JPS628185Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to industrial vehicles such as forklifts and shovel loaders, and more specifically relates to an improvement of a shift lock device that enables switching between forward and backward movement in industrial vehicles equipped with a torque converter only under certain conditions. It is something.

Generally, in industrial vehicles, so-called switchback operation is frequently performed, in which the driving mode is changed by shifting from forward to reverse or from reverse to forward.If this switchback is performed while the vehicle is running at high speed, In other words, in the event of a sudden switchback, not only is the shock to cargo and passengers dangerous, but it also has an adverse effect on the engine and power transmission system. Therefore, in order to eliminate the above-mentioned problems, vehicles equipped with a torque converter are equipped with a shift lock device that allows switching between forward and forward travel only under certain conditions. Examples include a vehicle speed sensing type that allows switching only when the vehicle is running at a very slow speed, or an engine speed sensing type that allows switching when the engine speed is in a low speed range and braking is applied.・Brake oil pressure sensing types are known.

However, in the former case, if the wheels are locked and slip occurs when sudden braking is applied while the vehicle is running at high speed, the apparent vehicle speed becomes zero, even though the vehicle speed is actually high. It is possible to switch between forward and reverse regardless of the situation, and it is also possible to switch from neutral to forward or reverse with the engine running at high speed when starting, and therefore in any of the above cases. The high load has an adverse effect on the engine, torque converter, and other power transmission systems, impairing their durability.

On the other hand, in the latter case, although the above-mentioned problem with the vehicle speed sensing type of the former can be solved, the brake pedal must be operated in any case when switching between forward and backward travel, and it may cause unnecessary stress to the occupants. This will cause physical and mental fatigue.

The present invention was developed in view of the above-mentioned conventional problems, and enables switching between forward and backward movement when the engine speed is low and the vehicle speed is slow, thereby preventing sudden switchback operation. The object of the present invention is to provide a shift lock device for an industrial vehicle that can protect the engine and power transmission device.

Embodiments of the present invention will be described in detail below with reference to the drawings. As shown in Fig. 1, a shift lever 1 for switching between forward and backward travel is installed near a steering column 2 of a steering device, and a torque converter is connected from the shift lever 1 via a shift lever shaft 3 and an interlocking rod 4. A forward/reverse switching lever of an automatic transmission (not shown) is operated to switch. A fan-shaped lock cam 5 having one lock groove 5a that defines a neutral position is provided in a part of the shift lever shaft 3. On the other hand, a lock arm 6 that can be engaged and detached from this lock groove 5a is attached to a front protector. The lock arm 6 is attached to a support shaft 8 rotatably supported by a bracket 7 fixed to the lock arm 6, and the lock arm 6 is always urged by a lock spring 9 in a direction to engage the lock groove 5a. The lock cam 5 is set so that an outer circumferential surface 5b sandwiching the lock groove 5a faces the lock arm 6 when the shift lever 1 is switched to the forward or reverse position. Further, an actuator 12 of a solenoid 11 for engaging/disengaging operation fixed to the front protector is connected to a movement lever 10 fixed to one end of the support shaft 8 via a link 13, and the solenoid 11 is excited. That is, when the lock is turned on, the lock arm 6 is rotated against the lock spring 9 and removed from the lock groove 5a of the lock cam 5.

As shown in FIG. 3, the solenoid 11 is connected to the output of an arithmetic circuit 15 including an F-V converter and a voltage comparator that receives the output of a rotation sensor that generates an alternating voltage according to the engine speed. , a signal from an arithmetic circuit 17 including an F-V converter and a voltage comparator that receives the output of a vehicle speed sensor 16 that generates an alternating voltage according to the running speed of the vehicle is applied through an AND gate 18. ON and OFF are controlled, and in this example, the engine speed is in a low speed range (for example, 800 rpm or less).
and the vehicle speed is in the slow range (for example, 1.75 km/n or less), the solenoid 11 is turned on,
Under other conditions, the solenoid 11 is set to be turned off. Further, the rotation sensor 14 and the vehicle speed sensor 16 are of an electromagnetic type that generates an alternating voltage due to changes in magnetic flux density, and the rotation sensor 14 is a fuel pump, oil pump, oil ternator, etc. that is rotationally driven by the engine. On the other hand, a vehicle speed sensor 16 is attached to detect the rotation of the ring gear in the differential device.

This embodiment is configured as described above,
The effect will be explained below. shift lever 1
During driving when the motor is switched to the forward side F or the reverse side R, each calculation circuit 15, 17 issues an OFF signal and the solenoid 11 is OFF, so the lock spring 9 engages the solenoid 11. The lock arm 6, which is biased in the direction
b (see Fig. 2 b, c), and therefore, in such a state, it is possible to switch from the forward position F or the reverse position R to the neutral position N, but it is possible to switch from the forward position F to the reverse position Switching to R or vice versa becomes impossible because the lock arm 6 engages with the lock groove 5a of the lock cam 5 at the neutral position N and is locked.

When the engine speed decreases and reaches the above-mentioned low speed range, and when the vehicle speed decelerates and reaches the above-mentioned slow speed range, each arithmetic circuit 15, 1
7 issues an ON signal, and along with this, solenoid 11 turns on.
When the lock is turned ON, the lock arm 6 is rotated in the direction of separating from the lock groove 5a against the lock spring 9 to release the lock (see Fig. 2 d).
Under such conditions, it becomes possible to perform a switching operation not only from the neutral position N but also from the forward position F to the reverse position R or vice versa.

Therefore, according to the present shift lock device, even if the wheels lock due to sudden braking and the apparent vehicle speed becomes zero, the engine speed will not remain in a low rotation state. As long as the vehicle maintains a speed substantially above the slow speed range, switching between forward and reverse is locked, which prevents sudden switchback operation and prevents the engine speed from reaching the high speed range. In certain conditions, forward/reverse switching is locked, so that so-called sudden starts are prevented. Moreover, unlike conventional brake oil pressure sensing type shift lock devices, switching between forward and backward movement when starting from a stopped state does not require the act of stepping on the brake pedal, which is effective in reducing occupant fatigue.

In this embodiment, the shift lock is performed only in the neutral position, that is, one lock groove 5a for the neutral position is formed in the lock cam 5, but this does not interfere with the original purpose and function of the shift lock. In fact, it is advantageous over the conventional structure having a locking groove for each switching position in that it reduces processing costs and facilitates adjustment work during assembly.

As detailed above, the shift lock device of the present invention enables switching between forward and forward movement only when two conditions are met: the engine speed is in the low speed range and the vehicle speed is in the slow speed range. Therefore, when the vehicle has a speed exceeding the slow speed range or when the engine speed is higher than the low speed range, the forward/reverse switching is locked to prevent sudden switchback operation or sudden start. This can protect the engine and the power transmission mechanism from adverse effects caused by excessive loads, and also helps reduce fatigue caused by the passenger's forward/reverse switching operations.

Note that the rotation sensor and vehicle speed sensor of the present invention are not limited to electromagnetic types, and can be replaced with various sensors such as photoelectric types or power generation types.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a perspective view showing a forward/reverse shift lock device, FIG. 2 is an explanatory diagram showing a forward/reverse switching mode, and FIG. 3 shows a control operation of a shift lock solenoid. It is an explanatory diagram. 1...Shift lever, 3...Shift lever shaft, 5...Lock cam, 6...Lock arm,
9...Lock spring, 11...Solenoid,
14... Rotation sensor, 16... Vehicle speed sensor,
15, 17... Arithmetic circuit.

Claims (1)

[Scope of utility model registration request] In a shift lock device that includes a lock arm that can be engaged and disengaged from a lock cam provided in a shift operation system for forward/reverse switching, and a solenoid for engagement and disengagement that is connected to the lock arm, an alternating voltage is applied according to the engine speed. An arithmetic circuit that receives the output of the rotation sensor as input, and an arithmetic circuit that takes as input the output of the vehicle speed sensor that generates an alternating voltage according to the vehicle speed. A shift lock device for an industrial vehicle, wherein the solenoid is operated to disengage the lock arm from the lock cam when the condition is zero or zero, and the lock arm is engaged with the lock cam when the condition is other than the above.