluid, and a switching device that is provided outside the main body and switches the flow of the hydraulic fluid between the main body and the tank. And between the pump device and the cylinder device, a first chamber side flow path connecting the pump device and the first chamber, and between the pump device and the cylinder device, the pump device and the cylinder device A second chamber side channel connecting the second chamber, wherein the switching device branches from the second chamber side channel, passes through the outside of the main body, and the second chamber side channel. And a second chamber discharge flow path connecting the tank and the tank, and the second chamber discharge flow path, Direction control for opening the second chamber discharge channel when discharging the hydraulic fluid from the second chamber and closing the second chamber discharge channel when supplying the hydraulic fluid from the pump device to the second chamber And when supplying the hydraulic fluid to the second chamber, the hydraulic fluid is supplied from the pump device via the second chamber side flow path, and the hydraulic fluid is discharged from the second chamber. When the hydraulic fluid is discharged to the tank via the second chamber discharge channel, and when the hydraulic fluid is supplied to the first chamber, the hydraulic fluid is discharged via the first chamber side channel. When the hydraulic fluid is supplied from the pump device and discharged from the first chamber, the hydraulic fluid is discharged to the pump device via the first chamber side flow path .
Hydraulic actuator of this invention, the switching device opens only in the second chamber provided on the side channel, the direction of flow of the hydraulic fluid is directed into the second chamber from the pump device check valve May be further provided.
The hydraulic actuator according to the present invention allows the hydraulic fluid to escape from the second chamber to the tank in accordance with the pressure of the second chamber discharge flow path, in parallel with the direction control valve, in the second chamber discharge flow path. A relief valve may be provided.
In the hydraulic actuator according to the present invention, the tank may be a separate body from the main body .
The hydraulic actuator according to the present invention may be disposed between a main body of a snowplow provided with a traveling unit of the snowplow and a snow removal working unit.

  With the hydraulic actuator according to the present invention, it is possible to suppress an increase in the temperature of the hydraulic fluid used for expansion and contraction of the cylinder device.

It is a figure which shows the external appearance of the raising / lowering actuator which concerns on one embodiment of this invention. It is principal part sectional drawing of a cylinder apparatus. It is principal part sectional drawing which shows arrangement | positioning of an electric motor and a pump apparatus. It is a figure which shows the snow remover to which a raising / lowering actuator is attached. It is a figure which shows the hydraulic circuit of a raising / lowering actuator. It is a figure which shows the example of the hydraulic circuit which made the one-way valve a part of main body parts, and provided the direction control valve in the exterior of the main body part.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a view showing an appearance of a lifting actuator 100 (an example of a hydraulic actuator) according to an embodiment of the present invention.

<Schematic configuration of lifting actuator 100>
(Main body 30, external tank 81, switching device 85)
As shown in FIG. 1, the elevating actuator 100 includes a main body portion 30 including a cylinder device 10 that expands and contracts by oil, which is an example of hydraulic fluid, and an external tank 81 (a tank An example), and a switching device 85 that is provided outside the main body 30 and switches the flow of oil between the main body 30 and the external tank 81.
The main body 30 includes a cylinder device 10, a pump device 21 that sends oil to the cylinder device 10, a housing 28 that houses the pump device 21, and a pump device 21 that is disposed above the housing 28 and accommodated in the housing 28. And an internal tank 31 in which oil supplied to the pump device 21 is stored.

(Cylinder device 10)
FIG. 2 is a cross-sectional view of a main part of the cylinder device 10. As shown in FIG. 2, the cylinder device 10 includes a cylinder block 14 having a closed lower portion, an upper end opened and extending in the vertical direction, a cylindrical cylinder 11 fitted in the cylinder block 14, and a cylinder 11, a piston 12 that slides along the axial direction of the cylinder 11, and a piston rod 13 that is displaced integrally with the piston 12 while fixing the piston 12 to one end and advances and retreats in the axial direction of the cylinder 11. And a rod guide 15 that closes the opening at the upper end of the cylinder block 14 while allowing the piston rod 13 to advance and retreat.
The cylinder block 14 is formed integrally with the housing 28 (see FIG. 1).

  The inside of the cylinder 11 is partitioned into a first chamber Y1 and a second chamber Y2 by a piston 12, and when oil is supplied to the first chamber Y1, the piston 12 and the piston rod 13 are lifted in the figure. The cylinder device 10 extends. On the other hand, when the oil is supplied to the second chamber Y2 from the extended state, the piston 12 and the piston rod 13 are lowered in the figure, and the cylinder device 10 is contracted. Here, when the cylinder device 10 extends, oil is discharged from the second chamber Y2, and when the cylinder device 10 contracts, oil is discharged from the first chamber Y1.

Moreover, the 1st connection part 14a connected with the driving | running | working frame 212 (refer FIG. 4) of the below-mentioned snowplow 200 which is the other party to which this raising / lowering actuator 100 is attached is formed in the lower end of the cylinder block 14. As shown in FIG. On the other hand, the upper end of the piston rod 13 is formed with a second connecting portion 13a that is connected to the vehicle body frame 213 of the snowplow 200 to which the lift actuator 100 is attached. The distance between the traveling frame 212 and the vehicle body frame 213 is changed by the expansion and contraction of the cylinder device 10.
Further, the cylinder block 14 is provided with an internal tank 31 for storing oil. A return flow path 76 that returns oil from the external tank 81 to the internal tank 31 is connected to the internal tank 31. In addition, although the flow path which returns oil to the pump chamber 24 mentioned later is connected to the internal tank 31, the illustration is abbreviate | omitted in FIG.

(Pump device 21, electric motor 40)
FIG. 3 is a cross-sectional view of the main part showing the arrangement of the electric motor 40 and the pump device 21.
As shown in FIG. 3, the pump device 21 is fixed to the bottom of a pump chamber 24 formed inside the housing 28.
The pump device 21 includes a pump body 25 and a switching valve 51 shown in FIG. The pump body 25 and the switching valve 51 may be integral with each other as the pump device 21 or may be separate.

The electric motor 40 includes a harness 42 (see FIG. 1) that receives power from the outside, and rotates the output shaft 41 by the power supplied through the harness 42. The electric motor 40 is mounted and fixed on the upper portion of the housing 28 so as to close the opening of the upper portion of the pump chamber 24 with the output shaft 41 connected to the pump device 21 of the pump chamber 24.
In the electric motor 40, the rotation direction of the output shaft 41 is switched between forward rotation and reverse rotation according to the direction of the supplied current. Therefore, the rotation direction of the pump device 21 to which the output shaft 41 is connected is also switched to forward rotation or reverse rotation according to the rotation direction of the output shaft 41.
The pump chamber 24 is filled with oil by flowing oil from the internal tank 31 described above through a flow path (not shown).

(External tank 81)
As shown in FIG. 1, the external tank 81 has mounting portions 81 a and 81 b that are fixed to the snow removal machine 200 (see FIG. 4). The external tank 81 in this embodiment has a larger capacity than the internal tank 31.
In the present invention, the external tank 81 may be an oil cooler such as an air cooling type or a water cooling type.

(Switching device 85)
As shown in FIG. 1, the switching device 85 is connected to the main body 30 by two flow paths 77 and 78 through which oil flows, and is connected to an external tank 81 by one flow path 79 through which oil flows.
When the oil is supplied to the second chamber Y2 of the cylinder device 10, the switching device 85 supplies the oil from the pump body 25 through the switching valve 51 (see FIG. 5), and when the oil is discharged from the second chamber Y2, the switching device 85 The oil flow is switched so as to be discharged directly to the external tank 81 without passing through the device 21 (switching valve 51). The switching of the oil flow by the switching device 85 is performed in conjunction with an operation input to an auger housing operation lever 250 (hereinafter referred to as an operation lever 250) of the snowplow 200 described later.
A hydraulic circuit for controlling the oil flow and pressure of the lifting actuator 100 including the switching device 85 will be described later.

<Snowplow 200 to which the lifting actuator 100 is attached>
FIG. 4 is a view showing a snow removal machine 200 as an example of a machine or the like to which the lifting / lowering actuator 100 is attached.
The snowplow 200 shown in FIG. 4 has a traveling frame 212 and a vehicle body frame 213 that constitute the body 211. The vehicle body frame 213 is attached to the front portion of the traveling frame 212 that constitutes the main body of the airframe 211, and is attached to the traveling frame 212 so as to be rotatable within the illustrated surface.

  The traveling frame 212 includes a traveling unit 221 that is driven by an engine (not shown), and the vehicle body 211 moves forward in the drawing to the left or backward in the drawing by the traveling unit 221. The traveling frame 212 includes an operation handle 260 extending rearward and upward. A grip 261 for the user to grip with the hand is provided at the tip of the operation handle 260.

In addition, an operation lever 250 for inputting an instruction to raise and lower a snow removal work unit 230 described later is provided near the grip 261. When the operation lever 250 is tilted forward (leftward in the figure), power is supplied from the battery to the electric motor 40 through the harness 42 so as to rotate the electric motor 40 in the forward direction. Thereby, the raising / lowering actuator 100 is extended, and the auger housing 231 is raised.
On the other hand, when the operation lever 250 is tilted backward (rightward in the drawing), power is supplied from the battery to the electric motor 40 through the harness 42 so as to reversely rotate the electric motor 40. Thereby, the raising / lowering actuator 100 contracts, and the auger housing 231 which has been raised is lowered.

A snow removal working unit 230 is provided at the front of the body frame 213. The snow removal working unit 230 houses an auger 232 that collects snow in an auger housing 231. The body frame 213 is mounted with a generator, a battery, and an electrical system to which the harness 42 of the lifting actuator 100 is connected, but illustration and description thereof are omitted.
Between the body frame 213 and the traveling frame 212 of the snowplow 200, the main body 30 of the lifting actuator 100 of the above-described embodiment is disposed. Specifically, the first connecting portion 14 a of the cylinder device 10 is connected to the traveling frame 212, and the second connecting portion 13 a is connected to the vehicle body frame 213.

Then, when the cylinder device 10 of the elevating actuator 100 expands and contracts, the body frame 213 is rotated with respect to the traveling frame 212 and the snow removal working unit 230 is raised and lowered.
On the other hand, the external tank 81 is fixed at a position higher than the main body portion 30 in the snow removal machine 200 by the attachment portions 81a and 81b. Thereby, the oil stored inside the external tank 81 can be returned to the internal tank 31 through the return flow path 76 by its own weight.
The part where the external tank 81 is fixed is a place exposed to the external environment and subject to snowfall. The switching device 85 is attached near the external tank 81.

<Hydraulic circuit of the lifting actuator 100>
(Hydraulic circuit of main body 30)
FIG. 5 is a diagram illustrating a hydraulic circuit of the lifting actuator 100.
Between the pump body 25 and the cylinder device 10, a first chamber side flow channel 71 communicating with the first chamber Y1 and a second chamber side flow channel 72 communicating with the second chamber Y2 are formed. The switching valve 51 is disposed in the first chamber side flow channel 71 and the second chamber side flow channel 72 so as to straddle the first chamber side flow channel 71 and the second chamber side flow channel 72. .

The switching valve 51 switches the direction of oil flow to the first chamber Y1 or the second chamber Y2 according to the rotation direction of the pump body 25. The switching valve 51 includes a spool 53 that slides in the valve chamber 52 and a first check valve 54 that is provided on the first chamber-side flow path 71 on each end portion side in the sliding direction of the spool 53. And a second check valve 55 provided on the second chamber side flow path 72.
The valve chamber 52 is partitioned by a spool 53 into a first oil chamber 52 a adjacent to the first check valve 54 and a second oil chamber 52 b adjacent to the second check valve 55. The first oil chamber 52a is connected to the pump body 25 through the first chamber-side flow channel 71, and is connected to the first chamber Y1 through the first check valve. The second oil chamber 52 b is connected to the pump body 25 through the second chamber-side flow path 72, and is connected to the second chamber Y <b> 2 through the second check valve 55.

Of the first chamber side channel 71, the channel from the pump body 25 to the switching valve 51 is referred to as a pump side first chamber side channel 71B, and the channel from the switching valve 51 to the first chamber Y1 of the cylinder device 10. Is referred to as a cylinder side first chamber side flow path 71A. Similarly, in the second chamber side flow path 72, the flow path from the pump body 25 to the switching valve 51 is referred to as a pump side second chamber side flow path 72B, and from the switching valve 51 to the second chamber Y2 of the cylinder device 10. This flow path is referred to as a cylinder side second chamber side flow path 72A (second chamber supply flow path).
The pump side first chamber side flow path 71B and the pump side second chamber side flow path 72B are provided with check valves 65 and 66 that are normally closed and open when oil is sucked from the internal tank 31, respectively.

The spool 53 is normally closed and opens when the pressure of the pump-side first chamber-side channel 71B becomes equal to or higher than a preset pressure, and the first oil chamber 52a (pump-side first chamber-side channel 71B) is opened. ) Is released to the second oil chamber 52b.
When the oil is supplied to the first chamber Y1 (when the cylinder device 10 is extended), the cylinder-side first chamber-side flow passage 71A is allowed to flow without reducing the flow passage area and is switched from the first chamber Y1. When returning the oil to 51, a control valve 64 is provided that reduces the flow area and reduces the contraction speed of the cylinder device 10. As shown in FIG. 5, the control valve 64 is constituted by a combination of a check valve 64a and an orifice 64b.

The cylinder-side first chamber-side flow path 71A is normally closed, and the pressure of the cylinder-side first chamber-side flow path 71A is a preset pressure (a pressure higher than the pressure at which the up blow valve 61 is opened). ) A relief valve 63 that opens when the above is reached and releases the oil in the cylinder side first chamber side flow path 71A to the internal tank 31 is connected.
On the other hand, the cylinder-side second chamber-side flow path 72A is normally closed and opens when the pressure of the cylinder-side second chamber-side flow path 72A becomes equal to or higher than a preset pressure, and the cylinder-side second chamber side A down blow valve 62 for allowing the oil in the flow path 72A to escape to the internal tank 31 is connected.
The switching valve 51 including the up blow valve 61 is configured integrally with the pump body 25. However, the down blow valve 62, the relief valve 63, and the check valves 65 and 66 may be integrated with the pump body 25. Alternatively, the housing 28 may be provided.

(Hydraulic circuit of switching device 85)
A switching device 85 is connected to the cylinder side second chamber side flow path 72A. The two flow paths 77 and 78 that connect the main body 30 and the switching device 85 constitute a part of the cylinder-side second chamber-side flow path 72A as shown in FIG.
The switching device 85 includes a one-way valve 82 (a check valve), a direction control valve 83, and a second chamber discharge flow path relief valve 84. The one-way valve 82 is provided on the cylinder-side second chamber side flow path 72A, and the oil opens in the direction from the switching valve 51 toward the second chamber Y2 of the cylinder device 10, and the oil is switched from the second chamber Y2. Close in the direction toward 51.

In the switching device 85, the second chamber discharge flow connected to the flow path 79 leading to the external tank 81 from the portion between the one-way valve 82 and the second chamber Y2 in the cylinder-side second chamber-side flow path 72A. A path 73 is provided. The direction control valve 83 is provided on the second chamber discharge flow path 73 and corresponds to an operation input to the operation lever 250 of the snowplow 200, that is, corresponds to switching of the rotation direction of the electric motor 40. Then, the opening and closing of the second chamber discharge channel 73 is switched.
Specifically, when the operation lever 250 is tilted forward and the electric motor 40 is rotated forward, oil is sent from the pump body 25 to the first chamber-side flow path 71 and the direction control valve 83 is opened. On the other hand, when the operation lever 250 is tilted backward to rotate the electric motor 40 in the reverse direction, oil is sent from the pump body 25 to the second chamber side flow path 72 and the direction control valve 83 is closed.
The second chamber discharge flow path relief valve 84 is provided in the second chamber discharge flow path 73 in parallel with the direction control valve 83, and flows from the second chamber Y2 in accordance with the pressure of the second chamber discharge flow path 73. Oil is released to the external tank 81 through the path 79.

(Hydraulic circuit operation)
Next, the operation of the hydraulic circuit of the lifting actuator 100 will be described. When the operation lever 250 is tilted forward and the electric motor 40 is rotated forward, the pump body 25 is rotated forward, and the oil is sent to the pump-side first chamber-side flow path 71B. At this time, the direction control valve 83 is open.
The oil sent to the pump side first chamber side flow path 71B flows into the first oil chamber 52a. The oil in the first oil chamber 52a pushes the spool 53 toward the second oil chamber 52b and opens the first check valve 54 adjacent to the first oil chamber 52a. As a result, the pump-side first chamber-side flow path 71B and the cylinder-side first chamber-side flow path 71A communicate with each other, and the oil in the first oil chamber 52a passes through the cylinder-side first chamber-side flow path 71A. To the first chamber Y1.

At this time, the oil in the second chamber Y2 is discharged to the cylinder-side second chamber-side flow path 72A and reaches the switching device 85 through the flow path 77 that is outside the main body 30. Since the one-way valve 82 of the switching device 85 is closed, the oil flows into the second chamber discharge flow path 73 opened by the direction control valve 83 and is discharged to the external tank 81 through the flow path 79. At this time, if the direction control valve 83 remains closed, the second chamber discharge flow path relief valve 84 is opened, and the oil in the second chamber discharge flow path 73 is released to the external tank 81.
Since the external tank 81 is disposed at a position higher than the main body 30 as shown in FIG. 4, the oil discharged to the external tank 81 passes through the return channel 76 (see FIG. 1) due to its own weight. Returned to the internal tank 31 of the section 30.
When the oil is supplied to the first chamber Y1 and the oil is discharged from the second chamber Y2, the cylinder device 10 extends and the snow removal working unit 230 rises.

On the other hand, when the operation lever 250 is tilted backward and the electric motor 40 is rotated in the reverse direction, the pump body 25 is rotated in the reverse direction, and the oil is sent to the pump-side second chamber side flow path 72B. At this time, the direction control valve 83 is closed.
The oil sent to the pump side second chamber side flow path 72B flows into the second oil chamber 52b. The oil in the second oil chamber 52b pushes the spool 53 toward the first oil chamber 52a and opens the second check valve 55 adjacent to the second oil chamber 52b. At this time, the spool 53 pushed toward the first oil chamber 52a pushes and opens the first check valve 54, whereby the pump side first chamber side flow channel 71B and the cylinder side first chamber side flow channel 71A. Leads to.

Further, since the second check valve 55 is opened, the pump-side second chamber-side flow path 72B and the cylinder-side second chamber-side flow path 72A communicate with each other, and the oil in the second oil chamber 52b is supplied to the cylinder-side second. It flows into the chamber-side flow path 72A, reaches the one-way valve 82 through the flow path 78 that is outside the main body 30, and opens the one-way valve 82. Here, since the second chamber discharge flow path 73 is closed by the direction control valve 83, the oil that has passed through the one-way valve 82 returns to the main body 30 through the flow path 77 and is supplied to the second chamber Y2. The
At this time, the oil in the first chamber Y1 is discharged to the cylinder-side first chamber-side flow path 71A, passes through the orifice 64b on the cylinder-side first chamber-side flow path 71A, and the first oil chamber 52a of the switching valve 51. Reaches the pump body 25 through the pump-side first chamber-side channel 71B.
When the oil is supplied to the second chamber Y2 and the oil is discharged from the first chamber Y1, the cylinder device 10 is contracted and the snow removal working unit 230 is lowered.

<Effect of lifting actuator 100>
According to the lifting / lowering actuator 100 configured as described above, when oil is supplied to the second chamber Y2, it is supplied from the pump body 25 through the switching valve 51 to the second chamber Y2. On the other hand, when the oil is discharged from the second chamber Y2, the oil discharged from the second chamber Y2 to the cylinder side second chamber side flow path 72A passes through the second chamber discharge flow path 73 that does not pass through the switching valve 51. It is discharged directly to the external tank 81.
That is, in the lift actuator 100, the oil discharged from the second chamber Y2 is changed from the second chamber Y2 to the switch valve 51 (pump) as compared with the conventional hydraulic actuator returned to the pump body 25 through the switch valve 51. It is not exposed to the heat of the device 21). Thereby, the temperature rise of the oil which distribute | circulates a hydraulic circuit can be suppressed. Therefore, the elevating actuator 100 can suppress an increase in the temperature of oil in the hydraulic circuit without increasing the capacity of the internal tank 31 of the main body 30 or using a dedicated cooling device.

In the lift actuator 100 of the present embodiment, since the flow path until the oil discharged from the second chamber Y2 returns to the pump body 25 is formed longer than that of the conventional hydraulic actuator, the oil and the external medium ( The opportunity for heat exchange with air, etc.) is increased, which can lower the temperature of the oil.
By lowering the temperature of the oil, an increase in the temperature of the pump immersed in the oil can be suppressed.

Further, since the lifting / lowering actuator 100 of this embodiment always acts in the direction in which the weight of the snow removal working unit 230 contracts the cylinder device 10, the oil discharged from the first chamber Y <b> 1 when the cylinder device 10 contracts. The pressure of the oil discharged from the second chamber Y2 when the cylinder device 10 extends is lower than the pressure.
In general, when a flow path for flowing oil discharged from the cylinder device 10 is provided outside the main body portion 30, the oil leakage countermeasure (pressure resistance), the rigidity of the flow path, etc., as the pressure acting on the flow path decreases. The cost for setting can be reduced.
In the lifting actuator 100 according to the present embodiment, the oil discharge flow path provided outside the main body 30 is discharged from the second chamber Y2 having a lower pressure than the oil flow path discharged from the first chamber Y1. The oil flow path (flow path 77, second chamber discharge flow path 73) makes it possible to relatively reduce costs required for setting oil leakage countermeasures, flow path rigidity, and the like.

  Further, in the lifting actuator 100 according to the present embodiment, since the external tank 81 is formed separately from the main body 30, the degree of freedom of the installation position of the external tank 81 is increased regardless of the installation position of the main body 30. high. Therefore, the external tank 81 can be installed in a place that is advantageous for cooling the internal oil, and is exposed to an external environment that can be in direct contact with snow, like the external tank 81 in the present embodiment. It is possible to cool the internal oil effectively by installing it at the place where it was installed. Also in this point of view, the lifting actuator 100 of the present embodiment is highly suitable when used in the snowplow 200.

  Further, the lifting actuator 100 of the present embodiment is a part of the cylinder side second chamber side flow path 72A (flow paths 77 and 78) through which oil passes in the direction in which the oil is supplied from the pump device 21 to the second chamber Y2. However, since it is provided outside the main body 30, the oil can be cooled even when the oil is supplied to the second chamber Y2.

  The lift actuator 100 of the present embodiment is used as a hydraulic actuator that lifts and lowers the snow removal work unit 230 of the snow removal machine 200. However, the snow removal machine 200 generally moves up and down the snow removal work unit 230 in general. The oil temperature of the hydraulic actuator is likely to rise. Since the raising / lowering actuator 100 of this Embodiment has suppressed the raise of the temperature of oil as mentioned above, the suitability when used for the snow remover 200 where the temperature of oil tends to rise is high.

<Modification 1>
The elevating actuator 100 of the present embodiment includes the internal tank 31 in the main body 30, but the present invention may not include the internal tank 31. In this case, the external tank 81 or the like connected to the internal tank 31 may be configured to be connected to the pump chamber 24 instead of being connected to the internal tank 31. According to the lifting actuator 100 in which the main body 30 does not include the internal tank 31, the main body 30 can be reduced in size.

<Modification 2>
When the lifting actuator 100 according to the present embodiment is configured not to include the internal tank 31, the external tank 81 may be configured integrally with the main body 30. Even in the case of Modification 2 in which the internal tank 31 is replaced with the external tank 81 in the lifting actuator 100 of the above-described embodiment, the oil discharged from the second chamber Y2 to the cylinder-side second chamber-side flow path 72A is The switching device 85 is discharged to the external tank 81 without passing through the switching valve 51.
Therefore, unlike the conventional hydraulic actuator in which the internal tank is simply replaced with the external tank, the effect of the present invention of suppressing the temperature rise of the oil in the hydraulic circuit can be exhibited. In addition, when the structure which replaces the internal tank 31 integral with the main body 30 with the external tank 81 is adopted, the external tank 81 is made to be the same size as the internal tank 31 so that the main body 30 does not become large. Is preferred.

<Modification 3>
In the lifting / lowering actuator 100 of the present embodiment, the switching device 85 may be integrated with the external tank 81 or may be integrated with the main body 30.

<Modification 4>
Moreover, the raising / lowering actuator 100 of this Embodiment is good also as a structure in which the switching apparatus 85 does not form the one-way valve 82, the direction control valve 83, and the 2nd chamber discharge flow path relief valve 84 integrally.
FIG. 6 is a diagram showing a hydraulic circuit in which the one-way valve 82 is integrated with the main body 30 and the direction control valve 83 and the second chamber discharge flow path relief valve 84 are provided outside the main body 30. As shown in FIG. 6, even in the elevating actuator 100 of the embodiment in which the one-way valve 82 of the switching device 85 is configured separately from the direction control valve 83 and the second chamber discharge flow path relief valve 84, the hydraulic circuit The effect of the present invention of suppressing the temperature rise of the oil can be exhibited.

<Modification 5>
The lifting actuator 100 of the present embodiment may be configured such that the switching device 85 does not include the second chamber discharge flow path relief valve 84.

<Modification 6>
Further, the lifting actuator 100 of the present embodiment is not limited to the configuration in which the switching device 85 is a combination of the one-way valve 82 and the direction control valve 83, and when supplying oil to the second chamber Y2, the pump device 21 (pump main body 25 and switching valve 51) is supplied, and oil is discharged from the second chamber Y2 directly to the external tank 81 without passing through the pump device 21 (pump main body 25 and switching valve 51). As long as the function of switching the flow of oil is exhibited, it is sufficient.

<Modification 7>
The lifting actuator 100 of the present embodiment is a hydraulic actuator used for lifting, but the hydraulic actuator of the present invention is not limited to lifting, and a tilting actuator that tilts the snow removal working part of the snowplow left and right. And various other hydraulic actuators.

DESCRIPTION OF SYMBOLS 10 ... Cylinder apparatus, 12 ... Piston, 21 ... Pump apparatus, 25 ... Pump main body, 51 ... Switching valve, 81 ... External tank (tank), 85 ... Switching apparatus, 100 ... Elevating actuator (hydraulic actuator), Y1 ... No. 1 room, Y2 ... 2nd room

Claims (5)

Partitioned into a first chamber and a second chamber by a piston, elongation by hydraulic fluid supplied to said first chamber, said cylinder shrinks by being supplied to the second chamber apparatus, the pre-Symbol hydraulic fluid delivered A pump device , and a main body unit,
A tank for storing the hydraulic fluid;
A switching device that is provided outside the main body, and switches the flow of the working fluid between the main body and the tank ;
A first chamber-side flow path connecting the pump device and the first chamber between the pump device and the cylinder device;
A second chamber-side flow path connecting the pump device and the second chamber between the pump device and the cylinder device;
The switching device branches from the second chamber side flow path, passes through the outside of the main body, and connects the second chamber side flow path and the tank, and the second chamber. When the hydraulic fluid is provided from the second chamber, the second chamber is opened, and the second chamber is opened when the hydraulic fluid is supplied from the pump device to the second chamber. A directional control valve for closing the discharge flow path,
When the hydraulic fluid is supplied to the second chamber, the hydraulic fluid is supplied from the pump device via the second chamber side flow path, and when the hydraulic fluid is discharged from the second chamber, the second chamber is supplied. The hydraulic fluid is discharged into the tank via a chamber discharge flow path;
When the hydraulic fluid is supplied to the first chamber, the hydraulic fluid is supplied from the pump device via the first chamber side flow path, and when the hydraulic fluid is discharged from the first chamber, the first chamber is supplied. A hydraulic actuator that discharges the hydraulic fluid to the pump device via a chamber-side flow path . Wherein the switching device, the provided second chamber side flow passage, the described flow of hydraulic fluid from said pump apparatus in claim 1, further comprising a check valve that opens only in the direction facing the second chamber Hydraulic actuator. Wherein the second chamber discharge passage, the parallel to the direction control valve, according to claim comprising a relief valve for releasing the hydraulic fluid to the tank from the second chamber in response to pressure in the second chamber discharge channel 1 Or the hydraulic actuator of 2. Hydraulic actuator according to any one of claims 1-3 wherein the tank is a separate body from the main body portion. The hydraulic actuator according to any one of claims 1 to 4 , wherein the hydraulic actuator is disposed between a main body portion of a snowplow provided with a traveling unit of the snowplow and a snow removal working unit.

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