JP2000170907A - HST vehicle control mechanism - Google Patents

Abstract

(57) [Problem] To provide a control mechanism of an HST vehicle which prevents erroneous starting of a vehicle when an engine is started. A controller (10) includes a forward / reverse selector switch (13) at a neutral position and a tilt sensor (11).
When the tilt angle of the hydraulic pump 7 detected by the hydraulic pump 7 is substantially zero, a start permission signal is output, and the forward / reverse selector switch 13 is not in the neutral position, or the hydraulic pressure detected by the tilt sensor 11 When the tilt angle of the swash plate of the pump 7 is not substantially zero, the start permission signal is not output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an HST (Hydro Static) which is operated by hydraulic pressure as a continuously variable transmission.
The present invention relates to a control mechanism of a vehicle equipped with a transmission.

[0002]

2. Description of the Related Art A conventional HST mounted on a forklift or a work vehicle includes a swash plate type hydraulic pump driven by an engine and a hydraulic motor for driving wheels. The speed ratio of the hydraulic motor to the pump is changed steplessly, and the forward / backward movement of the vehicle is switched by operating the forward / backward switch.

When the engine is started, it is determined that the forward / reverse selector switch is at a neutral position where the hydraulic motor is not rotated, and the engine is permitted to be started, thereby preventing erroneous starting of the vehicle.

[0004]

However, in such a conventional control mechanism for an HST vehicle, for example, when the engine stops due to an excessive load while the vehicle is running, the engine stops. It takes some time before the hydraulic pump returns to the neutral position where the swash plate tilt angle is zero by the urging force of the return spring. For this reason, if the engine is started before the hydraulic pump returns to the neutral position after the engine stall, the vehicle may start even if the forward / reverse switch is in the neutral position.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to prevent an erroneous start of a vehicle when an engine is started in a control mechanism of an HST vehicle.

[0006]

A first aspect of the present invention provides a swash plate type hydraulic pump driven by an engine, a hydraulic motor driven by hydraulic oil discharged from the hydraulic pump, and a swash plate tilt angle of the hydraulic pump. , A return spring that returns the hydraulic pump to the neutral position, a forward / reverse switch that commands the rotation direction of the hydraulic motor, and a neutral that determines that the forward / backward switch is in the neutral position that does not rotate the hydraulic motor. Position determining means, a tilt sensor for detecting a swash plate tilt angle of the hydraulic pump, and a neutral position determining means for determining that the hydraulic pump is at a neutral position according to the swash plate tilt angle detected by the tilt sensor. The engine is started when it is determined that the forward / reverse switch is in the neutral position and the hydraulic pump is in the neutral position. It was assumed and a start permission means for permitting.

[0007]

In the first invention, when the ignition switch is turned to the starter position before the hydraulic pump returns to the neutral position by the urging force of the return spring at the time of engine stall, the forward / reverse selector switch is turned to the neutral position. However, since the engine is not started until it is determined that the hydraulic pump has returned to the neutral position, it is possible to prevent the vehicle or the like from starting erroneously.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, an HST 1 provided as a continuously variable transmission mounted on a forklift includes a variable displacement hydraulic pump 7 driven to rotate by an input shaft 21,
The hydraulic motor 2 includes a hydraulic motor 2 that rotationally drives the output shaft 22 and hydraulic passages 3 and 4 that connect the two. The hydraulic oil discharged from the hydraulic pump 7 is sent to the hydraulic motor 2 so that the hydraulic motor 2
Rotates. The input shaft 21 is rotationally driven by the engine 5 via a gear mechanism 25, and the rotation of the output shaft 22 is transmitted to the left and right wheels 23 via the differential gear 8.

The swash plate type hydraulic pump 7 makes the discharge amount and discharge direction variable in accordance with the swash plate tilt angle, and the discharge amount becomes zero at a neutral position where the swash plate tilt angle becomes zero. Hydraulic pump 7
Is adjusted via a servo actuator (not shown). The servo actuator has a built-in return spring and is held at a neutral position where the swash plate tilt angle becomes zero by the biasing force of each return spring.

An inclination sensor 11 for detecting the inclination angle of the swash plate is provided, and the voltage of the output signal of the inclination sensor 11 becomes zero when the hydraulic pump 7 is in the neutral position, and as the inclination angle of the swash plate increases, It is growing.

The controller 10 calculates the target swash plate tilt angle in accordance with the depression amount of the speed pedal detected by the accelerator opening sensor 12, and calculates the target swash plate tilt angle detected by the tilt sensor 11 as the target swash plate tilt angle. The speed of the vehicle is controlled by adjusting the operation amount of the servo actuator so as to approach the plate tilt angle.

A forward / reverse changeover switch 13 for commanding the rotation direction of the hydraulic motor 2 is provided. Forward / reverse selector switch 1
Reference numeral 3 denotes a neutral position where the hydraulic motor 2 is not rotated, a forward position where the hydraulic motor 2 is rotated in the forward direction of the vehicle, and a reverse position where the hydraulic motor 2 is rotated in the backward direction of the vehicle. .

The controller 10 changes the operating direction of the servo actuator in accordance with a signal from the forward / reverse switch 13 to switch between forward and reverse of the vehicle. When the forward / reverse switch 13 is switched to the neutral position,
The hydraulic pump 7 is held at the neutral position to prevent the vehicle from starting.

As shown in FIG. 2, the drive circuit of the starter motor 31 for starting the engine 5 includes a starter relay 32 for interrupting the drive current for the starter motor 31 and a start permission for interrupting the drive current for the coil of the starter relay 32. Relay 33 and start permission relay 3
And an ignition switch 34 for interrupting the drive current for the third coil. When the engine 5 is started, when the ignition switch 34 is switched to the starter position by the driver, the start permission relay 33 is turned on.
Becomes Then, the controller 10 outputs a start permission signal to turn on the starter relay 32,
The starter motor 31 rotates to start the engine 5.

By the way, for example, if the engine becomes stuck due to an excessive load while the vehicle is running, it takes some time until the hydraulic pump 7 returns to the neutral position by the urging force of the return spring after the engine stall. Therefore, if the engine 5 is started before the hydraulic pump 7 returns to the neutral position after the engine stall, the vehicle may start even if the forward / reverse switch 13 is in the neutral position.

According to the present invention, in order to prevent the vehicle from erroneously starting when the engine 5 starts, the controller 10 controls the swash plate of the hydraulic pump 7 when the forward / reverse selector switch 13 is in the neutral position and the inclination sensor 11 detects the swash plate. When the tilt angle is substantially zero, a start permission signal is output while the forward / reverse selector switch 13 is not in the neutral position or the hydraulic pump 7 detected by the tilt sensor 11
When the tilt angle of the swash plate is not substantially zero, the start permission signal is not output.

The control operation executed by the controller 10 will be described in detail with reference to the flowchart of FIG.

First, in step S1, a signal from the forward / reverse selector switch 13 is read, and in step S2, it is determined whether the forward / reverse selector switch 13 is at the neutral position. The processing performed in step S3 corresponds to the neutral position determination means of the present invention.

If it is determined that the forward / reverse selector switch 13 is in the neutral position, the process proceeds to step S3, where a signal from the inclination sensor 11 is read, and in step S5, it is determined whether the hydraulic pump 7 is in the neutral position. . The processing performed in step S5 corresponds to the neutral position determining means.

In step S2, the forward / reverse selector switch 13
Is determined not to be in the neutral position, or when it is determined in step S5 that the hydraulic pump 7 is not in the neutral position, the process proceeds to step S2 and the engine 5 is started without outputting a start permission signal. Absent.

On the other hand, if it is determined in step S2 that the forward / reverse selector switch 13 is in the neutral position and in step S5 it is determined that the hydraulic pump 7 is in the neutral position, the process proceeds to step S6 to turn on the starter relay 32. .
As a result, the starter motor 31 is driven, and the engine 5 is started. The processing performed in step S6 corresponds to the start permitting means.

When the start permission signal is output in this manner, the process proceeds to step S7, and the running of the vehicle is controlled by another routine (not shown). Then, when it is determined in step S8 that the engine 5 is stopped, the present routine ends.

As described above, when the ignition switch 34 is set to the starter position before the hydraulic pump 7 returns to the neutral position by the urging force of the return spring at the time of engine stall, the forward / reverse changeover switch 13 is not in the neutral position. However, the engine 5 is not started until it is determined that the hydraulic pump 7 has returned to the neutral position, so that the vehicle can be prevented from starting erroneously.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram for driving a starter motor.

FIG. 3 is a flowchart showing control contents.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 HST 2 Hydraulic motor 5 Engine 7 Hydraulic pump 10 Controller 11 Tilt sensor 12 Accelerator opening sensor 13 Forward / reverse changeover switch 31 Starter motor 32 Starter relay 33 Start permission relay 34 Ignition switch

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Noboru Shimizu 2-4-1 Hamamatsucho, Minato-ku, Tokyo World Trade Center Building Kayaba Kogyo Co., Ltd. F-term (reference) AF01 3G093 AA08 BA09 BA13 CA02 CB05 DA13 DB12 EA00 EB03 EC01 FA04 3J053 AA01 AB04 AB43 AB44 DA11 DA23 DA30 EA01

Claims (1)

[Claims] A swash plate hydraulic pump driven by an engine; a hydraulic motor driven by hydraulic oil discharged from the hydraulic pump; a servo actuator for changing a swash plate tilt angle of the hydraulic pump; A return spring for returning the pump to a neutral position; a forward / reverse changeover switch for commanding a rotation direction of the hydraulic motor; and a neutral position determining means for determining that the forward / reverse changeover switch is at a neutral position at which the hydraulic motor does not rotate. An inclination sensor that detects a swash plate tilt angle of the hydraulic pump; and a neutral position determination unit that determines that the hydraulic pump is at the neutral position according to a swash plate tilt angle detected by the tilt sensor. It is determined that the forward / reverse selector switch is in the neutral position and the hydraulic pump is in the neutral position. Control mechanism of the HST vehicle, characterized in that it comprises a start permission means, for permitting starting of the engine when the.