JPH09301016A - Travel control device for hydraulically operated vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To particularly modify and set the speed characteristic of a hydraulically operated vehicle, and thereby allow the improvement in the fuel consumption performance to be compatible with the improvement in the speed-responsiveness. SOLUTION: A travel control device is provided with an engine controlling means 61 for modifying-controlling the engine speed in response to the amount of operation of an accelerator, in relation to a hydraulically operated vehicle in which a hydraulic motor 3 is supplied with operating fluid from a variable displacement hydraulic pump 2 driven by an engine 1 to drive a wheel 31, and a swash plate controlling means 62 for midifying-controlling the angle of a swash plate of the variable displacement hydraulic pump in response to the engine speed determined by the engine speed characteristic. In a small accelerator operating area, the engine is controlled so that the rate of change of the engine speed relatively becomes smaller, and the rate of change of the angle relatively becomes larger. In a large accelerator-operating area, the engine is controlled so that the rate of change of the engine speed relatively becomes larger, and the angle of the swash plate becomes constant at a maximum value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a travel control device for hydraulically driven vehicles such as construction machinery and industrial vehicles, and more specifically, it relates to a hydrostatic transmission (Hydrosta
tic Transmission: Hereinafter, in a hydraulically driven vehicle that is transmitted to wheels by simply using HST, a travel control device that controls the vehicle speed of the hydraulically driven vehicle according to an accelerator operation amount (x) by a driver.

[0002]

2. Description of the Related Art Conventionally, as a travel control device for a hydraulically driven vehicle of this type, one mounted on an industrial vehicle such as a forklift has been known (for example, Japanese Patent Laid-Open No. 4-3660).
No. 69). In this, while the throttle of the engine is mechanically connected to the accelerator pedal, the flow rate and pressure of the hydraulic oil supplied to the swash plate angle adjusting cylinder of the variable swash plate hydraulic pump driven by the engine are
The controller is configured to be controlled to increase / decrease according to the operation amount of the accelerator pedal. And
The amount of oil discharged from the variable swash plate hydraulic pump is changed to change the vehicle speed by the increase / decrease change of the number of times of the engine and the increase / decrease change control of the swash plate angle.

[0003]

However, since the accelerator pedal and the throttle are mechanically connected to each other in the above-described conventional travel control device for a hydraulically driven vehicle, it is necessary to change the vehicle speed characteristic in response to the operation of the accelerator pedal. This can be done only by changing the swash plate angle. Therefore, the width of the control for changing the swash plate angle must be a narrow range corresponding to the engine speed characteristic with respect to the operation amount of the accelerator pedal, and the hydraulic drive such as fuel consumption performance and vehicle speed response to the accelerator operation is required. There is an inconvenience that various performances of the vehicle cannot be sufficiently improved. In particular, from the start to the low speed range, the engine speed rapidly rises as the accelerator pedal is depressed, so the range of control for changing the swash plate angle becomes particularly narrow, resulting in a fuel consumption increase associated with a sharp increase in engine speed. In addition to deterioration of performance and increase of vibration and noise, narrowing of the change range of the swash plate angle causes deterioration of vehicle speed response.

The present invention has been made in view of such circumstances, and an object of the present invention is to achieve both improvement of fuel consumption performance and improvement of vehicle speed responsiveness of a hydraulically driven vehicle particularly in a low speed range. In addition, it is to reduce the vibration and noise.

[0005]

In order to achieve the above object, the invention according to claim 1 is to provide an engine (1), a hydraulic pump (20) driven by the engine (1),
A hydraulic drive vehicle equipped with a hydraulic motor (3, 3) that receives hydraulic oil from the hydraulic pump (20) and rotationally drives the wheels, and drives the vehicle at the speed of the hydraulic drive vehicle. It is premised on a travel control device that controls according to an accelerator operation amount (x) by a person. In this one,
Rotation of the engine (1) according to the accelerator operation amount detecting means (8) for detecting the accelerator operation amount (x) and the accelerator operation amount (x) detected by the accelerator operation amount detecting means (8). Engine control means (61) is provided for controlling the operation of the engine (1) so that the number (r) becomes a rotation speed based on a predetermined rotation speed characteristic in relation to the accelerator operation amount (x). . in addition,
The discharge oil amount of the hydraulic pump (20) is predetermined in relation to the rotational speed (r) according to the rotational speed (r) of the engine (1) controlled by the engine control means (61). A pump control means (65) for controlling the operation of the hydraulic pump (20) is provided so that the discharge oil amount is based on the discharge characteristic.

In the case of the above configuration, the rotational speed (r) of the engine (1) is controlled to be changed with respect to the accelerator operation amount (x) by the driver based on the rotational speed characteristic, while the hydraulic pump (20) is controlled. The amount of discharged oil is changed and controlled with respect to the rotational speed (r) of the engine (1) whose change is controlled as described above, based on the above-mentioned discharge characteristic. That is, the change control of the vehicle speed of the hydraulically driven vehicle is performed based on the change control of both the rotation speed (r) of the engine (1) and the displacement of the hydraulic pump (20). For this reason, it becomes possible to control the hydraulically driven vehicle more widely than before while maintaining the vehicle speed characteristic of the hydraulically driven vehicle with respect to the accelerator operation. It becomes possible to sufficiently improve various performances such as responsiveness.

According to a second aspect of the present invention, the hydraulic pump (20) according to the first aspect is a variable displacement hydraulic pump (2) provided with a variable swash plate, and a pump control means (65) is provided. Swash plate control for tilting the variable swash plate so that the swash plate angle (θ) becomes a swash plate angle based on a predetermined swash plate angle characteristic in relation to the rotation speed (r) of the engine (1). The means (62) is provided.

In the case of the above configuration, the hydraulic pump (20) and the pump control means (65) in the invention according to claim 1 are specifically specified. That is, the swash plate control means (6
By controlling the tilt of the swash plate angle (θ) of the variable displacement hydraulic pump (2) based on the swash plate angle characteristic, the discharge amount of the variable displacement hydraulic pump (2) is surely set to a predetermined value. It is possible to control the operation so that the discharge oil amount becomes.

According to a third aspect of the present invention, as the engine speed characteristic of the engine control means (61) according to the second aspect, the accelerator operation amount (x) is a predetermined set value (xA
) Is smaller than the small accelerator operating area, the rotational speed change rate (dp / dx) of the rotational speed (r) of the engine (1) with respect to the change of the accelerator operating amount (x) is calculated as a rotational speed change in another accelerator operating area. It is set smaller than the rate (dp / dx). In addition to this, swash plate control means (62)
As the swash plate angle characteristic of the swash plate, the angular change rate (dc / dq) of the swash plate angle (θ) with respect to the change of the rotation speed (r) of the engine (1) in the small accelerator operation region is discharged by the rotation speed characteristic. The configuration is such that the increase is set so as to compensate the increase / decrease characteristic of the oil amount.

In the case of the above configuration, the rotation speed characteristic and the swash plate angle characteristic in the invention of claim 2 are specifically specified, and as a result, the following actions are obtained. That is, in the small accelerator operation region, the change in the rotation speed (r) of the engine (1) is relatively small with respect to the accelerator operation, and the swash plate angle (θ) of the variable displacement hydraulic pump (2) is small. Is changed relatively rapidly. That is, the swash plate angle (θ) of the variable displacement hydraulic pump (2) is relatively rapidly increased or decreased while the rotational speed (r) of the engine (1) is kept relatively low, The discharge oil amount and the discharge oil pressure are increased / decreased. Here, in general, the output torque, the fuel consumption rate and the vibration / noise of the engine (1) become larger at the middle and high rotations than at the low rotation, and the swash plate angle of the variable displacement hydraulic pump (2) ( The change of θ) can be performed with high responsiveness as compared with the change of the rotation speed of the engine (1). Therefore, in the small accelerator operation range, that is, when the hydraulically driven vehicle is traveling at a relatively low speed, the fuel efficiency performance of the hydraulically driven vehicle is improved by operating the engine (1) at a relatively low speed. In addition, vibration and noise can be reduced, and the speed response of the hydraulically driven vehicle can be improved mainly by changing the speed of the swash plate angle (θ) relatively rapidly. Become.

According to a fourth aspect of the present invention, the swash plate angle characteristic of the swash plate control means (62) according to the third aspect is that the accelerator operation amount (x) is a predetermined set value (xA).
In this configuration, the swash plate angle (θ) of the variable displacement hydraulic pump (2) in a larger accelerator operation region that is larger than the above is set to be constant at the maximum value.

In the case of the above construction, in addition to the operation according to the invention described in claim 3, in the large accelerator operation region, the swash plate angle (θ) of the variable displacement hydraulic pump (2) becomes constant at its maximum value. Since it is maintained, the variable displacement hydraulic pump (2) is in a state in which the maximum flow rate can be flown, and the amount of discharged oil is changed by changing the rotation speed (r) of the engine (1). That is, in the large accelerator operation range, that is, when the hydraulically driven vehicle is traveling at a relatively high speed, the vehicle speed control of the hydraulically driven vehicle is performed by the change control of the rotation speed (r) of the engine (1). The vehicle speed response can be moderately moderated to enhance the driver's sense of security.

According to a fifth aspect of the present invention, the target engine speed (p) corresponding to the accelerator operation amount (x) is preset in the engine control means (61) of the second aspect of the invention. A target engine speed calculation unit (63) that calculates according to the characteristics, and an engine speed command calculation unit that calculates an engine speed command (q) corresponding to the target engine speed (p) according to a predetermined acceleration / deceleration characteristic. (64) and are provided. Then, the engine (1) is configured to operate and control so that the engine speed (r) of the engine (1) matches the engine speed command (q).

In the case of the above construction, in addition to the operation according to the invention as set forth in claim 1, the vehicle speed response to the accelerator operation of the hydraulically driven vehicle can be set slowly and independently by changing the setting of the acceleration / deceleration characteristic. . That is, the engine (1) is set with the calculated target engine speed (p) as a target.
Engine speed command (q) for gradually increasing or decreasing the engine speed (r) is calculated according to the acceleration / deceleration characteristic, and the operation of the engine (1) is controlled based on the engine speed command (p). At the same time, the swash plate angle (θ) of the variable displacement hydraulic pump (2) is changed and controlled. Therefore, by rapidly setting the acceleration / deceleration characteristic, the time required for the engine speed (r) of the engine (1) to reach the target engine speed (p) is shortened, and the swash plate is also used. The time required for the angle (θ) to reach the value corresponding to the target engine speed (p) is also shortened, which makes it possible to improve the vehicle speed response to the accelerator operation of the hydraulically driven vehicle. On the contrary, by slowly setting the acceleration / deceleration characteristic, it becomes possible to make the vehicle speed response to the accelerator operation of the hydraulically driven vehicle gentle. Therefore, the vehicle speed responsiveness to the accelerator operation of the hydraulically driven vehicle can be uniquely set to be changed gradually, and thus the vehicle speed control of the hydraulically driven vehicle can be finely performed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example in which a travel control device for a hydraulically driven vehicle according to the present invention is applied to a forklift.
Is a diesel engine (hereinafter simply referred to as engine),
2 is a variable displacement hydraulic pump of variable swash plate type driven by the engine (1) (hereinafter, simply referred to as traveling pump), and 3 and 3 are supplied with hydraulic oil from the traveling pump (2). Is a constant displacement hydraulic motor that rotationally drives a pair of wheels (31, 31), and 4 is a governor that adjusts the rotational speed of the engine (1). Further, 5 is an EDC (Electric Displacement Controller) for changing and adjusting the swash plate angle (θ) of the traveling pump (2), and 6 is the governor (4) based on the accelerator operation amount (x) by the driver. ) And the EDC (5) to control the traveling of the forklift. Further, 7 is driven by the above-mentioned engine (1) to move up and down the cylinder (7) of the fork.
1) and a constant-capacity hydraulic pump that supplies hydraulic oil to the tilt cylinder (72) (hereinafter simply referred to as a work pump),
Reference numeral 8 is an accelerator sensor as an accelerator operation amount detecting means for detecting an accelerator operation amount (x) by a potentiometer or the like and sending an accelerator signal corresponding to the detected value to the control unit (6), and 9 is connected to a brake (not shown). A brake sensor for detecting the operation amount of the brake pedal, 10 is a forward / backward changeover switch for changing the traveling direction of the forklift to forward or reverse, and 11 is for detecting the rotational speed of the engine (1) and responding to the detected rotational speed. A pickup coil (hereinafter simply referred to as PPU) that sends a rotation speed feedback signal to the control unit (6), and 12 is a battery that supplies power to the control unit (6).

The traveling pump (2) houses a plurality of reciprocating pistons in a cylinder block which rotates integrally with the pump shaft, and the reciprocating strokes of these pistons are at a swash plate angle (θ). It is configured to be changed and adjusted accordingly. When the pump shaft is rotationally driven by the engine (1), the pistons are rotated around the pump shaft together with the cylinder block,
The hydraulic oil is discharged by reciprocating the above stroke once per one rotation. Therefore, the amount of oil discharged per unit time of the traveling pump (2) is obtained as the product of the displacement volume substantially proportional to the swash plate angle (θ) and the rotational speed (r) of the engine (1). Also,
Each of the hydraulic motors (3, 3) is connected in parallel to the traveling pump (2) by hydraulic piping to form a closed circuit, and the inclination direction of the swash plate of the traveling pump (2). The forward / reverse switching of the forklift allows the rotation direction to be switched between the forward and reverse directions to switch the forward / backward movement of the forklift. The rotational speed of each hydraulic motor (3) per unit time is substantially proportional to the amount of oil discharged per unit time of the traveling pump (2), and therefore the traveling pump (2).
The vehicle speed of the forklift is changed and controlled by changing and controlling the swash plate angle (θ) and the engine speed (r) of the engine (1).

The governor (4) operates by receiving a governor control signal from the control unit (6) so that the engine speed (r) of the engine (1) matches the engine speed command (q) described later. Is configured to change and adjust. The EDC (5) is provided with a swash plate angle adjusting cylinder for adjusting the swash plate angle (θ) of the traveling pump (2) by receiving hydraulic oil supplied from a charge pump (not shown), and the charge pump. And an electromagnetic proportional control valve for changing and adjusting the flow rate and pressure of the hydraulic oil supplied from the control unit (6) to the swash plate angle adjusting cylinder. When the opening degree of the control valve is changed and controlled, the swash plate angle (θ) is changed and adjusted so as to match a swash plate angle command (c) described later.

The control unit (6) includes an accelerator signal from an accelerator sensor (8) and a PPU (1
The rotation speed feedback signal from 1) and various operation signals from the brake sensor (9), forward / reverse switching lever (10), lift lever (73), tilt lever (74), etc. are input respectively. Has become. Then, the control unit (6) calculates the engine speed command (q) according to the accelerator operation amount (x),
Engine control means (61) for controlling the operation of the governor (4) so that the rotation speed (r) of the engine (1) matches the engine rotation speed command (q); and the engine rotation speed command (q). According to the swash plate angle command (c), and the EDC (5) is controlled so that the swash plate angle command (θ) of the traveling pump (2) matches the swash plate angle command (c). Swash plate control means (6) as pump control means (65)
2) and are provided.

Specifically, the engine control means (6
1) is a target engine rotation speed calculation unit (63) for calculating a target engine rotation speed (p) corresponding to the accelerator operation amount (x) according to a predetermined target rotation speed characteristic,
The engine rotation speed command calculation unit (64) calculates an engine rotation speed command (q) corresponding to the target engine rotation speed (p) according to a predetermined acceleration / deceleration characteristic. The engine control means (61) is configured to calculate a governor control signal based on the engine speed command (q) and a speed feedback signal and output the governor control signal to the governor (4).

As the target revolution speed characteristic, as shown in the target revolution speed characteristic map of FIG. 2, the accelerator operation amount (x) is smaller than a predetermined set value (xA) corresponding to the point A shown in FIG. The rotation speed change rate (dp / dx) of the rotation speed (r) of the engine (1) with respect to the change of the accelerator operation amount (x) in the accelerator operation region is set to be relatively small,
In addition, the rotational speed change rate (dp / dx) in the large accelerator operation area other than the small accelerator operation area is set to be relatively large. As the acceleration / deceleration characteristic, the engine speed command (q) is increased / decreased according to the acceleration characteristic map of FIG. 3 or the deceleration characteristic map of FIG.

The swash plate control means (62) calculates a swash plate angle command (c) corresponding to the engine speed command (q) according to a predetermined swash plate angle characteristic, and the swash plate angle command is calculated. The EDC control signal corresponding to (c) is EDC (5)
Is configured to output to. As the swash plate angle characteristic, as shown in the swash plate angle characteristic map of FIG.
When the rotation speed (r) of the engine (1) is lower than the set value (qB) corresponding to the point B shown in the figure, that is, in the low engine rotation area corresponding to the small accelerator operation area, the engine (1 The angle change rate (dc / dq) of the swash plate angle (θ) with respect to the change of the rotation speed (r) is set to be relatively large so as to compensate the increase / decrease characteristic of the discharge oil amount due to the above rotation speed characteristic. Also, the swash plate angle (θ) is set to be constant at the maximum value in the high engine rotation region other than the low engine rotation region. Further, as the swash plate angle characteristic, the engine speed (r) of the engine (1)
Is in the region lower than the set value (qC) corresponding to the point C shown in FIG. 5, the angle change rate (dc / dq) is the rotational speed (r) of the engine (1) and the set value (qc). To the set value (qB) to the angle change rate (d
It is set smaller than (c / dq).

The control unit (6) is
By switching the inclination direction of the swash plate of the traveling pump (2) according to the forward / reverse switching operation of the forward / reverse switching lever (10), the traveling direction of the forklift can be switched to the forward / backward direction. In addition, the output of the engine (1) is controlled by changing the rotational speed (r) of the engine (1) according to the operation amount of the lift lever (73) or the tilt lever (74). It is designed to increase or decrease according to the load.

Specific control in the engine control means (61) and the swash plate control means (62) will be described below with reference to the flow chart shown in FIG.

First, in step S1, the accelerator operation amount (x) is read from the accelerator signal, and this value is compared with the set value (xA) to determine whether it is the small accelerator operation region or the large accelerator operation region. If the accelerator operation amount (x) is smaller than the set value (xA), the process proceeds to step S2, and if it is equal to or larger than the set value (xA), the process proceeds to step S3. In step S2, the target engine speed (p) corresponding to the accelerator operation amount (x) is calculated within the range of "x <xA" in the target speed characteristic map. In step S3, the target engine speed (p) corresponding to the accelerator operation amount (x) is calculated within the range of "x≥xA" in the target speed characteristic map. In step S4, the target engine speed (p)
Is the driver trying to accelerate the forklift based on the previous engine speed command (q0)?
It is determined whether the vehicle is going to decelerate or run at a constant speed. If the target engine speed (p) is smaller than the previous engine speed command (q0), the operation proceeds to step S5. If the target engine speed (p) is equal to the previous engine speed command (q0), the operation proceeds to step S6. If the target engine speed (p) is larger than the previous engine speed command (q0), step S7.
To, respectively.

In step S5, the amount of reduction read from the deceleration characteristic map of FIG. 4 is subtracted from the previous engine speed command (q0), and this is calculated as the current engine speed command (q) to calculate in step S8. Go to. Step S
In 6, the target engine speed (p) is determined as a new engine speed command (q), and the process proceeds to step S8. Further, in step S7, the increment / decrement read from the acceleration characteristic map of FIG. 3 is set to the previous engine speed command (q
0) and add this to the new engine speed command (q)
And proceeds to step S8. Then, in step S8, the value determined in any of steps S5 to S7 is updated and stored as the engine speed command (q) for this time. In step S9, the swash plate angle command (c) is calculated from the engine speed command (q) of this time according to the swash plate angle characteristic map, and step S1
At 0, the EDC control signal corresponding to the swash plate angle command (c) is output to the EDC (5). By this EDC control signal, the EDC (5) increases / decreases and adjusts the swash plate angle (θ) of the traveling pump (2) so as to match the swash plate angle command (c).

In step S11, the rotational speed (r) of the engine (1) is read from the rotational speed feedback signal so that the rotational speed (r) of the engine (1) becomes the value of the engine rotational speed command (q). A governor control signal for adjusting and operating the governor (4) is calculated. Then, step S12
After outputting the governor control signal at, the process returns. In response to the governor control signal, the governor (4) changes and adjusts the rotation speed of the engine (1) so as to match the engine rotation speed command (q).

In this flowchart, steps S1 to S3 are the target engine speed calculating section (63).
Steps S4 to S8 constitute an engine rotation speed command calculation unit (64), and the steps S1 to S8 and steps S11, S
12 constitutes an engine control means (61). Further, step S9 and step S10 constitute swash plate control means (62).

Next, the operation and effect of the travel control system for a hydraulically driven vehicle according to the above embodiment applied to a forklift will be described.

In this embodiment having the above structure, the engine control means (61) and the swash plate control means (62)
The rotational speed (r) of the engine (1) and the swash plate angle (θ) of the traveling pump (2) are controlled respectively. For this reason, the traveling characteristics of the hydraulically driven vehicle can be finely changed and set according to the usage conditions, etc., whereby various performances such as fuel consumption performance and vehicle speed response of the hydraulically driven vehicle can be improved. .

That is, since the rotation speed change rate (dp / dx) in the small accelerator operation region is set to be relatively small, the rotation speed (r) of the engine (1) can be suppressed to be relatively low. At this time, the engine (1) is operating in the low engine speed range, and the angle change rate (dc / dq) in the low engine speed range is set to be relatively large. Is relatively low, the swash plate angle (θ) of the traveling pump (2) changes relatively rapidly. Therefore, when the accelerator operation amount (x) by the driver is in the small accelerator operation region, that is, when the forklift is traveling at a relatively low speed, the engine (1) is operated at low speed while the main operation is performed. It is possible to control the vehicle speed of the forklift by relatively rapidly changing the swash plate angle (θ), which improves fuel efficiency and reduces noise and vibration. The vehicle speed response can be improved.

When the engine (1) is operated in the high engine speed range, that is, when the forklift is traveling at a relatively high speed, the swash plate angle (θ) of the traveling pump (2) has the maximum value. Since it is maintained constant, the traveling control of the forklift truck is performed only by changing the rotation speed (r) of the engine (1), which makes the vehicle speed response of the forklift vehicle gentle and increases the driver's peace of mind. Can be increased.

Further, the rotational speed (r) of the engine (1) is changed to the target engine rotational speed (p) by shifting the increment / decrement value in the acceleration characteristic map and the reduced value in the deceleration characteristic map to the larger value side. It is possible to shorten the time required to reach the value and the time required for the swash plate angle (θ) of the variable displacement hydraulic pump (2) to reach the value corresponding to the target engine speed (p). It is possible to independently enhance the vehicle speed response of the forklift to the accelerator operation. On the contrary, by shifting the values of the increment and decrement and the decrement to the smaller value side, the vehicle speed response of the forklift to the accelerator operation can be made gentler.

In addition, each of the above characteristics can be changed and set by changing and setting the set value (xA) and the set value (qB) according to the working situation of the forklift. By combining various settings, the vehicle speed characteristic of the forklift can be finely changed and set. For example, when the traveling load of the forklift is small, the state in which the engine (1) is operated at low speed can be maintained for a relatively long time by shifting the value of the set value (xA) to a larger value, and By shifting the set value (qB) to the smaller value side, the swash plate angle (θ) can be largely changed while the engine (1) rotation speed is low. As a result, the fuel efficiency performance and vehicle speed responsiveness of the forklift can be further improved. On the contrary, when the traveling load of the forklift is large, the engine speed (p) corresponding to the above set value (xA)
By changing the value of (A) to a higher value, that is, the rotational speed change rate (dp /
dx) is set to a larger value in a range smaller than the rotational speed change rate in other regions, so that the engine (1)
The rotation speed of the engine (1) can be increased relatively quickly, and the set value (qB) can be shifted to a larger value to change the swash plate angle (θ) to the rotation speed (r) of the engine (1). It can change with changes. As a result, the drive torque of the forklift can be increased and the response characteristics can be made gentler.

Further, for example, in order to further improve the safety at the time of driving by a novice driver, the value of the swash plate angle command (cC) corresponding to the point C is shifted to a smaller value side. The angle change rate (dc / dq) in a region where the engine (1) rotational speed is particularly low is set to be particularly small. As a result, the vehicle speed response of the forklift can be made particularly gentle when traveling at a low speed.

<Other Embodiments> The present invention is not limited to the above-described embodiments, but includes various other embodiments. That is, in the above embodiment,
A diesel engine (1) is used as an engine, and a governor (4) is used to adjust the rotation speed (r), but the invention is not limited to this, and a gasoline engine is used and the rotation thereof is adjusted by a throttle or the like. Is also possible.

In the above embodiment, the EDC (5) is used to adjust the swash plate angle (θ) of the variable displacement hydraulic pump (2).
However, the present invention is not limited to this, and it is possible to use a simple actuator.

In the above-described embodiment, as the rotation speed characteristic, as shown in the rotation speed characteristic map of FIG. 2, the characteristics up to point A in FIG. Not limited to this, each may have a non-linear characteristic. Similarly, in the swash plate angle characteristic map of FIG. 5, points C, C to B, and points B and above may be changed non-linearly. Further, the acceleration / deceleration characteristics shown in the acceleration characteristic map of FIG. 3 and the deceleration characteristic map of FIG. 4 may be non-linear characteristics.

[0038]

As described above, according to the traveling control device for a hydraulically driven vehicle in the first aspect of the present invention, the rotational speed (r) of the engine (1) and the displacement of the hydraulic pump (20) are set. Since both of them are controlled, the traveling control of the hydraulically driven vehicle can be performed more finely compared to the conventional one, and thereby various performances such as fuel consumption performance and vehicle speed response of the hydraulically driven vehicle can be sufficiently improved. Can be made.

According to the second aspect of the invention, the variable displacement hydraulic pump (2) is controlled by tilting the swash plate angle (θ) of the variable displacement hydraulic pump (2) by the swash plate control means (62). Can be controlled to be changed so that the amount of discharged oil can surely become a predetermined amount of discharged oil, whereby the effect according to the invention of claim 1 can be obtained reliably.

According to the invention described in claim 3, in addition to the effect of the invention described in claim 2, in the small accelerator operation region, the rotational speed (r) of the engine (1) is kept relatively low and the variable displacement is maintained. -Shaped hydraulic pump (2) swash plate angle (θ)
By increasing / decreasing the value relatively quickly, it is possible to improve the fuel efficiency and reduce vibration and noise when the hydraulically driven vehicle travels at a low speed, and at the same time, to improve the vehicle speed response.

According to the invention of claim 4, in addition to the effect of the invention of claim 3, in the large accelerator operation region, the swash plate angle (θ) of the variable displacement hydraulic pump (2) is maximized. By controlling the rotation speed (r) of the engine (1) while keeping the value constant, the vehicle speed response of the hydraulically driven vehicle can be moderately moderated to enhance the driver's sense of security. .

According to the invention of claim 5, in addition to the effect of the invention of claim 2, the acceleration / deceleration characteristic is changed to uniquely set the vehicle speed response of the hydraulically driven vehicle to the accelerator operation by the driver. It is possible to make a gradual change setting so that the traveling control of the hydraulically driven vehicle can be finely performed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a target rotation speed characteristic map.

FIG. 3 is a diagram showing an acceleration characteristic map.

FIG. 4 is a diagram showing a deceleration characteristic map.

FIG. 5 is a diagram showing a swash plate angle characteristic map.

FIG. 6 is a flowchart showing traveling control of a forklift.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Diesel engine (engine) 2 Variable displacement hydraulic pump 3 Hydraulic motor 8 Accelerator sensor (accelerator operation amount detection means) 20 Hydraulic pump 61 Engine control means 62 Swash plate control means 63 Target engine speed calculation section 64 Engine speed command calculation Part 65 pump control means x accelerator operation amount xA set value qB set value p target engine speed q engine speed command

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Claims (5)

[Claims] An engine (1) and the engine (1)
And a hydraulic pump (20) driven by the hydraulic pump (20) and a hydraulic motor (3, 3) that rotates the wheels by receiving hydraulic oil from the hydraulic pump (20). In a travel control device that controls the vehicle speed of the hydraulically driven vehicle according to the accelerator operation amount (x) by the driver, an accelerator operation amount detection means (8) for detecting the accelerator operation amount (x), and According to the accelerator operation amount (x) detected by the accelerator operation amount detecting means (8), the rotation speed (r) of the engine (1) is a predetermined rotation in relation to the accelerator operation amount (x). Engine control means (61) for controlling the operation of the engine (1) so that the rotation speed is based on a number characteristic, and rotation of the engine (1) controlled by the engine control means (61). Depending on (r), the hydraulic pump (20) discharges a quantity of oil that is based on a discharge characteristic that is predetermined in relation to the rotational speed (r). A travel control device for a hydraulically driven vehicle, comprising: a pump control means (65) for controlling the operation. 2. The hydraulic pump (20) according to claim 1, wherein the hydraulic pump (20) is a variable displacement hydraulic pump (2) provided with a variable swash plate, and the pump control means (65) includes the variable swash plate with a swash plate angle. (Θ) is a swash plate control means (62) for performing tilt control so that the swash plate angle is based on a swash plate angle characteristic that is predetermined in relation to the rotational speed (r) of the engine (1). Is a travel control device for a hydraulically driven vehicle. 3. The engine control means (61) according to claim 2, wherein the accelerator operation amount (x) is changed with respect to a change in the accelerator operation amount (x) in a small accelerator operation area in which the accelerator operation amount (x) is smaller than a predetermined set value (xA). Rotational speed change rate of engine (1) rotational speed (r) (dp / d
x) has a rotational speed characteristic set to be smaller than the rotational speed change rate (dp / dx) in other accelerator operation areas, while the swash plate control means (62) controls the engine (1) in the small accelerator operation area. ) The angle change rate (dc / dq) of the swash plate angle (θ) with respect to the change in the rotation speed (r) is set to be increased so as to compensate the increase / decrease characteristic of the discharge oil amount due to the above rotation speed characteristic. A travel control device for a hydraulically driven vehicle having characteristics. 4. The swash plate control means (62) according to claim 3, wherein the swash plate angle (θ) is a maximum value in a large accelerator operation region in which the accelerator operation amount (x) is larger than a predetermined set value (xA). 2. A travel control device for a hydraulically driven vehicle, which has a swash plate angle characteristic set to be constant. 5. The target engine rotation speed according to claim 2, wherein the engine control means (61) calculates a target engine rotation speed (p) corresponding to the accelerator operation amount (x) according to a predetermined target rotation speed characteristic. A calculating unit (63) and an engine speed command calculating unit (64) for calculating an engine speed command (q) corresponding to the target engine speed (p) according to a predetermined acceleration / deceleration characteristic.
And a configuration for controlling the operation of the engine (1) so that the engine speed (r) of the engine (1) matches the engine speed command (q). Driving control device for driving vehicle.