JPS61191429A - Hydraulic control device of hydraulic drive vehicle - Google Patents

Abstract

PURPOSE:To reduce the size of a hydraulic control apparatus of a hydraulically driven vehicle to thereby facilitate mounting the apparatus on the vehicle by using a fixed displacement type hydraulic pump to be connected to a transmission and connecting an auxiliary pump to a driving engine, whereby a hydraulic motor form running is supplied with pressurized oil from both the pumps. CONSTITUTION:A vehicle has rear wheels 1a and 1b driven by an engine 2 for driving the vehicle through a transmission 3 and has front wheels 4a and 4b driven by hydraulic motors 5a and 5b, respectively, connected to the front wheel axles. A hydraulic pump 6 for supplying pressurized oil to the hydraulic motors 5a and 5b is of the fixed displacement type and is driven by the engine 2 through the transmission 3. An auxiliary pump 6b is connected to the line between the hydraulic pump 6 and the hydraulic motors 5a and 5b. The auxiliary pump 6b is driven for rotation in synchronism with the engine 2, supplying a given pressurized oil to the hydraulic motors 5a and 5b.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic control device for a hydraulically driven vehicle, and particularly to a hydraulic control device for controlling two front wheels or rear wheels of a four-wheel drive vehicle, or a hydraulic control device for a two-wheel drive vehicle. The present invention relates to a hydraulic control device for a hydraulically driven vehicle that is most suitable for use in a vehicle configured to hydraulically drive two wheels.

[Conventional technology]

For example, as a hydraulic control system for a hydraulically driven vehicle, the rear wheels are driven by a driving engine and only the front wheels are hydraulically driven.
Conventionally, a device as shown in Fig. 7 has been proposed.

That is, according to this conventional proposal, the rear wheels 1α, Ib are formed to be driven by the driving engine 2 of the vehicle via the transmission 3, and the front wheels 4α
, 4b are hydraulic motors 5α, 5 connected to the front wheel axle.
b is configured to be driven by supply of pressure oil from the hydraulic pump 6 to b. And the hydraulic pump 6
is connected to and supplied to the driving engine 2 of the vehicle, and is formed so as to obtain a desired front wheel drive state.

[Problem that the invention seeks to solve]

However, in the above conventional proposal, the front wheel 4α
, 45 needs to be controlled so as to be synchronized with the rotation speed of the rear wheels 1a, 1h, but by rotating the rear wheels 1a, 1"b, the rotation speed of the car drive engine 2 is controlled to be synchronized with the rotation speed of the rear wheels 1a, 1"b.
The rotation speed of the hydraulic pump 6 that rotates the front @ 4al 4b is synchronized with the rotation speed of the drive engine 2, so the rotation speed of the front wheels 4a and 4b is variable. It is not easy to synchronize the rotation speeds of the rear wheels 1α and 1s, and the hydraulic pump 6 needs to have a large capacity and be a variable displacement pump. Since the hydraulic pump 6 has a large capacity, a hydraulic motor 5α is used.

5h will also have a large capacity, resulting in a hydraulic pump 6 and a hydraulic motor 5σ to the vehicle.

5b requires a large space, increases the weight of the entire vehicle, and the high cost of the town displacement pump as the hydraulic pump 6 makes the entire hydraulic control system expensive. There is a disadvantage in that the versatility of the device is reduced.

Therefore, the present invention does not require a large space when equipped on a vehicle, does not cause an unnecessary increase in the size of the vehicle, and furthermore, reduces the cost of the entire device, thereby increasing its versatility. The purpose of the present invention is to provide a new hydraulic control device for a hydraulically driven vehicle that can be improved.

[Means for solving problems]

In order to solve the above problems, the configuration of the present invention includes a hydraulic pump configured to be rotationally driven by a driving engine of a vehicle and to supply pressure oil to a hydraulic motor connected to an axle of the vehicle. In the hydraulic control device for a hydraulically driven vehicle, the hydraulic pump is a fixed displacement pump, and is configured to be rotated and driven via a transmission connected to a driving engine, and The drive engine is characterized in that an auxiliary pump is connected to the driving engine, and pressure oil from the auxiliary pump is supplied to the hydraulic motor.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

Figure 1 shows a vehicle in which the present invention is implemented, and shows a rear wheel 1α of the vehicle.

1h is formed to be driven by the vehicle's driving engine 2 via a transmission 3, while the front wheels 4α, 4b are driven by a hydraulic motor 5α connected to the front wheel axle.
, '5b by supplying pressure oil from the hydraulic pump 6,
It is configured to be driven. The hydraulic pump 6 is composed of a fixed capacity pump, and
A loincloth 3 is connected to the I-P transmission 3 and is configured to be rotationally driven by the driving engine 2 via the I-P transmission 3. Further, an auxiliary pump 6s is connected to a conduit 6α that allows the flow of pressure oil supplied from the hydraulic pump 6 to the hydraulic motors 5α and 5A. The auxiliary pump 6b is connected to the driving engine 2, is driven to rotate in synchronization with the rotation of the driving engine 2, and is driven by the hydraulic morph 5, which is a predetermined pressure oil.
α, 5bK can be supplied.

Here, in the present invention, the hydraulic pump 6 is a fixed capacity pump, and is connected to the transmission 3, and
The auxiliary pump 6b is connected to the driving engine 2, and the hydraulic motors 5α, 5 are connected to the hydraulic pump 6 and the auxiliary pump 6b.
Let us briefly explain why pressure oil is supplied to h.

First, the relationship between the front wheel drive load, the rotational speed of the hydraulic motor, and the discharge amount of the hydraulic pump will be considered.

Here, the rotation speed of the rear wheel drive @3a ---1-~NS rear wheel 1α (
1b) rotation speed --=-NR hydraulic pump 6 rotation speed
---Number of rotations of NP hydraulic motor 5α (5h) -N
Assuming that the rotation speed of M front wheel 4α (4h) is NF and the effective radius of the front and rear wheels is the same.

As a condition for the front and rear wheels to rotate at the same time, the following equation (1) holds true.

Np = NR----' (11 On the other hand, if the reduction ratio of the differential gear 3h is Kl, mechanically / does not change and is constant, so the rear wheel 1α (
The following equation (2) holds between the rotation speed NR of 16) and the rotation speed NS of the rear wheel drive shaft 3a.

NR= K/ x NS -----(21- Also, the rotation speed NF of the hydraulic pump 6 and the discharge amount Q of the hydraulic pump 6
The relationship with p is, when the volume of the hydraulic pump 6 is DP,
Theoretically, the following equation (3) is obtained.

Qp = Dp x NP -1--' (Similar to 31, the relationship between the rotation speed NM of the hydraulic motor 5α (56) and the inflow HQM to the hydraulic motor 5tZ (5A) is expressed as follows: When DM is used, the following equation (4) is theoretically obtained.

QM, = DM x NM ----- (41, and the rotation speed NM of the hydraulic motor 5α (5b) and the front wheel 4α (
If the reduction ratio is set to 2 between the rotation speed NF in 4b),
The following formula (5) holds true.

Ny=, Niko
h) If it is directly connected to the axle, KJ =
It becomes 1.

Since the two hydraulic motors 5α, 5h are driven by one hydraulic pump 6, the following equation (9) exists between the discharge amount QP of the hydraulic pump 6 and the inflow amount QM to the hydraulic motors 5α, 5A.
The formula holds true.

Qp = 2QM, --1-, (61-Here, by substituting equation (4) into equation (51) and substituting into equation (6), the following equation (7) is obtained.

λX to NY-, QM/DM, = Kz x QP/2DM
7-- (7) Substituting equation (3) into equation (7) yields equation (8) below.

Nv = K2x DP/, 2DM x Np
-----(81 and the rotation speed NR of the rear wheel 1α (1h)
In order to synchronize the rotation speed NF of the front wheel 4α (41I) with the rotation speed NF of the front wheel 4α (41I), the rotation speed Np of the hydraulic pump 6 becomes the following equation (91) from (IH21 and equation (8)).

"P= K'/Kx x 2DM/DP x Ns
----(g) Therefore, it is theoretically good if the hydraulic pump 6 is rotated by the rotating shaft 3C connected to the mission 3 so that the rotational speed NP of the above equation (9) is achieved.

However, the hydraulic pump 6 and the hydraulic motor 5α (5b)
Theoretically, the volumetric efficiency of is given by the above formula (31 (4j), but in general, slip (leakage) occurs due to the load pressure from the front wheel 4α (4h) side. Therefore, the load pressure is P, the leakage is When the coefficient is α1 and the slip coefficient is α, the discharge amount Qp of the hydraulic pump 6 is expressed by the following expression α0), and the inflow amount QM of the hydraulic motor 5a (5b) is expressed by the following old expression 1.

Qp=DpxNp-a, xP -------(1
01QM 7DMXNM+α, ×P −111 Old) When this 00) formula and the old) formula are illustrated, they become the 10th line of Fang 2 diagram and the 11th line of Fang 3 diagram. In addition, spear 2
Line 10 in the figure indicates that 1) pxNP=constant;
Line 11 in Figure 3 indicates that DMXNM-=constant.

By the way, if the drive torque for driving the front wheel 4α (4h) is TF, the pressure 1PO required for the hydraulic motor 5α (5h) is expressed by the following formula (121).

However, ηM is the mechanical efficiency of the hydraulic motor 5α (5h).

po = 2ffTF/2DMηM = ETF/DM
ηM ---' (121 Therefore, front wheel drive torque TF
The necessary conditions for generating are P = Po and Qp = DpxNp-αpxR) in the above equation 00) 11.
-----(10) QM = DM x NM +
aMx P□ (ill And the synchronization conditions are from the above (51f61 formula and 00) old) formula,
The following equation (13) holds true for the rotation speed NF of the front wheel 4α (4h).

NF = Ky (Dp x Np - P(1(ap +
2αM))/2DM-m--(131 Then, from the above formula (11(2)) and formula (131), the following formula α4 holds true for the rotation speed NF of the hydraulic pump 6.

NP='/Dp(K'/Ka X2DMxNs+Po
(αp+2αM))=K/to, x 2DM/DP
x Ns −4−(αp+2αM)/ppxP.

-111 α4 Therefore, as shown by the above equation 041, the rotation speed NF of the hydraulic pump 6 is the rotation speed NS of the rear wheel drive shaft 3α connected to the transmission 3. It is sufficient to increase the amount by an amount corresponding to the amount of slip (leakage) of 5a and 5b.

In other words, as shown in Figure 4, when the slip (leak) fi expressed by the above equation (9) is not taken into account, the slip (leak) expressed by the above equation α4, as shown by line 9 in the figure, When considering the amount, it is sufficient to set the characteristic as shown by line 14 in the figure.

However, as shown by line 6 in Figure 4, line 14 in the figure attempts to obtain the desired amount of slip (leakage), which cannot be controlled depending on Mission 3.

Therefore, in the present invention, the following considerations are made.

First, the capacity of the hydraulic pump 6 is increased, and the practical range of the rotation speed NS of the rear wheel drive shaft 3α is determined as shown in Figure 4.
NS/~Ns-, and the hydraulic pump 6 at this time
With respect to the required rotational speed NP/-Npx, if the rotational speed NP of the hydraulic pump 6 is NP/~NP, and the hydraulic pump capacity in this state is DP, Net in Fig.
, The required flow rate of the hydraulic pump 6 at the Npt point is calculated from the above equation (141) to the following equation (151).

NP/ x Dp=//', x 2DMXN8 z
+(ap+ 2αu) x PaHere, considering equation (9), NP/= becomes //, 2 Become.

DP=1/(Kl/2×2DM/DP×Nsl)×(
Kl/toλ×2DMXNS/+(ap+2αM)Pot
=2DI/2KIDMNSl×(αp+2αM
) Pa-111 〇〇 However, if N5 = NS, 2, and considering the same, the required flow rate will be the following formula a'7).

“×D”=2Kl”M/Ka XN8J+ (ap+
212M) PO--1-a force However, the discharge amount of the hydraulic pump 6 with increased capacity is calculated from the NSλ value of the above equation (9) and the above (161 equation), N⇠×Dp
= 2DMK // to ppxNsa (DP+ to 2DP
/2/DMNSt×(αp+2αM)Pol, that is, the following equation 081 is obtained.

N xl) P=2/DM/2 XN5J+ (α
p+2αM) POXNS, 2/N5l Therefore, the surplus flow rate ΔQ is the difference between the above sister formula and (181 formula), and becomes the following formula 09.

△Q=NP2X Dp-NPJ XDP=(αp+2α
M) P It is large during fluctuations, and if the surplus flow rate ΔQ is relieved, the so-called power loss becomes large.

In addition, the diagonally shaded part divided by the 14th line and the 6th line in FIG. 4 indicates the surplus flow rate ΔQ.

From the above, in the present invention, the leakage QL in the hydraulic pump 6 and the hydraulic motors 5α, 5h is replenished by the auxiliary pump 6b, which is a pump other than the hydraulic pump 6. Then, this QL becomes the following formula (■).

QL = (ap + 2txM) Po ---
1 (201) Next, since the QL itself has an extremely small flow rate, a small pump is sufficient.As mentioned above, if the capacity of the hydraulic pump 6 is increased, the relief flow rate will increase depending on the rotational fluctuation. It is possible to avoid the inconvenience of increased power loss and so-called power loss.

Moreover, if the above-mentioned auxiliary pump 6b is attached to the drive engine 2 instead of the transmission 3, even if the flow rate of the auxiliary pump 66 changes due to rotational fluctuations of the drive engine 2, the above-mentioned mission This is less than the variable excitation width in the case of attaching it to No. 3, and the width of so-called power loss can be reduced.

That is, the capacity Dc of the auxiliary pump 6b is given by the following equation (211) at the minimum value NE/hour, as shown in Fig. 5, when the rotational speed of the driving engine 2 is NE.

DC=Qc, -1--(21+Then, the discharge amount Qcλ at the maximum value N82 is Qcz=D
cxNz2, and the surplus flow rate ΔQC is expressed by the following formula.

ΔQa=Qca-QL=DcxN]l-DcxNmzkopc (NZ--NEz) =DCNF! / (NP'J/NE/-1)NF2 =QL(/N,-1) -----(221Here,
The assumed surplus flow rate in the hydraulic pump 6 is the above 0.
From Equation 9 and Equation (■), the following (Equation 191) is obtained.

At this time, N11! Assuming that J/NK 1 = 3 and assuming that the variation ratio of mission 3 is 10, NMλ/NM/ in the above equation 06 becomes 30, and therefore, the above (
ΔQc in Equation 221 is 2QL, whereas ΔQ is 29QL.

That is, the so-called power loss in the hydraulic pump 6 is much greater than the power loss in the auxiliary pump 6b.

Therefore, in the present invention, an auxiliary pump 6b is provided on the drive engine 2 side, and the auxiliary pump 6b replenishes the amount of slip (leakage) in the hydraulic pump 6 and the hydraulic motors 5α, 5b.

FIG. 6 shows a circuit diagram as an embodiment of a hydraulic control device for a hydraulically driven vehicle according to the present invention. Let me explain this a little bit.

The hydraulic pump 6 is connected to the mission 3 and is configured to be rotationally driven as the mission 3 rotates. The auxiliary pump 6h is connected to the driving engine 2, and is driven to rotate as the driving engine 2 rotates.

In this embodiment, the hydraulic pump 6 is a bidirectional pump and a fixed customer fi5. Further, the auxiliary pump 6b is a one-way pump.

On the other hand, the hydraulic motors 5α and 5b connected to the axles of the front wheels 4α and 4h are connected from both directions with conduits 6α that supply pressure oil from the hydraulic pump 6. It is configured to rotate forward or reverse depending on the supply of pressurized oil.

Further, from the auxiliary pump 6h, the pipe line 6α (fang 6
An auxiliary conduit 6h connected to the upper side in the figure is extended. A flow control valve 7 is disposed in this auxiliary pipe 6h, and the flow control valve 7 is used to set and adjust the flow rate. Furthermore, a switching valve 8 is disposed in the auxiliary pipe line 6b, and normally hydraulic motors 5α, 5
It is located at a normal rotation position 8α in which the normal rotation of A is defined as normal rotation, and has a reverse rotation position 8h that allows the hydraulic motors 5α and 5h to reverse rotation by switching the normal rotation position 8α. Note that this switching is performed by operating the lever 8c, but it goes without saying that the lever 8C may be a gear switching lever for backing up the vehicle.

Pressure oil from the auxiliary pump 6h when the switching valve 8 is in the reverse rotation position 8b is configured to be supplied to the hydraulic motors 5α, 5b via another auxiliary conduit 6b. Further, the surplus flow when the discharge flow rate from the auxiliary pump 6b is controlled by the flow control valve 7 is returned to the tank IOK via the unload circuit 9. Note that in the circuit in this embodiment, the hydraulic pressure required for rotationally driving the hydraulic motors 5α, 5A, that is, the hydraulic pressure supplied from the hydraulic pump 6 and the auxiliary pump 6b, exceeds the set value of the hydraulic motors 5α, 5h. When this occurs, a relief valve 11 is provided to relieve this, and a check valve 12 that enables the operation of the relief valve 11 and a supply of the relieved pressure oil to the main pipe line 6α are provided. A check valve 13 is provided.

The operation of the hydraulic control circuit according to the present invention formed as described above will be briefly explained.

First, when the driving engine 2 is operated, the auxiliary pump 6
h is rotationally driven, and the hydraulic pump 6 is rotationally driven in the normal rotation direction by the operation of the mission 3. As a result, the set pressure oil is supplied from the hydraulic pump 6 to the hydraulic motors 5a, 5b, and the pressure oil from the auxiliary pump 6b is also supplied to the hydraulic motors 5α, 5A under the control of the flow control valve 7. The Rukoto. - As a result, the front wheels 4α and 4b are driven in the forward rotation direction, and the rear wheel l
In addition to the drive of α, 1h (see FIG. 1), a so-called four-wheel drive or a two-wheel drive driving situation in which only the front wheels are driven is obtained.

Furthermore, if the hydraulic pump 6 is reversed when the vehicle is reversed, the hydraulic motor 5α.

56 enters the reverse rotation state, the pressure oil from the auxiliary pump 6b replenishes the hydraulic motors 5CL and 5A, which are rotated in reverse, with a predetermined amount of pressure oil by switching the switching valve 8.

In the above operation, if the drive load of the front wheels 4α, 4b exceeds the set torque, the hydraulic pump 6 and the hydraulic motor 5
As the leakage amount of α, 5b increases, the front wheels 4α, 4
The rotational speed of b becomes lower than the rotational speed of rear wheels 1α and Ib, and the driving force on the vehicle increases on the rear wheels 1a and 1b and decreases on the front wheels 4α and 46. Become. However, as the pressure decreases and the amount of leakage decreases, the rotational speed of the hydraulic motors 5α and 515 increases, making it possible to maintain the set torque.

Conversely, when the driving load of the front wheels 4α, 4b is reduced from the set value, the amount of leakage is reduced, the rotational speed of the hydraulic motors 5α, 5b increases, and the drive load of the rear wheels 1α, lb. On the other hand, the rotational speed of the front wheels 4α, 4A increases, and the driving force is actively applied to the front wheels 4α, 4h, so that the pressure increases and the set pressure is maintained.

In other words, under four-wheel drive conditions, even if load fluctuations occur on the front wheels 4α and 4h, the hydraulic control device itself maintains so-called self-balancing and always stably drives the front wheels 4α and 4h.
, 4b driving force will be generated.

Additionally, if the drive load on the rear wheels increases, the rotational speed of the transmission 3 and drive engine 2 will decrease, and at the same time the rotational speed of the hydraulic pump 6 will also be reduced, causing the rotational balance between the front and rear wheels to collapse. There isn't. Conversely, if the rear wheel load decreases, the rotational speed of the 1-drive engine 2 increases, and the rotations of the front and rear wheels increase in synchronization.

That is, even when the load on the rear wheels 1α, 1b changes, the front wheels 4α, 4b are always driven by the set torque due to the self-balancing described above, and the desired synchronous rotation and constant torque drive is achieved by a separate synchronous control system and torque. This can be done without using a control system or the like.

In addition, in the above operation, the front wheels 4α, 45 and the rear wheel lα
, IA and the predetermined torque are made possible by controlling the flow rate of the auxiliary pump 6b that replenishes the leakage of the hydraulic pump 6 and the hydraulic motors 5α and 5h, and the torque distribution between the front and rear wheels is , variable control is easily possible by finely adjusting the flow rate of the auxiliary pump 6b.

If the discharge amount of the auxiliary pump 6h is set to zero, the pressure setting in the control device becomes zero, and the front wheels 4α, 4b do not share the driving force. Furthermore, if the pressure oil from the auxiliary pump 6b is replenished to the opposite side, that is, the low pressure side, the predetermined power transmission is reversed, and the hydraulic motors 5α, 5A
The hydraulic pump 6 functions as a hydraulic pump, and the hydraulic pump 6 functions as a hydraulic motor. As a result, the vehicle travels by driving the rear wheels, and the front wheels 4a.

The rotation of 4b causes a so-called brake to be applied, but the braking force is applied to the mission 3 in the circuit.
The pressure loss caused by the braking force is only the pressure loss of the circuit.

Therefore, by variably controlling the leakage amount of the hydraulic pump 6, hydraulic motors 5a, 5A, and the flow rate from the small auxiliary pump 6b, a predetermined transmitted power can be freely controlled.

Furthermore, in the above operation, if the flow rate from the auxiliary pump 6b is reduced to zero, the rear wheel 1α of the vehicle is moved.

Although it will only run for 1 hour, the rear wheels are 1α.

If 1b bounces on an uneven road surface, etc.,
The driving force of the rear wheels 1a, lb is lost, and the driving engine 2
As the rotation speed of the hydraulic pump 4α increases,
, 4b increases, the pressure in the circuit increases overall, and until the ground contact force of the rear wheels 1α and Ih is restored, the front wheels are in the driving state and the transmission of the drive engine 2 is Loss can be prevented.

In the above, the present invention has been explained as an embodiment of a four-wheel drive vehicle in which the rear wheels are mechanically driven by one drive engine and the front wheels are hydraulically driven. Of course, the same applies to a four-wheel drive vehicle in which the rear wheels are hydraulically driven, or a two-wheel drive vehicle in which the front wheels are hydraulically driven.

〔Effect of the invention〕

From the above, according to the present invention, the following effects can be obtained.

(1) Since it is possible to use a fixed capacity hydraulic pump and hydraulic motor, it is possible to downsize each of them, and as a result, when equipping a vehicle with a hydraulic control device,
The mounting space can be reduced and the overall weight of the vehicle can be prevented from increasing.

(2) Since it can be a fixed displacement hydraulic pump, it is cheaper than a variable displacement hydraulic pump, and the cost of the entire device can be reduced, and its versatility can be expected.

(3) The hydraulic pump is driven by the transmission side, and the auxiliary pump is driven by the drive engine, so the rotation speed of the rear wheels due to the engine and drive has an extremely wide range of rotation, and the rotation speed of the front wheels due to the hydraulic drive. It is possible to control the rotation speed in synchronization with the engine speed, and since the auxiliary pump is driven by the engine, which is less likely to fluctuate in rotation, there is an advantage that so-called power loss can be reduced.

(,ll Synchronous control and power transmission torque (pressure) control can be controlled by the discharge flow rate of the auxiliary pump that supplements the pressure of the hydraulic pump and hydraulic motor, and the torque distribution between the front and rear wheels is controlled by the auxiliary pump. The flow rate
There is an advantage that variable control can be easily achieved by making fine adjustments.

[Brief explanation of drawings]

Figure 1.1 is a diagram schematically showing a vehicle according to an embodiment of the present invention, Figure 2 is a custom line diagram showing the relationship between the discharge amount of the hydraulic pump and the load pressure, and Figure 3 is a diagram showing the relationship between the hydraulic pump and the load pressure. A characteristic diagram showing the relationship between the inflow amount of the motor, a characteristic diagram showing the relationship between the rotation speed of the rear wheel axle and the rotation speed of the hydraulic pump, and a characteristic diagram showing the relationship between the rotation speed of the rear wheel axle and the rotation speed of the hydraulic pump. A characteristic diagram showing the relationship of surplus flow rate, Figure 6 is a circuit diagram according to an embodiment of the present invention, and Figure 7 is a diagram schematically showing a vehicle according to a conventional example. 1α, 1b...rear wheel, 2...1 drive engine, 3
...Mission, 4a, 4b...Rear wheel, 5α, 5A
...Hydraulic motor, 6...Hydraulic pump, 6α...Pipe line, 6z...Auxiliary pump, 7...Flow control valve, 8...Switching valve. Izumi Ohno 1 and i (□1'-,,j Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) Rotationally driven by the vehicle's driving engine,
In a hydraulic control device for a hydraulic drive vehicle, which includes a hydraulic pump configured to supply pressure oil to a hydraulic motor connected to an axle of the vehicle, the hydraulic pump is a fixed displacement pump, and the hydraulic pump is a fixed capacity pump. formed to be rotationally driven via a transmission connected to the engine, and
1. A hydraulic control device for a hydraulically driven vehicle, characterized in that an auxiliary pump is connected to a driving engine, and pressure oil from the auxiliary pump is supplied to a hydraulic motor. (2) A hydraulic control device for a hydraulically driven vehicle according to claim 1, wherein the pressure oil from the auxiliary pump is supplied to the hydraulic motor under flow control control by a flow control valve.