JP2002339906A - Drive control device for cooling fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the control and the structure of a swash plate of a hydraulic pump, and reduce the cost by eliminating a feedback mechanism in a hydraulic circuit for driving a cooling fan. SOLUTION: A load pressure PL of the hydraulic pump 2 corresponding to a fan target rotation speed NF is found. The capacity q of the hydraulic pump 2 is found based on the fan target rotation speed NF and the rotation speed Ne of an engine 1. The extent of a rotation moment rotating the swash plate 2a (locker cam 18) in the side of a maximum capacity qMAX is found based on the found load pressure PL and the capacity q. Then, a control signal (EPC(Electronic Pressure Control) output pressure) Pe necessary for generating the rotation moment rotating it on the side of a minimum capacity qMIN, which is balanced with the rotation moment rotating on the side of the maximum capacity qMAX, is found. The found control signal Pe is outputted to a piston 3 of a swash plate driving means 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling the driving of a cooling fan.

[0002]

2. Description of the Related Art A cooling fan is driven by pressure oil discharged from a variable displacement hydraulic pump. In this case, it is necessary to control the capacity (swash plate) of the hydraulic pump so that the rotation speed of the cooling fan becomes the target rotation speed.

Conventionally, the capacity of a hydraulic pump has been controlled using a mechanism shown in a hydraulic circuit of FIG. The hydraulic circuit shown in FIG. 6 is described in, for example, Japanese Patent Application Laid-Open No. 8-284806.

That is, in the hydraulic circuit shown in FIG. 6, the hydraulic pump 2 is driven by the engine 1. Hydraulic pump 2
Is supplied to a hydraulic motor (not shown) via an oil passage 7 to drive the hydraulic motor. When the hydraulic motor is driven, a cooling fan (not shown) rotates.

The hydraulic pressure Pp discharged from the hydraulic pump 2 is supplied to oil passages 7 and 8.
Is supplied to the oil chamber on the small diameter side of the servo piston 19 through the shaft. The hydraulic pressure Pp discharged from the hydraulic pump 2 is supplied to the oil passages 7, 8, 8
A is supplied to the inflow port of the control valve 22 as drive pressure oil via a. The discharge pressure oil Pp of the hydraulic pump 2 is
The pilot pressure oil is supplied to the pilot port of the control valve 22 via 8, 8a, 8b. When the control pressure oil flows from the control valve 22 into the oil chamber on the large diameter side of the servo piston 19 via the oil passage 24, the tilt angle of the swash plate 2a of the hydraulic pump 2 becomes small. When the control pressure oil flows out from the oil chamber on the large diameter side of the servo piston 19 to the control valve 22 via the oil passage 24, the tilt angle of the tilt angle 2a of the hydraulic pump 2 increases.

[0006] The servo piston 19 changes the displacement q of the swash plate 2a of the hydraulic pump 2 to change the capacity q of the hydraulic pump 2. The servo piston 19 moves to a position corresponding to the tilt angle of the swash plate 2a, that is, the displacement volume q of the hydraulic pump 2, and the position of the servo rod 21 connected to the servo piston 19 changes with this movement. With the movement of the servo rod 21, the spring force of the spring 23 acting on the control valve 22 changes. The servo rod 21 is a hydraulic pump 2
Is provided to feed back the tilt angle of the swash plate 2a.

The control valve 22 changes the tilt angle (capacity q) of the swash plate 2a of the hydraulic pump 2 according to the discharge pressure Pp of the hydraulic pump 2. If the rotation speed of the engine 1 is constant, control is performed so that the absorption horsepower of the hydraulic pump 2 does not exceed the horsepower generated by the engine 1. Spring 23 acting on control valve 22
The set maximum torque (set maximum horsepower) of the control valve 22 is determined according to the setting of the spring force (the position of the servo rod 21).

Next, the operation of the hydraulic circuit shown in FIG. 6 will be described.

When the discharge pressure of the hydraulic pump 2 increases, the pilot pressure applied to the pilot port of the control valve 22 via the oil passage 8b increases, so that the control valve 22 is pushed to the left in the figure. As a result, control pressure oil flows from the control valve 22 into the oil chamber on the large diameter side of the servo piston 19 via the oil passage 24. At this time, the same pressure acts on the large-diameter side and the small-diameter side of the servo piston 19, respectively, but the servo piston 19 is driven to the qMIN side (minimum capacity side) due to the difference in the diameter (pressure receiving area). This allows the hydraulic pump 2
Of the swash plate 2a, the displacement angle q (capacity q) of the hydraulic pump 2 is reduced, and the flow rate discharged from the hydraulic pump 2 is reduced.

As the servo piston 19 moves to the qMIN side, the servo rod 21 moves in the same direction and the control valve 2
The set spring force of the second spring 23 is increased. When the set spring force of the spring 23 of the control valve 22 is increased, the control valve 22 is pushed rightward in the drawing. Thereby, the control pressure oil flows out from the oil chamber on the large diameter side of the servo piston 19 to the control valve 22 via the oil passage 24. As a result, the servo piston 19 becomes qMA
Driven to the X side (maximum capacity side). As a result, the tilt angle of the swash plate 2a of the hydraulic pump 2 increases, the displacement volume q (capacity q) of the hydraulic pump 2 increases, and the flow rate discharged from the hydraulic pump 2 increases.

The swash plate 2a of the hydraulic pump 2 is controlled so that the product of the discharge pressure of the hydraulic pump 2 and the displacement q (capacity) does not exceed a certain torque by repeating the above-described operation alternately.

[0012]

According to the hydraulic circuit shown in FIG. 6, the servo piston, the servo rod 21, the control valve 2
2 and the like, the tilt angle of the swash plate 2a of the hydraulic pump 2 is fed back to control the swash plate 2a of the hydraulic pump 2 to change. Therefore, even if the discharge pressure of the hydraulic pump 2 fluctuates according to the magnitude of the load, the tilt angle of the swash plate 2a can be determined so as not to exceed a certain torque.
However, if a hydraulic circuit is constructed by providing such a feedback mechanism, the structure becomes complicated and the cost increases.

On the other hand, when the cooling fan is driven by the discharge pressure oil of the hydraulic pump, the magnitude of the load is uniquely determined according to the target fan speed, and the target fan speed and the load of the hydraulic pump 2 are determined. The present inventors have found that the pressure PL (discharge pressure) has a characteristic of perfectly matching. Therefore, even if the discharge pressure of the hydraulic pump 2 fluctuates according to the magnitude of the load, the swash plate 2
The conventional feedback mechanism that can determine the tilt angle of a so as not to exceed a fixed torque can be omitted in the hydraulic circuit that drives the cooling fan.

Accordingly, the present invention is to simplify the control of the swash plate 2a of the hydraulic pump 2 by omitting the feedback mechanism in the hydraulic circuit for driving the cooling fan, thereby simplifying the structure and reducing the cost. It is to be solved.

[0015]

A first aspect of the present invention is a hydraulic pump (2) driven by an engine (1) and a hydraulic pump (2) driven by hydraulic oil discharged from the hydraulic pump (2). Hydraulic actuator (14)
A cooling fan (15) driven by the hydraulic actuator (14); and a swash plate (2a, 1a) of the hydraulic pump (2) according to the discharge pressure of the hydraulic pump (2).
Swash plate driving means (28) for changing the swash plate (2a, 18) of the hydraulic pump (2) to the minimum capacity side in accordance with a control signal while changing the swash plate (8) to the maximum capacity side; A drive control device for a cooling fan, comprising control means (30, 6) for outputting a control signal to the swash plate drive means (28) so that the rotation speed of (15) becomes the fan target rotation speed. In the above, the load pressure of the hydraulic pump (2) corresponding to the fan target rotation speed is obtained, and the capacity of the hydraulic pump (2) is obtained based on the fan target rotation speed and the rotation speed of the engine (1). A control signal is obtained based on the obtained load pressure and capacity, and the obtained control signal is output to the swash plate driving means (28).

According to the first invention, as shown in FIG. 4, the load pressure PL of the hydraulic pump 2 corresponding to the fan target rotational speed NF
Is required. Then, the capacity q of the hydraulic pump 2 is obtained based on the fan target rotation speed NF and the rotation speed Ne of the engine 1. Then, based on the obtained load pressure PL and capacity q, as shown in FIG.
Is required to rotate the swash plate 2a (rocker cam 18) to the maximum capacity qMAX side. Then, as shown in FIG. 5 (a), the minimum capacity qMIN balanced with the rotational moment to be rotated toward the maximum capacity qMAX.
A control signal (EPC output pressure) Pe required to generate a rotational moment to rotate the side is obtained. Then, the obtained control signal Pe is output to the piston 3 of the swash plate driving means 28.

According to the first aspect, the control signal Pe required for rotating the cooling fan 15 at the target fan speed NF is calculated and output to the swash plate driving means 28, whereby the hydraulic pump 2 Since the plate 2a can be controlled according to the magnitude of the load, the feedback mechanism as shown in FIG. 6 can be omitted. For this reason, the structure of the hydraulic circuit is simplified, and the cost can be reduced.

According to a second aspect of the present invention, in the first aspect, a first map for obtaining the load pressure of the hydraulic pump (2) from the target fan speed is stored in advance, and the load pressure of the hydraulic pump (2) and the hydraulic pump (2) are determined. A second map for obtaining a control signal is stored in advance based on the capacity of 2), and the control signal is obtained in accordance with the stored contents of the first map and the second map.

According to the second invention, the first map shown in FIG. 4 is stored in advance, and the load pressure P
L is required.

A second map shown in FIG. 5 is stored in advance, and control is performed using the second map based on the load pressure PL obtained from the first map and the capacity (target capacity) q of the hydraulic pump 2. The signal Pe is determined.

In a third aspect based on the first aspect, the swash plate drive means (28) is configured to apply a force corresponding to the discharge pressure of the hydraulic pump (2) to the swash plate (2a, 18) of the hydraulic pump (2). )
And a first piston (29) for tilting the swash plate (2a, 18) to the maximum displacement side, and a swash plate (2a, 18) of the hydraulic pump (2) with a force corresponding to a control pressure. A second piston (3) for pushing and tilting the swash plate (2a, 18) to the minimum capacity side, wherein the control means (30, 6) is provided with respect to the second piston (3). It is characterized by including a control valve (6) for outputting a control pressure.

According to the third invention, as shown in FIG. 1, the first piston 29 is driven by a force corresponding to the discharge pressure of the hydraulic pump 2.
Pushes the swash plate 2a (rocker cam 18) of the hydraulic pump 2 to tilt the swash plate 2a (rocker cam 18) toward the maximum capacity qMAX. On the other hand, the control pressure Pe is output from the control valve 6 to the second piston 3, and the second piston 3 pushes the swash plate 2a (rocker cam 18) with a force corresponding to the control pressure Pe. When the swash plate 2a (rocker cam 18) has the minimum capacity qM
Swing to the IN side.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a drive control device for a cooling fan will be described below with reference to the drawings.

FIG. 1 shows a hydraulic circuit according to the embodiment.

The hydraulic circuit shown in FIG. 1 is mounted on a construction machine such as a hydraulic shovel, a wheel loader, and a bulldozer.

The variable displacement hydraulic pump 2 includes a cooling fan 1
5 is used as a drive hydraulic pressure source.

The hydraulic pump 2 is driven by the engine 1. The engine 1 is provided with an engine speed sensor 17 for detecting the speed Ne of the engine 1. As the engine speed sensor 17, for example, a pulse pickup can be used.

As the swash plate 2a of the hydraulic pump 2 changes, the displacement q of the hydraulic pump 2, that is, the capacity q changes.

The displacement volume (capacity) of the hydraulic pump 2 is:
It changes when the swash plate drive unit 28 operates. The swash plate drive unit 28 controls the rocker cam 18 as the swash plate 2a to
The piston 3 swings toward the minimum displacement qMIN with the point as a fulcrum, and the piston 29 swings the rocker cam 18 toward the maximum displacement qMAX with the point A as a fulcrum. A plurality (for example, six) of the pistons 29 are provided in the hydraulic pump 2 as shown in FIG. The hydraulic pump 2 sucks the pressure oil in the tank 9 and discharges the high-pressure oil compressed by the piston 29 in the cylinder block as the discharge pressure oil Pp from the discharge port. As shown in FIG. 1, the discharge port of the hydraulic pump 2 and the piston 29 communicate with each other through an oil passage 8, and a high discharge pressure, that is, a load pressure PL acts on the piston 29.

Therefore, the piston 29 pushes the rocker cam 18 with a force corresponding to the load pressure PL of the hydraulic pump 2, and swings the rocker cam 18 toward the maximum displacement qMAX. A force acts on the rocker cam 18 at the position of the center of gravity of the plurality of pistons 29.

On the other hand, the piston 3 pushes and rocks the rocker cam 18 with a force corresponding to the control pressure Pe flowing into the oil chamber 5. Rocker cam 18 on piston 3
Is provided with a spring 4 for applying a constant load.

The discharge pressure oil Pp of the hydraulic pump 2 is supplied to the inflow port of the fan drive hydraulic motor 14 via the oil passage 7. The hydraulic motor 14 is a fixed displacement hydraulic motor.

A cooling fan 15 is attached to the output shaft of the hydraulic motor 14.

The hydraulic motor 14 is rotated by the pressure oil discharged from the hydraulic pump 2 flowing from an inflow port (for example, port MA) through the oil passage 7 to rotate the cooling fan 15. The pressure oil flowing out of the outflow port (for example, port MB) of the hydraulic motor 14 is returned to the tank 9 via the oil passage 12.

A hydraulic motor 14 is provided on the oil passages 7 and 12.
A switching valve 13 for switching the rotation direction is provided.
The switching valve 13 is switched according to a signal output from the controller 30, for example.

When the switching valve 13 is in the switching position shown in FIG. 1, the hydraulic oil discharged from the hydraulic pump 2 is supplied to one port MA of the hydraulic motor 14 and the cooling fan 15
Rotates forward. When the switching valve 13 is switched from the position shown in FIG. 1, the pressure oil discharged from the hydraulic pump 2 is supplied to the other port MB of the hydraulic motor 14, and the cooling fan 15 rotates in the reverse direction.

A coolant (cooling water) as a cooling medium of the engine 1 is guided to a radiator 16 as a radiator. The heat of the coolant is radiated by the radiator 16. The cooling fan 15 is provided to face the radiator 16. Therefore, the coolant is cooled by the rotation of the cooling fan 15. The radiator 16 is provided with a temperature sensor 25 for detecting a temperature t of the coolant.

The electromagnetic proportional control valve (EPC valve) 6 reduces the pressure oil supplied from the hydraulic pressure source 26 in proportion to the magnitude of the electric signal i (current i) applied to the electromagnetic solenoid 6a, and As the control pressure Pe (hereinafter, EPC output pressure Pe).

Referring now to FIG. 2, the relationship between the movement of the rocker cam 18 of the hydraulic pump 2 shown in FIG. 1 and the displacement volume q (capacity q) will be described in further detail. FIG. 2 shows a cross section of a main part of the hydraulic pump 2.

As shown in FIG. 2, the hydraulic pump 2 is provided with a rocker cam 18 corresponding to the swash plate 2a. The rocker cam 18 can swing about the point A in the figure as a fulcrum. When the rocker cam 18 swings, the swash plate 2a
Of the hydraulic pump 2 changes, the displacement angle (capacity) q of the hydraulic pump 2 changes. When the rocker cam 18 rotates clockwise in the drawing, the capacity q of the hydraulic pump 2 changes to the maximum capacity qMAX. FIG. 2A shows a state when the capacity q of the hydraulic pump 2 reaches the maximum capacity qMAX.

On the other hand, when the rocker cam 18 rotates counterclockwise in the figure, the capacity q of the hydraulic pump 2 becomes the minimum capacity qMI.
It changes to the N side. FIG. 2B shows a state when the capacity q of the hydraulic pump 2 has reached the minimum capacity qMIN.

The rotational moment for rotating the rocker cam 18 counterclockwise in the figure, ie, toward the minimum capacity qMIN, is determined according to the magnitude of the EPC output pressure Pe supplied to the oil chamber 5 of the piston 3.

The hydraulic pump 2 acting on the piston 29
The rotational moment for rotating the rocker cam 18 clockwise in the figure, that is, toward the maximum capacity qMAX, is determined according to the magnitude of the discharge pressure, that is, the load pressure PL.

When the EPC output pressure Pe is small, the rotational moment for rotating the rocker cam 18 counterclockwise in the drawing, that is, to the minimum displacement qMIN becomes small, and the displacement q of the hydraulic pump 2 becomes the maximum displacement as shown in FIG. It changes to the qMAX side.

On the other hand, when the EPC output pressure Pe is large, the rocker cam 18 is moved counterclockwise in FIG.
The rotational moment to rotate to the MIN side increases, and the capacity q of the hydraulic pump 2 changes to the minimum capacity qMIN side as shown in FIG.

As described above, the discharge pressure oil Pp of the hydraulic pump 2
As the discharge pressure, that is, the load pressure PL increases, the force acting on the piston 29 increases, and the rotational moment for rotating the rocker cam 18 toward the maximum displacement qMAX increases.

Further, as the EPC output pressure Pe supplied from the electromagnetic proportional control valve 6 to the oil chamber 5 of the piston 3 increases, the force acting on the piston 3 increases, and the rocker cam 18 rotates to the minimum capacity qMIN. The rotating moment to be increased.

When these two rotational moments are balanced, the rocking position of the rocker cam 18 is determined, the tilt angle of the swash plate 2a of the hydraulic pump 2 is determined, and the displacement q (capacity q) of the hydraulic pump 2 is determined.

The piston 3 and the electromagnetic proportional control valve 6 are housed in the pump body 10 of the hydraulic pump 2 together with the piston 29 of the hydraulic pump 2. The switching valve 13 is built in the motor body 20 of the hydraulic motor 14.

In FIG. 1, the controller 30
The engine speed Ne detected by the engine speed sensor 17 is input and the temperature t of the coolant detected by the temperature sensor 25 is input. A signal i (current i) is output to the electromagnetic proportional control valve 6.

Next, with reference to FIG. 3, the processing executed by the controller 30 shown in FIG. 1 will be described.

The first map shown in FIG. 4 is stored in the controller 30 in advance.

FIG. 4 shows the relationship between the coolant temperature t or the fan speed NF and the load pressure PL. That is, when the coolant temperature t or the fan rotation speed NF is given, the load pressure PL can be uniquely obtained using the first map. The coolant temperature t or the fan speed NF has a linear relationship with the load pressure PL. Note that the correspondence shown in FIG. 4 is stored in a data table format, and when a temperature t or a fan speed NF is given, the corresponding data of the load pressure PL is read from the data table. Also, instead of using a data table format, the temperature t
Alternatively, it may be stored in the form of an arithmetic expression for calculating the load pressure PL from the fan speed NF. In this case, when the temperature t or the fan speed NF is given, the load pressure PL can be calculated by substituting this value into an arithmetic expression.

The controller 30 previously stores a second map shown in FIG.

FIG. 5 is a second map for obtaining the EPC output pressure Pe based on the target swash plate position (target capacity) q of the hydraulic pump 2 and the load pressure PL obtained from the first map of FIG. Is shown.

The second map is shown in FIGS. 5A and 5B.
Each map is shown. The map shown in FIG. 5B is a target swash plate position (target capacity) of the hydraulic pump 2.
4 is a map for obtaining the magnitude of a qMAX-side rotational moment for rotating the rocker cam 18 to the maximum capacity qMAX side based on q and the load pressure PL obtained from the first map in FIG. Further, the map shown in FIG.
Is a map for obtaining an EPC output pressure Pe required to generate a qMIN-side rotational moment for rotating to the minimum capacity qMIN that is balanced with the rotational moment obtained from the map of FIG. Note that the second map shown in FIG. 5 may be stored in the form of a data table or may be stored as an arithmetic expression, similarly to the first map shown in FIG.

As shown in FIG. 3, first, at step 101, a detection signal indicating the temperature t is input from the temperature sensor 25 to the controller 30 at every predetermined sampling time.

Next, a fan target rotation speed NF corresponding to the temperature t is obtained. Temperature t and target fan speed NF
Is a unique relationship, for example, the relationship shown on the vertical axis of the graph of FIG.
F is obtained (step 102).

Next, the cooling fan 15 is set in step 1
The discharge flow rate Q (l / min) of the hydraulic pump 2 necessary for rotating the fan at the fan target rotation speed NF obtained in step 02 is obtained (step 103). Next, the current engine speed Ne is input to the controller 30 from the engine speed sensor 17. Therefore, a target swash plate position (target capacity) q of the hydraulic pump 2 is determined based on the engine speed Ne and the required pump discharge flow rate Q determined in step 103. For example, it is assumed that q1 is obtained as the target swash plate position (target capacity) q of the hydraulic pump 2 (step 1).
04).

On the other hand, when the fan target rotation speed NF is obtained in step 102, the load pressure PL corresponding to the fan target rotation speed NF is obtained by using the first map shown in FIG. For example, as shown by a broken line in FIG. 4, when t1 is given as the temperature t, a fan target rotation speed NF1 corresponding thereto is obtained, and a load pressure PL1 corresponding to the fan target rotation speed NF1 is obtained.

Next, based on the load pressure PL1 obtained from the first map of FIG. 4 and the target swash plate position (target capacity) q1 obtained in step 104, the corresponding EPC output pressure Pe1 is calculated as shown in FIG. Is obtained using the second map shown in FIG.

Specifically, the line L corresponding to the load pressure PL1
1 is selected from the plurality of lines L in FIG. Therefore, as shown by a broken line in FIG. 5B, the target swash plate position (target capacity) q1 is determined from the intersection of the selected line L1.
Is obtained on the qMAX side.

Then, as shown by the broken line in FIG. 5B, the EPC output pressure Pe1 required to generate the qMIN-side rotational moment that matches the qMAX-side rotational moment is obtained.

As described above, when the rocker cam 18 of the hydraulic pump 2 is rotated to the maximum displacement qMAX side,
The X-side rotational moment is obtained from the map shown in FIG. 5B, and qMIN balanced with the qMAX-side rotational moment
EPC output pressure P required to generate side rotation moment
e1 is obtained from the map of FIG. 5A (step 10).
5). Then, the controller 30 obtains the obtained E
An electric command (current) i corresponding to the PC output pressure Pe1 is output to the electromagnetic proportional control valve 6 (step 106). Thereafter, the procedure shifts to step 101 and steps 101 to 1
Step 06 is repeated.

For this reason, from the electromagnetic proportional control valve 6, the EPC
The output pressure Pe1 is output and supplied to the oil chamber 5 of the piston 3.

Therefore, the swash plate 2a of the hydraulic pump 2 is positioned at a swash plate position corresponding to the fan target rotation speed NF.
The capacity q of the hydraulic pump 2 becomes the target capacity q1 obtained in step 104 of FIG.

As described above, according to the present embodiment,
An EPC output pressure Pe required for rotating the cooling fan 15 at the target fan rotation speed NF is obtained by calculation, and the EPC output pressure Pe is output to the oil chamber 5 of the piston 3 of the swash plate drive unit 28. The swash plate 2a of the hydraulic pump 2 can be controlled according to the magnitude of the load. For this reason, the feedback mechanism provided in the conventional hydraulic circuit shown in FIG. 6 can be omitted. Thereby, the structure of the hydraulic circuit is simplified, and the cost can be reduced.

In this embodiment, it is assumed that the controller 30 is mounted on a construction machine and the controller 30 outputs an electric signal i to the electromagnetic proportional control valve 6 via a wired electric signal line. However, the device or function corresponding to the controller 30 may be provided outside the construction machine. For example, a signal i may be transmitted wirelessly from a monitoring station remote from the construction machine and applied to the electromagnetic proportional control valve 6 inside the construction machine.

In this embodiment, it is assumed that the cooling fan is mounted on a construction machine. However, the present invention can also be applied to a case where the cooling fan is mounted on a general automobile. Also, without being limited to transportation equipment,
The present invention can also be applied to a case where a cooling fan is mounted on any other industrial machine.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment.

2 is a diagram showing a cross section of a main part of the hydraulic pump shown in FIG. 1, and FIG. 2A is a diagram showing a state when the capacity of the hydraulic pump reaches a maximum capacity; (b) is a diagram showing a state when the capacity of the hydraulic pump has reached the minimum capacity.

FIG. 3 is a control block diagram showing the contents of processing executed by a controller shown in FIG. 1;

FIG. 4 is a graph showing the contents of a map stored in a controller shown in FIG. 1;

FIG. 5 is a graph showing the contents of a map stored in the controller shown in FIG. 1;

FIG. 6 is a conventional hydraulic circuit diagram.

[Explanation of symbols]

 2 Hydraulic pump 2a Swash plate 3 Piston 6 Electromagnetic proportional control valve 18 Rocker cam 29 Piston 30 Controller

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 3H045 AA04 AA10 AA13 AA24 AA33 BA00 BA28 CA01 CA09 CA29 DA25 EA33 EA36 3H089 AA35 BB27 CC08 DA03 DA13 DB03 DB33 DB46 DB48 EE37 GG02 JJ20

Claims (3)

[Claims] A hydraulic pump (2) driven by an engine (1) and a hydraulic actuator (1) driven by hydraulic oil discharged from the hydraulic pump (2).
4), a cooling fan (15) driven by the hydraulic actuator (14), and the hydraulic pump (2).
Of the hydraulic pump (2) according to the discharge pressure of the hydraulic pump (2).
Swash plate driving means (28) for changing the swash plate (2a, 18) of the hydraulic pump (2) to the minimum capacity side in accordance with a control signal while changing the swash plate to the maximum capacity side; A drive control device for a cooling fan, comprising control means (30, 6) for outputting a control signal to the swash plate drive means (28) so that the rotation speed of (15) becomes the fan target rotation speed. In the above, the load pressure of the hydraulic pump (2) corresponding to the target fan speed is determined, and the capacity of the hydraulic pump (2) is determined based on the target fan speed and the rotational speed of the engine (1). A control signal is obtained based on the obtained load pressure and capacity, and the obtained control signal is output to the swash plate driving means (28). apparatus. 2. A first map for obtaining a load pressure of a hydraulic pump (2) from a fan target rotation speed is stored in advance, and based on a load pressure of the hydraulic pump (2) and a capacity of the hydraulic pump (2). 2. The driving of the cooling fan according to claim 1, wherein a second map for obtaining a control signal is stored in advance, and the control signal is obtained in accordance with the stored contents of the first map and the second map. Control device. 3. The swash plate driving means (28) pushes the swash plate (2a, 18) of the hydraulic pump (2) with a force corresponding to the discharge pressure of the hydraulic pump (2) to swash the swash plate. (2a, 1
8) A first piston (29) for tilting the piston toward the maximum capacity side
And a second piston (3) for pushing the swash plate (2a, 18) of the hydraulic pump (2) with a force corresponding to the control pressure to tilt the swash plate (2a, 18) to the minimum displacement side. The cooling means according to claim 1, wherein the control means (30, 6) includes a control valve (6) for outputting a control pressure to the second piston (3). Drive control device.